JPH09207594A - Four-wheel drive car - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a four-wheel drive car which includes a hydraulic transmission mechanism for transmitting a driving force and prevents steep drop of the driving torque at the time transfer is made from the four-wheel driving condition to the two-wheel driving condition. SOLUTION: A four-wheel drive car concerned is equipped with a hydraulic pump to rotate interlocking with the driving axle and hydraulic motor interlocking with the following axle. The hydraulic motor is a swash plate type axial piston motor to change the rate of discharge flow by changing the stroke of each piston 104 using a swash plate 105 inclining at a specified angle α, and is quipped with an energizing means 120. The energizing means is equipped with elastic members 126a, 126c to lower the reactive force given to provide a large energing force for giving a reactive force to the piston through the swash plate when the piston stroke is large and provides a smaller energizing force with a smaller piston stroke to sink the reactive force to be given to the piston.

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 A four-wheel drive vehicle having improved running performance on rough roads, rough terrain, etc., is equipped with a propeller shaft and a differential device for distributing drive torque from a prime mover to a plurality of axles. Further, in recent four-wheel drive vehicles, in order to distribute the driving force according to changes in the road surface condition, a viscous coupling or clutch is used between the drive shafts to make the distribution ratio of the driving force variable. doing. However, a four-wheel drive vehicle that variably controls the driving force distribution by such a mechanical system is likely to have a complicated device structure, and a propeller shaft passing under the floor of the vehicle body and a differential limiting device between axles are required. Therefore, the weight increases, which may hinder the miniaturization and weight reduction of the vehicle body.

As a solution to such a problem, for example, a prior application technique described in Japanese Patent Application No. 6-262639 previously proposed by the present applicant is known. This prior application technique is driven by a main engine. Drive axle, a fluid pressure pump that rotates in conjunction with the drive axle, a swash plate type variable displacement motor that is interlocked with the driven axle and that includes a swash plate as capacity changing means, and a discharge port of the fluid pressure pump. And a first flow path communicating with the suction port of the variable displacement motor, a second flow path communicating with the suction port of the fluid pressure pump and the discharge port of the variable displacement motor, and the capacity of the variable displacement motor is reduced. And a biasing means for driving the swash plate in a direction.

In the swash plate type variable displacement motor, as shown in FIG. 9, a cylinder block 2 is coaxially connected to a motor rotating shaft 1, and the cylinder block 2 is parallel to the motor rotating shaft 1. The bores 2a are formed at equal intervals along the rotation direction of the cylinder block 2. A piston 3 is arranged in each bore 2a, and a swash plate 4 is arranged at a position facing the tip of the piston 3 so as to swing up to a predetermined inclination angle α. The swash plate 4 restricts the stroke of the piston 3 pushed out from the bore 2a.
In addition, each of the bores 2a in which the pistons 3 are arranged has the valve plate 5
The working fluid suction port 6a and the working fluid return port 6b can be alternately communicated via the.

The above-mentioned urging means 7 includes a control piston 7b arranged in the cylinder chamber 7a and a spring arranged in the cylinder chamber 7a so as to urge the control piston 7b toward the swash plate 4 side. The member 7c, a communication passage 7d that communicates the cylinder chamber 7a and the low pressure portion, and a throttle 7e interposed in the communication passage 7d are provided. The member indicated by reference numeral 8 in FIG. 9 is a stopper that sets the maximum value of the inclination angle α of the swash plate 4.

In the four-wheel drive vehicle having the above structure, when the rotational speed of the drive shaft is higher than the rotational speed of the driven axle and four-wheel drive is required, the discharge flow rate of the fluid pressure pump is that of the variable displacement motor. The discharge flow rate is exceeded and the working fluid suction port 6a through the bore 2a
Since the high-pressure hydraulic oil is supplied to the inside, a torque corresponding to the high-pressure hydraulic oil is generated in the motor rotating shaft 1, and the drive torque is distributed to the driven axle to set the four-wheel drive traveling state.

[0007]

By the way, when the driving torque distributed to the driven axle suddenly drops in the transition from the above-mentioned four-wheel drive traveling state to the two-wheel drive traveling state, the drive shaft is correspondingly reduced in amount. A sudden increase in the transmission torque may increase the idling (slip) of the drive wheels, giving the driver a feeling of strangeness. Further, even when the vehicle shifts from the two-wheel drive traveling state to the four-wheel drive traveling state, if the rise of the drive torque distribution to the driven axle is slow, the driver may feel uncomfortable.

Therefore, by adjusting the spring force of the spring member 7c, which is a constituent member of the urging means 7, it is possible to eliminate a sudden drop or slow rise of the drive torque. That is, the spring member 7c always applies a biasing force to the swash plate 4 in a direction in which the inclination angle α decreases.
The spring member 7c having a strong spring force is used.
When a strong urging force is applied to the swash plate 4 from the control piston 7b, a reaction force (a reaction force corresponding to the strong urging force) acts on the piston 3 via the swash plate 4, and the displacement volume in the bore 2a decreases. As a result, the pressure of the hydraulic oil rises, so that the drive torque is distributed to the driven axle side by the generation of the drive torque of the motor rotating shaft 1, that is, the pre-torque is transmitted to the driven axle side.

