JPS5918558B2 - Control device combined with multiple variable displacement pumps driven by prime mover - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device combined with a plurality of variable displacement pumps driven by a prime mover.

Many hydraulically actuated devices, for example, excavators, are typically equipped with a plurality of variable displacement pumps to provide the pressurized fluid necessary to drive the multiple motors used in operating the excavation packet.

An example of a hydraulic circuit in such an excavator is disclosed in US Patent Application No. 207,027.

Various circuits are used in such systems,
The system may include entirely different or separate circuits associated with each motor, and various means for delivering fluid from multiple pumps to one or more hydraulic motors. All hydraulic pumps in a vehicle are typically driven by a single main motor, such as an internal combustion engine.

One problem with such a configuration is that separate individual motors and pumps can consume all of the horsepower output of the internal combustion engine.

Therefore, when loads are applied to more than one motor or pump, the internal combustion engine may stall.

According to many attempts made to solve these problems, means have been devised for adjusting the output of said pump according to the total horsepower output of the engine and the load applied to its own equipment. There is.

Additionally, U.S. Patent Application No. 68,317 discloses a system that solves the above-mentioned problems, but this system uses what is known as an underspeed bulge to reduce the output of the pump. In order to adjust
It operates according to the speed of the internal combustion engine driving the pump.

The conventional method for operating such a system is to cause the load applied to the engine to reduce its speed; The pump output can be adjusted and automatically reduced in a way that compensates for the loss in engine speed so as to obtain a corresponding pump output.

- The problem with such systems is that the engine inertia delays the reduction in engine speed and does not respond quickly when the underspeed valve is placed at maximum pressure.

By way of example, this occurs in an excavator equipped with a circuit as described above, where fluid from both pumps is used to lift one boom.

In this condition, the flow rate to the boom cylinder increases;
Depending on the capacity of the two variable displacement pumps, a sudden increase in pressure will occur, which exceeds the available power output from the engine.

If the boom and its load supported by the boom are rapidly increasing due to pressure peaks created in its circuit, the boom will tend to overrun the pump and the pressure in its system will begin to decrease.

At the same time, the engine speed begins to decrease, which creates a pressure differential across the underspeed orifice.
The underspeed valve responds by delaying the reduction in pump capacity.

This reduction in pump capacity facilitates the reduction in pressure by allowing the boom speed to decrease.

The inevitable process of change in system and pump capacity is based on underspeed control.
Due to the pressure conditions within this system, with a 90° phase difference, a rhythmic pulsation occurs during boom extension, which is then damped out.

Since the engine speed increases as the pump capacity and the pressure in the system decreases, the pump capacity becomes increased again, creating a new pulsation in the boom.

The 90° phase difference due to the underspeed output control facilitates the machine's natural course to continue the erratic boom motion.

Another solution for resolving the aforementioned power overload condition is disclosed in US Patent Application No. 127,738 "Summing Valve".

The summing valve device provides a means for adjusting a control valve responsive to the summation pressure created by the loading of a variable displacement pump, the control valve adapted to control the displacement of the pump. ing.

However, this type of pump has the disadvantage that although it responds to some extent to the load pressure of the pump, it does not respond to the load of the engine.

Also, although such systems are relatively sensitive to pump loads, they are less sensitive to actual engine loads.

The main object of the present invention is to provide an output control means capable of solving the above-mentioned problems in the prior art.

Another object of the present invention is to provide an output control means for a hydraulic control system equipped with a plurality of variable displacement pumps that can respond to both the output of the pump and the output of the main motor driving the same, thereby providing an optimal The aim is to make it possible to adjust the capacity and output of the pump appropriately so that it can correspond to the desired output.

