JPH0351945B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a solenoid valve, and in particular, to an electromagnetic valve for controlling fuel evaporation to adsorb fuel evaporation gas generated in a float chamber of an engine carburetor to a canister according to various conditions. This relates to a solenoid valve that controls the opening and closing of gas passages.

[Prior Art] Conventionally, in a carburetor for an automobile engine,
When the engine is running or at high temperatures immediately after stopping, the fuel in the float chamber evaporates and evaporative fuel gas is generated.When the engine is running, this is burned by the engine through the inner vent, and when the engine is stopped, it is adsorbed by the canister and released into the atmosphere. This was to prevent this from happening. In particular, immediately after the engine is stopped, the carburetor is in a high-temperature atmosphere and a large amount of fuel evaporation gas is generated, so it is necessary to communicate the float chamber and the canister.

However, after a certain period of time has passed after stopping, the fuel evaporative gas will decrease and there is no problem even if you close the fuel evaporative gas passage leading to the canister.In fact, if you leave it open for a long time, the fuel in the float chamber will gradually evaporate and reach the canister. Since it is absorbed, it becomes difficult to restart the engine. For this reason, it is required that the fuel evaporative gas passage be reliably closed after a certain period of time has passed after the engine is stopped.

Therefore, a temperature switching valve is provided in the fuel evaporative gas passage along with an electromagnetic valve that energizes or de-energizes a solenoid coil to open or close a flow path in accordance with whether the ignition switch is turned on or off. For example, as shown in Japanese Patent Publication No. 60-35589,
Some valves integrate the electromagnetic valve and the temperature switching valve in response to the temperature in the float chamber to improve operating accuracy. This is fixed to a diaphragm that is activated by negative pressure in the engine's intake pipe, and has one end opposite the valve and the other end attached to a plunger that is activated by the excitation of a solenoid coil. A first spring that biases the valve and a second spring that biases the valve in the opening direction are provided, and when the engine is stopped, the valve opens and closes due to the force relationship between these springs. Then, a second spring is formed of a shape memory alloy that expands to a memorized shape at high temperatures, and is installed inside the diaphragm chamber.
When the engine is stopped, the valve body is actuated in the opening direction only when the fuel evaporative gas temperature is high to open the fuel evaporative gas passage.

[Problems to be Solved by the Invention] However, as described above, the biasing force of the spring made of a shape memory alloy is changed in accordance with the change in the temperature of the fuel evaporative gas, and thereby the valve is In devices that open and close the valve, due to the transformation point of the shape memory alloy (the temperature at which it returns to its memorized shape), the spring does not transform immediately after the engine stops, and therefore the valve does not open. may occur. To explain this in detail, as shown in Figure 2, when the spring that is sensitive to the fuel evaporative gas temperature is made of a shape memory alloy with a high transformation point, the Since the temperature inside the diaphragm chamber is low, the spring does not transform and the biasing force does not increase, so the valve body remains closed due to the spring force that biases the valve body in the closing direction.

As a countermeasure to this problem, if a spring made of a shape memory alloy with a slightly lower transformation point is adopted, as shown in Figure 3, the biasing force of the spring will not be restored and the valve body will remain open, causing fuel evaporation. After the gas temperature drops, the intended purpose of closing the valve cannot be achieved.

This is due to the temperature-displacement hysteresis characteristic of the shape memory alloy, and as shown in Figures 2 and 3, this is the temperature at which the spring returns to its pre-heating state (that is, the state in which the biasing force is restored). This is because there is a difference between the temperature (transformation point) at which the force increases.

Furthermore, in the device disclosed in Japanese Patent Publication No. 60-35589 mentioned above, since the diaphragm is exposed to the flow path of fuel evaporative gas, there is concern that the diaphragm may deteriorate. This is believed to be because the structure is designed to be sensitive to the temperature of the fuel evaporative gas, but since the specific heat of the fuel evaporative gas is small, it takes a considerable amount of time for the second spring to be heated to the temperature at which it transforms. This may lead to a delay in operation.
Furthermore, the first spring biases the valve in the closing direction,
As is clear from the description of the embodiment and the drawings,
Since it is disposed in the fuel evaporative gas flow path, there is a risk that the generated fuel evaporative gas will not be adsorbed by the canister and flow toward the engine due to flow path resistance. In order to prevent this, the stroke of the valve can be increased, but this would require increasing the size of the diaphragm device and solenoid coil.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a solenoid valve that reliably opens a fuel evaporative gas passage and connects a float chamber to a canister immediately after an engine stops, and also reliably closes off the passage after a certain period of time. It is.

