JPH0641762B2 - Drive control device for hydraulic circuit - Google Patents

Description

TECHNICAL FIELD The present invention relates to a drive control device for a hydraulic circuit including a hydraulic pump, an actuator, and a switching valve for the actuator.

[Conventional technology]

Some actuators constituting a hydraulic circuit always or often have a load acting in a negative direction. For example,
The boom cylinder of the hydraulic shovel and the hydraulic motor for traveling correspond to this. For such an actuator,
Usually, speed control by a meter-out method is carried out.

[Problems to be Solved by the Invention]

In a circuit in which a negative load acts, the speed control by the meter-out method has a drawback that the speed of the actuator also changes when the size of the load changes, so that the speed control with good operability cannot be performed. In order to make up for this drawback, it is known to adopt a so-called load-sensing method, but this means that when the valve structure is complicated and there are multiple actuators as described above, those actuators are used. However, there is a drawback in that each of them cannot be load-compensated.

An object of the present invention is to provide a drive control device for a hydraulic circuit, which is capable of suppressing a change in the speed of an actuator even if the magnitude of a load changes, excluding the above-mentioned drawbacks of the prior art.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a hydraulic pump,
In a hydraulic circuit provided with an actuator connected to this hydraulic pump, on which a negative load pressure acts, and a switching valve that controls the drive of this actuator by a meter-out method, the side on which the negative load pressure on the actuator acts The pressure detecting means for detecting the differential pressure across the switching valve, the operation command signal generator for outputting a signal according to the command value of the operating means for operating the drive of the actuator, and the operating means for generating a negative load pressure. Selection means for selecting the pressure detection means when operated on the operating side and a flow rate to be discharged from the side on which the negative load pressure of the actuator acts on the basis of the output signal of the operation command signal generator. Based on the flow rate extraction means, the flow rate extracted by the flow rate extraction means and the detection value of the pressure detection means selected by the selection means, the switching valve is opened. Calculating means for calculating the area, characterized in that the opening area of the switching valve is provided and an opening area control means for controlling the opening area obtained by the computing means.

[Work]

When an operation command is issued to operate the actuator, the flow rate to be discharged is extracted from the side on which the negative load pressure of the actuator acts in response to the operation command. The opening area of the switching valve for obtaining the extracted flow rate is obtained by using the extracted flow rate and the differential pressure across the switching valve on the side where the load pressure of the switching valve detected by the pressure detecting means acts. Is calculated. When the load in the negative direction increases and the outlet pressure of the actuator increases, the calculated opening area decreases, and the switching valve also throttles accordingly. When the load becomes smaller, the reverse operation is performed. With the above operation, the actuator speed always coincides with the operation command value.

〔Example〕

 Hereinafter, the present invention will be described based on the illustrated embodiments.

FIG. 1 is a system diagram of a control device for a hydraulic shovel according to an embodiment of the present invention. In the figure, 1 is a variable displacement hydraulic pump,
Reference numeral 1a is a variable displacement mechanism for the hydraulic pump 1, and 2 is a regulator for operating the variable displacement mechanism 1a.
Reference numeral 3 denotes a traveling hydraulic motor (hereinafter, simply referred to as traveling motor) for traveling the lower traveling body of the hydraulic shovel, and 4 denotes a traveling direction switching valve for controlling the drive of the traveling motor 3 by a meter-out method. 5 is a boom cylinder for driving the boom in the front structure of the hydraulic shovel, 6
Is a boom direction switching valve for controlling the drive of the boom cylinder 5 by a meter-out method.

The traveling motor 3 and the boom cylinder 5 are connected to the hydraulic pump 1 in parallel with each other. Further, both the traveling directional control valve 4 and the boom directional control valve 6 are center-closed type directional control valves capable of controlling the opening area.

