JPH05104971A - Vehicle driving device - Google Patents

Abstract

PURPOSE:To provide a practical vehicle driving device for driving respective wheels in a vehicle which achieves separate control of drive force and high control functions in controlling while preventing deterioration of comfortableness or increase of a fuel consumption ratio. CONSTITUTION:For a vehicle driving device equipped with a motor 1, and power transmission mechanisms to transmit a power generated by the motor 1 to wheels as a rotation force, four wheels 4a, 4b, 5a, 5b are provided, two wheels 4a, 4b of the four wheels are driven to rotate by the power directly transmitted from the motor 1 through the power transmission mechanisms 2, 3, 11, 12, and the other two wheels 5a, 5b are driven to rotate under the optimum separate control by a hydraulic motor 8, a direction control valve 7a, and a pressure control valve using the motor 1 for a power source.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle drive device for rotating and driving each wheel in a vehicle having at least four wheels.

[0002]

2. Description of the Related Art In recent years, four-wheel drive vehicles (hereinafter referred to as 4WD) have been increasingly adopted as passenger cars as the applications of vehicles have diversified.

The conventional 4WD has a power transmission device for transmitting the power generated by the engine to the front, rear, left and right wheels. This power transmission device is composed of a clutch, a transmission, a propeller shaft, a differential, an axle shaft, and the like. By this power transmission device, each wheel is mechanically connected to the engine,
Each wheel is rotationally driven by the power generated by the engine. When driving force is applied to the front, rear, left and right wheels in this way,
Improves running stability and running performance on low friction roads and roads with high running resistance.

On the other hand, however, when the power transmission device as described above is used, the installation of the power transmission device narrows the passenger compartment to deteriorate the habitability, and the increase in the vehicle weight causes the fuel consumption rate to increase. Occur.

In order to solve this problem, for example, Japanese Patent Laid-Open Publication No. 53-128828 proposes a vehicle drive device that converts the power generated by an engine into hydraulic pressure and rotationally drives the wheels with this high-pressure oil. There is.

[0006]

In the above vehicle drive device, since all wheels are rotationally driven by the high pressure oil, the drive force required for the vehicle to travel (traveling drive force) is changed by the high pressure oil. Must be secured. For this reason, a pump that generates high-pressure oil needs to have a large size and a large capacity.

Independent high-pressure oil is supplied to each wheel, and a driving force is generated according to the flow rate. Therefore, in order to ensure the straight running stability and turning performance of the vehicle, it is necessary to control the flow rate of the high-pressure oil supplied to each wheel with extremely high precision according to the traveling state of the vehicle. This is because the traveling driving force itself is generated according to the flow rate of the high-pressure oil, so that if the flow rate of the high-pressure oil of the left and right wheels becomes unbalanced, the straight running stability of the vehicle is impaired.

Considering the above points, the above-mentioned vehicle drive device is not practical and still has a problem to be solved. The present invention has been made in view of the above points, and it is an object of the present invention to provide a more practical vehicle drive device that drives each wheel of a vehicle while preventing deterioration of comfort and an increase in fuel consumption rate. It is intended.

[0009]

In order to achieve the above object, a vehicle drive apparatus according to the present invention uses a prime mover and the power generated by the prime mover via a main transmission to either the left front wheel or the right rear wheel. A power transmission mechanism that mechanically transmits to one of them, one pump that generates pressure fluid using the prime mover as a power source, and one of the left and right front wheels or the left and right rear wheels, which are the other left and right wheels. In a vehicle drive device including two hydraulic motors that respectively rotate the left and right wheels by the hydraulic liquid generated by the hydraulic pump, a connection path between the hydraulic pump and the two hydraulic motors. In addition, two pressure control valves respectively arranged in series with the two hydraulic motors, a detection means for detecting the occurrence of acceleration slip of the left and right wheels, and acceleration to either one of the left and right wheels. Slippery When There generated, characterized in that it comprises a control means for increasing control the control pressure of the pressure control valve of the wheel side acceleration slip has occurred.

