JPH08310267A - Hydraulic driving gear - Google Patents

Abstract

PURPOSE: To distribute drive power to a plurality of drive shafts by arbitrary ratio with a simple constitution and high responsiveness, by providing a means of changing an initially set load relating to an energizing means of driving a capacity change means in the direction of decreasing a capacity of a variable displacement motor. CONSTITUTION: In an oil hydraulic motor, each piston 21 of a cylinder block 20 changes a displacement capacity in accordance with a tilt angle α of a swash plate 22, to drive a shaft 23 connected to a rear shaft. When a suction amount of the oil hydraulic motor is small generated relative to a delivery amount of an oil hydraulic pump, for instance, in the case of racing a front wheel with a rear wheel road-held, since a delivery pressure Pd rises, also a pilot pressure Pd applied to a piston 31 of controlling the swash plate 22 is increased, and the piston 31, while increasing the tilt angle αof the swash plate 22 against a spring 30, increases a displacement capacity of the oil hydraulic motor 8. When a solenoid 36 is driven to change an initially set load of the spring 30, a delivery pressure can be arbitrarily set. Accordingly, drive power of a prime mover can be distributed by arbitrary ratio to both the front/rear shafts.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic drive system for distributing power to a plurality of drive shafts of vehicles such as agricultural machines, construction machines and automobiles.

[0002]

2. Description of the Related Art Conventionally, in vehicles such as agricultural machines, construction machines, and automobiles, a drive device such as all-wheel drive or four-wheel drive has been adopted in order to improve the running performance on rough roads, rough terrain, etc. In such a drive device, a propeller shaft and a differential device are provided to distribute the drive force from one prime mover to a plurality of axles. 2. Description of the Related Art In recent years, in vehicles such as automobiles, in order to distribute the driving force according to changes in road surface conditions, it is becoming popular to use a viscous coupling or a clutch between drive shafts to make the distribution ratio of the driving force variable. . Such a mechanical drive device requires a control device for variably controlling the distribution of the driving force, which complicates the device and also requires a propeller shaft and a differential limiting device between axles. The weight also increases, and especially in automobiles, there is a problem that the propeller shaft penetrates under the floor of the vehicle body, which hinders downsizing and weight reduction of the vehicle body.To solve such a problem, it is connected to the prime mover or the drive shaft. 2. Description of the Related Art A hydraulic drive device that supplies pressure oil from a hydraulic pump to a hydraulic motor provided on each drive shaft and distributes the drive force to a plurality of drive shafts by the hydraulic motor has been conventionally known.

[0003]

By the way, in the above hydraulic drive, a variable displacement pump and a motor are combined,
The drive power distributed to each drive shaft is variably controlled by changing the capacity of the pump or motor.However, when one drive shaft idles from the stopped state of the axle or the low rotation region when the vehicle starts, other In order to change the driving force distributed to the driving shaft with high responsiveness, it is necessary to change the capacity of the pump or the motor in advance by an electric servo mechanism or the like.

However, such a servo mechanism has a problem that not only the structure is complicated but also the manufacturing cost is increased.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a hydraulic drive device which has a simple structure, can distribute a driving force to a plurality of drive shafts at an arbitrary ratio, and has high responsiveness.

[0006]

A first invention is a first drive shaft driven by a prime mover, a pump driven synchronously with the first drive shaft to supply pressure oil, and a second invention. A variable displacement motor which is connected to the drive shaft of the pump and which is driven according to the pressure oil from the pump and which has a capacity changing means, and supplies the pressure oil when the supply pressure from the pump exceeds a predetermined value. A relief valve for returning to the tank, a pressure responsive member for driving the capacity changing means in accordance with a hydraulic pressure from a predetermined hydraulic pressure source, and a capacity changing means driven by the pressure responsive member are regulated at a predetermined maximum capacity position of the motor. And a biasing means for driving the capacity changing means in a direction in which the capacity of the motor decreases, the hydraulic drive device including means for changing the initial setting load of the biasing means. Characteristic hydraulic drive.

In a second aspect based on the first aspect, the initial load changing means is composed of a second pressure responsive member driven in response to a pressure from an external hydraulic source.

In a third aspect based on the first aspect, the initial load changing means is a solenoid.

A fourth aspect of the invention is directed to a first drive shaft driven by a prime mover, a pump which is driven in synchronization with the first drive shaft to supply pressure oil in a predetermined direction, and a second drive shaft. A variable displacement motor, which is connected to the drive shaft of, and is driven in accordance with the pressure oil from the pump, including a capacity changing means,
Direction switching means for switching the rotation direction of the motor according to the rotation direction of the first drive shaft, a relief valve for returning pressure oil to the tank when the supply pressure from the pump exceeds a predetermined value, and a predetermined A pressure responsive member that drives the capacity changing means according to the hydraulic pressure from a hydraulic pressure source, a restricting means that restricts the capacity changing means driven by the pressure responsive member at a predetermined maximum capacity position of the motor, and a capacity of the motor. In a hydraulic drive device including an urging unit that drives the capacity changing unit in a direction in which the pressure decreases, the throttle unit is provided between the pressure responsive member and the pump and communicates with the tank.

A fifth aspect of the present invention is the first to fourth aspects of the invention.
In any one of the inventions, the motor is composed of a swash plate type piston motor having a swash plate as a capacity changing means, and the pressure responsive member increases an inclination angle of the swash plate according to a supply pressure. While driving in the direction
The biasing means biases the swash plate in a direction in which the tilt angle is reduced.

