JPS5812017A - Flow rate and pressure controller - Google Patents

Abstract

PURPOSE:To perform pressure control with high accuracy, good response and saving energy, by controlling a solenoid proportional type relief valve with an output signal from a pressure sensor and an output signal from an adding amplifier and making a pressure at the poststage of a throttle valve coincident with an objective pressure. CONSTITUTION:The part before and after a throttle valve 4 provided at a main line 3 of a variable pump 1 is connected to a pilot chamber and a spring chamber of a power matching valve 5 and the valve 5 is responded to the differential pressure before and after the valve 4. A delivery quantity controlling section 20 of the pump 1 is freely changed over to the line 3 and a tank 17 via the valve 5 to control the differential pressure before and after the valve 4 to a constant value. A by-pass line 32 branched from the line 3 at the poststage of the valve 4 to the tank is provided with a solenoid proportional type relief valve 33. The relief valve 35 is controlled with an output signal from a pressure sensor 34 detecting the pressure at the poststage of the valve 4 and an output signal from an adding amplifier 35 detecting a deviation with an objective signal representing the objective pressure, allowing to make the pressure at the poststage of the valve 4 coincident with the objective pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is particularly effective when used in, for example, an injection molding machine, which allows flow rate control and pressure control to be performed in an energy-saving manner, and pressure control to be performed with high precision and high response. The present invention relates to a flow rate/pressure control device.

In recent years, power matching type devices that match the discharge flow rate and discharge pressure of a variable pump to the load requirements are often used as flow rate/pressure control devices for injection molding machines, etc., in order to save energy. It became so.

This power matching type flow rate/pressure control device, for example, when controlling the flow rate when the injection cylinder is moving forward,
The pressures before and after the throttle valve provided in the main line connecting the variable pump and the injection cylinder are transmitted to the pilot chamber and spring chamber of the power match valve, respectively, and the power match valve is used to control the discharge amount of the variable pump. For example, by controlling the swash plate control cylinder 7-, the discharge amount is controlled so that the differential pressure across the throttle valve becomes constant, and unnecessary fluid is not discharged, resulting in an energy saving effect. In addition, during pressure control when the injection cylinder is stationary, such as during a pressure holding process, the pilot IJ valve, which is connected to the spring chamber of the power match valve and connected to the main line via a throttle, is operated. Then, the power match valve is operated to control the swash plate control cylinder, position the swash plate of the variable pump to the neutral side, and control the discharge amount of the variable pump to a state close to zero. This also has an energy saving effect.

In this way, the power matching type flow rate/pressure control device
Although it has an energy saving effect, since the pressure and flow rate are controlled by operating the swash plate of the variable pump, the swash plate control cylinder, etc., the high responsiveness required when manufacturing advanced molded products, for example. There was a drawback that it was not possible to obtain pressure control with high precision.

Therefore, an object of the present invention is to control the flow rate using a power matching method, maintain the energy saving effect, and control the pressure by using a variable pump, so that the swash plate and the swash plate control cylinder are hardly operated. Another object of the present invention is to provide a new flow rate/pressure control device that can eliminate the influence of a variable pump system and perform high-performance pressure control with high responsiveness and high accuracy.

Therefore, the present invention connects the front and rear of the throttle valve provided in the main line of the variable pump to the pilot chamber and spring chamber of the power match valve, respectively, and connects the power match valve to the front and rear of the throttle valve. The variable pump is adapted to respond to the differential pressure, and the discharge amount control section of the variable pump can be freely switched between the main line and the tank via the power match valve, so that the differential pressure before and after the throttle valve is controlled to be constant. In this flow rate control device, an electromagnetic proportional relief valve is provided in a bypass line branching from the main line downstream of the throttle valve to the tank, and the electromagnetic proportional relief valve is used to control the pressure downstream of the throttle valve. Control is performed using the output signal from the summing intensifier that calculates the deviation between the output signal from the pressure sensor to be detected and the target value signal representing the target pressure, and the pressure after the throttle valve is made to match the target pressure. It is characterized by the fact that

Hereinafter, the present invention will be described in detail with reference to embodiments of the illustrated injection molding machine.

