JP2013257030A - Relief valve and compressor fitted with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve productivity while eliminating the need for adjustment work using an adjustment cap and keeping the operation accuracy of a relief valve high.SOLUTION: A relief valve includes: a cylindrical valve case 20 whose front end is attached to an air chamber of a compressor body; a valve body 22 arranged in the center hole 21 of the valve case; a spring means 23 for biasing the valve body in the closing direction; and a fixing cap 24 fixed to the rear end of the valve case. A pressure difference PD between the center hole and outside air is generated by making valve body operating pressure Pv lower than relief pressure P0 and forming an exhaust hole arranged in the fixing cap into a small hole like orifice whose diameter d is 2.0 mm or smaller. The relief pressure P0 is defined as the sum (PV+PD) of the valve body operating pressure Pv and the pressure difference PD.

Description

  The present invention is suitable for puncture emergency repairs in which a sealing agent and compressed air are sequentially fed into a punctured tire to perform puncture repairs urgently. The present invention relates to a relief valve with improved performance and a compressor to which the relief valve is attached.

  As a relief valve used in a compressor for puncture emergency repair, the one described in Patent Document 1 below is known. As shown in FIG. 6, the relief valve a includes a cylindrical valve case c whose front end is attached to an air chamber b1 of a compressor body b that generates compressed air. The valve case c is provided with an air inlet h1 leading to the air chamber b1 at the front end and a center hole h having an open rear end. In the fork center hole h, a valve body e that opens and closes the air inlet h1 and a spring means f that biases the valve body e toward the air inlet h1 are arranged, and the center hole An adjustment cap g having an exhaust hole g1 and screwed back and forth is attached to the rear end of h.

  When the relief valve a is assembled, the adjustment cap g is screwed back and forth to adjust the urging force of the spring means f so that the relief valve a is operated at a preset relief pressure. ing. The reason for this is that the separation / contact of the valve body e from the valve seat portion d1a of the air inlet h1 determines the relief pressure due to the structure. This separation / contact is determined by the shape of the rubber material e1 of the valve body e, This is because the deformation tends to cause variation, and therefore adjustment by the adjustment cap g is required.

  However, in order to perform the adjustment operation on the total number of relief valves a, a lot of time and labor are required, and there is a problem that productivity is remarkably lowered.

JP 2012-101450 A

  Accordingly, an object of the present invention is to provide a relief valve that eliminates the need for adjustment work using an adjustment cap, improves the productivity while ensuring high operation accuracy of the relief valve, and a compressor having the relief valve attached thereto.

In order to solve the above-mentioned problem, the invention of claim 1 of the present application is a relief valve that attaches to an air chamber of a compressor body and releases overpressure when the pressure of compressed air in the air chamber exceeds a relief pressure P0.
A valve case having a cylindrical shape with a front end attached to the air chamber, and having a center hole having an air inflow port leading to the air chamber at the front end and opening the rear end;
A valve body arranged in the central hole and opening and closing the air inlet;
Spring means arranged in the central hole and biasing the valve body toward the air inlet;
A fixing cap that is fixed to a rear end of the valve case and has an exhaust hole that conducts the center hole and the outside air;
In addition, the valve body operating pressure Pv that retracts the valve body to open the air inlet is smaller than the relief pressure P0,
In addition, by forming the exhaust hole as a small orifice having a diameter d of 2.0 mm or less, a pressure difference Pd is generated between the central hole and the outside air due to resistance when compressed air passes through the exhaust hole. As well as
The sum (Pv + Pd) of the valve body operating pressure Pv and the pressure difference Pd is the relief pressure P0.

  According to a second aspect of the present invention, the diameter d of the exhaust hole is set based on an exhaust flow rate of the compressor body, a relief pressure P0, and a valve body operating pressure Pv.

  According to a third aspect of the present invention, the exhaust hole has a length of 1 to 5 mm.

  A fourth aspect of the present invention is a compressor, wherein the relief valve according to any one of the first to third aspects is attached to an air chamber of the compressor body.

  As described above, the valve body can be operated at a pressure lower than the relief pressure P0 by setting the valve body operating pressure Pv to be lower than the relief pressure P0 instead of making the valve body operating pressure Pv coincide with the relief pressure P0. It is configured. On the other hand, the exhaust hole provided in the fixed cap is a small-hole orifice having a diameter d of 2.0 mm or less. A pressure difference Pd is generated between the case and the outside air.

  At this time, the pressure difference Pd functions as a force for closing the valve body. Therefore, when the pressure P in the air chamber is smaller than the sum (Pv + Pd) of the pressure, the valve body is closed to prevent the compressed air from flowing out from the relief valve. When the pressure P in the fork air chamber rises above the sum (Pv + Pd), the valve body opens to allow the compressed air to flow out, and the pressure P can be reduced. That is, it can function as a relief valve with a relief pressure P0 = (Pv + Pd).

