JPH0745651Y2 - Engine speed control device for hydraulically driven vehicles - Google Patents

Description

[Detailed Description of the Invention] A. Field of Industrial Application The present invention relates to a motor rotational speed control device for a hydraulic traveling vehicle.

B. Conventional Technique This type of conventional device is constructed, for example, as shown in FIG.

In FIG. 6, when the traveling pedal 6a is depressed to operate the pilot valve 6, the oil discharged from the hydraulic pump 5 is controlled by the pilot valve 6, and the hydraulic pilot type control is performed via the slow return valve 7 and the forward / reverse switching valve 8. It is guided to the pilot ports 2a, 2b of the valve 2, and thereby the control valve 2 is switched in a predetermined direction by a predetermined amount. The flow rate and direction of the oil discharged from the hydraulic pump 1 is controlled by the control valve 2, and is guided to the hydraulic motor 4 via the counter balance valve 3. As a result, the hydraulic motor 4 is driven to move the vehicle forward or backward.

When the operation of the travel pedal 6a is released during traveling, the control valve 2
The pressure oil acting on the pilot port 2a or 2b returns to the tank via the forward / reverse switching valve 8, the throttle 7a of the slow return valve 7 and the pilot valve 6. At this time, since the return oil is throttled by the throttle 7a, the control valve 2 gradually returns to the neutral position. That is, when the control valve 2 is suddenly switched to the neutral position, the pressure in the inlet side conduit of the hydraulic motor 4 is suddenly decreased and cavitation is likely to occur. Therefore, the control valve 2 is gradually switched to prevent cavitation. ing. When the control valve 2 returns to the neutral position, the discharge oil from the hydraulic pump 1 is cut off, so that the hydraulic motor 4 is decelerated and the vehicle is decelerated.

Further, the check valves 18a, 18a are provided in the input / output line of the hydraulic motor 4.
The makeup line 19 is connected via b, and makeup oil is supplied from the hydraulic pump 5 to prevent cavitation.

Further, the oil discharged from the hydraulic pump 1 is also guided to the work actuator 12 via the control valve 2 and the switching valve 11 (operated by the lever 13a), which causes the work actuator 12 to move to the lever. It is driven according to the operation of 13a. Further, the oil discharged from the hydraulic pump 14 driven by the prime mover 21 is guided to the work actuator 16 via the switching valve 15 (operated by the lever 17a), which allows the work actuator 16 to operate. Are driven according to the operation of the lever 17a.

On the other hand, the pressure oil whose pressure is controlled by the pilot valve 6 according to the operation of the traveling pedal 6a is guided to the cylinder 45 via the slow return valve 43 including the throttle 41 and the check valve 42 and the electromagnetic switching valve 44, and Accordingly, the piston rod 45a of the cylinder 45 expands and contracts. The tip of the piston rod 45a is connected to the governor 21a of the engine 21 via the link mechanism 46, and the governor 21a is controlled by the expansion and contraction of the piston rod 45a, so that the rotation speed of the engine 21 changes. This rotation speed depends on the operation amount of the traveling pedal 6a.

Further, when the operation of the traveling pedal 6a is released, the bottom chamber of the cylinder 45 is connected to the tank via the pilot valve 6, so that the piston rod 45a contracts by the spring force of the spring 47, thereby controlling the governor 21a. Engine speed decreases. At this time, the return oil from the cylinder 45 is throttled by the slow return valve 43, so that the piston rod 45a gradually contracts, whereby the engine speed also gradually decreases. That is, when the engine speed suddenly decreases, the pressure in the inlet side pipe line of the hydraulic motor 4 suddenly decreases as in the above, so that cavitation easily occurs, and this cavitation is generated from the make-up pipe line 19 described above. Make-up oil alone cannot prevent it. Therefore, the rotation speed of the engine 21 is gradually reduced to reliably prevent cavitation.

Reference numeral 48 is a fuel lever connected to the governor 21a of the engine 21 via link mechanisms 49 and 46.
The engine speed can also be controlled by operating step 8.

The engine speed is adjusted by the link levers 49 and 46 by the fuel lever 48 and the traveling pedal 6a as follows.