In a sixth aspect based on the fifth aspect, the center of rotation of the swash plate is disposed on an axis substantially orthogonal to the axis of the motor, and the pressure responsive member and the urging force are applied. Means are arranged at predetermined positions from the center of rotation.

[0012]

Therefore, according to the first aspect of the present invention, the hydraulic oil from the pump is pumped to the variable displacement motor in response to the rotation of the first drive shaft driven by the prime mover, and the hydraulic oil from the predetermined hydraulic source is supplied. The pressure responsive member drives the capacity changing means against the urging means for which the urging force is set by the initial setting load changing means, and the thrust of the pressure responsive member and the thrust of the urging means generated in response to this hydraulic pressure are balanced. The displacement of the variable displacement pump is set at the position where the pressure is set, and the driving force corresponding to this displacement and the discharge pressure of the pump is transmitted to the second drive shaft. When the rotation speeds of the first drive shaft and the second drive shaft are substantially equal, the power from the prime mover is distributed to the first and second drive shafts according to the capacity of the motor in which the pressure responsive member and the biasing means are balanced. The ratio can be set arbitrarily, and the distribution ratio of the driving force can be changed by changing the initial setting load of the biasing means. On the other hand, when the first drive shaft idles, the discharge pressure of the pump increases and the pressure response member is driven by the capacity changing means until the capacity reaches a predetermined maximum value by the regulating means, while the discharge pressure of the pump is increased. When the pressure exceeds a predetermined value, the relief valve opens and the pressure oil from the pump flows back to the tank, and the second drive shaft is driven with the maximum driving force according to the set pressure of the regulating means and the relief valve. The distribution ratio can be changed with high responsiveness from the stopped state of the first drive shaft.

According to the second aspect of the invention, the initial set load of the biasing means can be changed according to the hydraulic pressure from the outside which drives the second pressure responsive member, and the hydraulic pressure of the external hydraulic source is adjusted. The driving force distributed to the second driving shaft can be arbitrarily changed regardless of the discharge pressure of the pump.

According to the third aspect of the invention, the initial setting load of the biasing means can be changed according to the driving of the solenoid,
The driving force distributed to the second driving shaft can be arbitrarily changed regardless of the discharge pressure of the pump.

According to a fourth aspect of the present invention, the pressure responsive member constitutes a bleed-off circuit by a throttle, and the first drive shaft and the second drive shaft are provided.
The distribution of the driving force to the drive shaft is set according to the discharge pressure of the pump supplied through the throttle, and the driving force can be distributed to the second drive shaft at an arbitrary ratio by adjusting the throttle. it can.

Further, a fifth aspect of the present invention changes the inclination angle of the swash plate according to the hydraulic pressure supplied to the pressure responsive member, and the second aspect of the present invention depends on the displacement according to the inclination angle of the swash plate and the discharge pressure of the pump. The drive force can be distributed to the drive shaft, and the drive force distributed to the second drive shaft can be changed according to the change of the inclination angle of the swash plate.

According to a sixth aspect of the present invention, the driving force generated by the motor is set by an inclination angle according to the moment around the swash plate, and the arrangement position of the pressure responsive member or the urging means is changed to change the first position. Also, the distribution ratio of the driving force to the second drive shaft can be changed.

[0018]

1 and 2 show an embodiment in which the present invention is applied to a four-wheel drive vehicle.

In FIGS. 1 and 2, a front wheel 3 as a first drive shaft connected to a prime mover 1 via a transmission 2 is provided with a front wheel 4 of a vehicle, while a front drive wheel 4 serves as a second drive shaft. A rear wheel 6 is provided on the rear shaft 5.

The front shaft 3 is connected to a hydraulic pump 7 that constantly supplies pressure oil in a predetermined direction, while the rear shaft 5 is a variable displacement motor that is driven according to the pressure oil from the hydraulic pump 7. Hydraulic motor 8 composed of a swash plate type piston motor
Are linked. The hydraulic pump 7 may be a rotary swash plate type axial piston pump or a radial piston pump having a check valve or the like and a constant discharge direction regardless of the rotation direction of the front shaft 3.

The hydraulic fluid pressure-fed from the hydraulic pump 7 is supplied from the supply passage 40 to the hydraulic motor 8 via the direction switching valve 10 which controls the forward and backward movements in conjunction with the transmission 2. The discharge direction of the hydraulic pump 7 is always directed toward the supply passage 40 regardless of the rotation direction of the front shaft 3.

The hydraulic oil discharged from the hydraulic motor 8 also flows back from the return passage 50 to the tank 11 via the direction switching valve 10.

A relief valve 9 is provided between the hydraulic pump 7 and the direction switching valve 10 to release the oil to the return passage 50 when the oil pressure in the supply passage 40 exceeds a predetermined value. Control the set pressure.

Further, the hydraulic pressure from the hydraulic pump 7 applied to the supply passage 40 is used as a pilot pressure for controlling the inclination angle of the swash plate, which will be described later.

As shown in FIG. 2, the hydraulic motor 8 composed of a swash plate type piston motor has a large number of pistons 2 in a cylinder block 20 arranged coaxially with a shaft 23.
1, the pistons 21 are slidably contacted with a swash plate 22 as a capacity changing means, and the inclination angle α of the swash plate 22 is increased.
The displacement of the piston 21 is changed according to
Drives the shaft 23 in accordance with the inclination angle α of the swash plate 22 and the hydraulic oil supplied from the hydraulic pump 7. The hydraulic motor 8
The shaft 23 of is connected to the rear shaft 5.

