JPS63255128A - Four-wheel drive device - Google Patents

Abstract

PURPOSE:To improve the flexibility of a design in a four-wheel drive system by driving either side of both front and rear wheels mechanically by power out of an engine, while driving either other side of these front and rear wheels by a hydraulic system via a main transmission. CONSTITUTION:An engine 1 is interlocked with each of symmetrical rear wheels 1e and 1d via a main transmission 1a, a drive shaft 1b and a differential 1c. And a hydraulic pump 2 is interlocked with this drive shaft 1b, and the hydraulic pump 2 is interlocked with plural hydraulic motors 2f and 2g via two hydraulic oil pipes 2b and 2c, while these hydraulic motors 2f and 2g are interlocked with symmetrical front wheels 2p and 2q. Likewise, a pressure detector 2k is installed in a hydraulic oil pipe 2n, and a detection signal out of this pressure detector 2k is inputted into a computer 4. And, each of actuators 2a, 2i and 2j is controlled by a control signal out of this computer 4, thereby operating the hydraulic pump 2 and respective hydraulic motors 2f and 2g.

Description

[Detailed description of the invention] [Industrial application field] TECHNICAL FIELD The present invention relates to a four-wheel drive device in an automobile.

[Prior Art] Conventionally, a four-wheel drive system in an automobile is capable of driving all four wheels, and therefore not only effectively exerts its driving or braking force when driving on a slippery road surface, but also effectively exerts its driving force or braking force when driving on a slippery road surface. It has been attracting particular attention in recent years due to its excellent steering stability.

The configuration of these four-wheel drive devices is such that output power from the engine mechanically drives the front wheels or rear wheels on the one hand via a transmission, and mechanically drives the rear wheels or front wheels on the other hand. It is structured as follows.

[Problems to be Solved by the Invention] However, in these four-wheel drive devices, both the front wheels and the rear wheels are mechanically driven via a drive shaft, as shown in L. , its configuration is inflexible and complex due to its design.

As a result, not only does the four-wheel drive system itself become complicated, but it also imposes various constraints on the design of the chassis, etc.
In particular, the chassis requires a tunnel structure to accommodate the drive shaft, and the floor structure within the city cannot be made into a uniform flat structure.

An object of the present invention is to provide a four-wheel drive device that eliminates the above-mentioned drawbacks and has increased design flexibility.

[Means for solving problems] The invention consists of the following configuration.

The output power from the engine is configured to mechanically drive either the front wheels or the rear wheels via the main transmission, and the drive from the engine to the one wheel side is configured. A hydraulic pump is linked between the systems,
The hydraulic power output from the hydraulic pump is not configured to drive a first hydraulic motor and a second hydraulic motor, and the first hydraulic motor is configured to drive either the front wheel or the rear wheel. 10. The second hydraulic motor is interlocked with the right wheel on the side of either the front wheel or the rear wheel, and the second hydraulic motor is interlocked with the right wheel on the side of the other wheel of the front wheel or the rear wheel. What is the relative magnitude of the output torque and the output torque of the second hydraulic motor? It is made up of the above structure that allows it to change.

[Operation] In the normal state, that is, the engine mechanically drives the front or rear wheels on one side of the wheel via the main transmission, and the engine is ready to drive the hydraulic pump. The hydraulic pump is configured to drive a first hydraulic motor and a second hydraulic motor, and the output torques of the first hydraulic motor and the second hydraulic motor are normally equal to each other. It becomes.

Under these normal conditions, if one of the wheels driven by the first hydraulic motor or the second hydraulic motor slips on the road surface, the side that is slipping should be If the output torque of the hydraulic motor is reduced, the output power of the engine will effectively drive the hydraulic motor on the side where the slip is not occurring, without causing the engine to run dry due to the slip. Since the output torque of the side hydraulic motor is reduced, slippage with the road surface can be reduced, and the lateral frictional force between the wheel and the road surface can be maintained high.

This increases the running stability of the vehicle on the road surface, and in this case, the wheels on the side that are not slipping on the road surface are effectively driven by the power from the engine, so the heavy vehicle The acceleration performance of the engine will also be degraded.