  In such a relief valve, since the pressure difference Pd, that is, the relief pressure P0, can be determined by the diameter d of the exhaust hole, there is no need for adjustment work by screwing back and forth of the adjustment cap as in the prior art, and the operation accuracy of the relief valve is improved. Productivity can be improved while ensuring high.

It is a disassembled perspective view which shows an example of the compressor which attached the relief valve of this invention. It is a perspective view which shows the principal part of a compressor main body. It is sectional drawing which shows the principal part of a compressor main body. (A), (B) is sectional drawing which shows the valve closing state and valve opening state of a relief valve. It is a perspective view which shows an example of the use condition of a compressor. It is sectional drawing which shows the conventional relief valve.

Hereinafter, embodiments of the present invention will be described in detail.
As shown in FIG. 1, the compressor 1 of this embodiment includes a compressor body 3 having an air chamber 2 and a relief valve 4 that attaches to the air chamber 2 and releases the overpressure of the compressed air in the air chamber 2. Have.

  In this example, the case where the compressor 1 is a compressor for puncture repair as shown in FIG. 5, for example, is shown. Reference numeral 40 in the figure denotes a cap at the mouth of a bottle container 41 containing puncture repair liquid. 42 is a bottle unit to which 42 is attached. The cap 42 has an air inlet 42a for sending compressed air from the compressor 1 into the bottle container 41, and an outlet for sequentially taking out puncture repair liquid and compressed air from the bottle container 41 by feeding this compressed air. A portion 42b is provided. In this example, a case where the hose 43a and 43b are connected between the compressor 1 and the air intake port 42a and between the take-out port portion 42b and the tire T is exemplified. It can also be configured such that it can be directly connected to the air intake port portion 42a without passing through the hose 43a.

  Next, the compressor body 3 includes a motor M, a piston 5 connected to the motor M, and a cylinder 7 that forms a pump chamber 6 that compresses air between the piston 5 and these are housed. It is accommodated in the case 9 so as to be transported integrally.

  The storage case 9 is a flat, substantially rectangular parallelepiped box having a small height, and is formed to be disassembled into upper and lower case portions 9U and 9L. As the motor M, various commercially available DC motors that operate with a 12V DC power source of an automobile can be used. A power cord provided with a power plug 10 that can be connected to a cigarette lighter socket of an automobile is connected to the motor M via a power switch SW that is attached to the upper plate portion of the storage case 9.

  As shown in FIGS. 2 and 3, the piston 5 is connected to the motor M via a known crank mechanism 11 and is disposed in the pump chamber 6 so as to be capable of reciprocating. The piston 5 has an intake hole 12A extending through the piston 5 in the axial direction, and the intake hole 12A is closed from the pump chamber side with a spring property, such as rubber, synthetic resin, metal, etc. The intake valve 12 using the valve 12B such as an elastic body is formed.

  The cylinder 7 includes a cylindrical cylinder body 7A that forms the pump chamber 6 and a cylinder sub-portion 7B that is connected to an end of the cylinder body 7A and forms an air chamber 2 that receives compressed air from the pump chamber 6. Provide one. The pump chamber 6 and the air chamber 2 are electrically connected through a small hole 13. The small hole 13 is provided with a one-way valve (not shown) having a well-known structure for preventing the compressed air in the air chamber 2 from flowing back to the pump chamber 6 side.

  The air chamber 2 is provided with a relief valve 4 for releasing the overpressure when the pressure P of the compressed air in the air chamber 2 exceeds the relief pressure P0. In the air chamber 2 of this example, an air supply unit 14 that sends out the compressed air in the air chamber 2 to the bottle unit 40 side, and a connection unit 16 that is connected to a pressure gauge 15 that measures the pressure P of the compressed air. Are further connected.

  Next, as shown in FIG. 4A, the relief valve 4 includes a cylindrical valve case 20 whose front end is attached to the air chamber 2, and a valve disposed in a central hole 21 of the valve case 20. It comprises a body 22, spring means 23 for urging the valve body 22, and a fixed cap 24 fixed to the rear end of the valve case 20.

  Specifically, the valve case 20 of this example has a cylindrical shape that protrudes rearward from the cylinder sub-portion 7 </ b> B that forms the air chamber 2. The center hole 21 having an air inlet 25 communicating with the air chamber 2 at the front end and opening the rear end is disposed inside. The center hole 21 of the present example has a small-diameter first center hole portion 21A extending rearward from the air inlet 25, and the first center hole portion 21A via a tapered cone-shaped valve seat portion 21B. A large-diameter second center hole portion 21C that is concentrically connected. In this example, a large-diameter fixed cap attachment hole 21F is further provided on the rear side of the second center hole 21C via a step 21D.

