JPH0455131A - Control method in hydraulic drive system - Google Patents

Abstract

PURPOSE:To eliminate response delay at the time of re-accelerating by controlling an acceleration signal on the basis of a depression amount of an accelerator pedal and a vehicle speed in a vehicle driven by a hydraulic drive system of an open circuit. CONSTITUTION:A command current output to a pilot pressure control valve 44 is obtained from an acceleration command value. The valve 44 is switched by a signal and decompresses a pressurized oil from a pump 43 to deliver it as a signal to a traveling control valve 13. At the same time, the pressurized oil decompressed by the valve 44 is delivered to an actuator la to increase the number of revolution of an engine 1 to a specified value Na. According to this, a delivery amount of a pump 11 is increased and the number of revolution M of a motor 15 is shifted to Ma complying with an accelerator 41. At this time, a false idling value alphao of the engine 1 is renewed as required in accordance with the number of revolution M of the motor 15 to be stored in a control part 42. Accordingly, even if a foot is removed from an accelerator pedal to stop depressing, the valve 44 is not abruptly closed and rotates the motor 15 with moderate deceleration.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a control method for a hydraulic drive system, and more particularly to a control method for a hydraulic drive system for a vehicle that runs on an open-circuit hydraulic drive system.

(Prior Art) Conventionally, as a control method for a hydraulic drive system, a configuration shown in FIG. 10 is known. By setting a forward/reverse selector switch (not shown) to the forward or reverse side and depressing the accelerator pedal 101, the rotational speed of the engine 102 increases and the travel control valve 103 is switched. Hydraulic pump 10 driven by engine 102
4 enters the hydraulic motor 106 via the travel control valve 103 and the brake valve 105, and the flow from the hydraulic motor 1
06 rotates. After the speed of the vehicle 100 increases to a certain extent, when the accelerator pedal 101 is released, the rotational speed of the engine 102 decreases and the travel control valve 103 closes. As a result, the brake valve 105 closes, but the hydraulic motor 1
06 is rotated by the inertia of the vehicle 100, and therefore tries to discharge oil by a pump action. However, since brake valve 105 is closed, safety valve 107
increases to the pressure that relieves the hydraulic motor 1.
A reverse drive torque is applied to 06, and a braking force is applied to stop the vehicle 100.

(Problems to be Solved by the Invention) However, the above conventional technology has the following two problems.

■ When the accelerator pedal is released while driving, a strong braking force is applied immediately, and it cannot be used for vehicles that coast due to inertia even if the accelerator pedal is released, such as passenger cars or construction machinery that runs on wheels. .

■ While driving, there is no response even if you release the accelerator pedal and try to accelerate again, or slightly press the accelerator pedal to reduce the deceleration force. In order to weaken the acceleration or deceleration force, it is necessary to press the accelerator pedal deeply.

The above problem is a peculiar phenomenon of open circuit hydraulic circuits, and occurs because there is no "reverse drive" mechanism for driving the engine from the hydraulic motor. In other words, in ■, while the accelerator pedal is depressed, the engine output is controlled by the hydraulic pump, control valve,
It is transmitted to the wheels via the brake valve and hydraulic motor,
When you release the accelerator pedal, the engine speed decreases and the travel control valve closes, which also closes the brake valve, and the reverse driving force generated by the vehicle's inertia is absorbed within the motor circuit (between the hydraulic motor and the brake valve) and becomes large. The brake force will cause the vehicle to stop.

In ■, even if you press the accelerator pedal when you want to accelerate again, the idling engine speed will rise to the specified speed, that is, the pump's discharge flow rate will catch up, the circuit pressure will rise, and the brake valve will open. The time it takes to open is a response delay (time lag).

The present invention has focused on the above-mentioned conventional problems and aims to provide a control method for a hydraulic drive system for a vehicle that runs using an open circuit hydraulic drive system.

(Means for Solving the Problems) In order to achieve the above object, a method is adopted in which an accelerator signal is controlled by the amount of depression of the accelerator pedal and the vehicle speed in a vehicle that is driven by an open-circuit hydraulic drive system.

(Function) According to the above configuration, when the vehicle is stopped, the idling speed of the engine is lowered, but when the vehicle is running, even when the accelerator pedal is not depressed,
The idling speed of the engine is increased according to the vehicle speed, and the travel control valve is also opened.

As a result, the speed of the vehicle is gently decelerated, and the engine speed and the opening degree of the pilot pressure control valve are increased, and the speed of the vehicle is also increased, even without greatly depressing the accelerator.

(Example) Hereinafter, an example of a hydraulic drive system according to the present invention will be described in detail with reference to the drawings. FIG. 1 is an overall configuration diagram of a hydraulic drive system showing a first embodiment of the present invention, and FIG.
The figure is a flow chart diagram of the first embodiment of the present invention.

