JPH05331879A - Motor rotation frequency control device of hydraulic driven vehicle - Google Patents

Abstract

PURPOSE:To improve the workability by controlling to convert the motor rotation frequency depending on the pedal depressing amount in an operation, reducing the motor rotation frequency by the passage of time in a running deceleration, and converting the rotation frequency depending on the pedal depressing amount in a running acceleration. CONSTITUTION:When a running pedal 6a is operated to the acceleration side in a running, a controller 33 detects the running condition of a vehicle, and increases the rotation frequency of an engine 21. And when the pedal 6a is operated to the deceleration side, the controller 33 reduces the rotation frequency of the engine 21 proportionally with the passage of time. When a brake switch 36 is converted to the W position at the starting of the work, and a main brake device 108 and a parking brake 106 are operated, the controller 33 detects the working condition of the vehicle. Furthermore, the controller 33 elects a rotation frequency of the engine 21 according to the operating amount of the pedal 6a, and increases or decreases the rotation frequency corresponding to the operating amount, regardless of whether it is in acceleration or deceleration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prime mover speed control device used in a hydraulically driven vehicle such as a wheel type hydraulic excavator.

[0002]

2. Description of the Related Art The present applicant has previously filed Japanese Patent Application No. 2-185876.
In the specification, etc., the engine speed that controls the engine speed and the flow rate supplied to the running hydraulic motor according to the amount of depression of the running pedal during running, and that allows the engine speed to be adjusted using the running pedal during work A controller is proposed. In the engine speed control at the time of this work, the engine speed is controlled according to the travel pedal depression amount, and the engine speed immediately drops to the idle speed when the travel pedal is released. In the present specification, this rotation speed control is usually called prime mover rotation speed control. Further, the applicant previously disclosed in Japanese Patent Application No. Hei 2-182986, etc. that the engine speed is not lowered to the idling speed immediately after the traveling pedal is released during traveling, but is gradually reduced with time. A prime mover speed control device is proposed. This prime mover speed control is referred to as slowdown control in this specification. In this case, during traveling acceleration, the engine speed is increased according to the amount of depression of the traveling pedal, and the flow rate supplied to the traveling hydraulic motor is increased / decreased according to increase / decrease of the amount of depression of the traveling pedal.

[0003]

However, the above-described two prime mover revolution speed control devices are both mounted, and the prime mover revolution speed is controlled so that the engine revolution speed is controlled by the traveling pedal during work and the slowdown control is performed during traveling deceleration. In the case of configuring the number control device, when adjusting the engine speed with the traveling pedal during work, the slowdown control always works on the lower side, which causes a problem of poor operation feeling.

It is an object of the present invention to set a slowdown control for the prime mover rotation speed during traveling deceleration, and to slow down the runner pedal when the prime mover pedal speed is controlled during work. It is an object of the present invention to provide a prime mover rotation speed control device for a hydraulically driven vehicle that normally performs the prime mover rotation speed control without performing control.

[0005]

The present invention will be described with reference to FIGS. 1, 6 and 7 showing an embodiment.
A hydraulic pump 1 driven by a prime mover 21, a traveling hydraulic motor 4 driven by discharged oil from the hydraulic pump 1 during traveling, a working actuator 52 driven by discharged oil from the hydraulic pump 1 during working, Driving speed control of a hydraulically driven vehicle including a running pedal 6a for controlling a running speed according to an operation amount at the time of running, and a rotation speed control means 33 for controlling a driving speed of the prime mover according to a depression amount of the running pedal 6a. Applies to equipment. The above-mentioned purpose is to determine the judgment means 33e (step S4) for judging that the depression amount of the traveling pedal 6a has decreased, and the detection means 33e (step S4) for detecting the traveling state or the working state.
1) is provided, and the motor speed control means 33 is configured as follows. That is, when the working state is detected, the first prime mover speed control is performed,
When the running state is detected and it is determined that the depression amount is decreasing, the second prime mover revolution speed control that reduces the prime mover revolution speed at least with the passage of time different from the first prime mover revolution speed control is performed. To do.

