Variable displacement lubricant pump

The present invention is directed to a variable displacement lubricant pump for providing pressurized lubricant, in particular to a mechanically driven variable displacement lubricant pump for providing pressurized lubricant to internal combustion engine.

The lubricant pump is mechanically driven by the engine, for example via a gear or belt, and is fluidically coupled to the engine for pumping the pressurized lubricant to and through the engine. The variable displacement of the lubricant pump allows controlling and/or stabilizing a pump discharge pressure of the lubricant pump and thereby allows, for example, controlling and/or stabilizing a lubricant gallery pressure in the engine.

Variable displacement lubricant pumps are, for example, described in WO 2018/068841 Al and US 9,670,925 B2. The described variable displacement lubricant pumps comprise a static pump housing, a rotatable pump rotor with several rotor vanes configured to rotate within a shiftable control ring, the control ring configured to be shiftable in a shifting direction between a maximum-eccentricity position and a minimum-eccentricity position. The described variable displacement lubricant pumps also comprise an suction chamber configured to be filled with non-pressurized lubricant during pump operation, an discharge chamber configured to be filled with pressurized lubricant during pump operation, and a pilot chamber configured to be loaded with a pilot chamber hydraulic pressure during pump operation and designed in that way that the control ring is loaded toward the minimum-eccentricity position by the pilot chamber hydraulic pressure. The described variable displacement lubricant pumps also comprise a pilot chamber loading line configured to fluid ically connect the pilot chamber with a high pressure and a pilot chamber draining line configured to fluid ically connect the pilot chamber with a low pressure.

The described variable displacement lubricant pumps are all provided with a separate external hydraulically and/or electrically controlled valve arrangement for controlling a loading lubricant flow through the pilot chamber loading line and/or or draining lubricant flow through the pilot chamber draining line as required so as to control the pilot chamber hydraulic pressure during pump operation. The components of the separate external valve arrangement however require additional space and cause additional cost.

An object of the present invention is therefore to provide a compact and cost-effective variable displacement lubricant pump.

This object is achieved with a variable displacement lubricant pump with the features of claim 1.

The variable displacement lubricant pump according to the invention is provided with a static pump housing which defines a pump inlet and a pump outlet. The pump housing typically comprises a main housing body which defines a plurality of pump chambers, and comprises a separate housing cover which is (flu id-tig htly) attached to the housing main body. The pump inlet is typically fluidically connected with a lubricant tank, and the pump outlet is typically fluidically connected with an engine so as to provide the engine with pressurized lubricant.

The variable displacement lubricant pump according to the invention is also provided with a rotatable pump rotor which is arranged inside the pump housing, in particular inside a pumping chamber which is defined by the pump housing and a shiftable control ring. The pump rotor is configured to rotate about a static rotation axis. The pump rotor comprises a plurality of rotor vanes which define a plurality of pumping chamber compartments in between them. The rotor vanes and thus the pumping chamber compartments are configured to rotate within the pumping chamber of the control ring to thereby pump lubricant from the pump inlet to the pump outlet. The pump rotor is mechanically driven by the engine, for example via a belt drive or a gearing.

The variable displacement lubricant pump according to the invention is also provided with a shiftable control ring which is arranged in the pump housing and which defines the - typically substantially cylindrical - pumping chamber in which the pump rotor is arranged. The control ring is configured to be shiftable with respect to the pump rotor rotation axis in a shifting direction to vary an eccentricity of the pumping chamber center with respect to the pump rotor rotation axis so as to vary a nominal fluid displacement and thus a volumetric pumping performance of the pump rotor. The control ring is in particular shiftable between a maximumeccentricity position with a maximum volumetric pumping performance and a minimum-eccentricity position with a minimum volumetric pumping performance. The control ring can be provided exactly linearly shiftable or can be provided pivotable with a substantially arc-shaped shifting direction. The control ring is typically preloaded into the maximumeccentricity position by a preload spring.

The variable displacement lubricant pump according to the invention is also provided with a suction chamber and with a discharge chamber which are both defined by the pump housing and by the control ring. The suction chamber and the discharge chamber are typically located radially outwardly of the pumping chamber at opposite lateral sides of the control ring. The suction chamber is fluidically connected with the pump inlet and is configured to be filled with non-pressurized lubricant during pump operation. The suction chamber is typically filled with lubricant with substantially atmospheric pressure which is drawn from the lubricant tank. The discharge chamber is fluidically connected with the pump outlet and is configured to be filled with pressurized lubricant during pump operation.