A hydraulic drive system showing one embodiment of the present invention is an engine 1.
, a hydraulic transmission 10 , a control device 40 , and a mechanical transmission 50 .

The engine 1 is provided with an actuator 1a that controls a fuel injection pump (not shown). The hydraulic transmission device 10 includes a variable displacement expansion hydraulic pump 11 (hereinafter referred to as the pump 11), a hydraulic valve 12, a travel control valve 13, a brake valve 14, and a variable displacement cedar hydraulic motor 15 (hereinafter referred to as the motor 15). ). The pump 11 is provided with a pump capacity control device 20 that controls the displacement and displacement of the pump 11.
is composed of a servo valve 21, a servo piston 22 connected to the servo valve 21, and a flow control valve 23 for controlling the servo valve 21. The motor 15 is provided with a motor displacement control device 3o that controls displacement of the motor 15, and the motor displacement control device 30 is composed of an actuator 31 and a flow control valve 32. Further, the hydraulic transmission device 10 is configured with an open circuit, and is connected by a pump 11, a pipe 16, a travel control valve 13, a pipe 17, a brake valve 14, and a motor 15, and a relief valve 18 is connected to the discharge pipe 16 of the pump 11. A known safety valve 25 is provided between the brake valve 14 and the motor 15.
and a shuttle valve 26 are provided. The travel control valve 13 has a switchboard (bow) 13a, 13 for switching forward and backward movement of the vehicle.
b and neutral bow) 13c are provided, and the tank is returned to the tank 29 when in neutral. In addition, the pipe 1 is branched from the pipe 16.
9. A hydraulic valve 12 is connected to supply and discharge oil to and drive another hydraulic actuator (A). The control device 40 includes an accelerator pedal sensor 41 (hereinafter referred to as the accelerator 41), a control section 42, a control pump 43, a pilot pressure control valve 44, a forward/reverse switching valve 45, and a relief valve 46. , and a rotation sensor 47.

A control section 42 consisting of a controller etc. receives signals from the accelerator 41 and rotation sensor 47 and controls the pilot pressure control valve 45. The pressure oil from the pump 43 is reduced in pressure by the pilot pressure control valve 44 and sent as a signal to the actuator 1a of the engine 1 and to the travel control valve 13 via the forward/reverse switching valve 45. Also, pump 4
The pressure oil from 3 is branched from a pipe 49, one is sent as a signal to the servo valve 21 of the pump 11 via the flow control valve 23, and the other is sent as a signal to the servo piston 22 via the servo valve 21. It is also sent to The rotation sensor 47 detects the rotation speed of the motor and sends it to the control section 42. The relief valve 46 keeps the pilot pressure constant.

The mechanical transmission device 50 includes a gear 52 fixed to the motor shaft 15a, a gear 54 meshing with the gear 52 and fixed to the output shaft 53, and a helical gear 55 fixed to the output shaft 53.
and the drive shaft 5 of the wheel 56 meshing with the helical gear 55.
The helical gear 58 is fixed to the helical gear 7. However, the above-mentioned mechanical transmission device 50 is not used in this embodiment (a reduction gear, a differential device, etc. may also be used).

Next, the operation of the above configuration will be explained.

When engine 1 is started to drive vehicle 100,
Oil is discharged from the pump 11 and the control pump 43. The oil in the pump 11 is at the neutral bow of the hydraulic valve 12)
12c and the neutral boat 13c of the travel control valve 13, it returns to the tank 29. The oil from the pump 43 is kept at a constant pressure by the relief valve 46, and is sent as a signal to the servo valve 21 of the pump 11 via the flow control valve 23. The servo valve 21 receives the signal and closes the boat 2.
Switching from 1a to boat 21c, the displacement of pump 11 sends pressure oil from pump 43 to servo piston 22 in order to increase the volume. At this time, the rotation speed of the engine l is not receiving a signal from the actuator 1a, so
This is the initially set idling rotation speed N. next,
To move the vehicle 100 in a desired direction, either forward or backward, the forward/reverse switching valve 45 is switched. For example, switch to forward baud) 45a. Furthermore, how to move the vehicle 100 will be explained using the flowchart of FIG. The accelerator 41 is depressed, and a predetermined accelerator command value α corresponding to the amount of depression is sent to the control unit 42. In step 1, the control unit 42 reads the accelerator command value α and the rotation speed M of the motor 15. In step 2, a pseudo idle value α0 of the engine 1 is calculated from the rotational speed M of the motor as shown in FIG. 3, and is stored in the control unit 42. In step 3, the accelerator command value αi is obtained from the following equation (1).