  In this example, the valve body 22 is disposed in the second center hole portion 21C, and opens and closes the air inlet 25 by being separated from and contacting the valve seat portion 21B. The valve body 22 of the present example is in the form of a rubber plug formed entirely from a rubber elastic material, and is attached to the rear end of, for example, a convex curved head portion 22A that can come into close contact with the valve seat portion 21B. A cylindrical spring locking portion 22B that locks the front end portion of the means 23 is projected.

  The fixing cap 24 is fixed to the rear end of the valve case and includes an exhaust hole 27 that conducts the center hole 21 and the outside air 26. In this example, the fixing cap 24 is a columnar spring locking portion 24B that locks the rear end portion of the spring means 23 to the front end of a columnar base portion 24A that fits into the fixing cap mounting hole 21F. Is protruding. The fixing cap 24 of the fork example is positioned by coming into contact with the step 21D, and is firmly fixed by the caulking portion 20a at the rear end of the valve case 20 without being displaced.

  The fork means 23 is a coil spring in this example, and is arranged in the second center hole portion 21C and between the valve body 22 and the fixed cap 24, thereby allowing the valve body 22 to air flow. Energize towards the entrance 25.

  In the relief valve 4 of this embodiment, the valve body operating pressure Pv when the valve body 22 is retracted and the air inlet 25 is opened is set to be smaller than the relief pressure P0. In the fork relief valve 4, the exhaust hole 27 is formed as a small-hole orifice 30 having a diameter d of 2.0 mm or less. As a result, as shown in FIG. 4B, resistance is generated when the compressed air flowing in from the air inlet 25 passes through the exhaust hole 27, and the pressure difference Pd between the inside of the valve case 20 and the outside air 26 is generated. Can be generated. The sum (Pv + Pd) of the valve element operating pressure Pv and the pressure difference Pd is set as the relief pressure P0.

  Hereinafter, the case where the relief valve 4 having the relief pressure P0 of 350 kPa is formed will be described in detail.

First, consider a case where the valve body operating pressure Pv of the valve body 22 is set to a value smaller than the relief pressure P0, for example, 320 kPa. For example, when the pressure P of the compressed air is 320 kPa, the force F that pushes up the valve body 22 is expressed by the following formula (1). The symbol “Da” in the formula is the diameter of the pressure receiving surface on which the valve body 22 receives the pressure P. For example, when the diameter Da is 6 mm, F≈9.04N from Equation (1).
^{F = (π × Da 2/} 4) × 320 --- (1)

  Therefore, the valve body operating pressure Pv of the valve body 22 can be set to 320 kPa by using the spring means 23 in which the spring compression force in the valve closed state of FIG.

  Next, the sum (Pv + Pd) of the valve element operating pressure Pv and the pressure difference Pd becomes the relief pressure P0. In this example, since the relief pressure P0 = 350 kPa and the valve body operating pressure Pv = 320 kPa, the pressure difference Pd is 30 kpa. Then, the diameter d of the exhaust hole 27 for setting the pressure difference Pd to 30 kPa is obtained by the following calculation.

In the valve open state of FIG. 4B, the flow rate Q of the air flowing through the relief valve 4 is expressed by the following formula (2).
Q = C × A × √ (2 × Pd / ρ) --- (2)
Symbol in the formula C --- The outflow coefficient, which is approximately 0.7 ± 0.1.
A --- A cross-sectional area of the exhaust hole 27, is ^{A = π × d 2/4} ( unit ^{m 2).}
Pd --- The pressure difference from the outside air 26, which is set to 30 kPa (= 30 × 10 ³ Pa ⁾ in this example.
[rho --- a density of air (in kg / m ^3), the temperature 20 ° C., is 1.205kg / ^{m 3} when the outside air pressure.
When the relief valve 4 is used in the compressor 1 having an exhaust flow rate Q of 7 liters / minute (= 0.117 × 10 ⁻³ m ³ / sec),
A = Q / {C × √ (2 × Pd / ρ)}
≈ 0.117 × 10 ⁻³ /{0.7×√(2×30×10 ³ /1.205)
≈ 0.749 × 10 ⁻⁶ (unit m ² )
It becomes.

D = √ (4 × A / π)
≒ √ (4 × 0.749 × 10 ⁻⁶ /3.14)
≒ 0.98 × 10 ^-3 (unit: m)
Therefore, by setting the diameter d of the exhaust hole 27 to 0.98 mm and the valve body operating pressure Pv of the valve body 22 to 320 kPa, the relief pressure P0 of the relief valve 4 can be set in a compressor with an exhaust flow rate Q of 7 liters / min. It can be set to 350 kPa.

