TECHNICAL FIELD

The present disclosure relates to hydrodynamic retarder configured to brake a shaft of a vehicle. The present disclosure further relates to a retarder arrangement, a transmission arrangement, a power train, a control arrangement, and a vehicle. Moreover, the present disclosure relates to a method of estimating a braking torque of a retarder, a computer program, and a computer-readable medium.

BACKGROUND

Retarders are devices used on vehicles to augment or replace some of the functions of primary braking arrangements, such as friction-based braking arrangements. One common type of retarder is hydrodynamic retarders. Such retarders utilize the viscous drag forces of a liquid in a work space between a rotor and a stator. The rotor is usually connected to a shaft of the vehicle, such as a shaft of the gearbox of the vehicle, via a retarder transmission. Traditionally, the work space has been emptied of liquid when the retarder is not in use. In general, due to environmental concerns, it is an advantage if vehicle arrangements, such as retarder arrangements, have low parasitic losses when not in use. As a reason thereof, some retarders utilize coupling devices to mechanically disconnect the rotor of the retarder from a driving shaft in order to minimize parasitic losses.

Retarders are capable of providing several advantages. As an example, they are less likely to become over heated in comparison to friction-based braking arrangements, for example when braking a vehicle travelling downhill. Furthermore, when used, retarders lower wear of primary friction-based braking arrangements.

The braking torque of a hydrodynamic retarder is difficult to estimate. During braking, the pressure inside a hydrodynamic retarder can be very high and can vary to a great extent. Moreover, in some portions of the hydrodynamic retarder, and in some braking torque ranges, the pressure can reach levels close to vaporization. However, a good estimation of the retarder braking torque can be vital for achieving control functions such as for example a smooth brake blending with other braking systems, an exact control of the braking torque, and the like. Furthermore, in retarders comprising a coupling device used to mechanically disconnect the rotor from a driving shaft, a proper estimation of the retarder braking torque can be important for providing a confirmation of whether the rotor is connected to a driving shaft or not. In addition, generally, on today’s consumer market, it is an advantage if products, such as vehicle arrangements, comprise different features and functions while the products have conditions and/or characteristics suitable for being manufactured and assembled in a cost- efficient manner.

SUMMARY

It is an object of the present invention to overcome, or at least alleviate, at least some of the above-mentioned problems and drawbacks.

According to a first aspect of the invention, the object is achieved by a hydrodynamic retarder configured to brake a shaft of a vehicle. The retarder comprises a retarder housing with a shovel space and a shovel arrangement arranged in the shovel space. The shovel arrangement comprises a shovel-equipped stator and a shovel-equipped rotor together forming a workspace. The retarder further comprises an inlet channel and an outlet channel arranged to supply and evacuate, respectively, working fluid to and from the workspace. Further, the retarder comprises a working circuit comprising the shovel space, the

workspace, and the outlet channel. The retarder further comprises a pressure sensor arrangement configured to, at least selectively, sense the pressure at a first portion of the working circuit, and at a second portion of the working circuit, wherein the second portion is different from the first portion.

Since the retarder comprises the pressure sensor arrangement configured to, at least selectively, sense the pressure at the first and second portions of the working circuit, a retarder is provided having conditions for an improved estimation of a current braking torque of the retarder. Moreover, conditions are provided for an improved estimation of a current braking torque of the retarder over a wider braking torque range. This because the optimal portion of the working circuit for sensing the pressure varies with the braking torque level. Therefore, by sensing the pressure at the first and second portions of the working circuit, an improved estimation of a current braking torque can be made over a wider braking torque range.

Since conditions are provided for an improved estimation of a current braking torque of the retarder over a wider braking torque range, conditions are also provided for a more precise control of the braking torque of the retarder. Moreover, conditions are provided for a smoother brake blending between the retarder and other braking systems. In addition, conditions are provided for a better estimation of whether the rotor is connected to a driving shaft or not. Accordingly, a retarder is provided overcoming, or at least alleviating, at least some of the above-mentioned problems and drawbacks. As a result, the above-mentioned object is achieved.