When the fuel lever 48 is operated, the link mechanisms 49 and 46 will move to the governor 2
The engine speed is set to a predetermined value by moving 1a by a predetermined amount. In this state, the cylinder 45 piston rod
45a does not move. Then, from this state, the traveling pedal 6a
When stepping on, pressure oil is supplied to the bottom chamber of the cylinder 45, and the piston rod 45a extends. When the governor 21a is moved further than the governor position set by the fuel lever 48 due to the extension of the piston rod 45a, the engine speed further increases.

C. Problem to be Solved by the Invention However, in the above-described conventional device, the slow return valve 7 for delaying the return of the control valve 2 to the neutral position is used.
And the slow return valve 43 for gradually reducing the engine speed, the circuit configuration is complicated. Further, since many components such as the cylinder 45 and the link mechanism 46 are required, the cost is high and there is a problem in reliability. In addition, in order to properly control the engine speed, the cylinder 45 and the link mechanism are required. 46 adjustment work is required and there is a problem in assembling. Furthermore, if adjustments are made due to wear of the link during use,
Proper rotation speed control becomes impossible.

A technical problem of the present invention is to prevent the cavitation with one slow return valve and without using the link mechanism.

D. Means for Solving the Problem Referring to FIG. 1, which is a diagram corresponding to the claims, the present invention relates to a hydraulic pump 102 driven by a prime mover 101 and a hydraulic oil discharged from the hydraulic pump 102. A traveling hydraulic motor 103 for traveling the vehicle and a hydraulic pump 102.
Hydraulic pilot type control valve 104 for controlling the flow rate of the discharged oil from the hydraulic motor and the operation of the hydraulic motor, and a pilot hydraulic power source 105
The operating means 106 for operating the control valve 104 by reducing the pilot hydraulic pressure from the control valve 104 and the control valve 1 provided between the operating means 106 and the control valve 104 to delay the return oil from the control valve 104.
04 Slow return valve that delays the return to the neutral position 10
The present invention is applied to a prime mover speed control device for a hydraulic traveling vehicle equipped with.

Then, the detection means 108 for detecting the line pressure between the slow return valve 107 and the control valve 104, and the target rotation speed is calculated such that the greater the pressure detected by this detection means 108, the higher the prime mover rotation speed becomes. The calculation means 109 and the prime mover control means 110 for controlling the rotation speed of the prime mover 101 to the calculated target rotation speed are provided, thereby solving the above technical problem.

E. Action detecting means 108 detects the line pressure between the slow return valve 107 and the control valve 104. When the operating means 106 is operated in the acceleration direction, this pressure has a value corresponding to the operation amount, and when the operating means 106 is operated in the deceleration direction, it depends on the delay characteristic of the slow return valve 107. It will be a value.

The calculation means 109 calculates the target rotation speed such that the higher the pressure detected by the detection means 108, the higher the prime mover rotation speed, and the prime mover control means 110 calculates the rotation speed of the prime mover 101 by the calculated target rotation speed. To control. According to this, the operating means
By operating 106 in the deceleration direction, the engine speed is gradually reduced and cavitation is prevented.

With the above configuration, only one slow return valve is required, and cavitation can be prevented without using a cylinder or a link mechanism.

F. Embodiments-First Embodiment-A first embodiment in which the present invention is applied to a wheel hydraulic excavator will be described with reference to Figs. 2 and 3.

FIG. 2 is a diagram showing a hydraulic circuit and a control circuit in which the present invention is applied to a wheel type hydraulic excavator, and the same parts as those in FIG. 6 are denoted by the same reference numerals.

In FIG. 2, the direction and flow rate of the pressure oil discharged from the hydraulic pump 1 driven by the engine (motor) 21 is controlled by the hydraulic pilot type control valve 2, and the traveling hydraulic motor is passed through the counter balance valve 3. 4 is supplied.

The stroke amount of the pilot control valve 2 is controlled by the pilot pressure from the pilot hydraulic circuit. The pilot hydraulic circuit has a pilot hydraulic pump (pilot hydraulic source) 5 and a pilot valve 6 (these are operating means) which is interlocked with the traveling pedal 6a, and the control valve 2 is operated by pressure oil from the pilot valve 6. The stroke speed of the vehicle is controlled to control the traveling speed of the vehicle. A slow return valve 7 that delays the return oil to the pilot valve 6 following the pilot valve 6 and a forward / reverse switching valve 8 that follows the slow return valve 7 and selects forward, reverse, or neutral of the vehicle. It is provided. The slow return valve 7 is composed of a throttle 7a and a check valve 7b.