The present invention is a control device that is combined with a prime mover and a plurality of variable displacement pumps that supply pressure fluid for operating a plurality of hydraulic motors that are driven by the prime mover and that power the device, the control device being combined with a a pressure-responsive servo control means operative to adjust displacement; a fixed displacement pump driven by the prime mover and providing a source of pilot control fluid; a fixed displacement pump connected to the servo control means and responsive to the output of the fixed displacement pump; an underspeed valve for directing a control fluid signal to said servo control means to adjust the output of said variable displacement pump as a function of the speed of said prime mover; In response to the sum of the pressures of the power fluid from the displacement pumps, a control fluid signal is directed to the servo control means (a pressure responsive summing valve is provided between the servo control means, the underspeed valve and the summing valve; A control device is provided which includes a speed valve and a shuttle valve responsive to a control fluid signal from the summing valve and directing the larger control fluid signal to the servo control means.

Embodiments of the present invention will be described below with reference to the drawings.

Referring to FIG. 1, a pair of variable displacement pumps 10.11
It is shown.

In addition, a fixed displacement pump 12 is provided, a variable displacement pump 10.11 and a constant displacement pump 12 are connected to the internal combustion engine 1.
3, which sucks liquid from the tank 14 and supplies hydraulic pressure to the hydraulic motor via conduits 15, 16, 17.

Each variable displacement pump 10.11 has pressure responsive servo control means 18, 19 which serve to adjust its displacement.

The control device has a fixed displacement pump 20 providing a source of pilot control fluid, the fixed displacement pump 20 having the same prime mover as the variable displacement pump 10.11, namely the internal combustion engine 13.
Driven by.

Additionally, an underspeed valve 21 is connected to the servo control means 18.19 of the variable displacement pump 10.11, the underspeed valve 21 being responsive to the output of the fixed displacement pump 20 and servo controlling the control fluid signal of the fixed displacement pump 20. It acts as a guide to means 18 and 19.

In this embodiment, an underspeed valve 21 having an orifice 22 and a pressure differential responsive valve member 23 is used, with the output of the fixed displacement pump 20 being directed to both ends of the valve member 23 by conduits 24,25.

Orifice 22 creates a pressure differential between conduits 24,25.

Furthermore, the spring force of the tension spring against the valve member 23 is the first.
Acting to the left in the figure, the valve member 23
．． It operates in response to a pressure difference between 25 and 25 mm.

The fixed displacement pump 20 is connected via conduit 26, valve member 23 and conduit 2T to the shuttle valve 28 and to the servo control means 18.19 of the variable displacement pumps 10,11.

Additionally, fixed displacement pump 20 connects conduit 31 and IJ I
Pressure responsive summing valve 32 via J-F valve 40
It is connected to the.

The shuttle valve 28 is the servo control means 18, 19 of the variable displacement pump 10.11, and the underspeed valve 21.
and a summing valve 32, and the summing valve 32 is connected to the servo control means 18, 19 via the shuttle valve 28.

In this embodiment, the spring force of the compression spring acts upwardly in FIG. 2 on the spool 33 of the summing valve 32, and the variable displacement pump io,
i1 and the power fluid of the fixed displacement pump 12 are connected to the piston 3
7, 38, 39, the spool 33 is connected to the pump 10
, 11.12.

This control device is capable of regulating the output of the variable displacement pump 10.11 as a function of the speed of the engine 13 until the variable displacement pump 10.11 is temporarily overloaded.

As the speed of engine 13 increases, fixed displacement pump 20
The speed of will also increase and its power will increase.

Therefore, the conduit 24 of the underspeed valve 21,
The differential pressure between 25 and 25 increases, actuating valve member 23 and closing between conduits 26 and 27.

Therefore, the output of the fixed displacement pump 20, ie the control fluid signal, is not led to the servo control means 18, 19 of the variable displacement pump 10.11.

Conversely, as the speed of engine 13 decreases, the speed of fixed displacement pump 20 also decreases, reducing its output.

Therefore, the pressure differential between conduits 24, 25 decreases, valve member 23 operates, and conduits 26, 27 are opened.

