JP2680744B2 - Hydraulic drive system for hydraulically driven vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic drive system for a hydraulic traveling vehicle in which an operating member of a traveling hydraulic motor is also used to control the rotational speed of a prime mover.

[0002]

2. Description of the Prior Art As a hydraulic drive device of this type, a full-scale shokai 6
The thing disclosed in the 1-97457 gazette is known. In this hydraulic drive system, when the traveling pedal is depressed,
The traveling flow control valve is opened according to the depression amount, and the engine speed is controlled to be increased. When the traveling pedal is not operated, the engine speed is operated at a predetermined idle speed. In the conventional drive device, the travel pedal is depressed to open the flow rate control valve, and at the same time, the acceleration is started from the idle speed.

[0003]

However, in the diesel engine used in this type of hydraulically traveling vehicle, the engine torque at idle speed is low as shown in FIG. Until the number blows up, there is overtorque, which causes engine stalls or black smoke. Therefore, if the pump input torque is reduced, the desired running performance may not be obtained.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a hydraulic drive system for a hydraulic traveling vehicle, which prevents overtorque at the time of starting and prevents generation of black smoke when the engine speed of the traveling hydraulic motor is also controlled simultaneously. It is in.

[0005]

FIG. 1 shows an embodiment of the present invention.
The present invention will be described with reference to FIG. 4. The present invention relates to a hydraulic pump 1 driven by a prime mover 21 and a traveling hydraulic motor driven by pressure oil discharged from the hydraulic pump 1 to drive a vehicle. 4, a valve means 2 for controlling the operation of the hydraulic motor 4, and an operating means 6 for increasing / decreasing the opening area of the valve means 2 and the prime mover rotation speed according to the operation amount. Applies to equipment. Then, the operating means 6 is used to increase the speed of the prime mover 21 from the idle state to a predetermined rotational speed range, and then the valve means 2 is opened to achieve the above object.

[0006]

The pressure oil is supplied to the traveling hydraulic motor 4 after the speed of the prime mover is increased to a predetermined speed or higher, that is, when the output of the prime mover is equal to or higher than a predetermined value. Does not stop or emit black smoke.

Incidentally, in the section of the means for solving the above problems and the section of the operation which explain the constitution of the present invention, the drawings of the embodiments are used to make the present invention easy to understand. It is not limited to the embodiment.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a wheel type hydraulic excavator will be described with reference to FIGS. 2 and 3 show a traveling hydraulic circuit and an engine speed control device of a wheel hydraulic excavator. In this embodiment, the flow rate to the traveling hydraulic motor is controlled according to the amount of depression of the traveling pedal. The engine speed is also controlled. When the travel pedal is depressed, the engine speed first starts increasing, and then the flow control valve starts to open.

In FIG. 1, a discharge oil from a hydraulic pump 1 driven by an engine (motor) 21 is guided to a traveling hydraulic motor 4 via a counterbalance valve 3 via a hydraulic pilot control valve 2. Has become. The control valve 2 is switched by a pilot hydraulic circuit including a hydraulic pump 5, a pilot valve 6, a slow return valve 7 and a forward / reverse switching valve 8. FIG. 1B is a graph showing the stroke of the control valve spool with respect to the pilot pressure Pi of the pilot hydraulic circuit, where the pilot pressure Pi is P.
The spool starts to move only when it is raised to o.

The governor 21a of the engine 21 is connected to the pulse motor 23 via a link mechanism 22, and the rotation speed of the engine 21 is controlled by the rotation of the pulse motor 23. That is, the rotation speed increases with the forward rotation of the pulse motor 23 and decreases with the reverse rotation. The rotation of the pulse motor 23
It is controlled by a control signal from the controller 24. A potentiometer 25 is connected to the governor 21a.
The potentiometer 25 detects the governor lever position according to the rotation speed of the engine 21, and inputs it to the controller 24 as a governor position detection value Nrp.

The controller 24 is also connected to a fuel lever 26 provided in the cab of the upper revolving structure, an n terminal of a forward / reverse switching switch 27, and a W terminal of a brake switch 28, and is connected to the pilot valve 6 and the forward / backward movement. A pressure sensor 29 provided in a conduit between the switching valve 8 and the switching valve 8 is connected. The pressure sensor 29 detects the pilot pressure Pi generated in proportion to the operation amount of the traveling pedal 6a and inputs it to the controller 24. This pilot pressure Pi is used as the pedal operation amount θp and is also used for engine speed control as described later. The fuel lever 26 is for changing the rotation speed of the engine 21 by a manual operation, and outputs a rotation speed signal No according to the operation amount.

