JPH07217763A - Solenoid valve - Google Patents

Abstract

PURPOSE:To provide a solenoid valve which can control the flow rate at a low value under high negative pressure with a high degree of accuracy. CONSTITUTION:A force given by DELTAp (differential pressure)XS1 (S1 is a pressure receiving area determined by openings 15, 26a) acts on an auxiliary valve 21 which is therefore urged toward a valve seat 18. When the urging force of a coil spring 29 is set to a value which is less than DELTApXS1, even though a movable member 6 is attracted toward an iron core 5 so that the valve element 8 is lifted, the valve element 21 is continuously held being seated on a valve seat 18 so that the area of the opening 15 is decreased to the area of the opening area 26a, and accordingly, the flow rate is decreased. When the differential pressure >=p is lowered so that the urging force of a coil spring 29 overcomes the force given by DELTApXS1, the auxiliary valve 21 is lifted from the valve seat 18 so that the opening 16 is fully opened. Accordingly, the flow rate at a high negative pressure with a large pressure differential can be reduced, thereby it is possible to enhance the degree of accuracy for the low flow rate control.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solenoid valve for controlling the flow rate of fluid flowing in a fluid passage.

[0002]

2. Description of the Related Art FIG. 8 is a sectional view of a conventional solenoid valve. This electromagnetic valve is for a vehicle, and is for purging evaporated fuel generated from a fuel tank and passing through a canister to the engine by using intake pressure. Electromagnetic solenoid 1
Is composed of a coil 2, a yoke 3, a magnetic plate 4 and a fixed iron core 5. Movable bodies 6 are opposed to the fixed iron core 5 at intervals in the axial direction. The movable body 6 is composed of a movable iron core 9, a leaf spring 10 and a valve body 8 made of an elastic body such as rubber. The valve body 8 is attached to a central portion of a leaf spring 10 whose peripheral portion is sandwiched between the end frame 11 and the coil bobbin 12. Therefore, the movable body 6 is held by the leaf spring 10. The leaf spring 1
0 is made of a leaf spring material such as a phosphor bronze plate and is formed so as to be displaced in the axial direction by the movement of the movable body 6. The movable iron core 9 is movable in the axial direction by providing a gap between its outer periphery and the inner periphery of the coil bobbin 12, that is, the bearing portion 12a. The coil spring 7 is a movable body 6.
Is urged in a direction away from the fixed iron core 5.

An end frame 11 is fixedly connected to the electromagnetic solenoid 1 via a yoke 3. Ports 11 a and 11 b are integrally formed on the end frame 11. A fluid passage 13 is formed in the port 11a, and a fluid passage 13a orthogonal to the fluid passage 13 is formed. The fluid passage 13a communicates with the opening 15 at the end of the cylindrical portion 14 formed integrally with the end frame 11. A fluid passage 16 is formed in the port 11b. A fluid passage 17 that connects the fluid passage 16 and the opening 15 is formed in the end frame 11. The valve body 8 is provided at the tip of the cylindrical portion 14.
A valve seat 18 is formed so that the base 8a of the base can be brought into contact with and separated from the base. In addition, 19 is a seal member for maintaining airtightness,
Reference numeral 20 is a connector portion that connects the coil 2 and the power source.

The operation of the solenoid valve having the above structure is as follows. When the coil 2 of the electromagnetic solenoid 1 is energized, the coil current reaches the operation start current, and the attraction force of the electromagnetic solenoid 1 overcomes the biasing force of the coil spring 7 that biases the movable body 6 toward the valve seat 18, The movable body 6 is attracted to the fixed iron core 5 side. When the movable body 6 moves and the pedestal 8a of the valve body 8 separates from the valve seat 18, the opening 15 opens and the fluid passages 13, 1 are opened.
3a, 16 and 17 lead to port 11a and port 11
b communicates with each other, and the fluid flows between the ports 11a and 11b.

