JPH0512807Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a pressure control valve such as a relief valve used in a hydraulic circuit.

[Conventional technology]

Conventionally, as such a pressure control valve, there is one described, for example, on page 89 of "Introduction to Hydraulic Drive" (May 20, 1970, published by Corona Publishing).

FIG. 5 shows an example of the standard relief valve, in which a balance piston 4 is slidably provided in the body 1.
is pressed against the valve seat 1a by the spring 2 to urge it in the direction of closing the main flow path 3, and the pressure oil on the inlet side of the main flow path 3 is passed through the tanker (elongated small hole) 4a provided in the piston 4. The pressure on the inlet port 3a side of the main flow path 3 (primary side pressure) can be controlled by introducing the oil into the back pressure chamber 6 and adjusting the oil pressure with the pilot relief valve 5.

If this relief valve 10 is shown in a hydraulic circuit diagram, the sixth
It will look like the figure.

Figure 7 shows an example of a normally open type relief valve, in which the balance piston 4 is connected to the spring 8.
The main flow path 3 is biased in the direction of opening, and pilot oil is introduced into the pilot line 7 at a pressure higher than the sum of the primary side pressure of the main flow path 3 and the biasing force of the spring 8, This is guided to the back pressure chamber 6 via the flow rate adjustment valve 9 to press the balance piston 4 in the valve closing direction, and by adjusting the pilot oil pressure with the pilot relief valve 5, the primary side of the main flow path 3 is The pressure can now be controlled.

This relief valve 20 is shown in a hydraulic circuit as shown in FIG.

[Problems to be solved by the invention] However, these conventional pressure control valves have the following problems.

That is, in the standard relief valve shown in FIGS. 5 and 6, the spring 2 constantly urges the balance piston 4 in the valve closing direction, so the primary side pressure is controlled from 0 pressure. It is not possible.

In addition, with the normally open type relief valve shown in Figures 7 and 8, the main flow path opens when the pilot oil pressure is low, so the system requires that the primary side and tank side are normally closed. When used for this purpose, a separate switching valve must be installed to open and close the oil passage.

For example, FIG. 9 shows a hydraulic circuit when the standard relief valve 10 shown in FIGS. 5 and 6 is used in an injection molding machine.

In such an injection molding machine, during injection, the solenoid valve 19 is switched to the injection side, and the piston 18a from which the screw 18b of the cylinder 18 extends is advanced in the direction of arrow A to perform injection.

When measuring, the solenoid valve 19 is switched to the measuring side to operate the hydraulic motor 21, and the hydraulic pressure flowing out from the cylinder 18 is controlled by the relief valve 10, so that the back pressure during plasticization of the injection material (plastic) can be adjusted arbitrarily. Can be set to .

Thereafter, the solenoid valve 19 is returned to the neutral position shown, and then the solenoid valve 17 is energized to forcibly retract the screw 18b together with the piston 18a in the direction of arrow B.

Therefore, the return oil path LT to the tank is opened during forced retreat, the oil pressure is controlled from 0 during metering, and closed at other times.

However, the conventional standard relief valve 10 inserted here is a normally closed type.
Since it does not open with pressure, a separate solenoid switching valve 11 is required.
is provided, and during forced retreat, the return oil passage LT must be communicated with the tank without going through this relief valve 10 as shown in the figure, which increases costs.

Moreover, this relief valve 10 cannot be controlled unless the primary oil pressure is in the range of, for example, 3 to 35 kgf/cm ² , so the problem of not being able to continuously control the oil pressure below 3 kgf/cm ² during metering cannot be solved.

On the other hand, when the normally open type relief valve shown in Figs. 7 and 8 is used in a similar injection molding machine, the result will be as shown in Fig. 10, and in this case, the pressure will change from 0 kgf/cm ² during measurement. Although continuous control is possible, it is necessary to provide an electromagnetic switching valve 22 having a block position as shown in the figure in order to return and close the oil passage LT at the time of injection, etc., which again raises the problem of increased costs.

This invention aims to solve such problems.

[Means for solving problems]

Therefore, the pressure control valve according to this invention has a valve body that opens and closes the main flow path by sliding inside the body, a spring that biases the valve body in the valve closing direction, and a pilot line that supplies pilot pressure. In the pressure control valve, the pilot line is branched into two flow paths within the body, and the hydraulic pressure of one flow path is adjusted by a pilot relief valve via a flow rate adjustment valve to provide a pressure control valve for the valve body. A pressure control valve is provided which is connected to a back pressure chamber and whose other oil passage is connected to an oil chamber on the opposite side of the back pressure chamber with respect to the valve body via a pressure reducing valve.