[Means for Solving the Problems] In order to solve the above problems, the present invention employs the following configuration.

That is, in a solenoid valve that has a valve body that opens and closes a fluid passage formed in a body, and that is operated to close by movement of a plunger caused by excitation of a solenoid coil, the first valve body is formed through a diaphragm.
a diaphragm device having a diaphragm chamber and a second diaphragm chamber, the second diaphragm chamber being adjacent to the fluid passage through a perforated partition and the first diaphragm chamber being adjacent to the solenoid coil; The other end of the rod attached to the valve body is inserted through the hole in the partition wall and connected to the diaphragm on the second diaphragm chamber side, and the plunger is connected to the diaphragm on the first diaphragm chamber side. Further, a biasing means for biasing the diaphragm in a direction in which the valve body closes is provided in the diaphragm device, and a shape memory alloy that transforms into a memorized shape and increases the biasing force when a predetermined temperature is reached. A spring is provided adjacent to the solenoid coil to bias the plunger in the direction in which the valve body opens.

Here, the biasing means may be a compression spring interposed between the diaphragm and the partition wall in the second diaphragm chamber, or a leaf spring mounted overlapping with the diaphragm.

[Function] When such a solenoid valve is installed in the fuel evaporative gas passage, the solenoid coil is excited during engine operation, and at the same time, the diaphragm device is driven by the negative pressure in the intake pipe, and the valve body is moved in the closing direction. The fluid passage within the body is closed and the fuel vapor passage is therefore cut off. and,
After the engine is stopped, the solenoid coil is not excited and the negative pressure in the intake pipe disappears, so the valve body opens and closes depending on the force relationship between the biasing means and the shape memory alloy spring.

Immediately after the engine is stopped, the temperature inside the fluid passage is not necessarily high, but since the spring is installed adjacent to the solenoid coil, the residual heat generated by the solenoid coil when energized while the engine is running will ensure that the spring is transformed and attached. The force is increased to actuate the valve body in the opening direction against the biasing means. This biasing means is disposed within the diaphragm device, and since substantially only the valve body is present in the fluid passage, fuel evaporation gas is smoothly guided to the canister.

When a certain period of time passes and the temperature of the spring falls below a predetermined temperature and the biasing force is restored, the biasing force in the opening direction of the biasing means in the diaphragm device overcomes the biasing force in the opening direction of the spring, operating the valve body in the closing direction. to shut off the fuel evaporative gas passage.

[Embodiments] Hereinafter, preferred embodiments of the solenoid valve of the present invention will be described with reference to the drawings.

FIG. 1 shows a first embodiment of the present invention, in which a solenoid valve body 1 has an inlet port 2 communicating with a float chamber (not shown) of a carburetor and a canister (not shown). An outlet port 3 is provided which communicates via a fluid passageway 4 formed within the body 1. A rod 5 having a valve body 6 attached to one end for opening and closing the inlet port 2 is disposed in the fluid passage 4, and the valve body 6 is connected to a small diameter portion 5a formed in the rod 5.
The rod 5 is biased toward the inlet port 2 by the relief spring 7 installed between the E-ring 8 and the E-ring 8 fixed to the tip of the small diameter portion 5a, and the stepped portion 5b of the rod 5 Supported.

The other end of the rod 5 is inserted through a hole 9a provided in a partition wall 9 between the fluid passage 4 and the diaphragm device 10 while maintaining a gap, and further through the approximate center of the diaphragm 11 and the shell 12 that sandwiches the diaphragm 11. It is fitted into the through hole of the plunger 15.

The recess formed in the bobbin 20 and the recess formed in the body 1 are overlapped with each other via the diaphragm 11 to form a first diaphragm chamber 13 and a second diaphragm chamber 14, respectively, and the diaphragm device 10
is configured.

The first diaphragm chamber 13 communicates with an engine intake pipe (not shown) through a bobbin 20 and a negative pressure passage 16 formed in the body 1, and the second diaphragm chamber 14 connects the gap between the hole 9a and the rod 5. It communicates with the fluid passageway 4 via.

