JP3133523B2 - Control device for four-wheel drive system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a four-wheel traveling device of a traveling vehicle such as a large dump truck for construction equipment.

[0002]

2. Description of the Related Art For example, as disclosed in Japanese Patent Application Laid-Open No. 63-258223, a four-wheel traveling device of a traveling vehicle mechanically transmits the output power of an engine to a rear wheel via a transmission, and transmits the engine power to the engine. There is known a four-wheel drive traveling device which combines a mechanical drive type and a hydraulic drive type in which a variable hydraulic pump is driven by a variable hydraulic pump driven by the discharge pressure oil of the variable hydraulic pump to drive the front wheels. ing.

[0003]

In such a four-wheel traveling apparatus, four wheels travel by controlling the capacity of a variable hydraulic pump and a variable hydraulic motor so that the rotational speeds of the front and rear wheels are synchronized. The capacity of the variable hydraulic pump and the variable hydraulic motor is controlled by the rear wheel rotation speed.

In the above-described four-wheel traveling device, when an abnormality or failure occurs in the mechanical transmission device that mechanically connects the engine and the rear wheels, for example, a failure of the torque converter and the transmission, a drop or breakage of the power transmission shaft, When a failure of the differential machine occurs, the rear wheels cannot be driven by the engine.

In this case, since the capacity of the variable hydraulic pump and the variable hydraulic motor cannot be controlled, the traveling vehicle cannot run because the front wheels cannot be hydraulically driven.

Accordingly, an object of the present invention is to provide a control device for a four-wheel traveling device capable of solving the above-mentioned problems.

[0007]

The output side of the engine 7 is connected to the rear wheel 3 via a mechanical transmission having a transmission 9 and the like, and a variable hydraulic motor 13 for driving the front wheel 2 is connected to the engine 7.
A variable hydraulic pump 15 that is driven by a hydraulic pump, a variable hydraulic pump 15 and a variable hydraulic motor 13 are connected in a circuit. Means for controlling the capacity, a main controller 23 having a normal running mode and an abnormal running mode, and a mode changeover switch 32.
Controls the capacity of the variable hydraulic pump 15 and the variable hydraulic motor 13 according to the rear wheel rotation speed. When the transmission neutral signal is input in the abnormal running mode, the main controller 23 controls the variable hydraulic pump 15 and the variable hydraulic pressure. A control device for a four-wheel traveling device configured to maximize the capacity of the motor 13.

[0008]

[Operation] When the abnormal mode is set by the mode changeover switch 32 and the transmission 9 is set to the neutral position, the capacity of the variable hydraulic pump 15 and the variable hydraulic motor 13 is maximized and the variable hydraulic motor 13 outputs the maximum torque. , Front wheel 2
Can be driven with the maximum driving force, and when the rear wheel 3 cannot be driven due to an abnormal mechanical transmission device connecting the engine 7 and the rear wheel 3, the vehicle can run with the maximum traction force using the variable hydraulic motor 13 and the variable hydraulic pump 15.

[0009]

1, a pair of left and right front wheels 2 and a pair of right and left rear wheels 3 are mounted on the front and rear portions of a vehicle body 1, and a driver's cab 4 is provided on the front portion of the vehicle body 1. As shown in FIG. , Body 1
A body 5 is attached to the rear of the vehicle by a hoist cylinder 6 so as to be able to move up and down to form a large dump truck for construction equipment. The output side of an engine 7 attached to the front of the vehicle body 1 is connected to a pair of left and right rear wheels 3 via mechanical transmission devices such as a torque converter 8, a transmission 9, a power transmission shaft 10, and a differential gear 11, and Wheel 3 is mechanically driven by engine 7.

As shown in FIG. 2, the front wheel 2 is rotatably supported by an arm 12 which is supported to be able to swing with respect to the vehicle body. The output side of the variable hydraulic motor 13 is connected to the front wheel 2 via a clutch 14, and the discharge pressure oil of a variable hydraulic pump 15 driven by the engine 7
The power is supplied to the variable hydraulic motor 13 in the second main circuits 16 and 17. This variable hydraulic pump 15 can reverse the discharge direction.