[0010]

In the present invention, two hydraulic motors are provided corresponding to the two wheels to rotate and drive the two wheels by the hydraulic pressure generated by the hydraulic pump serving as the power source of the prime mover. Two pressure control valves are arranged in series with the motor. Here, when the acceleration slip occurs on one of the wheels, the control pressure on the wheel side where the acceleration slip occurs is increased by the pressure control valve. As a result, the load on the wheel side where the acceleration slip has occurred is increased, the driving force of the wheel is reduced by the pressure liquid supplied from the hydraulic pump, and the acceleration slip is suppressed, while the pressure liquid is applied to the other wheel side. Can be supplied.

Therefore, the driving force of the two wheels can be optimally and independently controlled by using the hydraulic motor, so that it is not necessary to provide a mechanical power transmission mechanism for the two wheels. Therefore, compared with a four-wheel drive vehicle in which all the wheels are driven via a mechanical power transmission mechanism, the vehicle weight can be reduced and the comfortability can be improved.

Further, the traveling driving force of the vehicle can be secured by two wheels mechanically connected to the prime mover via a power transmission mechanism as in the conventional case. Therefore, auxiliary driving force may be obtained from the wheels that are rotationally driven by the rotary motor. Therefore, it is possible to reduce the size of the rotary motor and to improve the straight running stability of the vehicle as compared with a vehicle drive device in which all wheels are driven to rotate by using high pressure oil.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram showing the configuration of the present invention. In FIG. 1, an engine 1 as a prime mover is connected to a propeller shaft 2 via a clutch 11 and a transmission 12. Propeller shaft 2
It is connected to the differential 3, and the differential 3 performs a decelerating action, a converting action and a differential action as is known. Then, by the action of this differential 3, the left and right rear wheels 4 are passed through the rear axle shaft.
The rotational driving force is transmitted to a and 4b.

A hydraulic pump 6 is connected to the engine 1 by a pulley and a belt. Therefore, the hydraulic pump 6 is driven by the engine 1, sucks hydraulic oil from the oil tank 9, and discharges hydraulic oil at a pressure and a flow rate according to the engine speed. The discharge port of the hydraulic pump 6 is connected to the control valve 7, and the pressure of the hydraulic oil discharged from the hydraulic pump 6 is adjusted by the control valve 7. The hydraulic oil regulated by the control valve 7 is supplied to the hydraulic motors 8a and 8a provided inside the left and right front wheels 5a and 5b.
b, and drives the hydraulic motors 8a and 8b. As a result, a rotational driving force is generated on the left and right front wheels 5a and 5b. The hydraulic oil supplied to the hydraulic motors 8a and 8b causes the left and right front wheels 5a and 5b to generate rotational driving force, and then is discharged to the oil tank 9 through the pressure control valves RV2 and RV3.

Wheel speed sensors 13a and 13b are attached to the left and right front wheels 5a and 5b.
A detection signal corresponding to the rotation speed of 5b is output. Wheel speed sensors 13c and 13d are attached to the rear axle shafts in order to detect the rotational speeds of the left and right rear wheels 4a and 4b.

In addition, as a sensor for detecting the running state of the vehicle, a vehicle speed sensor 14 for detecting the rotation speed of the propeller shaft 2 as the vehicle speed, and a steering wheel 10.
Steering angle sensor 15 that detects the steering angle of the vehicle, acceleration sensor 19 that detects the acceleration state of the vehicle, throttle sensor 20 that detects the opening of the throttle valve that adjusts the intake air amount of the engine 1, and shift position of the transmission 12 A shift position sensor 22, a brake sensor 21 for detecting the depression state of the brake pedal, and an idle switch 23 for outputting a signal when the engine speed reaches an idle speed.

The detection signals of these sensors are input to an electronic control unit (hereinafter referred to as ECU) 25, and the ECU 25
Drives the control valve 7 on the basis of these detection signals to generate an optimum driving force for the left and right front wheels 5a, 5b.

Next, the specific construction of the control valve 7 and its operation will be described with reference to FIG. As shown in FIG. 2, the control valve 7 includes a pressure control valve RV1, a direction switching valve 7a, pressure control valves RV2, RV3, and a check valve 7b.
7c.

