Hydraulic circuit control device

A hydraulic circuit control device that selectively supplies oil to a first oil passage and a second oil passage by an oil pump, the control device includes: an oil passage switching unit adapted to connect the oil pump to either the first oil passage or the second oil passage; a control mode switching unit adapted to switch the control mode of the electric motor to either a torque control mode or a speed control mode; an oil passage selecting unit adapted to select whether to connect the oil pump to the first oil passage or the second oil passage; and a control unit adapted to perform control so that the control mode switching unit switches the control mode to the torque control mode when the first oil passage has been selected, and perform control so that the control mode switching unit switches the control mode to the speed control mode when the second oil passage has been selected.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a hydraulic circuit control device that selectively supplies oil to two oil passages with an oil pump.

Priority is claimed on Japanese Patent Application No. 2005-102507, filed Mar. 31, 2005, and Japanese Patent Application No. 2005-336782, filed Nov. 22, 2005, the contents of which are incorporated herein by reference.

2. Description of Related Art

A vehicle drive system has been developed in which either the front or rear wheels are powered by a main drive source such as an internal combustion engine, while an auxiliary drive source is provided by an electric motor for the other wheels.

Under normal driving conditions in a vehicle equipped with such a drive system, the main drive source drives the front or rear wheels, while the auxiliary drive source is activated to transmit drive power to the other wheels when, for example, setting off in adverse road conditions. In such a vehicle, a hydraulic engaging/disengaging device such as a hydraulic clutch is provided in the power transmission mechanism to deliver power from the driving electric motor serving as the auxiliary drive source, with such a clutch being suitably controllable in accordance with the vehicle running state. For example, at times when driving or regeneration of the electric motor is not required, by using the clutch to cut off power transmission with the electric motor, drive power loss arising from co-rotation of the electric motor can be reduced.

A control unit for a hydraulic actuator resembling the engaging/disengaging device described above has been proposed that provides an accumulator in the oil passage leading to the actuator to reduce the power loss of the oil pump (see, for example, Japanese Unexamined Patent Application, Publication No. 2003-54279).

In this control unit for an actuator, the accumulator is installed in the oil passage on the actuator side, and a check valve that only allows inflow of oil to the actuator side is interposed between the oil pump and the actuator, with the oil pump operating only when the pressure in the accumulator falls.

In the aforementioned control unit, the oil supplied from the oil pump is supplied only to the oil passage on the actuator side, which requires a high pressure. However, there is a clear need for shared use of the same oil pump for oil passages that require a low pressure and a high flow rate for lubrication and the like.

One solution that has been studied is to provide in the oil pump supply passage an oil passage switching valve that switches connection between the oil passage that requires a high pressure and the oil passage that requires a low pressure and a high flow rate, and operate the oil passage switching valve in accordance with requirements on the system side. In this case, it would be necessary to control the pump driving electric motor that drives the oil pump simultaneously with switching the oil passages in order to adjust the oil being supplied to a suitable oil pressure and flow rate.

However, in the case of always using speed control to control the pump driving electric motor, sudden fluctuations in the hydraulic load when used for the oil passage that requires a high pressure may cause step out of the electric motor.

Controlling the pump driving motor by torque control has also been investigated, but in this case, overspeed of the electric motor occurs when used for the oil passage that requires a low pressure and a high flow rate, leading to high power consumption, which is not desirable from the standpoint of energy conservation.

SUMMARY OF THE INVENTION

The present invention has as its object providing a control unit for a hydraulic circuit that can effectively use a common oil pump for an oil passage that requires a high pressure and an oil passage that requires a low pressure and high flow rate without causing problems such as step out and increased power consumption of the pump driving electric motor.

In order to attain the aforementioned object, the present invention provides a hydraulic circuit control device that selectively supplies oil to a first oil passage that requires a high pressure and a second oil passage that requires a low pressure and high flow rate by an oil pump driven by an electric motor, the control device including: an oil passage switching unit adapted to connect the oil pump to either the first oil passage or the second oil passage; a control mode switching unit adapted to switch the control mode of the electric motor to either a torque control mode or a speed control mode; an oil passage selecting unit adapted to select whether to connect the oil pump to the first oil passage or the second oil passage; and a control unit adapted to perform control so that the control mode switching unit switches the control mode of the electric motor to the torque control mode when the oil passage selecting unit has selected the first oil passage, and to perform control so that the control mode switching unit switches the control mode of the electric motor to the speed control mode when the oil passage selecting unit has selected the second oil passage.

In the present invention, when the oil passage selecting unit selects whether to supply oil to the first oil passage or the second oil passage, in accordance with that selection result, the oil passage switching unit and the control mode switching unit are separately controlled by the control unit. By means of the control performed by the control unit, when the oil pump is to be connected to the first oil passage that requires a high pressure, the pump driving electric motor is controlled in the torque control mode, and when the oil pump is to be connected to the second oil passage that requires a low pressure and high flow rate, the pump driving electric motor is controlled in the speed control mode.

The oil passage selecting unit may be adapted to perform oil passage selection based on at least one of a pressure of the first oil passage and a flow rate of the second oil passage.