As shown in FIG. 2, the rotation speed of the engine 7 is detected by an engine rotation sensor 18, the input shaft rotation speed of the transmission 9 is detected by an input shaft rotation sensor 19, and the speed stage of the transmission 9 is speed. Detected by the step detection sensor 20, the first
The hydraulic pressures of the second main circuits 16 and 17 are detected by first and second pressure sensors 21 and 22, and the detected values are input to a main controller 23, which sends an engine speed to an accelerator sensor 24. Control signal, brake signal from brake sensor 25, retarder brake signal from retarder sensor 26, four-wheel drive signal from changeover switch 27, two-wheel drive signal, steering angle signal from steering angle sensor 28, front wheel rotation signal from front wheel rotation sensor 29 Are respectively input.

The clutch 14 is of a hydraulically actuated type, and is brought into contact when pressure oil is supplied to its pressure receiving chamber 14a, and is turned off when it is discharged to a tank. The discharge pressure oil of the auxiliary hydraulic pump 31 such as a charge pump is supplied, and the clutch switching valve 30 is switched from the drain position a to the supply position b by energizing the solenoid 30a.

The variable hydraulic motor 13 and the variable hydraulic pump 15 are provided with a displacement control member 40 as shown in FIG. 3, and the displacement control member 40 is operated by a cylinder 41 in forward and reverse directions to control the displacement in forward and reverse directions. The discharge pressure oil of the control hydraulic pump 42 is supplied to the cylinder 41 by an electromagnetic proportional valve 43, and the first and second solenoids 43 a and 43 b of each electromagnetic proportional valve 43 are supplied to the cylinder 41 by the main controller 23. Output a signal.

For example, when power is supplied to the first solenoid 43a, the displacement control member 40 operates in the forward direction, the variable hydraulic pump 15 discharges pressure oil to the first main circuit 16, the variable hydraulic motor 13 rotates forward, and When the second solenoid 43b is energized, the displacement control member 40 operates in the reverse direction, the variable hydraulic pump 15 discharges pressure oil to the second main circuit 16, the variable hydraulic motor 13 rotates in the reverse direction, and the displacement becomes the first and second displacements. Solenoid 43a,
It is proportional to the amount of current supplied to 43b.

The main controller 23 has a normal running mode 23a and an abnormal running mode 23b. When a normal running mode signal is input from the mode switch 32, the main controller 23 enters the normal running mode, and inputs the abnormal running mode signal. Then, the driving mode becomes the abnormal mode.

Next, the traveling control operation in the abnormal traveling mode will be described. When the transmission 9 is operated to the neutral position after the abnormal mode 23b is selected by the mode changeover switch 32, a transmission neutral signal is input from the speed stage detection sensor 20 to the main controller 23. The transmission neutral signal may be input to the main controller 23 from a shift operation lever.
This allows the main controller 23 to operate the variable hydraulic pump 15
The maximum amount of current is supplied to the first solenoid 43a of the electromagnetic proportional valve 43 to maximize the capacity, the maximum amount of current is supplied to the first solenoid 43a of the electromagnetic proportional valve 43 of the variable displacement motor 13 to maximize the capacity, and the clutch is switched. Solenoid 30 for valve 30
a, the clutch 14 is brought into contact with the supply position a.

As a result, the discharge amount per rotation of the variable hydraulic pump 15 becomes maximum and the discharge amount per unit time becomes maximum, and the flow rate per rotation of the variable hydraulic motor 13 becomes maximum and the output torque becomes maximum. Therefore, the driving force of the front wheels becomes maximum and the vehicle can travel only by the front wheels 2, and the traction force at that time becomes maximum. This operation is shown in a flowchart of FIG.

As described above, the variable hydraulic pump 15 and the variable hydraulic motor 13 are used when the mechanical transmission device is abnormal such as the failure of the torque converter 8 and the transmission 9, the drop or breakage of the power transmission shaft 10, and the failure of the differential 11. You can run with maximum traction by using.