Optionally, the first portion of the working circuit is a portion of the outlet channel. Thereby, conditions are provided for an improved estimation of the braking torque at low braking torque levels. This because the pressure at the outlet channel is optimal as a base for an estimation of the braking torque at low braking torque levels. Moreover, since conditions are provided for an improved estimation of the braking torque at low braking torque levels, a reliable confirmation can be obtained of whether the rotor is connected to a driving shaft or not.

Optionally, the second portion of the working circuit is a portion of the shovel space. Thereby, conditions are provided for an improved estimation of the braking torque at high braking torque levels. This because the pressure in the shovel space is indicative of the braking torque at higher braking torque levels. Conversely, at lower braking torque levels, the pressure in the shovel space can reach levels close to vaporization. Since conditions are provided for an improved estimation of the braking torque at higher braking torque levels, a more precise control of the braking torque of the retarder can be made. Moreover, a smoother brake blending between the retarder and other braking systems can be made.

Optionally, the pressure sensor arrangement comprises a first pressure sensor fluidly connected to the first portion of the working circuit, and a second pressure sensor fluidly connected to the second portion of the working circuit. Thereby, a simple and reliable retarder is provided having conditions for an improved estimation of a current braking torque of the retarder over a wider braking torque range.

Optionally, the pressure sensor arrangement comprises one pressor sensor only. Thereby, a simple and cost-efficient retarder is provided having conditions for an improved estimation of a current braking torque of the retarder over a wider braking torque range.

Optionally, the retarder comprises a valve fluidly connected to the first and second portions of the working circuit and to the pressure sensor, and wherein the valve comprises a first state in which the valve opens a fluid connection between the pressure sensor and the first portion and closes a fluid connection between the pressure sensor and the second portion, and a second state in which the valve opens the fluid connection between the pressure sensor and the second portion and closes the fluid connection between the pressure sensor and the first portion. Thereby, the pressure sensor can be brought into fluid communication with the first portion or the second portion of the working circuit simply by switching the valve between the first and second states. In this manner, the pressure can be sensed at the first portion or the second portion of the working circuit in dependence of the braking torque level, to provide an improved estimation of a current braking torque of the retarder over a wider braking torque range.

Optionally, the valve is arranged to switch between the first and second states based on a pressure level supplied from a pressure source. Thereby, a simple and efficient control of the state of the valve can be performed.

Optionally, the pressure source is one of the first and second portions of the working circuit. Thereby, the valve can be switched between the first and second states in dependence of the pressure at one of the first and second portions of the working circuit. In this manner, an automatic control of the state of the valve can be performed based on a braking torque level of the retarder. As a result, the need for additional control systems for controlling the valve between the first and second states is circumvented.

Optionally, the pressure source is the second portion of the working circuit, and wherein the valve is configured to switch from the first state to the second state when the pressure at the second portion reaches above a predetermined pressure level. The fact that the pressure at the second portion reaches above the predetermined pressure level indicates that the braking torque rises. Since the valve is configured to switch from the first state to the second state when the pressure at the second portion reaches above the predetermined pressure level, the valve will fluidly connect the pressure sensor to the second portion of the working circuit in an automatic manner when the braking torque rises. Thereby, an automatic control of the state valve is performed in dependence of the braking torque, and an improved estimation of the braking torque at higher braking torque levels can be made.

Optionally, the valve is configured to switch from the second state to the first state when the pressure at the second portion drops below the predetermined pressure level. The fact that the pressure at the second portion drops below the predetermined pressure level indicates that the braking torque decreases. Since the valve is configured to switch from the second state to the first state when the pressure at the second portion drops below the

predetermined pressure level, the valve will fluidly connect the pressure sensor to the first portion of the working circuit in an automatic manner when the braking torque decreases. Thereby, an automatic control of the state valve is performed in dependence of the braking torque, and an improved estimation of the braking torque at lower braking torque levels can be made.

According to a second aspect of the invention, the object is achieved by a retarder arrangement comprising a control arrangement and a retarder according to some

embodiments of the present disclosure. The control arrangement is connected to the pressure sensor arrangement and is configured to estimate a braking torque of the retarder based on sensed pressure at the first portion of the working circuit, in a first braking torque range, and to estimate the braking torque of the retarder based on sensed pressure at the second portion of the working circuit in a second braking torque range. Thereby, a retarder arrangement is provided capable of performing an improved estimation of a current braking torque of the retarder over a wider braking torque range. As a result, a retarder arrangement is provided having conditions for a more precise control of the braking torque of the retarder. Moreover, a retarder arrangement is provided having conditions for obtaining a smoother brake blending between the retarder and other braking systems. In addition, a retarder arrangement is provided having conditions for performing a better estimation of whether the rotor is connected to a driving shaft or not.