In this case, when, for example, selecting the oil passage based on the pressure of the first oil passage, the pressure of the first oil passage is monitored so that when the pressure deviates from the set pressure condition, the first oil passage is chosen as the oil passage to connect to the oil pump. Thereby, oil supply is always provided in accordance with the requirements of the first oil passage side. Similarly, when selecting the oil passage based on the flow rate of the second oil passage, the flow rate of the second oil passage is monitored so that when the flow rate deviates from the set flow rate condition, the second oil passage is chosen as the oil passage to connect to the oil pump. Thereby, oil supply is always provided in accordance with the requirements of the second oil passage side.

The present invention provides a hydraulic circuit control device mounted in a drive device of a vehicle including wheels; a first electric motor that has a coil and a cooling portion and drives the wheels; a power transmission device that has a lubricating portion and transmits the drive power of the first electric motor to the wheels; and a hydraulic clutch mounted in the power transmission device that performs engagement and disengagement of drive power between the first electric motor and the wheels, the control device including: a first oil passage that requires a high pressure and is connected to the hydraulic clutch; a second oil passage that requires a low pressure and high flow rate and is connected to at least one of the cooling portion and the lubricating portion; an oil pump that is driven by a second electric motor and that selectively supplies oil to the first oil passage and the second oil passage; an oil passage switching unit adapted to switch the connection of the oil pump to either the first oil passage or the second oil passage; a control mode switching unit adapted to switch the control mode of the second electric motor to either a torque control mode or a speed control mode; an oil passage selecting unit adapted to select whether to connect the oil pump to either the first oil passage or the second oil passage; and a control unit adapted to perform control so that the control mode switching unit switches the control mode of the second electric motor to the torque control mode when the oil passage selecting unit has selected the first oil passage, and to perform control so that the control mode switching unit switches the control mode of the second electric motor to the speed control mode when the oil passage selecting unit has selected the second oil passage.

When the hydraulic clutch is performing an engagement or disengagement operation, large fluctuations in the hydraulic load occur. However, when supplying oil to the clutch side, since the second electric motor is controlled in the torque control mode, the second electric motor is hardly affected by the hydraulic load. When supplying oil to the cooling portion of the first electric motor or the lubricating portion of the power transmission system, since the second electric motor is controlled in the speed control mode, overspeed of the second electric motor is prevented.

The hydraulic circuit control device of the present invention may further include a drain passage connected to the second oil passage, and a relief valve adapted to discharge oil in the second oil passage to the drain passage when a pressure of the second oil passage is equal to or greater than a first predetermined value.

In this case, when the viscosity of the oil increases at low temperatures, causing the pressure in the second oil passage to be equal to or greater than the first predetermined value, the relief valve discharges the oil in the second oil passage to the drain passage. Because of this, when the second electric motor is operating in speed control mode, an excessive load caused by the change in viscosity of the oil no longer acts on the second electric motor. Therefore, the energy efficiency of the second electric motor can be raised and step loss can be prevented in the second electric motor that is speed controlled.

In the hydraulic circuit control device of the present invention, the second oil passage may have an upstream portion and a downstream portion that has a cooling oil passage that connects to the cooling portion and a lubricating oil passage that connects to the lubricating portion, with an orifice provided in the lubricating oil passage, and a pressure regulating valve provided in the cooling oil passage and adapted to make oil flow into the cooling portion when the pressure of the upstream portion is equal to or greater than a second predetermined value.

In this case, when oil discharged from the oil pump is supplied to the second oil passage side, a pressure differential occurs upstream and downstream the orifice in the lubricating oil passage, so that the pressure gradually rises at the side of the branch portion before the orifice. When the pressure at the branch portion side rises to be equal to or greater than the second predetermined value, the pressure regulating valve opens. Oil then is supplied from the branch portion side to the cooling portion of the first electric motor, and the pressure of the oil supplied to the lubricating portion is limited to lower than the second predetermined value.

The hydraulic circuit control device of the present invention may further include a spray unit provided in the cooling portion, being adapted to discharge oil introduced through the cooling oil passage onto the coil.

In this case, when oil is supplied to the cooling oil passage, the oil is directly sprayed onto the coil of the first electric motor via a spray mechanism. Accordingly, oil uniformly and forcefully falls on the entire coil of the first electric motor, with the sprayed oil penetrating to the interior so that the entire coil can be efficiently cooled by the oil.

The relief valve and the pressure regulating valve may be integrally formed.

In this case, when the pressure at the branch portion side rises to the second predetermined value as oil discharged from the oil pump is supplied to the second oil passage side, the valve body opens the cooling oil passage to supply oil to the cooling portion of the first electric motor, with the supply pressure on the lubricating oil passage side then decreasing. When the pressure at the branch portion side rises to be equal to or greater than the first predetermined value, the valve body opens the drain passage to discharge oil in the second oil passage, and so thereby the pressure in the second oil passage is held lower than the first predetermined value. Accordingly, limiting the pressure of the lubricating oil passage under ordinary use conditions and relief of the oil when the oil viscosity rises can be performed by a single valve body. This can lower manufacturing costs and reduce the weight and size of the apparatus.

According to this invention, when supplying oil to the first oil passage that requires a high pressure, the second electric motor is controlled in the torque control mode, and when oil is supplied to the second oil passage that requires a low pressure and high flow rate, the second electric motor is controlled in a speed control mode. Therefore, a common oil pump can be effectively used without causing problems such as step out of the second electric motor and increased power consumption of the second electric motor.