Next, an example of the travel control operation when the normal travel mode 23a is selected with the mode changeover switch 32 set to the normal travel mode position will be described. However, the present invention is not limited to this travel control operation.

When the changeover switch 27 is turned off and a two-wheel drive signal is input to the main controller 23. (Step 100 in FIG. 5) The clutch switching valve 30 is set to the drain position a, the clutch 14 is disengaged, and the front wheel 2 freely rotates with respect to the variable hydraulic motor 13.
The capacity is set to zero by setting the electromagnetic proportional valve 43 of No. 5 to the neutral position. As a result, the output of the engine 7 is transmitted from the transmission 9 to the rear wheels 3 to perform mechanical drive.

When the changeover switch 27 is turned on and a four-wheel drive signal is input to the main controller 23. (Step 100 in FIG. 5) Proceed to Step 101 in FIG. 5 to determine the abnormality of the hydraulic drive system, take action to notify the abnormality when there is an abnormality, set the capacity of the variable hydraulic pump to zero, and disengage the clutch 14. If there is no abnormality, the routine proceeds to step 102, where the rear wheel slip is determined.

At step 102, it is determined whether the rear wheel 3 is slipping.
The driving force of the front wheel 2 is increased when the vehicle is slipping. That is, when the rear wheel 3 is not slipping, the vehicle can travel sufficiently with the rear wheel driving force. Therefore, the driving force of the front wheel 2 is reduced, the horsepower consumption of the variable hydraulic pump 15 is reduced, and the power loss of the engine is reduced. The front wheel 2
To drive the four wheels.

Next, the slip determination of the rear wheel 3 will be described. The main controller 23 calculates the front wheel rotation speed based on the front wheel rotation speed signal from the front wheel rotation sensor 29, and uses the input shaft rotation speed signal of the input shaft rotation sensor 19 of the transmission 9 and the speed gear signal of the speed gear detection sensor 20 to output the rear wheel. Calculate the rotation speed,
The value obtained by dividing the front wheel rotation speed by the rear wheel rotation speed is within a certain range (for example, 1.1) of 1 or more and for a predetermined time (for example, 0. 1).
(1 second) When it is continuous, it is determined that the rear wheel is slipping. When the value obtained by dividing the front wheel rotation speed by the rear wheel rotation speed is 1 or less, it is determined that the rear wheel is not slipping.

The above description is for a straight running. In a turning running, the front wheel 2 rotates faster than the rear wheel 3 and the rotation speed ratio changes depending on the steering angle. Determine wheel slip. In other words, half of the sum of the rotational speed F _R of the rotation speed F _L and the right front wheel 2 of the left front wheel 2 and a front wheel rotational speed, the main controller 23 previously stores a rotational speed ratio of front and rear wheels by the turning radius (steering angle) Let
The turning radius at that time is calculated based on the steering angle signal from the steering angle sensor 28, a rotation speed ratio corresponding to the turning radius is read as a correction coefficient α, and the correction coefficient α is multiplied by the front wheel rotation speed to obtain a front wheel rotation for comparison. The rear wheel slip is determined in the same manner as described above based on the front wheel rotation speed and the rear wheel rotation speed for comparison.

Next, the magnitude of the driving force of the front wheels will be described. Variable hydraulic pump 1 to reduce the driving force of front wheel 2
5, the pressure of the first or second main circuit 16, 17 is set to a low pressure. Thereby, the variable hydraulic motor 1
Since the pressure of the oil supplied to 3 becomes low, the driving torque of the variable hydraulic motor 13 decreases, and the driving force of the front wheels decreases.

In order to increase the driving force of the front wheel 2, the discharge pressure of the variable hydraulic pump 15, that is, the first or second main circuit 16,
The pressure at 17 is set to high pressure. As a result, the pressure of the oil supplied to the variable hydraulic motor 13 becomes high, so that the driving torque of the variable hydraulic motor 13 increases and the driving force of the front wheels increases.