α i = (for α / α) × (αm - α0) + αo”・
(1) where αm is the maximum value of the accelerator pedal depression amount. In step 4, the command current Qi to be output to the pilot pressure control valve 44 is determined from the accelerator command value αi as shown in FIG. In step 5, a predetermined command current Qi commensurate with the accelerator command value αi is sent to the pilot pressure control valve 44. The pilot pressure control valve 44 switches from the signal input (44a) to 44b, reduces the pressure of the pressure oil in the pump 43, and sends it as a signal to the travel control valve 13 via the forward movement control valve (45a) of the forward/reverse switching valve 45. The neutral boat 13c is switched to the forward switching boat 13a. At the same time,
The pressure oil whose pressure is reduced by the pilot pressure control valve 44 is transferred to the pipe 4.
8, the actuator la that controls the fuel injection pump
The rotational speed Na of the engine 1 is increased by a predetermined amount. The discharge amount of the pump 11 increases depending on the rotation speed Na of the engine 1,
As a result, the rotational speed M of the motor also becomes the rotational speed Ma of the motor observed on the accelerator 41. At this time, the engine pseudo-idle value αO is updated as needed in accordance with the rotation speed of the motor 15 and stored in the control unit 42. The idling rotation speed Nb is set to be slightly lower than a value that matches the motor rotation speed Ma. Therefore, even if you take your foot off the accelerator and stop pressing it, the control unit 42 outputs a predetermined command current Qo commensurate with the next stored pseudo-idle value α0, so the pilot pressure control valve 44 does not close suddenly. It can only be closed by a predetermined amount. For this purpose, the travel control valve 13 is located in the forward boat 13a, and the pump 11
The discharge amount is the forward boat 13a of the travel control valve 13,
Brake valve 14 bow 1-14 a to motor 15
, and the motor 15 is rotated while being gently decelerated. When a sudden deceleration is desired, a braking device such as a brake (not shown) is operated to apply braking force to the motor 15. As a result, the pressure of the pump 11 increases and the relief valve 18 operates, and the pressure of the signal branched from the piping 16 is sent to the flow control valve 23, which switches the flow control valve 23 from the baud 23b to the servo piston 23a. 22 pressure oil is returned to the tank 29a via the boat 21c of the servo valve 21. Due to the operation of the servo piston 22, the discharge amount of the pump 11 is reduced, and the rotational speed of the motor 15 is also reduced accordingly, resulting in a speed reduction.

Moreover, even if you want to accelerate by loosening the accelerator 41 by -degree and stepping on it again, the pseudo idle value α0 corresponding to the rotation speed of the motor 15 is stored in the control unit 42, and the rotation speed of the engine 1 and the pilot pressure control valve 44 are stored in the control unit 42. Since the opening degree of is set to that position, the rotational speed of the engine 1 and the opening degree of the pilot pressure control valve 44 will increase from that position even if the accelerator 41 is not depressed greatly, the output torque of the motor will increase, and the speed will also increase. Go up.

FIG. 5 shows a second embodiment of the invention. Note that parts that are the same as those in the first embodiment are given the same reference numerals, and explanations thereof will be omitted.

The control device 140 includes an accelerator beta sensor 141 (hereinafter referred to as the accelerator 141), a control pump 43, a pilot pressure control valve 142, and three 2-position, 3-boat control valves, 161.162.163. , a forward/reverse switching valve 45, a relief valve 4G, a pump 151 that detects the rotation of the motor, and a throttle 152. The pressure oil from the pump 43 is one to the boat 142a of the pilot pressure control valve 142, one to the pilot 161m of the first control valve 161, and one to the pilot 161m of the first control valve 161. 2nd fi control valve 16
One is sent to the second boat 162a of the third control valve 163, and one is sent to the third boat 163a of the third control valve 163. Pilot pressure control valve 14
The pressure oil from 2 is sent to the boat 161a of the first control valve 161,
Pressure oil from the control valve 161 is sent to a pilot 162m of the second control valve 162 and a pilot 161n of the control valve 161 itself. One pilot signal from the boat 162a of the second control valve 162 is sent to the tank 29, and one to the second control valve 162.
The pilot 162n of the control valve 162 itself and the third control valve 1
63 pilot 163r. One pilot signal from the third control valve 163 is sent to the tank 29, and one is sent to the boat 45C of the forward/reverse switching valve 46 and the engine 1.
The actuator 1a is connected to the pilot 163m of the forward/reverse switching valve 46 itself. In addition, the third control valve 16
3, one is from the boat 162a of the second control valve, and one is the boat of the third control valve 163 itself)
163a, one is sent from a pipe 154 branched from the pipe 153 of the pump 151. Furthermore, pump 15
Pyro from piping 154 of 1, 7th is the first control valve 161
It is also sent to pylon 161 r I.