The variable displacement lubricant pump according to the invention is also provided with a pilot chamber which is defined by the pump housing and the control ring. The pilot chamber is configured to be loaded with a pilot chamber hydraulic pressure during pump operation. The pilot chamber is located radially outwardly of the pumping chamber and is designed in that way that the control ring is loaded toward the minimum-eccentricity position by the pilot chamber hydraulic pressure. The present control ring shifting position and thus the present volumetric pumping performance of the pump rotor is therefore defined by the present pilot chamber hydraulic pressure. The pilot chamber hydraulic pressure is directly or indirectly hydraulically coupled with the pump discharge pressure which allows the variable displacement lubricant pump to provide a relatively constant pump discharge set pressure independent of the present rotational speed of the pump rotor. The basic functional principle of a variable displacement lubricant pump with a shiftable control ring and a pilot chamber as described above is commonly known and is therefore not described in detail.

The variable displacement lubricant pump according to the invention is also provided with a pilot chamber loading channel and with a pilot chamber draining channel. The pilot chamber loading channel is configured to fluidically connect the pilot chamber with the discharge chamber, and the pilot chamber draining channel is configured to fluidically connect the pilot chamber with the suction chamber. The pilot chamber loading channel and the pilot chamber draining channel are preferably provided internally, wherein the pilot chamber loading channel and the pilot chamber draining channel are typically defined by the pump housing and/or by the control ring.

According to the invention, the variable displacement lubricant pump is provided with a passive internal valve arrangement which is defined by the pump housing and by the control ring and which is configured to control the loading lubricant flow through the pilot chamber loading channel as well as to control the draining lubricant flow through the pilot chamber draining channel. The passive internal valve arrangement according to the invention is directly mechanically regulated by the shiftable control ring so that the loading lubricant flow and the draining lubricant flow are inherently controlled based on the present shifting position of the control ring without the need of any separate active valve control means.

The self-adjusting passive internal valve arrangement according to the invention is provided completely inside the pump housing and provides a reliable control-ring-position-based control of the pilot chamber hydraulic pressure during pump operation without the need of any separate external control valves or valve control means. This provides a compact and cost- effective variable displacement lubricant pump.

In a preferred embodiment of the present invention, the internal valve arrangement comprises a draining valve mechanism for controlling the draining lubricant flow, wherein a moveable, flow-controlling part of the draining valve mechanism is defined by the control ring. The draining valve mechanism is therefore directly (mechanically) regulated by the control ring without the need of any separate flow-regulation or actuation elements. This provides a reliable control-ring-position-based control of the draining lubricant flow and thus a reliable and also compact and cost- effective variable displacement lubricant pump.

In a more preferred embodiment of the present invention, the draining valve mechanism is defined by static pump-housing-sided closing shoulder provided at the pump housing and by a corresponding moveable controlring-sided closing shoulder provided at the control ring. The moveable control-ring-sided closing shoulder defines the moveable, draining-flow- controlling part of the draining valve mechanisms. The control-ring-sided closing shoulder is always displaced with respect to the static pump- housing-sided closing shoulder if the control ring is shifted. The two corresponding closing shoulders are designed in that way that they are in contact with each other if the control ring is positioned between the maximum-eccentricity position and a draining-channel-opening position, and that they are not in contact with each other if the control ring is positioned between the draining-channel-opening position and the minimum-eccentricity position. The two closing shoulders partially define the pilot chamber draining channel so that the draining lubricant flow has to flow between the two closing shoulders. The pilot chamber draining channel is therefore fluidically closed if the two closing shoulders are in contact with each other, and is fluidically open if the two closing shoulders are not in contact with each other. The distance between the maximumeccentricity position and the draining-channel-opening position and thus the position at which the draining channel is opened/closed during a control ring movement can be easily and accurately defined via a shifting-direction extent of the contact area between the two closing shoulders in the maximum-eccentricity position of the control ring. The two corresponding closing shoulders provide a simple and reliable internal draining valve mechanism. Preferably, the internal valve arrangement comprises a loading valve mechanism for controlling the loading lubricant flow, wherein a moveable, flow-controlling part of the loading valve mechanism is defined by the control ring. The loading valve mechanism is therefore directly (mechanically) regulated by the control ring without the need of any separate flow-regulation or actuation elements. This provides a reliable control-ring-position-based control of the loading lubricant flow and thus a reliable and also compact and cost-effective variable displacement lubricant pump.