DETAILED DESCRIPTION OF THE INVENTION

The embodiment of the present invention is described below with reference to the accompanying drawings. This embodiment applies the hydraulic circuit control device according to the present invention to a hydraulic system provided in a drive device1for auxiliary drive use in a vehicle3shown inFIG. 2.

The entire constitution of the vehicle shown inFIG. 2and the drive device1shown inFIGS. 3 and 4shall initially be described. The vehicle3shown inFIG. 2is a hybrid vehicle having a drive unit6in which an internal combustion engine4and an electric motor5are connected in series. The drive power of the drive unit6is transmitted to front wheels Wf via a transmission7, and the drive power of a drive device1for auxiliary driving provided separate to the drive unit6is transmitted to rear wheels Wr. The drive device1is driven by an electric motor2(wheel driving electric motor). The electric motor5of the drive unit6and the electric motor2of the rear wheel Wr-side drive device1are connected to a power drive unit (PDU)8via a battery9. Power supply from the battery9and energy regeneration from the electric motors5and2to the battery9is performed via the PDU8.

FIG. 3shows the entire longitudinal sectional view of the drive device1, with10A and10B in the drawing denoting the left and right axles of the rear wheels of the vehicle. A housing11of the drive device1is provided so as to cover the periphery from approximately the intermediate position between both axles10A and10B to the axle10B side, being supported and fixed to the bottom of the vehicle3as well as to the axle10B (seeFIG. 2). Also, the entire housing11is formed to be approximately cylindrical, with the wheel driving electric motor2, a planetary gear reducer12that reduces the rotational speed of the electric motor2, and a differential13that distributes the power of the reducer12to the left and right axles10A and10B arranged to be coaxially housed therein.

In the present embodiment, the planetary gear reducer12and the differential13constitute the power transmission device in the drive device1.

A stator14of the electric motor2is fixedly disposed to the wheel-side end inner periphery of the housing11(right side inFIG. 3). An annular rotor15is disposed to be rotatably arranged on the inner periphery side of the stator14. A cylinder shaft16that encloses the outer periphery of the axle10B is coupled to the inner periphery portion of the rotor15. This cylinder shaft16is supported by an edge wall17and an intermediate wall18so as to be coaxial with the axle10B via a shaft bushing19. Also, a resolver20is provided between the outer periphery of one side of the cylinder shaft16and the edge wall17of the housing11to feed back rotation information of the rotor15to a controller (not illustrated) for control of the electric motor2.

The planetary gear reducer12is provided with a sun gear21, a plurality of planetary gears22that mesh with the sun gear21, a planetary carrier23that supports the planetary gears22, and a ring gear24that is meshed with the outer periphery of the planetary gears22. The drive power of the electric motor2is input from the sun gear21, and the reduced drive power is output through the planetary carrier23.

The sun gear21is integrally formed with the outer periphery of a sleeve25disposed coaxially with the outer periphery side of the axle10B. One end side of the sleeve25is coupled in an integrally rotatable manner to the cylinder shaft16of the electric motor2side. Each the planetary gear22has a large-diameter first gear26that is directly meshed with the sun gear21and a second gear27with a diameter smaller than that of the first gear26. Each first gear26and each second gear27are integrally formed coaxially and in a state of being offset in the axial direction. The ring gear24is rotatably disposed in a side position of the first gear26in the axial direction, with its inner periphery side meshed with the small-diameter second gear27. The ring gear24is held in an integrally rotatable manner by a rotating drum29of a hydraulic clutch28that is described below, and rotatably supported in the housing11via this rotating drum29.

The differential13is provided with a differential case31in which a rotatable pinion30is installed in a protruding manner in the interior, and a pair of side gears32aand32bthat mesh with the pinion30in the differential case31. These side gears32aand32bare separately coupled to the left and right axles10A and10B. On the outer surface of the differential case31, the planetary carrier23of the planetary gear reducer12is integrally provided in an extending manner. The differential case31is supported by an edge wall34at the chassis center side of the housing11and the intermediate wall18via a bushing33.

A cylindrical space is secured between the ring gear24and the edge wall34in the housing11, and the hydraulic clutch28is disposed in that space. In the hydraulic clutch28, a plurality of fixed plates35that are spline fitted to the inner periphery surface of the housing11and a plurality of rotating plates36that are spline fitted to the outer periphery surface of one end of the rotating drum29are alternately arranged in the axial direction. Pressure contact and release of the fixed plates35and the rotating plates36are operated by an annular piston37. The piston37is housed to freely advance and retract in the annular cylinder chamber38formed at the edge wall34of the housing11. Feeding high-pressure oil into the cylinder chamber causes the piston37to advance, and discharging oil from the cylinder chamber38causes the piston37to retract. The hydraulic clutch28is connected to a hydraulic circuit39shown inFIG. 1, with this hydraulic circuit to be described in detail later.

In this hydraulic clutch28, the fixed plates35lock rotation in the housing11, and the rotating plates36integrally support the ring gear24. As a result, when both the fixed plates35and the rotating plates36are pressure contacted by the piston37, braking force is applied to the ring gear24by the friction engagement between the plates35and36. When the pressure contact by the piston37is released, free rotation of the ring gear24is again permitted.

