JPH09240300A - Four-wheel drive vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration in a fuel consumption of the whole vehicle accompanying increase of vehicle weight and the like because of installation of a fluid pressure transmitting mechanism. SOLUTION: When a vehicle travels with a fluid pressure transmitting mechanism controlled to a two-wheel drive condition, a 2/4 switching valve 21 is shut off during the actuation of a brake and a tilting angle of a swash plate 103 in a swash plate type variable capacity motor 10 is regulated to a minimum position, and an intake oil quantity to an intake throttle type piston pump 6 is regulated by means of an intake restricting proportional control valve 22 so that a working fluid pressure in a high pressure pipe 8H is controlled to a high pressure. Then, the working fluid pressure is accumulated in an accumulator 25 while an Acc outlet valve 26 is opened, and after the pressure accumulation is finished, an ordinary two-wheel driving condition is revived. When the brake is not actuated, the Acc outlet valve 26 is opened, and the working fluid pressure accumulated in the accumulator 25 is supplied to the swash plate type variable capacity motor 10, so that a driving force is supplied from the swash plate type variable capacity motor 10 to a driven wheel, and as a result, reduction of a fuel consumption can be suppressed by the driving force equivalent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a four-wheel drive vehicle in which a rotational driving force of a main engine is transmitted to front wheels and rear wheels, and particularly, the driving force is transmitted by a fluid pressure transmission mechanism. It relates to four-wheel drive vehicles.

[0002]

2. Description of the Related Art As a four-wheel drive vehicle of this kind, conventionally, for example, Japanese Patent Application No. 6-49146 and Japanese Patent Application No. 6-0491.
As described in Japanese Patent Application No. 48, Japanese Patent Application No. 6-55974, and the like, drive-side fluid pressure driving means that rotates in conjunction with the front wheels driven by the main engine and generates hydraulic pressure according to the rotational speed thereof. A fluid pressure transmission mechanism including a driven-side fluid pressure driving means that rotates in conjunction with the rear wheel and generates a hydraulic pressure according to the rotation speed of the driven wheel is provided. It has been proposed to realize a four-wheel drive state by causing the motor to generate a transmission torque according to the front-rear wheel rotation speed difference when the amount of fluid discharged from the motor as a fluid pressure drive means is exceeded. There is.

[0003]

However, in the above-mentioned conventional four-wheel drive vehicle, since the fluid pressure transmission mechanism is newly provided for driving the driven wheels with respect to the two-wheel drive vehicle, the entire vehicle is However, there is a problem that the weight increases. Further, the driving force on the driving side is transmitted to the driven side via the fluid pressure transmission mechanism in accordance with the difference in fluid amount between the driving side fluid pressure driving means and the driven side fluid pressure driving means. However, there is a problem that mechanical loss torque is generated, which causes deterioration of fuel consumption in the two-wheel drive state.

Therefore, the present invention has been made in view of the above-mentioned unsolved problems of the prior art. By collecting the working fluid pressure during braking in the fluid pressure transmission mechanism and regenerating it during non-braking, It is an object of the present invention to provide a four-wheel drive vehicle that can prevent a reduction in fuel consumption of the entire vehicle.

[0005]

In order to achieve the above-mentioned object, a four-wheel drive vehicle according to a first aspect of the present invention rotates in association with a drive axle driven by a prime mover and discharges a working fluid. A four-wheel drive vehicle comprising: a fluid pressure supply means having a pump; and a fluid pressure drive means having a fluid pressure motor which is interlocked with an axle of a driven wheel and which is supplied with a working fluid from the fluid pressure supply means to rotate. The working fluid pressure from the fluid pressure supplying means to the fluid pressure driving means is accumulated in the pressure accumulating means during braking, and the working fluid pressure of the pressure accumulating means is supplied to the fluid pressure driving means during non-braking. I am trying.

According to the first aspect of the present invention, the working fluid pressure from the fluid pressure supply means to the fluid pressure driving means is accumulated in the pressure accumulating means during braking, and the accumulated working fluid pressure during braking is equal to the fluid pressure during non-braking. By being supplied to the pressure drive means,
The working fluid pressure from the fluid pressure supply means at the time of braking is supplied to the fluid pressure drive means as a driving force at the time of non-braking, and the working fluid pressure from the fluid pressure supply means is effectively utilized to reduce the fuel consumption of the entire vehicle. To be prevented.

A four-wheel drive vehicle according to a second aspect of the present invention includes a fluid pressure supply means having a fluid pressure pump that rotates in conjunction with a drive axle driven by a main engine and discharges a working fluid, and a driven wheel. A four-wheel drive vehicle including a fluid pressure driving means having a fluid pressure motor that rotates in response to a working fluid supplied from the fluid pressure supplying means, the fluid pressure supplying means and the fluid pressure driving means being provided. A switching valve for switching between the high-pressure side pipe and the low-pressure side pipe to a shutoff state, a switching valve control means for controlling the switching valve to be in a communication state or a shutoff state according to the running state of the vehicle, and the high-pressure side pipe When the pressure accumulating means for accumulating the working fluid pressure and the switching valve are controlled to communicate with each other, the working fluid pressure to the fluid pressure driving means is accumulated in the pressure accumulating means at the time of braking and the pressure accumulating means of the pressure accumulating means at the time of non-braking. Working fluid pressure It is characterized by and a regeneration control means for supplying to the serial hydraulic drive means.

According to the second aspect of the present invention, the switching valve control means controls the switching valve to be in a communicating state in accordance with the traveling state of the vehicle, and the fluid pressure supply means and the fluid pressure driving means are shut off from each other. When the vehicle is running in the braking state, the working fluid pressure supplied from the fluid pressure supplying means to the fluid pressure driving means is accumulated in the pressure accumulating means when the vehicle is running in the braking state, and When running in the braking state,
By supplying the working fluid pressure at the time of braking accumulated in the pressure accumulating means to the fluid pressure driving means, the working fluid pressure at the time of braking is supplied to the fluid pressure driving means at the time of non-braking, which serves as a driving force for the driven wheels. Since it works, a reduction in fuel consumption of the entire vehicle is prevented.

Further, in the four-wheel drive vehicle according to claim 3, the pressure accumulator is an accumulator connected to a high pressure side pipe between the switching valve and the fluid pressure drive means, and the accumulator and the high pressure side pipe. And a check valve that allows only the flow from the fluid pressure supply means to the fluid pressure drive means, which is provided between the pressure accumulation switch valve and the switch valve, The regenerative control means controls the switching valve to be in a closed state during braking, controls the pressure accumulation switching valve to be in a communication state, and controls the pressure accumulation switching valve to be in a communication state in a non-braking state. .

According to the invention of claim 3, claim 2
In the invention of claim 1, an accumulator is provided in the high-pressure side pipe between the switching valve for shutting off the high-pressure side pipe and the low-pressure side pipe and the fluid pressure drive means via the pressure accumulation switching valve, and the switching with the pressure accumulation switching valve. A non-return valve is provided between the fluid pressure supply means and the fluid pressure drive means by putting the check valve in the closed state during braking and putting the pressure accumulation changeover valve in communication. At this time, the working fluid pressure of the high-pressure side pipe is accumulated in the accumulator via the pressure accumulation switching valve, the switching valve is controlled to be in a communication state, and the fluid pressure from the fluid pressure supply means is not supplied to the fluid pressure drive means. When the vehicle is running in the non-braking state, the working fluid pressure at the time of braking accumulated in the accumulator is supplied to the fluid pressure driving means by setting the pressure accumulation switching valve in the communicating state, and this working fluid pressure is subordinated. For driving wheels Act as a power.

A four-wheel drive vehicle according to a fourth aspect of the invention is provided with a rotation speed detecting means for detecting the rotation speeds of the front and rear wheels, and the switching valve control means is adapted to rotate the front and rear wheels detected by the rotation speed detecting means. When the ratio of numbers is less than the preset threshold,
It is characterized in that the switching valve is controlled to be in a communication state.