According to a third aspect of the invention, the object is achieved by a transmission arrangement configured to transmit power between a power source of a vehicle and wheels of a vehicle. The transmission arrangement comprises a retarder according to some embodiments of the present disclosure. The retarder is configured to brake a shaft of the transmission arrangement. Thereby, a transmission arrangement is provided having conditions for an improved estimation of a current braking torque of the retarder thereof over a wider braking torque range. As a result, a transmission arrangement is provided having conditions for a more precise control of the braking torque of the retarder. Moreover, a transmission arrangement is provided having conditions for obtaining a smoother brake blending between the retarder and other braking systems. In addition, a transmission arrangement is provided having conditions for performing a better estimation of whether the rotor of the retarder is connected to the shaft of the transmission arrangement or not.

According to a fourth aspect of the invention, the object is achieved by a power train for a vehicle, wherein the power train comprises a power source and a transmission arrangement. The transmission arrangement is configured to transmit power between the power source and wheels of the vehicle. The power train comprises a retarder according to some embodiments of the present disclosure. The retarder is configured to brake a shaft of the power train. Thereby, a power train is provided having conditions for an improved estimation of a current braking torque of the retarder thereof over a wider braking torque range. As a result, a power train is provided having conditions for a more precise control of the braking torque of the retarder. Moreover, a power train is provided having conditions for obtaining a smoother brake blending between the retarder and other braking systems. In addition, a power train is provided having conditions for performing a better estimation of whether the rotor of the retarder is connected to the shaft of the power train or not.

According to a fifth aspect of the invention, the object is achieved by a vehicle comprising a power train according to some embodiments of the present disclosure. Thereby, a vehicle is provided having conditions for an improved estimation of a current braking torque of the retarder thereof over a wider braking torque range. As a result, a vehicle is provided having conditions for a more precise control of the braking torque of the retarder. Moreover, a vehicle is provided having conditions for obtaining a smoother brake blending between the retarder and other braking systems of the vehicle. In addition, a vehicle is provided having conditions for performing a better estimation of whether the rotor of the retarder is connected to the shaft of the vehicle or not.

According to a sixth aspect of the invention, the object is achieved by a method of estimating a braking torque of a retarder, wherein the retarder comprises:

a retarder housing with a shovel space,

a shovel arrangement arranged in the shovel space,

wherein the shovel arrangement comprises a shovel-equipped stator and a shovel-equipped rotor together forming a workspace,

an inlet channel and an outlet channel, arranged to supply and evacuate, respectively, working fluid to and from the workspace,

a working circuit comprising the shovel space, the workspace, and the outlet channel,

a pressure sensor arrangement, and

a control arrangement connected to the pressure sensor arrangement, wherein the method comprises:

estimating the braking torque based on sensed pressure at a first portion of the working circuit in a first braking torque range, and

estimating the braking torque based on sensed pressure at a second portion of the working circuit in a second braking torque range, wherein the second portion is different from the first portion. Thereby, a method is provided capable of estimating the current braking torque of the retarder with improved accuracy over a wider braking torque range. Moreover, the method provides conditions for a more precise control of the braking torque of the retarder and conditions for a smoother brake blending between the retarder and other braking systems. In addition, the method provides conditions for a better estimation of whether the rotor is connected to a driving shaft or not.

Accordingly, a method is provided overcoming, or at least alleviating, at least some of the above-mentioned problems and drawbacks. As a result, the above-mentioned object is achieved.

According to a seventh aspect of the invention, the object is achieved by a computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method according to some embodiments of the present disclosure. Since the computer program comprises instructions which, when the program is executed by a computer, cause the computer to carry out the method according to some embodiments, a computer program is provided which provides conditions for overcoming, or at least alleviating, at least some of the above-mentioned drawbacks.

