JPH11182443A - Control unit of variable displacement hydraulic pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatically set up the specified value to be smaller than the rated torque of an engine as keeping up the pump absorbing torque of a variable displacement pump almost constant in the case where a speed sensor has failed. SOLUTION: Self-discharge pressure in a variable displacement pump is fed back to a regulator 11 and thereby torque constant control takes place, and actual engine speed N is determined by the equilibrium of input of the variable displacement pump and output of an engine. A control unit 8 calculates the target engine speed N0 from a potentiometer 6, and also calculates the actual engine speed from a speed sensor 7, comparing the target engine speed N0 and the actual engine speed N, and a control current conformed to a deviation between them is outputted to the regulator 11. If the speed sensor gets out of order, a trouble judger 91 selects a connective destination of the regulator 11 to a setter 93, and this setter 93 outputs the regulator 11 with a constant current irrespective of the engine speed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a variable displacement hydraulic pump mainly mounted on a construction machine such as a hydraulic shovel.

[0002]

2. Description of the Related Art Conventionally, a variable displacement hydraulic pump (hereinafter, abbreviated as a variable displacement pump) mounted on a hydraulic excavator.
The self-discharge pressure is fed back to the regulator, and when the discharge pressure of the variable displacement pump set to a predetermined horsepower exceeds the PQ line which is a pump characteristic, the pump displacement is reduced (P- Q control) An overload of the engine is prevented.

On the other hand, the pump absorption torque of a variable displacement pump is usually set to a value lower than the rated torque of the engine in consideration of changes in the output torque of the engine. When the output torque of the engine changes, for example, when the engine itself changes over time, when lean air is drawn into the engine when driving at high altitude, kerosene is used as fuel instead of light oil, which is the regular fuel. Are shown.

If the pump absorption torque is set to a value lower than the rated torque of the engine by a predetermined amount in advance, the engine output is not effectively absorbed by the variable displacement pump. Therefore, as a discharge flow rate control that can use 100% of the engine output even when the operating conditions change,
For example, control by ESS (engine speed sensing) described in Japanese Patent Application Laid-Open No. 58-88480 is performed. This ESS control is to control the discharge flow rate of the variable displacement pump in accordance with the deviation between the target engine speed and the actual engine speed, so that the pump absorption torque can always be set near the engine rated torque. It has become. At present, the discharge amount control of the variable displacement pump is performed by using both the PQ control and the ESS control.

In this case, the discharge pressure is detected by a pressure sensor, and in ESS control, the target engine speed is detected by a potentiometer for detecting the position of a throttle lever, and the actual engine speed is detected by a rotation sensor. The controller calculates the amount of pump displacement based on the pressure detection signal, throttle lever position signal and rotation signal, gives the pump displacement command signal to the electromagnetic proportional pressure reducing valve, and introduces the secondary pressure of the electromagnetic proportional control valve to the regulator. It is supposed to.

[0006]

However, in the above-described control of the conventional variable displacement pump, when the rotation sensor detecting the actual rotation speed of the engine fails, the value of the rotation signal indicating the actual rotation speed is determined. Becomes zero, and the deviation between the target rotation speed and the actual rotation speed becomes the maximum value. When the deviation is at a maximum, the controller sets the pump absorption torque of the variable displacement pump to a minimum value, and as a result, the operation speed of the actuator is significantly lower than the operation speed during normal operation. In this state, since the work cannot be performed substantially, the work must be interrupted until the engine rotation sensor is replaced.

In the control device described in Japanese Patent Publication No. 6-58111, when the controller fails, the operator switches to another redundant circuit so as to prevent the whole operation from being stopped, and a constant current value is applied to the proportional electromagnetic circuit. A method has been proposed in which a regulator is supplied to a valve so that the discharge flow rate of a variable displacement pump is constant. However, in this case,
Since the PQ control does not operate, there is a disadvantage that the pump absorption torque cannot be made substantially constant. Another problem is that it is difficult to determine whether to switch to another redundant circuit.

The present invention has been made in consideration of the above-described problems in controlling the discharge flow rate of a conventional variable displacement pump, and is capable of detecting a failure of a rotation sensor. A control device for a variable displacement hydraulic pump capable of automatically setting the pump absorption torque of the variable displacement pump to a value smaller than the rated torque of the engine by a predetermined amount while keeping the pump absorption torque of the variable displacement pump substantially constant. To provide.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a control apparatus for a variable displacement hydraulic pump which is driven by an engine and whose tilt amount is adjusted by returning a self-discharge pressure to a regulator. Control current generator that outputs the control current of the regulator based on the deviation between the engine speed and the actual rotation speed, and setting for setting the pump absorption torque of the variable displacement hydraulic pump to a torque smaller than the rated torque of the engine by a predetermined amount. A set current generating section for outputting a current, switching means for connecting any one of the outputs of the control current generating section and the set current generating section to the regulator, and switching when an actual engine speed falls below a predetermined value. A failure determination unit that switches the connection destination of the regulator from the control current generation unit to the set current generation unit by switching the means. Control device for a variable displacement hydraulic pump to.