Specifically, a low pressure and a high pressure are stored in the main controller 23. When the rear wheel does not slip, the low pressure is set as the set pressure, and when the rear wheel slips, the high pressure is set as the set pressure.

After the front wheel drive force is set as described above, the target displacement of the variable hydraulic pump 15 according to the front wheel drive force, that is, the set pressure, is determined, and the main controller 23 sends the target displacement to the first solenoid 43a of the electromagnetic proportional valve 43. Energize to set the variable hydraulic pump to the target capacity. Specifically, the main controller 23 stores the capacity of the variable hydraulic pump 15 corresponding to the set pressure of the low pressure and the high pressure, and the main controller 23 controls the capacity of the variable hydraulic pump by the set low pressure and the high pressure as described above. Then, a current is output to the first solenoid 43a of the electromagnetic proportional valve 43 to obtain the set capacity.

Next, the routine proceeds to step 103, where it is determined whether or not the pressure of the variable hydraulic pump 15 is the set pressure. If the pressure is the set pressure, the capacity of the variable hydraulic motor 13 is controlled in accordance with the vehicle speed.
If the pressure is not the set pressure, the displacement of the variable hydraulic pump 15 is controlled to correct the pressure to the set pressure. Specifically, the main controller 23 detects the pressure of the first main circuit 16 by the first pressure sensor 21, and when the pressure is lower than the set pressure, increases the amount of current supplied to the first solenoid 43 a of the electromagnetic proportional valve 43. Thus, the capacity of the variable hydraulic pump 15 is increased, and when the capacity is high, the amount of electricity supplied to the first solenoid 43a of the electromagnetic proportional valve 43 is reduced to reduce the capacity of the variable hydraulic pump 15.

By controlling the capacity of the variable hydraulic motor 13 according to the vehicle speed (transmission speed stage), the rotation speed of the front wheels 2 can be set to a value corresponding to the vehicle speed even if the capacity of the variable hydraulic pump 15 is constant. For example, when the transmission 9 is in the first gear, the amount of electricity supplied to the first solenoid 43a of the electromagnetic proportional valve 43 is large, the capacity of the variable hydraulic motor 13 is large, and the variable hydraulic motor 13 is rotated at low speed. The amount of power to the first solenoid 43a of the electromagnetic proportional valve 43 is set to medium and the capacity is set to medium speed rotation at the third speed stage, and the amount of power to the first solenoid 43a of the electromagnetic proportional valve 43 is set to small to reduce the capacity. High-speed rotation. That is, the capacity of the variable hydraulic motor 13 is a flow rate during one rotation, and if the capacity is large, the capacity is 1
Since the flow rate at the time of rotation increases, even if the discharge flow rate of the variable hydraulic pump 15 is constant by changing the displacement, the rotation speed changes and the front wheel rotation speed becomes a value corresponding to the vehicle speed (rear wheel rotation speed).

When the capacity of the variable hydraulic motor is controlled in accordance with the vehicle speed as described above, the clutch 140 is brought into contact to drive four wheels. The conditions for engaging the clutch 14 include that the same speed stage is continuous for 1.3 seconds or more, that the engine speed is equal to or greater than a specified value (1070 rpm), and that 1. Two seconds have elapsed, the torque converter mode is maintained, and the speed stage is either the low speed stage or the reverse speed. When these conditions are satisfied, the main controller 23 supplies a current to the solenoid 30a of the clutch switching valve 30 to supply the current. Clutch 14 as position a
Is supplied to the pressure receiving chamber 14a, and the clutch 14 is brought into contact. When one condition is not satisfied, the clutch 14 is turned off. The operation of engaging the clutch 14 is actually different from the flowchart shown in FIG. 4 described above, and is described in FIG. 4 for convenience of explanation.