The swash plate 22 is provided with a trunnion shaft 22A which is a center of rotation on the shaft 23 in a direction orthogonal to the shaft 23, and is inclined at a predetermined position of a casing (not shown) facing the upper end of the swash plate 22 in the figure. A minimum inclination angle stopper 33 for restricting the minimum inclination angle α ₀ of the plate 22 is provided, while a maximum inclination angle of the swash plate 22 is provided at a predetermined position of a casing (not shown) that also faces the lower end of the swash plate 22 in the figure. A maximum inclination angle stopper 34 is provided as a means for regulating α _max, and the displacement of the hydraulic motor 8 reaches a predetermined maximum displacement at the position of the maximum inclination angle stopper 34.

The swash plate 2 is provided on the upper end side of the swash plate 22 in the figure.
The spring 30 as a biasing means for biasing 2 toward the minimum inclination angle stopper 33 has an initial set load (set load).
It is provided on the casing side (not shown) via a solenoid 36 as a means for changing the. By exciting the solenoid 36 by a driving means (not shown), the initial set load of the spring 30 can be changed.

On the other hand, an oil chamber 35 is formed at a predetermined position of the casing facing the lower end side of the swash plate 22 in the figure, and the swash plate 2 is formed.
A piston 31 is accommodated as a pressure responsive member for urging 2 toward the maximum inclination angle stopper 34 to control the inclination angle α.

Here, the spring 30 and the piston 31
Are arranged substantially parallel to the shaft 23, the spring 30 and the solenoid 36 are arranged at a position having a radius Rs from the trunnion shaft 22A, and the piston 31 is also arranged at a position having a radius Rp from the trunnion shaft 22A.

The piston 31 extends from the supply passage 40 to the throttle 32.
It expands and contracts in response to the pilot pressure supplied to the oil chamber 35 via, and rotates the swash plate 22 toward the maximum inclination angle stopper 34 against the biasing force of the spring 30. The throttle 32 buffers an excessive fluctuation of the pilot pressure applied to the oil chamber 35 and suppresses an excessive torque fluctuation of the hydraulic motor 8.

With the above construction, the operation will be described below.

The driving force of the prime mover 1 is transmitted to the front shaft 3 via the transmission 2 to drive the front wheels 4, and the hydraulic pump 7 connected to the front shaft 3 is driven.

The hydraulic oil pumped from the hydraulic pump 7 is supplied from the supply passage 40 to the hydraulic motor 8 via the directional control valve 10, and the hydraulic motor 8 drives the rear shaft 5 in response to the hydraulic oil, so that the vehicle is It is propelled by the front wheels 4 and the rear wheels 6.

Now, when the front shaft 3 and the rear shaft 5 are traveling at substantially the same rotation speed, the discharge amount Qp of the hydraulic pump 7 and the suction amount Qm of the hydraulic motor 8 become substantially the same, and the hydraulic motor 8
The inclination angle α of the swash plate 22 equilibrates at the position of the piston 31 which extends against the spring 30 according to the discharge pressure Pd of the hydraulic pump 7.

On the other hand, when the suction amount Qm of the hydraulic motor 8 is smaller than the discharge amount Qp of the hydraulic pump 7, for example, the front wheels 4
When the wheel slips and the rear wheels 6 come into contact with the ground, the supply passage 40
Since the internal hydraulic pressure, that is, the discharge pressure Pd rises, the pilot pressure Pd applied to the piston 31 that controls the swash plate 22 of the hydraulic motor 8 also increases, and the piston 31 causes the spring 3 to move.
The displacement volume Dm of the hydraulic motor 8 is increased while increasing the inclination angle α of the swash plate 22 against 0.

Here, the suction amount Qm of the hydraulic motor 8 is the product of the rotational speed Nm of the hydraulic motor 8 and the displacement Dm per one rotation of the motor, as shown in the following equation. It is proportional to the inclination angle α of 22.

[0037]

[Equation 1]

From the equation (1), the swash plate 22 rotates to the inclination angle α where Qm = Qp, while the discharge pressure Pd of the hydraulic pump 7 is increased.
Is expressed as follows from the balance of the moment of the swash plate 22.

[0039]

[Equation 2]

Here, Me is the piston 2 of the hydraulic motor 8.
Although it is a moment of the swash plate 22 generated based on the thrust of 1, it becomes a small value and can be ignored when the discharge pressure Pd of the hydraulic pump 7 is low. Is represented as

[0041]

(Equation 3)

In the above equation (3), each coefficient is as follows: Apc: Effective area of piston 31 k: Spring constant of spring 30 X ₀ : Initial compression length of spring 30 (initial setting load)

Therefore, according to the equation (3), the pressure Pd of the hydraulic pump 7 applied to the hydraulic motor 8 is the distance Rp, R of the piston 31 and the spring 30 from the trunnion shaft 22A.
s, effective area Apc of piston 31, spring 30
The discharge pressure Pd can be set to any value by changing these values based on the initial compression length X ₀ and the spring constant k of the front shaft 3 and the rear shaft 5. In the steady running state where the rotation speed is almost the same,
Drive force, that is, the torque of the hydraulic motor 8 is set by the discharge pressure Pd and the inclination angle α at which the moment about the swash plate 22 by the spring 30 and the moment by the thrust of the piston 31 are also balanced.