[Effect]

According to the pressure control valve configured in this way, when oil pressure is not acting on the pilot line or the oil pressure is low, the valve body is closed by the biasing force of the spring housed in the body. position, the main flow path is closed.

In addition, when high pressure is acting on the pilot line, the flow rate is adjusted to a constant level via the flow rate adjustment valve, and the pilot oil pressure whose pressure is adjusted by the pilot relief valve and the biasing force of the spring mentioned above are combined with the valve pressure. The pilot hydraulic pressure, which is reduced through the pressure reducing valve, acts on the valve body in the valve closing direction, so the pilot oil pressure acts on the valve body in the valve closing direction by adjusting the pilot relief valve. By changing the oil pressure, the inlet side oil pressure (primary side pressure) of the main flow path can be controlled from 0 kgf/cm ² according to the adjusted oil pressure.

〔Example〕

Hereinafter, an embodiment of this invention will be described based on FIGS. 1 and 2.

FIG. 1 is a longitudinal sectional view of a pressure control valve showing an embodiment of this invention, and FIG. 2 is a hydraulic circuit diagram thereof.

First, to explain its structure, this pressure control valve 30 has a balance piston 14, which is a valve body that opens and closes between an inlet port 3a and an outlet port 3b of a main flow path 3 formed in the body 1, slid into the body 1. A flow rate regulating valve 9 is provided between the oil passage 7a and the oil passage 7b of the pilot line 7 in the body 1.
A pilot relief valve 5 for adjusting the oil pressure is provided at a position facing the oil passage 7b.

This oil passage 7b is communicated with the back pressure chamber 6 through an oil passage 7c.

In addition, the pilot oil flowing in from the connection port 7d to the pilot line 7 is guided to the oil chamber 1c via the oil path 7e of the pilot line branching from the oil path 7a and the pressure reducing valve 12 provided in the middle thereof. 1c is communicated with an outlet port 3b connected to the tank 13 from the oil passage 7g through an orifice 23.

The balance piston 14 slides within a spring chamber 1b formed in the body 1, and has a medium-diameter rear end sliding portion 14b having a spring receiving hole 14a formed inside.
and a large diameter piston portion 14 that slides within the back pressure chamber 6.
c, a poppet portion 14d that opens and closes the main flow path by coming into contact with and away from the valve seat 1a of the body 1, a narrow diameter portion 14e having a tapered portion following the poppet portion 14d, and a medium diameter front end sliding member that slides within the oil chamber 1c. A portion 14f is integrally formed, and an oil passage 14h communicating the spring chamber 1b and the outlet port 3b is formed therein.

The balance piston 14 is attached in the valve closing direction in which the lower edge 14d ₁ of the poppet portion 14d is pressed against the valve seat 1a by a spring 15 engaged between the spring receiving hole 14a and the body 1. Forced.

In addition, in this balance piston 14, the pressure receiving areas of the end surface 14b ₁ of the rear end sliding portion 14b, the upper end surface 14c ₁ and the lower end surface 14c ₂ of the piston portion 14c, and the end surface 14f ₁ of the front end sliding portion 14f are the same. It is formed like this.

The pilot relief valve 5 is constructed by a poppet 5a, a spring 5c biasing the poppet 5a in the direction of pressing the poppet against the seat portion 5b, and a threaded portion of the body 1 to rotate the handle portion in the direction of arrow C in FIG. It consists of an adjustment shaft part 5d that can move forward and backward.

The pressure reducing valve 12 is biased in the valve opening direction by a spring 12a, and adjusts the opening degree of the throttle 16 by moving the spool 12b, which has an oil passage 12c formed inside, thereby reducing the oil pressure in the oil passage 7e. The pressure is reduced and supplied to the oil chamber 1c to keep the pressure acting on the front end surface 14f ₁ of the balance piston 14 constant.

If this pressure control valve 30 is shown in a hydraulic circuit diagram, the second
It will look like the figure.

Next, the operation of this embodiment will be explained.

If pilot oil is not introduced into the connection port 7d to the pilot line 7, or if the pilot oil pressure is low even if it is introduced, the balance piston 14 is caused by the biasing force of the spring 15 to cause the poppet portion 14d to close to the valve seat. 1a, the main flow path 3 is closed.

