JPS5838134A - Apparatus for controlling speed of injection cylinder - Google Patents

Abstract

PURPOSE:To carry out the injection molding with less power loss, by providing a by-pass of a main line with a pilot valve for adjusting the discharge amount of a variable pump and a mechanism for controlling it. CONSTITUTION:The main line 3 is connected with the by-pass comprising a discharge amount controlling section 20, a pilot change-over valve 7, and a pilot chamber 13. The by-pass measures at a summing amplifier 31 an output signal from a detector 32 for detecting the real speed of an injection cylinder 2 and a signal representing an aimed speed, and its deviation signal is inputted into an electromagnetic proportional type relief valve 27, so that the pressure in the spring chamber 11 is controlled to adjust the discharge amount.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a speed control device for an injection cylinder of an injection molding machine.

In recent years, in order to save energy, power matching type speed control devices for the injection cylinders of injection molding machines have often been used, which match the discharge flow rate and discharge pressure of a variable pump to the load requirements. Became.

This power matching type speed control device controls the pressure before and after the electromagnetic proportional throttle valve installed in the main line connecting the variable pump and the injection cylinder, respectively, during flow rate control when the injection cylinder is moving forward. The power is transmitted to the pilot chamber and spring chamber of the pilot valve as a match valve, and the pilot valve controls the discharge amount control unit of the variable pump, such as the swash plate control cylinder, to create a differential pressure vessel before and after the electromagnetic proportional throttle valve. Since the discharge amount is controlled to be constant and wasteful fluid is not discharged, it has an energy saving effect.

However, as is well known, this power matching type speed control device controls the speed by adjusting the opening degree of a proportional throttle valve installed in the main line. When using feedback control, it is difficult to obtain stability under high response conditions, and
There was a drawback in that a power loss occurred due to the differential pressure generated in the proportional throttle valve.

Therefore, an object of the present invention is to eliminate the above-mentioned drawbacks, and to make it possible to control the speed of the injection cylinder without using a proportional throttle valve, that is, without providing a valve in the main line. The objective is to improve responsiveness and prevent power loss due to passage resistance.

In order to achieve the above object, the present invention connects an injection cylinder to a variable pump via a main line that is not provided with a valve for speed control, and connects a discharge amount control section of the variable pump to the main line valve. The pilot chamber of the pilot △, which can be freely switched and connected to the tank and the tank, is connected to the main line via a pilot line, while the spring chamber of the pilot valve is connected to the main line via a pilot line provided with a throttle, An electromagnetic proportional relief valve is provided in the pilot line branched from between the spring chamber and the throttle, and the output signal from the speed detector that detects the actual speed of the injection cylinder and the signal representing the target speed are added together. After processing the signal representing the deviation between the actual speed and the target speed, the signal is input to the electromagnetic proportional type IJ IJ-7 valve, and the electromagnetic proportional type relief valve controls the spring. The present invention is characterized in that the pressure in the chamber is controlled and the pilot valve is operated to control the discharge amount of the variable pump so that the actual speed matches the target speed.

Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments.

In FIG. 1, 1 is, for example, a variable pump with a slant i whose swash plate is biased by a spring in the direction of the maximum inclination angle so as to always discharge the maximum flow rate, and 2 is an injection pump connected to the variable pump 1 via a main line 3. The main line 3 of the cylinder is not provided with a valve for speed control, so that passage resistance due to the valve does not occur.

Further, 4 is a relief valve-like surge pressure absorption valve provided in a branch line 6 branching from the main line 3 to the tank 5, and 7 is a J-type pilot valve for controlling the discharge amount of the variable pump 1.

The pilot valve 7 above is at symbol position ■1 and ports l and n
At symbol position v2, ports m and n are communicated and port 4 is closed. The pilot valve 7 sets the spring pressure of the spring chamber 11 and spring 12 to ΔP, and when the differential pressure between the pilot chamber 13 and the spring chamber 11 becomes 82 or more, the pilot valve 7 is located at the symbol position v0. , when the differential pressure becomes less than ΔP, the symbol position ■2 is located.

The main line 3 is connected to the port l of the pilot valve 7 via the /s+' pilot line 15, and
Tank 1 is connected to port m via pilot line 16.
7, while pilot line 1 is connected to its port n.
8, a discharge amount control section 20 of the variable pump 1, such as a swash plate control cylinder, is connected.

The main line 3 is connected to the pilot chamber 13 of the pilot valve 7 via a pilot line 21, and the main line 3 is connected to the spring chamber 11 via a pilot line 23 provided with a throttle 22. In addition, an electromagnetic proportional type IJ IJ-
A spring valve 27 is provided so that the pressure in the spring chamber 11 can be controlled.