[Example] Hereinafter, the present invention will be explained based on Examples.

FIG. 1 shows a system diagram of a four-wheel drive device as an embodiment of the present invention.

The engine 1 includes a main transmission 1a, a drive shaft 1b and a de-ZF
(Final deceleration a) Wheels 1e and 1 on the rear wheel side via lc
d, a hydraulic pump 2 is connected to the drive shaft 1b, and the hydraulic pump 2 is connected to the hydraulic pipes 2b and 2.
The hydraulic motor 2f is connected to the right heavy wheel 2 on the front wheel side.
p, and the hydraulic motor 2g is linked to the left wheel 2q on the front wheel side.

Check valves 2d and 2e are interposed between the hydraulic pipes 2b and 2C, and a bypass valve 2h is interposed between the hydraulic pipe 2b and the hydraulic pipe 2C.

A hydraulic pipe 2n is connected between the check valve 2d and the check valve 2e.
A pressure detector 2k is provided in the hydraulic pipe 2n, and the electrical output signal from the pressure detector 2k is input to the calculator 4, and the electric output signal from the pressure detector 2k is inputted to the calculator 4, and the rotation of the accelerator pedal 3 and the rotation of the drive shaft 1b are inputted into the calculator 4. The speed, a depression signal from a brake pedal (not shown), and the rotational speeds of the wheels 2p and 2q are also input to the calculator 4. Note that each of 4a, 4b, and 4C is a rotation speed detector such as an electromagnetic big amplifier.

The displacement volume of the hydraulic pump 2 is the actuator 2
a, the displacement volume in the hydraulic motor 2f is manipulated by the actuator 21, and the displacement volume in the hydraulic motor 2g is manipulated by the actuator 2j. It has a configuration that allows the displacement volume to be varied.

Each of these actuators 2a, 21, and 2j is configured to be operated by a control signal from the calculator 4.

Note that the pressure oil supercharging circuit that uses four check valves of the check valve 2ei, a relief valve, and a hydraulic power source of 2m has a known configuration. The effect will be explained below.

Operation during normal driving: When the vehicle is not in an engine braking state but in a driving state and is traveling straight, the engine 1 operates via the main transmission 1a, the drive shaft 1b, and the differential 1c. The calculator 4 drives the wheels 1e and ld, and
Hydraulic pump 2 and hydraulic motors 2f and 2g as initial values.
The displacement volume of each is set to zero.

In this driving state, the calculator 4 detects 12 the rotational speed of the rear wheel on the drive shaft 1b using the detector 4a.
In addition, on the front wheel side, the rotational speed of the wheel 2p and the rotational speed of the wheel 2q are detected by the detectors 4b and 4C, respectively, and the rotational speed of the wheel 2p and the rotational speed of the wheel 2q are detected.
The rotation speed of the drive shaft 1b is compared with the lower rotation speed of the rotation speed of the drive shaft 1b.

Here, in the comparison, the rotational speed of wheel 2p and wheel 2
The fact that the lower rotational speed of the rotational speed of The coefficient of friction between the wheel 2p or 2g is low, and one of the wheels may slip on the road surface, causing the rotational speed of that wheel to increase. The rotational speed of the wheel on the side that is moving is considered to be the wheel that is not slipping against the road surface.

In this way, when the rotational speed of the front wheels, which are considered not to be slipping with respect to the road surface, is compared with the rotational speed of the drive shaft 1b, the ratio of the rotational speeds of the two is within a predetermined range, for example, the rotational speed of the drive shaft 1b. Rotation speed and that wheel 2p or 2 on the front wheel side
The value obtained by dividing the rotation speed of q by the rotation speed of the drive shaft 1b, that is, the value of the wheels 1e and l relative to the road surface.
In a normal state where the slip ratio S of d is within 10%, the calculator 4
h is opened and the actuator 2a is operated to keep the displacement of the hydraulic pump 2 set to zero.

In this normal driving state, the bypass valve 2h is open as described above, so the hydraulic pressure ¥2b and the hydraulic pipe 2C have the same value, that is, the supercharging pressure from the hydraulic pressure fi2m is in a low pressure state (for example, 5 atm). ).