Reference numeral 7 is a relief valve that regulates the maximum discharge pressure of the hydraulic pump 1. 8B is a command signal X according to the operation of the boom lever.
_It is a boom operation command signal generator that outputs _LB.
Reference numeral 8R is a traveling operation command signal generator that outputs a command signal _XLR in response to the operation of the traveling lever. Reference numeral 9 is a pressure sensor for detecting the discharge pressure of the hydraulic pump 1, 10 is a pressure sensor for detecting the pressure of the traveling motor 3, and 11 is a pressure sensor for detecting the pressure of the boom cylinder 5. 12 is a boom operation command signal generator 8B and a traveling operation command signal generator 8
The control unit controls the traveling directional control valve 4, the boom directional control valve 6, and the regu- lator 2 by inputting signals from the R and the pressure sensors 9, 10, and 11 to perform the required calculation and control.

In this embodiment, only the traveling motor 3 and the boom cylinder 5 of the hydraulic shovel are shown as an example in which the load acts in the negative direction, and other actuators are not shown.

FIG. 2 is a block diagram of a part of the control unit shown in FIG. In the figure, reference numeral 15 is a switching element that selects the pressure sensor 11 on the side of the boom cylinder 5 that produces a negative load pressure. Since the negative load pressure is generated on the head side when the boom cylinder 5 is operated in the contracting direction, the switching element 15 is operated in the boom lowering direction of the boom lever (not shown) (the contracting direction of the boom cylinder 5). The pressure sensor 11 on the head side is selected according to. 16 the command signal X _LB outputted from the boom operation command signal generator 8R
Flow rate Q to be discharged from the boom cylinder 5 corresponding to
This is a function generator that finds. In this embodiment, the function generator 16 is provided with three types of flow characteristics I, II, III, and summer so as to select whether advance using any flow rate characteristics by switch or the like.

Reference numeral 17 is a calculation unit for inputting the selected pressure P _{B of the} boom cylinder 5 via the switching element 15 and the flow rate Q output from the function generator 16 and performing a required calculation. In this calculation unit 17, the opening area A of the boom directional control valve 6 is obtained by the following calculation.

Here, c: flow coefficient g: acceleration of gravity γ: specific weight.

Reference numeral 18 denotes a function generator, and the stroke L of the boom direction switching valve 6 for making the opening area of the boom direction switching valve 6 equal to the opening area obtained by the calculation unit 17 is obtained. A switching valve command signal output mechanism 19 outputs a command signal to the boom direction switching valve 6 so that the stroke L obtained by the function generator 18 is achieved.

Next, the operation of this embodiment will be described. Now, when a boom lever (not shown) is operated to issue a command to lower the boom (to drive the boom cylinder 5 in the contraction direction), the boom operation command signal generator 8B outputs a signal X _LB in response thereto. In the control unit 12, this signal L _LB is sent to the function generator 16
And outputs the flow rate Q corresponding to the signal X _LB according to the flow rate characteristic selected at that time, for example, the flow rate characteristic I. The calculation unit 17 inputs the flow rate Q and the detection value P _B of the pressure sensor connected to the head side of the boom cylinder 5, and calculates the opening area A of the boom directional control valve 6 by the above formula. In this case, since the pressure of the tank port (tank) of the switching valve is considered to be zero, only the input signal P _B is used. The function generator 18 obtains the stroke L of the boom directional switching valve 6 corresponding to the opening area A, and outputs a signal that causes the stroke L from the switching valve command signal output mechanism 19 to the boom directional switching valve 6. As a result, the boom direction switching valve 6 is driven by the stroke L.

In the state where the boom cylinder 5 is driven in the contracting direction as described above, if the load on the boom cylinder 5 increases due to, for example, a change in the arm or bucket, in the conventional device, the oil discharged from the head side of the boom cylinder 5 is used. Of the boom cylinder 5 increases, the driving speed of the boom cylinder 5 increases, and the speed becomes different from the speed expected by the operator from the operation amount of the boom lever, which makes accurate control difficult.
However, in the present embodiment, when the load on the boom cylinder 5 increases, the pressure on the head side increases, and this increased pressure is input to the calculation unit 17. In the calculation in the calculation unit 17, the opening area A calculated due to the increase in the pressure P _B becomes smaller, and as a result, the stroke output from the function generator 18 becomes smaller than the current stroke, and in the end,
The boom direction switching valve 6 is throttled. Therefore, the same state as when the throttle is inserted in the oil discharge circuit of the boom cylinder 5 is reached, the flow rate is limited, and the drive speed of the boom cylinder 5 is suppressed to be constant. Therefore, the operator can control the boom with a feeling corresponding to the operation amount of the boom lever, and the operability becomes extremely good.