In the invention of claim 4, the rotation speed of the front and rear wheels is detected by the rotation speed detection means, and when the ratio of the rotation speeds of the front and rear wheels is smaller than a preset threshold value, the switching valve control means is Since the switching valve is controlled to be in the communication state,
When the rotation speed ratio of the front and rear wheels is smaller than the threshold value and the rotation speeds of the front and rear wheels are almost the same, the switching valve is controlled to be in the communicating state, the working fluid pressure is accumulated during braking, and non-braking is performed. Occasionally, the accumulated working fluid pressure is supplied to the fluid pressure drive means.

A four-wheel drive vehicle according to a fifth aspect of the present invention includes an intake oil amount limiting valve for limiting the amount of intake oil to the fluid pressure pump, and pressure detecting means for detecting the working fluid pressure of the pressure accumulating means. Braking state detection means for detecting a braking state of the vehicle; and the regenerative control means, when the working fluid pressure is accumulated, the intake oil is increased as the detected value of the pressure detection means approaches a preset maximum accumulated pressure value. It is characterized in that the amount of the intake oil is reduced as the amount of the oil is reduced and the detected value of the braking state detecting means increases.

According to the fifth aspect of the present invention, when the working fluid pressure is accumulated, as the working fluid pressure of the pressure accumulating means approaches the preset maximum accumulated pressure value based on the detection value of the pressure detecting means, the fluid pressure pump is stored. By reducing the amount of intake oil, the amount of fluid discharged from the fluid pressure pump is reduced, and similarly, the amount of fluid discharged from the fluid pressure pump decreases as the braking state of the vehicle increases based on the detection value of the braking state detection means. At the time when the working fluid pressure reaches the maximum accumulated pressure value and the accumulation of the working fluid pressure in the pressure accumulating means is completed, the pressure accumulation state is smoothly switched to the normal braking state.

The four-wheel drive vehicle according to a sixth aspect is characterized in that the braking state detecting means detects a stroke of the brake pedal. In the invention of claim 6, the braking state of the vehicle is the stroke of the brake pedal,
That is, since the amount of depression is detected, the braking state of the vehicle can be detected more easily and reliably.

The four-wheel drive vehicle according to a seventh aspect is characterized in that the fluid pressure motor is a fluid pressure motor whose maximum displacement can be varied. In the invention of claim 7, since the fluid pressure motor is a fluid pressure motor whose maximum displacement can be varied, the driving force generated by the fluid pressure motor can be varied by changing the maximum displacement. .

Further, a four-wheel drive vehicle according to an eighth aspect comprises pressure detection means for detecting a working fluid pressure of the pressure accumulating means and speed state detection means for detecting a traveling speed state of the vehicle, and the regenerative control is provided. Means supplies the working fluid pressure of the pressure accumulating means to the fluid pressure driving means, and decreases the maximum capacity as the detection value of the pressure detecting means approaches a preset minimum pressure accumulation value, and the speed state detecting means The maximum capacity is decreased as the detected value of is increased.

In the four-wheel drive vehicle according to the eighth aspect, when the working fluid pressure of the pressure accumulating means is supplied to the fluid pressure driving means, the working fluid pressure of the pressure accumulating means is set to a minimum value based on the detection value of the pressure detecting means. The closer to the pressure accumulation value, the smaller the maximum capacity of the fluid pressure motor to reduce the driving force generated. Similarly, the larger the traveling speed state of the vehicle based on the detection value of the speed state detection means, the larger the fluid pressure motor Since the maximum capacity is reduced, the working fluid pressure of the pressure accumulating means is consumed and the working fluid pressure reaches the minimum accumulated value, and when the driving force supply to the driven wheels is stopped and the driving force is no longer supplied, The switching from the state in which the driving force is supplied to the driven wheels to the state in which the driving force is not supplied is smoothly performed.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an embodiment when the present invention is applied to a four-wheel drive vehicle based on a front-wheel drive vehicle.

In the figure, reference numeral 1 denotes an engine as a main prime mover. The rotational driving force of the engine 1 is input to a front wheel side differential device 3 via a transmission 2 and is output to the output side of the differential device 3. Front wheels 5 are connected via a front axle 4 as a drive axle.

The front wheel side differential device 3 is rotationally driven by a ring gear 3b formed in a differential gear case 3a being meshed with a gear 2a connected to the output side of the transmission 2. A pinion 3d is attached to a pair of pinion shafts 3c formed in the differential gear case 3a, a pair of side gears 3e meshes with these pinion 3d, and the front axle 4 is connected to these side gears 3e.

Further, the differential gear case 3a
A second ring gear 3f is formed in parallel with the ring gear 3b. The second ring gear 3f is connected via a gear 3g meshing with the second ring gear 3f to a rotary shaft 6a of a suction throttle piston pump 6 as a fluid pressure pump that constitutes drive side fluid pressure driving means.

The suction throttle type piston pump 6 is constituted by, for example, a fixed cylinder type radial piston pump described in Japanese Patent Application No. 3-199684. The suction port 6b of the suction throttle pump 6 is connected to the strainer 7a arranged in the reservoir tank 7 and also the low pressure pipe (low pressure side pipe) 8L that constitutes the second flow path.
Through the pump port T of the electromagnetic directional control valve 9 for forward / backward switching. Further, the discharge port 6c of the suction throttle type piston pump 6 is passed through a high-pressure pipe (high-pressure side pipe) 8H that constitutes the first flow path, and an electromagnetic directional control valve 9 for forward / reverse switching is provided.
Is connected to the pump port P.

Here, the suction throttle type piston pump 6 is used.
The suction port 6b and the discharge port 6c do not interchange depending on the rotation direction of the rotating shaft 6a, and the discharge flow rate thereof reaches a set vehicle speed higher than the vehicle speed at which the maximum transmission torque starts to decrease from "0", for example. Up to the above, the vehicle speed increases at a relatively large increase rate in proportion to the increase in the vehicle speed, and at the set vehicle speed or higher, the increase rate becomes a relatively small increase rate in proportion to the increase in the vehicle speed, or a high-speed running state. Therefore, the vehicle is set to saturate at the maximum discharge flow rate at a set vehicle speed or higher that does not require the four-wheel drive state.

The forward / backward switching electromagnetic directional switching valve 9 has an input / output port A connected to an inflow port 10a of a free swash plate type variable displacement motor 10 (fluid pressure driving means) as a fluid pressure motor, which will be described later. The port B is connected to the outflow port 10b of the swash plate type variable displacement motor 10. The pump port P is connected to the input / output port A and the tank port T is connected to the input / output port B at the normal position where the solenoid 9a is in the non-energized state, and the pump port P is connected at the offset position where the solenoid 9a is in the energized state. The input / output port B and the tank port T are connected to the input / output port A, respectively.

That is, at the normal position, the high-pressure oil in the high-pressure pipe 8H is supplied to the inflow port 10a of the swash plate type variable displacement motor 10.
In addition, the low-pressure pipe 8L is connected to the outflow port 10b to drive the rotary shaft 10c to rotate in the rotational direction during forward traveling, and conversely, the high-pressure oil in the high-pressure pipe 8H is flown out at the offset position to the outflow port 10a of the swash plate variable displacement motor 10. (Inflow port when moving forward)
Further, the low-pressure pipe 8L is communicated with the inflow port 10b (the outflow port when moving forward), and the rotary shaft 10c is rotationally driven in the rotational direction when traveling in reverse.

The forward / reverse switching electromagnetic directional control valve 9
Is built in the swash plate type variable displacement motor 10, and the output ports A and B are connected to the inflow / outflow ports 10a and 10b of the swash plate type variable displacement motor 10 without passing through pipes, respectively.

