JPH04362286A - Controller for variable capacity pump - Google Patents

Abstract

PURPOSE:To utilize the output torque to the max. over the whole pressure range by comparing the output torque of an engine with the absorption torque for a variable capacity pump, setting the absorption torque as to be max. within the range of the output torque, and outputting an instruction signal. CONSTITUTION:A controller 2 is installed, for example, on a construction machine, and when an engine 4 revolves, a variable capacity pump 6 is driven. A controller 8 always compares the output torque of the engine 4 and the absorption toque of the variable capacity pump 6, and when the latter is going to exceed the former, the controller 8 outputs an instruction signal to an solenoid proportional reducing valve 16. Accordingly, the solenoid proportional reducing valve 16 switches a control valve 12, and both the oil passages 24 and 26 are connected, and the pressurized oil in other chambers of a control cylinder 10 is discharged into an oil tank 28. Accordingly, the swash plate 20 of the variable capacity pump 6 is driven, and the discharge flow rate (absorption torque) is reduced. While, if the absorption torque is reduced both the oil passages 24 and 26 are connected, and the discharged flow rate (absorption torque) is increased.

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 pump applied to a hydraulic system of construction machinery and the like.

0002

2. Description of the Related Art Generally, a variable displacement pump is used as a hydraulic power source for hydraulic control of construction machinery and the like. As the variable displacement pump, for example, a swash plate type variable displacement pump is used, and is connected to an engine (prime mover) so as to be driven by the pump. Control methods for such variable displacement pumps include (1) a constant torque control method using its own discharge pressure, and (2) a control method for absorbing torque using a pilot pressure commanded by a control device that monitors the engine speed. A variable absorption torque control method that changes the maximum value is known.

In the constant torque control system, a spring is used to control the absorption torque of a variable displacement pump, and the discharge pressure is adjusted on the maximum value line (actually on a straight line as shown by the solid line in FIG. 4). The discharge flow rate is controlled to decrease in proportion to. And its maximum value is constant. In addition,
In FIG. 4, Q indicates the discharge flow rate of the variable displacement pump, P indicates its discharge pressure, and the dotted line indicates the maximum value of absorption torque of the variable displacement pump (output torque of the engine).

In the variable absorption torque control system, the engine speed is constantly monitored, and when the absorption torque of the variable displacement pump becomes larger than the absorption torque of the engine and the engine speed decreases, the pilot pressure is changed. and the absorption torque in the above torque-constant control method (
(maximum value) to prevent the engine speed from decreasing (see FIG. 5). In addition, in FIG. 5, Q
is the discharge flow rate of the variable displacement pump, P is the discharge pressure thereof, and the dotted line shows two examples of the maximum value of the absorption torque of the variable displacement pump after the change.

[0005]

However, the conventional variable displacement pump control system has the following problems to be solved. (1) In any of the above control systems, since the absorption torque of the variable displacement pump is set by a spring, the P-Q curve, which should originally be a hyperbola, becomes a straight line. Therefore, depending on the pressure range, the output torque of the engine cannot be used effectively. (2) In the above variable absorption torque control method, the absorption torque of the variable displacement pump is not directly measured, but it is detected that the absorption torque of the variable displacement pump exceeds the engine output due to a decrease in engine speed. Detected. Since the response to changes in the engine speed is slow, the controllability of changing the set value of the variable displacement pump absorption torque is poor, and the output torque of the engine cannot be used effectively. (3) Furthermore, when multiple variable displacement pumps are driven by a single engine, the absorption torque of each variable displacement pump cannot be accurately determined, so the absorption torque of the multiple variable displacement pumps as a whole must be reduced. Therefore, the output torque of the engine cannot be used effectively.

The main object of the present invention is to provide an improved variable displacement pump which allows the absorption torque of a variable displacement pump to be set over the entire pressure range so as to make full use of the output torque of the engine without exceeding it. The present invention provides a control device for a volumetric pump.

Other objects of the present invention will become clear from the following description, in which an embodiment of a control device for a variable displacement pump constructed in accordance with the present invention is explained in detail with reference to the accompanying drawings.

