JPH0418020Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention relates to an ultra-low pressure reducing circuit, and more specifically, to a method for reducing the minimum adjustment pressure to zero or an extremely low value in the vicinity of zero in a pilot-operated pressure reducing valve circuit. Regarding the ultra-low pressure reducing circuit that can be used.

[Prior Art] FIG. 4 shows an example in which the minimum adjustment pressure can be reduced using a conventional pressure reducing valve circuit. In FIG. 4, the main valve spool 404 is arranged to control the opening and closing of the flow path between the primary port 401 and the secondary port 402. A portion 416 is formed,
By colliding with the valve hole at the lower shoulder of this large diameter portion, the spring force of the main valve spring 405 causes the flow path control section 415 between the primary side and the secondary side to be in the normally open state in the installed state. It communicates with

Now, when the flow rate to the secondary side becomes zero, such as when the actuator is stopped, the main valve spool 404 operates to close the main control section 415 and rises against the main valve spring 405. Control unit 4 at this time
The opening degree of 15 is determined by the operation of the spool 404.
The pressure difference ΔP ₁ between the secondary pressure P ₂ acting on the lower surface of the spool large diameter portion 416 in the chamber 417 via the passage 418 in the spool and the pilot pressure controlled by the pilot valve 420 in the spring chamber 408, and the control The opening degree is maintained at a level sufficient to supply the flow rate determined by the size of the section 415, and in this state, the inflow flow rate from the primary side flows from the spool internal passage 418, through the throttle 414, through the pilot valve 420, and into the drain port 403. In this way, the secondary pressure is controlled.

Therefore, the minimum value P ₂ min of the secondary pressure when the actuator is stopped (when the secondary flow rate is zero) in this conventional pressure reducing valve circuit is at least equal to the secondary pressure P ₂ acting on the spool large diameter portion 416. Spring chamber 40
The pressure difference ΔP ₁ between the pilot pressure in the spool 418 and the pilot pressure in the spool from the primary side
20 and the pressure drop ΔP ₂ due to the flow path resistance of the series of outflow passages leading to the drain port 403, that is, P ₂ min=ΔP ₁ +ΔP ₂ (1). Here, the pressure receiving area of the large diameter part of the spool is A,
If the spring constant of the main valve spring 405 is k and its deflection amount is x, ΔP ₁ is ΔP ₁ =kx/A (2), and the spool pressure receiving area is increased by the large diameter portion 416. This reduces ΔP ₁ and therefore P ₂ min
In other words, it is made smaller. However, with such conventional pressure reducing valves, although it is possible to reduce the minimum value of the adjusted pressure value to a certain extent, the spool must be made large in diameter accordingly, and the dimensions of the large diameter part of the spool are limited. As a practical matter, it is impossible to reduce the minimum adjustment pressure from zero to zero or close to it, and it is usually about 1.8Kg/cm ²
In addition, the structure inevitably increases in size and complexity, and the flow rate override characteristic deteriorates as the pressure is set lower. Furthermore, in this conventional pressure reducing valve, the main control section 415 is of a so-called normally open type, so that the pressure oil flowing into the primary side at the start of valve operation instantaneously regulates the pressure until the spool starts pressure control. There is also the drawback that a jumping phenomenon occurs in which a flow rate greater than the amount flows to the secondary side.

Note that the normally closed type that does not cause this jumping phenomenon is, for example, the
Although this is disclosed in Japanese Patent No. 629 and is well known, it is impossible to make the minimum value of the minimum adjustment pressure at or near zero when the secondary skin flow rate is zero when the actuator is stopped. In other words, in the system disclosed in Japanese Patent Publication No. 45-629, oil leaking from the primary side when the actuator is stopped has no choice but to push open the check valve in the main valve piston and flow out from the pilot relief valve into the tank. The secondary pressure cannot be lower than the sum of the cracking pressure of the check valve and the pressure in the main valve spring chamber.

