JPS62124354A - Control of closed circuit hydraulic drive unit - Google Patents

Abstract

PURPOSE:To carry out energy-saving operation, by calculating the reference operating inclination of a hydraulic pump based on the revolution number of a hydraulic motor, and changing the operating inclination of the hydraulic pump in a range that preset operating inclination varying limit width is added to or subtracted from the reference operating inclination so as to prevent the occurrence of a peak pressure. CONSTITUTION:The revolution number of a hydraulic motor 4 is detected by a revolution number detector 20, and the reference operating inclination theta of a variable capacity hydraulic pump 3 is calculated by a reference operating inclination arithmetic circuit 21 based on the detected value of the detector, while limit width alpha preset to an operating inclination varying limit width setting device is added to or subtracted from the reference operating inclination theta and a range theta+alpha-theta-alpha in which operating inclination can be changed is calculated. As the operating inclination of the variable capacity hydraulic pump 3 is varied in this range and this range also is varied gradually by the variation of the revolution number of the hydraulic motor 4, the operating inclination of the variable capacity hydraulic pump 3 does not change sharply and a peak pressure above a set pressure does not occur, so that wasteful energy consumption is not generated.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for controlling a closed-circuit hydraulic drive device, and more specifically, the present invention relates to a method for controlling a closed-circuit hydraulic drive device, and more specifically, a control method for a variable displacement hydraulic pump in a hydraulic drive circuit such as a hydraulic excavator where a large load inertia acts. This relates to a control method.

[Prior art and its problems]

In order to drive a hydraulic excavator, a crane, etc., a conventionally well-known hydraulic drive device 2 equipped with a hydraulic closed circuit 1 as shown in FIG. 3 is employed.

The device is provided with a hydraulic motor 4 driven by hydraulic oil pressure from a variable displacement hydraulic pump 3, and its rotation operates a load 5 such as an excavator. If the inertia of the load is large, even if the operating lever is suddenly moved to increase the hydraulic pressure in the closed circuit 1 in order to operate the load, the excavator with the large inertia will not be directly accelerated. At that time, when the pressure becomes greater than a predetermined value, the relief valve 6△ or 6B (installed in a closed circuit) opens, and the pressurized hydraulic oil that exceeds the relief pressure bypasses the hydraulic motor 4. It becomes every. This is a relief light to safely maintain a closed hydraulic circuit, but on the other hand, the power consumed by the variable volume hydraulic pump 3 that is used to boost the pressure of the bypassed hydraulic oil is not used, resulting in savings. There is a point in terms of energy. On the other hand, if the lever is operated so as to produce a lL force with a margin so that the relief valve described above does not open, the acceleration time of the load will be shortened, which is not preferable.

Therefore, from the perspective of energy saving, variable displacement hydraulic pump 3
There is a system in which the pressures PI and P2 on the discharge side and suction side of the pump are detected, and the tilting and rotation of the variable displacement hydraulic pump 3 is controlled based on the detected pressures. For example, in the device described in Japanese Patent Publication No. 60-5821, the relief valve 6A,
In order to obtain a high hydraulic pressure that does not open 6B,
The tilting movement of the variable 8-speed hydraulic pump 3 is adjusted.

If the inertia of the load is large, the pressure feedback of the lightning strike will exhibit the behavior shown in Figure 4. In other words, when the operating lever is pushed down while the hydraulic motor is stopped, the rotation angle of the variable displacement hydraulic pump is temporarily increased in a straight line in order to hasten the rise in the accelerating pressure of the hydraulic oil. Ru. As a result, the pump discharge amount increases, and a high accelerating pressure as shown by line B is generated in the hydraulic fluid, and a peak pressure rises. This pressure rapidly increases and exceeds the set pressure Ps, and also tends to exceed the relief pressure Pre. To prevent this, the tilting angle is made small, and the acceleration pressure is reduced accordingly. If the pressure decreases too much, sufficient pressure to encourage rotation of the hydraulic motor will not be obtained, so the 100 degree tilt angle is increased and the acceleration pressure is also increased. While repeating such operations, the rotation of the hydraulic motor is gradually increased as indicated by line C, while overcoming large inertia, until the acceleration pressure approaches the set pressure Ps. When a load with large inertia is increased to a predetermined rotational speed Na,
Thereafter, it is rotated at a constant rotational speed, and the shovel or the like is displaced to a desired position.