More preferably, the loading valve mechanism is defined by a pump- housing-sided loading groove provided at a sliding surface of the pump housing and by a corresponding control-ring-sided loading groove provided at a sliding surface of the control ring, wherein the two sliding surfaces are in frictional contact with each other. The control-ring-sided loading groove is moveable with respect to the static pump-housing-sided loading groove and thus defines the moveable, loading-flow-controlling part of the loading valve mechanism. The control-ring-sided loading groove is always displaced with respect to the static pump-housing-sided loading groove if the control ring is shifted. The two corresponding loading grooves are designed in that way that they overlap if the control ring is positioned between the maximum-eccentricity position and a loading-channel-closing position so as to define a lubricant passage which allows a lubricant flow between the two loading grooves. The two corresponding loading grooves are furthermore designed in that way that they do not overlap if the control ring is positioned between the loading-channel-closing position and the minimum-eccentricity position so as to prevent a lubricant flow between the loading grooves. The two corresponding loading grooves - at least partially - define the pilot chamber loading channel so that the loading lubricant flow through the pilot chamber loading channel is controlled by the flow cross-section of the lubricant passage defined by the overlapping loading grooves. The pilot chamber loading channel is fluidically closed if the two loading grooves do not overlap. The distance between the maximum-eccentricity position and the loading-channel-closing position and thus the position at which the loading channel is opened/closed during a control ring movement can be easily and accurately defined via a shiftingdirection extent of the lubricant passage in the maximum-eccentricity position of the control ring. The two corresponding loading grooves provide a simple and reliable internal loading valve mechanism.

In a preferred embodiment of the present invention, the draining-channelopening position and the loading-channel-closing position substantially coincide so that the pilot chamber loading channel is closed substantially at the same time when the pilot chamber draining channel is opened, and vice versa. The pilot chamber loading channel and the pilot chamber draining channel are therefore not open at the same time, at least not for a significant duration. This prevents or at least minimizes an unfavorable lubricant leakage flow from the high-pressure discharge chamber to the low-pressure suction chamber via the pilot chamber during pump operation and thus provides a reliable and variable displacement lubricant pump.

Typically, the total shifting distance of the control ring is relatively small which allows only a relatively small overlap between the two corresponding loading grooves in the shifting direction. Therefore, the pump-housing- sided loading groove preferably extends substantially transversely to the shifting direction, and the control-ring-sided loading groove preferably comprises a passage-providing section which extends substantially parallel to the pump-housing-sided loading groove. This allows the two corresponding loading grooves to be provided with a relatively large overlap in the transverse direction and thus allows the lubricant passage defined by the overlap of the two corresponding loading grooves to be provided with a relatively large flow cross-section. The relatively large flow cross-section ensures a reliable fluidic communication between the pilot chamber and the discharge chamber if the pilot chamber loading channel is open. This provides a reliable variable displacement lubricant pump.

Internal combustion engines typically require different lubricant pressures for different engine speeds. In a preferred embodiment of the present invention, a separate auxiliary pilot chamber is therefore provided which is configured to be loaded with an auxiliary pilot chamber hydraulic pressure during pump operation and configured to be temporarily fluidically connected to a high pressure via an auxiliary pilot chamber load line, wherein the auxiliary pilot chamber is designed in that way that the control ring is loaded toward the minimum-eccentricity position by the auxiliary pilot chamber hydraulic pressure. The auxiliary pilot chamber is typically configured to be either directly or indirectly, e.g. via an auxiliary pilot chamber control valve, fluidically connected with the discharge chamber or with an engine lubricant gallery. The separate auxiliary pilot chamber allows the variable displacement lubricant pump to be designed for two different pump discharge set pressure levels. This provides a versatile variable displacement lubricant pump.

An embodiment of the present invention is described with reference to the enclosed drawings, wherein figure 1 shows a top view of an open (without housing cover) variable displacement lubricant pump according to the invention, and figure 2 shows a cross sectional view of a marked pump section of the lubricant pump of figure 1, figure 3 shows an enlarged view of the marked pump section of the variable displacement lubricant pump of figure 1, wherein a control ring is positioned in a maximum-eccentricity position, figure 4 shows the pump section of figure 2, but with the control ring positioned in a loading-channel-closing position, figure 5 shows the section of figure 2, but with the control ring positioned in a minimum-eccentricity position, and figure 6 shows an idealized, simplified progression of a pump discharge pressure as a function of a pump rotor speed for the variable displacement lubricant pump of figure 1.