That is, in this normal state, there is no pressure difference between the hydraulic source 2b and the hydraulic pipe 2C, and as described above, the displacement volumes of the hydraulic motors 2f and 2g are set to zero, and the hydraulic pump Since the displacement volume at 2 is also set to zero, the displacement from the hydraulic pump 2 to the hydraulic motor 2
Hydraulic power is not output to f and 2g, and as a result, hydraulic motors 2f and 2g are not in a state to drive wheels 2p and 2qt, respectively.

Further, in this case, the hydraulic pump 2 and the hydraulic motors 2f and 2g are in a hydraulically unloaded state because the hydraulic pipes 2b and 2c are at the same low pressure value.

Effects when the drive wheels on the main drive side slip against the road surface: The driving force applied to wheels 1e and ld was too large, or the coefficient of friction between wheels 1e and ld and the road surface decreased. By this, wheels 1e and 1d
When slippage occurs between the wheels 1e and 1d and the road surface, the rotational speeds of wheels 1e and ld become higher than the rotational speeds of wheels 2p and 2q.In this way, wheels 1e and 1d slip on the road surface, and the calculation in calculator 4 When it is determined that the slip rate s described in -L exceeds the predetermined slip rate so, the calculator 4 closes the bypass valve 2h and simultaneously controls the actuator 2a as described below.

The oil pressure p of the hydraulic pipes 2b and 2n is a reference value p.

(For example, a value corresponding to 300 atmospheres) When alp-po<0, the displacement volume in the pressure pump 2 is increased until the hydraulic pressure p=po.

b; When p-po=o, fix the displacement volume in the hydraulic pump 2 to the current size, and when cap-po>0, set the displacement volume in the hydraulic pump 2 to p=po
Make it smaller until it becomes .

Enter the above control.

However, at the moment when the control to set p=po is entered, the displacement of the hydraulic motors 2f and 2g is still zero, so the displacement of the hydraulic pump 2 increases by a small amount to the positive side. In a state where a small amount of pressure oil is discharged from the hydraulic pump 2 in an amount corresponding to the leakage loss from each part, the oil pressure of the hydraulic pipes 2b and 2n is controlled to P;po.

In this case, the above control means the following.

The rotational speed of the hydraulic pump 2 is np, its displacement is Dp, and the rotational speed of the wheels 2p and 2q is nm.
, the displacement volume of the hydraulic motor 2f is Dmf, and the displacement volume of the hydraulic motor 2g is Dmg, the pressure oil discharge amount Qp from the hydraulic pump 2 is Qp=npXDp (1), and the hydraulic motors 2f and 2g Pressure oil flow rate Qm flowing into
is, Qm=nmX(Dmf+Dmg) (2),
Assuming that the leakage loss between the hydraulic pump 2 and the hydraulic motors 2f and 2g is zero, from the continuous condition.

Qp=Qm needs to be satisfied.

In other words, the hydraulic energy of the hydraulic pump 2 and the hydraulic motors 2f and 2g can be controlled without discarding the discharged hydraulic energy from the hydraulic pump 2 into a reservoir or without causing a shortage in the pressure oil flow plate from the hydraulic pump 2 that is fed to the hydraulic motors 2f and 2g. 2
In order to perform pure hydraulic transmission between g, it is necessary to satisfy the above Qp=Qm, and from equations (1) and (2), npXDp=nmX (Dmf+Dmg) or Dp= (Dmf+Dmg)Xnp/nm The following conditions must be met.

Here, since the pressure oil discharged into the hydraulic pipe 2b can be considered to be almost an incompressible fluid, if Qp (pressure oil discharge flow rate from the hydraulic pump 2) is to increase even a little with respect to the above Qm, , the operating pressure P of the hydraulic pipe 2b increases, and if the opposite situation occurs, this P will decrease.

Therefore, the above control performs p=po control while satisfying the continuity condition of the above equation (3).