According to an eighth aspect of the invention, the object is achieved by a computer- readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the method according to some embodiments of the present disclosure. Since the computer-readable medium comprises instructions which, when the program is executed by a computer, cause the computer to carry out the method according to some embodiments, a computer-readable medium is provided which provides conditions for overcoming, or at least alleviating, at least some of the above-mentioned drawbacks.

According to a ninth aspect of the invention, the object is achieved by a control arrangement for a retarder, wherein the retarder comprises:

a retarder housing with a shovel space,

a shovel arrangement arranged in the shovel space,

wherein the shovel arrangement comprises a shovel-equipped stator, and a shovel-equipped rotor together forming a workspace,

an inlet channel and an outlet channel, arranged to supply and evacuate, respectively, working fluid to and from the workspace,

a working circuit comprising the shovel space, the workspace, and the outlet channel, and a pressure sensor arrangement,

wherein the control arrangement is configured to:

estimate the braking torque based on sensed pressure at a first portion of the working circuit in a first braking torque range, and

estimate the braking torque based on sensed pressure at a second portion of the working circuit in a second braking torque range, wherein the second portion is different from the first portion.

Thereby, a control arrangement is provided capable of estimating the current braking torque of the retarder with improved accuracy over a wider braking torque range. Moreover, the control arrangement provides conditions for a more precise control of the braking torque of the retarder and conditions for a smoother brake blending between the retarder and other braking systems. In addition, the control arrangement provides conditions for a better estimation of whether the rotor is connected to a driving shaft or not.

Accordingly, a control arrangement is provided overcoming, or at least alleviating, at least some of the above-mentioned problems and drawbacks. As a result, the above-mentioned object is achieved.

Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of the invention, including its particular features and advantages, will be readily understood from the example embodiments discussed in the following detailed description and the accompanying drawings, in which:

Fig. 1 schematically illustrates a cross section of a hydrodynamic retarder, according to some embodiments,

Fig. 2 schematically illustrates a cross section of a hydrodynamic retarder, according to some further embodiments,

Fig. 3 schematically illustrates a power train, according to some embodiments,

Fig. 4 illustrates a vehicle, according to some embodiments,

Fig. 5 illustrates a method of estimating a braking torque of a retarder, according to some embodiments, and

Fig. 6 illustrates computer-readable medium, according to some embodiments. DETAILED DESCRIPTION

Aspects of the present invention will now be described more fully. Like numbers refer to like elements throughout. Well-known functions or constructions will not necessarily be described in detail for brevity and/or clarity.

Fig. 1 schematically illustrates a cross section of a hydrodynamic retarder 1 according to some embodiments. The hydrodynamic retarder 1 is configured to brake a shaft 3 of a vehicle. As is further explained herein, according to the illustrated embodiments, the hydrodynamic retarder 1 is configured to brake a shaft 3 of a gearbox of a vehicle. For the reason of brevity and clarity, the hydrodynamic retarder 1 is in some places herein referred to as the retarder 1. The retarder 1 comprises a retarder housing 7 with a shovel space 9 and a shovel arrangement 1 1 , 13 arranged in the shovel space 9. The shovel arrangement 1 1 , 13 comprises a shovel-equipped stator 1 1 and a shovel-equipped rotor 13 together forming a workspace 15. The workspace 15 can also be referred to as a torus. The retarder 1 further comprises an inlet channel 17 and an outlet channel 19. The inlet channel 17 is arranged to supply working fluid to the workspace 15. The outlet channel 19 is arranged to evacuate working fluid from the workspace 15. The retarder 1 further comprises a working circuit 9, 15, 19 comprising the shovel space 9, the workspace 15, and the outlet channel 19.

The retarder 1 comprises a retarder transmission 20 comprising a set of gear wheels 20’,

20”. Furthermore, the retarder 1 comprises a coupling device 22 and an actuator element 24 mechanically connected to the coupling device 22. The actuator element 24 is moveable between an actuated position and an unactuated position to move the coupling device 22 between an engaged state and a disengaged state. The coupling device 22 is configured to, in the engaged state, connect the rotor 13 to the shaft 3 via the retarder transmission 20, and in the disengaged state, disconnect the rotor 13 from the shaft 3.