The pressure control valve RV1 is arranged between the discharge side of the hydraulic pump 6 and the oil tank 9, and the ECU 2
The discharge pressure of the hydraulic pump 6 is controlled according to a control signal output from the hydraulic pump 5.

The direction switching valve 7a is arranged between the hydraulic pump 6 and the hydraulic motors 8a and 8b, and whether or not hydraulic oil is supplied from the hydraulic pump 6 to the hydraulic motors 8a and 8b and to the hydraulic motors 8a and 8b. The flow direction of the working oil is switched. That is, when the vehicle is stopped or the driver is operating the brake pedal, it is not necessary to generate a driving force on the left and right front wheels 5a and 5b. Therefore, the direction switching valve 7a is switched to the B position,
The hydraulic pump 6 and the oil tank 9 are communicated with each other to rotate the hydraulic pump 6 in an unloaded state. When the vehicle is moving forward and the brake pedal is not operated, the directional control valve 7a is switched to the A position. As a result, hydraulic oil flows in the direction in which the left and right front wheels 5a, 5b are rotationally driven in the forward rotation direction through the hydraulic motors 8a, 8b. On the other hand, when the vehicle moves backward, the directional control valve 7a is switched to the C position. As a result, when the vehicle moves backward, the flow direction of the hydraulic oil is reversed from that when the vehicle moves forward, and the left and right front wheels 5a, 5b are rotationally driven in the reverse rotation direction.

The pressure control valves RV2, RV3 are provided between the hydraulic motors 8a, 8b and the oil tank 9 and are hydraulic motors 8a, 8b.
b is arranged in series, and when an acceleration slip occurs on any of the wheels of the vehicle, in order to suppress the acceleration slip,
The power supplied to the hydraulic motors 8a and 8b is controlled. For example, when the rotational speed MFL of the left front wheel 5a is higher than the rotational speed MFR of the right front wheel 5b during straight running of the vehicle, it can be determined that the left front wheel 5a has an acceleration slip. In this case, since the load of the hydraulic motor 8a on the hydraulic pump 6 is smaller than that of the hydraulic motor 8b, most of the hydraulic oil discharged from the hydraulic pump 6 flows through the hydraulic motor 8a. Then, hydraulic oil is not supplied to the hydraulic motor 8b, and it becomes impossible to drive the right front wheel 5b. Therefore, as described above, when the acceleration slip occurs on the left front wheel 5a, the pressure control valve RV2 on the left front wheel side is activated to increase the load on the left front wheel side. As a result, the power to be supplied to the hydraulic motor 8a can be reduced and the power to the hydraulic motor 8b can be supplied, so that the left and right front wheels 5a, 5b can be rotationally driven with an appropriate driving force.

The check valves 7b and 7c are pressure control valves RV in order to secure a flow path for hydraulic oil when the vehicle moves backward.
2 and RV3 are arranged in parallel. Further, the pressure control valves RV1, RV2, RV3 are provided with a fail-safe mechanism that mechanically reduces the control pressure when the control pressure becomes equal to or higher than a predetermined pressure.

Next, how the ECU 25 drives the control valve 7 based on the detection signals of various sensors will be described with reference to the flowchart of FIG. Figure 3
In step 100, the shift position sensor 22
The shift position of the transmission 12 is determined based on the detection signal of. It should be noted that the present embodiment is intended for a vehicle equipped with an automatic transmission, and the shift positions are a neutral range (N range) and a drive range (D range).
And a reverse range (R range). When it is determined in step 100 that the shift position of the transmission 12 is in the N range, step 1
In step 20, the directional control valve 7a is switched to the B position. As a result, the hydraulic pump 6 communicates with the oil tank 9 and is driven in an unloaded state, so that no driving force is generated on the left and right front wheels 5a, 5b.

