JPH0451670B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic drive device for driving an inertial mass, and more particularly to a hydraulic drive device having an electro-hydraulic servo that compensates its characteristics according to the pressure of pressure oil discharged from a hydraulic pump. .

FIG. 1 is a circuit diagram showing the basic configuration of a conventional hydraulic drive device.

In this figure, 1 is a variable displacement hydraulic pump, for example, a swash plate type hydraulic pump, and 2 is this hydraulic pump 1.
The connected hydraulic actuator, for example a hydraulic cylinder, 3 is an inertial load of mass M actuated by this hydraulic cylinder 2. Reference numeral 4 denotes a discharge amount control mechanism for the above-mentioned hydraulic pump 1, which is housed in a housing 4a and is housed in the housing 4a, and is, for example, a discharge amount control mechanism for the hydraulic pump 1.
a piston 4b for tilting the swash plate, a solenoid valve 4c,
4d, and a discharge amount detector that detects the discharge amount of the hydraulic pump 1 and outputs a discharge amount signal _Qp , that is, a displacement meter 4e that detects the displacement of the swash plate. Further, 5 is a discharge amount control device which outputs a digital command signal for controlling the discharge amount of the hydraulic pump 1, that is, a command signal Q ₀ ' for controlling the discharge amount control mechanism 4, which is an on-off servo mechanism, to the electromagnetic valves 4c and 4d. do. 6
7 is an operating lever that outputs a target discharge amount signal _Q0 to this discharge amount control device 5, and 7 is a pressure that detects the pressure of the pressure oil discharged from the hydraulic pump 1 and outputs a pressure signal P to the discharge amount control device 5. It is a detector. Note 8
9 is a hydraulic power source, 9 is a tank, and 11 is a pipe line connecting the hydraulic pump 1 and the hydraulic cylinder 2.

FIG. 2 is an explanatory diagram showing the basic configuration of the discharge amount control device 5 provided in the hydraulic drive device shown in FIG. 1. This discharge amount control device 5 is composed of a microcomputer, and includes a central processing unit 5a, an output I/O interface 5b, and amplifiers 5c and 5d connected to the aforementioned solenoid valves 4c' and 4d.
a memory 5e for storing a control procedure program;
The aforementioned operating lever 6, pressure detector 7, displacement meter 4
The target discharge amount signal Q ₀ outputted from e respectively,
It includes an A/D converter 5f that converts the pressure signal P and the discharge amount signal Q _p , that is, analog signals, into digital signals.

This discharge amount control device 5 receives a target discharge amount signal _Q0 from the operating lever 6, a pressure signal P from the pressure detector 7,
The drive command value of the hydraulic pump 1 is calculated based on the control procedure program, and the command signal Q ₀ ' is outputted to the electromagnetic valves 4c and 4d, and the discharge amount signal which is the output of the displacement meter 4e is It is controlled by an on-off servo, which is an example of an electro-hydraulic servo, so that Q _p becomes equal to the target discharge amount signal Q ₀ .

Note that the on-off servo is implemented as follows. That is, as shown in FIG.
The area of the left chamber 4f forming both sides of b is the area of the right chamber 4
It is larger than the area of g. The left chamber 4f is connected to the hydraulic pressure source 8 through the solenoid valve 4c,
It is connected to a tank 9 through a solenoid valve 4d, and the right side chamber 4g is directly connected to a hydraulic power source 8. Therefore, when both the solenoid valve 4c and the solenoid valve 4d are energized, the left chamber 4f communicates with the hydraulic power source 8, and the piston 4b moves to the right in FIG. 1 due to the area difference, and the solenoid valve 4c is demagnetized. However, when the solenoid valve 4d is energized, the piston 4b is held stationary, and the solenoid valves 4c, 4 are energized.
When d is demagnetized together, the piston 4b moves to the left due to the pressure in the right chamber 4g. This combination of movements is performed every extremely short period (sampling period).

By the way, in the conventional hydraulic drive device shown in FIG. 1, the mass of the inertial load 3 is M, and the hydraulic pump 1 is
The spring constant due to the compressibility of the oil between the hydraulic cylinder 2 and the hydraulic cylinder 2 is k _H = B/V (here, B is the bulk modulus of the oil, and V is the volume between the hydraulic pump 1 and the hydraulic cylinder 2), and the hydraulic pressure is When expressed in a block diagram with k ₀ representing the transfer function of the pump 1, A representing the area of the hydraulic cylinder 2, and s representing the Laplace operator, the result is shown in FIG. In addition, in this FIG. 3, 1 is the above-mentioned hydraulic pump, and 5 is a discharge amount control device. Reference numeral 20 denotes a hydraulic drive system, which includes a hydraulic cylinder 2, a pipe line 11 connecting the hydraulic pump 1 and the hydraulic cylinder 2, and an inertial load 3.