[0009] range of the vehicle speed of "0" ~V ₁ shown in the horizontal axis of FIG. 10 is a low speed area in need of four-wheel drive, V
Vehicle speeds higher than ₂ are in the high-speed range where four-wheel drive is not required, but as described above, when the spring member 7c having a strong spring force is used, four-wheel drive is performed (the solid line in FIG. 10 is distributed to the driven axles). The drive torque of the driven axle gradually decreases as shown by the alternate long and short dash line in the figure, thereby preventing a rapid increase in the torque transmitted to the drive axle. The driver will not feel discomfort.

However, when the spring member 7c having a strong spring force is used, pre-torque is generated on the driven axle side even in the high speed region as shown in the region Te in the figure, and the pulsation of the working fluid and the noise vibration due to the gears. It is disadvantageous in terms of fuel consumption and temperature rise of working fluid. Further, when the spring member 7c having a weak spring force is used, noise vibration, fuel consumption in a high speed region, fuel consumption, etc. when shifting from a four-wheel drive traveling state to a two-wheel drive traveling state.
Although it is possible to solve the temperature rise of the working fluid, as shown by the two-dot chain line in the figure, the drive torque of the driven axle drastically drops, and the driven torque of the driven axle drastically drops and the start-up delay is slow. There is no solution to this.

Therefore, the present invention has been made by paying attention to the unsolved problem of the above-mentioned prior art, in which the driving torque of the driven axle is rapidly changed when the four-wheel drive traveling state is changed to the two-wheel drive traveling state. Of the driving torque of the driven axle at the time of shifting from the two-wheel drive running state to the four-wheel drive running state, and the noise vibration in the high-speed range that does not require the four-wheel drive running state. , Fuel consumption,
An object of the present invention is to provide a four-wheel drive vehicle capable of improving the temperature rise of working fluid.

[0012]

In order to achieve the above object, a four-wheel drive vehicle according to a first aspect of the present invention comprises a drive axle driven by a prime mover and a fluid pressure pump rotating in association with the drive axle. A fluid pressure motor that works with the driven axle; a first flow path that connects the discharge port of the fluid pressure pump and the suction port of the fluid pressure motor; and the suction port of the fluid pressure pump and the fluid pressure motor. A second flow path communicating with the discharge port, the fluid pressure motor is a swash plate type axial piston motor, and a cylinder block that is connected to a motor rotation shaft to rotate and is parallel to the rotation shaft and along the rotation direction. In a four-wheel drive vehicle in which a plurality of bores are formed, the piston is housed in each bore, and the discharge flow rate is changed by changing the stroke of each piston by a swash plate inclined at a predetermined inclination angle, The fluid pressure motor is provided with an urging means for applying an urging force to the swash plate in a direction in which the inclination angle of the swash plate decreases. When the stroke of the piston is large, a large urging force that gives a reaction force to the piston via the swash plate becomes large, and as the stroke angle of the swash plate decreases and the stroke of the piston becomes smaller, a smaller gradual force is applied. It was set so that the reaction force acting on the piston and applied to the piston would decrease.

According to a second aspect of the present invention, in the four-wheel drive vehicle according to the first aspect, the swash plate has the urging force characteristic of the urging means in a high-speed traveling range where four-wheel drive traveling is not required. The four-wheel drive vehicle according to claim 1, wherein the four-wheel drive vehicle is set so as to have a small biasing force that does not apply a reaction force to the piston via the. The invention according to claim 3 is the four-wheel drive vehicle according to claim 1 or 2, wherein the biasing means is
A cylinder chamber that is parallel to the rotation axis and opens toward the swash plate, a sliding member that is slidably disposed in the cylinder chamber, and has a tip end abutting against the swash plate, and the sliding member. At least two elastic members housed in the cylinder chamber so that the urging force acting on the swash plate is aligned, and an urging force restricting mechanism for restricting the urging force of any one of the elastic members. Is increased and the stroke of the piston is large, all the biasing forces of the plurality of elastic members are applied to the sliding member, and the inclination angle of the swash plate is decreased to reduce the stroke of the piston to a predetermined value. When it becomes small, only the biasing force of the specific elastic member acts on the sliding member by the biasing force restricting mechanism.

Further, the invention according to claim 4 is the same as the invention according to claim 3.
In the invention described above, the elastic member is composed of at least two coil springs having different coil diameters, and the coil axis is made to coincide with each other, and the coil spring having a small diameter is housed in the cylinder chamber while being loosely inserted into the coil spring having a large diameter.
The biasing force restricting mechanism restricts the extension operation of the large-diameter coil spring when the inclination angle of the swash plate decreases and the stroke of the piston decreases to a predetermined value.

[0015]

According to the first aspect of the present invention, when the vehicle travels in the four-wheel drive state, the discharge flow rate of the fluid pressure pump is changed by the fluid pressure due to the difference in the rotational speed between the drive axle and the driven axle. When the fluid discharge motor exceeds the discharge flow rate of the motor, the resistance of the working fluid acts as a load and torque is generated while the tilt angle of the swash plate increases near the maximum angle, and the drive torque is transmitted to the driven shaft side.

When the rotational speed difference between the drive axle and the driven axle decreases and the vehicle shifts from the four-wheel drive state to the two-wheel drive state, the inclination angle of the swash plate of the fluid pressure motor gradually decreases. However, when the inclination angle of the swash plate increases and the stroke of the piston is large, the urging means of the present invention exerts a large urging force that gives a reaction force to the piston via the swash plate, Since the urging force is set to decrease gradually when the inclination angle of the plate decreases, the displacement volume in the bore decreases and the working fluid pressure rises, generating torque on the motor rotating shaft and driving shaft side. Transmit pre-torque to. As a result, the drive torque of the driven axle does not decrease gently, so that it is possible to prevent a sudden drop in drive torque when the vehicle shifts from the four-wheel drive state to the two-wheel drive state. Also, by transmitting the pre-torque to the driven axle side,
Even when the vehicle shifts from the two-wheel drive state to the four-wheel drive state, the drive torque rises quickly.