When it is determined in step 100 that the shift position of the transmission 12 is in the D range, the process proceeds to step 110. In step 110, it is determined based on the detection signal of the brake sensor 21 whether the driver is operating the brake pedal.
When the brake pedal is being operated, it is not necessary to generate a driving force on the left and right front wheels 5a, 5b, so the routine proceeds to step 120, where the direction switching valve 7a is switched to the B position. On the other hand, when the brake pedal is not operated, the routine proceeds to step 130, where the direction switching valve 7a is switched to the A position. This makes it possible to supply hydraulic oil to the hydraulic motors 8a and 8b, which drives the hydraulic motors 8a and 8b in the forward rotation direction.

In step 140, the idle switch 2
Based on the detection signal of No. 3, it is determined whether the rotation speed of the engine 1 is the idle rotation speed or higher. When it can be considered that the rotation speed of the engine 1 is substantially the idle rotation speed, the left and right front wheels 5a and 5b do not require so much driving force. Therefore, step 17
In step 0, the pressure control valve RV1 is controlled so that the discharge pressure of the hydraulic pump 6 becomes low. On the other hand, when the engine speed is higher than the idle speed, step 15
0, based on the detection signal of the throttle sensor 20,
Determine if the accelerator pedal is depressed.
If it is determined that the accelerator pedal is not depressed,
Proceeding to step 160, the pressure control valves RV2, RV are supplied so that medium to high pressure hydraulic oil is supplied to the hydraulic motors 8a, 8b.
Control 3 In other words, it is considered that when the rotation speed of the engine 1 is higher than the idle rotation speed and the accelerator pedal is not depressed, the driver is slowly reducing the vehicle speed by engine braking.

At this time, the hydraulic motors 8a and 8b are rotationally driven by the left and right front wheels, function as hydraulic pumps, and the pressure control valves RV2 and RV3 on the downstream side act as loads to generate braking force. Therefore, in this embodiment, the pressure control valve RV
2 and RV3 are set to a high load so that the engine brake works more effectively.

Further, since the pressure control valves RV2, RV3 are provided on the downstream side of the hydraulic motors 8a, 8b, they do not become a resistance when the hydraulic motors 8a, 8b suck in hydraulic oil. Therefore, the hydraulic motors 8a and 8b can suck a necessary amount of hydraulic oil, and noise such as cavitation on the suction side and necessity of durability do not pose a problem.

When it is judged at step 150 that the accelerator pedal is depressed, the routine proceeds to step 180, at an angle where the steering angle of the steering wheel 10 can be regarded as substantially zero based on the detection signal of the steering angle sensor 15. It is determined whether there is any. If it is determined that the steering angle is not substantially zero, it means that the vehicle is turning,
Proceeding to step 190, the left and right front wheels 5 depending on the turning state.
Correct the rotation speeds of a and 5b. That is, when the vehicle is turning, the rotation speed of the turning outer wheel is higher than the rotation speed of the turning inner wheel. Therefore, based on the vehicle turning radius estimated from the steering angle, one of the left and right front wheels 5a and 5b is multiplied by a correction coefficient so that the left and right front wheels 5a and 5b have the same rotation number.

When it is determined in step 180 that the steering angle is substantially zero, or when the rotational speed of one of the left and right front wheels 5a and 5b is corrected in step 190,
Go to step 200. In step 200, it is determined whether or not the rotation speeds of the left and right front wheels 5a and 5b can be regarded as substantially equal. When the rotational speeds of the left and right front wheels 5a and 5b are different, it is considered that an acceleration slip has occurred in one of the left and right front wheels 5a and 5b. For this reason, first step 21
At 0, the pressure control valve RV1 is controlled so that the discharge pressure of the hydraulic pump 6 becomes medium to high in order to increase the driving force of the wheel on the side where the acceleration slip has not occurred. afterwards,
In step 220, it is determined whether the rotational speed MFL of the left front wheel 5a is higher than the rotational speed MFR of the right front wheel 5b. The rotational speed MFL of the left front wheel 5a is the rotational speed M of the right front wheel 5b.
If it is lower than FR, it can be determined that an acceleration slip has occurred on the right front wheel 5b. In this case, step 230
Then, the control pressure of the pressure control valve RV2 on the left front wheel side is set to a low pressure state, and the control pressure of the pressure control valve RV3 on the right front wheel side is set to a medium to high pressure state. As a result, the load on the right front wheel side of the hydraulic pump 6 increases, so that the working oil easily flows to the left front wheel side. As a result, the power supplied to the hydraulic motor 8b of the right front wheel 5b in which the acceleration slip has occurred is decreased, and the power supplied to the hydraulic motor 8a of the left front wheel 5a is increased, which is optimal for the left and right front wheels 5a and 5b. Driving force can be supplied.