In addition, in this drive, since the pressure oil supply pressure of the hydraulic pipe 2b is always controlled to be constant p+=po, the magnitude of the displacement of each hydraulic pump 2 and hydraulic motors 2f and 2g is determined by the magnitude of their torque. The relationship is proportional to the

In addition, when the wheels 1e and ld are slipping excessively with respect to the road surface in this way, the calculator 4 closes the bypass valve 2h and establishes a control system to keep p=po constant, and at the same time, Subsequently, actuators 21 and 2j are each operated to increase the respective displacement volumes of hydraulic motors 2f and 2g. In this case, the increase equalizes the displacement volume of hydraulic motor 2f and the displacement volume of hydraulic motor 2g. The value of the increased displacement is (S-
SO).

This means that by increasing the displacement volume of the hydraulic motors 2f and 2g as described above, the amount of pressure oil flowing into the hydraulic motors 2f and 2g is increased relative to the amount of pressure oil discharged from the hydraulic pump 2. As a result, the hydraulic pressure p in the hydraulic pipe 2b is about to drop below pO, and as a result, the displacement of the hydraulic pump 2 increases until p=po, following the drop in the hydraulic pressure p. Then the above (3
) will satisfy the formula.

As a result, the wheels 1e and 1d slip more than permissible on the road surface as described above, and the hydraulic pump 2
Pressure oil begins to be discharged to the hydraulic pipe 2b, and the hydraulic power is ready to be sent to the hydraulic motors 2f and 2q via the hydraulic pipe 2b.

Therefore, the generation of hydraulic power by the hydraulic pump 2 creates a new load on the engine l, reducing the output of the engine l that was previously driving the wheels le and ld via the main transmission 1a. I'm going to go.

Therefore, the decrease in the output from the engine 1 to the wheels 1e and ld reduces the driving force of the wheels 1e and ld to the road surface, and as a result, the slip ratio S between the wheels 1e and ld and the road surface decreases. .

For this reason, even if slippage occurs on the road surface on the sides of wheels 1e and ld, the slippage is reduced, and at the same time, the wheels 2p and 2q are controlled by hydraulic power from hydraulic pump 2 via hydraulic motors 2f and 2g. The drive is
It maintains the driving force of the entire vehicle.

On the other hand, when the relationship between the rotational speeds of the wheels 1e and ld returns to the normal state where S<SO with respect to the slower rotational speed side of the wheels 2p or 2q, the calculator 4
returns the displacement of the hydraulic motors 2f and 2g to zero, and according to equation (3) above, the displacement of the hydraulic pump 2 also becomes zero, and the vehicle is driven only by the wheels 1e and ld.

When the wheels 2p or 2q slip on the road surface: In addition to the above control, the calculator 4 also calculates the slip ratio sh between the rotation speed of the right wheel 2p and the rotation speed of the left wheel 2q. There is. In this case, the slip rate sh is the wheel 2p
The difference between the rotational speed of wheel 2q and the rotational speed of wheel 2q is expressed as
It is the value obtained by dividing the rotational speed of wheel 2q by the rotational speed of the higher rotational speed between the rotational speed of wheel 2q and the rotational speed of wheel 2q.In this way, when the slip ratio sh becomes larger than the predetermined slip ratio sho, the calculator 4 calculates , the wheel 2P or 2q
Hydraulic motor 2f or 2g with higher rotation speed
The method of decreasing the displacement volume by decreasing the displacement volume is that the absolute value of the difference between the displacement volume Dmf of the hydraulic motor 2f and the displacement volume Dmg of the hydraulic motor 2g is proportional to (sh-sho). I try to do that.

Here, reducing the displacement volume in this way is because the oil pressure p in the hydraulic pipe 2b is constant pO as described above, so the hydraulic drive torque to the wheel whose displacement volume is reduced is reduced. As a result, the slippage between the wheels and the road surface decreases.

When such a difference in rotation occurs between the wheels 2P and 2q, it is possible that the coefficient of friction between the wheels on one side and the road surface has been reduced, or that the vehicle is turning due to the steering wheel being turned. As a result, the weight of the vehicle shifts toward the outer wheels with respect to the turning center, and as a result, the inner wheels tend to rise above the road surface, which may cause the inner wheels to easily slip on the road surface.