According to the illustrated embodiments, the retarder transmission 20 comprises a first gear wheel 20’ and a second gear wheel 20”. The second gear wheel 20” is arranged on a rotor shaft 26 and the first gear wheel 20’ is connectable to the shaft 3 by the coupling device 22. According to the illustrated embodiments, the coupling device 22 is configured to, in the engaged state, connect the first gear wheel 20’ of the retarder transmission 20 to the shaft 3. Moreover, the coupling device 22 is configured to, in the disengaged state, disconnect the first gear wheel 20’ of the retarder transmission 20 from the shaft 3. Thus, according to the illustrated embodiments, the first gear wheel 20’ and a second gear wheel 20” of the retarder transmission 20 will not rotate, or will at least not be driven by the shaft 3, when the coupling device 22 is in the disengaged state. The coupling device 22 may comprise a dog clutch, a synchronizer, or the like.

During operation of the retarder 1 , i.e. during rotation of the rotor 13, the retarder 1 pumps working fluid from the inlet channel 17 to the outlet channel 19, via the workspace 15. The inlet channel 17 and the outlet channel 19 may each comprise a plurality of parallel channels arranged to supply and evacuate, respectively, working fluid to and from the workspace 15. As an example, the outlet channel 19, as referred to herein, may be integrated in the shovel- equipped stator 1 1 and may comprise one outlet channel portion per shovel of the shovel- equipped stator 1 1 . According to such embodiments, the outlet channel portions may each extend to a common ring-shaped volume arranged in the housing 7. The retarder 1 comprises a brake valve 27 arranged to restrict flow of working fluid through the outlet channel 19 so as to control the braking torque of the retarder 1. The wording“outlet channel 19” as used herein, may be defined as an outlet channel 19, or a set of outlet channels 19, extending from the workspace 15 to the brake valve 27. From the brake valve 27, the working medium flows through a retarder circuit 28, comprising a cooler 30, back to the inlet channel 17. The working medium may comprise oil or an aqueous mixture.

The retarder 1 comprises a pressure sensor arrangement 21. According to the embodiments illustrated in Fig. 1 , the pressure sensor arrangement 21 comprises a first pressure sensor 31 fluidly connected to the first portion 23 of the working circuit 9, 15, 19 and a second pressure sensor 32 fluidly connected to the second portion 25 of the working circuit 9, 15, 19. Moreover, according to the illustrated embodiments, the retarder 1 is comprised in a retarder arrangement 40 comprising a control arrangement 43. The control arrangement 43 is connected to the first and second pressure sensors 31 , 32.

According to the illustrated embodiments, the first portion 23 of the working circuit 9, 15, 19 is a portion of the outlet channel 19 upstream of the brake valve 27. Moreover, according to the illustrated embodiments, the second portion 25 of the working circuit 9, 15, 19 is a portion of the shovel space 9 adjacent to the rotor 13. According to further embodiments, the second portion 25 of the working circuit 9, 15, 19 may be a portion of the workspace 15. The pressure at the second portion 25 provides a reliable base for an estimation of the braking torque at higher braking torque levels. Conversely, at lower braking torque levels, the pressure at the second portion 25, i.e. at the shovel space 9, can reach levels close to vaporization and is not optimal as a base for an estimation of the braking torque at lower braking torque levels. According to the illustrated embodiments, the control arrangement 43 is configured to estimate the braking torque based on sensed pressure at the first portion 23 of the working circuit 9, 15, 19 in a first braking torque range, and to estimate the braking torque based on sensed pressure at the second portion 25 of the working circuit 9, 15, 19 in a second braking torque range, wherein the first braking torque range is lower than the second braking torque range. As a result, the control arrangement 43 can estimate the braking torque of the retarder 1 , using values from the first pressure sensor 31 , at low braking torque ranges with high accuracy, and can estimate the braking torque of the retarder 1 , using values from the second pressure sensor 32, at higher braking torque ranges with high accuracy. In this manner, the control arrangement 43 is capable of estimating the current braking torque of the retarder 1 with improved accuracy over a wider braking torque range. Thereby, conditions are provided for a more precise control of the braking torque of the retarder 1 and a smoother brake blending between the retarder 1 and other braking systems of a vehicle comprising the retarder 1. In addition, a better estimation can be made of whether the rotor 13 is connected to the shaft 3 or not.