After that, when the energization of the coil 2 of the electromagnetic solenoid 1 is cut off and the attraction force of the electromagnetic solenoid 1 falls below the biasing force of the coil spring 7, the movable body 6 moves backward and the pedestal 8a of the valve body 8 is moved. Is seated on the valve seat 18 to close the opening 15 and the flow of fluid between the ports 11a and 11b is stopped. Since the flow rate of the fluid between the ports 11a and 11b described above depends on the ratio of the opening / closing time of the valve body 8, the flow rate is adjusted by changing this ratio (hereinafter referred to as the duty ratio).

By operating the solenoid valve as described above, the flow rate characteristic shown in FIG. 9 can be obtained. This flow rate characteristic is
It can be obtained from the opening area of the opening 15 and the valve body 8 (minimum aperture diameter φd × lift amount), duty ratio, differential pressure, and the like. The differential pressure at this time is determined by the engine intake pipe pressure, and is generally a high negative pressure (about -450 mmHg) in the engine low load range (when idle, etc.), and the actual use range of the above flow rate characteristic is low duty. Use only the low flow range of the ratio. or,
In the engine high load range, low negative pressure (approximately -150 mmHg
And the high flow rate range with a high duty ratio is used.
As described above, the use range of the flow rate characteristic is changed according to the intake air amount of the engine.

[0007]

However, in the above-described conventional solenoid valve, since the throttle diameter and the lift amount are constant, as is clear from the flow rate characteristics shown in FIG. Small pressure → small flow rate. This is because the throttle diameter is determined based on the required maximum flow rate at low negative pressure. Therefore, when a low duty ratio region is used during high negative pressure such as at idle, the flow rate becomes large at high negative pressure, so the gradient of the duty ratio-flow rate characteristic becomes steep and the duty ratio control range is limited. This makes it difficult to perform the purge control with high accuracy.

Further, under the request of strengthening environmental protection, it is inevitable that automobile exhaust gas regulations will be further strengthened. Along with this, the demand for higher precision of the purge control required for the evaporative purge system of the exhaust system becomes stricter. The flow rate characteristic of the solenoid valve that performs the control is an important factor in controlling the optimum purge amount of the evaporated fuel. In particular, at the time of idling, since the intake air amount is small and the fuel consumption ratio by purging is large, precise purge control accuracy is required to maintain the air-fuel ratio in the ideal state. However, as described above, according to the flow rate characteristic of the conventional solenoid valve, it is difficult to perform the purge control at the time of idling with high accuracy, and thus there is a problem that the stricter vehicle exhaust gas regulation cannot be cleared. The present invention has been made to solve the above problems, and an electromagnetic valve that can control a low flow rate with high accuracy by making only the gradient of the flow rate characteristic at high negative pressure (large differential pressure) gentle. It is intended to be provided.

[0009]

In order to achieve the above object, a solenoid valve of the present invention according to claim 1 is provided with a sub valve body for reducing the opening area of an opening of a fluid passage to be opened and closed, and a biasing member. A main valve body that closes the opening and shuts off the fluid passage by the urging force of the electromagnetic valve, and an electromagnetic solenoid that urges the main valve body against the urging force of the urging member to open the opening of the fluid passage. It is characterized by having and.

According to another aspect of the present invention, there is provided a solenoid valve which is seated on a first valve seat formed at an opening end of a fluid passage to be opened and closed to reduce an opening area of the opening. A sub-valve body, a main valve body seated on a second valve seat formed on the sub-valve body, a first urging member for urging the sub-valve body in a direction away from the first valve seat, A second urging member for urging the main valve body against the urging force of the first urging member; and a second urging member for urging the main valve body against the urging force of the second urging member, An electromagnetic solenoid that opens the opening of the fluid passage, and when the bias of the electromagnetic solenoid is released, the main valve body is seated on the second valve seat by the biasing force of the second biasing member, It is characterized in that the sub valve body is pressed to be seated on the first valve seat, the opening is closed, and the fluid passage is shut off.

The solenoid valve of the present invention according to claim 3 is
3. The differential pressure between fluid passages communicating with each other through the opening when the main valve body is biased by the electromagnetic solenoid and separated from the second valve seat of the sub valve body in the structure according to claim 2. Is less than or equal to a predetermined pressure, the sub valve body
The urging force of the first urging member is set so as to separate from the valve seat.