[0006]

When the running state is detected and the vehicle is accelerated by stepping on the running pedal 6a, the number of revolutions of the prime mover is increased according to the amount of stepping. That is, the first prime mover revolution speed control (normal prime mover revolution speed control) is performed. During deceleration by releasing the traveling pedal 6a, the engine speed is not reduced according to the decrease in the depression amount, but the engine speed is reduced over time. That is, the second prime mover speed control (slow down control) is performed. When the work state is detected, the first prime mover speed control is performed regardless of acceleration or deceleration.

Incidentally, in the section of means and action for solving the above-mentioned problems for explaining the constitution of the present invention, the drawings of the embodiments are used for the purpose of making the present invention easy to understand. It is not limited to.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a rotation speed control device for a wheel hydraulic excavator will be described with reference to FIGS. As shown in FIG. 5, the wheel hydraulic excavator has an upper swing structure US and a lower traveling structure LT, and a work attachment AT is attached to the upper swing structure US. Figure 1 shows the running hydraulic circuit of this type of hydraulic excavator,
The rotation speed control circuit and the brake circuit are shown. 2 to 4 are enlarged views of the respective parts of FIG.

1 to 4, an engine (motor) 2
The discharge oil from the hydraulic pump 1 driven by 1 is guided to the traveling hydraulic motor 4 via the hydraulic pilot type control valve 2 and the counter balance valve 3. This control valve 2 includes a hydraulic pump 5, a pilot valve 6,
Switching control is performed by a pilot hydraulic circuit including a slow return valve 7 and a forward / reverse switching valve 8.

Governor 21a of engine (motor) 21
Is connected to a pulse motor 32 via a link mechanism 31, and the rotation speed of the engine 21 is controlled by the rotation of the pulse motor 32. That is, the rotation speed increases when the pulse motor 32 rotates in the forward direction and decreases when it rotates in the reverse direction. This pulse motor 3
The rotation of 2 is controlled by a control signal from the controller 33. The governor 21a also has a potentiometer 34.
The potentiometer 34 detects the governor lever position according to the rotation speed of the engine 21 and inputs it to the controller 33 as a governor position detection value Nrp.

The controller 33 also includes an upper revolving structure U.
The fuel lever 23 provided in the operator's cab of S, the n terminal of the forward / reverse switching switch 35, and the W terminal of the brake switch 36 are connected, and the pilot valve 6 and the forward / reverse switching valve 8 are connected.
A pressure gauge 37 provided in a pipe line between and is connected. The pressure gauge 37 detects the pilot pressure Pi generated in proportion to the operation amount of the traveling pedal 6a and inputs it to the controller 33. The fuel lever 23 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 35 is connected to the battery 38, and the f and r terminals are connected to the solenoid portion of the forward / reverse selector valve 8 through normally closed contacts RS1 and RS2 of the relay R, n and n, respectively. 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 35 is in the n position, a high level signal indicating a neutral state is input to the controller 33.

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

The brake switch 36 is selectively operated in accordance with the operation of the operator during traveling, parking and working, and its common terminal is connected to the battery 38 and its W terminal is connected to the controller 33. Also this brake switch 3
The W terminal of 6 is also connected to the relay coil RC,
The relay coil RC is excited as the switch 36 is switched to the W position. When the coil RC is excited, the normally closed contacts RS1 and RS2 are opened, and in this state, the forward / reverse switching switch 35 and the forward / reverse switching valve 8 are shut off, and the switch 3 is opened.
Forward / reverse switching valve 8 even if 5 is operated to f position or r position
Holds the neutral position N.

The oil discharged from the hydraulic pump 1 is also introduced to a working cylinder (working actuator) 52 via a control valve 51. Then, the control valve 51 is operated by the work lever 51a to expand and contract the cylinder 52, thereby driving the work attachment to perform work. During this work, the engine speed control can be performed by the traveling pedal as described later, and finer control (fine adjustment) can be performed as compared with the case where the fuel lever 23 controls the speed. It contributes to noise prevention and improvement of fuel efficiency without raising.