[Problems to be solved by the invention] The problem of the invention is to solve the problems of the prior art as described above, and to reduce the minimum adjustment pressure value of the outlet pressure to zero or To provide a pilot operated type ultra-low pressure reducing valve which can be set from a value extremely close to zero, can flow a sufficient flow rate at low pressure, and is less likely to cause the normally closed type jumping phenomenon.

[Means for Solving the Problems] According to the present invention, the secondary side pressure and the main valve spring are changed from one end surface side of the main valve spool to change the communication opening degree of pressure oil flow from the primary side to the secondary side. By applying the spring force and applying the pilot pressure set by the pilot pressure control valve from the other end side, the secondary pressure is controlled to be reduced according to the adjusted pressure value set by the pilot pressure control valve, and the pressure is reduced from the primary side. The ultra-low pressure reducing circuit is configured to drain excess pressure oil into a tank through a drain flow path, and the flow path control section from the primary side to the secondary side until the main valve spool starts pressure control operation. The main valve spool is normally closed, and in this closed state, the throttle means directly communicates the secondary side with the outlet of the drain flow path, and the pilot pressure is applied to the main valve spool from the other end side. There is provided an ultra-low pressure reducing circuit characterized by comprising a constant flow control valve that directly supplies a constant flow rate of pilot flow from the primary side to the pilot pressure control valve.

[Function] In the present invention, the main valve spool 4 blocks the flow between the primary side 1 and the secondary side 2 in the installed state, and at this time, the secondary side is connected to the drain port 3 through the throttles 18 and 11. It communicates with This restriction may be formed by having the flow control section 15 of the main valve spool 4 in an equivalent underlap configuration 18, or if the flow control section 15 is in an overlapping configuration, another fixed restriction 11 may be formed between the secondary port 2 and the drain port. It may be configured by providing between three spaces. On the other hand, the constant flow control valve 19 is
A constant flow rate of pilot flow is applied to the pilot pressure control valve 20, so that the pilot pressure acting on the main valve spring chamber 8 remains constant at the adjusted set point.
Thus, in the present invention, the flow path leading from the secondary side 2 to the drain flow path outlet 3 falls directly to the drain flow path outlet by the throttles 18 and 11, without passing through the pilot line.

When the flow rate required on the secondary side is zero (actuator stopped), the flow path control section of the main valve spool 4 is normally closed, so only the amount that leaks from the spool sliding gap etc. from the primary side to the secondary side. No, this is a very small amount. At the same time, since the secondary side communicates with the drain port 3 through the throttles 18 and 11, no pressure is generated on the secondary side, and an amount equivalent to the leakage amount flows out to the drain, reducing the secondary side pressure. It becomes zero.

The main valve spool 4 is displaced to a position where the pilot pressure applied to the main valve spring chamber 8 and the sum of the spring force of the main valve spring 5 and the secondary side pressure _P2 are balanced.

Therefore, when the secondary pressure P ₂ is zero, the pilot pressure P _V only needs to be equivalent to the spring force of the main valve spring 5, and if this pressure value is the minimum set value, the adjustment pressure The minimum value that can be set is zero. In addition, the spring force of the main valve spring 5 in this case can be determined so that the main valve spool 4 exhibits sufficient rigidity against the flow force acting on the main valve spool 4 in the required flow rate range. The override characteristic also extends to a sufficiently large flow rate, and the characteristic of large flow rate can be obtained at low pressure.

In the pressure reducing circuit of the present invention, the main valve spool normally closes the main flow path control section, so there is no risk of the occurrence of a jumping phenomenon, and the overall drain amount is also small.

[Example] Fig. 1 is a longitudinal sectional view showing a first embodiment of the present invention configured as a composite valve device, and Fig. 2 is an enlarged view of the main flow path control section surrounded by the arrow in Fig. 1. It is.