[0012]

According to the solenoid valve of the first aspect, the opening area of the opening of the fluid passage opened and closed by the main valve body is reduced by the sub valve body. Therefore, the flow rate passing through the fluid passage is reduced, and the low flow rate control region is expanded.

Further, according to the electromagnetic valve of the second aspect, when the bias of the electromagnetic solenoid is released, the second valve seat in which the main valve body is formed into the sub valve body by the biasing force of the second biasing member. And the sub-valve is pressed to be seated on the first valve seat formed at the opening end of the fluid passage, and the opening is closed to shut off the fluid passage. Therefore, the opening can be opened and closed in two steps by the main valve body and the sub valve body, and high flow rate and low flow rate control can be performed.

According to the solenoid valve of the third aspect, when the main valve body is biased by the electromagnetic solenoid and separated from the second valve seat of the sub valve body, the difference between the fluid passages communicating through the openings is provided. When the pressure is equal to or higher than the predetermined pressure, the differential pressure overcomes the urging force of the first urging member, and the sub valve body is still seated on the first valve seat formed at the opening end of the fluid passage. Is less than or equal to a predetermined pressure, the sub-valve element is separated from the first valve seat by the urging force of the first urging member to fully open the opening. Therefore, when the differential pressure is equal to or higher than the predetermined pressure, even if the main valve body is fully opened, the opening area of the fluid passage opening is reduced by the auxiliary valve body, and the flow rate passing through the fluid passage is reduced when the differential pressure is large. There is an effect that the low flow rate control range is expanded and the control accuracy at the time of low flow rate can be improved.

[0015]

EXAMPLE An example in which the solenoid valve of the present invention is applied as a purge control valve for a vehicle will be described. Since the purge control system itself is not the subject matter of the present invention, its outline is shown in FIG. 1 and briefly described. The purge control system purges the vaporized fuel G generated in the fuel tank 100 and adsorbed in the canister 101 by using an intake pressure of the engine by opening and closing a solenoid valve according to the engine load condition to remove the vaporized fuel G into the atmosphere. It is intended to prevent the release to the. Therefore, the port 11a of the solenoid valve is connected to the engine intake pipe 102,
The ports 11b are connected to the canisters 101, respectively.

Regarding the solenoid valve according to the embodiment of the present invention,
It will be described with reference to the accompanying drawings FIGS. 2 to 8. FIG. 2 is a sectional view of the solenoid valve. It should be noted that, in FIG. 2, the structure is the same as that of the above-described conventional technique except for the structure of the sub-valve body 21 and the structure related to the sub-valve body 21, which are features of the present invention. Therefore, the same components are designated by the same reference numerals and detailed description thereof will be omitted.

As shown in FIGS. 2, 3 and 4, the sub-valve body 21 gently covers the outer periphery of the distal end portion of the cylindrical portion 14 and covers the valve seat 18 (corresponding to the first valve seat of the present invention). An opening 23 is formed at the center of the abutting cap body 22. An annular protrusion 24 is formed outside the cap body 22 and is concentric with the opening 23. The annular protrusion 2
4, a fluid passage 25 is formed by appropriately providing a notch. Further, a grommet 26 is fitted on the edge of the opening 23. The grommet 26 is made of an elastic body such as synthetic rubber or soft synthetic resin, and has a diaphragm opening 26a formed through the center in the axial direction. A pedestal 27 is formed on the surface that abuts the valve seat 18, and a valve seat 28 (corresponding to the second valve seat of the present invention) is formed on the surface on the opposite side where the annular projection 24 is formed. At this time, the valve body 8 is formed of an elastic body such as rubber or a non-elastic body such as metal or synthetic resin.

The sub-valve body 21 is separated from the valve seat 18 by a coil spring 29 (corresponding to the first urging member of the present invention) hung on the outer periphery of the cylindrical portion 14 formed integrally with the end frame 11. Biased in the direction. However, the coil spring 7 (corresponding to the second biasing member of the present invention)
Since the urging force of the valve spring 8 overcomes the urging force of the coil spring 29, the valve body 8 urged by the coil spring 19 is seated on the valve seat 28 with its pedestal 8a fitted in the annular projection 24, and The pedestal 27 formed by pressing the valve body 21 on the grommet 26 is seated on the valve seat 18 to close the opening 15.