Further, in FIGS. 1 and 4, reference numeral 100 denotes a brake system, and the brake system 100 is a positive type main braking device 108 for applying a service brake by the compressed air from a compressed air source 101 which sends out compressed air.
The brake is released by the pressure air from the pressure source 100, and the negative type parking brake device 106 applies the brake when the pressure air is exhausted. Further, in this embodiment, the main brake device 108 and the parking brake device 106 are simultaneously applied during work.

The compressed air source 101 is constructed by connecting the delivery side of a compressor 101a operated by the engine 21 to an air tank 101c via a check valve 101b. Further, a relief valve 101d for keeping the internal pressure of the air tank 101c constant is provided. One input conduit 102a connected to the air tank 101c is connected to the input port of the traveling brake valve 103, and the other input conduit 102b is connected to one input port of the brake switching valve 104. Further, the output port of the traveling brake valve 103 is connected to the other input port of the brake switching valve 104. The traveling brake valve 103 outputs a pressure corresponding to the depression amount of the pedal 103a to the output port, and when the petal 103a is released, the output port communicates with the atmosphere port 103b. Further, the brake switching valve 104 is switched to each of the traveling position (T), the parking position (P) and the working position (W) by switching the brake switch 36 to the terminals T, P and W, respectively. The brake switching valve 104 is also provided with an exhaust port 104a.

One output port of the brake switching valve 104 is connected to the negative type parking brake device 106 by a pipe 105, and the other output port of the brake switching valve 104 is connected to the pipe 10.
7 is connected to the positive type main braking device 108. Further, the output port of the traveling brake valve 103 is connected to the main braking device 108 by a conduit 109 in which the check valve 110 is arranged, and allows the compressed air from the traveling brake valve 103 to directly flow to the main braking device 108. To do.

Pipe line 1 connected to the main braking device 108
07 is connected to the input port of the pneumatic-hydraulic pressure conversion booster 108a, and its output port is connected to the brake cylinders 108b of a plurality of wheels. The brake is applied when the brake shoe 108c presses the brake drum 108d by the brake cylinder 108b. Also, 10
8e is a return spring.

The pipe 105 connected to the parking brake device 106 is connected to the input port of the pneumatic-hydraulic pressure conversion booster 106a, and its piston rod 106b is connected to the brake shoe 106d via the brake lever 106c. There is. The brake shoe 106d presses the brake drum 106e to apply a brake. Also,
A return spring 106f is loosely inserted in the piston rod 106b, and the restoring force of the return spring 106f is constantly urged in the direction of applying the parking brake. Therefore, the parking brake device 106 releases the brake when the compressed air is supplied and operates the brake when the compressed air is exhausted.

In the above brake system 100, when the brake switch 36 is switched to the traveling position T, the brake switching valve 104 is switched to the T position shown in the drawing, and the parking brake device 1 is operated.
06 is supplied with pressure from the pressure source 101, the parking brake is deactivated, and when the brake pedal 103a is stepped on, the main brake device 108 is activated during traveling to act as a so-called service brake. Brake switch 3
When 6 is switched to the work position W, the brake switching valve 104 is switched to the W position, and regardless of the depression of the brake pedal 103a, pressurized air is supplied to the main brake device 108 to actuate the service brake and the parking brake device 10
Since the compressed air is exhausted from 6, the parking brake works. That is, a so-called work brake state in which the two brakes work simultaneously is obtained. When the brake switch 36 is switched to the parking position P, the brake switching valve 104 is switched to the P position,
Regardless of the depression of the brake pedal 103a, the compressed air is exhausted from the parking brake device 106 to operate the parking brake. The main braking device 108 operates by depressing the brake pedal 103a.

