JPH0716594B2 - Gas mixing equipment - Google Patents

Description

TECHNICAL FIELD The present invention relates to a gas mixing device.

[Conventional technology]

For example, in a blood gas analyzer, it is necessary to continuously produce two or more kinds of aqueous solutions of known carbon dioxide and oxygen partial pressure as calibration standard solutions inside the apparatus.

For that purpose, there is a gas mixing device, for example, those shown in FIGS. 4 and 5 are known (USP. No.
See 3,464,434).

In FIG. 4, carbon dioxide 405 is a pressure control valve 411 and a resistance tube.
It is adapted to be introduced into the discharge pipe 414 via the 416 and the resistance pipe 401. On the other hand, the air 406 composed of oxygen and nitrogen is discharged through the pressure control valve 421 with pilot and the resistance pipe 402 to the exhaust pipe.
It will be introduced in 414.

The details of the pressure control valve 421 with pilot are shown in FIG.
The discharge pipe 426 from 6 is guided to the chamber passed by the membrane 423, and when the pressure of the air 406 becomes larger, the pressure corresponding to the pressure increased from the relief port due to the displacement of the membrane 423 becomes larger. The air 406 is designed to be discharged.

An indicator 420 is provided between the conduit that has passed through the pilot-equipped pressure control valve 421 and the conduit on the side of the carbon dioxide gas 405 to confirm that the respective differential pressures are 0 (the above technique is used). Known example A).

As another technique, those shown in FIGS. 6 and 7 are known (see Japanese Patent Laid-Open No. 63-111462). Although it is basically the same as that in FIG. 4 described above, the pressure reducing valve 313 is used instead of the relief type pilot-equipped pressure control valve 421 (the above technique is referred to as a known example B).

Further, as another technique, for example, there is a technique disclosed in Japanese Utility Model Publication No. 63-8420, which is referred to as a signal generator 203 as shown in FIG. It is a constant ratio type pressure reducing valve with drawers and diaphragms 252 and 256, which generates a reduced signal pressure from one gas supply pipe 264, and uses this as pilot pressure 234, which is a pressure regulating valve consisting of two pressure reducing valves dedicated to two gases. The device 202 is used. A bleed diaphragm 266 is used to prevent the signal pressure 265 to the pressure adjusting device 202 from becoming higher than necessary (the above technique is referred to as a known example C).

[Problems to be Solved by the Invention]

However, in the conventional example described above, in the known example A, firstly, the carbon dioxide gas in the cylinder (about 6370 KP
The vapor pressure of a is liquefied), and it is necessary to reduce the pressure within 1% of stability to about 9.8 KPa by the pressure reducing valve 411 and the resistance tube 416 shown in FIGS. There is a problem that a pressure reducing valve must be manufactured. Further, the air has to be supplied in an amount larger than that required to obtain the mixed gas, and the capacity of the centrifugal blower and the filter for removing dust in the air has to be increased accordingly. In addition, the membrane 42 is used to operate even with a slight differential pressure.
Considering the rigidity of 3, the area of the membrane 423 had to be considerably increased. More air pressure
When 426 became lower than carbon dioxide pressure 422, it completely lost its function.

Further, in the known example B, the pressure reducing valve 313 shown in FIGS. 6 and 7 has the force of the spring 341 even if the bellows 336 has no rigidity (which cannot be ignored in practice). Since it is not a specific pressure reducing valve, pilot pressure 31
0 must be higher than the secondary pressure (the inlet pressure of circuit 314). That is, the pressures at the branch points 305 and 315 are not equal, which makes the design and manufacture of the capillary resistance tubes 306, 307, 316, 317 very difficult.

Further, in the known example C, the stability of the mixing ratio with respect to the change in the flow rate is excellent, but this is rather due to the adjustment of the bleed-off amount of the bleed throttle 266. The structure is a combination of one relief type constant pressure reducing valve with a pilot (signal generator 203) and two relief type constant pressure reducing valves with a pilot (pressure regulator 202). This inevitably meant that the structure was more complicated than the previous two cases.

Therefore, the present invention has been made in view of such circumstances, and an object of the present invention is to provide a gas mixing device that solves the above-mentioned problems despite the extremely simple configuration.