In the present invention, the control current generator can calculate the target rotation speed based on a signal output from a potentiometer for detecting the operation amount of the throttle lever. Also, the actual rotation speed can be calculated based on a signal output from a rotation sensor that detects the engine rotation speed.

In the present invention, the control current generator calculates a target rotation speed based on a signal output from a potentiometer that detects an operation amount of a throttle lever, and converts the target rotation speed into a signal output from a rotation sensor that detects an engine rotation speed. Based on this, the actual rotation speed is calculated based on the actual rotation speed, and a PID operation is performed on the deviation to generate a control current for the regulator.

In the present invention, the set current generator can be constituted by a redundant circuit which automatically outputs a constant current when the rotation sensor fails.

According to the present invention, the self-discharge pressure of the variable displacement pump is fed back to the regulator, and the regulator increases the amount of tilting to increase the pump flow rate when the discharge pressure is low. Conversely, when the discharge pressure is high, the amount of tilt is reduced to reduce the pump flow rate, thereby preventing engine overload. Therefore, first, the actual engine speed is determined by the balance between the input of the variable displacement pump and the output of the engine. The control device calculates, for example, a target rotation speed N ₀ based on a signal output from a potentiometer, and calculates an actual rotation speed N based on a signal output from a rotation sensor,
ESS control is performed by comparing N ₀ and N and outputting a control current corresponding to the deviation to a regulator.

When the rotation sensor fails, the failure determination unit
By switching the switching means, the connection destination of the regulator is switched from the control current generator to the set current generator, and the set current generator reduces the pump absorption torque of the variable displacement pump to a torque smaller by a predetermined amount than the rated torque of the engine. The set current for setting is output to the regulator. However, since the displacement of the variable displacement pump is also controlled by the feedback of the self-discharge pressure, the pump absorption torque of the variable displacement pump is set to a value lower than the rated torque, and the pump absorption torque is kept substantially constant. Dripping.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on preferred embodiments shown in the drawings. FIG. 1 is an overall configuration diagram showing a case where the control device for a variable displacement hydraulic pump of the present invention is applied to a hydraulic shovel.

In FIG. 1, a variable displacement hydraulic pump (hereinafter, abbreviated as a variable displacement pump) 2 is driven by rotation of an engine 1, and a control valve 3 is provided in a discharge side oil passage of the variable displacement pump 2. An actuator 4 for operating a front attachment, a traveling motor, and the like is connected via the power supply.

Reference numeral 5 denotes a throttle lever which is oscillated to adjust the rotation of the engine. The throttle lever 5 is provided with a potentiometer 6 for detecting the operating position. Further, the engine 1 is provided with a rotation sensor 7 for detecting the actual rotation speed of the engine 1.

The rotation sensor 7 is of an electromagnetic pickup type and is disposed near the ring gear of the engine flywheel. The rotation sensor 7 electrically counts the number of teeth of the ring gear passing in front of the rotation sensor 7 and outputs the result as a sine wave pulse signal. Output. When attaching the rotation sensor 7 to the frame, adjust the distance between the tip of the rotation sensor 7 and the peripheral edge of the ring gear, and after confirming that a predetermined voltage is obtained, fix the rotation sensor 7 to the frame using an adhesive,
Tighten with lock nut.

The potentiometer 6 and the rotation sensor 7
Are supplied to a control device 8 composed of a microcomputer, and the control device 8
An engine target rotation speed N ₀ is calculated based on a signal output from the potentiometer 6 and output to the accelerator motor 9.

The accelerator motor 9 changes the engine speed based on the target engine speed N ₀ , whereby the engine speed changes according to the operation amount of the throttle lever 5.

The self-discharge pressure of the variable displacement pump 2 is as follows:
The feedback is fed back to the regulator 11 through the pipe 10, and when the load on the actuator 4 is small, the regulator 11 increases the amount of tilt to increase the pump flow rate,
When the load is large, the tilt amount is reduced to reduce the pump flow rate.

The regulator 11 can operate not only by the self-discharge pressure but also by a command from the control device 8.