  In the relief valve 4 set in this way, when the internal pressure P of the air chamber 2 exceeds the valve body operating pressure Pv (for example, 320 kPa), the valve body 22 is temporarily opened, and the compressed air flows into the center hole 21. . At this time, when the diameter of the exhaust hole 27 is sufficiently large, the pressure difference ΔP between the pressure in the center hole 21 and the outside air is substantially 0, so the valve body 22 remains open. However, in the present invention, since the exhaust hole 27 forms a small-diameter orifice 30, a pressure difference ΔP is generated between the pressure in the center hole 21 and the outside air 26, and (Pv + ΔP)> P is established, and the valve element 22 is Closed instantly.

  Here, the compressed air remaining in the center hole 21 gradually flows out through the exhaust hole 27 and the pressure difference ΔP decreases. On the other hand, the internal pressure P of the air chamber 2 increases due to the operation of the pump, and when (ΔP + Pv) <P, the valve body 22 is temporarily opened and the compressed air flows into the center hole 21. Thus, the internal pressure P of the air chamber 2 increases while the opening / closing of the valve body 22 is repeated. When the internal pressure P of the air chamber 2 exceeds the relief pressure P0, ΔP = Pb, P> (Pv + ΔP), the valve body 22 is opened, and exhaust is performed until the internal pressure P reaches the relief pressure P0. The compressed air is discharged from the hole 27.

  In order to stably exhibit the function by the exhaust hole 27, it is preferable that the length L of the exhaust hole 27 is 1 to 5 mm. When the length L is less than 1 mm, the flow of exhaust becomes unstable. Conversely, when the length L exceeds 5 mm, the flow resistance increases, and in any case, the operation accuracy at the relief pressure tends to decrease.

  In the fork relief valve 4, if the valve element operating pressure Pv is too low, the number of times the valve element 22 is opened before reaching the relief pressure P 0 increases, so that the rate of pressure increase tends to decrease. The operating pressure Pv preferably has a difference (P0−Pv) from the relief pressure P0 of 50 kPa or less. If the difference (P0−Pv) is too small, the operation accuracy at the relief pressure P0 tends to be lowered. Therefore, the difference (P0−Pv) is preferably 10 kPa or more.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

In order to confirm the effect of the present invention, 100 relief valves having the structure shown in FIG. 4 were prototyped based on the following specifications, and the actual relief valves when the exhaust flow rate Q was attached to a compressor of 7 liters / min. The variation of the relief pressure P0 was measured.
<Common specifications>
Valve body operating pressure Pv by spring means: 320 kPa
Diameter of exhaust hole d: 0.98 mm
Length L of exhaust hole 27: 3 mm
Relief pressure P0 target value: 350 kPa

  The average value of the relief pressure P0 of each relief valve was 350.7 kPa and the standard deviation was 8.4 kPa, and it was confirmed that the operation accuracy of the relief valve could be ensured while eliminating the adjustment work at the time of manufacture.

DESCRIPTION OF SYMBOLS 1 Compressor 2 Air chamber 3 Compressor main body 4 Relief valve 20 Valve case 21 Center hole 22 Valve body 23 Spring means 24 Fixed cap 25 Air inlet 27 Exhaust hole 30 Orifice

Claims (4)

A relief valve that attaches to the air chamber of the compressor body and releases the overpressure when the pressure of the compressed air in the air chamber exceeds the relief pressure P0;
A valve case having a cylindrical shape with a front end attached to the air chamber, and having a center hole having an air inflow port leading to the air chamber at the front end and opening the rear end;
A valve body arranged in the central hole and opening and closing the air inlet;
Spring means arranged in the central hole and biasing the valve body toward the air inlet;
A fixing cap that is fixed to a rear end of the valve case and has an exhaust hole that conducts the center hole and the outside air;
In addition, the valve body operating pressure Pv that retracts the valve body to open the air inlet is smaller than the relief pressure P0,
In addition, by forming the exhaust hole as a small orifice having a diameter d of 2.0 mm or less, a pressure difference Pd is generated between the central hole and the outside air due to resistance when compressed air passes through the exhaust hole. As well as
The relief valve characterized in that the sum (Pv + Pd) of the valve element operating pressure Pv and the pressure difference Pd is the relief pressure P0.   The relief valve according to claim 1, wherein the diameter d of the exhaust hole is set based on an exhaust flow rate of the compressor body, a relief pressure P0, and a valve body operating pressure Pv.   The relief valve according to claim 1 or 2, wherein the exhaust hole has a length of 1 to 5 mm. The compressor which attached the relief valve in any one of Claims 1-3 to the air chamber of the compressor main body.

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