JPH07111179B2 - Hydraulic pump controller - Google Patents

Description

The present invention relates to a control device for a hydraulic pump used in civil engineering / construction machinery such as a hydraulic excavator, and more particularly to detecting the displacement of the hydraulic pump and performing feedback control thereof. The present invention relates to a control device for a hydraulic pump that controls displacement.

[Prior Art] In civil engineering and construction machinery such as hydraulic excavators, pressure oil discharged from a hydraulic pump is guided to a hydraulic actuator via a direction switching valve and driven to operate work members such as a boom and an arm. Do the necessary work. The hydraulic pump is classified into a fixed displacement type and a variable displacement type. When the variable displacement type is used, the hydraulic pump is provided with a control device for controlling the pump displacement according to the required flow rate of the directional control valve.

As a conventional example of a control device for this hydraulic pump, there is, for example, the one described in JP-A-60-125402, which controls displacement of the hydraulic pump and, in a swash plate pump, the position of the swash plate. A controller that calculates the operation command value from the displacement detector to detect, the target value of the swash plate position of the hydraulic pump and the swash plate position detected by the displacement detector, and outputs the corresponding command signal, and the command signal from the controller It is equipped with a pump regulator that controls the pump capacity by operating the swash plate of the hydraulic pump, and feeds back so that the deviation between the target value of the swash plate position and the swash plate position detected by the displacement detector becomes zero. It controls.

(Problems to be Solved by the Invention) However, in this conventional control device, an abnormality occurs in the detection signal input to the controller due to a failure of the displacement detector, an abnormality in the signal transmission path between the displacement detector and the controller, or the like. In this case, feedback control is performed by the abnormal detection signal, so that displacement of the hydraulic pump cannot be controlled because the swash plate position greatly deviates from the target value, and therefore speed control of the hydraulic actuator cannot be performed, which is extremely dangerous. There was a problem of inviting the state.

It is an object of the present invention to provide a hydraulic pump control device that enables pump displacement control even when an abnormality occurs in a detection signal.

[Means for Solving the Problems]

In order to achieve the above object, the present invention adopts the following configurations.
That is, a control device for a hydraulic pump that supplies pressure oil to a hydraulic actuator via a directional switching valve, the detecting means for detecting displacement of the hydraulic pump, and the hydraulic pump according to the required flow rate of the directional switching valve. A target value of the displacement volume is calculated, an operation command value is calculated from the target value and the displacement volume detected by the detection means, and control means for outputting a corresponding command signal and displacement of the hydraulic pump based on the command signal. In a control device for a hydraulic pump including a pump regulator that operates a volume varying means and controls a displacement of a hydraulic pump, the control means is a function that is preset from a target value of the displacement volume to the target value. A first control path for obtaining a basic command value based on the relationship, and a deviation between the target value of the displacement and the displacement detected by the detecting means. A second control path for obtaining a correction value for the basic command value from this deviation, and a control calculating means having an adding portion for adding the correction value to the basic command value to obtain the operation command value, and the detecting means. An abnormality determining means for determining an abnormality of the detection signal, and a switch means for shutting off the second control path of the control calculating means when the abnormality determining means determines the abnormality of the detection signal. .

[Action]

In the present invention thus configured, the second control path functions when the detection signal is normal, and the correction value obtained from the deviation between the target value of the displacement and the detection value is obtained in the first control path. It is added to the basic command value and feedback control is performed. When an abnormality occurs in the detection signal, the switch means shuts off the second control path, the operation command value is directly obtained from the basic command value obtained in the first control path, and the hydraulic pump is controlled in open loop. It

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

In FIG. 1, reference numeral 1 is a variable displacement hydraulic pump, the displacement of which is controlled by a displacement variable mechanism, that is, a swash plate 2. The pressure oil discharged from the hydraulic pump 1 is supplied from the discharge pipe 3 through the direction switching valve 4 to the hydraulic motor 5 as a load, and drives it.

Reference numeral 6 is a control device for the hydraulic pump 1, which includes a sensor group of a differential pressure gauge 7, a pressure detector 8, a displacement detector 9, a controller 10, an electromagnetic proportional valve 11, and a pump regulator 12.

The differential pressure gauge 7 detects the differential pressure ΔP between the discharge pressure Ps of the hydraulic pump 1 and the load pressure PL of the hydraulic motor 5, the pressure detector 8 detects the discharge pressure Ps of the hydraulic pump 1, and the displacement detector 9 detects the hydraulic pressure. The position of the swash plate 2 of the pump 1, that is, the displacement, is detected, and the corresponding electric signals are sent to the controller 10. The controller 10 calculates the target position of the swash plate 2 of the hydraulic pump 1 based on these detection signals, and outputs the corresponding command signal X.
Is output. The solenoid proportional valve 11 converts this command signal X into a hydraulic signal and loads it on the pump regulator 12.