In the latter case, the degree of load applied to the inner and outer wheels can be predicted based on the steering wheel operation and vehicle speed, so the calculator 4 calculates the displacement of the hydraulic motor 2f and the hydraulic motor 2f from the beginning based on the steering wheel operation angle and vehicle speed. 2g
The configuration may be such that the difference between the displacement volume and the displacement volume is appropriately set.

Effect during engine braking: When the accelerator pedal is quickly released or by the subsequent depression of the brake pedal, the calculator 4
The above-mentioned (p-po) control is switched to the following control.

a; When the value of (p-po) becomes a positive value, the displacement of the hydraulic pump 2 is increased in proportion to that value, and b: When the value of (p-po) is zero, the displacement of the hydraulic pump 2 is increased. The displacement is fixed at the current value, and when the value of c; (p-po) becomes a negative value, the displacement of the hydraulic pump 2 is made smaller in proportion to the absolute value of that value, and the control is By doing so, the above-mentioned equation (3) is satisfied.

In addition, in this case, in the process of entering engine braking from a drive state where the accelerator pedal is depressed and returning to engine braking, there is a state where the drive force is intermediate between that drive and engine braking. In that state where the driving force is zero, the wheels 1e and 1d do not slip on the road surface.

Therefore, when the accelerator pedal 3 is returned to zero and the initial driving force becomes zero, the displacement volumes of the hydraulic pump 2 and the hydraulic motors 2f and 2g both temporarily become zero, as described above.

Further, when the accelerator pedal 3 is returned, the calculator 4 keeps the bypass valve 2h closed, and the calculator 4 keeps the bypass valve 2h closed, and the calculator 4 maintains the bypass valve 2h closed in proportion to the return speed of the accelerator pedal 3, or the subsequent depression of the brake pedal. The displacement volumes of the hydraulic motors 2f and 2J are increased in proportion to the strength.

In this case, since the accelerator pedal 3 has been returned to zero, the hydraulic motors 2f and 2g are driven from the wheels 2p and 2q to perform a pumping action. .

Therefore, when the accelerator pedal 3 is released in this way, the hydraulic pipe 2C side becomes the high pressure side, and the hydraulic pipe 2b side becomes the low pressure side, contrary to when driving, and the hydraulic pipe 2C side becomes the low pressure side.
The hydraulic pressure p is transmitted to the hydraulic pipe 2n via the check valve 2d.

As a result of the increased displacement volume of the hydraulic motors 2f and 2g, the pressure oil due to the pump action of the hydraulic motors 2f and 2g is discharged to the hydraulic pipe 2C, and the hydraulic oil is discharged into the hydraulic pipe 2C.
The hydraulic pressure p at C and 2n tends to be higher than pO, but in this case, in order to maintain the relationship of equation (3), the calculator 4 controls the hydraulic pump by controlling p=po in the case of engine braking. The displacement volume of the hydraulic pump 2 is increased until p=po to increase the pressure oil absorption class of the hydraulic pump 2, and the oil pressure p in the hydraulic pipe 2n is maintained at a reference value.

That is, in this engine brake as well, in principle, the displacement volume of the hydraulic valve 2 is controlled while the hydraulic pressure p in the hydraulic pipe 2n is always maintained at the reference value pO.

While satisfying the condition of continuity of the pressure oil IQ amount between the hydraulic pump 2 and the hydraulic motors 2f and 2g (Qm=Qp),
The hydraulic motors 2f and 2g absorb running energy from the wheels 2p and 2q and transmit it as hydraulic power to the hydraulic pump 2, which applies an engine brake to the engine l.

In this way, during engine braking, the wheel 2p
On the 2g side, engine braking is applied to the engine 1 via a pure hydraulic drive system consisting of hydraulic motors 2f and 2g and a hydraulic pump 2, so that the wheels 1e and ld slip on the road surface during engine braking. engine braking will be applied effectively.

Further, in the engine braking described above, when one of the wheels 2p and 2q slips with respect to the road surface, the calculator 4 performs the same control as in the case of driving described above.