Next, the operation of the above configuration will be explained. The control algorithm is the same as in Example 1, but only a hydraulic pilot is used. When the engine 1 is started to drive the vehicle 100 as in the first embodiment, the oil from the pump 43 is kept at a constant pressure Pm by the relief valve 4G, and
The aforementioned pyro throat pressure control valve 142 and three 2-position 3
and to the boat's control valves 161, 162, and 163. The pilot pressure control valve 142 reduces a constant pressure Pm according to the amount of depression of the accelerator 141, and sets the accelerator pedal command pressure value Pa shown in FIG. 6 to the first control valve 161.
Output to. In the first control valve, the pump 151 connected to the motor responds to the pilot pressure Pm from the pump 43.
A pilot pressure pb to the second control valve 162 shown in FIG. 6 is output based on the pilot pressure Po from the first control valve and the pilot pressure pb fed back from the first control valve itself. In the second control valve, the pilot pressure pb of the first control valve 161 and the pilot pressure Pc fed back from the second control valve itself cause the pump 43 to
By reducing the pilot pressure Pm from the third control valve 16
Output pilot pressure PC to 3. In the third control valve, as shown in FIG. The pilot pressure Pm from the pump 43 is reduced, and the pilot pressure Pi of the accelerator command pressure value is output to the boat of the forward/reverse switching valve 45 and the actuator 1a of the engine 1.

As a result, similarly to the first embodiment, the rotational speed N of the engine 1
The discharge amount of the pump 11 increases due to a, and the rotation speed of the motor also becomes Ma. At this time, the idling speed N of the engine is the pseudo idle value α0 as in the first embodiment.
The throttle 152 is set so that the pilot pressure of the pump 151 connected to the motor 15 becomes Po so that the rotational speed Nb corresponds to the rotation speed Nb. Further, at this time, the rotation speed Nb is set to be slightly lower than a value that matches the rotation speed Ma of the motor. As a result, even if you take your foot off the accelerator and stop pressing it, or if you loosen the accelerator by -degree and press it again to increase the speed, the engine rotational speed and the opening degree of the pilot pressure control valve 142 will increase, and the motor 15 will increase in speed. As the output torque increases, so does the speed.

In the above embodiment, the output rotation speed of the hydraulic motor is detected, but the rotation speed of the wheels or the speed of the vehicle may also be detected. Furthermore, although the hydraulic actuator was used to control the fuel injection pump of the engine, it goes without saying that an electric motor, an electronic governor, or the like may also be used.

(Effects of the Invention) As explained above, according to the present invention, when the vehicle is running and the accelerator pedal is not depressed, the idling speed of the engine is increased in accordance with the vehicle speed. At the same time, the opening of the travel control pulp is also kept open, so the vehicle speed can be gently reduced and the engine speed and pilot pressure control valve opening can be increased without having to press the accelerator too much. , the excellent effect of increasing the speed of the vehicle can be obtained.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of a hydraulic drive system showing a first embodiment of the present invention. FIG. 2 is a flowchart of the first embodiment of the present invention. FIG. 3 is a diagram showing the relationship between the hydraulic motor rotation speed and the pseudo idle value. FIG. 4 is a diagram showing the relationship between the accelerator command value and the command current. FIG. 5 is an overall configuration diagram of a hydraulic drive system showing a second embodiment of the present invention. FIG. 6 is a diagram showing the relationship between the accelerator pedal depression amount and the accelerator pedal command pressure. FIG. 7 is a diagram explaining the characteristics of the first control valve. FIG. 8 is a diagram explaining the characteristics of the second control valve. FIG. 9 is a diagram explaining the characteristics of the third control valve. FIG. 10 is an overall configuration diagram of a hydraulic drive system showing a conventional example.・Engine・Hydraulic transmission device・Traveling control pulp・Variable displacement hydraulic pump・Hydraulic pulp・Brake valve・Variable displacement hydraulic motor・Relief valve・Pump displacement control device 21...Servo valve 22...Servo piston 23 ...Flow rate control valve 30...Motor capacity control device 40.140...Control device 41.141...Accelerator beta sensor 42...Control unit 43...Control pump 44.142...・Pilot pressure control valve 45... Forward/backward switching valve 47... Rotation sensor 50... Mechanical transmission 151... Pump 152... Throttle 161.162.163... Control valve

Claims (1)

[Claims] A control method for a hydraulic drive system, characterized in that, in a vehicle running with an open-circuit hydraulic drive system, an accelerator signal is controlled based on the amount of depression of an accelerator pedal and the vehicle speed or the rotational speed of a hydraulic motor.