VEHICLE HYDRAULIC DEVICE

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No. 2015-181242 filed on Sep. 14, 2015, the entire contents of which are hereby incorporated by reference.

BACKGROUND

1. Technical Field

The present disclosure relates to a vehicle hydraulic device having a vane pump as the oil pressure source, and more particularly to a vehicle hydraulic device that operates smoothly even at the start and is little affected by fluctuations in oil pressure of a discharge oil passage during operation of the vane pump.

2. Description of Related Art

A vane pump driven by an engine has, inside a pump housing with a substantially elliptical inner peripheral cam surface, for example, a plurality of variable-displacement pump chambers that are defined by a rotor fitted on a rotating shaft and a plurality of vanes radially fitted into vane housing groves provided in the rotor. As the vanes rotate while being pressed against the inner peripheral surface of the pump housing, the volumes of the pump chambers vary and a discharge force is applied to a working fluid.

The force for pressing the vanes against the inner peripheral surface of the pump housing is derived from a rotational centrifugal force and a backpressure that presses the vanes against the inner peripheral surface of the pump housing inside the rotor. The working fluid discharged from the vane pump is used to obtain this backpressure. However, if the rotation speed of the rotor is low at the start of the vane pump, the pump may fail to start smoothly. This is because, even when the centrifugal force of the rotating vanes and the backpressure generated by the working fluid discharged from the vane pump are combined, the force that presses the vanes against the inner peripheral surface of the pump housing is too small.

To address this problem, Japanese Patent Application Publication No. 2008-286108 discloses a technique for raising the backpressure inside a vane pump at the start of the vane pump. Specifically, the oil pressure of a working fluid discharged from an electric motor-driven oil pump is supplied through a backpressure oil passage into vane housing grooves provided inside the rotor, so that a plurality of vanes that are radially fitted into the vane housing grooves formed in the rotor are pressed against the inner peripheral surface of a pump housing. Thus, the proposed vane pump operates smoothly even at the start.

In the vane pump of JP 2008-286108 A, if the discharge pressure of the vane pump exceeds the backpressure inside the vane housing grooves, the vanes may be pushed into the housing grooves and the pressure of the working fluid discharged from the vane pump may decrease.

SUMMARY

Having been devised in the context of these circumstances, the present disclosure provides a vehicle hydraulic device having a vane pump of which pump chambers vary in volume to apply a discharge force to a working fluid as vanes rotate while being pressed against the inner peripheral surface of a pump housing. The vehicle hydraulic device according to the present disclosure operates smoothly even at the start and is little affected by fluctuations in oil pressure of the discharge oil passage during operation of the vane pump.

According to one aspect of the present disclosure, a vehicle hydraulic device including a vane pump, an oil pressure control circuit, an electric motor-driven oil pump, and a shuttle valve, is provided. The vane pump is driven to rotate by an engine. The vane pump includes a pump housing, a plurality of vanes, and a rotor. The pump housing has an inner peripheral cam surface with an elliptical sectional shape. The plurality of vanes are provided inside the pump housing. The rotor provides vane housing grooves that house the plurality of vanes so as to be movable in a radial direction of the rotor. The oil pressure control circuit includes a first discharge oil passage, a second discharge oil passage, and a backpressure oil passage. The first discharge oil passage is configured to introduce a working fluid discharged from the vane pump to a device other than the vehicle hydraulic device. The backpressure oil passage is configured to supply a backpressure to the plurality of vanes inside the vane housing grooves. The electric motor-driven oil pump is configured to discharge the working fluid through the second discharge oil passage to the backpressure oil passage. The shuttle valve is provided at a junction of the first discharge oil passage, the second discharge oil passage, and the backpressure oil passage. The shuttle valve is configured to: (i) allow the working fluid to flow from the first discharge oil passage to the backpressure oil passage when the oil pressure of the working fluid in the first discharge oil passage discharged from the vane pump is higher than the oil pressure of the working fluid in the second discharge oil passage discharged from the electric motor-driven oil pump, and (ii) allow the working fluid to flow from the electric motor-driven oil pump to the backpressure oil passage when the oil pressure of the working fluid in the first discharge oil passage discharged from the vane pump is equal to or lower than the oil pressure of the working fluid in the second discharge oil passage discharged from the electric motor-driven oil pump.