The control fluid signal of the fixed displacement pump 20 is thus routed through the shuttle valve 28 to the servo control means 18.19 of the variable displacement pump 10.11.

As a result, the output of the variable displacement pumps 10, 11 is controlled as a function of the speed of the engine 13.

Further, this control device is configured to immediately switch off the variable displacement pump 10 in response to the sum of the power fluid pressures from the pumps 10, 11, 12 when a temporary overload occurs on the variable displacement pump 10, 11, 12. 11 outputs can be adjusted.

When a temporary overload occurs on the variable displacement pump 10.11 and the fixed displacement pump 12, the spool 33 of the spool valve 32 operates in response to the sum of the power fluid pressures from the variable displacement pump 10.11, causing the conduit 31 and shirttle valve 2
8 rooms will be opened.

Thus, the output of fixed displacement pump 20, ie, the control fluid signal, is directed through summing valve 32 to shuttle valve 28.

The control fluid signal from summing valve 32 is greater than the control fluid signal from underspeed valve 21.

The shuttle valve 28 operates in response to a control fluid signal from the summing valve 32 and directs the control fluid signal from the summing valve 32 to the servo control means 18.19 of the variable displacement pump 10.11.

The control fluid signal from underspeed valve 21 is blocked by shuttle valve 28 and ignored.

Therefore, the variable displacement pump 10.11 immediately responds to the sum of the pressures of the power fluid from the variable displacement pumps io, 'ii.
output is adjusted.

When the sum of the power fluid pressures from the variable displacement pump 10.11 decreases, the spool 33 of the summing valve 32 operates, closing between the conduit 31 and the shuttlecock valve 28, and the control fluid signal is directed to the shuttlecock valve 28. I can't get run over.

Shuttle valve 28 operates in response to the control fluid signal from underspeed valve 21 and connects the control fluid signal from underspeed valve 21 to variable displacement pump 10 .
11 servo control means 18.19.

As described above, the present invention provides an underspeed valve 21 that responds to the output of the fixed displacement pump 20 until a temporary overload is applied to the pair of variable displacement pumps 10 and 11.
can lead the control fluid signal to the servo control means 18,19.

The output of the variable displacement pump 10.11 can thus be adjusted as a function of the speed of the prime mover driving the variable displacement pumps 10, 11 and the fixed displacement pump 20.

Additionally, a control fluid signal is directed to the servo control means 18.19 by means of a summing valve 32 which is responsive to the sum of the pressures of the power fluid from the variable displacement pump 10.11 when a temporary overload occurs on the variable displacement pump 10.11. It can be drawn.

Therefore, the output of the variable displacement pump 10.11 can be immediately adjusted according to the sum of the pressures of the motive fluid from the variable displacement pump 10.11.

[Brief explanation of drawings]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of the present invention, and FIG. 2 is an explanatory diagram showing the principle of the summing valve of FIG. 1. 10.11...Variable displacement pump, 13...
... Engine, 18.19 ... Servo control means, 20 ... Fixed capacity pump, 21 ...
Underspeed valve, 28...Shuttle valve, 32...-+j-ming valve.

Claims (1)

[Scope of Claims] 1. A control device combined with a prime mover and a plurality of variable displacement pumps that supply pressure fluid for operating a plurality of hydraulic motors driven by the prime mover and powering the device, the control device comprising: a pressure-responsive servo control means operative to adjust the displacement of said pump; a fixed displacement pump driven by said prime mover and providing a source of pilot control fluid; an underspeed valve responsive to directing a control fluid signal to said servo control means to adjust the output of said variable displacement pump as a function of the speed of said prime mover; In response to the sum of power fluid pressures from a plurality of variable displacement pumps, a control fluid signal is transmitted to the servo control means (provided between a pressure responsive summing valve, the servo control means, the underspeed valve, and the summing valve). and a shuttle valve responsive to control fluid signals from the underspeed valve and the summing valve and directing the larger control fluid signal to the servo control means.