The present invention pertains to a clutch device for a retarder according to the preamble of patent claim 1, a vehicle comprising such a clutch device according to the preamble to patent claim 15, and a method for the connection of a retarder according to the preamble to patent claim 16.

A retarder is used to brake a driving source, such as a vehicle. Often the retarder consists of an auxiliary brake, which complements the wheel brakes of the vehicle. Thus excessive wear of the wheel brakes is avoided. The retarder is connected to the vehicle's gearbox or propeller shaft via a transmission. In order to reduce energy losses and thus reduce the vehicle's fuel consumption, the transmission and the retarder are disconnected from the gearbox or the propeller shaft when the retarder is disengaged and does not have to brake the vehicle. The retarder shaft stands still when the retarder is not engaged. The retarder's rotor and stator form a torus, which must be filled with a fluid as quickly as possible when a braking effect from the retarder is desired. A slow filling initially entails a lack of a braking effect from the retarder, which entails an exaggerated use of the vehicle's wheel brakes which will be exposed to unnecessary wear. In order to expedite the filling of the torus, a fluid with low viscosity may be used, such as water. In the event that a clutch device, which is used for the connection and disconnection of the retarder on the gearbox or the propeller shaft, comprises a synchronisation device with synchronisation rings, the connection and disconnection of the transmission on the gearbox or propeller shaft is more difficult when the torus of the retarder is filled with water. The speed difference between the different components that are connected with each other entails a substantial heat development in the synchronisation device, which is thus subject to substantial wear and tear. In the event that the torus is not fully drained before the connection of the retarder, the engaging torque becomes very high, which leads to great stress on the synchronisation device. Thus the retarder's braking effect may be delayed or absent due to a worn-out synchronisation device. In order to counteract this, the synchronisation device may be dimensioned to resist such wear and tear, but this entails a weight increase, which is not desirable.

The document US-A-3777860 shows a retarder for vehicles with a rotor and a stator, at which the rotor is installed to connect and disconnect the vehicle's driving shaft with a clutch device which is controlled automatically depending on the activation of the vehicle brake.

The document DE-A1- 10305239 shows a retarder for vehicles where the drive comprises a form bound clutch device. The form bound clutch device interacts with the vehicle's main clutch.

SUMMARY OF THE INVENTION

Despite prior art solutions, there is a need to further develop a clutch device for a retarder which does not significantly encumber a driving source when it is disengaged, but which has a low weight and which is engaged for a very short period of time when the retarder exerts a braking effect on the driving source.

The objective of the invention is thus to provide a clutch device for a retarder with increased life and reliability.

Another objective of the invention is to provide a clutch device for a retarder which, when disengaged, exerts a substantially zero braking torque on the driving source. Another objective of the invention is to provide a clutch device for a retarder which reduces the fuel consumption of a vehicle.

Another objective of the present invention is to provide a clutch device for a retarder with a short activation period.

Another objective of the invention is to provide a clutch device designed for a retarder, which contributes to a compact design of the retarder. These objectives are achieved with a retarder of the type specified at the beginning, which is characterised by the features specified in the patent claim 1.

Such a clutch device reduces the retarder's activation time considerably when the retarder is connected, at the same time as the clutch device is subject to low wear and tear, which entails an increased service life and reliability of the clutch device. The clutch device entails that the retarder in a disengaged state exerts a substantially zero braking torque on the driving source, which thus reduces the fuel consumption of a vehicle. The clutch elements' interaction with the first and the second shafts entails a compact design of the retarder. The retarder's weight is thus reduced, which entails that the fuel consumption of the vehicle may be reduced.

The above specified objectives are achieved also with a vehicle of the type mentioned above, which is characterised by the features specified in patent claim 15. The retarder permits a brief activation time and, when disengaged, exerts a substantially zero torque on the vehicle in order thus to reduce the fuel consumption. The controlled connection and disconnection of the retarder via the clutch device also entails that its service life and reliability increases. The small dimensions of the retarder, which arise through the clutch elements' interaction with the first and second shafts, entail a compact design of the retarder. The retarder's weight is thus reduced, which entails that the fuel consumption of the vehicle may be reduced.

