JPS5813202A - Flow control device with pressure compensation - Google Patents

Abstract

PURPOSE:To decrease loss of energy by controlling the difference of pressure definitely between front position of pressure decreasing type pressure compensation valve and rear position of throttle valve by the operation of the load sensing valve in a flowrate controlling device with compensation of pressure for an injection molding machine, etc. CONSTITUTION:A pressure decreasing type pressure compensation valve 14 is arranged to control the difference of pressure definitely in the front & rear of the throttle valve 15 of a flowrate controlling device with compensation of pressure. A load sensing valve 21 is connected with a pilot chamber 33 in a front position of the pressure compensation valve 14. The difference of pressure between the front position of the pressure decreasing type pressure compensation valve 14 and the rear position of throttle valve 15 is definitely controlled by operation of the load sensing valve 21. Thus the precise compensation of pressure is performed by making the difference of pressure in the front & rear positions of the throttle valve 15 definite and decreasing loss of energy.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power matching type pressure-compensated flow rate control device that is particularly suitable for use in, for example, an injection molding machine and has improved pressure compensation accuracy and responsiveness.

In recent years, for example, flow control devices for injection molding machines, etc.
In order to save energy, variable pumps of the power matching type, which match the discharge flow rate and discharge pressure to the load requirements, have come into widespread use.

For example, during flow control when the injection cylinder is moving forward, this power matching type flow control device adjusts the pressure before and after the throttle valve installed in the main line connecting the variable pump and the injection cylinder, respectively. The information is transmitted to the pilot chamber and spring chamber of the sensing valve, and the load sensing valve controls the discharge amount controller of the variable pump, such as the swash plate control cylinder, to adjust the discharge amount so that the differential pressure before and after the throttle valve is constant. It has an energy-saving effect because it controls the flow rate and prevents wasteful fluid from being discharged.

However, since the conventional flow rate control device described above controls the flow rate by operating the swash plate of the variable pump, the swash plate control '-7 ring, etc., as is well known, pressure compensation accuracy and response are poor. This has the disadvantage that it cannot be used, for example, in injection molding machines that produce sophisticated molded products.

Therefore, the purpose of this invention is to provide a new pressure-compensated flow rate control device that uses a power matching method to control the flow rate and has high pressure compensation accuracy and high responsiveness while maintaining the energy-saving effect. .

For this reason, the present invention connects the front and back of a throttle valve provided in the main line connected to the variable pump to a pilot chamber and a spring chamber of a load sensing valve, respectively, so that the discharge of the variable pump is controlled via the load sensing valve. A flow rate control device with pressure compensation, in which the amount control unit is switchable between the main line and the tank, and the discharge amount of the variable pump is controlled to control the differential pressure across the throttle valve to a constant level, A pressure reduction and expansion pressure compensation valve is installed in the main line before the throttle valve to keep the differential pressure before and after the throttle valve constant. Pressure reducing type △ The differential pressure between the front side of the pressure compensation valve and the rear side of the throttle valve is controlled to be constant, and the differential pressure across the throttle valve is controlled to be constant using the valve control method using the pressure reducing expansion pressure compensation valve. It is characterized by the fact that

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

In FIG. 1, 11 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 12 is connected to the outlet of the variable pump 11 via a main line 13. For example, an actuator consisting of an injection cylinder, 14.15 a decompression expansion pressure compensating valve and a throttle valve provided sequentially from the upstream side in the main line 13, 21 a load sensing valve consisting of a 3-port switching valve, and 22 the load sensing mentioned above. A pressure control pilot valve 23 has the same structure as the valve, and 23 is a relief valve-shaped surge pressure provided in a branch line 25 that connects the main line 13 and tank 24 between the decompression expansion pressure compensation valve 14 and the throttle valve 15. It is an absorption valve.

The load sensing valve 21 communicates between ports l and n and closes port m at symbol position ■1, while it communicates between ports m and n and closes port t at symbol position ■2. There is.