FIG. 6 is a conceptual diagram for explaining the details of the controller 33. The controller 33 includes two function generators 33a and 33b, a selection circuit 33c, a maximum value selection circuit 33d, a delay control circuit 33e, and a servo control circuit 33.
f and Andgade 33g and 33h.

Pilot pressure Pi detected by pressure gauge 37
Is also input to the function generators 33a and 33b and the delay control circuit 33e. The function generators 33a and 33b use the pilot pressure P
The rotation speeds Nt and Nd determined by the functions (revolution speed characteristics) L1 and L2 in which i is associated with the target rotation speed of the engine 21 are output. The function L1 is a traveling rotation speed characteristic suitable for traveling, and the function L2 is a working rotation speed characteristic suitable for performing work using the work attachment AT. L1 is L
The rotation speed rises sharper than 2 and the maximum rotation speed is also set higher. That is, the engine speed control can be performed by the traveling pedal 6a with the rotational speed characteristic suitable for the work at the time of working, and the engine rotational speed control with the traveling pedal 6a with the rotational speed characteristic suitable for the traveling at the time of traveling.

The selection circuit 33c has a traveling speed characteristic L1.
Has a fixed contact X connected to the function generator 33a that outputs the rotation speed Nt, and a fixed contact Y connected to the function generator 33b that outputs the rotation speed Nd according to the working rotation speed characteristic L2, and is also grounded. The fixed contact Z which is When the fixed contact Z is connected, a rotation speed signal indicating a rotation speed lower than the idling rotation speed is selected. The selection circuit 33c is switched by signals from the AND gates 33g and 33h.

The non-inverting input terminal of the AND gate 33g is connected to the W terminal of the brake switch 36 and the forward / reverse selector switch 3
5 is connected to the neutral terminal n. The inverting input terminal of the AND gate 33h is connected to the W terminal of the brake switch 36 and the neutral terminal n of the forward / reverse switching switch 35, and the non-inverting input terminal is connected to the pressure gauge 37. Here, when the brake switch 36 is switched to the W position, its W terminal becomes high level, and T, P
At the position, the W terminal becomes low level. When the forward / reverse selector switch 35 is switched to the neutral position n, the neutral terminal n becomes high level, and the n terminal becomes low level at the f and r positions. When the travel pedal 6a is depressed, the pressure gauge 3
The signal from 7 goes high. Therefore, the traveling signal output from the AND gate circuit 33h is at a high level during traveling, and the working signal output from the AND gate circuit 33g is at a high level during operation.

The engine speed signal from either the function generator 33a or 33b or the low speed signal from the fixed contact Z is selected according to the switching position of the selection circuit 33c and is input to the maximum value selection circuit 33d. It The fuel lever 23 is connected to the other input terminal of the maximum value selection circuit 33d.
Is also input to the delay control circuit 33e as the target rotation speed Nroa.
The delay control circuit 33e receives the output signals of the AND gates 33g and 33h indicating the traveling state or the working state, and the pilot pressure Pi indicating the travel pedal depression amount,
The delay control circuit 33e controls the governor lever position target value Nr.
o is calculated and input to the servo control circuit 33f. The current engine speed, that is, the governor lever position detection value Nrp is input from the potentiometer 34 to the servo control circuit 33f.
Performs control for changing the engine speed to the governor lever position target value Nro according to the procedure shown in FIG. That is, the two circuits 33e and 33f perform slow-down control only when the vehicle is decelerating, and in other cases, perform normal rotation speed control according to the amount of depression of the traveling pedal.

FIG. 7 shows a control procedure when the delay control circuit 33e and the servo control circuit 33f are realized by a program. And gated 33g, 33 in step S1
It is determined whether the vehicle is running or working based on the signal from h. If the output signal of the AND gate 33g is at a high level, it is determined to be work, and if the output signal of the AND gate 33h is at a high level, it is determined to be traveling. If it is determined that the vehicle is running, the process proceeds to step S2. When it is determined in step S2 that the operation amount θp of the pedal 6a is equal to or larger than the predetermined value θpo, the deceleration flag F is set to 1 in step S3, and the process proceeds to step S4 to determine whether the current Nroa is smaller than the previous value Nro1. judge. Where N
If roa <Nro1, it means that the traveling pedal 6a
Is being operated in the deceleration direction, that is, a deceleration command has been issued.