Therefore, the pilot valve 7 has the same dimensions as the fluid pressure in the pilot chamber 13 and the /NIL chamber 1 set as described above.
The pressure difference before and after the throttle 22, which is the difference between the fluid pressure of the main line 3 and the fluid pressure of the electromagnetic proportional relief valve 2.
The discharge amount of the variable pump 1 is controlled by being located at the symbol position v1 or v2 so that the differential pressure with respect to the set pressure of 7 becomes 7 inch pressure ΔP. That is, when the differential pressure before and after the throttle 22 becomes equal to or less than ΔP, the pilot valve 7 is located at the symbol position v2, communicates baud)n and m, and causes the discharge amount control unit 20 to communicate with the tank 17. Then, the swash plate is tilted toward the maximum discharge side to increase the discharge amount. As a result, the differential pressure before and after the throttle 22 increases to a spring pressure ΔP. On the other hand, when the differential pressure before and after the throttle 22 becomes equal to or higher than ΔP, the pilot valve 7 is located at the symbol position ■1, and communicates between and n at the port, and the main line 3 is connected to the discharge amount control unit 20.
This pressure is transmitted to tilt the swash plate toward the minimum discharge flow rate, thereby reducing the discharge volume. As a result, the differential pressure across the throttle 22 decreases to ΔP. As a result, the pressure in the main line 3 is always △P higher than the set pressure of the electromagnetic proportional relief valve 27.
It is designed to be controlled so that the

Further, the spring chamber 11 of the pilot valve 7 and the spring chamber 28 of the surge pressure absorption valve 4 are connected via a pilot line 29.

On the other hand, the addition amplifier 31 has the actual speed V of the injection cylinder 2.
The output signal from the speed detector 32 that detects the pressure 2 of the main line 3 and the output signal from the pressure sensor 33 that detects the pressure 2 of the main line 3 are input, and a signal indicating the outside of the target speed and the target pressure P are input. A signal representing .

The addition amplifier 31 controls the target speed V when controlling the speed of the injection cylinder 2. After processing, a signal representing the deviation between the actual speed V and the actual speed V is output to the electromagnetic proportional type IJ leaf valve 27, the set pressure of the electromagnetic proportional type relief valve 27 is controlled, and the variable pump 1 is controlled via the pilot valve 7. The discharge amount is controlled so that the actual speed V matches the target speed Vo. In other words, if the actual speed is smaller than the target speed,
The deviation is processed and the set pressure of the electromagnetic proportional relief valve 27 is set to the high pressure side, and accordingly, the pressure of the main line 3 is increased as described above to increase the actual speed. On the other hand, if the actual speed is larger than the target speed, the deviation is processed and the electromagnetic proportional type IJ IJ-
The set pressure of the valve 27 is set to the low pressure side to reduce the pressure in the main line 3 and reduce the actual speed. In this way, the actual speed ■ is made to match the target speed vo.

Further, the addition amplifier 31 maintains the target pressure P when controlling the pressure of the injection cylinder 2. After processing the signal representing the deviation between the detected pressure P of the main line 3 and the detected pressure P of the main line 3, the signal is output to the electromagnetic proportional type IJ leaf valve 27, and the set pressure of the electromagnetic proportional type relief valve 27 is controlled in exactly the same way as in the case of the above-mentioned excessive control. do,
The discharge amount of the variable pump 1 is controlled via the pilot valve 7 to achieve the target pressure P. The pressure P of the main line 3 is made to match the pressure P of the main line 3.

The injection cylinder speed control device configured as described above operates as follows.

Now, assume that the variable pump 1 is driven and the injection cylinder 2 is advanced while controlling its speed to perform an injection stroke in which a mold (not shown) is filled with resin.

At this time, the target speed signal is inputted to the addition amplifier 31, and the actual speed signal V of the injection cylinder 2 from the speed detector 32 is inputted thereto. The addition amplifier 31 processes the deviation signal between the target speed Vo and the actual speed V and then converts it into an electromagnetic proportional type crease.
5 input to valve 27.

The electromagnetic proportional relief valve 27 changes the set pressure to the high pressure side or the low pressure side depending on the above deviation. Therefore, when the target speed Vo is larger than the actual speed V, the set pressure of the electromagnetic proportional relief valve 27 changes to the high pressure side, and the pilot valve 7 is located at the symbol position @V2 side,
-Then, the discharge amount of the variable pump 1 increases, increasing the actual speed V and reaching the target speed V. Make the actual speed V match. Conversely, when the target speed vo is smaller than the actual speed V, the set pressure of the electromagnetic proportional relief valve 27 changes to the low pressure side, the pilot valve 7 is located at the symbol position ■1 side, and the discharge of the variable pump 1 is reduced. decrease the amount and decrease the actual speed V,
Make the actual speed match the target speed Vo.