In such an operation, stable discharge pressure control during acceleration and deceleration cannot be performed. To this end, there are countermeasures such as slowing down the tilting response of the variable volume) 2 hydraulic pump and lowering the pressure control gain, but it is important to improve the ability of the hydraulic motor to follow minute movements of the control lever. The problem remains that acceleration and deceleration take time.

(Objective of the Invention) The present invention was made in order to solve two problems.The purpose of the present invention is to improve the ability of the hydraulic motor to follow minute operations of the operating lever, and to accelerate and decelerate the load. This is a closed circuit hydraulic drive system that achieves this in the shortest possible time, and also minimizes the fluctuation range of the pressure during acceleration/deceleration and the amount of rotation of the variable displacement hydraulic pump, so that no peak pressure occurs relative to the set pressure. The object of the present invention is to provide a control method.

[Structure of the invention]

The characteristics of the control f′j11 method of a closed circuit hydraulic drive device of the present invention are as follows, with reference to FIG. Pressure pressure on the discharge side and suction side 11. P2 is detected, and based on the pressure, the town is transformed (d). Along with detecting the number,
Based on the detected value, the reference tilting angle θ of the hydraulic pump that is required from time to time is calculated, and the tilting angle change limit width α set in advance to generate acceleration or deceleration pressure is calculated as the reference tilting angle θ. Add to or subtract from the lower limit range (θ−α) to (
The tilting angle of the variable displacement slide pressure pump 3 is changed within θ+α), the range of pressure fluctuation during acceleration and deceleration is reduced, and the pressure is limited to the maximum set pressure Pa or less.

[For production]

The pressure on the discharge side and suction side of the variable displacement hydraulic pump 3 is detected, and based on the higher pressure, e.g. (θ−
α) ~ (θ+α), the tilt angle decrease amount △θ is (+'f
, and prevents peak pressure from occurring during acceleration and deceleration. On the other hand, the rotation speed of the hydraulic motor 4 is detected, and based on the detected value, the reference tilting angle θ of the hydraulic pump that is required from time to time is calculated, and a preset tilting angle change limit width α is added or subtracted. Then, the upper and lower limits of the new tilt angle at that time are calculated. Within this range, the change in the amount of tilting of the variable displacement hydraulic pump 3 is limited, and the (
(The fluctuation range of ¥ is kept to a minimum.

Therefore, the hydraulic motor has good followability even when the operating lever 7 is slightly operated, and acceleration and deceleration can be achieved in the shortest possible time.

(Example〕 Hereinafter, the present invention will be explained in detail based on examples thereof.

The closed circuit hydraulic drive device 2 shown in FIG. 5 is now driven.

The configuration for controlling the closed circuit hydraulic drive device 2 will be described in order. A delay circuit 8 that transmits the movement of the operating lever 7 and makes the movement slow even if the operation is sudden; and a tilting amount limiting circuit 9 that limits the amount of tilting and suppresses the required music.
, a horsepower limiting circuit 10 that suppresses the operation of the variable displacement hydraulic pump 3, which discharges a predetermined amount Fd, depending on the operating room, within the output range of l'! A controller 12 drives and controls the step motor 11 based on a signal, a servo valve 13 whose functional position is switched by the step motor 11, and a hydraulic oil supplied through the servo valve 13 to change the tilt angle of the variable hydraulic pump 3. A servo cylinder 14 is provided. The tilt angle at that time is detected by the differential transformer 15, and feed hack control is performed so that the tilt angle becomes a predetermined tilt angle.

In such a device, pressure detectors 16A and 16B that detect pressures pt and P2 on the discharge side and suction side of the variable displacement hydraulic pump 3 are installed in the closed circuit 1, and the pressure signals are detected based on the pressure signals. The amount of tilting of the variable hydraulic pump 3 is electronically controlled. For this purpose, there is a pressure higher selection circuit 17, whereby the selected higher pressure is set within a predetermined range, with settings to be described later - upper limit value Pa and lower limit value pb.
If there is a maximum pressure limiting circuit 1 day that calculates the tilting angle reduction amount △θ that reduces the tilt angle at that time,
Maintaining the current tilt angle prevents the discharge pressure of the variable displacement i-1 hydraulic pump 3 from becoming too high than the maximum set pressure Pa. Note that horsepower is calculated by a horsepower calculation circuit 19 based on the detected pressure, and if it exceeds a limit range, it falls within a limit range of the horsepower control v circuit 10.