The above objectives are achieved also with a method for the connection of a retarder of the type specified at the beginning, which is characterised by the features specified in the patent claim 16. Other advantages of the invention are set out in the detailed description below. BRIEF DESCRIPTION OF DRAWINGS

Below is a description, as an example, of preferred embodiments of the invention with refer- ence to the enclosed drawings, in which:

Fig. 1 shows a schematic side view of a vehicle with a clutch device for a retarder

according to the present invention,

Fig. 2 shows a section view of a first embodiment of a clutch device for a

retarder, according to the present invention, in a disconnected state, Fig. 3 shows a section view of the first embodiment of the clutch device for a retarder, according to the present invention, in a connected state,

Fig. 4 shows a section view of a second embodiment of a clutch device for a

retarder, according to the present invention, and

Fig. 5 shows a flow chart of a method for connection of a retarder according to

the present invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION Fig. 1 shows a schematic side view of a vehicle 1, the vehicle 1 of which is equipped with a retarder 2, which is connected and disconnected with a clutch device 4 according to the present invention. The vehicle 1 is also equipped with a gearbox 6, which is connected to a combustion engine 8, which drives the driving wheels 10 of the vehicle 1 via the gearbox 6 and a conventional transmission comprising, among others, a propeller shaft 12. The driving wheels 10 are equipped with wheel brakes 11. A torque sensor 14 is arranged on the combustion engine 8 in order to detect the torque emitted from the combustion engine 8. The torque sensor 14 is connected to a control device 16, which is arranged to control the retarder 2.

Fig. 2 shows a section view of a clutch device 4 for a retarder 2, according to a first embodi- ment of the present invention, in a disconnected state. The clutch device 4 comprises a first shaft 18, which is connected with a rotor 20 of the retarder 2 and a second shaft 22, which is arranged to engage with a driving source. According to the embodiment shown in Fig. 2, the driving source constitutes the vehicle 1, where the connection of the retarder 2 with the vehicle 1 is carried out via the gearbox 6. The second shaft 22 is equipped with teeth 24 for en- gagement with a transmission 26 arranged at the gearbox 6, which comprises a gear drive 28 between the output shaft 30 and the second shaft 22 of the gearbox 6. The gear drive 28 comprises the first and second cogwheels 32, 34 in engagement with each other.

The first cogwheel 32 is arranged on the output shaft 30 of the gearbox 6, and the second cogwheel 34 is arranged between the first cogwheel 32 and the second shaft 22. The first and second cogwheels 32, 34 and the second shaft 22 are in constant engagement with each other. Preferably, a gearing through the gear drive 28 in the ratio 3: 1 occurs, but other gearings are also possible, e.g. 1: 1. The first shaft 18 is preferably journalled, through a bearing 36, in a gearbox house 38 and in a retarder house 40. On the first shaft 18 the rotor 20 is arranged, which in a connected state rotates with a speed which is proportionate to the speed of the output shaft 30 of the gearbox 6. A stator 42 is connected to the retarder housing 40 and will therefore not rotate.