Therefore, when the vehicle shifts from the four-wheel drive state to the two-wheel drive state, the slip does not increase due to the sudden increase of the transmission torque to the drive shaft, and when the vehicle shifts from the two-wheel drive state to the four-wheel drive state. Since the drive torque is smoothly transmitted to the driven shaft side, the driver does not feel uncomfortable. Further, the invention according to claim 2 can obtain the effect according to claim 1, and in a high-speed traveling region where four-wheel drive traveling is not required, a small attachment that does not apply a reaction force to the piston via the swash plate is provided. Since the characteristic of the urging means is set so as to exert a force, the pressure of the working fluid in the bore does not rise and torque is not generated on the motor rotating shaft. Therefore, in the high-speed traveling region, the pre-torque is not transmitted to the driven axle side, so that vibration due to pulsation of the working fluid hardly occurs, noise and vibration on the floor inside the vehicle can be suppressed, fuel consumption deterioration and working fluid temperature It is possible to prevent the rise.

Further, the invention according to claim 3 can obtain the effect according to claim 1 or 2, and at least two elastic members are used as members for exerting a biasing force on the swash plate. By controlling the urging state of No. 2 by the urging force regulating mechanism, the urging force is applied in stages from the time when the piston stroke is large to the time when the piston stroke is small, so that pre-torque can be generated with high accuracy. it can.

Further, the invention according to claim 4 can obtain the effect according to claim 3, and since the elastic member is composed of at least two coil springs having different coil diameters, a simple device structure can be obtained. Can be provided.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a first embodiment when the present invention is applied to a four-wheel drive vehicle based on a front-wheel drive vehicle. In the figure, 10 is an engine as a prime mover. The rotational driving force of 10 is input to the front wheel side differential device 13 via the transmission 12, and the front wheels 15 are connected to the output side of the differential device 13 via the front axle 14 as a drive axle.

In the front wheel side differential device 13, the ring gear 13b formed in the differential gear case 13a meshes with the gear 12a connected to the output side of the transmission 12 to be rotationally driven, and is formed in the differential gear case 13a. The pinion 13 on the pair of pinion shafts 13c
d is attached, a pair of side gears 13e mesh with these pinions 13d, and the front axle 14 as a first drive shaft is connected to these side gears 13e.

Further, the differential gear case 13
A ring gear 1 formed in a in parallel with the ring gear 13b
3f is a rotary shaft 16 of a suction throttle type piston pump 16 as a fluid pressure pump via a gear 13g meshing with this.
a. This suction throttle type piston pump 1
6, the suction port 16b is connected to the strainer 17a arranged in the reservoir tank 17, and is connected to the tank port T of the 2-position 4-port electromagnetic directional control valve 19 through the low-pressure pipe 18L as a flow path. And outlet 1
6c is connected to the pump port P of the electromagnetic directional control valve 19 for forward / backward switching through a high pressure pipe 18H as a flow path.

Here, the suction throttle type piston pump 16
Depending on the direction of rotation of the rotary shaft 16a
Is not changed, and the discharge flow rate is
Curve L ₁As shown by, the vehicle speed changes from "0" to a predetermined value Va.
In the meantime, it will increase in proportion to the increase in vehicle speed,
Maximum discharge flow rate Q above the constant value Va_maxTo saturate with
Is set.

In the electromagnetic directional control valve 19 for switching between forward and reverse, the pump port P communicates with the output port A and the tank port T communicates with the output port B at the normal position where the solenoid 19a is in the non-energized state. Pump port P to output port B at the offset position which is in the energized state,
The tank port T is communicated with the output port A, and the output ports A and B flow in and out of a swash plate type variable displacement motor (hereinafter abbreviated as variable displacement motor) 20 as a fluid pressure motor.
Connected to the outflow ports 20a and 20b, the high pressure oil in the high pressure pipe 18H is connected to the inflow port 20a of the variable displacement motor 20 and the low pressure pipe 18L is connected to the outflow port 20 in the normal position.
The rotary shaft 20c is driven to rotate in a forward direction, for example, in a clockwise direction when viewed from the left side surface while being communicated with b.
18 L of low-pressure piping to the outflow port 20b of the inflow port 2
The rotation shaft 20c is driven to rotate in a counterclockwise direction when viewed from the left side surface, for example, in the rotation direction during forward traveling in communication with 0a.

The electromagnetic directional control valve 19 is built in the variable displacement motor 20 so that the output ports A and B do not have to be connected to the inflow / outflow port 20 of the variable displacement motor 20.
It is connected to a and 20b. In addition, the electromagnetic directional control valve 1
Although the solenoid 19a is energized, the solenoid 19a is connected to the DC power source 19c via the shift position detection switch 19b which is turned on when the solenoid 19a selects the backward movement by the shift lever (not shown), so that the vehicle is traveling forward. It is controlled to be in the non-energized state and to be in the energized state when traveling backward.

