JPH0237188A - Controller for variable displacement pump - Google Patents

Abstract

PURPOSE:To perform control over a variation in pump displacement optimally by making a feedback gain variable according to either of load pressure in a pump and a position of an operating level and its speed. CONSTITUTION:When pump displacement is changed, a feedback gain to a controller 3, making discharge of a pump 2 variable according to the position and operating speed of an operating level 7, is made to be variable, not constant. Even if load pressure being imposed on the pump 2 is suddenly varied, the feedback gain is made smaller in advance, so that a pump swash plate 6 is no longer subjected to hunting and thus the pump displacement becomes stabilized. When the operating level 7 is quickly operated from a neutral position, each responsiveness in a servo 5 and the pump swash plate 6 is good because the feedback gain is made larger in advance, thus any delay of a variation in the pump displacement is brought to naught.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a control device for a variable displacement pump, and particularly to a device for suitably controlling changes in the discharge amount of a variable displacement pump used in construction machinery, etc. Regarding.

[Conventional power technology] Conventionally, as shown in FIG. 9, in a hydraulic circuit used for construction machinery, etc., the discharge amount of a variable displacement pump is determined by: (1) detecting the load pressure 33 applied to the pump 32 in accordance with the output of the engine 31; The proportional electromagnetic control valve 34 then drives the servo 35 of the pump 32 to make the pump discharge amount variable as shown in FIG. 10(a).

(2) The flow rate flowing from the pump 32 to the tank 39 is detected by the sensor 40 according to the displacement of the operating lever 38 of the switching valve 37 for operating the actuator 36, is converted by the pressure proportional valve 41, and is converted by the servo 35 of the pump 32. is driven to change the pump discharge amount as shown in FIG. 11(b).

These things are being done together.

[Problems to be Solved by the Invention] However, according to the conventional variable displacement pump control device described above, when the pump displacement changes depending on the load pressure applied to the pump, if the servo responsiveness is too good, the pump The pump swash plate, which determines the capacity, is hunting and the pump capacity is unstable.

(2) When changing the pump capacity according to the position of the control lever, if the control lever is operated rapidly, the responsiveness of the servo and pump swash plate cannot follow, resulting in a delay in pump capacity and a time lag.

This contradictory situation arises, and there is a drawback that it is difficult to appropriately select control of the change in pump displacement of the variable displacement pump.

The present invention focuses on the above-mentioned conventional problems, and the position of the operating lever is 1. The object of the present invention is to provide a control device for a variable displacement pump that can suitably control changes in pump displacement according to operating speed.

[Means for Solving the Problems] In order to achieve the above object, a control device for a variable displacement pump according to the present invention is a control device for a variable displacement pump in which the pump discharge amount is controlled by the load pressure applied to the pump. The configuration is such that the feedback gain to the control device that changes the discharge amount of the pump is not constant but variable depending on either the load pressure of the pump or the position and operating speed of the operating lever.

[Function] According to the above configuration, when changing the pump capacity, the feedback gain to the control device that changes the pump discharge amount depending on the position and operation speed of the operating lever is not constant but variable, so that the pump capacity does not change. is now suitable, and even if the load pressure applied to the pump changes suddenly, the feedback gain is small, so the servo response is not too good, and the pump swash plate, which determines the pump capacity, does not hunt, and the pump capacity is stabilized. do. Furthermore, when the control lever is operated rapidly from the neutral position of the control lever, the feedback gain is increased, so the response of the servo and the pump swash plate is good, and there is no delay in the change in pump capacity, eliminating time lag. Furthermore, when the control lever is operated slowly from the neutral position, the feedback gain is changed according to the speed of the control lever, so the response of the servo and pump swash plate is also variable according to the speed. Sexuality improves.

[Embodiment] An embodiment of a control device for a variable displacement pump according to the present invention will be described in detail below with reference to one drawing. 1st
1 is an overall configuration diagram of one embodiment of the present invention, FIG. 2 is a flowchart of the first embodiment, and FIG. 3 is a block diagram. In FIG. 1, a variable displacement pump 2 (hereinafter referred to as pump) driven by a power source 1 such as an engine is operated by a control device 50 consisting of a proportional electromagnetic control valve 4 and a servo 5 based on a command from a controller 3. The position of the pump swash plate 6 (hereinafter referred to as swash plate) is determined, and a determined pump capacity is discharged. The controller 3 has an operating lever 7 (
below.

A lever position signal and a speed signal from a lever (referred to as a lever) are input, and the load pressure applied to the pump is detected by a pressure sensor 8 and input as a load signal, and the position and speed of the pump swash plate are determined. There is. Further, the position of the pump swash plate is measured by a displacement meter 9 and fed back to the controller 3 and compared with a command value to improve accuracy, and the rotation of the pump 2 is detected by a tachometer 10 and fed back to the controller 3.