According to some embodiments, the control arrangement 43 may estimate the braking torque of the retarder 1 , using values from the first pressure sensor 31 when the pressure at the second portion 25 is below a predetermined pressure level, and may estimate the braking torque of the retarder 1 , using values from the second pressure sensor 32 when the pressure at the second portion 25 is above the predetermined pressure level. Purely as an example, the predetermined pressure level may be within the range of 0 - 3 bars, such as within the range of 0.1 - 3 bars.

According to further embodiments, the control arrangement 43 may be configured to utilize input from another arrangement or system as a basis for a determination of whether values from the first or second pressure sensor 31 , 32 is to be used to estimate the braking torque of the retarder 1. As an example, the control arrangement 43 may be configured to estimate the braking torque of the retarder 1 , using values from the first pressure sensor 31 , during idle rotation of the retarder 1. Moreover, the control arrangement 43 may be configured to estimate the braking torque of the retarder 1 , using values from the first pressure sensor 31 , when the actuator element 24 is in the unactuated position, to thereby confirm if the rotor 13 is disconnected from the shaft 3. Furthermore, the control arrangement 43 may be configured to estimate the braking torque of the retarder 1 , using values from the second pressure sensor 32, during braking with the retarder 1. As an example, the control arrangement 43 may be configured to estimate the braking torque of the retarder 1 , using values from the second pressure sensor 32, when the actuator element 24 is in the actuated position.

Fig. 2 schematically illustrates a cross section of a hydrodynamic retarder 1 according to some further embodiments. The retarder 1 illustrated in Fig. 2 comprises the same features, functions, and advantages, as the retarder 1 illustrated in Fig. 1 , with some exceptions explained below. According to the embodiments illustrated in Fig. 2, the pressure sensor arrangement 21 of the retarder 1 comprises one pressor sensor 35 only. The control arrangement 43 is connected to the pressor sensor 35. Moreover, the retarder 1 comprises a valve 37 fluidly connected to the first and second portions 23, 25 of the working circuit 9, 15, 19 and to the pressure sensor 35. The valve 37 comprises a first state in which the valve 37 opens a fluid connection between the pressure sensor 35 and the first portion 23 and closes a fluid connection between the pressure sensor 35 and the second portion 25. Furthermore, the valve 37 comprises a second state in which the valve 37 opens the fluid connection between the pressure sensor 35 and the second portion 25 and closes the fluid connection between the pressure sensor 35 and the first portion 23.

According to the illustrated embodiments, the valve 37 is arranged to switch between the first and second states based on a pressure level supplied from a pressure source 23, 25, 39, which, according to the illustrated embodiments, is the second portion 25 of the working circuit 9, 15, 19. The valve 37 is configured to switch from the first state to the second state when the pressure at the second portion 25 reaches above a predetermined pressure level. Moreover, the valve 37 is configured to switch from the second state to the first state when the pressure at the second portion 25 drops below the predetermined pressure level. Purely as an example, the predetermined pressure level may be within the range of 1 - 3 bars. In this manner, an automatic control of the state of the valve 37 is obtained. All pressures and pressure levels given herein are pressures above atmospheric pressure, also referred to as gauge pressures.

Thus, according to the illustrated embodiments, the pressure sensor 35 is fluidly connected to the first portion 23 when the pressure at the second portion 25 is below the predetermined pressure level. As a result, the control arrangement 43 can estimate the braking torque of the retarder 1 , using sensed pressure at the first portion 23, at low braking torque ranges with high accuracy. In addition, a better estimation can be made of whether the rotor 13 is connected to the shaft 3 or not. At higher braking torque ranges, i.e. when the pressure at the second portion 25 is above the predetermined pressure level, the pressure sensor 35 is fluidly connected to the second portion 25. As a result, the control arrangement 43 can estimate the braking torque of the retarder 1 , using sensed pressure at the second portion 25, at higher braking torque ranges with high accuracy. Thereby, conditions are provided for a more precise control of the braking torque of the retarder 1 and a smoother brake blending between the retarder 1 and other braking systems of a vehicle comprising the retarder 1. Moreover, the control arrangement 43 is capable of estimating the current braking torque of the retarder 1 with improved accuracy over a wider braking torque range.