The control of the traveling motor 3 is also the same as the control of the boom cylinder 5 by providing a switching element, a function generator for obtaining a flow rate, an arithmetic unit, a function generator for obtaining a stroke, and a switching valve command signal output mechanism separately. Will be carried out.

When the boom cylinder 5 is operated in the contracting direction and the head side pressure is always high, the rod side pressure sensor 11 and the switching element 15 can be omitted.

As described above, in this embodiment, when the boom cylinder is operated in the contracting direction, the opening area of the boom directional control valve is controlled based on the flow rate of the oil to be discharged and the discharge side pressure according to the operation. Therefore, even if the load changes, the opening area of the switching valve can be controlled by detecting the pressure to obtain the boom cylinder speed according to the operation amount, and the operability can be significantly improved. Further, since the above control can be performed independently for each actuator, the circuit can be configured by a simple parallel circuit. Further, since a plurality of flow rate characteristics can be selected in the function generator for obtaining the flow rate, the drive speed of the boom cylinder can be selected according to the work content, and the workability can be improved.

In the description of the above embodiment, the boom cylinder and the traveling motor of the hydraulic shovel are exemplified as the actuator, but the actuator is not limited to this, and the present invention can be applied to any actuator if the load acts in the negative direction. You can Further, in the above description of the embodiment, the tank pressure is considered to be 0. However, when the tank pressure is not 0, the difference between the pressure selected by the switching element and the tank pressure may be used for the calculation of the opening area. Good.

〔The invention's effect〕

As described above, in the present invention, in order to control the flow rate to be discharged from the actuator according to the operation amount on the side on which the negative load pressure of the actuator acts, the difference on the side on which the negative load pressure of the switching valve acts. Since the opening area of the switching valve of the actuator is controlled based on the pressure, it is possible to suppress the change in actuator speed due to the change in load,
Therefore, the speed control can be performed according to the operation amount, and the operability can be significantly improved. Further, since the control of the opening area can be performed independently for each actuator, the circuit can be configured by a simple parallel circuit.

[Brief description of drawings]

FIG. 1 is a system diagram of a hydraulic shovel control device according to an embodiment of the present invention, and FIG. 2 is a block diagram of a part of the control unit shown in FIG. 1 ... hydraulic pump, 3 ... travel motor, 4 ... travel direction switching valve, 5 ... boom cylinder, 6 ... boom direction switching valve, 8B ... boom operation command signal generator, 8R ...
… Running command signal generator, 9, 10, 11 …… Pressure sensor, 12 …… Control unit, 15 …… Switching element, 16, 18…
… Function generator, 17 …… Calculator

Claims (3)

[Claims] 1. A hydraulic circuit comprising a hydraulic pump, an actuator connected to the hydraulic pump, on which a negative load pressure acts, and a switching valve for controlling the drive of the actuator by a meter-out method. A pressure detection means for detecting a differential pressure across the switching valve on the side where a negative load pressure acts, and an operation command signal generator for outputting a signal according to a command value of an operation means for operating the drive of the actuator, Selection means for selecting the pressure detecting means when the operating means is operated to the side where negative load pressure acts, and negative load pressure of the actuator acts based on the output signal of the operation command signal generator. Flow rate extraction means for extracting the flow rate to be discharged from the side, detection of the flow rate extracted by the flow rate extraction means and the pressure detection means selected by the selection means A hydraulic circuit for calculating the opening area of the switching valve based on the above, and an opening area control means for controlling the opening area of the switching valve to the opening area obtained by the calculating means. Drive controller. 2. The opening area control means according to claim 1, further comprising another extraction means for extracting the stroke of the switching valve based on the opening area obtained by the computing means, A drive control device for a hydraulic circuit, comprising: output means for instructing the switching valve of the stroke obtained by the extraction means. 3. The drive control device for a hydraulic circuit according to claim (1), wherein the extraction means has a plurality of selectable flow rate characteristics.