Furthermore, a rotation speed detector 20 is attached to detect the rotation speed of the hydraulic motor 4, so that it is possible to know how much rotation the load 5 with large inertia is rotating. Based on the detected value, a reference tilting angle calculation circuit 21 calculates the base tilting angle θ of the hydraulic pump 3, which is necessary for the displacement at any given time. A tilt angle change limit width setting device 22 that outputs a tilt angle change control V width α, and the tilt angle change limit width α
(by adding and subtracting the tilting angle θ to 4, i) variable displacement in the limiting circuit 9) of the hydraulic pump 3.
The L limit value (θ-α), <θ1-α) of ↓ is changed each time.

According to the closed-circuit hydraulic drive device 2 having such a configuration, the tilting angle of the variable eight minute hydraulic pump 3 is controlled in the following manner, and the hydraulic motor 4 is controlled while suppressing an excessive increase in its discharge pressure.
It is possible to improve the acceleration/deceleration of rotation.

Taking the operation lever 7 as an example, after the operation amount is converted into Δ/D through the delay circuit 8, the value of θ1-α is selected in the tilt M limit circuit 9 as the tilt angle commensurate with the required angle. , the step motor 11 is driven with a gain corresponding to the tilt angle based on whether the horsepower is within the limit. The spool moves, and the hydraulic oil from the hydraulic pump 23 is poured into the servo cylinder 14. (The rotation angle changes.) The rotation angle is fed back by the lance 15, and this continues until the set rotation angle θ + α is reached. It will be done. The discharge pressure I11 that falls at the (G1 rotation angle)
is detected, and the safety of horsepower is recognized by GAt. On the other hand, the opening pressure Pre (
Control is carried out so as not to generate a pressure exceeding the pressure (see FIG. 4). When the discharge pressure generated at the tilt angle at that time exceeds the limit value Pa (set (not shown in Fig. 2) which is slightly lower than the relief pressure Pre), the pressure is lowered.
Tilt angle reduction amount △θ to reduce the current tilt angle so that
is determined by the maximum pressure limiting circuit I8, and a corrected tilting angle signal (θ+α)−Δθ from which the tilting angle reduction amount Δθ is output is output to the ':1 controller 12. Since the tilting angle of the hydraulic pump 3 is reduced due to variable displacement, the discharge pressure is also reduced. If it decreases too much, the force for rotating the load 5 by the hydraulic motor 4 becomes weaker, and the discharge pressure drops to reach the set lower limit value pb. Since the pressure detected at point 11 is low, the tilting angle reduction amount Δθ calculated by 6u in the maximum pressure limiting circuit 18 becomes zero, and the tilting angle signal input to the controller 12 is θ+α. becomes. Therefore, the discharge pressure gradually rises, and the pressure that accelerates the fI load is as shown in the second line and the lower limit value 1).
h, and the hydraulic motor 4 is
'JsuJ pressure never exceeds the relief pressure Prc. In addition, at the initial stage until the discharge pressure reaches the set lower limit value Pb, the tilt angle decrease ¥-Δθ is zero.

On the other hand, the rotation speed of the hydraulic motor 4 is detected by the rotation speed detector 20 . Since the inertia of the load 5 is large, the rotation of the hydraulic motor 4 gradually increases as shown by line E.

For example, when the rotation of the load is low, even if the tilting angle of the variable displacement hydraulic pump 3 is increased to increase the displacement, the rotation of the hydraulic motor 4 will not increase accordingly due to the load with large inertia. . However, such an operation is wasteful and may cause the relief valve to open due to excessive discharge pressure.
There will be a loss of energy due to this. On the other hand, when the rotation speed increases to a certain extent, the oil amount is increased (and the rotation speed increases quickly. Therefore, in this example, the rotation state of the load 5 is grasped and the rotation speed at that point is increased. In other words, an appropriate rotation angle is calculated for the detected rotational speed, and this is calculated as the rotation angle θ by the rotation limit circuit 9. At the same time, in order to generate acceleration or deceleration pressure, the J1 (vehicle head roll angle θ) is added or subtracted by the tilt angle change limit width α preset in the tilt angle change limit width setting device 22. The tilting amount range is set in the tilting limit circuit 9, and i'I is set within the upper and lower limit range (θ-α) to (θ+α).
Hydraulic oil is discharged while the tilting angle change of the J variable displacement pressure port hydraulic pressure 3 is limited. Incidentally, initially, the rotational speed of the hl'' pressure motor 4 is zero, and the appropriate reference tilt angle is also zero. Therefore, in the tilting displacement +9rJ circuit 9, a tilting command is first given in the range up to the tilting angle α, and when the hydraulic motor 4 starts rotating, the appropriate standard tilting angle θ is determined from the rotation speed at that time. is calculated, and from then on (around ten yen is θ
The reference tilt angle θ of C1 is changed one after another.