The operation of the above configuration will now be described with reference to FIGS. 2 to 5. In step 51, it is determined whether the displacement (dimension=L) of the swash plate 6 is less than or equal to a certain value (La), and in the following cases (
For example, if the load on the pump in FIG. 10 is below point P), go to step 52. In step 52, it is determined whether the operation speed (V) of the lever 7 is below a certain value (V a ), or above a certain value (V a ), In the following cases, go to step 53, and in order to move the swash plate 6, the value of the feedback gain in FIG.
As shown in the figure, the controller 3 calculates the command value to be gradually increased according to the operating speed, and outputs the command value to the servo 5. If the value is 0 or more, the process goes to step 54, and the value of the feedback gain is shown in Figure 4 (point R). As shown above), the controller 3 calculates the command value so that it remains constant even if the operating speed increases, and outputs a command value to the servo 5. In addition, in step 51, the displacement (dimension = L) of the swash plate 6 is set to a certain value (La ) or more, go to step 55. In step 55, the operating speed of lever 7 (V
) is below or above a certain value (vb), and if it is 2 or more, go to step 568, and in order to move the swash plate 6, the value of the feedback gain in Fig. 4 is determined as in Fig. 5 (8 points or more). The controller 3 calculates the speed so that the speed gradually decreases depending on the operating speed. In the following cases, go to step 57, and the controller 3 calculates so that the value of the feedback gain remains constant even if the operation speed increases, as shown in Figure 5 (8 points or less), and outputs a command value to the servo 5. .

Next, the operation of the second embodiment, which has the same configuration as the first embodiment, will be explained with reference to FIGS. 6 to 8.

In the second embodiment, the load pressure applied to the pump approximately corresponding to the position of the swash plate and lever of the pump is detected, and in step 61, whether the load pressure (P) of the pump 2 is less than a certain value (Pa) or greater than or equal to a certain value (Pa) is detected. In the following cases, go to step 62. In step 62, it is determined whether the operation position M (M) of the lever 7 is less than or greater than a certain value (M a ), and in the following cases, go to step 63, In order to move the swash plate 6, the controller 3 calculates the value of the feedback gain shown in Fig. 3 so that it gradually becomes faster according to the operating position, as shown in Fig. 7.
If it is 0 or more, send the command value to servo 5, step 64
The controller 3 calculates the value of the feedback gain so that it remains constant even if the operating position increases as shown in Figure 7 (8 points or more), and outputs the command value to the servo 5.In step 61, the load pressure is If (P) is greater than a certain value (Pa), go to step 65. In step 65, lever 7
It is determined whether the operating position (M) is less than or equal to a certain value (Mb), or greater than or equal to 1. If it is greater than or equal to 1, the process goes to step 66, and in order to move the swash plate 6, the value of the feedback gain in FIG. 3 is determined as shown in FIG. (T point or above), the controllers 1 to 3 are used to calculate the speed gradually becoming slower depending on the operating position. In the following cases, the process goes to step 67, and the value of the feedback gain is shown in Fig. 8 (
The controller 3 calculates and outputs a command value to the servo 5 so that it remains constant even if the operating position increases (below point T).

In the above example, the swash plate and lever speed, and the pump load pressure and lever position are described, but this is not taken as an example, and the pump load pressure and lever speed, the swash plate and lever position, the pump load pressure or the swash plate are described. , lever speed, and lever position may be combined.Also, although the feedback gain is shown as a straight line connected at a certain point, it goes without saying that a curved line may also be used.

[Effects of the Invention] As explained above, according to the present invention, the feedback gain to a control device such as a servo that controls a swash plate that determines the discharge amount of a variable displacement pump is controlled depending on the position of the operating lever, operating speed, etc. Since it is variable rather than constant, changes in pump capacity can be suitably controlled. Therefore, when changing the pump capacity according to the load pressure applied to the pump, the feedback gain will be small even if the pump is sufficiently loaded with load pressure (for example, the PQ curve in Figure 10) and the control lever is operated quickly. This prevents the servo from being too responsive, and the pump swash plate, which determines the pump capacity, does not hunt, making the pump capacity stable. In addition, when changing the pump capacity according to the control lever position, if the control lever is operated rapidly from the control lever position, the feedback gain is increased, so the response of the servo and pump swash plate is good, and the pump capacity changes. There will be no delays and no time lags. In addition, when the control lever is operated slowly from the neutral position, the feedback gain is changed according to the speed of the control lever, so the response of the servo and pump swash plate is also variable according to the speed. The excellent effect of improving sexual performance can be obtained.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of one embodiment of the present invention. FIG. 2 is a flowchart of the first embodiment of the present invention. FIG. 3 is a block diagram of the present invention. FIGS. 4 and 5 are diagrams showing examples of operating lever speed and feedback gain. FIG. 6 is a flowchart of a second embodiment of the present invention. FIG. 7 and FIG. 8 are diagrams showing an example of the operating lever position and feedback gain. FIG. 9 is an overall configuration diagram of a conventional example. FIG. 10 is a diagram showing the relationship between pump load pressure and pump discharge amount. FIG. 11 is a diagram showing the relationship between the operating lever and the pump discharge amount. Power source Variable displacement pump controller Proportional electromagnetic control valve Servo pump Swash plate Figure 1 Operation lever - Pressure sensor Displacement meter Tachometer

Claims (1)

[Claims] In a control device for a variable displacement pump in which the pump discharge amount is controlled by the load pressure applied to the pump and a control lever for driving an actuator, the position and operating speed of the control lever are adjusted depending on the load pressure of the pump. A control device for a variable displacement pump, characterized in that the feedback gain to the control device that varies the discharge amount of the pump is variable instead of constant.