The solenoid 9a of the forward / reverse switching electromagnetic directional control valve 9 is energized via a shift position detecting switch 9b which is turned on only when the solenoid 9a is selected to be reverse by a shift lever (not shown). DC power supply 9c
When the vehicle is traveling forward, it is controlled to be in a non-energized state, and when it is traveling backward, it is controlled to be energized.

Further, between the suction port 6b and the discharge port 6c of the suction throttle type piston pump 6, a relief valve 11 which determines the upper limit of the discharge pressure of the suction throttle type piston pump 6 is inserted. Further, the high-pressure pipe 8H and the low-pressure pipe 8L between the suction throttle type piston pump 6 and the forward-reverse switching electromagnetic switching valve 9 are communicated with each other by a communication pipe 12, and the two-wheel drive state is connected to the communication pipe 12. 2/4 switching valve (switching valve) 2 consisting of an electromagnetic on-off valve for switching between the vehicle and four-wheel drive state
1 is inserted. The 2/4 switching valve 21 is provided with a controller 13 which will be described later and is supplied to its solenoid 21a.
It operates according to the exciting current i ₂₁ from 0, and can communicate or block the flow of the hydraulic oil in the communication pipe 12.

A suction limit proportional control valve (intake oil amount control valve) 22 for controlling the amount of intake oil of the suction throttle type piston pump 6 is provided at the suction port 6b of the suction throttle type piston pump 6. There is. The suction limit proportional control valve 22 is a duty-controlled open / close solenoid valve, and is operated by a solenoid 22 a in response to a command from the controller 130.
The exciting current i ₂₂ is supplied to the valve at a predetermined cycle, and the opening / closing control is performed according to the exciting current i ₂₂ , so that the amount of oil supplied to the suction throttle piston pump 6 can be varied according to the exciting current i ₂₂ . .

Then, the communication pipe 12 of the high-pressure pipe 8H.
Between the above and the forward / backward switching electromagnetic directional control valve 9 allows the flow of fluid from the suction throttle type piston pump 6 side to the forward / backward switching electromagnetic directional control valve 9 side with respect to the high-pressure pipe 8H. The check valve 23 is inserted and the high pressure pipe 8
An accumulator (pressure accumulating means) 25 in which a constant pressure Pc is enclosed is connected downstream of the H check valve 23 via a communication pipe 24.

Further, the high pressure pipe 8H and the accumulator 25
An Acc outlet valve (accumulation switching valve) 26, which is an electromagnetic on-off valve, is inserted between the pressure sensor and the accumulator 25, and a pressure sensor (which detects the outlet pressure of the accumulator 25 between the Acc outlet valve 26 and the accumulator 25). Pressure detecting means) 27 is provided. The Acc outlet valve 26 has its solenoid 26.
Excitation current i ₂₆ from the controller 130 supplied to a
In accordance with the above, the accumulator 25 and the high-pressure pipe 8H are controlled to be in a communication state or a cutoff state.

The free swash plate type variable displacement motor 10 is
As shown in FIGS. 2 and 3, the rotary shaft 10c is rotatably supported by the pump housing 100. A cylindrical cylinder block 101 is coaxially fitted at a position inside the housing 100 of the rotary shaft 10c by serration fitting. In the cylinder block 101, an odd number, for example, seven pistons 102 are arranged at equal intervals along the rotation direction of the cylinder block 101. Each piston 102 is slidably supported by the cylinder block 101 in a direction parallel to its axial direction.

A swash plate 103 is arranged in the housing 100 at a position facing the right end surface of the cylinder block 101. The swash plate 103 includes a disc portion 103a,
It is composed of a projecting portion 103b projecting upward from its upper end, and its inclination angle is slidable around a predetermined swing shaft 106. In the swing shaft 106, the swash plate 103 is arranged in the cylinder block 1 with respect to the central shaft 105 of the rotary shaft 10c.
No. 01 is arranged so as to approach the facing surface, that is, in the upper direction in FIG.

The swash plate 103 has a disc portion 103.
The piston 1 is provided on the surface of the cylinder a facing the cylinder block 101.
The shoe 108 crowned at the right end of 02 is the shoe holder 10.
The shoe holder 109 is slidably brought into contact with the cylinder block 101, and the shoe holder 109 is pressed against the swash plate 103 side via the needle 111 by the pressing spring 110 arranged on the inner peripheral surface of the cylinder block 101.

Therefore, the piston 102 is attached to the swash plate 103.
The external force is transmitted from the swash plate 103. However, on the lower side of the swash plate 103 of the swash plate 103, a moment acting around the swing shaft by the force transmitted from the piston to the swash plate 103 is generated. And the central axis 105 are made to coincide with each other, the arm of the moment is shortened by the amount corresponding to the amount of eccentricity ε, resulting in a smaller value.
Is inclined so that the upper side of the swing shaft 104, that is, the side of the protrusion 103 approaches the cylinder block 101.

The tilt angle of the swash plate 103 increases as the external force transmitted to the swash plate by each piston increases, and the discharge capacity of the fluid pressure motor increases. The external force transmitted from the piston 102 to the swash plate 103 is the working fluid pressure that is the pressure of the fluid pressure chamber of the piston, that is, the difference between the discharge amount of the suction throttle piston pump 6 supplied to the motor and the suction amount of the motor. Since the working fluid pressure rises, the tilt angle of the swash plate 103 automatically increases accordingly.

Further, the swash plate 103 is urged by the urging mechanism 113 in the direction in which the tilt angle is reduced. The urging mechanism 113 contacts the left end surface of the protruding portion 103b of the swash plate 103 and presses the protruding portion 103b of the swash plate 103 in the right direction, that is, in the direction of reducing the tilt angle of the swash plate 103b. A cylinder device having a piston 113a, a coil spring 113c arranged in the fluid pressure chamber 113b of the cylinder device for urging the control piston 113a toward the swash plate 103, and a fluid pressure chamber 113.
b is a communication pipe 113d that connects b to the low pressure portion in the swash plate type variable displacement motor 10, for example, the low pressure pipe 8L side or opens to the atmosphere.
And an orifice 113e inserted in the middle of the communication pipe 113d.

On the other hand, a maximum displacement regulating mechanism 115 for regulating the maximum displacement angle of the swash plate type variable displacement motor 10 by regulating the maximum tilt angle of the swash plate 103 is provided on the lower end side of the swash plate 103 opposite to the protruding portion 103b. It is arranged.

The maximum capacity regulating mechanism 115 is a step motor 116, which is, for example, a stepping motor installed in the pump housing 100, a screw shaft 117 connected to the rotary shaft of the step motor 116, and the screw shaft 117. A ball nut 118 that is screwed into the ball nut 118 and is non-rotatably guided by a guide member, and a disc portion 103a of the swash plate 103 that is formed to project from the ball nut 118.
The locking piece 119 that abuts on the right end side of the ball nut 11
8, and stoppers 120L and 120S that restrict the large-capacity position and the small-capacity position by abutting against each other.

On the other hand, a valve plate 121 fixed to the housing 100 is provided on the left end surface of the cylinder block 101.
Are in sliding contact with each other, and the valve plate 121 and each piston 1
A communication hole 123 is formed between the bore 122 that accommodates 02. As shown in FIG. 3, in the valve plate 121, an inflow port 10a (outgoing port during reverse drive) is provided in the left half and an outflow port 10b (reverse inflow port) is provided in the right half along the movement path of the communication hole 123. Are formed.

The maximum specific discharge amount of the swash plate type variable displacement motor 10 (the specific protrusion amount when the ball nut 118 of the maximum displacement regulating mechanism 115 is in contact with the stopper 120L) is the suction throttle piston pump. 6 is set to be larger than the specific ejection amount.

On the other hand, a gear 16 is attached to the rotary shaft 10c of the swash plate type variable displacement motor 10, and the differential gear case 17 of the rear wheel side differential device 17 is attached to the gear 16.
The ring gear 17b formed on a is meshed. The rear wheel side differential device 17 has substantially the same configuration as the front wheel side differential device 3 described above, and is different from the differential gear case 1 in FIG.
A pair of pinion shafts 17c is formed in 7a, and a pair of side gears 17e meshes with the pinion 17d attached to the pair of pinion shafts 17c. A rear axle 18 is connected to the side gears 17e, and a rear wheel 19 is connected to the rear axle 18.