According to the oil pressure control circuit as described above, the vane pump operates smoothly, even at the start of the vane pump, with a backpressure applied to the plurality of vanes by the electric motor-driven oil pump. Moreover, even when the oil pressure in the first discharge oil passage fluctuates to a higher pressure during operation of the vane pump, the oil pressure in the first discharge oil passage is supplied by the shuttle valve as the backpressure for the vanes, and the vanes are pushed into the housing grooves. Thus, it is possible to suppress a decrease in pressure of the working fluid discharged from the vane pump and realize stable operation.

In the vehicle hydraulic device, the electric motor-driven oil pump may be configured to actuate only at a start of the engine and when a temperature of the working fluid is equal to or lower than a predetermined temperature.

According to the oil pressure control circuit as described above, the electric motor-driven oil pump is operated only at the start of the engine and when the temperature of the working fluid is equal to or lower than a predetermined temperature. Using the electric motor-driven oil pump thus only when necessary can reduce the usage of electric power.

Moreover, in the vehicle hydraulic device, the oil pressure of the working fluid discharged from the electric motor-driven oil pump may decrease as a temperature of the working fluid rises.

According to the oil pressure control circuit as described above, the oil pressure of the working fluid discharged from the electric motor-driven oil pump decreases as the temperature of the working fluid rises. Thus, the usage of electric power can be further reduced.

Furthermore, in the vehicle hydraulic device, the electric motor-driven oil pump may not start when a time taken for the engine to restart after stopping of the engine is within a predetermined time.

According to the oil pressure control circuit as described above, it is possible to reduce the electric power consumption by preventing the actuation of the electric motor-driven oil pump when the time taken for the engine to restart after stopping is a short time within a predetermined time, since in that case the backpressure is not always reduced so much and then there is no need to actuate the electric motor-driven oil pump.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is a schematic view illustrating the configuration of the major part of a vehicle hydraulic device of a first embodiment of the present disclosure;

FIG. 2 is a front view of a vane pump of the vehicle hydraulic device of FIG. 1, with a cover thereof removed;

FIG. 3 is a schematic view illustrating the configuration of the major part of a vehicle hydraulic device of a second embodiment of the present disclosure;

FIG. 4 is a functional block diagram illustrating the major part of an electric motor control function of an electronic controller of FIG. 3;

FIG. 5 is a flowchart illustrating the major part of the operation of controlling an electric motor-driven oil pump of the vehicle hydraulic device of FIG. 3, i.e., illustrating the control operation for reducing the electric power used by the vehicle hydraulic device; and

FIG. 6 is a one example of a relational map used for obtaining the required rotation speed of the electric motor-driven oil pump according to the temperature of a working fluid of the vehicle hydraulic device of the second embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

In the following, a first embodiment of a vehicle hydraulic device of the present disclosure will be described in detail with reference to the drawings.

FIG. 1 is a schematic view illustrating the configuration of a vehicle hydraulic device 10. The vehicle hydraulic device 10 includes a vane pump 14, an electric motor-driven oil pump 48, and a shuttle valve 50. The vane pump 14 supplies a working fluid to an oil pressure control device 12 that functions as an oil pressure control circuit. The oil pressure control device 12 consumes the working fluid of, for example, a hydraulic cylinder, such as the sheave of an automatic transmission (A/T) or a continuously variable transmission (CVT). The electric motor-driven oil pump 48 supplies a backpressure to the vane pump 14.

The vane pump 14 is driven by the rotation of an engine 15. The vane pump 14 has a first suction port 22, a second suction port 24, a first discharge port 26, and a second discharge port 28. The first suction port 22 and the second suction port 24 are ports through which the working fluid stored in an oil pan 18 is suctioned via an oil strainer 20. The first discharge port 26 and the second discharge port 28 are ports through which the suctioned working fluid is discharged to the outside of the pump. The vane pump 14 further has a first backpressure groove 42 and a second backpressure groove 44 that supply a backpressure to a plurality of vanes 82 that suction and discharge the working fluid. The working fluid is sent from the suction ports 22, 24 to the discharge ports 26, 28 through pump chambers P provided by the vanes 82.

