JPS585112Y2 - Input horsepower control device for multiple variable displacement hydraulic pumps - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a control device for controlling the input horsepower of the pumps to a constant value when at least two variable displacement forming pressure pumps are driven by one prime mover.

In hydraulic power transmission devices for construction machinery, etc., in order to effectively utilize the output horsepower of the prime mover, an output limiter is installed on the variable displacement hydraulic pump, and regardless of the load, the pump input is limited within the range exceeding the load. In many cases, it is set so that it remains almost constant.

In this case, one or two variable displacement pumps are often used, but in recent years, a fixed displacement pump has been used as the third pump to increase the total input horsepower of each pump, that is, two or three pumps. A control device that maintains a constant load over a range exceeding the load has been developed, and the present applicant has already filed a patent application in 1983-1.
No. 4174 (see Japanese Unexamined Patent Publication No. 108002/1983).

However, in variable displacement pumps, there is a limit to the minimum input horsepower setting in terms of efficiency of the hydraulic pump and stability of control performance.

In other words, there is a limit to the maximum input horsepower of the third pump relative to the prime mover output.

Therefore, in the present invention, one of the plurality of pumps driven by a prime mover is a variable displacement pump with an output limiter,
Accordingly, the present invention provides an input control device for use with at least two variable displacement pumps that can be used over a wider range of loads and speeds.

Below, one embodiment of the present invention will be explained with reference to the drawings.
A, IB, and 16 are first to third variable displacement hydraulic pumps, and each pump is connected to a prime mover (not shown) through gears Z1 to Z4 and an input shaft 2, and is driven in conjunction with the pumps. It has become so.

In the actual case shown, three pumps are used, but two
It may be one or four or more.

Discharge lines 3 to 5 are provided between each pump 1A to 1C and each load (not shown), and the discharged oil from the loads of pumps IA and IB is returned to tank 8 via line 6.7. The discharged oil passes through line 9 to pump 1C.
It is set to be returned to .

An output limiter 10 is provided for the pumps 1A and 1h.

Any output limiter known per se can be used, and the figures are therefore illustrated in a simplified manner.

This output limiter 10 has screws 12 and 14, springs 15 and 16, follower pin 12a, etc.
2 is configured such that discharge pressure from pilot lines LA, LB, and LC branched from each of the discharge lines, that is, self-driving pressure and pressure from other pumps are applied.

The following pin 12a of the output limiter 10 is connected to the servo motor 20.
1 pump IA, I by a servo motor 20.
The tilting angle of B is changed, and the discharge amount of each pump changes in a substantially hyperbolic manner as the discharge pressure of each pump changes.

The configurations of the illustrated output limiter 10 and servo motor 20 may be those described in, for example, Japanese Unexamined Patent Publication No. 108002/1983, as described above.

Now, in the discharge pressure line 5 of the pump 1C, a piston 31,
An output limiter 30 including a spring 32 is provided, and this output limiter 30 is also configured to change the pump tilt angle substantially hyperbolically by the self-driving pressure of the pump 1C, thereby changing the discharge flow rate.

Furthermore, a pressure reducing valve 40 is provided in the pilot line LC,
The valve 40 maintains the downstream pressure PC constant when the upstream pressure is above a predetermined value, and maintains the downstream pressure PC to the same value as the upstream pressure when the upstream pressure is below a predetermined value. The structure is such that it is held in place.

Next, the operation of the present invention will be explained with reference to FIGS. 2 and 3.

FIG. 2 shows the relationship between the discharge pressure P3 and the discharge amount Q of the third pump 1C, and when the discharge pressure of the pump 1C is from zero to A, pressurized liquid is discharged at a constant flow rate QA.

When the discharge pressure becomes higher than this pressure A, the output limiter 30 is activated, so the flow rate decreases almost hyperbolically, during which a constant horse power control is performed, and this control is continued up to the pressure B.

Now, when the third pump 1C is operated with zero discharge pressure, it is sufficient to control the sum of the outputs of the first pump 1A and the second pump 1B to be constant.

That is, in FIG. 3, the first and second pumps IA,
IB is controlled with a constant horse power by curve S.

Next, when the discharge pressure of the third pump 1C increases, the increased pressure PC is applied to the output limiter 12 of the first and second pumps via the pilot line LC, so the output limiter 12 increases by that amount. Operate.

Therefore, the first and second pumps correspond to the curve S1 in FIG.
The pressure is controlled along a hyperbola that moves toward curve S2 as the pressure PC increases.

When the pressure of the third pump reaches pressure A, the eleventh and second pumps are controlled along the curve S2.

The pressure reducing valve 40 is configured to supply the pressure A to the pilot line LC even if a pressure higher than this pressure A is applied.

Therefore, the first and second pumps 1 and 1B are always controlled along the curve S3 when the third pump 1C is operated at pressure A or higher.

When the discharge pressure PC of the third pump 1C further increases, the output controller 30 of the third pump 1C is activated, and the discharge amount Q decreases according to FIG. 2, so that the third pump 1C is controlled at a constant power. .

At this time, since the first and second pumps IA and IB are also controlled to have a constant horsepower, the total horsepower of the three pumps is constant.

Therefore, according to the present invention, when at least one variable displacement pump is operated at less than a predetermined horsepower, the other one or more pumps are controlled to have a constant horsepower as shown in FIG. When one pump is operated at a discharge pressure higher than a certain level, the pump is controlled to a certain degree, so that each pump can be operated at a high pressure overall.

For example, in the above-mentioned known technology, the third pump could not be operated at pressure A or higher, but in the present invention it can be operated at pressure B, which is higher than pressure A.

As explained above, in the present invention, at least one of the at least two variable displacement hydraulic pumps (the third pump) has an output limiter that is controlled only by the self-driving pressure, and the remaining pumps Since the pump has a limiter controlled by the self-driving pressure and the pressure from the pilot line of the other pumps, and a pressure reducing valve is installed in the pilot line, the input horsepower to all pumps can be held constant, and All pumps can be of variable displacement type to enable a wide range of control.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the input horsepower control device for a plurality of variable displacement hydraulic pumps according to the present invention, and FIGS.
The figure is a diagram explaining the operation of the present invention. IA, IB, IC...variable displacement hydraulic pump,
10.30... Output limiter, 40...
Pressure reducing valve.

Claims (1)

[Scope of utility model registration request] In an input horsepower control device in which at least two variable displacement forming pressure pumps are driven in conjunction with one prime mover, at least one pump has an output limiter that is controlled only by self-driving pressure; The remaining pumps have output limiters controlled by the self-driving pressure and the pressure from the pilot line of said pump, said pilot line being provided with a pressure reducing valve, which pressure reducing valve is connected to a predetermined pressure on the upstream side. In the following cases, the pressure on the upstream side is applied to the downstream side, and when a pressure higher than a predetermined pressure is applied on the upstream side, the predetermined pressure is applied on the downstream side. Pressure pump input horsepower control device.