Here, if the initial set load of the spring 30 is changed by driving the solenoid 36, that is, the initial compression amount X ₀ in the above equation (3) is made variable, it is added to the supply passage 40. The discharge pressure Pd can be set to an arbitrary value, so that the driving force of the prime mover 1 can be distributed to the front shaft 3 and the rear shaft 5 at an arbitrary ratio during the steady running of the vehicle. The ratio of the driving force set in advance based on the moment around the plate 22 can be changed by driving the solenoid 36 even while the vehicle is traveling. If the solenoid 36 is constituted by a linear solenoid or the like, the distribution ratio of the driving force can be continuously changed. It can be changed smoothly, and it becomes possible to further improve the running performance of the vehicle by changing the driving force applied to the front shaft 3 and the rear shaft 5 according to the road surface condition.

In this steady running state or the front shaft 3 and the rear shaft 5
The change of the distribution of the driving force during the acceleration so that the rotation speeds of the rear shaft 5 become substantially the same, for example, while the straight shaft is mainly driven by the front shaft 3 to secure the straight traveling stability, while the rear shaft 5 is rotated during the turning. By increasing the distribution ratio of the driving force to the understeer, it is possible to suppress the understeer and secure the turning performance.

When the discharge pressure Pd is set low,
When the rotation speeds of the front shaft 3 and the rear shaft 5 are substantially the same, the theoretical value of the torque Tm generated by the hydraulic motor 8 is given by the following equation.

[0047]

[Equation 4]

Note that Ps represents the suction pressure of the hydraulic pump 7.

The torque Tm of the hydraulic motor 8 has a small value because it is proportional to the discharge pressure Pd.
Drives mainly with the driving force of.

On the other hand, if the discharge amount Qp of the hydraulic pump 7 <the suction amount Qm due to an increase in the rotation speed of the rear shaft 5 or a decrease in the rotation speed of the front shaft 3, the discharge pressure Pd decreases according to the above equation. Therefore, while the piston 31 contracts, the spring 30 expands, the inclination angle α of the swash plate 22 decreases, and the displacement of the hydraulic motor 8 decreases, so the driving force to the rear shaft 5 decreases and the discharge amount Q
p and the inhaled amount Qm are in equilibrium. However, the decrease of the inclination angle α is restricted at the position where the swash plate 22 contacts the minimum inclination angle stopper 33, and the rear shaft 5 and the rear wheel 6 are driven by the driving force corresponding to the minimum inclination angle α ₀ at this time. .

Here, when the front wheels 4 spin from the stopped state while the rear wheels 6 start to drive when the vehicle starts or suddenly accelerates, the rotational speed of the front shaft 3 becomes equal to that of the rear shaft 5. And the discharge amount Qp of the hydraulic pump 7 exceeds the suction amount Qm of the hydraulic motor 8 and becomes Qp> Qm.

In such a case, as described above, the discharge pressure Pd increases and the piston 31 expands against the spring 30, so that the inclination angle α of the swash plate 22 increases and the suction amount of the hydraulic motor 8 increases. Qm tries to approach the discharge amount Qp, but if the discharge pressure Pd continues to increase, the swash plate 22 uses the maximum tilt angle stopper 34 to increase the tilt angle α to the maximum value α.
_{In addition to} being regulated to _max , the relief valve 9 is opened and the rear shaft 5 is driven with the maximum set angle according to the maximum inclination angle α _max and the set pressure of the relief valve 9, and the rear wheel is replaced by the rear wheel instead of the idle front wheel 4. The driving force of No. 6 can be rapidly increased to accelerate the vehicle smoothly. At this time, the driving force distribution ratio to the rear shaft 5 is increased substantially in proportion to the increase in the rotational speed of the front shaft 3, and the driving force to the rear shaft 5 can be increased with high responsiveness. It is possible to easily start the vehicle in a situation where the road surface has a low friction coefficient such as an icy road or a bad road, and the change of the driving force distribution ratio at this time responds as the rotation speed of the front shaft 3 increases. Therefore, the stability of the vehicle can be secured.

Similarly, the driving force to the rear shaft 5 is increased and the driving force to the front shaft 3 is reduced during turning acceleration of the vehicle in which Qp> Qm. It is possible to secure the sex.

Thus, during steady running, the driving force to the front shaft 3 and the rear shaft 5 is distributed in accordance with the above-mentioned set values of the piston 31 and the spring 30, and one of the front shaft 3 and the rear shaft 5 is distributed. When idling, the driving force to the other can be increased with high responsiveness, and the change of the distribution of the driving force at this time is determined according to the discharge pressure Pd of the hydraulic pump 7, and according to this change of the discharge pressure Pd. The piston 31 can respond quickly, and the distribution ratio of the driving force can be easily changed arbitrarily even during steady running by driving the solenoid 36, and the straight running stability, turning performance, etc. according to the running state of the vehicle can be achieved. It is possible to obtain the driving performance of, and it is possible to distribute the driving force at an arbitrary ratio and with high responsiveness while having a simple structure without requiring a special control device such as a servo mechanism, further, Since only the pressure motor 8 needs to be a variable displacement type, an increase in manufacturing cost can be suppressed, and no mechanical power transmission means such as a propeller shaft or a differential limiting device is required unlike the conventional example. When applied to vehicles such as passenger cars, it is possible to improve the running performance of the vehicle while increasing the effective space of the vehicle body, and by forming the floor surface flat, it is possible to easily secure the interior space of the vehicle compared to the conventional example. It is possible to promote weight reduction.