When the hydraulic drive system 20 in FIG. 3 is equivalently converted, it is expressed as k _H ·A/(Ms ² +k _H ·A ² ). Therefore, this hydraulic drive system 20 has Ms ²
It has a second-order system of s and does not have a viscosity term of s (first-order system), and therefore has the problem of generating vibration when driven.

Furthermore, in order to prevent such vibrations in the hydraulic drive system 20, conventionally, the hydraulic pump 1 and the hydraulic cylinder 2 are
A hydraulic drive device has been proposed in which a constriction is provided in the middle of a conduit 11 that communicates with the duct to provide viscous resistance. The hydraulic drive system of such a hydraulic drive device is, for example, k _H・A/(Ms ² +M・k _H・cs+k _H A ² )
It has a viscosity term (first-order system) of s, and therefore vibrations are prevented from occurring. Note that c indicates the viscosity coefficient. However, since this conventional hydraulic drive device is provided with a restriction, a large pressure loss occurs in the pipe line 11 that connects the hydraulic pump 1 and the hydraulic cylinder 2, especially when the driving speed of the hydraulic cylinder 2 is high. has a defect that causes large energy loss.

The present invention has been made in view of the actual situation in the prior art, and its purpose is to improve the flow of hydraulic actuators such as hydraulic pumps and hydraulic actuators such as hydraulic cylinders without intervening a restriction in the middle of the pipe connecting the hydraulic pump and hydraulic actuators such as hydraulic cylinders. An object of the present invention is to provide a hydraulic drive device that can prevent vibrations from occurring in a drive system.

In order to achieve this object, the present invention provides a variable displacement hydraulic pump, a discharge amount control device that outputs a digital command signal to an on-off servo mechanism that controls the discharge amount of the hydraulic pump, and a discharge amount control device that outputs a digital command signal to an on-off servo mechanism that controls the discharge amount of the hydraulic pump. a discharge amount detector that detects the pressure of the pressure oil discharged from the hydraulic pump and outputs a discharge amount signal to the discharge amount control device; and a pressure detector that detects the pressure of pressure oil discharged from the hydraulic pump and outputs a pressure signal to the discharge amount control device. and an operation lever that outputs a target discharge amount signal to the discharge amount control device, and a hydraulic drive device that controls driving of the hydraulic pump by the on-off servo mechanism, which differentiates the pressure signal and calculates the differential value. The discharge amount control device includes a characteristic compensator that adds the signal and the discharge amount signal as an analog value and outputs the result to the discharge amount control device as a discharge amount signal, and the discharge amount control device adds the result to the discharge amount control device. A digital command signal is output to the on-off servo mechanism so that the signal value of the discharge amount signal and the signal value of the target discharge amount signal are equal.

FIG. 4 is a block diagram showing the basic principle of the hydraulic drive system of the present invention. In this block diagram, the pressure differential is electrically determined from the pressure P as kp·s (kp is the gain of pressure differential compensation), and this is fed back to form the hydraulic drive system 20, k _H /s.
The characteristics are compensated to cancel the term.
That is, if block 21 in FIG. 4 is equivalently transformed, it becomes k _H /s (1 + k _H · kp), and if the gain kp is adjusted to 1 + k _H · kp0,
The k _H /s term is canceled.

This makes the hydraulic drive system 20' a first-order system, and therefore vibrations are prevented from occurring. Note that when trying to realize the basic principle shown in FIG. 4 in the discharge amount control device 5 shown in FIGS. 1 and 2, since the rate of change in the pressure of the pressure oil discharged from the hydraulic pump 1 is extremely fast, A high-speed A/D converter such as 5f must be used. Additionally, digital circuits generally generate noise, and differentiation often picks up a large amount of this noise, making it impractical.

5 to 7 are explanatory diagrams showing one embodiment of the hydraulic drive device of the present invention that also takes into consideration such circumstances, FIG. 5 is a circuit diagram showing the basic configuration, and FIG. FIG. 7 is a circuit diagram showing an example of a characteristic compensator constituting the hydraulic drive device shown in the figure, and FIG. 7 is a block diagram of the hydraulic drive device shown in FIG. 5. In these figures, the same components as those shown in FIGS. 1 to 4 described above are designated by the same reference numerals.

In FIG. 5, 10 is a characteristic compensator which differentiates the pressure signal P detected by the pressure detector 7 in an analog manner, and combines the differential signal with the discharge amount signal Q detected by the displacement meter 4e. _p in an analog manner and outputs the result to the discharge amount control device 5 as another discharge amount signal Q _p '. This characteristic compensator 10
For example, as shown in FIG. 6, there is a differentiator 10a connected to the pressure detector 7, an amplifier 10b connected to the differentiator 10a, an amplifier 10c connected to the displacement meter 4e, an amplifier 10b, and an amplifier 10c. It consists of an adder C10d. This characteristic compensator 10 differentiates the pressure signal P from the pressure detector 7 with a differentiator 10a, and adjusts the gain with an amplifier 10b. Further, the discharge amount signal Q _p of the displacement meter 4e is adjusted by the amplifier 10c. and amplifier 10b,1
The signals output from each of the adder 10
d to generate another discharge amount signal Q _p '.
That is, as illustrated in the block diagram of FIG.
The characteristic compensator 10 generates Q _p ′=Q _p −k _p ′·s. Note that the gain k _p ′ and the gain k _p shown in FIG.
The relationship with is expressed as k _p ′=k _p (k ₀ +1)/k ₀ .
Then, another discharge amount signal Q _p ′ obtained as described above is inputted to the above-mentioned A/D converter 5f of the discharge amount control device 5, and in this discharge amount control device 5, the discharge amount signal Q _p ′ is The signal value is controlled to be equal to the signal value of the target discharge amount signal _Q0 .
Note that the other basic configurations are the same as those shown in FIGS. 1 and 2.