Then, the step motor 116 of the maximum capacity regulating mechanism 115 is driven and controlled by the controller 130, whereby the ball nut 118 moves between the stoppers 120S and 120L, and the ball nut 118 is inclined depending on the position of the ball nut 118. The maximum tilt angle of the plate 103 is controlled.

The controller 130 is composed of, for example, a microcomputer. As shown in FIG. 4, various sensors are connected to its input side and a step motor 116 is connected to its output side. Here, the controller 130
Corresponds to the switching valve control means and the regenerative control means.

As shown in FIG. 4, the controller 130 includes the pressure sensor 27 and the front wheel side rotation speed sensor 2 as described above.
01, rear wheel side rotation speed sensor 202, accelerator sensor 20
3, brake sensor 205, engine speed sensor 20
6. An electric signal from the shift position detection switch 207 is input. Further, an anti-skid control device 2 (not shown)
A indicating whether or not the anti-skid control from 50 is in progress
The S flag is input.

The front wheel side rotation speed sensor 201 and the rear wheel side rotation speed sensor 202 as the rotation speed detecting means are provided, for example, on either one of the front wheel and the rear wheel, respectively, and correspond to the rotation speeds of the front wheel and the rear wheel. Output a pulse signal. Also,
The accelerator sensor 203 detects the stroke amount of the accelerator pedal, and the brake sensor 205 detects the stroke amount of the brake pedal. Further, the engine rotation speed sensor 206 detects the engine rotation speed from the ignition ignition pulse of the engine. The shift position detection switch 207 is a shift lever (not shown)
When the range, D range, L range, or N range is selected, a detection signal corresponding to each range that is turned on is output.

Then, the detection signal which is a pulse signal corresponding to the wheel speed from the front wheel side rotation speed sensor 201 is a frequency-voltage (F / V) converter 301 for converting this into a voltage value.
Also, it is input to the controller 130 via the A / D converter 302 that converts this converted signal into a digital signal. Similarly, the detection signal from the rear wheel side rotation speed sensor 202 is F
It is input to the controller 130 via the / V converter 303 and the A / D converter 304. Further, the detection signals of the accelerator sensor 203 and the brake sensor 205 are converted into digital values via A / D converters 305 and 306, respectively, and input to the controller 130.

The detection signal of the engine speed sensor 206 is sent to the controller 13 via the waveform shaper 307.
0, and the detection signal of the pressure sensor is the hydraulic signal P.
The controller 13 via the A / D converter 308 as a
Input to 0.

This controller 130 is at least
Input interface circuit 130a, output interface circuit 130b, arithmetic processing unit 130c, and storage unit 13
0d. The arithmetic processing unit 130c includes the front wheel side rotation speed sensor 201 and the rear wheel side rotation speed sensor 202.
The rotation speed ratio ΔN of the front and rear wheels is detected based on the rotation speeds of the front wheel and the rear wheel, and the 2/4 switching valve 21 is opened / closed based on the detected ratio ΔN, and the suction throttle type piston pump 6 and the swash plate type variable The fluid pressure transmission mechanism constituted by the capacity motor 10 and the members interposed between the high-pressure pipe 8H and the low-pressure pipe 8L connecting these is controlled to a two-wheel drive state or a four-wheel drive state, and at the same time, a suction limit proportional control valve 22 is controlled to the closed state, and the mechanical loss torque due to the fluid pressure transmission mechanism in the two-wheel drive state is reduced.

Further, when the controller 130 detects that the brake of the vehicle is being used based on the detection signal of the brake sensor 205 in the two-wheel drive state, the 2/4 switching valve 21 is closed and the fluid pressure transmission is performed. The mechanism is controlled to the four-wheel drive state, the Acc outlet valve 26 is opened, and the opening degree of the suction limit proportional control valve 22 is controlled according to the depression state of the brake pedal. By controlling the step motor 116 of No. 10, the tilt angle of the swash plate 103 is restricted to the minimum position, and the working fluid pressure due to the amount of oil discharged from the suction throttle piston pump 6 during braking is accumulated in the accumulator 25. Then, during non-braking in the two-wheel drive state, the 2/4 switching valve 21 is opened to control the fluid pressure transmission mechanism to the four-wheel drive state, and the Acc outlet valve 26 is opened to store the working fluid pressure accumulated in the accumulator 25. Is supplied to the swash plate type variable displacement motor 10.

Then, in the arithmetic processing unit 130c, the 2/4 switching valve 21, the suction limit proportional control valve 22, A
A control signal for controlling the opening / closing of the cc outlet valve 26 is formed and supplied to the solenoid drive circuits 314, 315, 316 via the D / A converters 311, 312, 313, respectively, and the exciting currents i ₂₁ , i ₂₂ are respectively generated. , I ₂₆ are supplied to the solenoids 21a, 22a, 26a of the respective control valves.

A control signal to the step motor 116 is sent via the motor drive circuit 321 to the step motor 116.
Is supplied to. In this motor drive circuit 321, for example, a step motor drive signal is formed from the current position information and the target position of the step motor that is held in advance, and the drive signal is output to the step motor 116 and the step motor 116 is
The position information after updating is stored.

Next, the operation of the above embodiment will be described with reference to the flowchart of FIG. 5 showing the control processing of the controller 130. The control process of FIG. 5 is executed as a timer interrupt process every predetermined time (for example, 10 msec) while the engine 1 is rotating, that is, while the ignition switch is on.

First, in step S1, the detection signals from the front wheel side rotation speed sensor 201 and the rear wheel side rotation speed sensor 202 are read, and, for example, by counting the number of pulses per unit time, the rotation speeds of the front and rear wheels are read. And the ratio ΔN of the rotational speeds of the front and rear wheels is calculated. Then, it is determined whether or not this rotation speed ratio ΔN is smaller than a preset threshold value α _N.

When ΔN <α _N , the process proceeds to step S2 to read the detection signal composed of the stroke signal of the brake pedal from the brake sensor 205,
Based on this, it is determined whether the brake switch is in the on state. Then, when the brake switch is not in the on state, the process proceeds to step S3, a control signal for fully closing the intake restriction proportional control valve 22 is formed and output, and the 2/4 switching valve 21 is opened. A control signal for setting the state is formed and output (step S4).

Then, in step S5, the pressure sensor 27
Of the hydraulic pressure signal Pa is larger than the enclosed pressure P _{0 of the} accumulator 25, and it is determined that the N range is off based on the position detection signal of the shift position detection switch 207. When it is determined that the accelerator pedal is being depressed and the accelerator pedal switch is in the on state based on this, a control signal for opening the Acc outlet valve 26 is formed in step S6 and is output. In addition, based on the control map shown in FIG. 6, the swash plate 1 of the swash plate type variable displacement motor 10 will be described.
The maximum tilt angle of 03 is determined, and a drive signal for the step motor 116 that moves the locking piece 119 to a position that restricts the maximum tilt angle of the swash plate 103 to the determined maximum tilt angle is generated and output. (Step S7). Then, the timer interrupt processing ends.

Here, the tilt angle of the swash plate type variable displacement motor 10 is such that the outlet pressure of the accumulator 25, that is, the hydraulic pressure signal Pa detected by the pressure sensor 27 and the enclosed pressure P _{0 of the} accumulator 25 are P ₀ ≦ Pa + α. The interval is set so that the maximum tilt angle increases as the outlet pressure Pa increases, and the predetermined value α is the depression amount of the accelerator pedal as the traveling speed detecting means, the shift position of the shift lever, and the engine. It is set based on the traveling speed state of the vehicle set by the number of revolutions, and is set such that α becomes smaller as the vehicle travels at a lower speed.