The operation of the solenoid valve having the above structure is as follows. When the electromagnetic solenoid 1 is energized and the attraction force of the electromagnetic solenoid 1 overcomes the biasing force of the coil spring 7, the movable body 6 is attracted to the fixed iron core 5 side. When the movable body 6 is sucked, the fluid passage 13 a is passed through the fluid passage 17.
And the fluid passage 16 communicate with each other. At this time, the throttle opening 26a of the sub valve body 21 is provided between the fluid passage 13a communicating with the port 11b and the fluid passage 17 communicating with the port 11a.
As shown in FIG. 4, the differential pressure Δp depends on the atmospheric pressure and the engine negative pressure.
Occurs. Such a differential pressure Δp is represented by the following theoretical equation of a fluid model.

[0020]

[Number 1] flow rate ^{Q = C (πd 2/4} ) √ (2 △ p / ρ) where, C is the flow coefficient, [rho is the fluid density. The differential pressure Δp can be easily obtained by an experiment.

When the differential pressure Δp is generated, a force having a magnitude of Δp × S ₁ (S ₁ is a pressure receiving area determined by the openings 15 and 26a, the same applies below) acts on the sub-valve body 21, It is urged toward the valve seat 18 side. Therefore, the coil spring 29
By setting the urging force of A to a value smaller than Δp × S ₁ , the sub valve body 21 continues to be seated on the valve seat 18 even when the movable body 6 is attracted to the fixed iron core 5 side and the valve body 8 is separated. As a result, the area of the opening 15 is reduced to the area of the throttle opening 26a, and the flow rate is reduced. Therefore, the Komake pressure time as shown in FIG. 5, the gradient of the flow characteristics up to the maximum use point Q _a becomes gentle, use zone i.e. underflow quantity control area is enlarged.

On the contrary, when the differential pressure Δp decreases and the biasing force of the coil spring 29 overcomes the force of Δp × S ₁ , the sub-valve body 21 synchronizes with the operation of the movable body 6. When the valve is opened, it is separated from the valve seat 18 by the urging force of the coil spring 29, and the opening 15 is fully opened. When the valve is closed, the urging force of the coil spring 7 causes the valve body 8 to press the sub valve body 21 to be seated on the valve seat 18 to close the opening 15. The flow rate at high negative pressure can be arbitrarily set by changing the diameter of the throttle opening 26a of the sub valve body 21. Further, the differential pressure at the time of starting the movement of the sub valve body 21 can be arbitrarily set by changing the biasing force of the coil spring 29 and the pressure receiving area S ₁ of the differential pressure.

As is clear from the above description of the operation, it is possible to improve the low flow rate control accuracy when the negative pressure is high. Further, by reducing Δp × S ₂ (S ₂ is the area of the throttle opening 26a), the electromagnetic force required to open the movable body 6 is reduced, and the area of the opening 15 can be increased. As shown in the stroke-flow rate characteristic of No. 6, the rising angle α of the flow rate is increased and the stroke of the movable body 6 can be shortened. Therefore, there are advantages that the electromagnetic solenoid 1 is downsized, the response speed between the fully open and fully closed of the movable body 6 is increased, and the rising linearity of the duty ratio-flow rate characteristic is improved.

FIG. 7 is a sectional view showing another embodiment of the solenoid valve. The solenoid valve of the above embodiment is different from the solenoid valve in the configuration of the sub valve body 31 and the first urging member for urging the sub valve body 31. The sub-valve body 31 is an elastic ring body such as rubber or soft synthetic resin having a throttle opening 32 in the center, and the central portion of the leaf spring 33, which is the first urging member, is inserted into the outer peripheral portion to be integrated. It was done. The leaf spring 33 is sandwiched between the end frame 11 and the coil bobbin 12 like the leaf spring 10 that holds the movable body 6. The sub-valve body 31 is biased by the leaf spring 33 in a direction away from the valve seat 18.