In one embodiment configured in this way, a pipe line 11 connecting the hydraulic pump 1 and the hydraulic cylinder 2
electrical means without intervening an aperture in the middle of the process,
That is, by the characteristic compensator 10, k _H /s in FIG.
Therefore, the hydraulic drive system 30 shown in FIG. 7 can be made into a first-order system, and the occurrence of vibration in the hydraulic drive system 30 can be reliably prevented. .

In addition, since the characteristic compensator 10 processes the pressure signal P output from the pressure detector 7 and the discharge amount signal Q _p output from the displacement meter 4e, that is, analog signals, high-speed A/ There is no need for a D converter, and there is no possibility that the differential value will become unstable due to noise in the digital circuit.

In addition, in this embodiment, it is sufficient to simply provide the characteristic compensator 10, that is, the conventional on-off servo discharge amount control device 5 and discharge amount control mechanism 4 shown in FIGS. 1 and 2 can be used as they are. The structure is simple.

Since the hydraulic drive device of the present invention is configured as described above, it is possible to prevent the occurrence of vibration in the drive system of the hydraulic actuator without interposing a throttle in the middle of the pipe connecting the hydraulic pump and the hydraulic actuator. Therefore, pressure loss in the pipeline can be suppressed to a minimum, energy loss can be prevented, and in particular,
The discharge amount control device is equipped with a characteristic compensator that adds the differential signal obtained by differentiating the discharge pressure of the hydraulic pump and the discharge amount signal as an analog value, and outputs the result as a discharge amount signal to the discharge amount control device. The digital command signal is output to the on/off servo mechanism so that the signal value of the discharge amount signal output from the compensator and the signal value of the target discharge amount signal output from the control lever are equal, so high-speed operation is possible. This method does not require an A/D converter, is economical, and has the effect of ensuring stable control performance without causing the differential value to become unstable due to noise in the digital circuit.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the basic configuration of a conventional hydraulic drive device, FIG. 2 is an explanatory diagram showing the basic structure of a discharge amount control device provided in the hydraulic drive device shown in FIG. 1, and FIG. FIG. 1 is a block diagram of the hydraulic drive device shown in FIG. 4, FIG. 4 is a block diagram showing the basic principle of the hydraulic drive device of the present invention, and FIGS. 5 to 7 are explanations showing one embodiment of the hydraulic drive device of the present invention. In the figures, Fig. 5 is a circuit diagram showing the basic configuration, Fig. 6 is a circuit diagram showing an example of a characteristic compensator that constitutes the hydraulic drive device shown in Fig. 5, and Fig. 7 is a circuit diagram showing the hydraulic drive shown in Fig. 5. FIG. 2 is a block diagram of the device. 1... Variable displacement hydraulic pump, 2... Hydraulic cylinder (hydraulic actuator), 3... Inertial load, 4
...discharge rate control mechanism, 4e...displacement meter (discharge rate detector), 5...discharge rate control device, 6...operation lever, 7...pressure detector, 10...characteristic compensator, 1
0a...Differentiator, 10b, 10c...Amplifier, 1
0d...Adder, 11...Pipe line.

Claims (1)

[Claims] 1. A variable displacement hydraulic pump, a discharge amount control device that outputs a digital command signal to an on/off servo mechanism that controls the discharge amount of this hydraulic pump, and a discharge amount control device that detects the discharge amount of the hydraulic pump and uses the discharge amount signal to control the discharge amount. A discharge amount detector outputs to the device, a pressure detector detects the pressure of the pressure oil discharged from the hydraulic pump and outputs a pressure signal to the discharge amount control device, and a pressure detector outputs a target discharge amount to the discharge amount control device. In a hydraulic drive device that includes an operation lever that outputs a signal and controls driving of the hydraulic pump by the on-off servo mechanism, the pressure signal is differentiated, and the differentiated signal and the discharge amount signal are used as analog values. The discharge amount control device includes a characteristic compensator that adds the result and outputs the result as a discharge amount signal to the discharge amount control device, and the discharge amount control device adds the signal value of the discharge amount signal output from the characteristic compensator and the target discharge amount. A hydraulic drive device characterized in that a digital command signal is output to the on-off servo mechanism so that the signal value of the quantity signal is equal to the signal value of the quantity signal.