Further, since the propeller shaft or the like is not required as described above, the FF vehicle or the FR vehicle can be easily four-wheel drive without making a great change in the vehicle body, and the existing vehicle body is diverted. This makes it possible to easily implement four-wheel drive while suppressing an increase in manufacturing cost.

In the above embodiment, the solenoid 3
6 indirectly biases the swash plate 22 via the spring 30, but as shown in FIG. 3, the solenoid 36 and the spring 30 are arranged in parallel in the radial direction of the swash plate 22, and the solenoid 36 Alternatively, the spring 30 and the spring 30 may directly bias the swash plate 22.

Further, the hydraulic pump 7 is used such that the discharge direction is always constant regardless of the rotation direction of the front shaft 3. However, as shown in FIG. 4, the constant supply passage 40 is provided via the check valves 70a to 70d. The hydraulic oil may be pumped to the tank 11 while being sucked from the tank 11. In this case, as the hydraulic pump 7 ', one whose discharge direction is switched according to the rotation direction of the front shaft 3 can be used.

FIG. 5 shows the second embodiment, in which the second pressure for urging the swash plate 22 in the mounting position Rs of the spring 30 in place of the solenoid 36 in the direction in which the inclination angle α decreases in the first embodiment. A pilot piston 37 as a responding member is provided, and a spring 30 is housed inside the pilot piston 37. Other configurations are similar to those of the first embodiment.

The pilot piston 37 is housed in an oil chamber 38 formed on the casing side (not shown), and the spring 3
0 is the oil chamber 38 at the base end and the pilot piston 37 at the other end.
Abutting the inner circumference of the end of the
The swash plate 22 is biased according to the pilot pressure Pp applied to the valve 8 and the biasing force of the spring 30, that is, the spring constant k.

Here, the pilot pressure P applied to the oil chamber 38
p is a hydraulic pressure from an external hydraulic source (not shown), and in this case as well, the drive of the prime mover 1 is performed during steady running of the vehicle in which the rotation speeds of the front shaft 3 and the rear shaft 5 are substantially the same as in the first embodiment. The force can be distributed to the front shaft 3 and the rear shaft 5 at an arbitrary ratio, and variable control can be performed by changing the pilot pressure Pp to the set ratio of the driving force.

Although the pilot piston 37 and the spring 30 are integrally provided, the spring 30 and the pilot piston 37 can be separately provided.

FIG. 6 shows a third embodiment, in which a variable throttle 39 communicating with the tank 11 is provided from the middle of the throttle 32 and the oil chamber 35 in the first embodiment, and the piston 31 is driven by a bleed-off circuit. The solenoid 36 is eliminated and the base end of the spring 30 is provided on the casing side, and the other configurations are the same as those in the first embodiment.

By adjusting the variable throttle 39, it is possible to reduce the pilot pressure Pd from the supply passage 40 to an arbitrary pressure, and the piston 31 tilts the inclination angle α of the swash plate 22 according to the hydraulic pressure from the variable throttle 39. Can be set arbitrarily, and the driving force of the hydraulic motor 8 can be variably controlled. In this case, as in the first or second embodiment, the front shaft 3 and It becomes possible to arbitrarily change the distribution ratio of the driving force to the rear shaft 5,
The running performance of the vehicle can be improved.

It is possible to perform arbitrary control by configuring the variable diaphragm 39 with an electromagnetic type or the like.

7 and 8 show a fourth embodiment, in which the hydraulic motor 8 in the first embodiment is replaced with a hydraulic motor 8A composed of a swash plate type variable displacement piston motor having both tilt angles. Then, the pressure oil from the hydraulic pump 7 is directly supplied to the hydraulic motor 8A, and the pilot pressure for controlling the inclination angle α of the swash plate 22 is synchronized with the traveling direction of the forward or reverse vehicle selected by the transmission 2. It is supplied to the hydraulic motor 8A via the directional switching valve 10A which is switched by.

The inclination angle α of the swash plate 22 is switched between positive and negative depending on the traveling direction of the vehicle. For example, the inclination angle α> 0 for forward movement, and the inclination angle α <0 for backward movement. The pistons 31A and 31B that drive the swash plate 22 by receiving the pilot pressure Pd from the direction switching valve 10A are shown in FIG.
As shown in FIG. 5, the hydraulic motor 8A is provided at a position where it can come into contact with each end of the swash plate 22 in the drawing corresponding to normal rotation and reverse rotation.

The pistons 31A and 31B are the trunnion shaft 2
Oil chambers 35A and 35B arranged at the center of 2A, that is, at a distance Rp from the shaft 23 of the hydraulic motor 8A, respectively.
The oil chambers 35A and 35B are housed in the directional control valve 10A via throttles 32A and 32B that suppress excessive fluctuations in hydraulic pressure.
Communicate with

Inside the pistons 31A and 31B, springs 30A and 30B for biasing the pistons 31A and 31B toward the swash plate 22 are provided in the solenoid 36A,
36B, respectively, and these springs 3
The spring constants of 0A and 30B are k ′, and the initial set load of the initial compression amount X ₀ is set. The piston 3
The effective sectional areas of 1A and 31B are the same as those of the first embodiment.
It is represented by pc.