According to further embodiments, the valve 37 may be switched between the first and second states by an electronic control arrangement. Furthermore, according to some embodiments, the valve 37 is arranged to switch between the first and second states based on a pressure level supplied from a pressure source 39 other than the first and second portions 23, 25 of the working circuit 9, 15, 19, such as a control pressure from a vacuum generator, or the like.

Fig. 3 schematically illustrates a power train 60, according to some embodiments, for a vehicle. The power train 60 comprises a power source 53 and a transmission arrangement 50. The transmission arrangement 50 is configured to transmit power between the power source 53 and wheels 55 of the vehicle. The power train 60 comprises a retarder 1 , which may be a retarder 1 according to the embodiments illustrated in Fig. 1 , or a retarder 1 according to the embodiments illustrated in Fig. 2. The retarder 1 is configured to brake a shaft 3 of the power train 60. In more detail, according to the illustrated embodiments, the retarder 1 is configured to brake a shaft 3 of the transmission arrangement 50, namely a shaft 3 of a gearbox 57 of the transmission arrangement 50. During braking, the torque applied to the shaft 3 by the retarder 1 is transferred to the wheels 55 of the vehicle to provide a retardation force to the vehicle.

The power source 53 may comprise an internal combustion engine, for example a compression ignition engine, such as a diesel engine, or an Otto engine with a spark-ignition device, wherein the Otto engine may be configured to run on gas, petrol, alcohol, similar volatile fuels, or combinations thereof. As an alternative, or in addition, the power source 53 may comprise one or more electrical machines.

Fig. 4 illustrates a vehicle 5 according to some embodiments. The vehicle 5 comprises a power train 60 according to the embodiments illustrated in Fig. 3. The power train 60 is arranged to provide motive power to the vehicle 5 via wheels 55 of the vehicle 5. According to the illustrated embodiments, the vehicle 5 is a truck. However, according to further embodiments, the vehicle 5, as referred to herein, may be another type of manned or unmanned vehicle for land based propulsion such as a lorry, a bus, a construction vehicle, a tractor, a car, or the like.

Fig. 5 illustrates a method 100 of estimating a braking torque of a retarder, according to some embodiments. The retarder 1 may be a retarder 1 according to the embodiments illustrated in Fig. 1 , or a retarder 1 according to the embodiments illustrated in Fig. 2.

Therefore, below, reference is made to Fig. 5 as well as to Fig. 1 and Fig. 2. The method 100 is a method 100 of estimating a braking torque of a retarder 1 , wherein the retarder 1 comprises:

a retarder housing 7 with a shovel space 9,

a shovel arrangement 1 1 , 13 arranged in the shovel space 9,

wherein the shovel arrangement 1 1 , 13 comprises a shovel-equipped stator 1 1 , and a shovel-equipped rotor 13, together forming a workspace 15, an inlet channel 17 and an outlet channel 19, arranged to supply and evacuate, respectively, working fluid to and from the workspace 15,

a working circuit 9, 15, 19 comprising the shovel space 9, the workspace 15, and the outlet channel 19,

a pressure sensor arrangement 21 , and

a control arrangement 43 connected to the pressure sensor arrangement 21 , wherein the method 100 comprises:

estimating 1 10 the braking torque based on sensed pressure at a first portion 23 of the working circuit 9, 15, 19 in a first braking torque range, and estimating 120 the braking torque based on sensed pressure at a second portion 25 of the working circuit 9, 15, 19 in a second braking torque range, wherein the second portion 25 is different from the first portion 23.

It will be appreciated that the various embodiments described for the method 100 are all combinable with the control arrangement 43 as described herein. That is, the control arrangement 43 may be configured to perform any one of the method steps 1 10, 120 of the method 100.

Fig. 6 illustrates computer-readable medium 200 comprising instructions which, when executed by a computer, cause the computer to carry out the method 100 according to some embodiments of the present disclosure. According to some embodiments, the computer-readable medium 200 comprises a computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method 100 according to some embodiments.