[0008]

Means for Solving the Problems In order to achieve the above main object, the present invention provides an engine, a variable displacement pump connected to the engine so as to be driven by the engine, and a discharge pump of the variable displacement pump. The variable displacement pump includes a control device that controls the flow rate and a control device that outputs a command signal to the control device, and the variable displacement pump is provided with an input torque measurement device, and the control device includes at least the input torque measurement device. The variable displacement pump is configured to receive an input torque signal measured by the engine and a rotational speed signal of the engine, and the output torque of the engine determined from the rotational speed of the engine and the input torque signal. The absorption torque of the variable displacement pump is compared with the absorption torque of the variable displacement pump, and the absorption torque of the variable displacement pump is set to be the maximum within the range of the output torque of the engine, and is output as the command signal. A controller for a variable displacement pump is provided.

In order to achieve the above main object, the present invention further provides an engine, a plurality of variable displacement pumps connected to the engine so as to be driven by the engine, and a plurality of variable displacement pumps connected to the engine so as to be driven by the engine. control devices provided in association with each other so as to control the discharge flow rates independently of each other;
A control device that outputs a command signal to each of the control devices, each of the variable displacement pumps is provided with an input torque measuring device, and the control device is configured to at least perform measurement by each of the input torque measuring devices. The variable displacement pump is configured to receive an input torque signal and a rotational speed signal of the engine, and output torque of the engine determined from the rotational speed of the engine and the input torque signal, respectively. The sum of the absorption torques of each of the variable displacement pumps is set to be the maximum within the range of the output torque of the engine, and the command signal is A control device for a variable displacement pump is provided, the control device being configured to output an output.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS A control device for a variable displacement pump improved according to the present invention will be described in detail below based on embodiments with reference to the accompanying drawings.

[0011] In FIG. 1, a control device for a variable displacement pump, generally designated by the number 2, is mounted on, for example, a construction machine. The variable displacement pump control device 2 includes an engine 4, a variable displacement pump 6 connected to the engine so as to be driven by the engine 4, a control device for controlling the discharge flow rate of the variable displacement pump 6, and a command signal to the control device. and a control device 8 that outputs. In this example, the control device includes a control cylinder 10 that directly controls the discharge flow rate of the variable displacement pump 6, a control valve 12 that controls the control cylinder 10, and a flow rate of pressure oil from a pilot pump 14 that is a pilot oil pressure source. and an electromagnetic proportional pressure reducing valve 16 that controls the control valve 12 by changing the pressure. A command signal from the control device 8 is sent to the electromagnetic proportional pressure reducing valve 14.

The engine 4 is, for example, a diesel engine equipped with a governor, and the variable displacement pump 6 is, for example, a swash plate variable displacement pump as shown in FIG. 3, which is well known to those skilled in the art. Pressure oil discharged from the variable displacement pump 6 is guided to each hydraulic element (not shown) through a discharge oil passage 18. The control cylinder 10 has a piston housed therein, and one end of the piston rod is connected to the swash plate 20 of the variable displacement pump 6. control cylinder 1
0, one oil chamber separated by the piston is connected to the discharge oil passage 18 via the oil passage 22, and the other oil chamber is
It is connected to the oil passage 22 via the oil passage 24 and the control valve 12.

The control valve 12 is a three-port, two-position switching valve, and in the normal position shown in the figure, the pressure oil discharged from the variable displacement pump 6 is guided to the other oil chamber of the control cylinder 10, and the swash plate 2
0 is moved to maximize the discharge flow rate of the variable displacement pump 6, that is, the absorption torque. When it is switched to another position, the oil passage 24 and the oil passage 26 are connected, and the pressure oil in the other oil chamber of the control cylinder 10 is discharged to the oil tank 28. As a result, the discharge flow rate of the variable displacement pump 6 is reduced. One pilot port of the control valve 12 is connected to the electromagnetic proportional pressure reducing valve 16 via an oil passage 30.
The electromagnetic proportional pressure reducing valve 16 is connected to the pilot pump 14 via an oil passage 32.