The rotor 20 and the stator 42 jointly form a toroidal void shape, which is called torus 44, which is filled with a fluid 46, such as water, when the retarder 2 carries out a braking torque on the output shaft 30 of the gearbox 6 in order to brake the vehicle 1 to thus reduce the vehicle's 1 speed. The braking effect arises since the rotor 20 and the stator 42 are equipped with blades or shovels 48, which create a fluid flow in the torus 44 when the rotor 20 rotates. The fluid flow creates, in interaction with the shovels 48 of the rotor 20 and the stator 42, a reaction force which forms the braking effect. The greater the revolutions of the rotor 20, the greater the reaction force. On occasions when the retarder 2 does not have to brake the vehicle 1, the torus 44 is drained of fluid 46, which entails that the shovels 48 of the rotor 20 and the stator 42 will create an air flow in the torus 44. The air flow causes an undesirable reaction force on the first shaft 18, which generates a braking torque on the output shaft 30 of the gearbox 6. The braking torque from the retarder 2 entails that the fuel consumption of the vehicle 1 increases when the combustion engine 8 of the vehicle 1 exerts a torque. The friction from the first shaft's 18 bearings emits a reaction force, which entails an increased fuel con- sumption. For this reason, the first shaft 18 may be disconnected from the output shaft 30 of the gearbox 6 when the retarder 2 is not used to brake the vehicle 1. Thus the fuel consumption of the vehicle 1 may be reduced. Filling and draining of torus 44 with fluid 46 is via a fluid circuit. The torus 44 must be filled with fluid 46 as quickly as possible when the braking effect from the retarder 2 is desired. A slow filling initially entails a lack of a braking effect from the retarder 2, which entails an exaggerated use of the wheel brakes of the vehicle 1, which will be exposed to unnecessary wear. The clutch device 4 according to the invention entails that the first shaft 18 and thus the retarder 2 may be disconnected from the gearbox 6, which entails that the retarder 2 does not have a braking effect on the vehicle 1 when the retarder 2 is disengaged. When the retarder 2 is to be engaged, the retarder 2 must in a quick and efficient manner be connected mechanically with the output shaft 30 of the gearbox 6. In order to achieve this, a first and a second clutch element 54, 56 is arranged between the first and second shafts 18, 22. According to the first embodiment, the first clutch device 54 is a friction clutch of the multi-plate clutch type. The second clutch element 56 is, according to the embodiment displayed, a claw clutch of the form bound type. The second clutch device 56 comprises an axially shiftable sleeve 58, which is equipped with teeth 60 which are adapted to engage with corresponding teeth 62 on the first and second shafts 18, 22. The second shaft 22 is arranged co-axially with the first shaft 18 and the second shaft 22 is preferably arranged through rolling bearings 63 on the first shaft 18.

When the retarder 2 is to be engaged in order to brake the vehicle 1, the clutch device 4 is thus engaged, so that the first shaft 18 is connected with the second shaft 22 via the first clutch element 54. Since the second shaft 22 rotates from the start and the first shaft 18 stands still, the first clutch element 54 will make the first shaft 18 rotate. The first clutch element 54 is applied by a first power element 64, which may be a pneumatic or a hydraulic cylinder, or an electric engine, the first power element 64 of which is connected to the control device 16, which impacts a first valve 66 or a switch to the first power element 64. The first clutch element 54 is, according to the embodiment, a multi-plate clutch, which through friction connects the first and the second shafts 18, 22. The first power element 64 may also be built into the multi-plate clutch, and with a piston act directly on the discs in the multi-plate clutch. The multi-plate clutch will, however, not be able to transmit the braking torque which arises when the retarder 2 is to brake the vehicle 1. For this reason, the second clutch element 56 is connected, which consists of a form shaped clutch, such as a claw clutch. The second clutch element 56 is dimensioned to be able to transfer the large braking torque which is exerted by the retarder 2. The connection of the claw clutch is carried out through a second power element 68, which may be a pneumatic or a hydraulic cylinder, or an electric engine, the second power element 68 of which is connected to the control device 16, which influences a second valve 70 or a switch to the second power element 68.

Fig. 3 shows a section view of the first embodiment of the clutch device 4 for a retarder 2, according to the present invention, in a connected state. The claw clutch, which comprises a sleeve 58 has been displaced on the first shaft 18 in a direction toward the second shaft 22 and engages with teeth 62, which are designed on the periphery of the second shaft 22. The corresponding teeth 62 also exist on the periphery of the first shaft 18, so that the sleeve 58, with its internal teeth 60 in a form-bound manner, connects the first and the second shafts 18, 22 with each other. When the sleeve 58 is displaced to connect the first and second shafts 18, 22 with each other, the first clutch element 54 must be released at the same time as the sleeve 58 is to engage with the teeth 62 on the second shaft 22. This clutch manoeuvre is achieved with the power ele- ments 64, 68 controlled by the control device. The first and second power elements 64, 68, in order to control the first and second clutch elements, may be designed in different ways. According to the first embodiment, the second power element 68 is preferably connected to a manoeuvring fork 72, which engages with the sleeve 58 and moves the sleeve 58 between the connected and disconnected positions.