A vane pump discharge oil passage 30, corresponding to the first discharge oil passage, is connected to the first discharge port 26 and the second discharge port 28, and the vane pump discharge oil passage 30 serves as a working fluid supply passage to the oil pressure control device 12 through which the working fluid discharged from the first discharge port 26 and the second discharge port 28 is pumped to the oil pressure control device 12. The vane pump discharge oil passage 30 is also connected to a first input port 50a of the shuttle valve 50, and serves as a working fluid supply passage to the vane pump 14 through which the working fluid discharged from the first discharge port 26 and the second discharge port 28 is pumped to the first backpressure groove 42 and the second backpressure groove 44. An electric motor-driven oil pump discharge oil passage 31, corresponding to the second discharge oil passage, is connected to the other, second input port 50b of the shuttle valve 50, and an output port 50c of the shuttle valve 50 is connected to a backpressure oil passage 36.

A suction oil passage 34 connects the first suction port 22 and the second suction port 24 of the vane pump 14 to the oil pan 18 via the oil strainer 20 such that the working fluid stored in the oil pan 18 is suctioned to the first suction port 22 and the second suction port 24. The suction oil passage 34 also connects the electric motor-driven oil pump 48 to the oil pan 18 via the oil strainer 20 such that the working fluid stored in the oil pan 18 is suctioned to the electric motor-driven oil pump 48. A return oil passage 32 returns the working fluid of the oil pressure control device 12 to the suction oil passage 34 of the vane pump 14.

FIG. 2 is a front view of the vane pump 14 of the vehicle hydraulic device 10, with a pump cover thereof removed. The vane pump 14 is composed of a body 68, a cam ring 70, a side plate 66, a rotor 74, a pump shaft 76, and the pump cover (not shown). The body 68 is provided with a substantially columnar recess 16. The cam ring 70 has a substantially cylindrical shape, and is fitted inside the recess 16 so as to be unable to rotate relative to the body 68. The cam ring 70 corresponds to the pump housing, and is therefore also called the pump housing. The side plate 66 has a disc shape, and is mounted so as to be interposed between a bottom wall surface of the recess 16 of the body 68 and the cam ring 70, with one flat surface and the other flat surface of the side plate 66 in contact with the bottom wall surface of the recess 16 and a substantially circular one end surface of the cam ring 70, respectively. The rotor 74 has a columnar shape, and is housed such that the outer peripheral surface faces an inner peripheral cam surface 78 of the cam ring 70 with a small space therebetween and that one end surface in the direction of a rotational axis can come into sliding contact with the other flat surface of the side plate 66. The pump shaft 76 is fixed to the rotor 74 coaxially with the rotational axis of the rotor 74, is rotatably supported on the body 68, and rotates the rotor 74 in the direction of the arrow indicated in FIG. 2, i.e., in the clockwise direction, according to the driving of a driving source, such as the engine 15. The pump cover is fastened to the body 68 so as to cover the opening of the recess 16 while being in contact with the substantially circular other end surface of the cam ring 70 and able to come into sliding contact with the other end surface of the rotor 74 in the axial direction.

The cam ring 70 has the inner peripheral cam surface 78 that is the inner peripheral surface with a substantially elliptical sectional shape. The rotor 74 includes slits 80, corresponding to the plurality of vane housing grooves, that are formed over the entire axial length of the outer peripheral surface, radially from a center part in the radial direction toward the outer peripheral surface at regular intervals in the circumferential direction, and the plurality of rectangular, plate-shaped vanes 82 that are fitted into the slits 80. Since the slits 80 house the vanes, the slits 80 are also called vane housing grooves. The vane 82 is inserted into the slit 80 such that the side surfaces of the vane 82 in the circumferential direction of the rotor 74 can slide in the radial direction of the rotor 74 over inner walls of the slit 80 facing the vane 82; that the side surfaces of the vane 82 in the axial direction come into sliding contact with the other end surface of the side plate 66 and an inner wall surface of the pump cover, respectively; and that the radially outer end surface of the vane 82 can slide over the inner peripheral cam surface 78 of the cam ring 70.