In FIG. 1, 1 is a swash plate-type variable pump 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 cylinder, 4 is an electromagnetic proportional throttle valve as an example of a throttle valve provided in the main line 3, and 5 is a power match valve.

The above power match valve 5 has ports l and n at symbol position ■1.
・At symbol position ■2, ports m and n are communicated and port / is closed. The power match valve 5 has the spring pressure of the spring 12 in the spring chamber 11 set to ΔP, and when the differential pressure between the pilot chamber 13 and the spring chamber 11 becomes 12 or more, it is located at the symbol position v1, When the differential pressure becomes equal to or less than ΔP, the symbol is located at the symbol position (2). - Port j of the power match valve 5 is connected to the main line 3 which is located in front of the throttle valve 4 via the pilot line 15, and the pilot line 16 is connected to the port m.
While the tank 17 is connected to the port n via the pilot line 18, it is connected to the discharge amount control section 20 of the variable pump 1, such as a swash plate control cylinder. - The pilot chamber 13 and spring chamber 11 of the power match valve 5 have a pilot line 21 and a throttle 22, respectively.
The front and rear of the throttle valve 4 are connected via a pilot line 23 provided with a pilot line 23, so that the power match valve 5 responds to the differential pressure across the throttle valve 4.

Further, a pilot line 26 branched from between the spring chamber 11 and the throttle 22 of the power match valve 5 to the tank 25 is provided with a pi-lot relief valve 27.

On the other hand, an electromagnetic proportional +71
7- A valve 33 is provided. The above electromagnetic proportional relief valve 33
is the output signal from the summing intensifier 35 that calculates and outputs the deviation between the output signal from the pressure sensor 34 that detects the front pressure, which is the control pressure of the electromagnetic proportional relief valve 33, and the target value signal that represents the target pressure. .

Pressure feedback control is configured to match the target pressure and the control pressure by being controlled by the output signal.

The flow rate/pressure control device having the above configuration operates as follows.

Suppose now that the variable pump 1 is driven and the injection cylinder 2 is moved forward while controlling its speed with the aperture 4 to perform an injection stroke in which a mold (not shown) is filled with resin.

At this time, as shown in FIG. 2, the injection pressure, that is, the downstream pressure Pa of the throttle valve 4 increases as the resin is filled, but the pilot chamber 13 and spring chamber 11 of the power match valve 5 have no throttle. The pressure before and after the valve 4 is connected to the pilot line 21.
i3, the power matching valve 5 is located at the symbol position v1 or v2 as shown below according to the differential pressure before and after the throttle valve 4, and the power is controlled by the discharge amount control unit 20 of the variable pump 1. The discharge amount of the variable pump l is controlled so that the differential pressure across the throttle valve 4 is constant (ΔP I
if/d) Iζ. That is, 1,
Is the differential pressure before and after the throttle valve 4 ΔPK? /d or less, the power match valve 5 has a spring pressure of its spring 12 (ΔPK1i
1/d), it is located at the symbol position v2, and the baud)
n and m are communicated, the discharge amount control unit 20 is communicated with the tank 17, and the swash plate is inclined toward the maximum discharge side to increase the discharge amount. As a result, the differential pressure across the throttle valve 4 increases to ΔP Kf/cd. On the other hand, when the differential pressure across the throttle valve 4 becomes equal to or greater than ΔP Kf/d, the power match valve 5 is located at the symbol position v1, communicates between baud)/ and n, and the main The pressure of line 3 is transmitted to tilt the swash plate toward the minimum discharge flow rate to reduce the discharge volume. As a result, the differential pressure before and after the throttle valve 4 decreases to ΔP
Become KP/aJ.

In this way, this flow rate/pressure control device controls the discharge amount of the variable pump 1 to an amount that corresponds to the load requirement during flow rate control, and does not discharge excess fluid, so it is energy-saving. It is. It is assumed that in the above flow rate control state, the pilot valve 27 and the electromagnetic proportional relief valve 33 are completely closed.