Fig. 4 shows a section view of a second embodiment of a clutch device for a retarder according to the present invention. The first and second embodiments differ from the first embodiment in that the power element 68' is one entity connected with the second clutch element 58' where the second power element 68' operate in an axial direction in order to connect the first and second shafts 18, 22 with the second clutch element 58', and where a return spring 74 operates to disconnect the first and second shafts 18, 22. Fig. 4 shows the retarder 2 only schematically arranged at the first shaft 18. When the retarder 2 is to be engaged in order to brake the vehicle 1, the clutch device 4 is thus engaged, so that the first shaft 18 is connected with the second shaft 22 via the first clutch element 54. Since the second shaft 22 rotates from the start and the first shaft 18 stands still, the first clutch element 54 will make the first shaft 18 rotate. The first clutch element 54 is applied by a first power element 64, which may be a pneumatic or a hydraulic cylinder, or an electric engine, the first power element 64 of which is connected to the control device 16, which impacts a first valve 66 or a switch to the first power element 64. When the first valve 66 is impacted, a fluid in the form of compressed air or hydraulic fluid is led through a first central channel 76 formed in the first shaft 18, which extends in the longitudinal direction of the first shaft 18. The fluid is led through the first central channel 76 and further to the first power element 64. The first clutch element 54 is, according to the second embodiment, a multi-plate clutch which connects the first and the second shafts 18, 22 through friction. The first power element 64 is, in the displayed embodi- ment, in-built in the multi-plate clutch. The multi-plate clutch will, however, not be able to transmit the braking torque which arises when the retarder 2 is to brake the vehicle 1. For this reason, the second clutch element 56' is connected, which, according to the second embodiment, consists of a form bound clutch such as a claw clutch. The second clutch element 56' is dimensioned to be able to transfer the substantial braking torque which is exerted by the re- tarder 2. The connection of the claw clutch is carried out through the second power element 68', which may be a pneumatic or a hydraulic cylinder, where the claw clutch consists of a circular case shaped piston. The second power element 68' is connected to the control device 16, which impacts a second valve 70 or a switch of the second power element 68'. When the second valve 70 is impacted, a fluid in the form of compressed air or hydraulic fluid is led through a second central channel 78 formed in the first shaft 18, which extends in the longitudinal direction of the first shaft 18. The fluid is led through the second central channel 78 and further to the second power element 68'. Above the first and the second shafts' 18, 22 central shaft, the second clutch element 56' is displayed in a connected position between the first and the second shafts 18, 22, and below the central shaft the second clutch element 56' is displayed in a disconnected position between the first and the second shafts 18, 22.

When the second clutch element 56, 56' is connected, the retarder's 2 torus 44 is filled with fluid 46, which entails that the retarder 2 will exert a braking action on the vehicle 1, as de- scribed above. According to the above, the retarder 2 is described as being arranged at a vehicle 1 in order to brake the vehicle 1, but it is also possible to use the retarder 2 according to the present invention for other applications. According to the above, the vehicle 1, the combustion engine 8, the gearbox 6 or the propeller shaft 12 may constitute a driving source, which is connected directly or indirectly to the retarder 2. Other driving sources may, how- ever, be connected to the retarder 2.

By arranging the first and the second clutch elements 56, 56', 58, 58' on each side of the second shaft 22 in the second shaft's 22 longitudinal direction, the dimensions of the clutch device 4, and thus the dimensions of the retarder 2, may be reduced, which entails a weight reduction in the retarder 2 and also the vehicle 1 in which the retarder 2 is mounted. The fuel consumption of the vehicle 1 may thus be reduced. Preferably, the first and second clutch elements 56, 56', 58, 58' are arranged on each side of the teeth 24 in the longitudinal direction of the second shaft 22.

The method for the connection of the retarder 2, according to the present invention, is described below jointly with the flow chart in Fig. 5, the method of which comprises the steps: a) to actuate the first clutch element 54, so that the second shaft 22 brings the first shaft 18 to rotate with the same speed as the second shaft 22; b) to actuate a second clutch element 56, 56', which connects the first and the second shafts 18, 22 with each other, and

c) to engage the retarder 2 by adding fluid 46 to the rotor 20. The method also comprises the additional step:

d) to release the first clutch element 54 while the second clutch element 56, 56' is actuated to connect the first and the second shafts 18, 22.

The components and features specified above may within the framework of the invention be combined between different embodiments specified.