JPH0535275B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an input limiting device for a hydraulic pump driven by an internal combustion engine, and in particular, the target rotation speed of the internal combustion engine is set according to the amount of operation of a control lever that controls a hydraulic actuator, and The present invention relates to a hydraulic pump input limiting device that controls the input horsepower of the hydraulic pump so that it does not exceed the output of an internal combustion engine.

FIG. 1 is a block diagram showing an example of a conventional input limiting device for a hydraulic pump driven by an internal combustion engine. In this figure, 1 is an internal combustion engine, 2 is a fuel injection pump for this internal combustion engine 1, 3 is a variable displacement hydraulic pump driven by the internal combustion engine 1, and 4 is a discharge capacity that controls the discharge capacity of this hydraulic pump 3. It is a control mechanism. Reference numeral 5 indicates a control valve that is connected to the hydraulic pump 3 and drives a hydraulic actuator (not shown), and 6 is a pressure detector disposed in a circuit that communicates the hydraulic pump 3 and the control valve 5. 7 is a throttle lever that sets the target rotation speed of the internal combustion engine 1; 8 is a rotation speed detector that detects the output rotation speed of the internal combustion engine 1; 9 is a rotation speed detector that detects the target rotation speed signal N output from the throttle lever 7; number detector 8
Compare the output rotation speed signal Ne output from
A comparator 10 for determining the rotation speed deviation, which is the difference between them, is a fuel injection pump controller that outputs a control signal to the fuel injection pump 2 in accordance with the rotation speed deviation signal ΔN output from the comparator 9. Also, 11 is
An operation lever for controlling the control valve 5, 1
2 is the rotation speed deviation signal ΔN output from the comparator 9
and a horsepower control function generator that outputs a _pump discharge volume signal X _H in accordance with the pressure signal P output from the pressure detector 6; vessel 12
This is a minimum value selection circuit that selects the minimum value of the pump discharge volume signal _XH output from the pump discharge volume signal XH and outputs the discharge volume control signal X to the discharge volume control mechanism 4.

The operation of the conventional input limiting device configured as described above is as follows.

In other words, when the control lever 11 is operated while the target rotational speed signal N output from the throttle lever 7 is kept at a constant value, the control valve ₅ is controlled, and a hydraulic actuator (not shown) is driven by the pressure oil discharged from the hydraulic pump 3, thereby operating a working machine (not shown) to perform various tasks.

Further, the internal combustion engine 1 is controlled by the fuel injection pump 2 according to the control signal output from the fuel injection pump controller 10 in accordance with the rotation speed deviation signal ΔN output from the comparator 9. Ne is controlled so that it becomes the target rotation speed N.

By the way, if the load on a hydraulic actuator (not shown) increases, the input torque of the hydraulic pump 3 will exceed the output torque of the internal combustion engine 1, resulting in engine stall. In order to prevent this, the pressure of the pressure oil discharged from the hydraulic pump 3 is detected by the pressure detector 6, and a pressure signal P is output to the horsepower control function generator 12. The horsepower control function generator 12 is set with a functional relationship such that P·X _H =constant. This is because the product of the pressure signal P and the pump discharge capacity signal _XH is the input torque of the hydraulic pump 3, and this input torque is to be kept constant against sudden pressure changes. Further, in this horsepower control function generator ₁₂ , a plurality of P. It's starting to move in parallel. As a result, when an excessive output is requested from the internal combustion engine 1 by the hydraulic pump 3, the rotational speed deviation signal ΔN increases, and as a result, the value of the pump displacement signal _XH in the horsepower control function generator 12 increases. becomes smaller, and the input torque of the hydraulic pump 3 becomes smaller.

Note that the minimum value selection circuit 13 is connected to the operating lever 11.
The manipulated variable signal X _L output from the pump displacement signal X L and the pump discharge capacity signal X _L output from the horsepower control function generator 12
The minimum value of the values is selected to prevent waste of pressure oil discharged from the hydraulic pump 3 during fine operation and to limit input to the hydraulic pump 3.