This load sensing valve 21 is connected to its spring chamber 31.
The spring pressure of the spring 32 is set to ΔPL1, and when the differential pressure between the pilot chamber 33 and the spring chamber 31 becomes ΔP or more, the symbol position ■ is located, and when the differential pressure above the mouth becomes ΔP or less, the symbol position ■It is located at 21. The spring pressure of the spring 35 in the spring chamber 34 of the pressure control pilot valve 22 is set to ΔPP.

The port 1 of the load sensing valve 21 is connected via a pilot line 41 to the main line 13 which is located in front of the decompression expansion pressure compensation valve 14, and the pilot line 42 is connected to the port m of the tank 43 above the valve. On the other hand, the port m of the pressure control pilot valve 22 is connected to the port n via the pilot line 44. A discharge amount control section 46 consisting of, for example, a swash plate control cylinder of the variable pump 11 is connected to port n of the pressure control pilot valve 22 via a pilot line 45, while a pressure reduction and expansion control section 46 is connected to the port l via a pilot line 47. Connect the main line 13 in front of the pressure compensation valve 3.

The pilot chamber 33 of the load sensing valve 21 is connected to the front side of the decompression expansion pressure compensation valve 14 via a pilot line 48, while the spring chamber 33 of the load sensing valve 21
is connected to the rear of the throttle valve 15 via a pilot line 49. The pilot line 49 is connected to the front side of the decompression and expansion pressure compensating valve 14 via a pilot line 52 provided with a feed-in throttle 51, so that the load sensing valve 21 can respond quickly.

Pilot chamber 36 of the pressure control pilot valve 22
is connected to the pressure reducing type pressure compensating valve 14 via the pilot line 53.
On the other hand, the spring chamber 34 of the pressure control pilot valve 22 is connected to the tank 56 via a pilot line 54 provided with an electromagnetic proportional pilot relief valve 55. Pilot line 5 between the spring chamber 34 of the pressure control pilot valve 22 and the pilot relief valve 55
4 is connected to the front side of the decompression expansion pressure compensation valve 14 via a pilot line 58 having a feed-in throttle 57,
A vent flow rate for operating the pressure control pilot valve 22 is obtained. Further, the spring chamber of the surge pressure absorption valve 23 is connected to the line 54 between the spring chamber 34 of the pressure control pilot valve 22 and the pilot relief valve 55 via a pilot line 71.

The spring chamber 61 of the decompression and expansion pressure compensating valve 14 is connected to the rear end of the throttle valve 15 via a pilot line 62. The spring pressure of the spring 63 in the spring chamber 61 is set to ΔPo, and the differential pressure across the throttle valve 15 is controlled to ΔP.

Further, the spring pressure ΔPLI of the load sensing 21, the spring pressure ΔPR of the spring in the spring chamber of the surge pressure absorption valve, the spring pressure ΔPP of the pressure control pilot valve 22, the spring pressure ΔP6 of the pressure reducing type pressure compensating valve 14, ΔPc<ΔPL1, ΔPP〈Δ
PR relationship, for example ΔPL1=ΔPR=8Ky/cd
, ΔPP−ΔpG=5Kf/′cJ.

The pressure-compensated flow rate control device configured as described above operates as follows.

It is now assumed that this flow rate control device with pressure compensation is in a flow rate control state in which the actuator 12 is in motion.

At this time, the outlet pressure of the variable pump 11 is below the set pressure of the pilot relief valve 55, and the pilot relief valve 55 remains closed, so the pilot chamber 36 and spring chamber 34 of the pressure control pilot valve 22 are , the pressure in front of the pressure reduction/expansion pressure compensation valve 14 is transmitted via the pilot line 53 and the feed-in pilot line 58, respectively.