On the other hand, in step S5, Pa> P ₀ ,
When all of these conditions that the N range is not selected and the accelerator switch is in the on state are not satisfied, the process proceeds to step S11, and a control signal for closing the Acc outlet valve 26 is formed and this is set. Further, a drive signal for the step motor 116 that outputs the swash plate type variable displacement motor 10 and regulates the tilt angle of the swash plate 103 to the minimum value is generated and output to the motor drive circuit 321 (step S12). Then, the timer interrupt processing ends.

Further, when the rotation speed ratio ΔN of the front and rear wheels is not ΔN <α _{N in} step S1, a control signal for closing the 2/4 switching valve 21 is output (step S21), and then the intake restriction is performed. A control signal for fully opening the proportional control valve 22 is output (step S22), and then the Acc outlet valve 2 is output.
A control signal for closing 6 is output (step S2).
3). Then, the swash plate 103 of the swash plate type variable displacement motor 10
The drive signal to the step motor 116 that restricts the tilt angle of the maximum value is output (step S24), and the timer interrupt process ends.

When the brake switch is in the ON state in step S2, the process proceeds to step S31, and the hydraulic signal Pa from the pressure sensor 27 has a preset maximum value Pa _MAX (Pa _MAX > P) of the hydraulic signal. ₀ ), and if Pa <Pa _MAX ,
Next, it is determined whether or not the anti-skid control is being performed based on the AS flag indicating that the anti-skid control is being performed from the anti-skid control device 250 (step S32). If the anti-skid control is not being performed, the 2/4 switching is performed. A control signal for closing the valve 21 is output (step S33), and a drive signal for the step motor 116 for limiting the tilt angle of the swash plate 103 of the swash plate variable displacement motor 10 to a minimum is output (step S34). Further, a control signal for opening the Acc outlet valve 26 is output (step S35). Then, based on the control map shown in FIG. 7, the opening degree of the intake restriction proportional control valve 22 is controlled (step S36), and the timer interrupt process is ended.

The opening of the intake control proportional control valve 22 is determined by the outlet pressure of the accumulator 25, that is, the hydraulic signal P.
While a and its maximum value Pa _MAX are Pa ≦ Pa _MAX −β, as the outlet pressure Pa increases, the opening degree tends to shut off so that the intake oil amount of the intake control proportional control valve 22 decreases. Further, based on the detection signal of the brake sensor 205, the larger the depression amount of the brake pedal is, the larger the predetermined value β is set.

If the hydraulic signal Pa is not Pa <Pa _MAX in step S31, or if the anti-skid control is in step S32, the process proceeds to step S41 to open the 2/4 switching valve 21. Then, a control signal for closing the intake outlet proportional control valve 22 is output (step S42), and a control signal for closing the intake restriction proportional control valve 22 is output (step S42). S43). Then, the timer interrupt processing ends.

Therefore, when the vehicle is currently stopped on a high friction coefficient road such as a dry road surface and the ignition switch (not shown) is in the off state and the ignition switch is turned on to start the engine, When the ignition switch is turned on, power is supplied to the controller 130, predetermined initialization is executed, the Acc outlet valve 26 is opened, and the outlet pressure Pa of the accumulator 25 is set to the fluid pressure on the high pressure pipe 8H side, that is, After setting to substantially zero, the control process of FIG. 5 is executed.

When the engine 1 starts the forward running from the braking state in the idling state, the shift lever (not shown) is switched to the forward running state so that the vehicle can be started. At this time, the shift position detection switch 9b on the reverse traveling side is maintained in the off state, so the solenoid 9a of the forward / reverse switching electromagnetic directional switching valve 9 is maintained in the non-energized state, and the switching position is the normal position shown in FIG. Hold.

In this state, by releasing the brake pedal and stepping on the accelerator pedal, the rotational force of the engine 1 is transmitted to the front wheel side differential device 3 via the transmission 2 and the front wheel side differential device 3 is operated. The forward movement of the vehicle is started by rotationally driving the front wheels 5 in the forward direction.

At this time, since the vehicle has started with a high friction coefficient and the rotation speeds of the front wheels and the rear wheels thereof are substantially the same (steps S1 and S2), the intake proportional limit proportional control valve 22 is fully closed. The 2/4 switching valve 21 is controlled to the open state (steps S3 and S4). At this time,
The outlet pressure Pa of the accumulator 25 is substantially zero, and Pa>
Since it is P ₀ , the Acc outlet valve is controlled in the closed state, and the tilt angle of the swash plate type variable displacement motor 10 is limited to the minimum position (steps S11 and S12).

Therefore, the rotary shaft 6a of the suction throttle type piston pump 6 is rotationally driven as the vehicle starts.
Since the suction limit proportional control valve 22 is controlled to be fully closed, the suction oil amount of the suction throttle piston pump 6 becomes substantially zero, and the working oil is not discharged from the suction throttle piston pump 6. Also, the rear wheels 19 and the front wheels 5 as the vehicle starts.
Since the rotary shaft 10c of the swash plate type variable displacement motor 10 is rotated via the rear wheel side differential device 17, it is driven from the suction throttle type piston pump 6 because it is rotationally driven in the same direction and at the same rotational speed. Since no oil is discharged, no hydraulic oil is discharged from the swash plate type variable displacement motor 10.

At this time, since the vehicle is traveling on a high friction coefficient road and the rotation speeds of the front wheels and the rear wheels thereof are substantially the same, the intake restriction proportional control valve 22 is in the fully closed state, the 2/4 switching valve 21. Remains open. Further, although the accelerator pedal is depressed and the N range is not selected by the shift lever, the outlet pressure P of the accumulator 25 is
Since a is smaller than the filling pressure P ₀ of the accumulator 25, the Acc outlet valve 26 maintains the closed state, and the step motor 116 sets the tilt angle of the swash plate 103 of the swash plate variable displacement motor 10 to the minimum position. It remains in the position to be regulated.

As a result, the pressure in the high-pressure pipe 8H does not rise and remains substantially zero, and the swash plate type variable displacement motor 10 does not transmit the driving torque to the driven axle 18, that is, the rear wheel 19. Therefore, the vehicle travels forward in the same state as the front-wheel drive vehicle (two-wheel drive vehicle). At this time, since the suction throttle piston pump 6 and the swash plate type variable displacement motor 10 do not suck and discharge the hydraulic oil, they are in a no-load operating state, and the mechanical loss torque is reduced.

When the accelerator pedal is released and the brake pedal is depressed from this forward traveling state, the outlet pressure Pa is substantially zero and Pa <Pa _MAX (step S1,
S2, S31), and then proceeds to step S32. At this time, assuming that anti-skid control is not in progress, 2/4
The switching valve 21 is controlled to the closed state, and the step motor 116 is
Is maintained at a position where the tilt angle of the swash plate 103 of the swash plate type variable displacement motor 10 is restricted to the minimum position, the Acc outlet valve 26 is controlled to be in the open state, and the suction limit proportional control valve 2
2 is controlled to an opening degree according to the depression state of the brake pedal (steps S33 to S36).

As a result, the rotary shaft 6a of the suction throttle type piston pump 6 is rotationally driven, whereby the opening degree of the suction limit proportional control valve 22, that is, the amount of oil supplied to the suction throttle type piston pump 6 and the rotation speed. A hydraulic fluid having a discharge flow rate corresponding to the above is discharged. The discharged hydraulic oil is supplied to the inflow port 10a of the swash plate type variable displacement motor 10 via the high pressure pipe 8H and the forward / reverse switching electromagnetic direction switching valve 9.

At this time, since the brake pedal is depressed, the rotation speed on the rear wheel side is slower than the rotation speed on the front wheel side, and the tilt angle of the swash plate 103 is restricted to the minimum position. Therefore, the discharge flow rate of the swash plate type variable displacement motor 10 is limited, and the discharge flow rate of the swash plate type variable displacement motor 10 becomes larger than the discharge flow rate of the suction throttle type piston pump 6, so that the swash plate type variable displacement motor 10 Is used as a load to increase the hydraulic pressure of the high-pressure pipe 8H.