The maximum inclination angle α _max of the swash plate 22 is restricted in each direction by the maximum inclination angle stoppers 34A and 34B.

Here, the swash plate 22 is controlled around the inclination angle α = 0 in order to control forward and backward movement of the vehicle equally.

During steady running in which the rotation speeds of the front shaft 3 and the rear shaft 5 are substantially the same, the hydraulic pump 7 is the same as in the first embodiment.
And the suction amount Qm of the hydraulic motor 8A become substantially equal to each other.

(Equation 5) In addition, the discharge pressure Pd of the hydraulic pump 7 is

(Equation 6) Therefore, the torque of the hydraulic motor 8, that is, the distribution ratio of the driving force between the front wheels 4 and the rear wheels 6 can be arbitrarily set by the moment around the swash plate 22 as in the first embodiment. , 31B, position Rp, effective area Apc, spring constant k ′ of springs 30A and 30B, and initial load set by solenoids 36A and 36B.

During this steady running, when the vehicle is moving forward, the solenoid 36B is excited by a driving means (not shown) to change the initial load of the spring 30B, thereby changing the hydraulic motor 8A in the same manner as in the first embodiment. It becomes possible to variably control the driving force of the front shaft 3 and the rear shaft 5, and it is possible to arbitrarily change the distribution ratio of the driving force of the front shaft 3 and the rear shaft 5. When the vehicle is in reverse, the solenoid 36A excites the front shaft 3 and the rear shaft. The driving force to the shaft 5 can be changed arbitrarily.

On the other hand, when the front wheel 4 is idling when the discharge amount Qp of the hydraulic pump 7> the intake amount Qm, the swash plate 22 contacts the maximum tilt angle stopper 34A or 34B in the same manner as described above, and the maximum tilt angle α _max. When the discharge pressure Pd further increases, the relief valve 9 opens, the hydraulic motor 8 is driven with a predetermined maximum torque, and the driving force of the rear wheel 6 instead of the idle front wheel 4 is increased to smooth the vehicle. Can be accelerated to.

When the vehicle moves forward, the piston 31A pushes the swash plate 22 against the piston 31B and the spring 30B, while when the vehicle moves backward, the piston 31B moves the piston 3 to the piston 3.
1A, the swash plate 22 is pressed against the spring 31A, and the inclination angle α of the swash plate 22 is increased.

In the first embodiment, the directional control valve 10 switches the main circuit, whereas the directional control valve 10A switches only the pilot pressure Pd, so that it is smaller and lighter than the first embodiment. It is possible to configure, it is possible to promote the manufacturing cost and downsizing of the device, and other functions and effects are the same as those in the first embodiment.

FIG. 9 shows the fifth embodiment, in which the pistons are provided with the variable throttles 39A and 39B communicating with the tank 11 from the middle of the oil chambers 35A and 35B and the throttles 32A and 32B of the fourth embodiment. 31A and 31 are driven by a bleed-off circuit, while solenoids 36A and 36B are abolished. Other configurations are the same as in the fourth embodiment.

During steady running in which the rotational speeds of the front shaft 3 and the rear shaft 5 are substantially equal to each other, the pilot pressure applied to the piston 31A is changed by adjusting the variable throttle 39A constituting the bleed-off circuit when the vehicle is moving forward. As a result, the driving force of the hydraulic motor 8A can be variably controlled in the same manner as in the fourth embodiment, and the distribution ratio of the driving forces of the front shaft 3 and the rear shaft 5 can be arbitrarily changed. Similarly, when the vehicle is moving backward, the driving force to the front shaft 3 and the rear shaft 5 can be arbitrarily distributed by adjusting the variable diaphragm 39B.

FIG. 10 shows a sixth embodiment, in which the directional control valve 10A and the variable throttle 39 which communicates with the tank 11 from the middle of the supply passage 40 in the fifth embodiment are provided, and the motor 8 is excessively changed. The diaphragm 32 for suppressing the
The upstream side of 9, that is, on the side of the supply passage 40, the other configurations are the same as those of the fifth embodiment.

During steady running when the rotation speeds of the front shaft 3 and the rear shaft 5 are substantially equal to each other, the pistons 31A, 31 are adjusted by adjusting the variable throttle 39 regardless of whether the vehicle is moving forward or backward.
By changing the pilot pressure Pd applied to B, the driving force of the hydraulic motor 8A can be variably controlled, and the distribution ratio of the driving forces of the front shaft 3 and the rear shaft 5 can be arbitrarily changed. Become. In this case, the variable aperture 39A when moving forward
By adjusting the variable diaphragm 39B during reverse,
The driving force of the hydraulic motor 8A can be finely adjusted, and the distribution ratio of the driving force can be set according to the traveling direction.

The variable diaphragm 39 communicating with the tank 11
A and 39B may be eliminated and the driving force may be changed only by the variable aperture 39. In this case, the number of parts can be reduced as compared with the above embodiment.

FIG. 11 shows the seventh embodiment, and the pilot pressure P from an external hydraulic pressure source (not shown) is provided on the outer periphery of the oil chambers 35A and 35B shown in the fourth embodiment as in the second embodiment.
_PA, provided an oil chamber 38A for guiding the P _PB, 38B, respectively, these oil chambers 38A, the pilot piston 37A that urges the swash plate 22 to 38B, while accommodated the 37B, which was abolished solenoid 36A, the 36B, The other structure is the same as that of the fourth embodiment.