The variable displacement pump 6 is provided with an input torque measuring device 34. An example is shown in FIG. 3, where numeral 36 indicates the input shaft of the variable displacement pump 6,
One end is connected to the engine 4. A torque detection section 38 is provided on the input shaft 36, and a strain gauge (not shown) is attached thereto. In connection with the strain gauge, the case 40 of the variable displacement pump 6 is provided with an input coil 42 and an output coil 44. The strain gauge has an input coil 42.
A current is supplied from the output coil 44, and the detected input torque (absorbed torque) is detected. It goes without saying that the input torque detection device is not limited to this example, and may use other methods well known to those skilled in the art.

Referring again to FIG. 1, control device 8
is configured to receive at least an input torque signal measured by an input torque measuring device 34 and a rotation speed signal detected by a rotation speed detection device 46 provided in the engine 4 and well known to those skilled in the art. ing. The control device 8 constantly compares the output torque of the engine 4 determined from the rotation speed of the engine 4 and the absorption torque of the variable displacement pump 6 based on the input torque signal, and determines that the absorption torque of the variable displacement pump 6 is equal to the output torque of the engine 4. The configuration is such that the maximum value is set within the range of , and output as a command signal. The command signal output by the control device 8 is sent to the electromagnetic proportional pressure reducing valve 16 to control the electromagnetic proportional pressure reducing valve 16 . The electromagnetic proportional pressure reducing valve 16 is configured to control the oil pressure supplied from the pilot pump 14 to the control valve 12 in accordance with a command signal. Note that the control device 8 has the following information in advance:
Data on the rotational speed and output torque of the engine 4 are stored. Further, in this example, the control device 8 is configured to receive an external signal from an external device 48, and in a range below a permissible value of the output torque of the engine 4, the control device 8 is configured to receive a signal from the outside to control the variable displacement pump 6. It is also possible to control the input torque of

Next, the operation of the variable displacement pump control device 2 constructed as described above will be explained. engine 4
When the variable displacement pump 6 rotates, the variable displacement pump 6 is driven. The output torque of the engine 4 determined from the rotational speed of the engine 4 and the absorption torque of the variable displacement pump 6 based on the input torque signal are input to the control device 8 and are constantly compared. When the absorption torque of the variable displacement pump 6 attempts to exceed the output torque of the engine 4, a command signal is output from the control device 8 and sent to the electromagnetic proportional pressure reducing valve 16. The electromagnetic proportional pressure reducing valve 16 receives this command signal, changes (reduces) the pilot pressure, and switches the control valve 12 from the illustrated position to another position. When the control valve 12 is switched, the oil passage 24 and the oil passage 26 are connected, and the control cylinder 1
Pressure oil in the other oil chamber of No. 0 is discharged to the oil tank 28. The swash plate 20 of the variable displacement pump 6 is moved to increase the discharge flow rate (
absorption torque) is reduced.

When the absorption torque of the variable displacement pump 6 decreases and there is a margin for the output torque of the engine 4, a command signal is output from the control device 8 and sent to the electromagnetic proportional pressure reducing valve 16. The electromagnetic proportional pressure reducing valve 16 receives this command signal, changes (increases) the pilot pressure, switches the control valve 12, and returns it to the position shown in the figure. When the control valve 12 is switched, the oil passage 24 and the oil passage 22 are connected, and the pressure oil discharged from the variable displacement pump 6 is guided to the pressure oil in the other oil chamber of the control cylinder 10. Swash plate 2 of variable displacement pump 6
0 is moved and the discharge flow rate (absorption torque) is increased. Since the above control is always performed while the engine 4 is rotating, the swash plate 20 of the variable displacement pump 6
It is always set at a position where the output torque of the engine 4 can be utilized to the maximum.

FIG. 2 shows an example of a control device 2 for a variable displacement pump to which the present invention is applied to a so-called double pump. This variable displacement pump control device 2 includes an engine 4 and two variable displacement pumps 6 connected to the engine 4.
, a control device provided in association with each variable displacement pump 6 so as to control the discharge flow rate of each variable displacement pump 6 independently of each other, and a control device 8 that outputs a command signal to each of the control devices. . In addition, in FIG. 2, the number 50 is a transmission device that divides and transmits the output of the engine 4 to two variable displacement pumps 6. Each variable displacement pump 6 is individually provided with an input torque measuring device 34, and is configured so that independent input torque signals are input to the control device 8. Each of the control devices includes a control cylinder 10, a control valve 12, and an electromagnetic proportional pressure reducing valve 16, respectively. Since their basic configuration and operation are substantially the same as those shown in FIG. 1, the same parts are denoted by the same reference numerals, and individual explanations will be omitted.