[Means for Solving the Problems]

In order to achieve such an object, the present invention provides a non-pressurizable spring element that uses a pressure regulating element upstream of a capillary resistance tube as a pilot pressure and provides a deficient force. At least one relief type constant differential pressure reducing valve is provided in the other flow path, and its secondary pressure is made equal to the pilot pressure or equal to the secondary pressure of the pressure reducing valve that determines the pilot pressure. This is achieved by compensating for the deficiency in the spring element so as to equalize the inlet pressures of the elements that define the gas flow rate of

That is, according to the present invention, on the one hand, the carbon dioxide gas is passed through the pressure reducing valve and the constant flow rate generating element, and on the other hand, the air pressure is different from the pressure reducing valve and the other pressure reducing valve and the constant flow rate generating element. In a gas mixing device that obtains a mixed gas via a constant flow rate generating element, one of the pressure reducing valves is a non-relief type constant difference type pressure reducing valve, and the other pressure reducing valve has a constant flow rate generating element inlet side. The secondary pressure is basically the pilot pressure of the non-relief type constant difference type pressure reducing valve.

[Action]

In this way, the pressure reducing valve used as the constant pressure generating element generally exerts a fluctuation of 1 to 3% of the fluctuation of the primary pressure on the secondary pressure. Providing a relief port to this pressure reducing valve improves it to 0.3 to 1%. However, the amount of gas that bleeds off from the relief port is wasted, that is, wasted in vain, so there is a problem in terms of economy. Therefore, in the present invention, let the pressure of the gas having the most stable pressure at the inlet of the constant flow generation amount be the pilot pressure, and suppress the change in the secondary pressure of the pressure reducing valve of the other gas without the relief port. It is what is said. Therefore, even if the pilot pressure fluctuates ± 5% of the design value, for example, the secondary pressures of other gases also fluctuate by ± 5% in synchronization with the fluctuation of the pilot pressure, and the flow rates of both gases are also designed. Although it fluctuates by ± 5% of the value, since it is synchronized in this case, the flow rate ratio, that is, the composition of the mixed gas does not change. Further, since the inlet pressures of the constant flow rate elements of the respective gases are the same (because the outlet pressures are originally unchanged and are bidirectional), the design of the constant flow rate elements becomes very simple with respect to the composition of the mixed gas. Since this pilot pressure is not specifically generated, the structure is extremely simple.

〔Example〕

An embodiment of the gas mixing device according to the present invention will be described below.

In FIG. 1, there is a first gas source 11 made of liquefied carbon dioxide gas in a cylinder, for example, and the gas from this gas source 11 is supplied to a pressure reducing valve 12 serving as a constant pressure generating element. The secondary pressure side of the pressure reducing valve 12 is connected via branch points 13 to capillary resistance tubes 14 and 15 which are constant flow rate generating elements, and reach outlets 17 and 27.

On the other hand, the second gas source 21 including, for example, an air compression pump
The gas from the gas source 21 is supplied to the non-relief type differential pressure reducing valve 28. The constant pressure reducing valve 28 is connected to the secondary pressure side of the pressure reducing valve 12 via a conduit 19, and the pressure on the secondary pressure side is supplied to the constant pressure reducing valve 28 as a pilot pressure. . The secondary pressure side of the constant pressure reducing valve 28 is connected to the capillary resistance tubes 24 and 25, which are constant flow rate generating elements, respectively via a branch point 23, and a branch point 16 provided on the downstream side of the capillary resistance tubes 14 and 15 is connected. The discharge ports 17 and 27 are reached via the and 26.

Next, the detailed structure of the non-relief type constant pressure reducing valve 28 will be described with reference to FIG. In the figure, the valve body
The valve body 50 is provided with a primary pressure port 51 on the side surface and a secondary pressure port 52 on the bottom surface. The secondary pressure port 52 is connected to the conduit 53 via a foreign matter removing filter 55. In the figure, 54 is a sealing ball. On the other hand, the primary pressure port 51 is also connected to the guide path 56 via the foreign matter removing filter 55. The conduit 56 is connected to a hole 57 located approximately in the center of the valve body 50, in which a compression spring 58, a valve seat 59 located above the compression spring 58, and a spherical valve.
60 are arranged. A transmission rod 61 is attached to the spherical valve 60, and the transmission rod 61 is attached so as to penetrate the valve housing 63. The valve housing 63 is a valve seat
A guide port 52 and a guide 64 communicating with the valve seat 65 are provided. A metal bellows 68 is arranged on the upper portion of the valve housing 63, and is fixed to the valve body 50 at a flange 67 provided on the lower portion. A cup 69 having a fixed upper end is arranged in the metal bellows 68.
69 is positioned inside the guide 64 and can slide as the metal bellows 68 expands and contracts.