In the second diaphragm chamber 14, a seat member 17 is fitted into the rod 5 and attached to the shell 12, and when the valve body 6 is operated in the opening direction, it comes into contact with the wall 9 and prevents the movement of the rod 5a. It can be stopped.

The plunger 15 and the stator 18 are surrounded by a bobbin 20 around which a solenoid coil 19 is wound, and the stator 18 is fixed to a case 21 facing the plunger 15.

The case 21 and the plate 22 are fixed to the bobbin 20 with bolts 23, and the bobbin 20 is connected to the body 1 through a gasket 24 and a diaphragm 11.
Fixed. Here, stator 1
8, case 21, plate 22 and plunger 1
5 constitutes a magnetic circuit.

Then, within the second diaphragm chamber 14,
A compression spring 26 serving as a biasing means is inserted between the shell 12 and the partition wall 9, and the diaphragm 11
is urged in the direction of the stator 18, that is, upward in the figure.

The space between the plunger 15 and the stator 18 is made of a shape memory alloy, and when the transformation point (temperature at which it returns to the memorized shape) is exceeded, a force is exerted to return to the memorized shape and the plunger 15 and the stator 18 expand. A spring 27 configured to increase is inserted, and the spring 27 urges the plunger 15 in a direction to separate it from the stator 18, that is, in a downward direction in the drawing, in a direction in which the valve body 6 opens.

Note that the O-ring 25 seals between the stator 18 and the bobbin 20 so that the negative pressure within the first diaphragm chamber 13 does not decrease.

As shown in FIG. 1, the spring 27 is disposed between a small diameter stepped portion formed on the outer periphery of the stator 18 and a small diameter stepped portion formed on the outer periphery of the plunger 15, and is connected to the solenoid coil 19 via a bobbin 20. Since the solenoid coils 19 and 19 are adjacent to each other, good thermal conductivity from the solenoid coil 19 is maintained.

Next, the operation of this embodiment will be explained.

In the state shown in FIG. 1, the solenoid coil 19 is not energized, that is, the ignition switch is off and the engine is stopped.

When the ignition switch is turned on, the engine rotates, generating negative pressure in the intake pipe, which is transmitted to the first diaphragm chamber 13 via the negative pressure passage 16, pulling the diaphragm 11 upward in the figure, and passing it through the rod 5 to the valve body 6. is attached to the wall of inlet port 2. At the same time, the solenoid coil 19 is energized and the plunger 15
A suction force acts between the plunger 15 and the stator 18, and the plunger 15 moves until it comes into contact with the stator 18.
At this time, the valve body 6 comes into contact with the inlet port 2 and only the rod 5 moves further against the relief spring 7, so the valve body 6 is pressed against the wall surface of the inlet port 2 by the steady force of the relief spring 7 and closed. Becomes a valve state. Thereafter, since the solenoid coil 19 is energized while the engine is operating, the closed state is maintained regardless of the negative pressure that fluctuates depending on the engine operating state.

Therefore, during engine operation, the fuel evaporative gas passage is blocked, and the fuel evaporative gas generated in the float chamber of the carburetor is sent to the engine via the inner vent and burned.

Next, when the ignition switch is turned off and the engine is stopped, the solenoid coil 19 is no longer excited and the negative pressure in the intake pipe also disappears, so the valve body 6 is moved by the compression spring 26 and the shape memory alloy spring as the biasing means. The opening/closing operation is performed by the force relationship of the urging force 27. Moreover, the spring 27 is made of a shape memory alloy, and when the temperature exceeds a predetermined temperature (transformation point), the spring 27 transforms and the biasing force increases, so the valve body 6 opens and closes according to the ambient temperature of the spring 27.

The following description will be made with reference to FIG. 4 for ease of explanation.

During engine operation, the valve body 6 is biased in the closing direction by the electromagnetic force generated by the excitation of the solenoid coil 19, as described above, regardless of the biasing force of the spring 27.

Immediately after the engine stops, the temperature inside the fluid passage 4 is not so high, but the solenoid coil 19 is in a high temperature state (approximately 50 degrees Celsius or higher) due to residual heat during excitation, so the spring 27 exceeds the transformation point and the biasing force increases. .