In this case, the inlet oil pressure _P1 of the main flow path 3 acting on the lower end surface _14c2 of the piston portion 14c is the biasing force F/S of the spring 15 (cracking pressure:
Kgf/cm ² ), the balance piston 14 has a cracking pressure F/S of the spring 15.
The lower edge 14d ₁ separates from the valve seat 1a, the main flow path 3 opens, and pressure oil is relieved into the tank 13.

When high pressure is introduced into the pilot line 7,
The flow rate of the pilot oil passing through the oil passage 7a is adjusted to a constant level by a flow rate regulating valve 9, and the pilot oil is supplied to the back pressure chamber 6 through the oil passage 7c.

Then, the oil pressure is adjusted by the pilot relief valve 5, and the pilot oil pressure Pp acting on the upper end surface _14c1 of the piston portion 14c of the balance piston 14 is set.

This pilot oil pressure Pp acts on the balance piston 14 in the valve closing direction in addition to the urging force F/S of the spring 15.

On the other hand, the pilot oil that has branched and flowed into the oil path 7e side flows into the pressure reducing valve 12, and the spring 12a
The force that pushes the spool 12b to the left in the figure and the oil path 12
The spool 12b is positioned at a position where it is balanced with the hydraulic pressure pushing the spool 12b to the right through
The hydraulic pressure supplied to c is reduced to a constant pressure, and the pilot hydraulic pressure Pb is applied to the balance piston 14 in the valve opening direction.

In addition, the inlet side oil pressure (primary side pressure) _P1 of the main flow path 3 acts on the lower end surface _14c2 of the piston portion 14c of the balance piston 14, and this also acts on the balance piston 14 in the valve opening direction. .

Here, the end face 14b ₁ of the balance piston 14,
14f ₁ , the upper end surface 14c ₁ , and the lower end surface 14c ₂ have the same pressure receiving area in advance, so that the pilot oil pressure Pp acting in the direction of pressing the balance piston 14 toward the valve seat 1a and the cracking pressure F/ by the spring 15 are the same. S, pilot oil pressure Pb via a pressure reducing valve that acts in the direction of separating the balance piston 14 from the valve seat 1, and 1 of the main flow path 3.
The relationship between the next side pressure P ₁ is as shown in the following equation.

Pp+F/S= _P1 +Pb Therefore, the primary pressure _P1 is _P1 =(Pp+F/S)-Pb...(1).

Here, when there is a relationship of Pb≧Pp＋F/S,
Regardless of the magnitude of the primary pressure _P1 , no force in the valve closing direction acts on the balance piston 14, so
The valve opens, the inlet port 3a and the outlet port 3b communicate with each other, and the primary pressure _P1 becomes zero.

Also, when there is a relationship of Pp<Pp+F/S, 1
The next side pressure _P1 is the value shown in equation (1), and in equation (1), the pilot oil pressure Pp is the value shown by the pilot relief valve 5.
The pilot relief valve 5 can be changed by adjusting the adjusting shaft portion 5d of the pilot relief valve 5.
By adjusting the above, the primary side pressure P ₁ of the inlet port 3a can be smoothly adjusted from 0 kgf/cm ² .

In this embodiment, a case has been described in which the pressure-receiving areas of each end surface 14b ₁ , 14c ₁ , 14c ₂ , 14f ₁ of the balance piston 14 are made the same in advance, but the present invention is not limited to this, and the pressure-receiving area of each end surface is Similar effects can be obtained even if they are different.

FIG. 3 is a hydraulic circuit diagram showing an example in which the pressure control valve according to the invention is used in an injection molding machine similar to that shown in FIGS. 9 and 10. The same parts are given the same reference numerals, and their explanation will be omitted.

In this case, the primary pressure of the pressure control valve 30, that is, the oil pressure of the return oil path LT to the tank 13, is set to 0 kg.
Since it can be controlled continuously from f/cm ² , there is no need to provide an electromagnetic switching valve 11 or 22 like in the past, and by adjusting the pilot relief valve 5 to the maximum pressure or cutting off the pilot oil supply at the time of injection. The return oil passage LT is closed, and when the vehicle is forced to retreat, the pilot relief valve 5 is adjusted to the lowest pressure to open the return oil passage LT.

Furthermore, during measurement, the oil pressure flowing out from the cylinder 18 can be continuously adjusted from 0 kgf/cm ² .

FIG. 4 shows another embodiment in which the valve body of the pressure control valve according to this invention is a spool valve, and parts corresponding to those in FIG. 1 are given the same reference numerals.

In this pressure control valve, a spool 24 is slidably inserted into a sliding hole 1d formed in the body 1, and a spring 15 is engaged between the body 1 and a spring receiving hole 24a formed at one end of the spool 24. This urges the spool 24 in the valve closing direction (to the right in the figure).