During steady running in which the rotation speeds of the front shaft 3 and the rear shaft 5 are substantially equal to each other, the pilot pressure P _PB applied to the oil chamber 38B is changed when the vehicle is moving forward to change the second speed.
It becomes possible to variably control the driving force of the hydraulic motor 8A by changing the inclination angle α of the swash plate 22 as in the embodiment.
It becomes possible to arbitrarily change the distribution ratio of the driving forces of the front shaft 3 and the rear shaft 5, and when the vehicle is in reverse, the pilot pressure P _PA applied to the oil chamber 38A is changed to drive the front shaft 3 and the rear shaft 5. Power can be distributed arbitrarily. Of course,
The swash plate 2 is responsive to the pressure difference between the oil pressures applied to the oil chambers 38A and 38B.
A tilt angle of 2 may be controlled.

In the above embodiment, the front shaft 3 driven by the prime mover 1 via the transmission 2 is provided with the hydraulic pump 7 and the rear shaft 5 is provided with the hydraulic motor 8, respectively. The rear shaft 5 may be driven by the prime mover 1 via the machine 2, and the hydraulic pump 7 may be arranged on the rear shaft 5 while the hydraulic motor 8 may be arranged on the front shaft 3. Further, the hydraulic motor 8 may drive a plurality of axles.

In the above embodiment, the hydraulic pump 7
Is connected to the front shaft 3, the hydraulic pump 7 may be rotated synchronously with the front shaft 3. For example, the hydraulic pump 7 is connected to the output shaft of the transmission 2 to synchronize with the front shaft 3. May be

Further, in the above embodiment, the spring 3
0, 30A, 30B, pistons 31, 31A, 31B,
The pilot pistons 37, 37A, 37B are members that control the moment acting on the swash plate 22 around the trunnion shaft 22A, and the arrangement position thereof is not limited to a position substantially parallel to the shaft 23. It can be inclined and arranged.

In the above embodiment, the hydraulic motor 8
Alternatively, although 8A is composed of a swash plate type variable displacement axial piston motor, it may be composed of a swash shaft type variable displacement motor or a variable displacement radial piston motor, etc., although not shown.

In the above embodiment, the hydraulic pump 7
Alternatively, if the suction pressure limiting type pump 7'is used and the discharge flow rate is substantially constant at a predetermined rotation speed or more, unnecessary power transmission can be suppressed and mechanical loss can be reduced.

[0088]

As described above, according to the first invention, the first
Of the present invention, a first drive shaft driven by a prime mover, a pump that is driven in synchronization with the first drive shaft to supply pressure oil, and a second drive shaft are connected, and the capacity is changed. A variable displacement motor that is equipped with a means and is driven according to the pressure oil from the pump; a relief valve that returns the pressure oil to the tank when the supply pressure from the pump exceeds a predetermined value; and a relief valve from the pump. A pressure responsive member that drives the capacity changing means according to the oil pressure, a restricting means that restricts the capacity changing means driven by the pressure responsive member at a predetermined maximum capacity position of the motor, and a direction in which the capacity of the motor decreases. A biasing means for driving the capacity changing means and a means for changing an initial setting load of the biasing means, and a capacity and a pump in which the pressure responsive member and the biasing means driven by the initial setting load are balanced. Second drive according to discharge pressure To the power it is possible to allocate, it is possible to arbitrarily set by the distribution ratio of the driving force pressure responding member and a biasing means and the initial set load changing means,
Since the distribution ratio can be changed with high responsiveness to changes in driving force, it is possible to easily start on icy roads, etc.In addition, during steady running, the initial setting load of the biasing means It is possible to obtain any driving force distribution ratio by changing the driving force distribution ratio, and it is possible to improve running performance such as straight running stability and turning performance by the driving force distribution ratio according to the running state of the vehicle. Since no control means is required, the number of parts can be reduced as compared with the conventional example, and reduction in manufacturing cost can be promoted while promoting miniaturization and weight reduction of the vehicle.

The second aspect of the present invention changes the initial set load of the urging means in accordance with the hydraulic pressure from the external hydraulic pressure source, so that the driving force distributed to the second drive shaft can be arbitrarily set regardless of the discharge pressure of the pump. It is possible to change the distribution ratio of the driving force according to the running state, and it is possible to improve the running performance of the vehicle.

In the third invention, the initial set load of the biasing means is changed by driving the solenoid, and the driving force distributed to the second drive shaft can be arbitrarily changed regardless of the discharge pressure of the pump. Therefore, it is possible to electrically change the distribution ratio of the driving force according to the traveling state, and it is possible to expand the degree of freedom of control and improve the traveling performance of the vehicle.

A fourth aspect of the present invention includes a first drive shaft driven by a prime mover, a pump driven synchronously with the first drive shaft to supply pressure oil, and a second drive shaft. A variable displacement motor that is connected and that is equipped with a capacity changing means and is driven according to the pressure oil from the pump, and a relief that returns the pressure oil to the tank when the supply pressure from the pump exceeds a predetermined value. A valve, a pressure responsive member that drives the capacity changing means according to the hydraulic pressure from the pump, and a restricting means that restricts the capacity changing means driven by the pressure responsive member at a predetermined maximum capacity position of the motor, An urging means for driving the capacity changing means in a direction in which the capacity of the motor is reduced, and a throttle connected between the pressure responsive member and the pump to communicate with the tank are provided. Hydraulic pressure of pressure responsive member It can be driven, and the distribution ratio of the driving force to the second drive shaft can be easily changed with a simple structure, and the traveling performance of the vehicle is improved by changing the distribution ratio of the driving force according to the traveling state. It is possible to
Since no special control means is required, it is possible to reduce the number of parts as compared with the conventional example, and it is possible to promote the reduction of manufacturing cost.