The oil discharged from the hydraulic pump 5 is guided to the pilot port 2a or 2b of the pilot-type control valve 2 through the pilot valve 6, the slow return valve 7, and the forward / reverse switching valve 8, whereby the control valve 2 becomes hydraulic. The stroke amount is changed accordingly. When the control valve 2 returns to the neutral position, the throttle 7a of the slow return valve 7 gives a delay time.

Further, a check valve 18 is provided in the input / output line of the hydraulic motor 4.
A makeup line 19 is connected via a and 18b, and makeup oil is supplied from the pilot hydraulic pump 5 to prevent cavitation. The driving force of the hydraulic motor 4 is transmitted to the transmission via an output shaft (not shown), and the wheels are rotated via the propeller shaft to drive the vehicle.

The above is the configuration of the traveling system.

On the other hand, a pilot type control valve 11 for work is provided in tandem downstream of the travel control valve 2, and the work actuator 12 is drive-controlled by this control valve 11. The control valve 11 is switched by rotating the operation lever 13a of the pilot valve 13. Further, the hydraulic pump 14 driven by the engine 21
A work actuator 16 is connected to the hydraulic pump 14 via a work pilot type control valve 15. The control valve 15 is also an operating lever 17 of the pilot valve 17.
It can be switched by rotating a.

A pressure sensor (detection means) 51 for detecting the pressure P in the pipeline 61 is provided in the pipeline 61 between the slow return valve 7 and the forward / reverse control valve 8, that is, between the slow return valve 7 and the control valve 2.
Is provided. Here, the pressure P of the pipeline 61 depends on the operation amount of the travel pedal 6a when the operation direction of the travel pedal 6a is the acceleration direction (direction in which the travel pedal 6a is depressed) which increases the engine speed. In the deceleration direction in which the engine speed is reduced (the direction in which the travel pedal 6a is released from the depression), the value becomes a value corresponding to the delay characteristic of the slow return valve 7.

Next, a rotation speed control device for the engine 21 will be described.

The rotation speed of the engine 21 is controlled by the governor 21a. The governor 21a is connected to the pulse motor 23 by the link mechanism 22.
The pulse motor 23 is driven according to the rotation of the pulse motor 23 to control the engine speed. A potentiometer 25 is connected to the pulse motor 23 by a link mechanism 24, and the potentiometer 25 detects the rotational position of the pulse motor 23 as a governor lever position detection value Nrp described later. The rotation of the pulse motor 23 is controlled by a motor drive signal from the control circuit 30. Here, the governor 21a and the control circuit 30 constitute a prime mover control means.

The control circuit 30 as a computing means is composed of a microcomputer or the like, and the control circuit 30 includes an engine speed setting device 34 for detecting the operation amount of the fuel lever in the driver's seat and outputting an operation amount signal corresponding thereto. The pressure sensor 51, the pulse motor 23, and the potentiometer 25 are connected. The control circuit 30 includes a rotation speed setting device 34 or a pressure sensor 51.
The governor lever position target value (set rotation speed) Nro calculated based on the output of and the governor lever position detection value which is the detection result of the potentiometer 25 (the engine speed control value by the pulse motor 23, and the actual engine speed is The rotation direction and the rotation amount of the pulse motor 23 are calculated based on (different) Nrp, and a motor drive signal (not shown) is used to create a motor drive signal and supply it to the pulse motor 23.

Next, engine speed control by the control circuit 30 will be described with reference to the processing procedure of FIG.

First, in step S21, the governor lever position detection value Nrp input from the potentiometer 25 is read, and the pressure P of the conduit 61, which is the detection value of the pressure sensor 51, and the fuel lever operation amount, which is the output value of the rotation speed setting device 34, are read. Read x.

Next, in step S1, the engine speed N _A corresponding to the read displacement x of the fuel lever is calculated based on the illustrated characteristic, and in step S2, the engine speed N _B corresponding to the pressure P is set to the illustrated characteristic. Based on the calculation, the process proceeds to step S3. In step S3, the calculated rotation speed
Compare N _A and N _B. If N _A > N _B , set N _A as the target speed Nro in step S4 and proceed to step S22. If N _A ≤N _B , target speed in step S5 Set N _B as Nro and proceed to step S22. That is, the higher one of the rotation speeds N _A and N _B is selected as the target rotation speed Nro.