Fig. 1 shows a variable displacement lubricant pump 10 which is configured to draw non-pressurized lubricant from a lubricant tank 12 and to provide pressurized lubricant to an internal combustion engine 14.

The lubricant pump 10 comprises a static pump housing 16 with a housing main body 18 and a housing cover 19 which is attached to the housing main body 18.

The lubricant pump 10 comprises a shiftable control ring 20 which is arranged in the pump housing 16 and which radially defines a substantially cylindrical pumping chamber 22, and comprises a rotatable pump rotor 24 which is arranged in the pumping chamber 22 so as to be rotatable about a static rotor rotation axis R. The control ring 20 is configured to be shiftable in a shifting direction S between a maximum-eccentricity position and a minimum-eccentricity position so as to vary an eccentricity of a pumping chamber center with respect to the rotor rotation axis R.

The pump rotor 24 comprises a plurality of radially shiftable rotor vanes 26, wherein the pump rotor 24 is configured in that way that the rotor vanes 26 are pressed against a radial inside of the pumping chamber 22 if the pump rotor 24 is rotating. The rotor vanes 26 define a plurality of fluidically separated pumping chamber compartments 28 between them.

The lubricant pump 10 comprises a suction chamber 30 and a discharge chamber 32 which are located at different lateral sides of the control ring 20 and which are defined by the control ring 20 and the pump housing 16. The suction chamber 30 is fluidically connected with the lubricant tank 12 and is configured to be filled with non-pressurized lubricant (typically with substantially atmospheric pressure) drawn from the lubricant tank 12 during pump operation. The discharge chamber 32 is fluidically connected with the internal combustion engine 14 and is configured to be filled with pressurized lubricant during pump operation. The discharge chamber 32 is, in particular, filled with lubricant with a pump discharge pressure PD.

The lubricant pump comprises a preload spring 34 which is arranged in a spring chamber 36. The spring chamber 36 is located at a first front end of the control ring 20 and the preload spring 34 is configured to preload the control ring 20 toward the maximum-eccentricity position. The spring chamber 36 is directly fluidically connected with the suction chamber 30 via an internal spring chamber fluid channel 38.

The lubricant pump 10 comprises a pilot chamber 40 and a separate auxiliary pilot chamber 42. Both pilot chambers 40,42 are located at a second front end of the control ring 20 which is opposite to the first front end of the control ring 20. The pilot chamber 40 is configured to be loaded with a pilot chamber hydraulic pressure during pump operation, and the auxiliary pilot chamber 42 is configured to be loaded with an auxiliary pilot chamber hydraulic pressure during pump operation. The pilot chamber 40 is designed in that way that the control ring 20 is loaded toward the minimum-eccentricity position by the pilot chamber hydraulic pressure, and the auxiliary pilot chamber 42 is designed in that way that the control ring 20 is loaded toward the minimum-eccentricity position by the auxiliary pilot chamber hydraulic pressure.

The auxiliary pilot chamber 42 is fluidically connected with an external auxiliary pilot chamber control valve 44 via an auxiliary pilot chamber load line 46. The auxiliary pilot chamber control valve 44 is configured to be hydraulically regulated by the pump discharge pressure PD. The auxiliary pilot chamber control valve 44 is in particular configured to fluidically connect the auxiliary pilot chamber 42 with the lubricant tank 12 if the pump discharge pressure PD is less than a defined switching threshold value, and is configured to fluidically connect the auxiliary pilot chamber 42 with the pump discharge pressure PD if the pump discharge pressure PD is equal to or greater than the defined switching threshold value. The auxiliary pilot chamber 42 is therefore configured to be temporarily fluidically connected to a high pressure.

The lubricant pump 10 comprises a pilot chamber loading channel 48 and a pilot chamber draining channel 50 which, in the present embodiment, are both provided internally, and are both defined by the pump housing 16 and the control ring 20.