By the way, in the conventional input limiting device configured as described above, it is convenient when the throttle lever 7 is maintained at a constant value. However, in particular, depending on the amount of operation of the operation lever 11, the internal combustion engine 1
If you want to change the output rotation speed of the motor, there are the following problems. That is, due to the moment of inertia of the internal combustion engine 1, the output rotation speed signal Ne lags with respect to the change in the target rotation speed signal N, and as a result, the rotation speed deviation signal ΔN becomes a large value, causing the output rotation speed to suddenly increase. Although controlled to increase internal combustion engine 1
Most of the output is used to increase the rotational speed of the internal combustion engine 1 itself. As a result, the horsepower control function generator 1
2, the input torque of the hydraulic pump 5 is significantly reduced, resulting in deterioration of operability.

The present invention has been made in view of the actual situation in the prior art, and its purpose is to increase the output of the internal combustion engine by the increased rotational speed of the internal combustion engine and the input of the hydraulic pump when the target rotational speed of the internal combustion engine is increased. An object of the present invention is to provide an input limiting device for a hydraulic pump driven by an internal combustion engine, which can distribute torque and obtain good operability.

In order to achieve this object, the present invention provides a means for determining the differential value of the output rotation speed of the internal combustion engine, a correction means for correcting the rotation speed deviation according to the differential value, and a hydraulic pump according to the differential value. The configuration is such that the minimum value of the input torque is limited.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An input limiting device for a hydraulic pump driven by an internal combustion engine according to the present invention will be described below with reference to the drawings. Second
The figure is a block diagram showing one embodiment of the present invention.
In FIG. 2, the same parts as those shown in FIG. 1 described above are designated by the same reference numerals.

In FIG. 2, 14 is a differentiator that calculates the differential value of the output rotation speed based on the output rotation speed signal N _e detected by the rotation speed detector 8, and 15 is the differentiator 1.
According to the differential signal N・_e output from 4, the signal ΔN _lnt
is a correction means, such as a function generator, that outputs .
This function generator 15 has N・e−
The functional relationship of ΔN _lnt is set. Also, 16 is
The minimum value of the operation amount signal X _L output from the operating lever 11 and the target rotation speed signal N output from the throttle lever 7 is selected to generate the target rotation speed signal.
Minimum value selection circuit that outputs N ₀ , 17 is comparator 9
Select the minimum value of the rotation speed deviation signal ΔN output from the rotation speed deviation signal ΔN and the value of the signal ΔN _lnt output from the function generator 15, and output the minimum value signal ΔN _nio to the horsepower control function generator 12. It is a circuit.

Note that ΔN _lnt installed in the function generator 15 is set as a function that satisfactorily distributes the internal combustion engine output by the internal combustion engine rotational speed increase and the hydraulic pump input torque in accordance with N· _e .

The operation of the embodiment configured as described above is as follows.

In other words, when the value of the operation amount signal _XL of the operation lever 11 is smaller than the value of the target rotation speed signal N of the throttle lever 7, the target rotation speed signal N ₀ output from the minimum value selection circuit 16 is the operation amount signal It is equivalent to X _L , and therefore, the output rotation speed of the internal combustion engine 1 is controlled according to this manipulated variable signal X _L. Also,
When the value of the manipulated variable signal _XL becomes larger than the value of the target rotational speed signal N, the target rotational speed signal _N0 output from the minimum value selection circuit 16 is equivalent to the target rotational speed signal N, and therefore The rotation speed of the internal combustion engine 1 is controlled according to this target rotation speed signal N.

In particular, among the above, when the value of the manipulated variable signal _XL is smaller than the value of the target rotational speed signal N and the manipulated variable signal _XL tends to increase, as described above, the influence of the moment of inertia of the internal combustion engine 1 Therefore, the rotation speed deviation signal ΔN output from the comparator 9
This will cause the value of to become too large.

Here, in general, the moment of inertia of the internal combustion engine 1 is
I _E , the output torque of the internal combustion engine 1 is T _E , the input torque of the variable displacement hydraulic pump 3 is T _P , and the rate of change (differential value) of the output rotation speed of the internal combustion engine 1 is N・e, then I _E N・
The relationship is _e = T _E - T _P. Further, as described above, since the input torque of the hydraulic pump 3 is expressed by T _P =P·X _H , I _E N· _e = T _E −P·X _H.

By the way, when the target rotation speed of the internal combustion engine 1 increases, the output signal ΔN from the comparator 9 increases, and this ΔN is directly transmitted to the horsepower control function generator 12.
, the pump discharge volume control signal _XH becomes a small value, and the input torque of the hydraulic pump 3 decreases excessively. Therefore, in the above equation, X _H
Focusing on the point that N・_e increases as becomes smaller,
By making ΔN _lnt input to the horsepower control function generator 12 smaller than ΔN according to the magnitude of N· _e , the increase in N· _e is limited, thereby X _H
Hydraulic pump 3
This prevents the input torque from decreasing significantly.