When controlling the tilting angle of the 1iJ displacement pressure pump 3 in this way, the range of the tilting angle is gradually changed in accordance with the rotational speed of the current propensity.

7. As mentioned above, the tilt angle change for force control is within the limit range (θ−α) to (θ+α) at each time.
α), and therefore, the rotation angle of the variable displacement hydraulic pump 3 is wide (3') as shown in FIG.

Since the angle is turned around 1 and the a is adjusted based on the detection by the pressure detector 20, there is no possibility of a peak in the discharge pressure. As a result, the range of variation in the discharge pressure and tilting angle of the variable displacement hydraulic pump is reduced, no peak pressure occurs relative to the set pressure in a closed circuit, and unnecessary consumption of drive energy due to opening of the relief valve is avoided. can do. Moreover, it is possible to drive the hydraulic motor 4 according to the inertia of the load without rotating it, and the hydraulic motor 4 can better follow even minute operations of the control lever 7, allowing acceleration and deceleration of rotation to be performed in a short time. Realized.

(Effects of the Invention) I'f, as described in detail, the present invention detects the rotation speed of the hydraulic motor, and based on the detected value, the reference tilt angle of the hydraulic pump is determined from time to time. Calculate 1
To generate acceleration or deceleration pressure, add or subtract the tilt angle change limit width set in advance to the basic tilt angle, and change the tilt angle change of the hydraulic pump variable within the range of the upper and lower limits. By limiting the pressure and μJ during acceleration and deceleration, the electronic control allows the hydraulic motor to follow even the slightest operation of the operating lever. By minimizing the fluctuation range of the tilting of the variable displacement hydraulic pump, it is possible to create an energy-saving hydraulic closed circuit that does not generate peak pressure relative to the set pressure.

[Brief explanation of drawings]

Fig. 1 shows a closed-circuit hydraulic drive device to which the control method for a closed-circuit hydraulic drive device of the present invention is applied and its control configuration, and Fig. 2 shows changes in tilt angle, rotation speed, and acceleration pressure due to this control. The graph in Figure 3 is based on the pressure on the discharge side and suction side of the variable displacement U hydraulic pump. FIG. 4 is a graph showing a previous example of a closed-circuit hydraulic drive system for controlling the tilt angle Fa of a hydraulic pump, and shows how the tilt angle and the acceleration pressure change rapidly. 1 Hydraulic closed circuit, 3-variable capacity, hydraulic pump, 4-bending motor, 9-tilting amount limiting circuit, 16△, 16B-pressure detector, 18-maximum pressure limiting circuit, 20 rotation speed detector,
21 - Reference tilt angle calculation circuit, 22 Tilt angle change limit width setter, θ - Reference tilt angle, α - Tilt angle change side limit 1 fall △
θ - tilting angle reduction amount, Pa - maximum set pressure.

Claims (1)

[Claims] (1) Detect the pressure on the discharge side and suction side of the variable displacement hydraulic pump that operates the hydraulic motor installed in the hydraulic closed circuit,
In a method for controlling a closed-circuit hydraulic drive device that controls the amount of tilting of the variable displacement hydraulic pump based on the pressure, the rotation speed of the hydraulic motor is detected, and the rotation speed of the hydraulic motor is detected based on the detected value. Calculate the reference tilting angle of the hydraulic pump, add or subtract the preset tilting angle change limit width to the reference tilting angle to generate acceleration or deceleration pressure, and adjust the variable displacement within the range of the upper and lower limits. A method for controlling a closed-circuit hydraulic drive device, characterized in that the tilting angle of a hydraulic pump is changed, the range of pressure fluctuation during acceleration and deceleration is reduced, and the pressure is limited to a maximum set pressure or less.