In other words, whichever of the wheels 2p and 2q is slipping against the road surface (the frictional force between the road surface and the wheel becomes smaller, the frictional force reduces the force that tries to rotate the wheel, and The method of decreasing the displacement volume of the hydraulic motor (on the side where the rotational speed is low) and making it smaller is the same as when driving, where the difference between the displacement volume of the hydraulic motor 2f and the displacement volume of the hydraulic motor 2g is , is proportional to the difference between the slip ratio sh and the group Q 4 +N shO.

In this way, by reducing the displacement volume on the side that has grown relative to the road surface, and reducing the braking force with the road surface on the side of the wheels (I+i), when the slippage disappears, that is, (sh- When sho) becomes zero, the displacement volumes of the hydraulic motor 2f and the hydraulic motor 2g become small again.

In the above embodiment, the wheels 2p and 2q are described as the front wheels, and the wheels 1e and 1d are described as the rear wheels. , the wheels 1e and 1d may be on the front wheel side.

[Effects of the Invention] As is clear from the above description, the effects of the present invention are as follows.

The output power from the engine mechanically drives either the front wheels or the rear wheels via the main transmission,
Since the wheels on the other side are driven by pure hydraulic drive, l) A mechanical drive shaft is required only on one wheel side, and the drive to the other wheel side is
This means that it can be driven by freely arranged hydraulic pipes.

Therefore, if the engine is installed on the side of the wheel that is driven via the main transmission, when driving the wheel on the other side,
This eliminates the need to provide a conventional mechanical driveshaft tunnel in the chassis, making it possible to design a larger interior.

2) In addition, the drive on the pure hydraulic drive side is only activated when the wheels on the side driven via the main transmission slip more than a predetermined value with respect to the road surface. It is also possible to perform a drive, so when a pure hydraulic drive is used in this way, the pure hydraulic drive is not used all the time, but only when slippage occurs. Therefore, there is almost no deterioration in engine fuel efficiency due to the fact that the power transmission efficiency is lower in pure hydraulic drive than in mechanical power transmission.

3) The wheels driven by the hydraulic motors are individually driven by the first hydraulic motor and the second hydraulic motor, and these hydraulic motors are configured to independently vary their displacement. When one of the wheels driven by a hydraulic motor slips against the road surface, the displacement of the hydraulic motor on that side is reduced to reduce the slippage and improve the lateral stability of the vehicle relative to the road surface. It becomes possible to increase the

In addition, when a vehicle turns, this increases the hydraulic drive torque of the outer wheel, which is driven by a hydraulic motor and carries a large amount of vehicle weight due to the turning, and the external force and turning causes the wheel to rise above the road surface. This makes it possible to reduce the hydraulic drive torque on the inner wheel side that causes stiffness, allowing the vehicle to turn stably.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing an embodiment of a four-wheel drive device according to the present invention. The main symbols used in the examples are as follows. 1: Engine, LA: Main transmission, LB: Drive shaft, IC: Differential, 1e and LD: 4 wheels, 2
: Hydraulic pump, 2a, 21 and 2j: Actuator, 2f and 2g: Hydraulic motor, 2p and 2q: Wheel, 2 = Pressure detector, 4: Calculator,
4a, 4b and 4C: detectors.

Claims (1)

[Claims] 1. The output power from the engine is configured to mechanically drive either the front wheels or the rear wheels via a main transmission, and A hydraulic pump is interlocked between the drive system leading to one wheel side, and the hydraulic power output from the hydraulic pump drives a first hydraulic motor and a second hydraulic motor, and the hydraulic power output from the hydraulic pump drives a first hydraulic motor and a second hydraulic motor. The first hydraulic motor is interlocked with a left wheel on the other side of the front wheel or the rear wheel, and the second hydraulic motor is interlocked with the left wheel on the other side of the front wheel or the rear wheel. or the right wheel on the other wheel side, and the output torque of the first hydraulic motor and the output torque of the second hydraulic motor can be relatively changed in magnitude. , A four-wheel drive device having the above configuration.