Electromagnetic valve for ORVR system

[0002] This application is based on and incorporates herein by reference Japanese Patent Application No. 2000-49447 filed on Feb. 25, 2000.

[0003] 1. Field of the Invention

[0004] The present invention relates to an electromagnetic valve working as a pressure regulating valve and an opening/closing valve suitable for use in an ORVR system.

[0005] 2. Description of Related Art

[0006] A conventional vapor fuel treating system requires an ORVR (On Board Refueling Vapor Recovery) system shown in FIG. 7. In the ORVR system, vapor fuel arising in a fuel tank during fuel supply is not discharged to atmosphere, and a canister adsorbs the vapor fuel.

[0007] In the ORVR system shown in FIG. 7, pipes 202 and 205 connect a fuel tank 200 with a canister 210. A pressure sensor 201 is provided in the fuel tank 200 for detecting pressure inside the fuel tank 200. When a vapor fuel leak is detected, an electromagnetic valve 203 opens to allow the fuel tank 200 to communicate with the canister 210. An internal pressure valve 204 includes a diaphragm, and maintains the pressure inside the fuel tank 200 over a predetermined pressure. A fuel supply valve 206 includes a diaphragm. When the pressure inside the fuel tank 200 rises due to a fuel supply, the fuel supply valve 206 opens to discharge the vapor fuel into the canister 210 such that the canister 210 adsorbs the vapor fuel. When a purge valve 213 opens, an intake air passage 208 communicates with the canister 210.

[0008] In the conventional ORVR system in FIG. 7, there is need to prepare a lot of valves and pipes such as two pipes 202, 205 for connecting the fuel tank 200 with the canister 210, electromagnetic valve 203, internal pressure valve 204, and supply valve 206. Thus, an installation space for these parts is necessary, and the number of installations is increased.

[0009] An object of the present invention is to provide an electromagnetic valve working as pressure regulating valve and opening/closing valve, for reducing the number of parts.

[0010] According to a first aspect of the present invention, when a coil is not energized, a pressure-receiving member switches a communication between a first passage and a second passage due to pressure difference between a first pressure chamber and a second pressure chamber. That is, an electromagnetic valve works as a pressure regulating valve. When the coil is electrically energized, the first passage communicates with the second passage regardless the pressure difference between the first pressure chamber and the second pressure chamber. That is, the electromagnetic valve works as an electromagnetic opening/closing valve.

[0011] In this way, a single electromagnetic valve works as pressure regulating valve and opening/closing valve. Thus, the number of parts is reduced, so that the system is easily assembled. The system is compacted, so that the system is easily installed in a narrow space.

[0012] According to a second aspect of the present invention, a stator magnetically attracts the permanent magnet provided in the moving core. A communication between the first passage and the second passage is shut when the moving core is close to the stator. Thus, even when the magnetic force of the permanent magnet is small, sufficient force for closing valve is attained. Further, the coil is energized to generate a magnetic repelling force between the permanent magnet and the stator, so that the moving core leaves the stator. Since air gap between the moving core and the stator is small, even when the wind number of the coil is small, the electromagnetic valve can open, thereby compacting the electromagnetic valve.

[0013] Additional objects and advantages of the present invention will be more readily apparent from the following detailed description of preferred embodiments thereof when taken together with the accompanying drawings in which:

[0014] FIG. 1 is a cross-sectional view showing an electromagnetic valve;

[0015] FIG. 2 is a schematic view showing an ORVR system including the electromagnetic valve;

[0016] FIGS. 3A and 3B are cross-sectional views showing an operation of the electromagnetic valve while a coil is not energized;

[0017] FIGS. 4A and 4B are cross-sectional views showing an operation of the electromagnetic valve while vapor fuel leak is detected;

[0018] FIG. 5 is a graph showing an opening/closing state of each valve and an output signal of a pressure sensor;

[0019] FIGS. 6A-6C are cross-sectional views showing an operation of the electromagnetic valve during fuel supply, and

[0020] FIG. 7 is a schematic view showing a conventional ORVR system.