When the step S4 is denied, that is, when it is determined that the deceleration direction is not operated, the deceleration flag F is set to zero in the step S5, and the step S1 described later is executed.
2, the process proceeds to step S6 if the determination in step S4 is affirmative, that is, if it is determined that the vehicle is being operated in the deceleration direction.
Then, it is determined whether the variable i is zero. This variable i
Shows how many times the control loop of FIG. 7 was repeated. Further, the deceleration flag F is set to 1 in step S3 and is set to zero in step S5 after the step S4 is denied. Therefore, the flag F being 1 indicates that deceleration operation is performed. ing.

If step S6 is positive, step S7
Then, the variable i is set to a predetermined value io (however, io> 0), and the process proceeds to step S8. Nro1-ΔN is set to Nro and the process proceeds to step S9. In step S9, Nro1 is the current N
Substitute ro and proceed to step S21. On the other hand, if step S6 is denied, i is set to "-" in step S10.
1 ", and Nro is set to Nro1 in step S11, and the process proceeds to step S9.

If step S2 is denied,
In step S14, it is determined whether or not the deceleration flag F is 1, and if affirmative, the process proceeds to step S4, and if negative, i is set to a predetermined value io in step S12, and step S1
In step 3, Nro is set to Nroa, and the process proceeds to step S9.

In step S21, the difference Nr between the current governor lever position and the governor lever target value indicating the target rotational speed.
p-Nro is obtained, and the result is stored in the memory as the rotation speed difference A, and in step S22, it is determined whether or not | A | ≧ K using a predetermined reference rotation speed difference K. If the result at step S22 is affirmative, the routine proceeds to step S23, at which it is determined whether the rotational speed difference A> 0. If A> 0, the current control rotational speed is higher than the target rotational speed Nro. In step S24, a signal for instructing the motor reverse rotation is output to the pulse motor 32 in order to decrease the unit rotational speed ΔN from the value of the above. As a result, the pulse motor 32 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 rotational speed is the maximum rotational speed that can be increased or decreased while executing one loop.

If step S23 is denied, the control rotation speed is lower than the target rotation speed Nro, and therefore the motor forward rotation is commanded in step S25 in order to increase the engine rotation speed from the current value by the unit rotation speed ΔN. The signal to perform is output to the pulse motor 32. As a result, the pulse motor 32 rotates in the normal direction and the rotation speed of the engine 21 increases by ΔN. When step S22 is denied, the routine proceeds to step S26, where a motor stop signal is output, and the rotation speed of the engine 21 is held at a constant value. When steps S24 to S26 are executed, the process returns to the beginning.

Here, steps S1 to S1 described above.
4 shows the processing procedure by the delay control circuit 33e in step S
21 and the following shows the processing procedure by the servo control circuit 33f.

In such an embodiment, the engine speed is controlled as follows. When the brake switch 36 is switched to the W position to start the work, both the main brake device 108 and the parking brake device 106 are operated and the work brake is applied, as described above. At this time, when the forward / reverse selector switch 35 is switched to the neutral position n, the output of the AND gate 33g becomes high level and the selection circuit 33
c is switched to the Y contact. As a result, the function generator 33
The work rotation speed characteristic L2 is selected from b. On the other hand, when the brake switch 36 is switched to the T or P position and the forward / reverse selector switch 35 is switched to the forward position f or the reverse position r, the output of the AND gate 33h becomes high level, and the selection circuit 33c is switched to the X contact. Be done. As a result, the traveling speed characteristic L1 is selected from the function generator 33a.