FIG. 2 shows the configuration of the regulator 11. In the figure, first, a case where the operation is performed by feedback of the self-discharge pressure Pa will be described. Self discharge pressure Pa of the pipe 10 is led to the port P ₁ (see FIG. 1),
When the self-dispensing pressure Pa increases, the compensating piston 20 is pushed, and the compensating rod 22 is moved rightward against the urging force of the compensating spring 21. At this time, the first pin 23 of the compensating rod groove also moves to the right, so that the compensating lever 24 moves to the right with the fixing pin 25 as a fulcrum, thereby moving the spool 26 to the right.

When the spool 26 moves to the right, the port P
₂ communicates with the port P _3, and the self-discharge pressure P
a is guided, and the servo piston 28 moves to the right. The self-discharge pressure Pa acts on both the large-diameter chamber 27 and the small-diameter chamber 19;
Moves to the right. Since the servo piston 28 is directly connected to the swash plate of the variable displacement pump 2, the discharge flow rate decreases as the swash plate approaches vertical. When the self-discharge pressure Pa decreases, the reverse operation is performed, and the discharge flow rate increases.

Next, a case where the operation is performed by a command from the control device 8 will be described. Solenoid proportional valve 30 is actuated in response to a control signal output from the control unit 8, the secondary pressure Pb of the electromagnetic proportional valve 30 is led to the port P _4. When the secondary pressure Pb increases, the compensating piston 20 is pushed rightward via the fixing pin 25, and the servo piston 28 moves rightward in the same manner as described above, and the discharge flow rate of the variable displacement pump 2 decreases.

Thus, the self-pressure Pa and the control device 8
, The discharge flow rate of the variable displacement pump 2 is controlled.

FIG. 3 is a block diagram showing the configuration of the control device 8. As shown in FIG. In the figure, a signal output from the potentiometer 6 is given to a function generator 80, which calculates an engine target speed N ₀ at each operation position of the throttle lever 5, and sends the signal to an adder 81. give.

On the other hand, the pulse signal output from the rotation sensor 7 is given to a function generator 82, and the function generator 82
The actual engine speed N is calculated based on the cycle of the pulse signal, and is provided to the adder 81.

The adder 81 subtracts the actual engine speed N from the engine target speed N ₀ to calculate a deviation ΔN. ΔN = N ₀ −N The integrator 83, differentiator 84, counters 85 to 87 and adder 88 perform a PID operation on this deviation ΔN. Kp × ΔN + Ki × ∫ΔNdt + Kd × dΔN / dt, where Kp: proportional gain, Ki: integral gain, Kd:
Differential gain

A control current as a calculation result is supplied to a current amplifier 90 through a changeover switch 89 as a changeover means, amplified, and output to the regulator 11.
The changeover switch 89 normally closes.
The circuit 8a that generates a control current according to the above-described deviation ΔN can be regarded as a control current generation unit.

On the other hand, the signal output from the rotation sensor 7 is also branched and input to a failure discriminator (failure discriminating unit) 91. Is calculated, and the calculated actual engine speed N is compared with the reference engine speed Ns stored in the memory 92 in advance, thereby determining the failure of the rotation sensor 7. Specifically, the memory 92 stores a reference engine speed N set in advance according to the engine performance.
s (for example, 300 rpm) is stored, and the actual engine speed N is calculated based on the pulse signal output from the rotation sensor 7, and the calculation result is used as the reference engine speed N
When it is less than s, it is determined that the rotation sensor 7 is out of order. In the present invention, the reason why the failure determination is performed not on the control device 8 but on the rotation sensor 7 is that the probability that the control device 8 fails in the operation of the hydraulic excavator is much smaller than that of the rotation sensor 7. .

The failure determiner 91, which has determined that the rotation sensor 7 has failed, switches the connection destination of the regulator from the circuit 8a to the setter 93 as a set current generator by switching the changeover switch 89. The setting device 93
A predetermined constant current is output, and this constant current is supplied to a current amplifier 90 through a changeover switch 89.
After being amplified, it is output to the regulator 11. Therefore, in this case, the pump absorption torque of the variable displacement pump 2 is set to a torque lower than the rated torque of the engine by a predetermined amount regardless of the engine speed. To set the torque to be lower by a predetermined amount means, specifically, a decrease in output torque due to aging of the engine, a decrease in output torque due to high altitude operation, and a decrease in output torque when a fuel other than regular fuel is used. Is set to the torque obtained by subtracting the largest value of the above. The operation of the control device for a variable displacement pump having the above configuration will be described below.