On the exterior of the wheel-side edge wall17of the housing11, an oil pump40for supplying oil to the hydraulic clutch28, the cooling portion of the electric motor2, and the lubricating portion (of the power transmission device) in the housing11; a pump driving electric motor41for driving the oil pump40; and an accumulator42that accumulates oil in a pressure-accumulated state at the stage prior to supplying it to the hydraulic clutch28are provided as shown inFIGS. 3 and 4. These are housed in a cover43as block-shaped and fixed along with the cover43to the edge wall17.

The pump driving electric motor41is a brushless motor that has an annular rotor44as shown close-up inFIG. 4. An annular stator45that is a size larger than the rotor44is fixed to the outer surface of the edge wall17via a bracket46. A sleeve47that is fixed to the inner periphery of the rotor44is supported by the edge wall17and the bracket46via a bushing48. The rotor44and the stator45in this state are coaxially disposed on the outer periphery side of the axle10B.

The oil pump40is an external gear pump, with a pair of gears49for pump operation disposed in parallel alignment on the outer periphery of the pump driving electric motor41. Rotation of the electric motor41is transmitted to one of the gears49of the oil pump40by a gear transmission mechanism50.

In the accumulator42, an annular chamber51that has depth in the axial direction is integrally formed along the edge of the inner periphery of the cover43. An annular piston52is housed to freely advance and retract in the annular chamber51, with the piston52biased by a spring53for accumulating pressure.

When driving the axles10A and10B on the rear wheel Wr side with the drive device1of the above constitution, by supplying the oil pressure of the oil pump40to the hydraulic clutch28, the clutch28is turned ON, and by effecting friction engagement of the fixed plates35and the rotating plates36, the ring gear24becomes fixed with respect to the housing11. When the ring gear24is thus fixed, the reducing ratio of the planetary gear reducer12is fixed, with drive power transmitted without loss between the sun gear21and the planetary carrier23. Accordingly, the drive power of the electric motor2at this time is lowered to the set reducing ratio by the planetary gear reducer12, and transmitted to the left and right axles10A and10B of the vehicle by means of the differential13.

When the rotation speed of the rear wheels Wr exceeds the rotation speed of the electric motor2such as when driving by the drive device1on a downslope and the like, by discharging the oil in the hydraulic clutch28, the clutch28is turned OFF, whereby braking of the ring gear24is released. When the ring gear24is thus free to rotate, the ring gear24rotates idly in the housing11in tandem with the rotation of the axles10A and10B, and as a result, the rotor15of the electric motor2is no longer forcibly rotated by the rotation force of the axles10A and10B.

Accordingly, the drive device1can prevent excess rotation of the electric motor2and generation of axle friction.

The hydraulic circuit39shown inFIG. 1shall now be described. The hydraulic circuit control device according to the present invention is implemented to the control system of this hydraulic circuit39.

In the hydraulic circuit39, oil discharged from the oil pump40is selectively switched to a clutch oil passage58and a low-pressure oil passage57through a pilot-operating valve55, which is a solenoid valve, and a selector valve56. The low-pressure oil passage57is continuous with a suitable position in the housing11for supplying oil to the cooling portion of the electric motor2and lubricating portions of the power transmission device such as the planetary gear reducer12and the differential13. A check valve61is set between the clutch oil passage58and the selector valve56to prevent reverse flow of oil from the clutch oil passage58to the selector valve56. A clutch operating valve59that consists of a solenoid valve is set in the clutch oil passage58, and a branched oil passage60that leads to the accumulator42is provided further upstream from than the clutch operating valve59. A pressure sensor62that monitors the pressure in the accumulator42is provided in the branched oil passage60, with detection signals from the pressure sensor62being fed to a controller110(ECU). The clutch oil passage58is an oil passage that requires a high pressure in order to engage and disengage the hydraulic clutch28, and so constitutes a first oil passage in the present invention. In addition, the low-pressure oil passage57is an oil passage that requires a low-pressure and high flow rate for cooling and lubrication purposes, and so constitutes a second oil passage in the present invention.

The pilot-operating valve55and the selector valve56in the hydraulic circuit39constitute an oil passage switching unit in the present invention.

The selector valve56is provided with a spool112that allows or blocks communication of a pump oil passage111, which connects the oil pump40and the check valve61, with respect to the low-pressure oil passage57, and a spring113that biases the spool112to the left inFIG. 1. The pressure of the pump oil passage111always acts on the end face of the spool112on the left side inFIG. 1via a back-pressure passage114, while the operating pressure produced by the pilot-operating valve55acts on the right-side end face of the spool112via a pilot passage115.

The pilot-operating valve55is a solenoid three-way valve that is controlled by the controller110. When power is supplied to the solenoid (i.e., when it is ON), the pump oil passage111is connected to the pilot passage115, which causes pressure of the pump oil passage111to act on the right-side end face of the spool112inFIG. 1. At this time, since the same pressure acts on the end faces of both sides of the spool112, the spool112moves to the left side in the drawing due to the force of the spring113. Thereby, the low-pressure oil passage57is cut off, so that the pump oil passage111is only connected to the clutch oil passage58. Also, when power is cut to the solenoid of the pilot-operating valve55(i.e., when it is OFF), simultaneously with cutting the connection between the pump oil passage111and the pilot passage115, the pilot passage115becomes connected to a drain port116, whereby the pressure acting on the right-side end face of the spool112is opened. At this time, the spool112moves to the right side due to the pressure of the pump oil passage111acting on the left-side end face of the spool112, making the pump oil passage111continuous with the low-pressure oil passage57.