If it is determined in step 220 that the rotational speed MFL of the left front wheel 5a is higher than the rotational speed MFR of the right front wheel 5b, it is considered that an acceleration slip has occurred in the left front wheel 5a. Proceed to. Step 24
At 0, contrary to step 230, the control pressure of the left front wheel side pressure control valve RV2 is set to the middle to high pressure state, and the control pressure of the right front wheel side pressure control valve RV3 is set to the low pressure state. As a result, the power supplied to the hydraulic motor 8b of the right front wheel 5b is increased and the power supplied to the hydraulic motor 8a of the left front wheel 5a is reduced, so that the acceleration slip of the left front wheel 5a can be eliminated.

In step 200, the left and right front wheels 5a, 5b
If it is determined that the rotation speeds of the
In step 50, it is determined whether or not there is a difference in the number of rotations between the average value of the number of rotations of the left and right front wheels 5a, 5b and the average value of the number of rotations of the left and right rear wheels 4a, 4b. (However, when the vehicle is turning, the rotational speeds of the left and right rear wheels 4a, 4b are corrected in the same manner as the rotational speeds of the left and right front wheels 5a, 5b.) In this case, a rotational speed difference has occurred. If so, it is considered that an acceleration slip has occurred in the left and right rear wheels 4a, 4b. Therefore, the routine proceeds to step 260, in order to improve the driving stability of the vehicle, in order to increase the driving force of the left and right front wheels 5a, 5b, the pressure control valve is adjusted so that the discharge pressure of the hydraulic pump 6 becomes medium to high pressure. Control RV1. On the other hand, when there is no difference in rotation speed between the front and rear wheels, step 270
Then, based on the detection signal of the acceleration sensor 19, it is determined whether the acceleration of the vehicle is larger than a predetermined value. When the acceleration of the vehicle is larger than a predetermined value,
In order to secure the traveling stability of the vehicle, the routine proceeds to step 260, where the driving force of the left and right front wheels 5a, 5b is increased.

When it is determined in step 270 that the vehicle acceleration is smaller than the predetermined value, the process proceeds to step 280. In this case, it is considered that the vehicle maintains a stable running state because no acceleration slip has occurred on all wheels of the vehicle and the change in speed is small. At this time, it is not necessary to supply such a large driving force to the left and right front wheels 5a and 5b. Therefore, in step 280,
The pressure control valve RV1 is controlled so that the discharge pressure of the hydraulic pump 6 is low to medium pressure, and the control pressure of the pressure control valves RV2, RV3 is set to a low pressure state.

When it is determined in step 100 that the shift position of the transmission 12 is in the R range, the process proceeds to step 290. In step 290,
The direction switching valve 7a is switched to the C position so that the hydraulic motors 8a and 8b rotate in the reverse rotation direction. As a result, the hydraulic oil discharged from the hydraulic pump 6 is supplied to the hydraulic motors 8a and 8b via the direction switching valve 7a and the check valves 7b and 7c.

In step 300, as in step 250, is there a difference in the number of rotations between the average value of the number of rotations of the left and right front wheels 5a, 5b and the average value of the number of rotations of the left and right rear wheels 4a, 4b? It is determined whether or not. At this time, if there is a difference in the number of revolutions, the routine proceeds to step 310, where the left and right front wheels 5a,
In order to increase the driving force of 5b, the pressure control valve RV1 is controlled so that the discharge pressure of the hydraulic pump 6 becomes medium to high pressure. On the other hand, when there is no difference in rotational speed between the front and rear wheels,
Proceeding to step 320, the pressure control valve RV1 is controlled so that the discharge pressure of the hydraulic pump 6 becomes low to medium pressure. When the shift position of the transmission 12 is in the R range, the control pressures of the pressure control valves RV2, RV3 are always in the low pressure state.