[0021] FIG. 2 shows an ORVR (On Board Refueling Vapor Recovery) system including an electromagnetic valve 10. A fuel tank 100 communicates with a canister 110 through pipes 102 and 103. A housing 11 of the electromagnetic valve 10 includes a first connecting pipe 12 and a second connecting pipe 13. The first connecting pipe 12 connects with the pipe 102, and the second connecting pipe 13 connects with the pipe 103. A pressure sensor 101 detects a pressure inside the fuel tank 100 to detect a vapor fuel leak.

[0022] The canister 110 adsorbs the vapor fuel. When an electromagnetic valve 112 opens, the canister 110 is exposed to the atmosphere through a pipe 111. The canister 110 communicates with an intake pipe 105 through a pipe 104. A purge valve 113 provided in the pipe 104 opens, the canister 110 and the pipe 102 communicate with an intake air passage 105a.

[0023] As shown in FIG. 1, the housing 11 of the electromagnetic valve 10 is made of resin. A first passage 12ais formed within the first connecting pipe 12, and a second passage 13ais formed within the second connecting pipe 13. A valve seat 14 is formed at the end of the first connecting pipe 12 inside the housing 11.

[0024] A valve member 20 includes a valve body 21 and a contacting portion 22 made of rubber. The contacting portion 22 is capable of seating on the valve seat 14. A first communication passage 20apenetrates through the center of the valve body 21, so that the first passage 12ais capable of communicating with a first pressure chamber 45. A spring 23 urges the valve member 20 toward a pressure-receiving member 30.

[0025] The pressure-receiving member 30 separates the first pressure chamber 45 from a second pressure chamber 46. The first pressure chamber 45 communicates with the second passage 13a.A pressure-receiving area of the valve member 20, which receives a pressure from the first passage 12a, is the same as a pressure-receiving area of the pressure-receiving member 30, which receives a pressure from the second pressure chamber 46. The pressure-receiving member 30 includes a contacting side member 31, a shaft side member 32, a contacting portion 33 made of rubber, and a diaphragm 40. The inner periphery of the diaphragm 40 is pinched between the contacting side member 31 and the shaft side member 32, and the outer periphery thereof is pinched between a first plate 41 and a second plate 42. A through hole penetrates through the centers of the contacting side member 31 and the shaft side member 32 to form a second communication passage 30a.The second communication passage 30aincludes a side hole 30bcommunicating with the second pressure chamber 46. When the contacting portion 33 of the pressure-receiving member 30 contacts the valve body 21 at the outer periphery of the first communication passage 20a, communication between the first communication passage 20aand the first pressure chamber 45 is shut.

[0026] An electromagnetic operating unit 50 includes a coil 52 wound around a spool 51, a stator core 55, an end core 56, a yoke 57 and a moving core 60. The coil 52 is electrically connected to a terminal 53. The stator core 55, the end core 56 and the yoke 57 are made of magnetic material, and form a stator. The moving core 60 includes a permanent magnet 61, a resin portion 62, and a shaft 63. The resin portion 62 molds the permanent magnet 61 and is screwed to the shaft 63. A screw 65 is screwed into an adjust hole 11aof the housing 11, and the screw 65 is fixed by a potting resin 66.

[0027] When the coil 52 is not energized, the permanent magnet 61 is attracted to the stator core 55, so that the moving core 60 is attracted rightwardly in FIG. 1 (arrow A direction). Here, FIG. 1 shows a state that the coil 52 is not energized in the electromagnetic valve 10.

[0028] The left end 63aof the shaft 63 is formed in X-shape extending radially outwardly. The stator core 55 includes a X-shaped groove at the inside wall thereof, and the left end 63ais fit into the X-shaped groove. An adjuster is inserted through the adjust hole 11ato adjust a screwed amount of the resin portion 62, so that an attraction force between the permanent magnet 61 and the stator core 55, which is a closing valve force of the electromagnetic valve 10, is adjusted. Here, since the left end 63aof the shaft 63 is fit into the X-shape groove of the stator core 55 and does not rotate, the closing valve force of the electromagnetic valve 50 is adjusted while the shaft 63 is inserted into the stator core 55. After the screwed amount of the resin portion 62 is adjusted, the screw 65 seals the adjust hole 11a, and the potting resin 66 molds the screw 65.

[0029] An operation of the electromagnetic valve 10 will be explained.