Therefore, since the working oil pressure of the high-pressure pipe 8H rises, this acts as a load on the suction throttle piston pump 6, and the assist braking force is applied to the rotary shaft 6a of the suction throttle piston pump 6, that is, the front wheel 5. Will operate as. At this time, the Acc outlet valve 26
Is open, the high pressure in the high-pressure pipe 8H is accumulated in the accumulator 25.

Then, with the brake pedal still depressed, the pressure in the high-pressure pipe 8H rises, and the outlet pressure Pa of the accumulator 25 reaches the preset maximum value P of the outlet pressure.
or _{a MA X (Pa ≧ Pa MAX} ) when it comes (step S3
1) The 2/4 switching valve 21 is opened, the Acc outlet valve 26 is closed, and the suction limit proportional control valve 22 is fully closed.
The fluid pressure in the high-pressure pipe 8H is accumulated in the accumulator 25 to return the fluid pressure transmission mechanism to the two-wheel drive state (step S
41-S43). As a result, the energy during braking is collected and stored in the accumulator 25 in the form of fluid pressure.

At this time, when performing energy recovery during braking, the opening degree of the intake limit proportional control valve 22 is controlled based on the outlet pressure Pa as shown in the control map of FIG.
As the outlet pressure Pa increases, the opening degree of the suction limit proportional control valve 22 decreases, that is, the outlet pressure P
The suction oil amount of the suction throttle type piston pump 6 is controlled to decrease according to the rise of a, and the braking force accompanying the energy recovery to the suction throttle type piston pump 6 is decreased, so that the outlet pressure Pa = When the 2/4 switching valve 21 is controlled to be in the open state at the time of reaching Pa _MAX , the fluid pressure in the high-pressure pipe 8H sharply decreases, so that the front wheels 5
The assist braking force against does not suddenly disappear,
For the front wheels 5, the state where the braking force corresponding to the sum of the assist braking force due to energy recovery and the braking force due to the disc brake or the like is working smoothly switches to the state where only the braking force due to the disc brake or the like is working. As a result, the vehicle can maintain a stable braking state.

Further, as the amount of depression of the brake pedal increases, the pressure of the high-pressure pipe 8H, that is, the rate of change of the outlet pressure Pa according to the amount of oil discharged from the suction throttle piston pump 6, increases, but the control map of FIG. As shown in
The predetermined value β is set to increase as the amount of depression of the brake pedal increases, and the opening of the suction limit proportional control valve 22 is narrowed to the minimum value at an earlier stage. Instead, it is possible to smoothly switch from the state in which the assist braking force is added to the front wheels 5 due to the energy recovery to the state in which the assist braking force is not added.

On the other hand, the brake pedal is depressed, the energy is collected during braking, and the accumulator 2
5 the outlet pressure Pa is lower state than its maximum value Pa _MAX, the anti-skid control process in the anti-skid control unit 250 is started (Step S1, S2, S
31 and S32), the 2/4 switching valve 21 is opened, the Acc outlet valve 26 is closed, and the suction limit proportional control valve 22 is fully closed (steps S41 to S43), and the fluid pressure transmission mechanism is driven by two wheels. Transition to the state. As a result, the pressure of the high-pressure pipe 8H at this time is accumulated and held in the accumulator 25.

From this state, if the brake pedal is released and then the brake pedal is depressed again, as long as the anti-skid control process is not performed,
Energy at the time of braking is accumulated in the accumulator 25 as fluid pressure.

Also, after releasing the brake pedal,
The front and rear wheels rotate when the accelerator pedal is depressed.
When the numbers are almost the same (steps S1 and S2),
Suction limit proportional control valve 22 is fully closed, 2/4 switching valve
21 is controlled to the open state, and the vehicle is similar to the two-wheel drive state.
The vehicle travels forward in this state (steps S3 and S4). This and
Then, the outlet pressure Pa of the accumulator 25 is as described above.
And pressure is accumulated, Pa> P ₀, Then Axelpe
Since the dull is stepping forward and traveling forward,
The cc outlet valve 26 is controlled to the open state, and the swash plate type variable
The tilt angle of the swash plate 103 of the displacement motor 10 is determined by the control matrix shown in FIG.
The smaller the outlet pressure Pa, the smaller
(Steps S3 to S7).

Since the check valve 23 is provided in the high pressure pipe 8H, the working fluid pressure accumulated in the accumulator 25 is supplied only to the swash plate type variable displacement motor 10 and input to the swash plate type variable displacement motor 10. The working fluid pressure is increased. Therefore, the swash plate type variable displacement motor 10 generates a drive torque according to this working fluid pressure, and this is transmitted to the rear wheels 19 via the rear wheel side differential device 17, and the vehicle is similar to a four-wheel drive vehicle. Drive forward in this state.

At this time, as for the tilt angle of the swash plate 103, the outlet pressure Pa is Pa ≦ P ₀ + α (α is a predetermined value set in advance)
Since the outlet pressure Pa is set to decrease as the outlet pressure Pa decreases, the assist driving force to the rear wheels 19 gradually decreases as the outlet pressure Pa decreases. When Pa becomes Pa ≦ P ₀ , the rear wheels 19
The assist driving force to the vehicle does not suddenly disappear, and the vehicle can maintain a stable running state. Further, at this time, the larger the function value representing the traveling speed state of the vehicle, which is obtained by the accelerator pedal depression amount, the shift position of the shift lever (not shown), and the engine speed,
That is, the higher the speed is, the smaller the predetermined value α is set, and the assist driving force is decreased from the time when the outlet pressure Pa is higher. Therefore, at a higher speed, the outlet pressure Pa decreases more, but faster. Since the assist driving force is decreased from the time point, the assist driving force to the rear wheels 19 does not suddenly disappear when the outlet pressure Pa becomes Pa ≦ P _0, and the assist driving force acts on the rear wheels 19. From
The transition to a state where the assist driving force does not work is performed smoothly.

Then, when the accelerator pedal is opened from this state, the Acc outlet valve 26 is controlled to the closed state and the tilt angle of the swash plate 103 is restricted to the minimum value (steps S11 and S12). The supply of the assist driving force to the rear wheels 19 is stopped. When the accelerator pedal is stepped on again from this state, if the outlet pressure Pa is larger than P _0, it is possible to generate the assist driving force, so the Acc outlet valve 26 is controlled to the open state again, and the tilted angle is reduced. The tilt angle of the plate 103 is controlled according to the outlet pressure Pa, and the assist driving force is supplied to the rear wheels 19 again.

Then, when the fluid pressure accumulated in the accumulator 25 is consumed as the assist driving force and the outlet pressure Pa becomes equal to or lower than the enclosed pressure P ₀ , the Acc outlet valve 26 is controlled to the closed state and the swash plate 103. The tilt angle of the vehicle is regulated to the minimum value, and thereafter, the vehicle travels in a state similar to the normal two-wheel drive state.

Then, for example, when the vehicle starts on a low friction coefficient road such as an icy road or a snowfall road, the front wheels 5 are driven to rotate as described above. Since the front wheels 5 that are the driving wheels slip, a difference occurs in the rotational speeds of the front and rear wheels, so that the 2/4 switching valve 21 is closed, the intake limiting proportional control valve 22 is fully open, and the Acc outlet valve 26 is closed. Controlled by. Further, the tilt angle of the swash plate 103 is restricted to the maximum position (steps S1, S21-
S24).

As a result, the larger the slip of the front wheels 5, the relatively the discharge amount of the suction throttle type piston pump 6 per unit time increases, and the same discharge amount is kept on the side of the swash plate type variable displacement motor 10 following this. Swash plate 1 to output
03 is automatically adjusted in a direction in which the tilt angle increases, and is fixed when the tilt angle restriction position is reached.