Next, the setting of the target displacement of the variable hydraulic pump 15 will be described. As described above, the capacity of the variable hydraulic motor 13 is set according to the speed stage, and the variable hydraulic motor 13 is rotated while the capacity of the variable hydraulic pump 15 is kept constant. Is slightly faster, and the four-wheel drive is performed. Therefore, the target displacement of the variable hydraulic pump 15 is determined in consideration of not only the bit pressure but also the reduction ratio of the torque converter 8. That is, since the variable hydraulic motor 15 is driven by the engine 7 and the engine output is transmitted to the rear wheel 3 via the torque converter 8, if the reduction ratio of the torque converter 8 is different, even if the engine speed is constant, the rear wheel 3 , The front wheel 2 and the rear wheel 3 cannot be rotated synchronously as described above.

For this purpose, the reduction ratio of the torque converter is calculated by the following equation based on the engine speed signal input to the main controller 23 and the transmission input shaft speed. Reduction ratio = engine rotation speed / transmission input shaft rotation speed The target displacement of the variable hydraulic pump 15 is corrected by the calculated reduction gear, and the actual displacement of the variable hydraulic pump 15 is set to a value corresponding to the reduction ratio of the torque converter. . Thus, the front wheel 2 and the rear wheel 3 can be synchronously rotated as described above.

In turning, it is important to rotate the front wheel 2 at a higher speed than in straight running in order to make a smooth turn. Therefore, the target displacement of the variable hydraulic pump 15 is corrected by the steering angle. Specifically, the steering angle (turning radius) is known from the steering angle signal input to the main controller 23, and the target displacement of the variable hydraulic pump 15 is increased in proportion to the magnitude of the steering angle, and is proportional to the steering angle. Thus, the variable hydraulic motor 13 is rotated at a higher speed than when the vehicle is traveling straight, and the front wheel 2 is rotated at a higher speed. The amount by which the target displacement of the variable hydraulic pump 15 is increased is determined by the center distance between the front wheel 2 and the rear wheel 3 and the like.

Next, the setting of the front wheel driving force after the rear wheel slip determination will be described. As described above, the front wheel driving force is set to large and small. However, since the operating conditions of the off-road dump truck vary greatly, in order to efficiently drive the four wheels, the driving force is set in multiple stages according to the operating conditions as follows. did.

(1) When the rear wheel 3 is not slipping.
(When the front wheel driving force is small) When earth and sand are not loaded on the body 5 (hereinafter referred to as empty), the set pressure is set to 30 to 150 kg / cm ² . When soil is loaded on the body 5 (hereinafter referred to as loading), the set pressure is set to 50 to 200 kg / cm ² . The set pressure is set to 100 to 250 kg / cm ² when the vehicle is running uphill. The set pressure is set at 125 to 380 kg / cm ² when the vehicle is running uphill.

(2) When the rear wheel 3 is slipping. (When the front wheel driving force is large) When the vehicle is empty, the set pressure is set to 80 to 300 kg / cm ² . When loading, the set pressure is set to 100 to 350 kg / cm ² . The set pressure is set to 200 to 380 kg / cm ² when the vehicle is running uphill. Set the pressure to 300 to 380 kg / cm ² when loading from a slope.
And The above set pressures are the first main circuit 16, that is, the pressure on the high pressure side, and the pressure of the second main circuit 17 on the low pressure side is 25 kg / cm ² .

Next, a case where the variable hydraulic pump 15 and the variable hydraulic motor 13 are used as a brake will be described. Since a large dump truck has a large body weight, braking by a brake and a retarder brake may not be sufficient in some cases. Therefore, the variable hydraulic pump 15 and the variable hydraulic motor 13 provided as four-wheel drive are used as brakes. .

The details will be described below. When a brake signal or a retarder brake signal is input to the main controller 23, the main controller 23
By reducing the amount of current supplied to the solenoid 43a, the capacity of the variable hydraulic pump 15 is made significantly smaller than the target capacity. As a result, the supply flow rate to the variable hydraulic motor 13 is less than the flow rate for rotating the front wheel 2, and the front wheel 2 is rotated by the rear wheel 3, so that the variable hydraulic motor 13 is driven by the front wheel 2 to perform a pump action. I do. When the variable hydraulic motor 13 operates as a pump, the pressure of the second main circuit 17 becomes high and the pressure of the first main circuit 16 becomes low after the vehicle advances, and the second main circuit 1
Since the variable hydraulic pump 15 is driven by the high-pressure oil of No. 7, the rotational resistance of the variable hydraulic pump 15 is significantly increased, and the rotational load of the engine 7 is increased. The overall braking force increases.