In step S22, the result of Nrp-Nro is stored in the memory as the rotation speed difference A, and in step S23, it is determined whether or not | A | ≧ K using a predetermined reference rotation speed difference K. When step S23 is affirmed, the routine proceeds to step S24, where it is determined whether or not the rotational speed difference A> O. If A> O, the control rotational speed is higher than the target rotational speed Nro. A signal for instructing motor reverse rotation is output to the pulse motor 23 in S25. As a result, the pulse motor 23 rotates in the reverse direction, and the rotation speed of the engine 21 decreases.

When step S24 is denied, the control rotation speed is lower than the target rotation speed Nro, and therefore a signal for directing the motor to rotate normally is output to the pulse motor 23 in step S25 in order to increase the engine rotation speed. As a result, the pulse motor 23 rotates in the normal direction and the rotation speed of the engine 21 increases.

When step S23 is denied, the routine proceeds to step S27, where a motor stop signal is output, whereby the rotation speed of the engine 21 is held at a constant value. Executing steps S25 to S27 returns to the beginning.

That is, in the above-described embodiment, the control is performed so that the higher engine speed of the engine speed N _A according to the fuel lever operation amount x and the engine speed N _B according to the pressure P in the conduit 61 is set. Is performed.

Hereinafter, the case where the target rotation speed N _B according to the pressure P of the pipe 61 is higher will be described.

At this time, when the operation direction of the travel pedal 6a is the acceleration direction, the pressure P of the pipeline 61 becomes a value corresponding to the operation amount of the pilot valve 6 as described above, so the travel pedal 6a is suddenly depressed. In this case, the engine speed is the value N _B according to the operation.
Increase rapidly until. On the other hand, when the operation direction of the travel pedal 6a is the deceleration direction, the pressure P of the conduit 61 becomes a value according to the delay characteristic of the slow return valve 7, and even when the travel pedal 6a is suddenly released, this delay characteristic is obtained. As a result, the pressure P gradually decreases. Therefore, the engine speed gradually decreases to the target speed Nro, and as a result, cavitation is prevented.

As described above, according to this embodiment, the engine speed is controlled by using the pressure according to the delay characteristic of the slow return valve 7 for delaying the return of the control valve 2 to the neutral position. Only one return valve is required, and cavitation can be reliably prevented without using a conventional cylinder or link mechanism.

If the optimum delay characteristic for gradually reducing the engine speed is different from the optimum delay characteristic for delaying the return of the control valve 2 to the neutral position, the rotation speed N obtained in step S2 A process for setting _B to a value according to the optimum delay characteristic may be added.

In the above description, the pressure P in the conduit 61 between the forward / reverse switching valve 8 and the slow return valve 7 is detected. However, for example, the conduit 62 between the forward / reverse switching valve 8 and the control valve 2 is detected. The same control can be performed by detecting the higher pressure of 63.

-Second Embodiment- Next, a second embodiment of the present invention will be described with reference to Figs.

As shown in FIG. 4, in the circuit of the present embodiment, instead of the above-mentioned pressure sensor 51, a pair of pressures are provided in pipe lines 62, 63 connecting the forward / reverse switching valve 8 and the pilot ports 2a, 2b of the control valve 2. Sensor
52 and 53 are provided, and the sensors 52 and 53 detect the pressures P1 and P2 of the conduits 62 and 63, respectively, and input them to the control circuit 30.

Here, when the travel pedal 6a is operated in the accelerating direction while the forward / reverse switching valve 8 is switched to the forward position (F position) (when the vehicle is moving forward), the pressure P2 in the conduit 62 is the operation amount thereof. When the travel pedal 6a is operated in the acceleration direction when the forward / reverse switching valve 8 is switched to the reverse position (R position) (when the vehicle is reverse), The value depends on the manipulated variable. Further, the pressures P2 and P3 in the pipelines 62 and 63 gradually decrease according to the delay characteristics of the slow return valve 7 when the traveling pedal 6a is operated in the decelerating direction when the vehicle is moving forward and backward, respectively.

FIG. 5 shows the processing procedure of the control circuit 30, and the same steps as those in FIG. 3 are designated by the same reference numerals.