The pump regulator 12 has a servo cylinder 13 that drives the swash plate 2 of the hydraulic pump 1, and a servo control valve 14 that determines the movement of the servo cylinder 13. The servo control valve 14 has a hydraulic pressure from the solenoid proportional valve 11 at one end. It has a pressure receiving portion 15 to which a signal is guided and a spring 16 at the other end, and the servo control valve 14 is driven to the left side in the figure against the spring 16 according to the level of the hydraulic signal guided to the pressure receiving portion 15. , Piston position of servo cylinder 13,
That is, the position of the swash plate 2 of the hydraulic pump 1 is determined. The discharge pressure of the hydraulic pump 1 is introduced into the servo cylinder 13 and the servo control valve 14 as a fluid for driving the servo cylinder 13 via a check valve 17.

Reference numeral 18 is a pilot pump, the pilot pressure of which is set by a relief valve 19. This pilot pressure is sent to the solenoid proportional valve 11 and used as the hydraulic pressure source of the hydraulic pressure signal. Further, the pilot pressure is introduced to the downstream side of the above-mentioned check valve 17 via the check valve 20, and is used as the second fluid for driving the servo cylinder 13 when the discharge pressure of the hydraulic pump 1 is low. In addition, 21 is a tank.

The content of the calculation performed by the controller 10 is shown in a functional block diagram in FIG.

In FIG. 2, reference numeral 30 is a block for calculating the target position θo of the swash plate 2 of the hydraulic pump 1 from the differential pressure ΔP and pump discharge pressure Ps, and reference numeral 31 is the command signal X from the target position θo. This is the block to generate.

In block 30, in block 32, the differential pressure target discharge amount θ for maintaining the differential pressure ΔP at the target differential pressure ΔPo from the differential pressure ΔP.
The change rate Δp of Δp is obtained, and the change rate Δp
Is integrated by the integration block 33 to obtain the target differential pressure discharge amount θΔp. On the other hand, in block 34, the discharge pressure of the hydraulic pump 1
The input limit target discharge amount θT is obtained from Ps based on the input torque limit function stored in advance. The two target values θΔp and θT thus obtained are selected by the minimum value selection block 35, and the smaller value is selected to determine the target value of the displacement of the hydraulic pump 1, that is, the target position θo of the swash plate 2. It

The block 31 has a first control path 36 and a second control path 37, and in the first control path 36, a swash plate 2 is provided at a block 38.
The target position θo of is converted into a basic command value io on the basis of a predetermined functional relationship. This function is for converting the target position θo of the swash plate 2 into the basic command position io according to the characteristics of the solenoid proportional valve 11, and is stored in the controller 10 in advance.

In the second control path 37, the difference between the target position θo of the swash plate 2 and the position θ of the swash plate 2 detected by the displacement detector 9 is obtained by the subtraction unit 39, and the block is passed through the block 40 having the switch function. At 41, the proportional constant K is multiplied to obtain the correction value ic.

The basic command value io obtained in the block 38 and the correction value ic obtained in the block 41 are added by the adder 42 to obtain the operation command value ix, the operation command value ix is amplified by the amplifier 43, and the command signal X
Is converted to.

On the other hand, the detection signal of the position θ of the swash plate 2 obtained by the displacement detector 9 is sent to the abnormality determination block 44, and it is determined whether or not the detection signal is abnormal. This determination can be made, for example, by pre-storing the level range of the detection signal at the time of normality and checking whether the level of the detection signal is within that range. If the detection signal deviates from the range, it is abnormal. Is determined. The block 44 outputs a level 0 signal when the detection signal is normal, and outputs a level 1 signal when an abnormality is determined. This signal is sent to block 40
40 is in the position shown in the figure when the signal is 0, transmits the deviation Δθ to the block 41, and when the signal becomes 1, the second control path 37
Is cut off, and the value of Δθ = 0 of the block 45 prepared in advance is output. Therefore, the correction value ic = 0, and the value of the basic command value io in the adding section 42 becomes the operation command value ix as it is.

Next, the operation of this embodiment configured as described above will be described.

First, in the preceding block 30, the target differential pressure discharge amount θΔ
When p is smaller than the input restriction target discharge amount θT, the differential pressure target discharge amount θΔp is selected in the minimum value selection block 35, and this becomes the swash plate target position θo. Therefore, the position of the swash plate 2 of the hydraulic pump 1 is controlled so that the differential pressure ΔP is maintained at the target differential pressure ΔPo. Here, the differential pressure ΔP is a value that changes according to the required flow rate (operation amount) of the directional control valve 4,
The swash plate target value θo becomes a target value according to the required flow rate.
That is, the discharge amount of the hydraulic pump 1 is controlled by the load sensing control to be a flow rate according to the required flow rate.
When the discharge pressure Ps of the hydraulic pump 1 increases and the input limit target discharge amount θT becomes smaller than the differential pressure target discharge amount θΔp, the input limit target discharge amount θT is selected in the minimum value selection block 35, and this is the swash plate target position. θo. For this reason,
The position target value θo of the swash plate 2 of the hydraulic pump 1 is limited to the input limit target discharge amount θT, and the input limit control of the hydraulic pump 1 is performed.