In the case of this variable displacement pump control device 2,
The control device 8 compares the output torque of the engine 4 determined from the rotational speed of the engine 4 with the sum of the absorption torques of each of the variable displacement pumps 6 based on each input torque signal measured by each input torque measuring device 34. , the sum of the absorption torques of the variable displacement pumps 6 is set to be maximum within the range of the output torque of the engine 4, and is configured to be output as a command signal. Since each electromagnetic proportional pressure reducing valve 16 is individually controlled by this command signal,
The absorption torque of each variable displacement pump 6 can be individually set to an appropriate value within a range that does not exceed the output torque range of the engine 4.

Although this invention has been described in detail above based on examples, this invention is not limited to the above-mentioned examples, and can be modified or modified in various ways within the scope of this invention. be.

[0021]

[Effects of the Invention] According to the present invention described above based on one implementation, the following effects can be obtained. (1) The control device can always control the absorption torque of the variable displacement pump to the maximum value that does not exceed the engine output range, making the most effective use of the engine output torque over the entire pressure range. can. (2) Since it is configured to directly measure the absorption torque of the variable displacement pump, the responsiveness of changing the absorption torque setting value of the variable displacement pump is quick, and the variable displacement pump output is always close to the engine output torque. You can expect high torque,
The engine's output torque can be used as effectively as possible. (3) When multiple variable displacement pumps are driven by one engine, the absorption torque of each variable displacement pump can be accurately determined, so the sum of the absorption torque of each variable displacement pump is
It becomes possible to individually control the absorption torque of each variable displacement pump to a desired value within a range that does not exceed the output of the engine, and the above merits are further improved.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of a control device for a variable displacement pump improved according to the present invention.

FIG. 2 is a schematic diagram showing another embodiment of a control device for a variable displacement pump improved according to the present invention.

FIG. 3 is a schematic cross-sectional view of a swash plate variable displacement pump including an embodiment of an input torque measuring device.

FIG. 4 is a P-Q diagram for explaining constant torque control.

FIG. 5 is a PQ diagram for explaining absorption torque variable control.

[Explanation of symbols]

2 Control device for variable displacement pump 4 Engine (prime mover) 6 Variable displacement pump 8 Control device 10 Control cylinder 12 Control valve 14 Pilot pump 16 Solenoid proportional pressure reducing valve 20 Swash plate 34 Input torque measuring device 46 Rotation speed detection device 48 External device

Claims (2)

[Claims] 1. An engine, a variable displacement pump connected to the engine to be driven by the engine, a control device for controlling a discharge flow rate of the variable displacement pump, and a control for outputting a command signal to the control device. The variable displacement pump is provided with an input torque measuring device, and the control device receives at least an input torque signal measured by the input torque measuring device and a rotation speed signal of the engine. The output torque of the engine determined from the rotational speed of the engine is compared with the absorption torque of the variable displacement pump based on the input torque signal, and the absorption torque of the variable displacement pump is determined from the engine rotation speed. A control device for a variable displacement pump, characterized in that the output torque is set to be maximum within the range of the output torque, and is output as the command signal. 2. An engine, a plurality of variable displacement pumps coupled to the engine to be driven by the engine, and a plurality of variable displacement pumps each associated with each other so as to control the discharge flow rate of each of the variable displacement pumps independently of each other. and a control device that outputs a command signal to each of the control devices, each of the variable displacement pumps is provided with an input torque measuring device, and the control device includes at least the following: The input torque signal measured by each of the input torque measurement devices and the rotation speed signal of the engine are configured to be input, and the output torque of the engine determined from the rotation speed of the engine and the input Compare the sum of absorption torques of each of the variable displacement pumps due to each of the torque signals, and the sum of the absorption torques of each of the variable displacement pumps is maximized within the range of the output torque of the engine. What is claimed is: 1. A control device for a variable displacement pump, characterized in that it is configured to set such settings and output them as the command signal.