Further, between the suction port 16b and the discharge port 16c of the suction throttle type piston pump 16, a relief valve 21 for limiting the upper limit of the discharge pressure of the suction throttle type piston pump 16 is inserted as a torque limiting means. . Further, the communication pipe 22A that communicates between the high pressure pipe 18H and the low pressure pipe 18L between the suction throttle type piston pump 16 and the electromagnetic directional control valve 19 includes a high pressure pipe 18L from the low pressure pipe 18L side.
A check valve 23 that allows fluid flow to the H side is inserted, and a fixed orifice 24 is connected in parallel with the check valve 23 to a communication pipe 22B arranged in parallel with the communication pipe 22A. There is.

On the other hand, the rotary shaft 20c of the variable displacement motor 20.
A gear 20d is attached to the gear 20d, and a ring gear 27b formed in a differential gear case 27a of the rear wheel side differential 27 is meshed with the gear 20d. The rear wheel side differential device 27 has substantially the same configuration as the front wheel side differential device 3 described above, and has a differential gear case 27a.
A pinion 27d is attached to a pair of pinion shafts 27c formed inside, a pair of side gears 27e meshes with these pinion 27d, a rear axle 28 is connected to these side gears 27e, and a rear wheel 29 is connected to this rear axle 28. Has been done.

Next, FIGS. 3 and 4 show a concrete structure of the variable displacement motor 20 described above.
In the variable displacement motor 20, a rotary shaft 20c supported by a bearing 101 is rotatably arranged in a pump housing 100, and a cylindrical cylinder block 102 is coaxially fixed to the outer periphery of the rotary shaft 20c. ing. Further, the cylinder block 102 is formed with a plurality of bores 103 parallel to the rotating shaft 20c at predetermined intervals in the circumferential direction, and a piston 104 is housed in each bore 103. The cylinder block 102 shown in FIG.
A swash plate 105 is swingably disposed at a position facing the right end surface of the.

This swash plate 105 has a cylindrical portion 105a and a protruding portion 105b protruding from the upper end of the cylindrical portion 105a in FIG.
And a shoe holder 107 that locks the shoe 106 engaged with the end of each piston 104 so as to be slidable in the circumferential direction. Then, the shoe holder 107 is attached to the swash plate 1 via the needle 109 by the pressing spring 108.
It is pressed to the 05 side. Further, the position indicated by reference symbol P in FIG. 3 is the swing shaft of the swash plate 105, and this swing shaft P is provided at a position offset by a predetermined amount ε in the direction orthogonal to the axis of the rotary shaft 20c. The swash plate 105 swings about the swing axis P up to a predetermined tilt angle α. In addition, a stopper 110 is provided in the pump housing 100 at a position facing the swash plate 105.
When 5 comes into contact with this stopper 110, swing is restricted,
The maximum inclination angle α _max of the swash plate 105 is set.

The left end surface of the cylinder block 102 in FIG. 3 is in sliding contact with the valve plate 111 fixed to the pump housing 100. This valve plate 11
As shown in FIG. 4, an inflow port 20a (an outflow port when traveling in reverse) and an outflow port 20b (an inflow port when traveling in reverse) are formed in 1, and the inflow port 20a and the outflow port 20b accommodate the piston 104. Each of the bores 103 is in communication with each other via a communication hole 112.

When traveling forward, the inflow port 20
The hydraulic oil is supplied from the a into the bore 103 and the piston 10
4 is pushed out from the bore 103, an axial force proportional to the working hydraulic pressure is transmitted to the swash plate 105, and the cylinder block 102 is rotated by the reaction force to transmit the driving torque to the rotary shaft 20c. Also, when traveling backwards,
Hydraulic oil is supplied into the bore 103 from the outflow port 20b, the piston 104 is pushed out of the bore 103, an axial force proportional to the hydraulic pressure is transmitted to the swash plate 105, and the reaction force causes the cylinder block 102 to rotate in the reverse direction. Rotating shaft 20
The drive torque is transmitted to c.

The discharge flow rate of the variable displacement motor 20 increases as the tilt angle α of the swash plate 105 increases, and the swash plate 105 comes into contact with the stopper 110 so that the maximum tilt angle α _max.
The maximum discharge flow rate is reached at this time, but the flow rate characteristic is from the vehicle speed "0" to a predetermined value V ₁ (V ₁ <Va) as shown by the characteristic curve L ₂ in FIG. Then, it increases in proportion to the increase of the vehicle speed, and since the suction throttle type piston pump 16 is saturated at the maximum discharge flow rate Q _max at the predetermined value V ₁ or more, this maximum discharge flow rate Q _max is maintained. Here, "0" range of the vehicle speed of ~V ₁ is a vehicle speed region that requires four-wheel drive.

The swash plate 105, which is swingably arranged in the hoop housing 100, is urged by the urging means 120 in the direction in which the inclination angle α becomes smaller. That is, the urging means 120, as shown in FIG.
A cylinder-shaped cylinder chamber 122 that opens parallel to c toward the swash plate 105, and a control piston as a sliding member that is slidably disposed in the cylinder chamber 122 and has a tip end contacting the swash plate 105. 124 and the cylinder chamber 122
The control piston 124 is housed in the swash plate 105.
Biasing member 126 as a biasing force regulating mechanism for biasing the side
And a communication pipe 128 that connects the cylinder chamber 122 and the low-pressure pipe 8L.

The cylinder chamber 122 is composed of a housing chamber 122a for housing the urging member 126, and a piston chamber 122b having an inner peripheral wall whose diameter is smaller than that of the housing chamber 122a and in which the control piston 124 reciprocates. An engagement wall 122c as a biasing force regulating mechanism is formed at the boundary between the accommodation chamber 122a and the piston chamber 122b.