A fluid passage 13a communicating with the port 11b and a fluid passage 1 communicating with the port 11a of the solenoid valve constructed as described above.
Between 7 and 7, a differential pressure Δp is generated by the atmospheric pressure and the engine negative pressure through the throttle opening 32 of the sub valve body 31. The sub-valve element 31 is urged toward the valve seat 18 by a force of Δp × S ₁ . Therefore, by setting the biasing force of the leaf spring 33 to a value smaller than Δp × S ₁ , the sub-valve element 31 can move the movable element 6
Is sucked toward the fixed iron core 5 side and the valve body 8 is separated,
The valve seat 18 continues to be seated, the area of the opening 15 is reduced to the area of the throttle opening 32, and the flow rate is reduced.

On the contrary, when the differential pressure Δp decreases and the biasing force of the leaf spring 33 overcomes the force of Δp × S ₁ , the sub valve body 31 synchronizes with the operation of the movable body 6, When the valve is open, the leaf spring 3
The urging force of 3 separates from the valve seat 18, and the opening 15 is fully opened. When the valve is closed, the urging force of the coil spring 7 causes the valve body 8 to press the sub valve body 31 to be seated on the valve seat 18 to close the opening 15. The biasing force of the plate spring 33 can be adjusted by the plate thickness, shape, and the like.

The sub-valve body 31 of the above-mentioned embodiment is formed by integrally molding the leaf spring 33 on the elastic ring body such as rubber, and has an advantage that the number of parts can be reduced and the assembling workability can be improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a purge control system for a vehicle.

FIG. 2 is a sectional view showing an embodiment of a solenoid valve of the present invention.

FIG. 3 is a perspective view of a sub valve body of the above embodiment.

FIG. 4 is an enlarged cross-sectional view of a sub-valve body explaining generation of a differential pressure.

FIG. 5 is a characteristic diagram showing a flow rate characteristic with respect to a duty ratio of the solenoid valve of the present invention.

FIG. 6 is a characteristic diagram showing flow rate characteristics with respect to the stroke of the valve body of the solenoid valve of the present invention.

FIG. 7 is a sectional view showing another embodiment of the solenoid valve of the present invention.

FIG. 8 is a sectional view of a conventional solenoid valve.

FIG. 9 is a characteristic diagram showing a flow rate characteristic with respect to a duty ratio of a conventional solenoid valve.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electromagnetic solenoid 7 Coil spring (2nd biasing member) 8 Valve body (main valve body) 13, 13a, 16, 17 Fluid passage 15 Opening 18 Valve seat (1st valve seat) 21, 31 Sub valve body 26a, 32 Throttle opening 28 Valve seat (second valve seat) 29 Coil spring (first biasing member) 33 Leaf spring (first biasing member)

Claims (3)

[Claims] 1. A sub-valve body that reduces an opening area of an opening of a fluid passage that is opened and closed, a main valve body that closes the opening by a biasing force of a biasing member to shut off the fluid passage, and the biasing member. An electromagnetic solenoid for urging the main valve body against the urging force of the electromagnetic valve to open the opening of the fluid passage. 2. A sub-valve body which is seated on a first valve seat formed at an opening end of a fluid passage to be opened and closed to reduce an opening area of the opening, and a second valve seat formed on the sub-valve body. The seated main valve body, the first urging member for urging the sub valve body in the direction away from the first valve seat, and the main valve body against the urging force of the first urging member. A second urging member for urging, and an electromagnetic solenoid for urging the main valve body against the urging force of the second urging member to open the opening of the fluid passage. When the urging is released, the main valve body is seated on the second valve seat by the urging force of the second urging member, and the sub-valve body is pressed to seat on the first valve seat. A solenoid valve which closes an opening to shut off the fluid passage. 3. A differential pressure between fluid passages communicating through the opening when the main valve element is biased by the electromagnetic solenoid and separated from the second valve seat of the sub-valve element. 3. The solenoid valve according to claim 2, wherein the urging force of the first urging member is set so that the sub-valve element separates from the first valve seat at the time.