Accordingly, connection of the clutch oil passage58and the low-pressure oil passage57to the oil pump40is controlled by ON/OFF operation of the pilot-operating valve55.

The clutch operating valve59is a solenoid three-way valve that is controlled by the controller110similarly to the pilot-operating valve55. When power is supplied to the solenoid, the branched oil passage60that leads to the accumulator42is connected to the hydraulic clutch28and the hydraulic clutch28is engaged. When power is cut to the solenoid, the connection of the hydraulic clutch28with the branched oil passage60side is cut off, and the hydraulic clutch28becomes connected to a drain port117, whereby engagement of the hydraulic clutch28is released.

Also, the pump driving electric motor41that drives the oil pump40receives power from the battery9(seeFIG. 2) via the PDU8(seeFIG. 2), and is drive-controlled by the controller110via a motor driver circuit118.

The controller110commences driving of the pump driving electric motor41upon receiving a command from a main controller of the vehicle that is not illustrated. It controls the pilot-operating valve55and the pump driving electric motor41so that the pressure Poil in the accumulator42is maintained within a definite pressure range (AL≦Poil≦AH) in which engagement and disengagement of the hydraulic clutch28is possible. Three operation modes for the pump driving electric motor41, namely, Hi mode, Low mode, and Ini mode, are provided in a motor driver circuit118, with the mode changed in accordance with a mode switching command received from the controller110.

Each operation mode shall now be described in detail. The Hi mode is the mode used for when operating the oil pump40with a high pressure and low flow rate under normal driving conditions. The pump driving electric motor41is controlled by setting a torque value as the target value based on a current command issued from the controller110(torque control mode).

The Low mode is the mode used for when operating the oil pump40with a low pressure and high flow rate under normal driving conditions. The pump driving electric motor41is controlled by setting a speed value as the target value based on a rotation speed command issued from the controller110(speed control mode).

The Ini mode is the mode used for when operating the oil pump40with a greater current than during the Hi mode directly after starting the pump driving electric motor41. The pump driving electric motor41is torque controlled based on a current command issued from the controller110.

Accordingly, the controller110and the motor driver circuit118perform control of the pump driving electric motor41via torque control in the Hi mode or the Ini mode, and via speed control in the Low mode.

The controller110is provided with an oil passage selecting unit120that selects whether to supply oil discharged from the oil pump40to the clutch oil passage58or the low-pressure oil passage57; and a control unit121that controls the ON/OFF of the pilot-operating valve55and the control mode switching for the pump driving electric motor41in accordance with the selection result of the oil passage selecting unit120. In this embodiment, the oil passage selecting unit120receives a pressure signal from the pressure sensor62in the branched oil passage60and, based on that signal, selects an oil passage that supplies oil.

Specifically, the controller110constantly monitors the pressure Poil in the accumulator42via the signal from the pressure sensor62. The oil passage selecting unit120selects the clutch oil passage58when the pressure Poil is under the lower limit pressure AL and selects the low-pressure oil passage57when the pressure Poil exceeds the upper limit pressure AH. When the oil passage selecting unit120has selected the clutch oil passage58, the pilot-operating valve55is turned ON, the pump oil passage111is connected to only the clutch oil passage58, and the control mode of the pump driving electric motor41is switched to the Hi mode, which is the torque-control mode. When the oil passage selecting unit120has selected the low-pressure oil passage57, the pilot-operating valve55is turned OFF, the pump oil passage111is connected to the low-pressure oil passage57and the control mode of the pump driving electric motor41is switched to the Low mode, which is the speed-control mode.

A speed sensor122and an oil temperature sensor123are connected to the input side of the controller110. In the state of the control mode being set to the Low mode, and the hydraulic clutch28having stopped power transmission (that is, when in two-wheel drive mode), the controller110determines whether to stop operation of the pump driving electric motor41based on output signals from these sensors122and123. Under these conditions, when the vehicle speed is lower than a set vehicle speed V1and the oil temperature is less than a set temperature T1, the controller110stops operation of the pump driving electric motor41.

Control performed by the controller110shall be described below with reference to the flowcharts inFIGS. 6 and 7.

In step S101, a detection signal is received from the pressure sensor62, and the pressure Poil of the accumulator42is detected. Next, in step S102, it is confirmed that the startup completion signal (the signal that enables the transition to the ordinary control mode) is input from the motor driver circuit118. When the input of the startup completion signal is confirmed, the processing proceeds to step S103, and when it has not been input, the processing proceeds to step S108, where the operation mode of the pump driving electric motor41is set to the Ini mode.

In step S103, it is determined whether the pressure Poil of the accumulator42has exceeded the upper limit pressure AH. When it has exceeded the upper limit pressure AH, the processing proceeds to step S104, where the operation mode of the pump driving electric motor41is set to the Low mode. When the pressure Poil of the accumulator42has not exceeded the upper limit pressure AH, the processing proceeds to step S105, where it is determined whether the pressure Poil of the accumulator42is below the lower limit pressure AL. When the pressure Poil is below the lower limit pressure AL, the processing proceeds to step S106, where the operation mode of the pump driving electric motor41is set to the Hi mode. When the pressure Poil of the accumulator42is not below the lower limit pressure AL, the processing proceeds to step S107, and the operation mode is set to the same mode as the current mode.