Further, the urging member 126 is provided in the accommodation chamber 122a.
Has a first coil spring 126a that is disposed between the end surface of the control piston 124 and the base end portion of the control piston 124 and biases the control piston 124 toward the swash plate 105, and has an outer peripheral diameter that is substantially the same as the inner peripheral diameter of the housing chamber 122. In addition, the ring-shaped locking member 12 disposed in the accommodation chamber 122a has an inner diameter smaller than the outer diameter of the base end of the control piston 124.
6b, the first coil spring 126a is inserted between the end surface of the accommodation chamber 122a and the locking member 126b, and biases the control piston 124 toward the swash plate 105 side through the locking member 126b. 2 coil spring 126c
It is composed of

In the urging means 120, as shown in FIG.
When moved to 2a, both the first and second coil springs 126a and 126c exert an urging force on the control piston 124. Further, as shown in FIG. 3, when the proximal end side of the control piston 124 moves to the piston chamber 122b, the locking member 126b contacts the engaging wall 122c, and the locking member 126b and the proximal end side of the control piston 124 are separated from each other. Therefore, only the first coil spring 126a exerts an urging force on the control piston 124.

Then, the first and second coil springs 126
The urging force of a and 126c is the control piston 124
Stroke change, that is, the flow rate characteristic of the variable displacement motor 20.
It acts according to the change of the inclination angle α of the swash plate 105 due to the sex.
The four-wheel drive is set as shown in FIG.
Vehicle speed "0" to V₁(V₁<Va)
In the low speed region, the first and second coil springs 126a, 1a
26c both act on the urging force (state shown in FIG. 4),
Vehicle speed V that does not require four-wheel drive_Two(V _Two> V
a> V₁) In the above high speed region, the first coil spring 126
Only a is set to exert a biasing force (see FIG. 3).
State).

Next, the operation of the above embodiment will be described.
Now, when the vehicle stops on a high friction coefficient road such as a dry road surface and starts forward traveling in a braking state in which the engine 10 is in an idling state, the shift lever is switched to the forward traveling side so that the vehicle can start. To do. At this time, since the shift position detection switch 19b on the reverse traveling side is kept in the off state, the solenoid 19a of the forward / reverse switching electromagnetic directional control valve 19 is kept in the non-energized state, and the switching position is the normal position shown in FIG. To continue. In this state, by releasing the brake pedal and depressing the accelerator pedal, the rotational force of the engine 10 is transmitted to the front wheel side differential device 13 via the transmission 12, and the front wheel side operating device 13 operates the front wheel 15 to operate. The vehicle is started to travel forward by being rotationally driven in the forward direction.

At this time, the rotary shaft 16a of the suction throttle piston pump 16 is rotationally driven, so that the suction throttle piston pump 16 discharges hydraulic fluid at a discharge flow rate according to the rotational speed. This discharged hydraulic oil is
It is sucked into the inflow port 20a of the variable displacement motor 20 through the high pressure pipe 18H and the forward / reverse switching electromagnetic directional switching valve 19, and is discharged from the outflow port 20b.

[0040] Here, when the vehicle runs at a low speed region ( "0" speed of ~V _1), the discharge flow rate of the suction throttle type piston pump 16 and a variable displacement motor 20, as shown in FIG. 2 Since the discharge flow rate of the variable displacement motor 20 is set to be larger than that of the suction throttle piston pump 16, in a state where the rear wheel 29 and the front wheel 15 are rotationally driven at the same rotational speed during normal traveling, As shown in FIG. 6, the inclination angle α of the swash plate 105 is an inclination angle α ₁ smaller than the maximum inclination angle α _max .

At this time, the biasing means 120 of the variable displacement motor 20 has the first and second coil springs 126a and 126c.
Exerts an urging force on the control piston 124, and the control piston 124 having received this urging force presses the swash plate 105 in a direction in which the inclination angle α decreases. The swash plate 105, which receives the urging force of the first and second coil springs 126 a and 126 c, acts a reaction force on the piston 104 to cause the bore 10 to move.
Since the displacement volume in 3 is reduced, the hydraulic pressure in the bore 103 rises and the cylinder block 102 rotates,
A torque having a magnitude corresponding to the biasing force of the first and second coil springs 126a and 126c is generated on the rotating shaft 20c. Thus, as shown in FIG. 5, in the low speed region ( "0" speed of ~V _1), while allocating a drive torque to the rear wheels 29, i.e., a state that communicated pretorque the rear wheel 29 side Become.

When the vehicle travels in the medium speed range of the vehicle speeds V _{1 to} V ₂ , as shown in FIG. 2, the discharge flow rates of the suction throttle piston pump 16 and the variable displacement motor 20 are saturated with each other. However, the inclination angle α of the swash plate 105 becomes smaller as the number of rotations of the rotating shaft 20c increases. At this time, the biasing force of the first and second coil springs 126a and 126c, which exerts the biasing force on the control piston 124, gradually decreases due to their extension operation, and the torque having a magnitude corresponding to the biasing force is gradually reduced. Occurs on the rotating shaft 20c, as shown in the region of vehicle speeds V _{1 to} V _{2 in} FIG.
The pre-torque transmitted to the rear wheel 29 side is gradually increased or decreased.