Therefore, the pressure control pilot valve 22 has a spring pressure ΔP,
Therefore, the symbol is located at the symbol position v2. At this time, the pressure in front of the decompression and expansion pressure compensation valve 14 is transmitted to the pilot chamber 33 of the load sensing valve 21 via the pilot line 48, while the pilot line 49 is transmitted to the spring chamber 31 of the load sensing valve 21. The pressure behind the throttle valve 15 is transmitted via it. Therefore, when the pressure difference between the pilot chamber 33 and the spring chamber 31 is less than the spring pressure Δptt, the load sensing valve 21 is located at the symbol position line 45, the pressure control pilot valve 22, the pilot line 44, and the tank 4 via the pilot line 42.
3, and the swash plate of the variable pump 11 is inclined toward the maximum discharge side to increase the discharge amount. At this time, it should be noted that there is a response delay in the swash plate. On the other hand, when the differential pressure between the pilot chamber 33 and the spring chamber 31 exceeds the spring pressure ΔPLI, the load sensing valve 21 is located at the symbol position It communicates with the main line 13 in front of the pressure reduction and expansion pressure compensation valve 14 via the pressure control pilot valve 22, the pilot line 44, and the pilot line 41,
Fluid pressure is applied to the discharge amount control section 46 to tilt the swash plate of the variable pump 11 toward the neutral direction, thereby making the discharge amount tend to decrease. In this way, the load sensing valve 21 controls the discharge amount of the variable pump 11 so that the differential pressure between the front side of the pressure reducing/pressure compensating valve 14 and the rear side of the throttle valve 15 matches the spring pressure ΔPL1. do. In other words, the variable pump 11 is configured such that the pressure in front of the pressure reducing type pressure compensation valve 14 is higher than the pressure in the rear part of the throttle valve L5 by the spring pressure ΔPLI of the load sensing valve 21 (depending on the opening degree of the throttle valve 15). The discharge amount is controlled by the power matching type flow rate control, which has a large energy-saving effect.

Also, at this time, the decompression and expansion pressure compensation valve 14
1 through the pilot line 62, the differential pressure across the throttle valve 15 (7) is controlled to spring pressure, ΔPG (6 to 9/ad). In this way, the pressure compensation for the throttle valve 15 performed by the valve control method using the decompression/expansion pressure compensation valve 14 is more accurate than the simple power matching method. In addition, the responsiveness of the output flow rate when the opening degree of the throttle valve 15 is suddenly decreased is determined by the responsiveness of the decompression expansion pressure compensation valve 14, and the variable pump system (variable pump 11, load sensing valve 21 etc.), which is very good. Therefore, overrun of the injection cylinder 12 can be prevented. This pressure-compensated flow control device retains the energy-saving advantages of the power matching control method (variable pump control method), and uses a valve control method that is highly accurate and highly responsive in the direction of decreasing output flow rate. It has the following advantages.

Next, the pressure control state, that is, the state in which the injection cylinder is stopped after completing filling and only the pressure is controlled, with almost no flow rate required, will be explained.

When the injection cylinder 12 is disused and the flow rate control state shifts to the pressure control state, the pressure in the pilot line 54 between the pilot relief valve 55 and the feed-in restrictor 7 is 55, the pressure is controlled to the set pressure.At this time, the pressure control pilot valve 22 is controlled so that the pressure difference between the pressure in the pilot chamber 36 and the pressure in the spring chamber 34 which is the set pressure is equal to the spring pressure ΔP.
It is located at symbol position ■1 or ■2 so that P, and is regularly located at the symbol position between ■□ and V2.

Therefore, the discharge amount control section 46 of the variable pump 11 is connected to the main line 13 via the pilot lines 45, 47, 53, and the variable pump 11 suddenly positions the swash plate toward the neutral side. The pressure of the main line 13 is controlled to a set pressure with an extremely small discharge amount. Therefore, there is less power loss on the circuit. Note 1. During the transition period from the speed control area to the pressure control area, the flow rate decreases rapidly, but there is a delay in the operation of the swash plate, which causes surge pressure (pressure overshoot) on main lines 1" and 3. This is caused by the surge absorption valve 23.
It can be absorbed by kudzu. In addition, if the transition from flow rate control to pressure control is slow during the initial transition, the load sensing valve 21 adjusts the differential pressure between the front side of the decompression expansion pressure compensation valve 14 and the rear side of the throttle valve 15 by a spring difference. Pressure Δ
Since the flow rate control circuit can be controlled to achieve PLI, the pressure override characteristic seen from the cylinder side of this flow rate control circuit is good.

In other words, even if the load pressure increases and a small amount of flow passes through the pilot relief valve 55, the differential pressure is kept constant and accurate flow control is performed until the pressure control pilot valve 22 is activated. be.