When the front wheel speed increases and the discharge amount of the suction throttle type piston pump 6 exceeds the discharge flow rate of the swash plate type variable displacement motor 10, the resistance of the swash plate type variable displacement motor 10 becomes a load. The hydraulic pressure of the high-pressure pipe 8H rises, the swash plate type variable displacement motor 10 generates a drive torque according to the supply pressure from the high-pressure pipe 8H, and is transmitted to the rear wheel 19 via the rear wheel side differential device 17. , The vehicle travels forward in the same state as a four-wheel drive vehicle.

When the vehicle is moving backward, the shift position detection switch 9b is turned on by switching the shift lever to the R range position, so that the solenoid 9a of the forward / reverse switching electromagnetic directional control valve 9 operates. When the power is turned on, the switching position is switched from the normal position to the offset position, whereby the hydraulic oil in the high-pressure pipe 8H is supplied to the reverse inlet port 10b of the swash plate type variable displacement motor 10 and discharged from the reverse outlet port 10a. By returning the hydraulic oil to the low-pressure pipe 8L side through the flow path 12, the rotary shaft 10c of the swash plate type variable displacement motor 10 is reversed from that during forward traveling, and the rear wheel 19 is rotated in reverse. Therefore, when the vehicle is moving backward, the driving force is transmitted in the same way as when moving forward, and when the accelerator pedal is depressed with the front and rear wheels having no predetermined rotation speed ratio, the outlet pressure of the accumulator 25 is reduced. When Pa is Pa> P ₀ and the assist driving force for the rear wheel 19 can be generated, the Acc outlet valve 26 is controlled to the open state, and the fluid pressure accumulated in the accumulator 25 is used as the assist driving force for the rear wheel 19. Is supplied to. Further, when the brake pedal is depressed in a state where the front and rear wheels do not have a predetermined rotation speed ratio and the anti-skid control is not operated, the 2/4 switching valve 21 is closed, A
The cc outlet valve 26 and the suction limit proportional control valve 22 are controlled to be in the open state, the tilt angle of the swash plate type variable displacement motor 10 is restricted to the minimum position, and the high pressure pipe 8H is the same as during forward traveling.
Is generated in the accumulator 25, and the accumulator 25 accumulates the pressure.

Therefore, when the vehicle is running in a traveling state in which the front and rear wheels do not have a predetermined rotational speed ratio, that is, in a two-wheel drive state, the hydraulic pressure of the working fluid discharged by the suction throttle piston pump 6 is applied during braking. Is accumulated in the accumulator 25, and when not braking, the working fluid pressure accumulated in the accumulator 25 is supplied to the swash plate variable displacement motor 10.
Since the swash plate type variable displacement motor 10 transmits the driving force corresponding to the supplied working fluid pressure to the driven wheels, the fuel consumption in the two-wheel drive state improves accordingly. Therefore, although the fuel consumption decreases with the provision of the fluid pressure transmission device, by using the working fluid pressure during braking as the driving force during non-braking, as a result, the reduction of the fuel consumption of the entire vehicle is prevented. be able to.

When the working fluid pressure accumulated in the accumulator 25 is supplied to the swash plate type variable displacement motor 10, as shown in the control map of FIG.
5, the tilt angle of the swash plate 103 is set according to the traveling speed state of the vehicle based on the outlet pressure, the selected position of the shift lever, the stroke amount of the accelerator pedal, the number of revolutions of the engine, and the like. When accumulating the working fluid pressure during braking, as shown in the control map of FIG. 7, the opening degree of the intake restriction proportional control valve 22 is adjusted according to the outlet pressure of the accumulator 25 and the depression amount of the brake pedal. Therefore, when the outlet pressure Pa reaches the filling pressure P ₀ , or the outlet pressure Pa is the maximum value Pa of the outlet pressures.
At the time of reaching _MAX , the running state of the vehicle becomes unstable as the supply of the working fluid pressure of the accumulator 25 to the swash plate variable displacement motor 10 is stopped or the accumulation of the working fluid pressure to the accumulator 25 is stopped. Therefore, it is possible to maintain a good running condition.

Further, since the accelerator sensor 203 is adapted to detect the stroke of the accelerator pedal, it is possible to more reliably detect the depression state of the accelerator pedal.

Further, the regenerative control process for accumulating the working fluid pressure in the accumulator 25 and the accumulated working fluid pressure for supplying the accumulated working fluid pressure to the swash plate type variable displacement motor 10, and the control process for bringing the fluid pressure transmission mechanism into the four-wheel drive state. Since the switching between and is performed based on the rotational speed ratio of the front and rear wheels, the timing of these switching can be easily recognized and the switching can be easily performed.

Further, the regenerative control processing for accumulating the working fluid pressure in the accumulator 25 is performed when the vehicle does not need the four-wheel drive state, that is, the rotation speed ratio Δ of the front and rear wheels.
Since it is performed only when _N is smaller than the reference value α _N , the original functional performance of the four-wheel drive vehicle is not deteriorated, and the responsiveness of the system from the two-wheel drive state to the four-wheel drive state is reduced. There is nothing to do.

In the above embodiment, the case where the front wheel drive vehicle is used as a base has been described. However, the present invention is not limited to this, and when the rear wheel drive vehicle is used as a base, the fluid pressure pump is provided on the rear wheel side. By arranging the swash plate type variable displacement motor 10 on the front wheel side, it is possible to obtain the same effect as that of the above-described embodiment.

Further, in the above embodiment, the case where the opening / closing control of the 2/4 switching valve 21 is performed based on the rotation speed ratio of the front and rear wheels has been described. It is also possible to perform the control based on the difference in the number of rotations, and even in this case, the same effect as the above can be obtained.

Further, in the above embodiment, the tilt angle of the swash plate 103 of the swash plate type variable displacement motor 10 and the opening of the suction limit proportional control valve 22 are based on the control maps shown in FIGS. 6 and 7. Although the case where the degree is set has been described, the present invention is not limited to this, and the control is such that the driving force supplied to the driven wheels does not suddenly disappear when the outlet pressure Pa becomes equal to or lower than the accumulator filling pressure P _0. Any map may be used, and similarly, any control map may be used so that the braking force acting on the drive wheels does not suddenly disappear when the outlet pressure Pa reaches Pa _MAX .

In the above embodiment, the case where the high pressure side pipe 8H is unloaded by the 2/4 switching valve 21 has been described, but the present invention is not limited to this, and the relief pressure of the relief valve 11 can be varied. By
It may be performed.

When the hydraulic pump on the front wheel side is a pump whose maximum flow rate is adjusted by the variable throttle on the upstream side, and the free wheel swash plate type variable displacement motor is used as the motor on the rear wheel side. However, the variable displacement pump and the variable displacement motor are not limited to this,
It is possible to apply.

Further, as the free swash plate type variable displacement motor, the one in which the swash plate tilts on one side has been described, but the invention is not limited to this, and a motor in which the swash plate tilts on both sides can be applied. .

[0100]

As described above, according to the four-wheel drive vehicle of the first aspect, the working fluid pressure from the fluid pressure supplying means to the fluid pressure driving means is accumulated in the pressure accumulating means during braking, and the accumulated operation is performed. By supplying the fluid pressure to the fluid pressure drive means during non-braking, the working fluid pressure from the fluid pressure supply means during braking is effectively utilized as the driving force during specific braking, and the reduction in fuel consumption of the entire vehicle is prevented. be able to.

Further, according to the four-wheel drive vehicle of the second aspect, the switching valve control means controls the switching valve to be in the communicating state in accordance with the running state of the vehicle so that the fluid pressure supply means and the fluid pressure driving means are connected to each other. When the vehicle is running in the state where the power is cut off, the working fluid pressure supplied from the fluid pressure supply means to the fluid pressure drive means during braking is stored in the pressure storage means, and the vehicle is running in the non-braking state. In addition, by supplying the working fluid pressure at the time of braking accumulated in the pressure accumulating means to the fluid pressure driving means, the working fluid pressure at the time of braking acts as a driving force for the driven wheels at the time of non-braking. Can be prevented.