One skilled in the art will appreciate that the method 100 of estimating a braking torque of a retarder 1 may be implemented by programmed instructions. These programmed instructions are typically constituted by a computer program, which, when it is executed in the control arrangement 43, ensures that the control arrangement 43 carries out the desired control, such as the method steps 1 10 and 120 described herein. The computer program is usually part of a computer program product 200 which comprises a suitable digital storage medium on which the computer program is stored.

The control arrangement 43 may comprise a calculation unit which may take the form of substantially any suitable type of processor circuit or microcomputer, e.g. a circuit for digital signal processing (digital signal processor, DSP), a Central Processing Unit (CPU), a processing unit, a processing circuit, a processor, an Application Specific Integrated Circuit (ASIC), a microprocessor, or other processing logic that may interpret and execute instructions. The herein utilised expression“calculation unit” may represent a processing circuitry comprising a plurality of processing circuits, such as, e.g., any, some or all of the ones mentioned above.

The control arrangement 43 may further comprise a memory unit, wherein the calculation unit may be connected to the memory unit, which may provide the calculation unit with, for example, stored program code and/or stored data which the calculation unit may need to enable it to do calculations. The calculation unit may also be adapted to store partial or final results of calculations in the memory unit. The memory unit may comprise a physical device utilised to store data or programs, i.e., sequences of instructions, on a temporary or permanent basis. According to some embodiments, the memory unit may comprise integrated circuits comprising silicon-based transistors. The memory unit may comprise e.g. a memory card, a flash memory, a USB memory, a hard disc, or another similar volatile or non-volatile storage unit for storing data such as e.g. ROM (Read-Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable PROM), EEPROM (Electrically Erasable PROM), etc. in different embodiments.

The control arrangement 43 is connected to components of the vehicle 5 for receiving and/or sending input and output signals. These input and output signals may comprise waveforms, pulses or other attributes which the input signal receiving devices can detect as information and which can be converted to signals processable by the control arrangement 43. These signals may then be supplied to the calculation unit. One or more output signal sending devices may be arranged to convert calculation results from the calculation unit to output signals for conveying to other parts of the vehicle's control system and/or the component or components for which the signals are intended. Each of the connections to the respective components of the vehicle 5 for receiving and sending input and output signals may take the form of one or more from among a cable, a data bus, e.g. a CAN (controller area network) bus, a MOST (media orientated systems transport) bus or some other bus configuration, or a wireless connection.

In the embodiments illustrated, the retarder arrangement 40 comprises a control

arrangement 43 but might alternatively be implemented wholly or partly in two or more control arrangements or two or more control units.

Control systems in modern vehicles generally comprise a communication bus system consisting of one or more communication buses for connecting a number of electronic control units (ECUs), or controllers, to various components on board the vehicle. Such a control system may comprise a large number of control units and taking care of a specific function may be shared between two or more of them. Vehicles of the type here concerned are therefore often provided with significantly more control arrangements than depicted in Fig. 1 and Fig. 2, as one skilled in the art will surely appreciate.

The computer program product 200 may be provided for instance in the form of a data carrier carrying computer program code for performing at least some of the method steps 1 10 and 120 according to some embodiments when being loaded into one or more calculation units of the control arrangement 43. The data carrier may be, e.g. a CD ROM disc, as is illustrated in Fig. 6, or a ROM (read-only memory), a PROM (programable read-only memory), an

EPROM (erasable PROM), a flash memory, an EEPROM (electrically erasable PROM), a hard disc, a memory stick, an optical storage device, a magnetic storage device or any other appropriate medium such as a disk or tape that may hold machine readable data in a non- transitory manner. The computer program product may furthermore be provided as computer program code on a server and may be downloaded to the control arrangement 43 remotely, e.g., over an Internet or an intranet connection, or via other wired or wireless communication systems.

It is to be understood that the foregoing is illustrative of various example embodiments and that the invention is defined only by the appended claims. A person skilled in the art will realize that the example embodiments may be modified, and that different features of the example embodiments may be combined to create embodiments other than those described herein, without departing from the scope of the present invention, as defined by the appended claims.

As used herein, the term "comprising" or "comprises" is open-ended, and includes one or more stated features, elements, steps, components or functions but does not preclude the presence or addition of one or more other features, elements, steps, components, functions or groups thereof.