As a result, the biasing force of the spring 27 in the valve opening direction is greater than the biasing force of the compression spring 26 in the valve closing direction, and the valve body 6 is moved in the opening direction (downward in FIG. 1), resulting in the state shown in FIG. Therefore, the fuel evaporative gas is sent from the float chamber to the canister and adsorbed.

After a certain period of time (30 to 60 minutes) has passed after the engine is stopped, the temperature near the solenoid coil 19 decreases to below a predetermined temperature, and the biasing force of the spring 27 is restored. Then, the biasing force of the compression spring 26 in the valve closing direction becomes larger than the biasing force of the spring 27 in the valve opening direction, and the valve body 6 comes to be pressed against the wall surface of the inlet port 2, and the fuel evaporative gas passage is blocked. Ru.

In the first embodiment, the second diaphragm chamber 14 communicates with the fluid passage 4 through the gap between the rod 5 and the hole 9a, but this gap is eliminated and a separate passage is provided to connect it to the atmosphere. It is also possible to communicate with each other. In this case, sealing between the rod 5 and the partition wall 9 is required, but the diaphragm 11
Since the compression spring 26 can completely cut off contact with fuel evaporation gas, it is expected that durability will be improved.

Further, in the first embodiment, the diaphragm device 10 is constructed by overlapping the body 1 and the bobbin 20 in order to reduce the number of parts, but it is of course possible to attach this to the body 1 as a separate body.

FIG. 5 shows a second embodiment of the present invention, in which a leaf spring 28 is used as the biasing means in place of the compression spring 26 in the first embodiment.
is polymerized and installed on the diaphragm 11,
The valve body 6 always urges the shell 12 and the rod 5 in the closing direction. According to this, the leaf spring 2
8 can be installed either inside the first diaphragm chamber 13 or inside the second diaphragm chamber 14.

[Effects of the Invention] As described above, according to the present invention, even immediately after the solenoid coil is de-energized due to engine stoppage, the valve body is reliably operated in the opening direction by increasing the biasing force of the spring due to the residual heat of the solenoid coil. This allows the fuel evaporative gas passage between the float chamber of the carburetor and the canister to communicate with each other. After a certain period of time, the biasing force of the spring is restored, so the biasing force of the biasing means in the diaphragm device reliably operates the valve body in the closing direction and blocks the fuel evaporative gas passage. can get.

Since the diaphragm is configured to be separated from the fluid passage, there is no risk of impairing durability, and since the biasing means is installed within the diaphragm device, there is no flow resistance, and when communication occurs, fuel evaporative gas is removed. This has the effect of ensuring a stable flow.

[Brief explanation of drawings]

FIG. 1 is a side sectional view of a solenoid valve according to a first embodiment of the present invention, FIGS. 2 and 3 are operating characteristic diagrams of the prior art, and FIG. 4 is an operating characteristic diagram of the first embodiment of the present invention. FIG. 5 is a side sectional view of a solenoid valve according to a second embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Body, 4... Fluid passage, 5... Rod, 6... Valve body, 10... Diaphragm device, 1
3...First diaphragm chamber, 14...Second diaphragm chamber, 15...Plunger, 19...Solenoid coil, 26...Compression spring, 27...
spring.

Claims (1)

[Scope of Claims] 1. A solenoid valve that has a valve body that opens and closes a fluid passage formed in a body, and that is closed by movement of a plunger caused by excitation of a solenoid coil. a first diaphragm chamber and a second diaphragm chamber;
a diaphragm device having a diaphragm chamber adjacent to the fluid passage through a perforated partition and a first diaphragm chamber adjacent to the solenoid coil, the other end of a rod attached to the valve body at one end; The plunger is inserted through a hole in the partition wall and connected to the diaphragm on the second diaphragm chamber side, and the plunger is connected to the diaphragm on the first diaphragm chamber side, and urges the diaphragm in the direction in which the valve body closes. A biasing means is provided in the diaphragm device, and is made of a shape memory alloy that transforms into a memorized shape when a predetermined temperature is reached to increase the biasing force, and the plunger is biased in a direction in which the valve body opens. A solenoid valve characterized in that a spring for biasing the solenoid coil is installed adjacent to the solenoid coil. 2. Claim 1, wherein the biasing means is a compression spring interposed between the diaphragm and the partition wall in the second diaphragm chamber.
Solenoid valve described in section. 3. The electromagnetic valve according to claim 1, wherein the biasing means is a leaf spring attached to overlap with the diaphragm.