The self-discharge pressure of the variable displacement pump 2 is
The spool of the regulator 11 via the zero (not shown)
When the discharge pressure is low, the regulator 11 increases the amount of tilt of the swash plate to increase the flow rate. Conversely, when the discharge pressure is high, the regulator 11 decreases the amount of tilt of the swash plate. And act to reduce the flow rate. In this way, the actual rotation speed N of the engine 1 is first determined by the balance between the input of the variable displacement pump 2 and the output of the engine 1.

On the other hand, the control device 8 controls the potentiometer 6
, A target rotation speed N ₀ is calculated based on a signal output from the rotation sensor 7, an actual rotation speed N is calculated based on a signal output from the rotation sensor 7, and N ₀ and N are compared with each other. The output current is output to the regulator 11.

In this state, the constant torque control for keeping the torque of the variable displacement pump 2 constant to prevent overload of the engine 1 and the ESS control for efficiently absorbing the output torque of the engine 1 to the variable displacement pump 2 cooperate. doing.

If the rotation sensor 7 fails during the operation of the hydraulic excavator, the actual engine speed N calculated based on the signal output from the rotation sensor 7 becomes “zero”, and the check value stored in the memory 92 is used. Rotational speed Ns (300
rpm), the failure discriminator 91 switches the changeover switch 89 to change the connection destination from the circuit 8a to the setting device 93. The setting device 93 outputs a constant current to the regulator 11. As a result, the ESS control does not work, and the pump absorption torque of the variable displacement pump 2 is set to a predetermined amount smaller than the rated torque of the engine 1 irrespective of the engine speed.

However, since the control for feeding back the self-discharge pressure of the variable displacement pump 2 to the regulator 11 is working, the torque of the variable displacement pump 2 is kept constant.

The control device for a variable displacement hydraulic pump according to the present invention is not limited to the hydraulic shovel described in the above embodiment, but can be applied to construction machines such as hydraulic cranes.

[0039]

As is apparent from the above description,
According to the present invention, when the rotation sensor fails, the pump absorption torque of the variable displacement hydraulic pump can be automatically set to a value smaller than the rated torque of the engine by a predetermined amount while keeping the pump absorption torque substantially constant. Has advantages.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram in which a control device for a variable displacement pump according to the present invention is applied to a hydraulic shovel.

FIG. 2 is a longitudinal sectional view showing a configuration of the regulator of FIG.

FIG. 3 is a block diagram showing a configuration of a control device shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 2 Variable displacement pump 3 Control valve 4 Actuator 5 Throttle lever 6 Potentiometer 7 Rotation sensor 8 Control device 10 Flow control mechanism

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroaki Iwamitsu 3-12-4 Gion, Asaminami-ku, Hiroshima City Inside Aburaya Heavy Industries, Ltd.

Claims (5)

[Claims] 1. A control device for a variable displacement hydraulic pump driven by an engine and adjusting a tilt amount by feeding back a self-discharge pressure to a regulator, wherein a deviation between a target rotation speed and an actual rotation speed of the engine is provided. A control current generator for outputting a control current of the regulator based on the control current, and outputting a set current for setting a pump absorption torque of the variable displacement hydraulic pump to a torque smaller than a rated torque of the engine by a predetermined amount. A setting current generator, switching means for connecting any one of the outputs of the control current generator and the set current generator to the regulator, and when the actual engine speed falls below a predetermined value, Failure determination for switching a connection destination of the regulator from the control current generation unit to the set current generation unit by switching a switching unit. When the variable displacement hydraulic pump control apparatus characterized by comprising comprises a. 2. The variable displacement type according to claim 1, wherein the control current generator is configured to calculate the target rotational speed based on a signal output from a potentiometer for detecting an operation amount of a throttle lever. Control device for hydraulic pump. 3. The variable according to claim 1, wherein the control current generator is configured to calculate the actual rotation speed based on a signal output from a rotation sensor that detects an engine rotation speed. Control device for displacement hydraulic pump. 4. The control current generator calculates the target rotation speed based on a signal output from a potentiometer that detects an operation amount of a throttle lever, and outputs a signal output from a rotation sensor that detects an engine rotation speed. 2. The control device for a variable displacement hydraulic pump according to claim 1, wherein the control device is configured to calculate the actual rotation speed based on the following formula, and perform a PID operation on the deviation to generate a control current for the regulator. 3. 5. The control device for a variable displacement hydraulic pump according to claim 1, wherein the set current generating section is configured by a redundant circuit that outputs a constant current.