In FIG. 1, in the installed state, the main valve spool 4 cuts off the third annular groove 35 that communicates with the primary port 2, and the first annular groove 16 and the drain port 3.
The main valve spring 5 is slidably disposed within the valve hole penetrating each of these annular grooves so as to communicate with the second annular groove 17 which directly communicates with the second annular groove 17 at a predetermined opening degree. The upper part of the main valve spool 4 is a reduced diameter part, and a flat ring-shaped spring receiving flange 33 is fitted into the shoulder part 34 of this reduced diameter part, and is held at the tip of the spool to prevent it from coming off with a flange bolt 31. The main valve spring 5 is resiliently mounted between the spring receiver 32 and the spring receiver 32, and the main valve spool 4 is arranged as described above so as to leave a slight upward displacement stroke within the cylindrical portion of the spring receiver 32. It is configured to be in a state.

The details of the vicinity of the main flow path control section in the above-mentioned installed state of the main valve spool 4 are as shown in FIG. l ₁ is the overlap dimension between the through hole 14 and the second annular groove 17 constituting the equivalent underlap control section 18, l ₂ is the diameter of the hole 14, and L _S is the distance between the grooves 16 and 17. If L _B , l ₁ = l ₂ , L _S = L _B
An equivalent underlap configuration is obtained as follows. As a result, when the outflow flow rate from the secondary side port 2 is zero, the main valve spool 4 is adjusted so that the inflow flow rate due to leakage from the primary side to the secondary side and the outflow flow rate from the secondary side to the drain are equal to each other. is activated.

The constant flow control valve 19 directs a portion of the primary pressure oil of the primary port 1 introduced into the pressure chamber 29 via the flow path 28 from the spring chamber 30 through the through-throttle hole 12 of the spool 6 to the throttle control section. 13 through the flow path 21,
23, and a constant flow of pressure oil is supplied to the pilot pressure control valve 20. In this case, the spool 6 is displaced against the spring 7 to control the control part 13 so that the pressure difference across the fixed throttle 12 is constant. Control. The flow passages 21 and 23 also communicate with the main valve spring chamber 8 via the flow passage 22, and the pilot pressure set and regulated by the pilot pressure control valve 20 is applied to the upper end surface side of the main valve spool 4.

The pilot pressure control valve 20 receives a constant flow rate of pilot flow from the constant flow control valve 19.
The poppet valve body 9 seated on the seat 24, the spring 10 of the poppet valve body 9, and its pressure regulating screw 34
The pilot flow that pushes open the poppet valve body 9 flows out from the spring chamber 25 through a passage 26 to the drain port 3 through a large diameter drain passage 27.

Now, when pressure oil with a pressure P ₁ and a flow rate Q ₁ flows from the primary port 1, a part of it flows into the constant flow control valve 19.
The other part flows into the main flow path control section 15 by the main valve spool 4. By the way, since the main valve spool 4 cuts off the primary side and the secondary side in the attached state, the flow to the secondary side is an extremely small flow rate, which is only the amount of leakage from the sliding portion of the spool. Further, since the secondary side is directly connected to the drain port 3 by the control section 18, no pressure is built up, and therefore the pressure in the annular chamber 35 communicating with the secondary port 2 is zero.

On the other hand, as described above, the constant flow control valve 19 controls the output of the throttle control section 13 so that the pressure difference before and after the fixed throttle 12 is constant, and the constant flow rate q _c flows into the pilot valve 20. , the pressure P _V (pilot pressure) in the main valve spring chamber 8 is controlled to be constant at the set value.

As a result, the main valve spool 4 operates to a position where the balance between the pressure P _V in the spring chamber 8 and the sum of the spring force of the main valve spring 5 and the secondary side pressure P ₂ is balanced, and the secondary pressure _P2 becomes a pressure lower than the primary pressure _P1 .

When the flow rate from the secondary side port 2 to the actuator is not required, that is, when the actuator is stopped, the flow rate flowing from the primary side to the secondary side and the flow rate flowing out from the secondary side to the drain port are offset. It works like that.

The balance equation of the main valve spool 4 when the actuator is stopped is shown below.

P ₂・A _S +k (y ₀ +y)=P _V・A ₂ ∴P ₂ =P _V −k/A _S (y ₀ +y) ……(1) Here, P ₂ : Secondary pressure, P _V : Pressure in the spring chamber 8, A ₂ : Pressure-receiving cross-sectional area of the spool 4, k: Spring constant of the main valve spring 5, y ₀ : Initial deflection amount of the main valve spring 5, y: Deflection amount of the main valve spring 5 be.