A bonnet 74 fixed to the valve body 50 is provided so as to cover the metal bellows 68, and a pilot hole 75 is provided on the side surface of the bonnet 74. A seat 70 is arranged at the bottom of the cup 69, and a compression spring 71 is inserted into the upper part of the cup 70, and the other end of the compression spring 71 is locked by a piston 72 with a spring seat. The spring seat piston 72 can slide on the bonnet 74 in an airtight state.
You can do it at Thereby, the spring 71 and the bellows 68 are compressed via the piston 72, the transmission rod 61 is pushed down, and the opening degree of the valve seat 65 and the spherical valve 60 is made constant, and the secondary pressure is set. It is designed to be fixed with a lock nut 77.

Next, the operation of the gas mixing device configured as described above will be described first.
This will be described with reference to the drawings and FIG.

Assuming that the ambient temperature is 23 ± 5 ° C and the pressure of the gas source 11 is 196 ±.
If the secondary pressure setting value of the pressure reducing valve 12 is 9.8 KPa and 19.6 KPa,
The pressure at branch point 13 is approximately 19.6 ± 0.98 KPa.
The pressure of the gas source 21 is 49 ± 9.8 KPa, and the secondary pressure setting value of the pressure reducing valve 28 (when the pilot pressure is 19.6 KPa)
Is 19.6KPa. As shown in FIG. 3, 49 ±
9.8 KPa and 19.6 ± 0.98 KPa are applied to the pilot hole 71. If these pressures are 0 and the secondary pressure is set to 0, the spherical valve 60 seals the valve seat 65, the transmission rod 61 and the cup 69 are slightly separated, and Bellows 68 and spring 71 must be of free length. Here, the effective area of the valve is A ₁ , the effective pressure receiving area of the bellows 68 is A ₂ , the spring constant of the spring 58 is k ₁ , the compression spring constant of the bellows 68 is k ₂ , and the spring constant of the spring 71 is k ₃ Assuming that the primary pressure is P ₁ , the secondary pressure is P ₂ , the pilot pressure is P ₀ , and the valve opening is x, the following equation is satisfied when the above pressures are balanced.

_{A 1 (P 1 -P 2)} + k 1 x + P 2 A 2 + k 2 x = P 0 A 0 + k 3 (x + α) ...
(1) Here, α is a surplus compression margin of the spring 71 for establishing the balance. For simplification, A ₁ (P ₁ −P ₂ ) and k ₁ x are very small, so if omitted, P ₂ A ₂ + k ₂ x = P ₀ A ₀ + k ₃ (x + α) (2) Now, if x increases by Δx for some reason and D ₂ increases by ΔP ₂ and tries to return to the original state, Has become. That is, the smaller k ₃ is, the smaller the increase of ΔP ₂ is. However, if k ₃ is reduced from the equation (2), the amount of α must be increased, which makes the design of the spring 71 difficult.
In equation (2), there is a term of P ₀ A _{2 on} the right side (that is, with a pilot), so it is possible to design to reduce k ₃ .
The above is the advantage of the circuit itself, that is, the secondary pressure fluctuation of the pressure reducing valve 28. Then, when the P ₀ is increased △ P _0, x is △ x increases, and the P ₂ has increased △ P _2, That is, the valve moves slightly to reach equilibrium. This means that the pressures at the branch points 13 and 23 are synchronized and fluctuate in the range of 19.6 ± 0.98KPa, and the relation of P ₀ = P _{2 is} always maintained.

