JPS6145102A - Method of controlling speed of hydraulic equipment - Google Patents

Abstract

PURPOSE:To eliminate useless time and reduce the frequency of occurrence of shock or vibration by varying the flow-rate by an arbitrarily set value every unit time set in advance, thereby controlling the equipment-speed stepwise until it becomes the target value. CONSTITUTION:Both a unit time t required for change-over and a controlled quantity of flow-rate K per unit time t are set at suitable constant values. As the time elapses, the flow-rate is controlled stepwise by the controlled quantity of flow-rate K so that the speed of the equipment can be controlled from the high speed side to the low speed side. With this contrivance, the time required for complete switching of the equipment-speed is not fixed, and, when the difference in speed is small, the speed control can be done in a short period, thereby eliminating the useless time. At the same time, since the flow-rate can be controlled by a small amount per each unit time, occurrence of shock or vibration caused by sudden change of pressure can be eliminated, thus enhancing the stop- accuracy of the equipment.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method of controlling the speed in a hydraulic system from high speed to low speed or from low speed to high speed.

(Prior Art) In a hydraulic system, the operating speed can be arbitrarily controlled depending on the purpose. In this case, if the speed is suddenly changed, shocks and vibrations will occur due to pressure changes in the circuit, so in the past, resistors and capacitors were used to avoid sudden pressure changes when changing the speed in steps. A time constant circuit was used to electrically control the output to the proportional valve to adjust the amount of oil, thereby lengthening the time required for switching, that is, the pressure rise and fall time, to alleviate shocks and the like.

(Problem to be solved by the invention) It is generally said that the shock and vibration mentioned above are greater as the flow rate changes and the pressure changes are higher. In a hydraulic system that transfers the mold at high speed and opens and closes the mold at low speed, there is a significant difference in the flow rate and pressure of the hydraulic oil used, and the above-mentioned time constant circuit is used to reduce the shock and vibration that occur during switching. What we did was by no means the best method in terms of improving work efficiency.

In other words, if the one using a time constant circuit is expressed as an equation, σk q(t)=Q(1-θ) Command Q: Difference between the target command value and the flow rate command at time t=θ〃C: Capacity of the capacitor R: is the constant of the resistance value, and as shown in Figure 4, in the CR type time constant circuit,
Due to the constant of OR, the time required to reach the target flow rate is fixed regardless of whether the flow rate difference is small Q1 or Q2 is large, and particularly when the flow rate difference is small, wasted time is required.

(Means for Solving the Problems) This invention was devised to eliminate the drawbacks of the above-mentioned conventional methods. It is an object of the present invention to provide a new speed control method that can perform speed control in a short period of time and can also reduce as much as possible the shocks that tend to occur when switching speeds.

The feature of the present invention for the above purpose is that when controlling the speed by adjusting the flow rate of pressure oil, the flow rate is increased or decreased by an arbitrary set value every preset unit time, and by repeating this, the speed is increased in stages until the target value is reached. The aim is to control the

(Example) Fig. 2 shows a mold clamping device of an injection molding machine.
is the mold clamping cylinder, 2 is the mold clamping ram, and the booster ram 3 is inside.
has. To close the mold 4 on the movable plate side attached to the tip of the mold clamping ram 2 and the mold 5 on the fixed plate side, first, pressurized oil is supplied into the booster ram 3 and the mold 4 is moved at high speed. death,
When the mold 4 reaches a predetermined position, the position is electrically detected by a detector, the amount of oil is decreased, and the speed is switched to a low speed.

However, in this invention, as shown in FIG. 1, K is appropriately set constant during the flow rate control in the unit time t during which switching is performed, and the flow rate is adjusted as time passes during the flow rate control. By performing stepwise control, the speed is controlled from the high speed side to the low speed side. During this flow rate control, in this embodiment, the pump discharge amount is set between 00 and 7.5 inches, and during this flow rate control, the supply flow rate decreases with K as the lower width, so the speed decreases.

Furthermore, in this case, the smaller K is during flow rate control, the more gradual the switching becomes, and the occurrence of shocks and vibrations decreases accordingly.

FIG. 3 shows an example of a circuit for automatically performing speed switching, in which a device 7 that gives a command signal to the proportional valve 6 and an adder/subtractor 8 are electrically connected, and the switch unit time is A time setting device 9 for setting t and a flow rate setting device 10 for setting K during flow rate control are electrically connected. Furthermore, adder/subtractor 8
Enter the target speed A in
is input as the current speed B, and as long as the target speed A and the current speed B match, the same speed is maintained.

Also, if the target speed A input to the adder/subtractor 8 is changed, a difference will occur between it and the current speed B, so the flow rate is controlled during each switching unit time t, and the flow rate is controlled during each switching unit time t, so that it matches the target value. controlled step by step.

Therefore, by setting the switching unit time t and the jump once during flow rate control, the speed will be automatically controlled while calculating the difference between the target speed and the current speed.

(Effects of the Invention) As described above, in the present invention, the time required for complete speed switching is no longer fixed as in the case where a conventional time constant is used, and when the speed difference is small, the time required to completely switch the speed is not fixed. Since the speed is controlled based on time, there is no need to waste time as in conventional methods, and since the flow rate is controlled in small increments per unit time, shocks and vibrations caused by sudden changes in pressure are extremely unlikely to occur. It has features such as being small and further improving stopping accuracy.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the speed control method of the present invention, Fig. 2 is a schematic sectional view of the mold clamping device, Fig. 3 is an explanatory diagram when speed control is performed electrically, and Fig. 4 is a conventional speed control method. FIG. 3 is an explanatory diagram of a control method. 1... Mold clamping cylinder, 2... Mold clamping ram, 3... Booster ram, 4, 5...
...Mold, 6...Proportional valve. Figure 2 Figure 3

Claims (1)

[Claims] When controlling the speed by adjusting the pressure oil flow rate, the flow rate is increased or decreased by an arbitrary set value at each preset unit time, and by repeating this, the speed is controlled step by step until the target value is reached. speed control method in hydraulic equipment.