The feed pack speed control is performed by the speed detector 32, addition amplifier 31, electromagnetic proportional relief valve 27, pilot valve 7, variable pump 1 and injection cylinder 2.
Since feedback control is not performed using a throttle valve provided in the main line as in the past, the response to the target speed is excellent. In addition, the discharge amount of the variable pump 1 is controlled according to the target speed of the injection cylinder, eliminating the discharge of excess fluid and reducing power loss. Since there is no passage resistance caused by the passage resistance. This injection cylinder speed control device is therefore extremely energy-saving.

Next, a pressure control state in which filling of the mold with resin is completed and the injection cylinder 2 is stationary will be described.

During this pressure control, the target pressure signal P is sent to the addition amplifier 61.
□ and the main line actual pressure signal P detected by the pressure sensor 33 are input. The addition amplifier 31 processes a deviation signal between the target pressure and the actual pressure and inputs it to the electromagnetic proportional relief valve 27 . The electromagnetic proportional relief valve 27 increases or decreases the set pressure in accordance with the deviation signal, and controls the discharge amount of the variable pump via the pilot valve 7 to achieve the target Pressure P. Make the actual pressure P match the actual pressure P. That is, the pressure sensor 33, the addition amplifier 31, the electromagnetic proportional relief valve 2, the pilot valve 7, and the variable pump 1 perform efficient feedback pressure control.

It should be noted that the surge pressure in the main line 3 that is likely to occur due to the delay in decreasing the pump discharge amount during the transition from the speed control to the pressure control can be absorbed by the surge pressure absorption valve 4. Note that even during speed control, this surge pressure absorption valve can compensate for the delay in decreasing the pump discharge amount.

In the above embodiment, the variable postp 1 has a discharge amount control section 2.
However, as shown in Figure 2, when the control fluid pressure acting on the control fluid is at its minimum value, the discharge amount is at its maximum value. ,
A variable pump 1a may be used that has a maximum discharge flow rate when the control fluid pressure is at its maximum value. In this case, as shown in FIG. 2, the symbol signal of the pilot valve 7a is opposite to that of the pilot valve 7 of the above embodiment. A variable pump white i bias piston may also be provided. In addition, depending on the sign of the deviation between the target speed and the actual speed, the electromagnetic proportional type I
Of course, the current value applied to the J IJ-7 valve can be configured to increase or decrease, or can be configured to decrease or increase.

As is clear from the above description, the injection cylinder speed control device of the present invention connects the injection cylinder to the variable pump via a main line that is not provided with a valve for speed control, and also A pilot chamber of a pilot valve whose control unit can be freely switched and connected to the main line and the tank is connected to the main line via a pilot line, and a spring chamber of the pilot valve is connected via a pilot line provided with a throttle. An electromagnetic proportional relief valve is provided in a pilot line connected to the main line and branched from between the spring chamber and the throttle, and an output signal from a speed detector that detects the actual speed of the injection cylinder and the target speed are A signal representing the difference between the actual speed and the target speed is inputted from the addition amplifier to an electromagnetic proportional relief valve after being processed. to control the pressure in the spring chamber and operate the pilot valve to control the discharge amount of the variable pump;
Since the actual speed above matches the target speed,
It is possible to obtain quick response to the target speed, to control the discharge amount of the variable pump according to the target speed, and because there is no passage resistance of the main line, power loss can be further reduced.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an injection cylinder speed control device according to an embodiment of the present invention, and FIG. 2 is a circuit diagram showing a modification of the variable pump portion. 1... Variable pump, 2... Injection cylinder, 3...
Main line...7...Pilot valve, 27...
Electromagnetic proportional relief valve, 31...additional amplifier, 32.
...Speed detector. Figure 1 2 Figure 2

Claims (1)

[Claims] (1) Connect the injection cylinder (2) to the variable pump (1) via a main line (3) that does not have a valve for speed control, and connect the discharge amount control section (■) of the variable pump (1). The pilot chamber (to) of the pilot switching valve (7), which can be freely switched and connected to the main line (3) and the tank 0η, is connected to the main line (3) via the pilot line.
On the other hand, the spring chamber circle of the pilot switching valve (7) is connected to the main line (3) via a pilot line provided with a throttle, and a pilot branched from between the spring chamber αυ and the throttle ■. Electromagnetic proportional relief valve on line■
and inputs the output signal from the speed detector (to) for detecting the actual speed of the injection cylinder (2) and the signal representing the target speed to the addition amplifier (9), and outputs the addition amplifier (9). A signal representing the deviation between the actual speed and the target speed is input from the spreader (2) to the electromagnetic proportional relief valve (5) after processing, and the electromagnetic proportional relief valve (5) adjusts the pressure in the spring chamber a1. The pilot switching valve (7) is controlled to operate the pilot switching valve (7) so that the discharge amount of the variable pump (1) is n*L and the actual speed matches the target speed. Cylinder speed control device.