Then, at the time when the vehicle speed reaches V ₂ , the locking member 126b, which has been moving together with the second coil spring 126c in the accommodation chamber 122a, comes into contact with the engagement wall 122c, so that the second coil spring 126c is extended. Stop. As a result, the first coil spring 12 is attached to the control piston 124.
Only the biasing force of 6a acts, and the first coil spring 126
The urging force of “a” is a force that presses the swash plate 105 so that the swash plate 105 is always in contact with the tip end portion of the piston 104, so that the line pressure on the inflow port 20a side does not rise. Therefore, since the rotary shaft 20c hardly generates torque, the pre-torque is hardly transmitted to the rear wheel 29 side as shown in the region where the vehicle speed exceeds V _{2 in} FIG.

As described above, when the vehicle travels on the high friction coefficient road, the vehicle travels in a state in which the pre-torque is transmitted to the rear wheel 29 side from the start to the medium speed range, and the rear wheel 2 operates in the high speed range.
It runs in a two-wheel drive state with almost no pre-torque transmitted to the 9 side. Next, when the vehicle starts on a low friction coefficient road such as an icy road or a snowfall road, as described above, the front wheels 15 are first driven to rotate, but since the road is a low friction coefficient road, the front wheels 15 slip. Therefore, a difference in rotation speed between the front wheels 15 and the rear wheels 29 is generated so that the front wheels 15 have a high rotation speed. As a result, the discharge flow rate of the suction throttle type piston pump 16 exceeds the discharge flow rate of the variable displacement motor 20, so the variable displacement motor 20 increases the inclination angle α of the swash plate 105 so that the discharge amount becomes the same. When the swash plate 105 contacts the stopper 110, the maximum inclination angle α _max is reached.

Further, when the rotational speed difference between the front wheel 15 and the rear wheel 29 becomes large, the suction throttle type piston pump 16
Discharge flow rate from the variable displacement motor 20 exceeds the discharge flow rate of the variable displacement motor 20, the resistance of the variable displacement motor 20 becomes a load and the high-pressure pipe 1
The hydraulic pressure of 8H rises. In this state, the variable displacement motor 20 generates a drive torque according to the supply pressure of the high-pressure pipe 18H, and transmits this drive torque to the rear wheels 29 via the rear wheel side differential device 27, so that the vehicle has four wheels. Drive forward with the wheels driven.

Further, when the slip of the front wheels 15 is reduced from this four-wheel drive state and the difference in rotational speed between the front wheels 15 and the rear wheels 29 becomes small, the suction throttle piston pump 16 supplies the variable displacement motor 20 with an operation. Since the difference in the amount of oil discharged is reduced, the pre-torque in the medium speed traveling range described above is transmitted. That is, as shown in FIG. 2, the suction throttle type piston pump 16 and the variable displacement motor 20 saturate with each other, and the swash plate 105 increases as the rotation speed of the rotary shaft 20c increases.
Since the pre-torque is transmitted to the rear wheel 29 side by the first and second coil springs 126a and 126c acting on the control piston 124 as the inclination angle α of the rear wheel 29 decreases, The drive torque gradually decreases, and a sudden decrease in drive torque when the vehicle transitions from the four-wheel drive state to the two-wheel drive state is prevented.

Further, since the pre-torque is transmitted to the rear wheel 29 side, it is possible to accelerate the rise of the drive torque when the vehicle shifts from the two-wheel drive state to the four-wheel drive state. Next, when the vehicle is moved in the reverse direction, the shift position is switched to the reverse position to turn on the shift position detection switch 19b, so that the solenoid 19a of the electromagnetic directional control valve 19 is energized and the switching position is in the normal position. Switch from position to offset position. As a result, the hydraulic oil inside the high-pressure pipe 18H is supplied to the outflow port 20b of the variable displacement motor 20, and the hydraulic oil discharged from the inflow port 20a is returned to the low-pressure pipe 18L side, whereby the rotary shaft 20c of the variable displacement motor 20 is rotated. Is reversed from that during forward traveling, and the rear wheel 29 is rotated in reverse. Therefore, when the vehicle is moving backward, the same as when moving forward, the pre-torque is transmitted to the rear wheel 29 side, the front wheel 15 slips, and the front wheel 15 rotates at a high speed between the front wheel 15 and the rear wheel 29. When there is a difference in the number of revolutions, the hydraulic pressure in the high-pressure pipe 18H rises, and the drive torque is transmitted to the rear wheel 29.

[0048] Thus, according to a first embodiment of the above-described configuration, in the low speed range within the range the vehicle speed is "0" ~V _2, the first acting a biasing force to the control piston 124
And the rear wheel 2 by the second coil springs 126a and 126c.
Since the pre-torque is transmitted to the 9 side, even if the four-wheel drive traveling state is changed to the two-wheel drive traveling state, the drive torque on the rear wheel 29 side is gradually reduced to reduce the transmission torque of the front axle 14. The sudden increase is prevented, the slip is not increased, and the driver does not feel uncomfortable.

Also, when the two-wheel drive traveling state is changed to the four-wheel drive traveling state in the medium and low speed range, the rear wheels 2
Since the pre-torque is transmitted to the 9 side, the rise of the drive torque can be accelerated and the driver does not feel uncomfortable. Further, in the high and low speed region where the vehicle speed exceeds V ₂ , the locking member 126b that has been moving together with the second coil spring 126c in the accommodation chamber 122a comes into contact with the engagement wall 122c and the extension operation of the second coil spring 126c is stopped. ,
Since only a small biasing force of the first coil spring 126a acts on the swash plate 105, the rotary shaft 20c produces almost no torque. Therefore, the vibration of the hydraulic oil due to the flow arterial movement hardly occurs, so that the noise and vibration to the floor inside the vehicle can be suppressed, the pressure loss due to the piping resistance etc. is reduced, and the fuel consumption is deteriorated and the temperature of the hydraulic oil is increased. Can be prevented.