In the subsequent block 31, when there is no abnormality in the detection signal of the displacement detector 9, the abnormality determination block 44 outputs a level 0 signal, the block 40 is at the position shown, and the second control path 37 is Since it is not cut off, the basic command value i from the swash plate target position θo obtained in block 30 is set in the first control path 36.
o is obtained, the correction value ic corresponding to the deviation Δθ is obtained in the second control path 37, and these are added to obtain the operation command value ix. Therefore, the command signal X corresponding to the operation command value ix is sent to the solenoid proportional valve 11, and the swash plate position of the hydraulic pump 1 is controlled accordingly. That is, when the detected swash plate position θ is larger than the target position θo, a negative value corresponding to the deviation Δθ is calculated as the correction value ic, so that the operation command value ix becomes smaller than the basic command value io. The position of the swash plate is controlled so as to be corrected and the deviation Δθ becomes smaller. In the opposite case, since a positive value is calculated as the correction value ic, the operation command value ix is corrected to be larger than the basic command value io, and the swash plate position is similarly controlled so that the deviation Δθ becomes smaller. It In other words, the first control path 36 and the second control path 37 are combined to form a feedback control system, and the swash plate 2 of the hydraulic pump 1 is feedback-controlled.

On the other hand, when an abnormality occurs in the detection signal of the displacement detector 9 due to a failure of the displacement detector 9 or an abnormality in the signal transmission system from the displacement detector 9 to the controller 10, the abnormality determination block A signal of level 1 is output from 44, and the block 40 shuts off the second control path 37 and the correction value ic
Is ic = 0. Therefore, a value equal to the basic correction value io is obtained as the operation command value ix, and the swash plate 2 of the hydraulic pump 1 is controlled by this operation command value ix. That is, even if the second control path 37 is shut off, the first control path 36
Functions as an open loop control system, and hydraulic pump 1
The swash plate position is controlled by its open loop. Therefore, even if an abnormality occurs in the detection signal, the displacement control of the hydraulic pump 1 is possible, and the displacement control of the hydraulic pump 1 is disabled, so that the operating speed of the hydraulic motor 5 cannot be controlled, which causes a dangerous state. Can be prevented.

Therefore, according to the present embodiment, when the detection signal from the displacement detector 9 is normal, the electromagnetic proportional valve 11 is controlled by feedback control, so that the displacement of the hydraulic pump 1 can be accurately controlled. When an abnormality occurs in the detection signal from 9, the solenoid proportional valve 11 is controlled by the open loop control, so that the hydraulic pump 1 is not out of control and the reliability can be improved. Further, since the operation command value is obtained by adding the basic command value and the correction value, the required responsiveness and stability can be obtained without increasing the proportional constant K of the correction value.

In the above embodiment, the swash plate target position θo is calculated by combining the load sensing control and the input torque limit control in the block 30, but the swash plate target position θo is calculated according to the required flow rate. It is not limited to this as long as it has a different value, and any other method can be adopted.

〔The invention's effect〕

According to the present invention, the pump displacement control can be performed even when an abnormality occurs in the detection signal, so that the reliability of the pump displacement control can be improved and the safety of the speed control of the hydraulic actuator can be ensured. Further, since the operation command value is obtained by adding the basic command value and the correction value, the required responsiveness and stability can be obtained without increasing the proportional constant K of the correction value.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a hydraulic circuit to which a control device according to an embodiment of the present invention is applied, and FIG. 2 is a functional block diagram showing calculation contents of the controller shown in FIG. Explanation of symbols 1 …… hydraulic pump 2 …… swash plate (displacement volume changing means) 9 …… displacement detector 10 …… controller (control means) 12 …… pump regulator 36 …… first control path 37 …… first 2 control path 40 ...... Switch means 42 ...... Adding section 44 ...... Abnormality judgment block θo ...... Swash plate target position io ...... Basic command value Δθ ...... Deviation ic ...... Correction value ix ...... Operation command value X ... ... Command signal

Claims (1)

[Claims] 1. A control device for a hydraulic pump that supplies pressure oil to a hydraulic actuator via a directional switching valve, the detecting means detecting the displacement of the hydraulic pump, and the required flow rate of the directional switching valve. A target value of the displacement of the hydraulic pump is calculated, an operation command value is calculated from the target value and the displacement detected by the detection unit, and a control unit that outputs a corresponding command signal and a hydraulic pressure based on the command signal are output. In a control device for a hydraulic pump, which comprises a pump regulator for controlling the displacement volume of the pump and controlling the displacement of the hydraulic pump, the control means is preset from the target value of the displacement volume to the target value. A first control path for obtaining a basic command value based on the obtained functional relationship, a deviation between the target value of the displacement and the displacement detected by the detecting means. A second control path for obtaining a correction value for the basic command value from the deviation, and a control calculation means having an adding section for adding the correction value to the basic command value to obtain the operation command value; An abnormality determining means for determining abnormality of the detection signal of the means, and a switch means for shutting off the second control path of the control calculating means when the abnormality determining means determines the abnormality of the detection signal. Characteristic hydraulic pump control device.