The pilot chamber loading channel 48 is substantially defined by a controlring-sided loading groove 52 and by a corresponding pump-housing-sided loading groove 54. The control-ring-sided loading groove 52 is provided at a control ring sliding surface 56 of the control ring 20. The pump-housing- sided loading groove 54 is provided at a housing sliding surface 58 of the pump housing 16, in particular of the housing cover 19, the housing sliding surface 58 being in frictional contact with the control ring sliding surface 56. The control-ring-sided loading groove 52 is designed substantially L- shaped with an inflow section 53 which extends substantially parallel to the shifting direction S and with a passage-providing section 55 which extends substantially perpendicular to the shifting direction S. The pump- housing-sided loading groove 54 is designed substantially linear and extends substantially perpendicular to the shifting direction S and thus substantially parallel to the passage-providing section 55 of the controlring-sided loading groove 52. The control-ring-sided loading groove 52 is directly fluidically connected with the discharge chamber 32, and the pump-housing-sided loading groove 54 is directly fluidically connected with the pilot chamber 40. The pilot chamber loading channel 48 is thus configured to fluidically connect the pilot chamber 40 with the discharge chamber 32.

The pilot chamber draining channel 50 is substantially defined by a draining recess 60 which is provided in a pump housing section which separates the pilot chamber 40 from the suction chamber 30. The draining recess 60 is designed in that way that the pilot chamber draining channel 50 is configured to fluidically connect the pilot chamber 40 with the suction chamber 30.

The lubricant pump 10 comprises a passive internal valve arrangement 62 with a loading valve mechanism 64 which is configured to control a loading lubricant flow LF through the pilot chamber loading channel 48, and with a draining valve mechanism 66 which is configured to control a draining lubricant flow DF through the pilot chamber draining channel 50.

The loading valve mechanism 64 is defined by the moveable control-ringsided loading groove 52 and by the static pump-housing-sided loading groove 54, in particular by the passage-providing section 55 of the controlring-sided loading groove 52 and by the pump-housing-sided loading groove 54. The two loading grooves 52,54 are designed in that way that they overlap if the control ring 20 is positioned between the maximumeccentricity position shown in Fig. 3 and a loading-channel-closing position shown in Fig. 4 so as to define a lubricant passage 68 which allows a lubricant flow between the two loading grooves 52,54. The two loading grooves 52,54 are furthermore designed in that way that they do not overlap if the control ring 20 is positioned between the loading-channelclosing position and the minimum-eccentricity position shown in Fig. 5 so as to prevent a lubricant flow between the two loading grooves 52,54 and thus to prevent a lubricant flow through the pilot chamber loading channel 48. The flow-cross-section of the lubricant passage 68 regulates the lubricant flow from the control-ring-sided loading groove 52 into the pump- housing-sided loading groove 54 and thus regulates the present loading lubricant flow LF through the pilot chamber loading channel 48. The flowcross-section of the lubricant passage 68 and thus the loading lubricant flow LF is maximum if the control ring 20 is positioned in the maximumeccentricity position.

The draining valve mechanism 66 is defined by a moveable control-ringsided closing shoulder 70 which is provided at the control ring 20, and by a corresponding static pump-housing-sided closing shoulder 72 which is provided at the pump housing 16, in particular at the housing main body 18. The two closing shoulders 70,72 partially define the pilot chamber draining channel 50. The two closing shoulders 70,72 are designed in that way that they are in contact with each other if the control ring 20 is positioned between the maximum-eccentricity position and a drainingchannel-closing position so as to fluid ica lly close the pilot chamber draining channel 50. The two closing shoulders 70,72 are furthermore designed in that way that they are not in contact with each other if the control ring 20 is positioned between the draining-channel-closing position and the maximum-eccentricity position so as to fluidically open the pilot chamber draining channel 50. The draining-channel-closing position, in the present embodiment, coincides with the loading-channel-opening position shown in Fig. 4. The present draining lubricant flow DF is regulated by a present clearance 74 between the two closing shoulders 70,72, wherein the clearance 74 and thus the draining lubricant flow DF is maximum if the control ring 20 is positioned in the minimum-eccentricity position. The passive internal valve arrangement 62 is completely defined by the pump housing 16 and by the control ring 20, wherein the static parts of both valve mechanisms 64,66, i.e. the pump-housing-sided loading groove 54 and the pump-housing-sided closing shoulder 72, are defined by the pump housing 16, and wherein the moveable parts of both valve mechanisms 64,66, i.e. the control-ring-sided loading groove 52 and the control-ring-sided closing shoulder 70, are defined by the control ring 20. The passive internal valve arrangement 62 is thus directly mechanically regulated by the control ring 20 so that the present loading lubricant flow LF and the present draining lubricant flow DF both are inherently controlled based on the present shifting position of the control ring 20.