The biasing means 120 of this embodiment is
Since the two types of coil springs 126a and 126c and the ring-shaped locking member 126b that abuts on the engagement wall 122c of the cylinder chamber 122 are used, the urging force toward the swash plate 105 can be changed stepwise. It is possible to provide a simple device. Next, FIG. 7 and FIG. 8 show a second embodiment of the present invention. The same components as those shown in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

In the present embodiment, the swash plate 131 is in the forward direction (the direction with the inclination angle of α _A in FIG. 8) and the reverse direction (the direction in which the inclination angle is α _A in FIG. 8).
_The variable displacement motor 130 that swings in both directions (the direction with the inclination angle of _B ) is adopted, and the high pressure pipe 18H and the low pressure pipe 18L are used without using the electromagnetic directional control valve 9 for switching between forward and reverse of the first embodiment. The electromagnetic directional control valve 132 is connected to the electromagnetic directional control valve 132 to which high-pressure P _H and low-pressure P _L working fluid is supplied, and the output ports A ₁ , A _{2 of the} electromagnetic directional control valve 132 are used.
The urging means 134 for forward movement and the urging means 136 for rearward movement are connected.

Further, the forward biasing means 134 is formed in parallel with the rotary shaft 130c and has the first and second coil springs 1
A housing chamber 134c for housing 34a and 134b, and a piston chamber 134 having an inner peripheral wall having a diameter reduced from the housing chamber 134c for reciprocating the control piston 134h.
d, an engagement wall 134e formed at the boundary between the accommodating chamber 134c and the piston chamber 134d, a locking member 134f disposed in the accommodating chamber 134c, the output port A ₁ of the electromagnetic directional control valve and the accommodating chamber 134c. And a communication pipe 134g that communicates with each other. Further, the reverse biasing means 136 also includes the same components.

[0053] Then, during forward traveling, maintaining the solenoid 132a deenergized state of the solenoid directional control valve 132, since the switching position indicates the normal position shown in FIG. 7, the hydraulic oil of high pressure P _H is the directional control valve 132 Biasing means 1 for forward movement
When the swash plate 131 is supplied to the valve 34 and exerts an urging force on the control piston 134h, the swash plate 131 is inclined to the forward inclination angle α _A. When shifting from the four-wheel drive traveling state to the two-wheel drive traveling state during the forward traveling, the rear wheel 29 is driven by the first and second coil springs 134a and 134b which exert the biasing force on the control piston 134h in the medium and low speed region. Since the pre-torque is transmitted to the rear side, the rear wheel 29
Side drive torque is gradually reduced to the front axle 14
The sudden increase in the transmission torque to the vehicle is prevented, the slip is not increased, and the driver does not feel uncomfortable. In addition, since the pre-torque is transmitted to the rear wheel 29 side even when the two-wheel drive traveling state is changed to the four-wheel drive traveling state in the medium and low speed region, the driving torque can be quickly started up, and the driver feels uncomfortable. Never give. Further, in the high speed region, the second coil spring 134b is accommodated in the accommodation chamber 134c.
The locking member 134f that was moving together with the engaging wall 134
Since the extension operation of the second coil spring 134b is stopped by contacting e, and only a small biasing force of the first coil spring 134a acts on the swash plate 131, the rotating shaft 130c generates almost no torque, and noise on the floor inside the vehicle is reduced. It is possible to solve the problems of vibration, fuel consumption, and temperature rise of hydraulic oil.

When traveling in reverse, the electromagnetic directional control valve 1
Since the switching position becomes the offset position due to the energization state of the solenoid 132a of 32, the hydraulic oil of high pressure P _H is supplied from the electromagnetic directional switching valve 132 to the reverse biasing means 136 to exert a biasing force on the control piston 136h. , The swash plate 131 is tilted at the tilt angle α _B in the opposite direction. Even when the four-wheel drive traveling state is shifted to the two-wheel drive traveling state during the reverse traveling, the control piston 136
First and second coil springs 13 that apply a biasing force to h
Since the pre-torque is transmitted to the rear wheel 29 side by 6a and 136b, the driving torque on the rear wheel 29 side is gradually reduced, and the driver does not feel uncomfortable.

Further, in this embodiment, since two kinds of biasing means 134 and 136 are used for forward movement and backward movement, the second coil spring 134 used for them is used.
If b and 136b have different spring forces, the pre-torque to the rear wheel 29 side during forward traveling and backward traveling can be changed appropriately. In addition, in the present embodiment, a small electromagnetic directional control valve 132 capable of switching between forward traveling and reverse traveling is used for the control piston 134h by using a working fluid that can introduce Pitorro pressure. Therefore, the weight of the device can be reduced.

In the first and second embodiments, the biasing means 1
The coil spring 12 is used as a biasing member for 20,134,136.
6a, 126c, 134a, 134b, 136a, 13
Although 6b is used, the gist of the present invention is not limited to this, and the same action and effect can be obtained by using another elastic member such as a rubber material or a disc spring. Further, in each of the embodiments, two types of coil springs act as urging forces up to the medium and low speed regions, and one type of coil spring acts in the high speed region, but the gist of the present invention is not limited to this. However, more coil springs may be used to increase the number of stages in which the biasing force acts.