Next, after filling the mold with resin is completed, the injection cylinder 2
When it comes to a standstill, the injection pressure increases rapidly, as shown by the curve on the right side of time t0 in FIG. 2, and the flow rate control state shifts to a pressure control device that requires almost no flow rate.

At this time, the opening degree of the throttle valve 4 is set to, for example, an electromagnetic proportional
- The flow is narrowed down to a level that allows approximately 1 to 10% of the rated flow rate of the valve 33 to flow, and a target value signal representing the target pressure is input to the addition amplifier 35, and pressure i control is performed as described below. Note that 27 functions as a safety valve, and is always in the relationship of "Pressure (very) Pressure (5)".

Now, if the electromagnetic proportional type relinif valve 33 is closed, the recycle fluid pressure will increase.

However, a target value signal representing a predetermined target primary pressure pb in FIG. A pressure signal representing the rear pressure of the throttle valve 4 is inputted, and a deviation signal between the pressure signal and the target value signal is inputted from the addition amplifier 35 to the electromagnetic proportional type IJ valve 3$. I will come. For this reason, the electromagnetic proportional IJ valve 33 operates so that the pressure downstream of the throttle valve 4, which is the control pressure detected by the pressure sensor 34, matches the target primary pressure Pb. In other words, the electromagnetic proportional relief valve 33 operates to the open side when (control pressure>target primary pressure);

(standard pressure), it moves to the closing side. In other words, the electromagnetic proportional relief valve 33, the additive amplifier 35, and the pressure sensor 3
4 performs pressure pack control. Also, at this time, the spring chamber 11 of the power match valve 5
Since the fluid pressure in the pilot chamber 13 is the above-mentioned primary pressure Pb, the pyro-relief valve 27 is completely closed, and the power match valve 5 is operated so that the pressure in the pilot chamber 13 is the above-mentioned primary pressure Pb.
The discharge amount of the variable pump 1 is controlled by operating so that the spring pressure ΔP is higher than that of the throttle valve 4, that is, the differential pressure across the throttle valve 4 becomes ΔP. In this state, the opening degree of the throttle valve 4 is set to an extent that does not interfere with pressure control, that is, as described above, the opening degree of the throttle valve 4 is set to 1 to 10 of the rated flow rate of the electromagnetic proportional type valve 33.
%, the variable pump 1 keeps the swash plate stationary on the neutral side and discharges a very small amount of fluid. This fluid flows through the throttle valve 4 and the electromagnetic proportional type IJ I
It is discharged into the tank 31 via the J-fu valve 33.

Next, when a signal representing the secondary pressure Pc in FIG. 2, which is lower than the primary pressure pb, is input to the addition amplification device 35, the addition amplification device 35 detects the pressure downstream of the throttle valve 4 detected by the pressure sensor 34. A signal representing the deviation between the pressure and the secondary pressure Pc is input to the electromagnetic proportional relief valve 33. Then, the electromagnetic proportional relief valve 33 opens in response to the signal representing the deviation, and
The pressure downstream of the throttle valve 4 is quickly and accurately controlled to the secondary pressure Pc. Note that at this time, the power match valve 5 is controlled to the throttle valve 4 as in the case where the primary pressure is controlled to PB.
The discharge amount of the variable pump 1 is controlled so that the differential pressure before and after is controlled to the spring pressure ΔP, and the pilot relief valve 27 is closed.

The pressure control performed as described above is achieved by narrowing down the throttle valve 4.
This is a valve control method using an electromagnetic proportional relief valve 33, an additive amplifier 35, and a pressure sensor, which eliminates the influence of a variable pump system that degrades pressure control accuracy and response.
Moreover, since it is pressure feedback control, it has the advantage of high pressure control accuracy and high pressure response. Also,
In the above pressure control state, the throttle valve 4 is of the electromagnetic proportional type f Sugi IJ
The flow is throttled so that only 1% to 10% of the rated flow rate of the IJ-F valve 33 can flow, and the variable pump 1 discharges an extremely small amount using the power match valve 5 so that the differential pressure across the throttle valve 4 becomes ΔP. Therefore, compared to the conventional pressure control method of valve control using a fixed pump and a relief valve, there is less surplus fluid and less power loss.