This spool 24 has a land portion 24 having the same diameter.
b, 24c, 24d are integrally formed with a sliding portion 24e having a slightly smaller diameter at the right end in the figure, and a pilot relief valve ₅ is provided on the left end surface 24b1 of the land portion 24b facing the back pressure chamber 6. The pilot hydraulic pressure Pp whose pressure has been adjusted is applied to the end surface 24 of the sliding portion 24e.
The pilot oil pressure Pp, which is reduced to a constant pressure, is applied to e ₁ via a pressure reducing valve 12, respectively.

Further, inside the spool 24, there is an oil passage 24f that communicates the spring chamber 1b with the outlet port 3b,
Oil passage 24g that communicates the primary side pressure P ₁ and the oil chamber 1c ₁
is formed.

If pilot oil is not introduced into the pilot line 7, or if the oil pressure is low even if it is introduced, the spool 24 is urged to the right by the urging force of the spring 15, and the valve is closed as shown in the figure. position.

When high pressure pilot oil is introduced into the pilot line 7, by adjusting the pilot relief valve 5 and changing the pilot oil pressure Pp, the spool 24 moves left and right according to the pressure, and the spool 24 is closed. The biasing force F/S of the spring 15 acting in the direction and the pilot oil pressure Pb,
Oil chamber 1 that acts on the spool 24 in the valve opening direction
Pilot oil pressure Pb of c and primary side pressure of oil chamber 1c ₁
The spool 24 is positioned at a position where P ₁ (acting on the end surface 24e ₂ ) is balanced.

Thereby, the opening degree of the main flow path 3 can be adjusted, so that the primary side pressure P ₁ can be smoothly adjusted from 0 kgf/cm ² .

[Effect of idea]

As explained above, the pressure control valve of this invention provides the following effects.

(1) Set the pressure on the inlet side (primary side) of the pressure control valve to 0 kg.
It can be controlled more smoothly than f/cm ² .

(2) If no pilot oil pressure is introduced into the pilot line or if the pilot oil pressure is low, the main flow path is closed, eliminating the need to use a switching valve to open and close the hydraulic circuit.
This simplifies the circuit and reduces costs.

(3) When using a proportional electromagnetic relief valve in the pilot line, the conventional pressure control valve (Figure 7) requires a strong spring, and the spring sensitivity increases, resulting in a significant deterioration of the main flow rate-pressure characteristics. However, according to this invention, this can be dealt with simply by increasing the set pressure of the pressure reducing valve, so its characteristics will not deteriorate. It is also possible to control pressure at a large flow rate.

[Brief explanation of drawings]

Fig. 1 is a vertical cross-sectional view of a pressure control valve showing an embodiment of this invention, Fig. 2 is a hydraulic circuit diagram thereof, and Fig. 3 is an example of the pressure control valve according to this invention used in an injection molding machine. FIG. 4 is a vertical cross-sectional view of a pressure control valve showing another embodiment of this invention, and FIGS. 5 and 6 are vertical cross-sectional views of a conventional standard relief valve and its hydraulic circuit. Figures 7 and 8 are longitudinal cross-sectional views and hydraulic circuit diagrams of conventional normally open type pressure control valves, and Figure 9 is an example of the standard relief valve shown in Figure 5 used in an injection molding machine. Fig. 10 is a hydraulic circuit diagram showing an example in which the normally open type pressure control valve shown in Fig. 7 is applied to an injection molding machine. 1...Body, 3...Main flow path, 5...Pilot relief valve, 7...Pilot line, 9
...Flow rate adjustment valve, 12...Pressure reducing valve, 14...Balance piston (valve body), 15...Spring, 2
4...Spool (valve body).

Claims (1)

[Claims for Utility Model Registration] Inside the body 1, there is a valve element 14 that opens and closes the main flow path 3 by sliding, a spring 15 that biases the valve element 14 in the valve closing direction, and a pilot pressure is supplied. In the pressure control valve provided with a pilot line 7, the pilot line 7 is connected within the body 1.
One oil passage 7a is branched into two oil passages 7a and 7e.
, the pilot relief valve 5 via the flow rate adjustment valve 9
The hydraulic pressure is adjusted by connecting the back pressure chamber 6 to the valve body 14, and the other oil passage 7e is connected to the pressure reducing valve 1.
2, the pressure control valve is connected to an oil chamber 1c on the opposite side of the back pressure chamber 6 with respect to the valve body 14.