When the processing proceeds to any of steps S104, S106, S107, and S108, it always next proceeds to step S109. In the subsequent steps, various different controls are executed in accordance with the operation mode set in the previous state and other vehicle conditions.

In step S109, it is determined whether the set operation mode is the Hi mode. In the case of being the Hi mode, the processing proceeds to step S110, and in the case of not being the Hi mode, the processing proceeds to step S112. In step S110, without regard to whether connection of the hydraulic clutch28is performed, since the operation mode is in the Hi mode, which requires the supply of high pressure oil to the accumulator42, the control of the pump driving electric motor41is set to torque control. In step S111, the current command of the pump driving electric motor41is set to the current Ih in accordance with the electric motor load pressure, and by turning on the pilot-operating valve55the oil emitted from the oil pump40is supplied to the clutch oil passage58(accumulator42).

When proceeding from steps S109to S112, it is determined whether the set operation mode is the Low mode. In the case of the Low mode, the processing proceeds to step S113, and if not the Low mode the processing proceeds to step S119. In the event of proceeding to step S119, since the operation mode is the Ini mode, after the control of the pump driving electric motor41is set to torque control, in step S120the current command of the pump driving electric motor41is set to startup current I1and the pilot-operating valve55is turned OFF.

In step S113, it is determined whether the clutch operating valve59is ON. If it is ON, the processing proceeds to step S114, and if it is OFF, the processing proceeds to step S116. When the processing proceeds to step S114, since the hydraulic clutch28is engaged in the Low mode in the state of the pressure of the accumulator42being in the set pressure range, the control of the pump driving electric motor41is set to speed control. In step S115, the rotation number command for the pump driving electric motor41is set to Np1and the pilot-operating valve55is turned OFF.

When the processing proceeds to step S116in the state of the clutch operating valve59being OFF, it is determined whether the current vehicle speed Vcar is less than a set vehicle speed V1. When equal to or greater than the set vehicle speed V1, the processing proceeds to step S114, similarly to when the hydraulic clutch28is engaged, and the control of the pump driving electric motor41is set to speed control. Also, when the vehicle speed Vcar is less than the set vehicle speed V1, the processing proceeds to step S117, where it is determined whether the current oil temperature Toil is less than a set oil temperature T1. When the oil temperature Toil at this time is equal to or greater than the set oil temperature T1, the processing proceeds to S114, similarly to when the hydraulic clutch28is engaged, and the control of the pump driving electric motor41is set to speed control.

When the oil temperature Toil is less than the set oil temperature T1, the processing proceeds to S118, where the pump driving electric motor41is turned OFF and the pilot-operating valve55is turned OFF. That is, when the processing proceeds to step S118, when in Low mode and the clutch operating valve59is OFF, since both the vehicle speed Vcar and the oil temperature Toil are sufficiently low, it is determined that there is no need to supply oil to the clutch oil passage58or the low-pressure oil passage57, and operation of the oil pump40is stopped.

The flow of control is as described above, but the operation during actual driving is as presented in the timing chart ofFIG. 8. This timing chart is explained below.

InFIG. 8, symbol (a) denotes the state of the pump driving electric motor41in a stopped condition. When the pressure of the actuator42is lower than the lower limit pressure AL at time (b) of startup, the controller110instructs a current according to the electric motor (EOP) load pressure PH, and the pump driving electric motor41is started by torque control. Then, the pilot-operating valve55is turned ON and high-load operation is performed in time period (c) until the pressure of the accumulator42reaches the upper limit pressure AH.

At time (d), when the pressure of the accumulator42reaches the upper limit pressure AH, by turning off the pilot-operating valve55, the oil passage connected to the oil pump40is switched to the low-pressure oil passage57of the low-load side. At this time, the controller110instructs the electric motor (EOP) rotation number (Np1), and the pump driving electric motor41is operated by rotation speed control. In addition, at time (d), the clutch operating valve59is ON and the vehicle switches to four-wheel-drive mode. In time period (e), low-load operation is performed with the pilot-operating valve55turned off until the pressure in the accumulator42reaches the lower limit pressure AL.

At time (f), when the pressure of the accumulator42reaches the lower limit pressure AL, the pilot-operating valve55is turned on and the oil passage connected to the oil pump40is switched to the clutch oil passage58on the high-load side. The controller instructs a current according to the electric motor (EOP) load pressure PH and runs the pump driving electric motor41in torque control. From this time on in time period (g), high load operation is performed with the pilot-operation valve55turned on until the pressure of the accumulator42reaches the upper limit pressure AH.

When the pressure of the accumulator42again reaches the upper limit pressure AH at time (h), by turning off the pilot-operation valve55, the oil passage connected to the oil pump40is switched to the low-pressure oil passage57similarly to at time (d), and the controller110instructs the electric motor (EOP) rotation number (Np1) and runs the pump driving electric motor41in rotation speed control.

At time (i), the clutch operating valve59switches off, and the vehicle changes to two-wheel-drive mode.