Since the braking force acting on the front wheel 2 is determined by the pressure in the second main circuit 17, a pressure for setting the braking force is set in the main controller 23, and the pressure from the second pressure sensor 22 is set. Is greater than the set pressure, the first solenoid 43 of the electromagnetic proportional valve 43 of the variable hydraulic pump 15
By increasing the amount of power supplied to a, the capacity of the variable hydraulic pump 15 is increased, and the pressure in the second main circuit 17 is reduced to set the pressure. By doing so, the braking force of the front wheel 2 can be maintained at the set braking force, and each part can be prevented from being damaged.

The braking force of the front wheel 2 is set according to the operating conditions. The setting of the braking force setting pressure will be described below. (1) When the rear wheel 3 is not slipping. 30 ~ when empty
It is 150 kg / cm ² . 30-160kg when loading
/ Cm ² . 100 to 200 kg / c when the vehicle is downhill
and m ^2. 125 to 200 kg / cm ² when the vehicle is going downhill
And (2) When the rear wheel 3 is slipping. 50-2 when empty
00 kg / cm ² . 50-125kg / when loading
cm ² . 150 to 200 kg / cm when the vehicle is downhill
^{Assume 2} . When the vehicle is going downhill, the load is 150 to 250 kg / cm ² . The pressure of the first main circuit 16 is 25 kg / cm ²
And

[0042]

When the transmission 9 is set to the neutral position by the mode changeover switch 32 and the transmission 9 is set to the neutral position, the capacity of the variable hydraulic pump 15 and the variable hydraulic motor 13 becomes maximum and the variable hydraulic motor 13 outputs the maximum torque. Therefore, the front wheels 2 can be driven with the maximum driving force. Therefore, engine 7
The variable hydraulic motor 13 and the variable hydraulic pump 15 when the mechanical transmission device connecting the
You can run with maximum traction by using.

[Brief description of the drawings]

FIG. 1 is a side view of a large dump truck.

FIG. 2 is a schematic plan view of the four-wheel traveling device.

FIG. 3 is a hydraulic circuit diagram of a variable hydraulic pump / motor.

FIG. 4 is a flowchart of an abnormal-time traveling operation.

FIG. 5 is a flowchart of a normal running operation.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Body, 2 ... Front wheel, 3 ... Rear wheel, 9 ... Transmission, 13 ... Variable hydraulic motor, 15 ... Variable hydraulic pump, 23 ... Main controller, 32 ... Mode switch.

Continuation of the front page (56) References JP-A-63-258223 (JP, A) JP-A-54-157934 (JP, A) JP-A-57-140228 (JP, A) , U) Shokai Sho 62-137129 (JP, U) JP-B 47-10647 (JP, B1) JP-T-Hei 6-503280 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB) Name) B60K 17/28-17/36

Claims (1)

(57) [Claims] An output of an engine (7) is connected to a transmission (9).
Connected to the rear wheel (3) via a mechanical transmission device equipped with
A variable hydraulic motor (13) for driving the front wheels (2) and a variable hydraulic pump (15) driven by the engine (7) are provided;
In a four-wheel traveling device in which the variable hydraulic pump 15 and the variable hydraulic motor (13) are circuit-connected, means for controlling a capacity of the variable hydraulic pump (15);
Means for controlling the capacity of the variable hydraulic motor (13);
A main controller (23) having a normal running mode and an abnormal running mode; and a mode changeover switch (32). In the normal running mode, the main controller (23) is provided.
Controls the capacity of the variable hydraulic pump (15) and the variable hydraulic motor (13) according to the rear wheel rotation speed. When the transmission neutral signal is input in the abnormal running mode, the main controller (23) is changed. Hydraulic pump (15)
And a control device for a four-wheel traveling device configured to maximize the capacity of the variable hydraulic motor (13).