In the embodiment shown in FIG. 2, a differential value is determined by a differentiator 14 based on an output rotational speed signal Ne output from a rotational speed detector 8, and the differential signal N· _e is sent to a function generator. 15. The function generator 15 outputs a signal ΔN _lnt to the minimum value selection circuit 17 according to the functional relationship N· _e −ΔN _lnt . The rotation speed deviation signal ΔN is also output from the comparator 9 to the minimum value selection circuit 17, and the minimum value ΔN _nio of the signals ΔN _lnt and ΔN is output to the horsepower control function generator 12. This horsepower control function generator 12 generates a signal ΔN _nio
According _to the value _of It is output to the minimum selection circuit 13. Therefore, hydraulic pump 3
The discharge volume control mechanism 4 includes a minimum value selection circuit 13.
A discharge volume control signal X equivalent to the pump discharge volume signal _XH is output from the hydraulic pump 3.
is limited to a good input torque without reducing its input torque too much.

In addition, N・e− of the function generator 15 described above
By changing the functional relationship of ΔNlmt, the acceleration characteristics of the internal combustion engine 1 can be changed arbitrarily.
For example, if the value of ΔNlmt with respect to the differential value signal N·e is set to a large value, when ΔNlmt is selected by the minimum value selection circuit 17, the pump discharge selected by the horsepower control function generator 12 The capacity signal Xh becomes a small value, the input torque of the hydraulic pump 3 becomes small, and the corresponding output torque of the internal combustion engine 1 is used to increase the rotational speed of the internal combustion engine 1 itself, so that the acceleration characteristics of the internal combustion engine 1 are improved. . vice versa,
If the value of ΔNlmt with respect to the differential value signal N·e is set to a small value, the input torque of the hydraulic pump 3 can be maintained at a relatively large value, but the acceleration characteristics of the internal combustion engine 1 will deteriorate. In this way, by adjusting the functional relationship of N・e−ΔNlmt in the function generator 15,
The input torque of the hydraulic pump 3 and the acceleration characteristics of the internal combustion engine 1 can be set in a well-balanced manner.

As described above, the input limiting device for a hydraulic pump driven by an internal combustion engine of the present invention obtains the differential value of the output rotation speed of the internal combustion engine, and limits the minimum value of the input torque of the hydraulic pump according to this differential value. Because of this configuration, the input torque of the variable displacement hydraulic pump can be well controlled, resulting in improved operability compared to the conventional system.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an example of a conventional input limiting device for a hydraulic pump driven by an internal combustion engine, and FIG. 2 is a circuit diagram showing an example of the input limiting device for a hydraulic pump driven by an internal combustion engine according to the present invention. It is a circuit diagram. 1... Internal combustion engine, 2... Fuel injection pump, 3...
...Variable capacity hydraulic pump, 4...Discharge volume control mechanism, 5...Control valve, 6...Pressure detector, 7...Throttle lever, 8...Rotation speed detector, 9...Comparator, 10... ... Fuel injection pump controller, 11 ... Operation lever, 12 ... Horsepower control function generator, 13 ... Minimum value selection circuit, 14 ...
... Differentiator, 15 ... Function generator, 16 ... Minimum value selection circuit, 17 ... Minimum value selection circuit.

Claims (1)

[Scope of Claims] 1. Means for determining a rotation speed deviation, which is the difference between a target rotation speed and an output rotation speed of the internal combustion engine, such that as the rotation speed deviation increases, the input torque of the hydraulic pump decreases. In an input limiting device for a hydraulic pump driven by an internal combustion engine that controls the discharge capacity of the hydraulic pump, means for determining a differential value of the output rotational speed of the internal combustion engine, and correcting the rotational speed deviation according to the differential value. An input limiting device for a hydraulic pump driven by an internal combustion engine, comprising: a correction means, and limits a minimum value of input torque of the hydraulic pump according to the differential value. 2. An input limiting device for a hydraulic pump driven by an internal combustion engine according to claim 1, wherein a target rotational speed of the internal combustion engine is set in accordance with the amount of operation of a control lever that controls a hydraulic actuator.