At this time, since the pressure of the accumulator42is in a definite range between the lower limit pressure AL and the upper limit pressure AH, the oil temperature Toil is lower than T1, and the vehicle speed Vcar is equal to or greater than V1, the pump driving electric motor41maintains its operation condition without stopping. That is, since lubrication of the power transmission device is required with a high vehicle speed Vcar, the running of the pump driving electric motor41is continued. At time (j), when the vehicle speed Vcar falls below V1, even if the supply of oil is stopped to the low-pressure oil passage57, it is determined that there is no lubrication or cooling problem, and the pump driving electric motor41is stopped.

FIG. 9shows a timing chart under another driving condition.

The driving condition in the first half of this timing chart resembles that ofFIG. 8, but the driving condition of the latter half, particularly from time (i) to time (j), partially differs.

Namely, at time (i), the clutch operating valve59is turned off and the vehicle switches to two-wheel-drive mode. The pressure of the accumulator42is in a set pressure range between the lower limit pressure AL and the upper limit pressure AH, and the vehicle speed Vcar is slower than V1, but since the oil temperature Toil is equal to or greater than T1, the pump driving electric motor41maintains its operating condition without stopping. That is, in this case, since it is necessary to continue cooling of the wheel driving electric motor2because the oil temperature Toil is high, running of the pump driving electric motor41is continued. When the oil temperature Toil subsequently falls below T1at time (i), even if the supply of oil is stopped to the low-pressure oil passage57, it is determined that there is no lubrication or cooling problem, and the pump driving electric motor41is stopped.

Next, the low-pressure oil passage57of the oil pressure circuit39shown inFIG. 1shall be explained in detail below.

In the low-pressure oil passage57, the upstream side oil passage57aconnected to the selector valve56branches into a lubricating oil passage70and a cooling oil passage71. The lubricating oil passage70supplies oil to the lubricating portions of the drive power transmission devices (the planetary gear reducer12and the differential13) as lubricating oil, while the cooling oil passage71supplies oil to the cooling portions (the regions requiring cooling) of the wheel driving electric motor2as cooling oil. In the lubricating oil passage70there is provided an orifice72, and in the cooling oil passage71there is a pressure regulating valve73that regulates and relieves the pressure within the low-pressure oil passage57in cooperation with the orifice72.

The lubricating oil passage70opens at a suitable position to be able to supply oil to the planetary gear reducer12and the differential13. The cooling oil passage71is connected to a stator cover74that encloses a stator coil14a(coil) of the electric motor2as shown inFIG. 10. This stator cover74is integrally provided with the housing11shown inFIG. 3, with an approximately semicircular oil filling chamber75formed in the upper half of the interior. The oil filling chamber75is connected to the cooling oil passage71via an introduction port76, and a plurality of small-diameter spray holes77are formed on the inner periphery of the oil filling chamber75whereby oil can be directly discharged onto the outer surface of the stator coil14a. The oil filling chamber75and the spray holes77formed in this stator cover74constitute a spray mechanism78that directly discharges oil onto the stator coil14a. Since the diameter of the spray holes77is small in the spray mechanism78, oil is not discharged from the spray holes77onto the stator coil14auntil the pressure in the oil filling chamber75reaches a specified pressure. At the point when the pressure in the oil filling chamber75has risen to or surpassed the specified pressure, oil is discharged onto the stator coil14ain small droplets.

In the pressure regulating valve73, a spool79that is a valve as shown inFIG. 11is slidably accommodated in a valve chamber80. The pressure in the lubricating oil passage70is adjusted by displacement of the spool79in accordance with pressure on a branched portion81of the lubricating oil passage70and the cooling oil passage71, and when the pressure of the branched portion81has risen to or above a set pressure, the oil inside is drained.

Specifically, in approximately the center position in the axial direction of the valve chamber80, an inlet port82connected to the branched portion81of the cooling oil passage71and an outlet port83connected to the cooling portion side of the electric motor2are offset in the axial direction. An operating pressure port84is provided on the end portion of the valve chamber80on the outlet port83side, and an air port85is provided on the other end portion of the valve chamber80on the inlet port82side, with a drain portion86provided between the outlet port83and the air port85. The operating pressure port84is connected to the branched portion81via a pressure induction passage87. An orifice88for restricting sensitive pressure fluctuations is provided in the pressure induction passage87. A spring89is interposed between the other end portion of the valve chamber80and the spool79, with the spool79being constantly biased to the one end side of the valve chamber80by the spring89. A first land portion90A, a second land portion90B, and a third land portion90C are formed spaced apart in the axial direction on the outer periphery of the spool79and sandwiching annular grooves91A and91B. In an initial state in which the pressure of the branched portion81is sufficiently low, as shown inFIG. 11the first and second land portions90A and90B of the spool79block communication between the outlet port83and the other ports84and82, and the second and third land portions90B and90C block communication between the inlet port82and the other ports83and84.

When pressure on the branched portion81side is introduced to the inlet port82and the operating pressure port84from the initial state shown inFIG. 11, the thrusts acting on the opposing surfaces of the second land portion90B and the third land portion90C, which have the same surface area, cancel each other out. The spool79then moves due to the balance of the rightward thrust inFIG. 11acting on the operating pressure port84and the reactive force of the spring89. In the pressure regulating valve73, when the pressure on the branched portion81side becomes a set pressure (second predetermined pressure), the inlet port82and the outlet port83mutually communicate due to the displacement of the second land portion90B, and oil is supplied from the branched portion81to the oil filling chamber75of the stator cover74through the cooling oil passage71. At this time, the amount of oil supplied to the lubricating oil passage70decreases, and the pressure of the lubricating oil passage70is restricted to be lower than the second predetermined pressure.