FIG. 2 is a block diagram showing another embodiment of the gas mixing apparatus according to the present invention. The same reference numerals as those in FIG. 1 use the same members. The structure different from that of FIG. 1 is that a constant pressure reducing valve 18 is used in place of the pressure reducing valve 12, and its pilot pressure is set to the other constant pressure reducing valve.
The secondary pressure of 28 is taken out, and the secondary pressure of each constant differential pressure reducing valve is mutually made into another pilot pressure by this.

Even in such a case, extremely stable secondary pressure synchronism is exhibited.

〔The invention's effect〕

As is clear from the above description, according to the present invention, the pressure reducing valve used as the constant pressure generating element generally exerts a fluctuation of 1 to 3% of the fluctuation of the primary pressure on the secondary pressure. 0.3-1% if a relief port is provided on this pressure reducing valve
To improve it. However, this is a waste of the amount of gas bleeding out from the relief port, that is, it is abandoned in vain, so there is a problem in terms of economy.
Therefore, in the present invention, the gas having the most stable pressure at the inlet of the constant flow generation amount element is used as the pilot pressure,
It is intended to suppress the change in the secondary pressure of the pressure reducing valve for other gases without using the relief port. Therefore, even if the pilot pressure fluctuates by ± 5% of the design value, for example, the secondary pressures of the other gases also fluctuate by ± 5% in synchronization with the fluctuation of the pilot, and the flow rates of both gases are also the design values. ±
Although it fluctuates by 5%, since it is synchronized in this case, the flow ratio, that is, the composition of the mixed gas does not change. Also, since the inlet pressure of each gas constant flow element is the same (because the outlet pressure is originally unchanged and bidirectionally the same),
The constant flow rate element can be easily designed for the composition of the mixed gas. Since this pilot pressure is not specifically generated, the structure is extremely simple.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a gas mixing apparatus according to the present invention, FIG. 2 is a block diagram showing another embodiment, and FIG.
FIG. 4 is a configuration diagram showing an embodiment of a non-relief type constant difference type pressure reducing valve, FIG. 4 is a configuration diagram showing an example of a conventional gas mixing device, and FIG. 5 is a pressure control valve with pilot in FIG. FIG. 6 is a block diagram showing an example of a conventional gas mixing device, FIG. 7 is a block diagram showing a pressure reducing valve in FIG. 6, and FIG. 8 is a structure showing an example of a conventional gas mixing device. It is a figure. 11 …… first gas source, 12 …… pressure reducing valve, 13,23,16,26 …… branch point, 14,15,24,25 …… capillary resistance tube, 19 …… conduit, 21 …… second Gas source, 28 …… Non-relief type constant pressure reducing valve.

Claims (4)

[Claims] 1. A carbon dioxide gas is passed through a pressure reducing valve and a constant flow rate generating element on the one hand, while air is passed through another pressure reducing valve different from the pressure reducing valve and another constant flow rate generating element being different from the constant flow rate generating element. In a gas mixing device that obtains a mixed gas via a flow rate generating element, one of the pressure reducing valves is a non-relief type constant difference type pressure reducing valve, and the other pressure reducing valve at the constant flow rate generating element inlet side A gas mixing device, wherein a secondary pressure is set to a pilot pressure of the non-relief type constant difference type pressure reducing valve. 2. The non-relief type constant pressure reducing valve according to claim 1, wherein the opposite side of the secondary pressure including the pressure sensing means and the secondary pressure setting spring has a sealing structure, and the sealing is performed. A non-relief constant difference type pressure reducing valve characterized in that a pilot hole communicating with the space is formed. 3. A carbon dioxide gas is passed through a pressure reducing valve and a constant flow rate generating element on the one hand, while air is passed through another pressure reducing valve different from the pressure reducing valve and another constant flow rate generating element to the air. In a gas mixing apparatus for obtaining a mixed gas via a flow rate generating element, each of the pressure reducing valves is a non-relief type constant pressure reducing valve, and a constant flow rate generating element in each non-relief type constant pressure reducing valve. A gas mixing device characterized in that the secondary pressure on the inlet side is set to the pilot pressure of another non-relief type constant pressure reducing valve. 4. The non-relief type constant pressure reducing valve according to claim 3, wherein the opposite side of the secondary pressure including the pressure sensing means and the secondary pressure setting spring has a sealing structure, and the sealing is performed. A non-relief constant difference type pressure reducing valve characterized in that a pilot hole communicating with the space is formed.