In the above embodiment, an electromagnetic proportional throttle valve is used as the throttle valve, but for example, a flow rate adjustment valve with pressure compensation or a proportional throttle switching valve may be used. Furthermore, the variable pump 1 of the above embodiment is of a type in which the discharge amount reaches the maximum value when the control fluid pressure acting on the discharge amount control section is the minimum value, but when the control fluid pressure is the minimum value, A variable pump of a type that has a minimum discharge amount and a maximum discharge flow rate when the control fluid pressure is at a maximum value may be used. In this case, as is well known, the symbol of the power match valve will be reversed from that of the above embodiment. Furthermore, in the above embodiment, the pressure was controlled by restricting the throttle valve 4; however,
It goes without saying that one pressure control can be performed even when the throttle valve 4 is fully open.

As is clear from the above description, the flow rate/pressure control device of the present invention connects the front and rear of the throttle valve provided in the main line of the variable pump to the pilot chamber and spring chamber of the power match valve, respectively. A match valve is made to respond to the differential pressure before and after the throttle valve, and the discharge amount control section of the variable pump is made freely switchable between the main line and the tank via the power match valve, so that the discharge amount of the variable pump is Since the differential pressure before and after the throttle valve is controlled to be constant, the flow rate and discharge pressure of the variable pump can be controlled according to the load requirements, and therefore there is no power loss and the flow rate is high in circuit efficiency. In addition to maintaining the advantage of controllability, an electromagnetic proportional relief valve is provided on a bypass line that branches from the main line downstream of the throttle valve to the tank, and the electromagnetic proportional relief valve is connected to the bypass line downstream of the throttle valve. The pressure after the throttle valve is controlled by the output signal from the summing amplifier that calculates the deviation between the output signal from the pressure sensor that detects the pressure at the end of the throttle valve and the target value signal that represents the target pressure. By adjusting the throttle valve to match the value of , it is possible to perform pressure control with high precision, good responsiveness, and energy saving. Therefore, the present invention is extremely effective when used in an injection molding machine that manufactures sophisticated molded products. Further, since the device of the present invention uses an electromagnetic proportional relief valve, it has the advantage that it is more resistant to hydraulic oil contamination and has higher reliability than devices that use conventional servo valves. In addition, the electrical circuit for pressure feedback of the device of this invention can be used as is from the conventional valve control method (fixed pump, relief valve method), so this device can be manufactured at low cost and quickly. has advantages.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a flow rate/pressure control device according to an embodiment of the present invention, and FIG. 2 is a graph showing the relationship between time and injection pressure of the device shown in FIG. 1...Variable pump, 3...Main line, 4...
Throttle valve, 5...Power match valve, 33...Electromagnetic proportional relief valve, 34...Pressure sensor, 35...Additional amplifier.

Claims (1)

[Claims] (1) The front and rear of the throttle valve (4) provided in the main line (3) of the variable pump (1) are connected to the pilot chamber and spring chamber of the power match valve (5), respectively, and the power match valve (5
) is made to respond to the differential pressure before and after the throttle valve (4), and the discharge amount control section (■) of the variable pump (1) is controlled between the main line (3) and the tank αη via the power match valve (5). In a flow control device that can be freely switched to control the differential pressure before and after the throttle valve (4) at a constant level, the main line (3) downstream of the throttle valve (4) is branched to a tank. Install a proportional electromagnetic relief valve c1 on the bypass line (branch)
34 is provided, and during pressure control, the electromagnetic proportional relief valve (to) is connected to an output signal from a pressure sensor that detects the pressure downstream of the throttle valve (4) and a target value signal representing the target pressure. Flow rate/pressure control characterized in that the pressure downstream of the throttle valve (4) is made to match the target pressure by controlling with an output signal from an addition amplifier (to) that calculates the deviation. Device.