The difference will be mainly described. First, in step S21 ′, the pressures P2 and P3 of the pipes 62 and 63, which are the detection results of the pressure sensors 52 and 53, are read, and the fuel lever operation amount x
And the governor position detection value Nrp is read. Next, in step S1, the rotational speed N _A corresponding to the fuel lever operation amount x is calculated, and in step S51 the rotational speed N _B2 corresponding to the pressure P2 in the conduit 62 is changed to the pressure P3 in the conduit 63 in step S52. The corresponding number of revolutions N _B3 is calculated from the illustrated characteristics, and the process proceeds to step S53. Here, the characteristic of step S52 is such that the rotation speed increases more slowly than the characteristic of step S51.

In step S53, N _A, one has to determine the maximum of N _B2, N _B3, the N _A in step S4 if N _A, the N _B2 in step S54 if N _B2, there in N _B3 For example, in step S55, N _B3 is set as the target rotation speed Nro, and the flow proceeds to step S22. Steps S22-S
Since 27 is the same as described above, the description is omitted here.

According to the above procedure, it is possible to obtain the same effect as that of the first embodiment, and it is possible to change the rotational speed characteristic when the vehicle is moving forward and when the vehicle is moving backward. That is, the displacement x of the fuel lever
Is sufficiently small, the engine 21 is controlled so that the rotation speed is N _B2 when the vehicle is moving forward and the rotation speed N _B3 is when the vehicle is moving backward. The number will be low.

Although the wheel type hydraulic excavator including the hydraulic traveling circuit has been described above, the present invention can be applied to other vehicles having the hydraulic traveling circuit. In addition, although the prime mover speed is set by operating the fuel lever to a desired position, a digital setting method or a method of setting the prime mover speed by providing buttons for increasing and decreasing the engine speed is also possible. Good.

Furthermore, although the method of driving the governor by the pulse motor has been shown, the invention is not limited to this. For example, a linear solenoid may be used to mechanically link the fuel lever and the governor to drive the governor. Often,
The method does not matter.

G. Effect of the Invention According to the present invention, the line pressure between the slow return valve and the control valve is detected, and the higher the line pressure, the higher the engine speed is controlled so that the engine speed is controlled. As a result, the engine speed can be gradually reduced by using the slow return valve for delaying the return to the neutral position of the hydraulic pilot control valve, and
You will be able to do it individually. In addition, since no cylinder or link mechanism is required, cost can be reduced and reliability can be improved, as well as adjustment work for them is not required, assembly is improved, and proper rotation speed control is always possible. .

[Brief description of drawings]

FIG. 1 is a claim correspondence diagram. 2 and 3 show an embodiment in which the present invention is applied to a wheel type hydraulic excavator, FIG. 2 is an overall configuration diagram thereof, and FIG. 3 is a flowchart showing an example of its processing procedure. 4 and 5 are an overall configuration diagram and a flowchart showing a second embodiment of the present invention. FIG. 6 is an overall configuration diagram of a conventional motor rotation speed control device. 1: Hydraulic pump, 5: Pilot hydraulic pump 7: Slow return valve 2: Hydraulic pilot control valve 4: Hydraulic motor, 6: Pilot valve 6a: Travel pedal, 21: Engine 21a: Governor, 23: Pulse motor 25: Potentiometer 30: Control circuit, 31: Pressure switch 34: Engine speed setting device 101: Motor, 102: Hydraulic pump 103: Hydraulic motor 104: Hydraulic pilot type control valve 105: Pilot hydraulic power source 106: Operating means, 107: Slow return Valve 108: Detection means, 109: Calculation means 110: Motor control means

Claims (1)

[Scope of utility model registration request] 1. A hydraulic pump driven by a prime mover, a traveling hydraulic motor driven by pressure oil discharged from the hydraulic pump to drive a vehicle, and a flow rate control of the discharge oil from the hydraulic pump to control the flow rate. A hydraulic pilot type control valve for controlling the operation of the hydraulic motor; an operating means for reducing the pilot hydraulic pressure from a pilot hydraulic pressure source to operate the control valve; and an operating means provided between the operating means and the control valve. In a prime mover speed control device for a hydraulic traveling vehicle, comprising: a slow return valve that delays the return oil from the control valve to delay the return of the control valve to the neutral position. Detecting means for detecting the pipe line pressure, and calculating means for calculating the target rotation speed such that the greater the pressure detected by this detection means, the higher the prime mover rotation speed, A prime mover rotation speed control device for a hydraulic traveling vehicle, comprising: a prime mover control means for controlling the number of revolutions of the motor to reach the calculated target rotation speed.