When the rotor 74 is driven to rotate, the vane 82 is pushed out toward the radially outer side of the rotor 74 from the inner wall of the slit 80 under the backpressure from the first backpressure groove 42 and the second backpressure groove 44, so that the radially outer end surface of the vane 82 is pressed against the inner peripheral cam surface 78 of the cam ring 70 and, in this state, slides over the inner peripheral cam surface 78 in the rotation direction of the rotor 74. Thus, the plurality of pump chambers P are defined by the side surfaces of the adjacent vanes 82 facing each other in the circumferential direction, the inner peripheral cam surface 78, the outer peripheral surface of the rotor 74, the other end surface of the side plate 66, and the inner wall surface of the pump cover. Since the inner peripheral cam surface 78 has a substantially elliptical shape, as the rotor 74 makes one rotation, the vane 82 reciprocates twice inside the slit 80 in the radial direction of the rotor 74, so that the volume of the pump chamber P increases and decreases twice.

In the side plate 66 and the body 68, the pair of first suction port 22 and second suction port 24 communicating with the pump chambers P, which increase in volume according to the rotation of the rotor 74, are formed across the pump shaft 76 so as to straddle both the side plate 66 and the body 68. In the side plate 66 and the body 68, the pair of first discharge port 26 and second discharge port 28 communicating with the pump chambers P, which decrease in volume according to the rotation of the rotor 74, are formed across the pump shaft 76 so as to straddle both the side plate 66 and the body 68. The first discharge port 26 is located on the front side in the rotation direction of the rotor 74 relative to the first suction port 22. The second discharge port 28 is located on the front side in the rotation direction of the rotor 74 relative to the second suction port 24. It is also possible to form the ports 22, 24, 26, 28 only in the side plate 66, instead of forming these ports so as to straddle both the side plate 66 and the body 68.

The side plate 66 communicates with the inner peripheral ends of the slits 80, into which the vanes 82 defining the pump chambers P are fitted, between the first suction port 22 and the first discharge port 26. The first backpressure groove 42 and the second backpressure groove 44 that supply a backpressure for pressing the vanes 82 against the inner peripheral cam surface 78 are formed in a semi-annular shape in the circumferential direction of the rotor 74. The first backpressure groove 42 and the second backpressure groove 44 communicate with the backpressure oil passage 36.

When the vane pump 14 is started according to the driving of the engine 15 and the rotor 74 is rotated in the clockwise direction in FIG. 2, the working fluid inside the oil pan 18 is suctioned through the suction oil passage 34 into the first suction port 22 and the second suction port 24, and carried to each pump chamber P of the vane pump 14 of which the volume increases gradually as the rotor 74 rotates. As the rotor 74 rotates and the volumes of the pump chambers P decrease accordingly, the working fluid suctioned into the pump chambers P is discharged through the first discharge port 26 and the second discharge port 28 to the vane pump discharge oil passage 30. When an electric motor 52 dedicated to the electric motor-driven oil pump 48 is driven along with the start of the engine 15 and the electric motor-driven oil pump 48 is started accordingly, the working fluid inside the oil pan 18 is suctioned through the suction oil passage 34 into the electric motor-driven oil pump 48, and discharged to the electric motor-driven oil pump discharge oil passage 31 communicating with the second input port 50b of the shuttle valve 50.