In the cases other than the above two states, the selection circuit 33c is switched to the Z contact, and the signal showing the rotation speed lower than the idle rotation speed is selected. The rotation speed selected as described above is input to the maximum value selection circuit 33d and compared with the rotation speed No set by the fuel lever 23, and the larger one is selected as the target rotation speed Nroa.
The target rotation speed Nroa is the delay control circuit 33e.
When input to, the target speed Nro is calculated, and N
ro is input to the servo control circuit 33f. Then, according to the procedure shown in FIG. 7, the slowdown control is executed only during traveling deceleration, and in other cases, the normal engine speed control is executed.

That is, when the traveling pedal 6a is operated in the acceleration direction during traveling, the step S4 is denied and the value Nroa selected by the selection circuit 33c is set as the target rotational speed Nro in step S13. The number of rotations rapidly rises according to the operation of the traveling pedal 6a. On the other hand, when the traveling pedal 6a is operated in the deceleration direction, step S4 is affirmed and i = 0.
Only in this case, the target rotation speed Nro is set to a value obtained by subtracting ΔN (unit rotation speed) from the previous value Nro1 (step S8). The variable i is "-" every time the step S10 is passed.
Since the step is incremented by 1 ", when the control loop of FIG. 7 is repeated, step S8 is executed once every predetermined number of times. Therefore, the engine speed decreases in proportion to the passage of time.

When it is determined that the work is performed in step S1, steps S12, 13, 9 and steps S21-26 are performed.
Since the engine speed is controlled by the loop of, the slowdown control is not performed even when the travel depression amount is decreased, the normal engine speed control is executed, and the operation when controlling the engine speed with the travel pedal during work is performed. Feeling is improved.

In the above embodiment, the controller 3
3 determines that the vehicle is in the working state, the number of rotations N corresponding to the operation amount of the traveling pedal 6a is determined from the working rotation number characteristic L2.
If d is selected and the fuel lever 23 is operated to the idle position, the rotation speed of the engine 21 is controlled to be the rotation speed Nd. When it is determined that the vehicle is in the running state, the rotation speed Nt corresponding to the pedal operation amount is selected from the running rotation speed characteristic L1 and the rotation speed of the engine 21 is controlled to be the rotation speed Nt. Running speed characteristic L1
Has a steeper rise in the rotation speed due to pedal operation than the working rotation speed characteristic L2, and therefore the acceleration performance during traveling is not impaired. In addition, the operability and fuel consumption are improved without undesirably increasing the rotation speed during work.

Further, in the above embodiment, when the brake switch 36 is switched to the W position, the brake switch 3
Relay coil RC from battery 38 through W terminal 6
Is energized to open the normally closed contacts RS1 and RS2. Therefore, the forward / reverse switching valve 8 is held at the neutral position even when the forward / reverse switch 35 is in the f position and the r position. Therefore, when the rotational speed control is performed during operation by operating the travel pedal 6a, there is no possibility that the vehicle will start moving undesirably even if the operator forgets to switch to the neutral position of the forward / reverse switching valve 8.

Further, in the present embodiment, the maximum value selection circuit 33d.
Thus, the engine speed target value determined by the travel pedal 6a and the engine speed target value determined by the fuel lever 23 are compared in magnitude, and the larger value is selected, so that there is also the following advantage. When the work load is heavy, it is desirable to operate the engine at a high rotation speed, but if the engine rotation speed is set in the high rotation range by the fuel lever 23, the travel pedal 6a is stepped on and off to increase or decrease the rotation speed. It is not necessary to do so, and annoying noise is suppressed by increasing or decreasing the engine speed, and the generation of black smoke is also reduced. Furthermore, fuel efficiency is also improved. When the load is light, the engine speed is set in the low speed range with the fuel lever 23, and if the speed is increased or decreased with the traveling pedal 6a as necessary, noise,
It is preferable in terms of fuel efficiency.