In the above embodiment, the left and right rear wheels 4a,
4b is mechanically driven by the engine 1 and the left and right front wheels 5
Although a and 5b were hydraulically driven, the same effect can be obtained even if the drive sources for the front and rear wheels are reversed.

Although the hydraulic pump 6 receives rotational power from the engine 1 via the pulley and the belt, the hydraulic pump may be rotationally driven by a gear or the like. Furthermore, FIG.
As shown in, the hydraulic pump 6 may be connected to the propeller shaft 2 via the gear 24 or the like and rotationally driven by the rotational force of the propeller shaft 2. In this case, the rotational speeds of the propeller shaft 2 and the rear wheels 4a and 4b are uniquely determined, so that the control of the control valve 7 becomes easy. further,
When the vehicle moves backward, the propeller shaft 2 also rotates in the opposite direction like the rear wheels 4a and 4b, so that the directional control valve can be omitted.

Further, the direction switching valve may be kept in the A position even when the brake is turned on when the driving / control torque of the rotary motor is not so large, and is switched to the B position when the rotary motor does not require a driving force even during forward traveling. You may keep it.

Further, the hydraulic motor 6 is not directly mounted on the front wheels 5a and 5b but is mounted on the vehicle body near the front wheels 5a and 5b or near the engine 1 to drive the hydraulic motor 6 and the front wheels 5a and 5b. You may connect via the shafts 26a and 26b. In this case, since the hydraulic motor 6 can be mounted on the spring of the vehicle suspension, maneuverability, riding comfort, fuel economy, etc. can be improved.

[0039]

As described above, according to the present invention, there are two hydraulic motors that rotate and drive two wheels by the hydraulic pressure generated by the hydraulic pump whose power source is the prime mover. Two pressure control valves are provided in series with each of the two hydraulic motors. As a result, it is possible to provide a practical vehicle drive device capable of optimally and independently controlling the driving forces of the two wheels while preventing deterioration of comfortability and increase in fuel consumption rate.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a hydraulic circuit diagram showing a configuration of a control valve.

FIG. 3 is a flowchart showing a control procedure of the electronic control unit.

FIG. 4 is a configuration diagram showing a configuration of another embodiment of the present invention.

FIG. 5 is a configuration diagram showing a configuration of another embodiment of the present invention.

[Explanation of symbols]

 1 Engine 2 Propeller Shaft 3 Differential Gear 4a, 4b Rear Wheel 5a, 5b Front Wheel 6 Hydraulic Pump 7 Control Valve 8a, 8b Hydraulic Motor 9 Oil Tank 11 Clutch 12 Transmission 25 Electronic Control Unit (ECU)

Claims (3)

[Claims] 1. A prime mover, a power transmission mechanism for mechanically transmitting the power generated by the prime mover to one of the left and right front wheels or the left and right rear wheels via a main transmission, and a pressure source using the prime mover as a power source. One pump to generate liquid,
For a vehicle provided with two hydraulic motors that are provided corresponding to the other left and right wheels of the left and right front wheels or the left and right rear wheels, and that respectively rotate the left and right wheels by hydraulic fluid generated by the hydraulic pump In the drive device, two pressure control valves, which are respectively arranged in series with the two hydraulic motors, are provided in a connection path between the hydraulic pump and the two hydraulic motors, and the left and right wheels are connected to each other. A detection means for detecting the occurrence of the acceleration slip, and a control means for increasing the control pressure of the pressure control valve on the wheel side where the acceleration slip occurs when the acceleration slip occurs on one of the left and right wheels. And a vehicle drive device. 2. The two pressure control valves, which are respectively arranged in series with respect to the two hydraulic motors, are provided on the downstream side of the two hydraulic motors. 1. The vehicle drive device according to 1. 3. A directional switching valve between the hydraulic pump and the two hydraulic motors for switching the direction of the hydraulic fluid supplied from the hydraulic pumps to the two hydraulic motors, The vehicle drive device according to claim 1, further comprising: a control unit that controls the directional control valve according to a shift position of the main transmission.