The vane pump discharge oil passage 30 and the electric motor-driven oil pump discharge oil passage 31 communicate respectively with the first input port 50a and the second input port 50b of the shuttle valve 50. The backpressure oil passage 36 communicates with the output port 50c of the shuttle valve 50. When the oil pressure of the working fluid in the vane pump discharge oil passage 30 discharged from the vane pump 14 is higher than the oil pressure of the working fluid in the electric motor-driven oil pump discharge oil passage 31 discharged from the electric motor-driven oil pump 48, the shuttle valve 50 allows the working fluid to flow from the vane pump discharge oil passage 30 to the backpressure oil passage 36. When the oil pressure of the working fluid in the vane pump discharge oil passage 30 discharged from the vane pump 14 is equal to or lower than the oil pressure of the working fluid in the electric motor-driven oil pump discharge oil passage 31 discharged from the electric motor-driven oil pump 48, the shuttle valve 50 allows the working fluid to flow from the electric motor-driven oil pump discharge oil passage 31 to the backpressure oil passage 36. Thus, the backpressure for pressing the vanes 82 defining the pump chambers P of the vane pump 14 against the inner peripheral cam surface 78 of the cam ring 70 is maintained.

Thus, the vehicle hydraulic device 10 of this embodiment is provided with the electric motor-driven oil pump 48 and the shuttle valve 50, so that the vehicle hydraulic device operates smoothly, even at the start, as a backpressure is applied from the electric motor-driven oil pump 48 to the vanes 82. Moreover, even when the oil pressure of the working fluid discharged from the vane pump exceeds the backpressure inside the slits 80 during operation of the vane pump 14, the working fluid flows from the vane pump discharge oil passage 30 to the backpressure oil passage 36, so that the vanes 82 are pushed into the slits 80 and the pressure of the working fluid discharged from the vane pump 14 does not decrease. Thus, it is possible to suppress the decrease in discharge amount of the vane pump 14 even if the oil pressure in the vane pump discharge oil passage 30 fluctuates to a higher pressure during operation of the vane pump 14.

EMBODIMENT 2

Next, a second embodiment of the present disclosure will be described. In the following second embodiment, those parts that have substantially the same functions as in the first embodiment will be denoted by the same reference signs and the detailed description thereof will be omitted. A vehicle hydraulic device 100 of the second embodiment is different from the vehicle hydraulic device 10 of the first embodiment in that the electric motor-driven oil pump 48 is operated only at the start of the engine 15 and when the temperature of the working fluid is equal to or lower than a predetermined temperature, and in that the oil pressure of the working fluid discharged from the electric motor-driven oil pump 48 is reduced as the temperature of the working fluid rises. Only these differences will be described in detail below using FIG. 3 to FIG. 6.

FIG. 3 is a schematic view illustrating the configuration of the vehicle hydraulic device 100 of the second embodiment of the present disclosure. The configuration of the vehicle hydraulic device 100 is the same as the configuration of the vehicle hydraulic device 10 shown in FIG. 1, i.e., includes the electric motor 52, which drives the electric motor-driven oil pump 48, in addition to the vane pump 14 that supplies the working fluid to the oil pressure control device 12 that consumes the working fluid of, for example, a hydraulic cylinder, such as the sheave of an A/T or a CVT, the electric motor-driven oil pump 48 that supplies a backpressure to the slits 80 of the vane pump 14, the shuttle valve 50, the oil pan 18, the oil strainer 20, and the oil passages for the working fluid to flow through. However, the vehicle hydraulic device 100 is different from the vehicle hydraulic device 10 in that a temperature sensor 54 that detects the temperature of the working fluid, and an electronic controller 56 that controls the electric motor 52 on the basis of the temperature detected by the temperature sensor 54 are provided. The electric motor 52 is driven through a control signal from the electronic controller 56 and actuates the electric motor-driven oil pump 48 to supply the working fluid to the electric motor-driven oil pump discharge oil passage 31. The electronic controller 56 is configured with a so-called microcomputer that includes, for example, a CPU, a RAM, a ROM, and an input-output interface, and the CPU executes output control of the engine 15, speed change control of an automatic transmission (not shown), etc. by processing signals according to a program that is stored in the ROM in advance using the temporary storage function of the RAM.