The common terminal of the forward / reverse selector switch 27 is connected to the battery 30, and the f and r terminals are also connected to the solenoid portion of the forward / reverse selector valve 8 via normally closed contacts RS1 and RS2 of the relay R. The forward / reverse switching valve 8 is switched to the N, F, and R positions in accordance with the switching to the f and r positions. When the forward / reverse selector switch 27 is operated to the f position, the forward / reverse selector valve 8 is switched to the F position, to the r position when operated to the r position, and to the N position when operated to the n position. .
Controller 2 when the forward / reverse selector switch 27 is in the n position
A high level signal indicating a neutral state is input to 4.

When the traveling pedal 6a is operated by switching the forward / reverse switching valve 8 to the F position (forward position) or the R position (reverse position), the discharge pressure of the hydraulic pump 5 is controlled by the pilot valve 6, and the operation of the pedal 6a is performed. Is guided to the pilot port 2a or 2b of the control valve 2 via the slow return valve 7 and the forward / reverse switching valve 8. At this time, control valve 2
Is switched in a predetermined direction by a predetermined amount. Of the discharge oil of the hydraulic pump 1 that rotates according to the operation amount of the travel pedal 6a, only the amount corresponding to the switching amount of the control valve 2 is guided to the hydraulic motor 4. As a result, the hydraulic motor 4 is driven and the travel pedal 6
The vehicle moves forward or backward at a speed corresponding to the operation amount a.
At this time, as will be described later, the engine speed is also increased or decreased according to the operation amount of the traveling pedal 6a.

The brake switch 28 is selectively operated in accordance with the operation of the operator during running, parking and working, and its common terminal is connected to the battery 30 and its W terminal is connected to the controller 24. Also this brake switch 2
The W terminal of 8 is also connected to the relay coil RC,
The relay coil RC is excited as the switch 28 is switched to the W position. When the coil RC is excited, the normally closed contacts RS1 and RS2 are opened. In this state, the forward / reverse changeover switch 27 and the forward / rearward changeover valve 8 are cut off, and even if the switch 27 is operated to the f position or the r position. The forward / reverse switching valve 8 holds the neutral position N. In addition, W (work) terminal,
The T (running) terminal and the P (parking) terminal are respectively connected to the solenoid portion of a solenoid valve (not shown), and when operated to the W terminal, the parking brake and the service brake operate,
When the terminal is operated, only the service brake is enabled, and when the terminal P is operated, the parking brake is operated.

The oil discharged from the hydraulic pump 1 is guided to a working hydraulic cylinder 52 via a control valve 51. And the working lever 51a
By operating the control valve 51 to extend and retract the cylinder 52,
Thereby, the work attachment is driven to perform the work. During this operation, the traveling pedal 6 is operated as described later.
The engine speed can be controlled by a, and finer control (fine adjustment) can be performed as compared with the case where the speed control is performed by the fuel lever 26, and noise can be prevented and fuel consumption can be improved without unnecessarily increasing the engine speed. Contribute to.

Next, the engine speed control by the controller 24 will be described with reference to the processing procedure of FIG.
First, in step S1, the governor lever position detection value Nrp input from the potentiometer 25 is read, and the traveling pedal 6a which is the detection value of the pressure sensor 29 is read.
And the operation amount x of the fuel lever, which is the output value of the fuel lever 26, are read.

Next, in step S2, the engine speed Na corresponding to the read displacement x of the fuel lever is calculated based on the illustrated characteristics, and in step S3 the engine speed Na corresponding to the operation amount θp of the travel pedal 6a. Nb is calculated based on the characteristic shown in the figure, and step S4 is performed.
Proceed to. Here, the operation amount θp in step S3, that is, the diagram of the traveling pilot pressure Pi and the target engine speed is shown in detail in FIG. 1 (a), and the idle speed is maintained until the pressure Ps, and the control valve is maintained. The engine speed becomes No at the pressure Po at which the spool 2 starts to move.

In step S4, the calculated rotational speed N
a and Nb are compared, and if Na> Nb, step S5
At step S7, Na is set as the target speed Nro.
If Na ≦ Nb, the target rotation speed Nro is set to Nb in step S6, and the flow advances to step S7.