As the temperature decreases the oil viscosity rises, the oil resistance of the cooling oil passage71increases. When this occurs, oil is hindered from flowing from the inlet port82of the pressure regulating valve73to the outlet port83, and as a result, the pressure in the low-pressure oil passage57including the branched portion81gradually rises. When the pressure on the branched portion81side thus gradually rises, the thrust acting on the spool79via the operating pressure port84rises. When the pressure on the branched portion81side reaches a first predetermined pressure that is higher than the second predetermined pressure, the drain port86opens due to the displacement of the third land portion90C, and oil is discharged from the inlet port82to the drain port86, as shown inFIG. 12. Thereby, the pressure throughout the entire low-pressure oil passage57is inhibited from becoming higher than the first predetermined pressure.

In the discharge piping of the oil pump40, a high-pressure relief valve95is provided as shown inFIG. 1, and the pressure of the oil supplied to the clutch oil passage58thereby is restricted to a prescribed pressure or less. The second predetermined pressure is a lower pressure than the prescribed pressure of this high-pressure relief valve95.

As described above, when supplying oil to the clutch oil passage58that requires a high pressure, the control device of this hydraulic circuit (the control device that controls the hydraulic circuit39) controls the pump driving electric motor41by torque control. When supplying oil to the low-pressure oil passage57that requires a low pressure and high flow rate, the control device of this hydraulic circuit controls the pump driving electric motor41by speed control. Therefore, step out of the pump driving electric motor41due to large fluctuations in the hydraulic load accompanying operation of the hydraulic clutch28can be reliably prevented. Moreover, when sending oil at a low pressure and high flow rate through the low-pressure oil passage57, excessive power consumption due to overspeed of the pump driving electric motor41can be reduced.

The control device of the hydraulic circuit constantly monitors the pressure of the accumulator42side of the clutch oil passage58with the pressure sensor62. When the detected pressure in the accumulator42deviates from a set pressure range, the oil passage selecting unit120selects the clutch oil passage58. Therefore, it is always possible to achieve oil passage selection in accordance with the request of the clutch oil passage58and the optimum electric motor control mode based on that selection.

Moreover, in the control device of the hydraulic circuit, since the pressure regulating valve73with a relief function is interposed in the low-pressure oil passage57that sends oil for lubrication and cooling, even if the viscosity of oil rises at low temperatures, the spool79of the pressure regulating valve73can restrict the pressure of the low-pressure oil passage57to be less than the first predetermined pressure by opening the drain port86. Accordingly, in this device, when the pump driving electric motor41is running in speed control mode, overloads caused by fluctuations in the oil viscosity have no impact on the pump driving electric motor41. Therefore, the energy efficiency of the pump driving electric motor41can be raised, and step out of the speed-controlled pump driving electric motor41due to overloading can be prevented.

Since restricting the rotation speed of the pump to a specified rotation speed is particularly difficult in the case of operating the oil pump40by the sensor-less type pump driving electric motor41as in the present embodiment, the implementation of the pressure regulating valve73of the present invention is effective.

In the control device of this hydraulic circuit, with respect to the low-pressure oil passage57that branches into the lubricating oil passage70and the cooling oil passage71, since the orifice72is interposed in the lubricating oil passage70and the pressure regulating valve73is provided in the cooling oil passage71, the pressure of the oil supplied to the lubricating portion during normal operation can be kept lower than the second predetermined pressure by the pressure regulating valve73.

Since pressure adjustment of the lubricating oil passage70during normal usage and oil relief of the low-pressure oil passage57during abnormally high pressure can be performed by the single spool79of the pressure regulating valve73in the present embodiment, compared to the case of separately providing two types of valves, the manufacturing cost can be reduced and the weight and size of the device can be reduced.

The present invention is not limited to the aforementioned embodiment, and design modifications are possible without departing from the spirit or scope of the present invention. For example, the above embodiment applied the control device according to the present invention to the hydraulic circuit39that switches the oil passage for clutch control and the oil passage for cooling/lubrication in the drive device1for auxiliary drive use. However, the application of this invention is not limited to the drive device1, and is applicable to other devices provided they have a hydraulic circuit for switching of an oil passage that requires a high pressure and an oil passage that requires a low pressure and high flow rate.

In the embodiment described above, the oil passage selecting unit120in the controller110selects the oil passage based on the pressure of the clutch oil passage58, which is the first oil passage (that is, the pressure of the accumulator42). However, depending on the application use of the hydraulic circuit, selection of the oil passage may be performed based on the flow rate of the second oil passage that requires a low pressure and high flow rate.

In the embodiment described above, the oil temperature Toil is measured, and the temperature of the wheel driving electric motor2is indirectly determined from the oil temperature Toil. However, a temperature sensor may be installed in the wheel driving electric motor2to directly measure the temperature of the wheel driving electric motor2, or the temperature of the wheel driving electric motor2may be estimated from the electric current passing through the wheel driving electric motor2.