In the vehicle hydraulic device 100 of this embodiment, to reduce the electric power used for actuating the electric motor-driven oil pump 48, for example, the electric motor 52 is driven only at the start of the engine 15 and when the temperature of the working fluid is equal to or lower than a preset temperature, so as to restrict the actuation of the electric motor-driven oil pump 48. Moreover, to reduce the electric power used for actuating the electric motor-driven oil pump 48, for example, the oil pressure of the working fluid discharged from the electric motor-driven oil pump 48 is reduced as the temperature of the working fluid rises.

FIG. 4 is a functional block diagram illustrating the major part of an electric motor control function of the electronic controller 56, and including an engine start determination unit 62, a working fluid temperature determination unit 60, and an electric motor control unit 58. The engine start determination unit 62 determines whether or not the engine 15 is at start. The working fluid temperature determination unit 60 determines whether or not a working fluid temperature TOIL is equal to or lower than a preset working fluid criterion temperature Te. The electric motor control unit 58 actuates the electric motor 52 by sending an electric motor control signal SM to the electric motor 52 on the basis of the determination of the engine start determination unit 62 and the working fluid temperature determination unit 60. The engine start determination unit 62 may determine whether or not the time from when the engine 15 is driven and stopped last time until the engine 15 is driven this time, i.e., the time taken to restart, is within a predetermined time, and the electric motor control unit 58 may control so as not to start the electric motor 52 if the time taken to restart is within the predetermined time.

FIG. 5 is a flowchart of the major part of the operation of controlling the electric motor-driven oil pump 48 performed by the electronic controller 56 of FIG. 3, i.e., the control operation for reducing the electric power used by the vehicle hydraulic device 100. This operation is executed repeatedly.

In FIG. 5, in step (hereinafter “step” will be omitted) S1 corresponding to the engine start determination unit 62, it is determined whether or not the engine 15 is at start. The current routine ends if the determination result in S1 is negative. If the determination result is affirmative, it is determined in S2, corresponding to the working fluid temperature determination unit 60, whether or not the working fluid temperature TOIL is equal to or lower than the preset working fluid criterion temperature Te on the basis of the signal from the temperature sensor 54. The current routine ends if the determination result in S2 is negative. If the determination result is affirmative, in S3 corresponding to the electric motor control unit 58, the electric motor 52 is actuated on the basis of the electric motor control signal SM from the electric motor control unit 58 and the electric motor-driven oil pump 48 is driven. Under such control, the actuation of the electric motor-driven oil pump is restricted and the electric power used by the vehicle hydraulic device 100 is reduced.

FIG. 6 is one example of a relation (map) stored in advance that is used by the electric motor control unit 58 to obtain the working fluid temperature TOIL (° C.) and the rotation speed (rpm) of the electric motor-driven oil pump 48 required at a given working fluid temperature. Specifically, as the temperature of the working fluid rises, the oil pressure of the working fluid discharged from the electric motor-driven oil pump 48 is reduced, i.e., the rotation speed of the electric motor-driven oil pump 48 is reduced, and thus the electric power used by the vehicle hydraulic device 100 is reduced.

While the present disclosure has been described in detail with reference to the drawings, the present disclosure can also be implemented in other embodiments, and various modifications can be made within the scope of the disclosure.

For example, in the vane pump 14 of the first embodiment and the second embodiment, the cam ring 70 having the inner peripheral cam surface 78 is fitted in the recess 16 of the body 68. However, the present disclosure is not limited thereto, and, for example, the cam ring may be omitted by forming the inner peripheral cam surface 78, facing the outer peripheral surface of the rotor 74, directly on the inner peripheral surface of the recess 16 of the body 68.

In the vane pump of the first embodiment and the second embodiment, the plurality of discharge ports 26, 28 communicate with the oil pressure control device 12 and the working fluid is supplied thereto. However, the working fluid may be supplied from the plurality of discharge ports 26, 28 to separate oil pressure control devices. In that case, a plurality of shuttle valves 50 may be used respectively for the plurality of discharge ports 26, 28, or only one shuttle valve 50 may be used to control the oil pressure of the working fluid in the backpressure oil passage 36 to be supplied to the vanes 82.

VEHICLE HYDRAULIC DEVICE

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