In the first and second embodiments, the case where the rear wheel side differential device 27 is provided has been described, but the present invention is not limited to this, and the rear wheel differential device 27 is not limited to this.
Alternatively, instead of this, variable displacement motors may be individually provided on the left and right axles 28 of the left and right rear wheels 29.
Furthermore, in the above-described first embodiment, the case has been described in which the forward / reverse switching electromagnetic direction switching valve 19 is built in the variable displacement motor 20, but the present invention is not limited to this, and the outside of the variable displacement motor 20 is described. It may be installed separately.

In the first and second embodiments, the embodiment based on the front-wheel drive vehicle has been described. However, the present invention is not limited to this, and the embodiment based on the rear-wheel drive vehicle is also described. The same effect can be obtained.

[Brief description of drawings]

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

FIG. 2 is a characteristic diagram showing discharge flow rate characteristics of a fluid pressure pump and a fluid pressure motor applied to the present invention.

FIG. 3 is a cross-sectional view of a swash plate type axial piston motor applied to the first embodiment.

FIG. 4 is a conceptual diagram showing a mechanism of a swash plate type axial piston motor applied to the first embodiment.

FIG. 5 is a characteristic diagram showing a relationship between a change in the urging force of the urging means according to the present invention and a drive torque transmitted to the driven axle side.

FIG. 6 is a diagram showing a relationship between a vehicle speed and an inclination angle of a swash plate of a swash plate type axial piston motor.

FIG. 7 is a schematic configuration diagram showing a second embodiment of the present invention.

FIG. 8 is a conceptual diagram showing a mechanism of a swash plate type axial piston motor applied to the second embodiment.

FIG. 9 is a conceptual diagram showing a mechanism of a conventional swash plate type axial piston motor.

FIG. 10 is a characteristic diagram showing the relationship between changes in the urging force of the urging means of the conventional device and the drive torque transmitted to the driven axle side.

[Explanation of symbols]

10 Engine (Main Motor) 14 Front Axle (Drive Axle) 16, 36 Fluid Pump 28 Rear Axle (Driven Axle) 20, 130 Variable Capacity Motor (Fluid Pressure Motor, Swash Plate Axial Piston Motor) 18H High Pressure Piping (First Flow) 18L Low-pressure pipe (second flow path) 20c, 130c Rotating shaft (motor rotating shaft) 102 Cylinder block 103 Bore 104 Piston 105 Swash plate 120, 134, 136 Energizing means 122 Cylinder chamber 122c, 134e, 136e Engaging wall (Biasing force regulating mechanism) 124, 134h, 136h Control piston (sliding member) 126a, 134a, 136a First coil spring (elastic member) 126b, 134f, 136f Locking member (biasing force regulating mechanism) 126c, 134b, 136b 2-coil spring (elastic member)

Claims (4)

[Claims] 1. A drive axle driven by a prime mover,
A fluid pressure pump that rotates in conjunction with the drive axle; a fluid pressure motor that interlocks with the driven axle; a first flow path that connects the discharge port of the fluid pressure pump and the suction port of the fluid pressure motor; A cylinder block that includes a second flow path that connects the suction port of the fluid pressure pump and the discharge port of the fluid pressure motor, and uses the fluid pressure motor as a swash plate type axial piston motor, which is connected to a motor rotation shaft to rotate. , A plurality of bores are formed parallel to the rotation axis and along the rotation direction, the pistons are housed in the respective bores, and the stroke of each piston is changed by a swash plate tilted at a predetermined tilt angle to change the discharge flow rate. In this four-wheel drive vehicle, the fluid pressure motor is provided with a biasing means for applying a biasing force to the swash plate in a direction in which the inclination angle of the swash plate decreases, and the biasing force characteristic of the biasing means is provided. When the tilt angle of the swash plate is increased and the stroke of the piston is large, a large biasing force that gives a reaction force to the piston via the swash plate is obtained.
The four-wheel drive vehicle is set such that as the inclination angle of the swash plate decreases and the stroke of the piston becomes smaller, the urging force gradually becomes smaller and the reaction force applied to the piston decreases. 2. The urging force characteristic of the urging means is set to be a small urging force that does not apply a reaction force to the piston through the swash plate in a high-speed traveling region that does not require four-wheel drive traveling. The four-wheel drive vehicle according to claim 1, wherein 3. The biasing means is parallel to the rotation axis,
In addition, a cylinder chamber that opens toward the swash plate, a sliding member that is slidably disposed in the cylinder chamber and has its tip end abutting against the swash plate, and a direction in which an urging force acts on the sliding member. At least two that are matched and stored in the cylinder chamber
One elastic member and an urging force restricting mechanism that restricts an urging force of one of these elastic members, and when the inclination angle of the swash plate increases and the stroke of the piston is large, All the urging force acts on the sliding member, and when the inclination angle of the swash plate decreases and the stroke of the piston decreases to a predetermined value, the urging force restricting mechanism applies a specific elastic member. The four-wheel drive vehicle according to claim 1 or 2, wherein only a force acts on the sliding member. 4. The elastic member is constituted by at least two coil springs having different coil diameters, and the coil springs are housed in the cylinder chamber in a state in which a coil spring having a small diameter is loosely inserted in a coil spring having a large diameter. The urging force restricting mechanism restricts the extension operation of the large-diameter coil spring when the inclination angle of the swash plate decreases and the stroke of the piston decreases to a predetermined value. The four-wheel drive vehicle described.