From equation (1), the secondary pressure P ₂ becomes zero if P _V =k/A _S (y ₀ +y).

According to the present invention, the secondary pressure can be set to zero in the pressure reducing circuit shown in FIG. 1, so the secondary pressure can be set from zero according to equation (1). Also(1)
As is clear from the equation, the controllability of the pilot pressure P _V in the spring chamber 8 is unrelated to the minimum value of the secondary pressure P ₂ , and therefore it has the advantage of being extremely easy to design in practice. It turns out.

In FIG. 1, for example, when surge pressure arrives from the secondary port 2, the main valve spool 4 is displaced upward by the upward stroke margin given by the cylindrical spring receiver 32, and the surge pressure is annularly displaced. It also has the function of letting water escape from the groove 17 to the drain port 3, and has the effect of absorbing surges.

In FIG. 1, the hole 14 of the spool 4 serves as a throttle that connects the secondary side directly to the drain port.
An underlap control unit 18 between the annular groove 17 and the annular groove 17 is provided, but if the spool 4 has an overlapping configuration, a fixed throttle 11 is provided between the annular chamber 35 and the drain port 3 as shown by the broken line in the figure. You can also replace it with

Further, although the main valve spring 5 is arranged at the upper part in the example shown in FIG. 1, it may be arranged, for example, at the lower part of the spool on the side of the secondary port 2 with the same effect.

FIG. 3 shows another embodiment of the present invention, in which parts having the same effect or corresponding to those in FIG. 1 are given the same reference numerals. In this embodiment, the main flow path control section 1
5 is formed by the edge portion of the land of the main valve spool 4 instead of the hole 14 shown in FIG. 1, and since the other parts are not much different from those shown in FIG. 1, further explanation will be omitted.

[Effects of the invention] As described above, according to the invention, it is possible to set and regulate the secondary side pressure from zero or its vicinity regardless of the primary side pressure, and moreover, it is possible to flow a large flow rate at a low pressure. This provides an ultra-low pressure reducing circuit with good override characteristics and no jumping phenomenon, and has practical effects in low-pressure, high-speed actuator applications, such as when chucking thin-walled rings in the radial direction in machine tools. It is something to play.

[Brief explanation of drawings]

Fig. 1 is a vertical cross-sectional view showing a first embodiment of the present invention configured as a composite valve device, Fig. 2 is an enlarged view of the part surrounded by the arrow in Fig. A sectional view showing a composite valve device according to a second embodiment,
FIG. 4 is a sectional view showing a conventional example. 1...Primary port, 2...Secondary port, 3...
Drain port, 4... Main valve spool, 5... Main valve spring, 8... Main valve spring chamber, 11... Fixed throttle, 1
4... Spool wall through hole, 15... Main flow path control section, 16... First annular groove, 17... Second annular groove, 18... Underlap control section, 19... Constant flow control valve, 20... ...Pilot pressure control valve.

Claims (1)

[Scope of utility model registration request] The secondary side pressure and the spring force of the main valve spring 5 are applied from one end side of the main valve spool 4 that changes the communication opening degree of pressure oil flow from the primary side to the secondary side, and the pilot pressure is controlled from the other end side. By applying the pilot pressure set by the valve 20, the secondary side pressure is controlled to be reduced according to the adjusted pressure value set by the pilot pressure control valve 20, and excess pressure oil from the primary side is drained into the tank via the drain passage 3. The ultra-low pressure reducing circuit is configured to flow out to the main valve spool 4.
The flow path control unit 15 from the primary side to the secondary side is kept closed until the pressure control starts. In this closed state, the secondary side is directly connected to the drain flow path outlet 3. Constant flow control that directly supplies a constant flow rate of pilot flow from the primary side to the throttle means 18, 11 that communicate with each other and the pilot pressure control valve 20 that applies its pilot pressure to the main valve spool 4 from the other end surface side. An ultra-low pressure reducing circuit characterized by comprising a valve 19.