According to the four-wheel drive vehicle of the third aspect, the accumulated pressure is switched to the high-pressure side pipe between the switching valve and the fluid pressure drive means for disconnecting the high-pressure side pipe and the low-pressure side pipe. An accumulator is installed through the valve, and a check valve is provided between the pressure accumulation switching valve and the switching valve.When the braking valve is closed, the switching valve is shut off so that the pressure accumulation switching valve is in communication. By accumulating the pressure in the accumulator via the accumulator switching valve and supplying the working fluid pressure during braking stored in the accumulator during non-braking to the fluid pressure drive means, the working fluid pressure can be easily accumulated, Further, the accumulated working fluid pressure can be easily supplied as a driving force to the driven wheels.

Further, according to the four-wheel drive vehicle of the fourth aspect, when the ratio of the rotation speeds of the front and rear wheels detected by the rotation speed detecting means is smaller than a preset threshold value, the switching valve is brought into the communication state. By controlling, the control for making the four-wheel drive state of the fluid pressure transmission mechanism and the switching process between the accumulation of the working fluid pressure or the supply processing of the working fluid pressure to the fluid pressure driving means are easily performed based on the rotation speed ratio of the front and rear wheels. be able to.

According to the four-wheel drive vehicle of the fifth aspect, the intake oil amount to the fluid pressure pump is set based on the working fluid pressure of the pressure accumulating means, and the fluid pressure pump of the fluid pressure pump is set based on the braking state of the vehicle. By setting the discharge fluid amount, the traveling stability of the vehicle can be maintained even when the working fluid pressure is accumulated in the pressure accumulating means.

According to the four-wheel drive vehicle of the sixth aspect, the braking state of the vehicle is detected by detecting the stroke of the brake pedal, so that the braking state of the vehicle can be detected more easily and reliably.

According to the four-wheel drive vehicle of the seventh aspect, since the fluid pressure motor is a fluid pressure motor whose maximum displacement can be changed, the fluid pressure motor is generated by changing the maximum displacement. The driving force can be easily adjusted.

Further, in the four-wheel drive vehicle according to the eighth aspect, the maximum capacity of the fluid pressure motor is set according to the working fluid pressure of the pressure accumulating means, and the maximum capacity of the fluid pressure motor is set according to the traveling speed state of the vehicle. Since the capacity is set, it is possible to smoothly switch from the state in which the driving force is supplied to the driven wheels to the state in which the driving force is not supplied according to the working fluid pressure of the pressure accumulating means.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a four-wheel drive vehicle showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a free swash plate type variable displacement motor applicable to an embodiment of the present invention.

FIG. 3 is a schematic diagram showing a mechanism of the free swash plate type variable displacement motor of FIG.

FIG. 4 is a block diagram showing an example of an energy regeneration control device.

FIG. 5 is a flowchart showing an example of a control processing procedure of a controller.

FIG. 6 is a control map showing the correspondence between the tilt angle of the swash plate of the free swash plate type variable displacement motor, the outlet pressure, and the traveling speed state.

FIG. 7 is a control map showing the correspondence between the opening of the intake restriction proportional control valve, the outlet pressure, and the stroke amount of the brake pedal.

[Explanation of symbols]

 1 engine 5 front wheel (driving wheel) 6 suction throttle type piston pump 8H high pressure piping 8L low pressure piping 9 electromagnetic switching valve for forward / reverse switching 10 free swash plate type variable capacity motor 19 rear wheel (driven wheel) 21 2/4 switching valve 22 Intake limit proportional control valve 25 Accumulator 26 Acc outlet valve 27 Pressure sensor 103 Swash plate 116 Step motor 130 Controller 201 Front wheel side rotation speed sensor 202 Rear wheel side rotation speed sensor 203 Accelerator sensor 205 Brake sensor 206 Engine rotation speed sensor 207 Shift position detection switch

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroo Kitada 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd.

Claims (8)

[Claims] 1. A fluid pressure supply means having a fluid pressure pump that rotates in association with a drive axle driven by a main engine and discharges a working fluid; and a fluid pressure supply means associated with an axle of a driven wheel and from the fluid pressure supply means. In a four-wheel drive vehicle including a fluid pressure drive means having a fluid pressure motor that is supplied with a working fluid and rotates, a working fluid pressure from the fluid pressure supply means to the fluid pressure drive means is accumulated in a pressure accumulation means during braking. The four-wheel drive vehicle is characterized in that the working fluid pressure of the pressure accumulating means is supplied to the fluid pressure driving means during non-braking. 2. A fluid pressure supply means having a fluid pressure pump that rotates in conjunction with a drive axle driven by a main engine and discharges a working fluid, and a fluid pressure supply means associated with the axle of a driven wheel and from the fluid pressure supply means. In a four-wheel drive vehicle including a fluid pressure drive means having a fluid pressure motor that is supplied with and rotates a working fluid, a high pressure side pipe and a low pressure side pipe between the fluid pressure supply means and the fluid pressure drive means A switching valve for switching between the shutoff states, a switching valve control means for controlling the switching valve to be in a communication state or a shutoff state according to a running state of the vehicle, a pressure accumulating means for accumulating the working fluid pressure of the high pressure side pipe, When the switching valve is controlled to the communicating state, the working fluid pressure to the fluid pressure driving means is accumulated in the pressure accumulating means during braking, and the working fluid pressure of the pressure accumulating means is supplied to the fluid pressure driving means during non-braking. Regenerative system Four-wheel drive vehicle, characterized in that it comprises a means. 3. An accumulator connected to a high-pressure side pipe between the switching valve and the fluid pressure drive means, and a pressure-accumulation switching valve for disconnecting the accumulator and the high-pressure side pipe from each other. And a check valve that is provided between the pressure accumulation switching valve and the switching valve and allows only the flow from the fluid pressure supply means to the fluid pressure drive means. 3. The four-wheel drive vehicle according to claim 2, wherein the switching valve is controlled to a shut-off state, the pressure accumulation switching valve is controlled to a communication state, and the pressure accumulation switching valve is controlled to a communication state during non-braking. 4. A rotation speed detecting means for detecting the rotation speeds of the front and rear wheels, wherein the switching valve control means has a ratio of the rotation speeds of the front and rear wheels detected by the rotation speed detecting means to a preset threshold value. The four-wheel drive vehicle according to claim 2 or 3, wherein the switching valve is controlled to be in a communication state when the value is small. 5. An intake oil amount limiting valve for limiting the amount of intake oil to the fluid pressure pump, a pressure detecting device for detecting a working fluid pressure of the pressure accumulating device, and a braking condition detecting device for detecting a braking condition of a vehicle. The regenerative control means reduces the intake oil amount as the detected value of the pressure detecting means approaches a preset maximum accumulated pressure value when accumulating the working fluid pressure, and the braking state detecting means. The four-wheel drive vehicle according to any one of claims 2 to 4, wherein the intake oil amount is reduced as the detected value of (1) increases. 6. The four-wheel drive vehicle according to claim 5, wherein the braking state detecting means detects a stroke of a brake pedal. 7. The four-wheel drive vehicle according to claim 2, wherein the fluid pressure motor is a fluid pressure motor whose maximum capacity is variable. 8. A pressure detecting means for detecting a working fluid pressure of the pressure accumulating means, and a speed state detecting means for detecting a traveling speed state of the vehicle, wherein the regeneration control means detects the working fluid pressure of the pressure accumulating means. When supplying to the fluid pressure drive means, the maximum capacity is decreased as the detection value of the pressure detection means approaches a preset minimum pressure accumulation value, and the maximum capacity is decreased as the detection value of the speed state detection means increases. The four-wheel drive vehicle according to claim 7, wherein the four-wheel drive vehicle is adapted to be driven.