Fig. 6 shows an idealized, simplified progression of the pump discharge pressure PD as a function of a pump rotor speed RS of the lubricant pump 10.

In a first speed interval II, the pump discharge pressure PD and thus the pilot chamber hydraulic pressure increases with increasing pump rotor speed RS because the control ring 20 is pushed in the maximumeccentricity position by the preload spring 34.

At a first pump rotor speed value RSI, the control-ring load toward the minimum-eccentricity position generated by the pilot chamber hydraulic pressure of the pilot chamber 40 is equal to the control-ring load toward the maximum-eccentricity position generated by the preload spring 34.

In a second speed interval 12, the pump discharge pressure PD therefore remains substantially constant at a first pump discharge set pressure level PD1 because the control ring 20 is continuously shifted toward the minimum-eccentricity position with increasing pump rotor speed RS thereby continuously reducing the nominal fluid displacement and thus the volumetric pumping performance of the pump rotor 24.

At a second pump rotor speed value RS2, the control ring 20 reaches the loading-channel-closing position/draining-channel-opening position so that the pilot chamber 40 is fluidically separated from the discharge chamber 32 and is fluidically connected with the suction chamber 30. The pilot chamber hydraulic pressure thus decreases so that the control ring 20 is moved toward the maximum-eccentricity position again caused by the preload of the preload spring 34. This however causes the pilot chamber 40 to be fluidically connected with the discharge chamber 32 again so that the control ring 20 is moved toward the minimum-eccentricity position again. The control ring 20 is therefore kind of "frozen" at about the loadingchannel-closing position/draining-channel-opening position.

In a third speed interval 13, the pump discharge pressure PD therefore increases again with increasing pump rotor speed RS because of the "frozen" and thus non-moving control ring 20.

At a third pump rotor speed value RS3, the pump discharge pressure PD reaches the switching threshold value of the auxiliary pilot chamber control valve 44 so that the auxiliary pilot chamber 42 is fluidically connected to and thus loaded with the pump discharge pressure PD. This causes an auxiliary control-ring load toward the minimum-eccentricity position which is directly proportional to the pump discharge pressure PD.

In a fourth speed interval 14, the pump discharge pressure PD remains substantially constant at a second pump discharge set pressure level PD2 because the control ring 20 is continuously shifted toward the minimumeccentricity position with increasing pump rotor speed RS due to the continuously increasing auxiliary control-ring load toward the minimum- eccentricity position which is caused by the continuously increasing hydraulic pressure of the auxiliary pilot chamber 42.

A similar pump discharge pressure progression can be realized if the auxiliary pilot chamber 42 is directly fluidically connected with the pump discharge PD without an intermediate auxiliary pilot chamber control valve 44. The auxiliary pilot chamber 42 can also be configured to be connected with an engine lubricant gallery pressure or any other engine lubricant pressure instead of with the pump discharge pressure PD.

Reference List

10 variable displacement lubricant pump

12 lubricant tank

14 internal combustion engine

16 pump housing

18 housing main body

19 housing cover

20 control ring

22 pumping chamber

24 pump rotor

26 rotor vanes

28 pumping chamber compartments

30 suction chamber

32 discharge chamber

34 preload spring

36 spring chamber

38 spring chamber fluid channel

40 pilot chamber

42 auxiliary pilot chamber

44 auxiliary pilot chamber control valve

46 auxiliary pilot chamber load line

48 pilot chamber loading channel

50 pilot chamber draining channel

52 control-ring-sided loading groove

53 inflow section

54 pump-housing-sided loading groove

55 passage-providing section

56 control ring sliding surface

58 housing sliding surface

60 draining recess 62 passive internal valve arrangement

64 loading valve mechanism

66 draining valve mechanism

68 lubricant passage

DF draining lubricant flow

11-14 pump rotor speed intervals

LF loading lubricant flow

PD pump discharge pressure

PD1,PD2 pump discharge set pressure levels

R rotor rotation axis

RS pump rotor speed

RS1-RS3 pump rotor speed values

S shifting direction