In step S7, the result of Nrp-Nro is stored in the memory as the rotational speed difference A, and in step S8, | A | ≧ K using a predetermined reference rotational speed difference K.
It is determined whether or not. If the result at step S8 is affirmative, the routine proceeds to step S9, at which it is determined whether or not the rotational speed difference A> 0, and A> 0.
If so, the control speed is higher than the target speed Nro,
In order to lower the engine speed from the current value by a predetermined unit speed ΔN, a signal for instructing the motor reverse rotation is output to the pulse motor 23 in step S10. As a result, the pulse motor 23 rotates in the reverse direction and the rotation speed of the engine 21 decreases by ΔN. Here, the above-mentioned maximum value ΔN of the unit rotation speed is the maximum rotation speed that can be increased or decreased during execution of one loop.

If step S9 is denied, the control rotation speed is lower than the target rotation speed Nro, and therefore the motor forward rotation is performed at step S11 in order to increase the engine rotation speed from the current value by the unit rotation speed ΔN. The command signal is output to the pulse motor 23. As a result, the pulse mode 32 rotates in the normal direction and the rotation speed of the engine 21 increases by ΔN. When step S8 is denied, the routine proceeds to step S12, where a motor stop signal is output, whereby the rotation speed of the engine 21 is held at a constant value. When steps S10 to S12 are executed, the process returns to the beginning.

That is, in the embodiment described above, until the traveling pilot pressure Pi exceeds the predetermined value Ps and reaches Po, only the engine speed is increased as shown in FIG. 1 (a), and the pilot pressure is set to the predetermined value Po. When it exceeds the limit, the spool of the control valve 2 starts to move. As a result, pressure oil is supplied to the traveling hydraulic motor 4 to generate traveling torque after the engine torque becomes equal to or higher than a predetermined value, so that over torque does not occur and engine stall is prevented. Also, generation of black smoke is prevented.

-Other Embodiments-If the opening area diagram of the control valve 2 with respect to the traveling pilot pressure Pi is set as shown in FIG. 5 (b), the spool of the control valve 2 is operated simultaneously with the generation of the traveling pilot pressure Pi. Even if it does, the same effect as described above can be obtained. That is, in the control valve 2, the A-B port communicates with the maximum opening at the neutral position, and the opening area between the A-B ports is gradually closed until the pilot pressure Pi exceeds the predetermined pressure Po. Then, when the predetermined pressure Po is almost reached, the A-B port is shut off. When the pressure exceeds the predetermined pressure Po, P-A
Begin to open between ports and between BT ports. On the other hand, the engine speed is increased when the pilot pressure exceeds the predetermined value Ps, as shown in FIG. 5A, as in the previous embodiment.

In the construction of the above embodiment, the control valve 2 constitutes the valve means, the controller 24 constitutes the prime mover speed control means, and the traveling pilot valve 6 constitutes the operation means. The control valve 2 is an electromagnetic proportional valve, an electric operation member for outputting an electric signal corresponding to the amount of depression of the traveling pedal is provided, and the electric valve controls the control valve and the engine speed. Can be applied.

[0024]

According to the present invention, the traveling hydraulic motor is driven after the output of the prime mover exceeds a predetermined value by the operating means for increasing / decreasing the opening area of the control valve and the number of revolutions of the prime mover according to the manipulated variable. Since the prime mover speed control and the control valve control are set as described above, there is no possibility that the prime mover is undesirably stopped at the time of start-up or that black smoke is emitted.

[Brief description of the drawings]

FIG. 1 is a graph showing traveling pilot pressure, engine speed, and stroke of a control valve spool in an embodiment.

FIG. 2 is a diagram showing a part of a prime mover speed control device and a hydraulic circuit according to the present invention;

FIG. 3 is a diagram showing a remaining portion of FIG. 2;

FIG. 4 is a flowchart when the engine speed control of FIG. 2 is realized by a program.

FIG. 5 is a graph showing traveling pilot pressure, engine speed, and stroke of a control valve spool in another embodiment.

FIG. 6 is a typical rotational speed-output torque diagram of a diesel engine used in a hydraulic construction machine.

[Explanation of symbols]

 1 hydraulic pump 2 control valve 4 hydraulic motor 6 traveling pilot valve 6a traveling pedal 7 slow return valve 8 forward / reverse switching valve 21 engine 21a governor 24 controller 25 potentiometer 27 forward / reverse switching switch 28 brake switch 29 pressure sensor

Claims (1)

(57) [Claims] 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, valve means for controlling the operation of the hydraulic motor, and an operation. Depending on the quantity, the opening area of the valve means and the engine speed
In a hydraulic drive system for a hydraulic traveling vehicle including an operating means for increasing / decreasing the speed, the operating means accelerates the prime mover from an idle state to a predetermined rotational speed range, and then the valve means is opened. A hydraulic drive system for a hydraulically traveling vehicle characterized by the above.