According to a fifth aspect of the present invention, the motor is a swash plate type piston motor having a swash plate as a capacity changing means, and the pressure response member has an inclination angle of the swash plate according to a supply pressure. While driving in the direction of increasing
The biasing means biases the tilt angle of the swash plate in a direction to decrease the tilt angle of the swash plate is changed according to the hydraulic pressure supplied to the pressure responsive member. Therefore, the second structure has a simple structure. It is possible to arbitrarily change the distribution ratio of the driving force to the drive shaft, and it is possible to reduce the manufacturing cost while improving the running performance of the vehicle.

According to a sixth aspect of the present invention, the center of rotation of the swash plate is disposed on an axis that is substantially orthogonal to the axis of the motor, and the pressure responsive member and the biasing means are disposed from the center of rotation. The distribution ratios of the driving forces to the second driving shafts, which are respectively arranged at predetermined positions, can be arbitrarily set according to the moment around the swash plate where the pressure responsive member and the biasing means are balanced and the supply pressure to the motor. Therefore, it becomes possible to simplify the structure of the apparatus and reduce the manufacturing cost without requiring any special control means.

[Brief description of drawings]

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

FIG. 2 is a schematic explanatory diagram of a swash plate type variable displacement motor.

FIG. 3 is an explanatory view of a main part of a swash plate type variable displacement motor in which a solenoid and a spring are arranged in parallel.

FIG. 4 is a hydraulic circuit diagram of a pump.

FIG. 5 is a schematic explanatory view of a swash plate type variable displacement hydraulic motor showing a second embodiment.

FIG. 6 is a schematic explanatory view of a swash plate type variable displacement hydraulic motor showing a third embodiment.

FIG. 7 is a block diagram showing a fourth embodiment.

FIG. 8 is a schematic explanatory view of a swash plate type variable displacement hydraulic motor.

FIG. 9 is a schematic explanatory view of a swash plate type variable displacement hydraulic motor showing a fifth embodiment.

FIG. 10 is a schematic explanatory view of a swash plate type variable displacement hydraulic motor showing a sixth embodiment.

FIG. 11 is a schematic explanatory view of a swash plate type variable displacement hydraulic motor showing a seventh embodiment.

[Explanation of symbols]

 1 prime mover 3 front shaft 5 rear shaft 7 hydraulic pump 8 hydraulic motor 9 relief valve 10 directional switching valve 11 tank 22 swash plate 23 shaft 30 spring 31 piston 34 maximum inclination angle stopper 36 solenoid 37 pilot piston 39 variable throttle 40 supply passage

Claims (6)

[Claims] 1. A first drive shaft driven by a prime mover, a pump driven synchronously with the first drive shaft to supply pressure oil, a second drive shaft, and a capacity. A variable displacement motor provided with a changing means and driven according to pressure oil from the pump, a relief valve for returning the pressure oil to the tank when the supply pressure from the pump exceeds a predetermined value, and the pump The pressure responsive member that drives the capacity changing means in accordance with the hydraulic pressure, the restricting means that restricts the capacity changing means driven by the pressure responsive member at a predetermined maximum capacity position of the motor, and the capacity of the motor decreases. A hydraulic drive system including a biasing means for driving the capacity changing means in a direction, and a means for changing an initial set load of the biasing means. 2. The hydraulic drive system according to claim 1, wherein the initial load changing means is composed of a second pressure responsive member that is driven according to a pressure from an external hydraulic source. 3. The hydraulic drive system according to claim 1, wherein the initial setting load changing means comprises a solenoid. 4. A first drive shaft driven by a prime mover, a pump driven synchronously with the first drive shaft to supply pressure oil, a second drive shaft, and a capacity. A variable displacement motor provided with a changing means and driven according to pressure oil from the pump, a relief valve for returning the pressure oil to the tank when the supply pressure from the pump exceeds a predetermined value, and the pump The pressure responsive member that drives the capacity changing means in accordance with the hydraulic pressure, the restricting means that restricts the capacity changing means driven by the pressure responsive member at a predetermined maximum capacity position of the motor, and the capacity of the motor decreases. A hydraulic drive device including an urging means for driving the capacity changing means in a direction, characterized by comprising a throttle interposed between the pressure responsive member and the pump and communicating with a tank. Hydraulic drive. 5. The motor comprises a swash plate type piston motor having a swash plate as a capacity changing means, and the pressure responsive member drives in a direction to increase an inclination angle of the swash plate according to a supply pressure. The hydraulic drive device according to any one of claims 1 to 4, wherein the urging means urges the swash plate in a direction in which an inclination angle of the swash plate is reduced. 6. The center of rotation of the swash plate is disposed on an axis substantially orthogonal to the axis of the motor, and the pressure responsive member and the urging means are arranged at predetermined positions from the center of rotation. The hydraulic drive device according to claim 5, wherein the hydraulic drive device is provided.