The modification shown in FIG. 2 differs from the above embodiment mainly in the following points. That is, the pilot valve 21 for pressure control shown in FIG. 1 is removed, and the pilot relief valve 55 is connected to the spring chamber 31 of the load sensing valve 21 as shown in FIG. In addition to serving as a pilot valve, the pressure reduction and expansion pressure compensation valve 14 is also used as a pilot relief valve 55 during pressure control.
The point is that the valve is operated in cooperation with the valve, and together they form a so-called balanced piston type pressure reducing valve. Further, as other embodiments for controlling the variable pump 11, there are control circuits shown in FIGS. 5 and 4. In this case, the circuit configuration other than those shown in the drawings is completely the same as in FIG. Nothing changes. That is, since the configuration of the variable pump is different, the pressure control pilot valve 22a10 and the sensing valve 21a are different from each other in FIG.
It is configured as shown in Fig. 4, and Fig. 3 - OK.

The variable pump lla is configured so that when the control pressure acting on the discharge amount control section 46a is at the maximum value, the discharge amount is the maximum, and when the control pressure is at the minimum value, the discharge amount is the minimum. On the other hand, the variable pump 11b in FIG. 4 is a variable pump llb equipped with a discharge amount control section 461 having a piston that constantly applies a discharge pressure to the small area side A15 and applies a control pressure to the large area side 4A2, The relationship between control pressure and discharge amount is the same as that shown in FIG. 3.

In addition, the term throttle valve here includes a proportional throttle switching valve. It is a concept that

As is clear from the above description, the flow rate control device with pressure compensation of the present invention connects the front and rear of the throttle valve provided in the main line connected to the variable pump to the pilot chamber and spring chamber of the load sensing valve, respectively. The discharge amount control section of the variable pump can be freely switched between the main line and the tank via the load sensing valve to control the discharge amount of the variable pump and equalize the differential pressure across the throttle valve. Furthermore, a pressure reduction and expansion pressure compensating valve is provided in the main line upstream of the throttle valve to keep the differential pressure before and after the throttle valve constant. Since the differential pressure is controlled to be constant, energy loss can be reduced using the power matching method, and highly accurate pressure compensation can be obtained using the pressure reduction and expansion pressure compensation valve'1' In addition, the responsiveness of the output flow rate of the throttle valve at the time of flow reduction t is determined by the pressure reduction/swelling pressure compensating valve and is not affected by the variable pump system, so it has advantages such as being quick. Therefore, the pressure-compensated flow rate control device of the present invention is extremely effective when used in automatic machines such as injection devices of plastic injection molding machines that require high efficiency, high precision, and high response.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a flow rate control device with pressure compensation according to an embodiment of the present invention, FIG. 2 is a circuit diagram of a modified example, and FIGS.
Each figure is a circuit diagram of a modified example of the variable pump portion. 11... Variable pump, 14... Decompression expansion pressure compensation valve,
15... Throttle valve, 21... Load sensing valve, 3
1...Spring chamber, 33...Pilot chamber, 46...
Discharge amount control section. Patent applicant: Daikin Industries, Ltd. Agent: Patent attorney, Tamotsu Aoshiro, and 2 others-11, Figure 2, Figure 3, Figure 4, Figure 10

Claims (1)

[Claims] (1) The throttle valve (151) installed in the main line connected to the variable pump (Ill)
21) is connected to the pilot chamber (to) and the spring chamber C311, and the discharge amount control section (lead can be freely switched between the main line and the tank) of the variable pump (11) via the load sensing valve (21). In the flow control device with pressure compensation, which controls the discharge amount of the variable pump (111) to keep the differential pressure before and after the throttle valve (151 constant), A pressure reducing type pressure compensating valve for controlling the differential pressure before and after the throttle valve (151) to a constant level is installed in the main line of the throttle valve (151), and a pressure reducing type pressure compensating valve ring is installed in the pilot chamber of the load sensing valve (21) in front of the pressure reducing type pressure compensating valve OI. The load sensing valve (21) is operated so that the differential pressure between the front side of the pressure reducing type pressure compensating valve α and the rear side of the throttle valve a9 is controlled to be constant. A flow control device with pressure compensation used for injection cylinders, etc., characterized by the following.