Further, in each of the above-described embodiments, the following advantages can be obtained by setting the maximum rotation speed of the prime mover rotation speed characteristic L2 suitable for work higher than the maximum rotation speed set by the fuel lever. (1) If the rotation speed set by the fuel lever can be set to a very high value, it may be constantly used at a high rotation speed, which is preferable in terms of durability of the engine, hydraulic equipment, fuel consumption, noise, etc. Absent. Therefore, if the above setting is made, even if the fuel lever is set to the maximum value, the rotation speed will be limited to an appropriate rotation speed, and the rotation speed can be increased to a desired high rotation range by the pedal only when necessary (during heavy load). The required flow rate can be secured even under heavy load, and the durability of the engine, hydraulic equipment, etc. can be secured to reduce fuel consumption and noise. (2) Even if a special attachment requiring a large flow rate such as a breaker or a crusher is mounted, the pedal operation can be used to obtain the effect of (1).

In the above, the operation amount of the traveling pedal 6a is detected by the pilot pressure gauge 37, but a potentiometer or the like may be directly attached to the traveling pedal 6a to detect the operation amount. Further, the configuration of the controller is not limited to the above. Further, in the above description, one forward / reverse switching valve 8 can be set to three positions of the neutral position and the forward / rearward moving position, but it is composed of two valves, that is, a switching valve that switches between two positions of the forward / rearward moving position and an on-off valve. May be. Furthermore,
In the above, the traveling state is determined by the fact that the brake switch 36 is switched to a position other than the W position, the forward / reverse selector switch is switched to a position other than N, and the traveling pedal is operated. The running state may be determined only by the state of the brake switch or only the state of the forward / reverse selector switch. The work state may be detected by detecting the actual operation of the parking brake device 106 and the main brake device 108, or the running state or the work state may be detected at the actual position of the forward / reverse switching valve 8. Further, although the wheel type hydraulic excavator has been described, the present invention can be similarly applied to other hydraulically driven vehicles.

[0043]

According to the present invention, when the prime mover rotational speed control is performed by the traveling pedal both during traveling and during work, when so-called slowdown control is performed from the viewpoint of cavitation prevention during traveling deceleration, the slowdown is required during work. Since the control is prohibited and the normal engine speed control is performed, cavitation can be reliably prevented during traveling deceleration, and the driving feeling at the time of work can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of a motor rotation speed control device, a hydraulic circuit, and a brake circuit according to the present invention.

FIG. 2 is an enlarged view of each part of FIG.

FIG. 3 is an enlarged view of each part of FIG.

FIG. 4 is an enlarged view of each part of FIG.

[Fig. 5] Side view of a wheel hydraulic excavator

6 is a detailed block diagram of the controller of FIG.

FIG. 7 is a flowchart when the delay control circuit and the servo control circuit in FIG. 6 are realized by a program.

[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 33 controller 33a, 33b function generator 33e delay control circuit 33g work judgment and gated circuit 33h traveling AND gate circuit for judgment 35 Forward / reverse switching switch 36 Brake switch 37 Pressure gauge

Claims (1)

[Claims] 1. A hydraulic pump driven by a prime mover, a traveling hydraulic motor driven by oil discharged from the hydraulic pump during traveling, and a work actuator driven by oil discharged from the hydraulic pump during work. A traveling pedal for controlling a traveling speed according to an operation amount during traveling, and a rotation speed control unit capable of performing a first prime mover rotation speed control for increasing or decreasing the prime mover rotation speed according to a depression amount of the travel pedal. A prime mover rotation speed control device for a hydraulically driven vehicle, comprising: a determining unit that determines that the amount of depression of the traveling pedal is decreasing, and a detecting unit that detects whether the vehicle is in a running state or a working state. The rotation speed control means performs the first prime mover rotation speed control when the working state is detected, the running state is detected, and the depression Is determined to be decreasing, the second prime mover revolution speed control is performed to reduce the prime mover revolution speed at least with the passage of time different from the first prime mover revolution speed control. A motor drive speed control device for a hydraulically driven vehicle.