[0030] As shown in FIG. 3A, when the coil 52 is not energized, the attraction force between the permanent magnet 61 and the stator core 55 urges the moving core 60 rightwardly (arrow A direction). The pressure receiving member 30 contacts the valve member 20, and is urged toward the shaft 63. The valve member 20 seats on the valve seat 14 against the urging force of the spring 23.

[0031] In the state shown in FIG. 3A, since the first passage 12acommunicates with the second pressure chamber 46 through the first and second communication passages 20aand 30a, pressure inside the first passage 12ais the same as inside the second pressure chamber 46.

[0032] When pressure inside the second passage 13aand the first pressure chamber 45 rises due to a pressure rise inside the fuel tank 100, pressure difference between the first pressure chamber 45 and the second pressure chamber 46 increases, thereby increasing a force urging the pressure receiving member 30 toward an arrow B direction. Thus, as shown in FIG. 3B, the pressure receiving member 30 moves toward the arrow B direction while repelling the attraction force between the permanent magnet 61 and the stator core 55. Here, the valve member 20 seats on the valve seat 14 due to pressure difference between the first pressure chamber 45 and the first passage 12a.Since the pressure receiving member 30 leaves the valve member 20, the second passage 13aand the first pressure chamber 45 communicate with the first passage 12athrough the first communication passage 20a.When the first passage 12acommunicates with the second passage 13a, the vapor fuel inside the fuel tank 100 is discharged to the canister 110, and adsorbed by the canister 110.

[0033] When the vapor fuel leak in the ORVR system is detected, the electromagnetic valve 112 opens, as shown in FIG. 5, to expose the canister 110 to the atmosphere. Pressure inside the fuel tank 100 may be either of positive or negative pressure. Next, the coil 52 is energized under a valve closing state shown in FIG. 4A. The coil 52 is energized such that the stator core 55 generates a repulsion force against the magnetic force 61 between the stator core 55 and the permanent magnet 61. Then, as shown in FIG. 4B, the permanent magnet 61 repels the stator core 55, and the moving core 60 moves toward the arrow B direction. When the moving core 60 moves toward the arrow B direction, the pressure receiving member 30 and the valve member 20 move toward the arrow B direction by the urging force of the spring 23. Then, the valve member 20 leaves the valve seat 14, and the first passage 12acommunicates with the first pressure chamber 45 and the second passage 13athrough an opening between the valve member 20 and the valve seat 14.

[0034] When the first passage 12acommunicates with the second passage 13a, both electromagnetic valve 112 and the purge valve 113 open as shown in FIG. 5, the intake air passage 105acommunicates with the fuel tank 100 through the pipes 102, 103 and 104. Here, when there is no leak in the pipes 102, 103 and 104 and the fuel tank 100, pressure inside the fuel tank 100 reaches a constant negative pressure as shown in FIG. 5. When there is a leak somewhere, pressure inside the fuel tank 100 increases as shown by broken line 120 in FIG. 5. In this way, pressure inside the fuel tank 100 is detected to detect a leak in the ORVR system.

[0035] When a cover of the fuel tank is opened for fuel supply, the coil 52 of the electromagnetic valve 52 is energized. When the coil 52 is energized by opening the cover of the fuel tank 100 under a valve closing state shown in FIG. 6A, the moving core 60 and the pressure receiving member 30 move toward the arrow B direction as shown in FIG. 6B. While the fuel is supplied, pressure inside the fuel tank 100 rises, and pressure difference between inside the fuel tank 100 and inside the canister 101 becomes over a predetermined value, so that the valve member 20 keeps seating on the valve seat 14 due to the pressure inside the second passage 13a. In this state, the first passage 12acommunicates with the second passage 13athrough the first communication passage 20a.

[0036] When the vapor fuel in the fuel tank 100 is discharged and pressure inside the fuel pressure 100 decreases and the pressure difference becomes under the predetermined value, the valve member 20 leaves the valve seat 14 as shown in FIG. 6C. Then, the first passage 12acommunicates with the second passage 13athrough the opening between the valve member 20 and the valve seat 14. Here, cross-sectional area of the opening between the valve member 20 and the valve seat 14 is larger than cross-sectional area of the first communication passage 20a. Since the first passage 12acommunicates with the second passage 13aregardless the valve member 20 leaves the valve seat 14 or not, the vapor fuel arising in the fuel tank during the fuel supply is discharged toward the canister 110 to be adsorbed by the canister 110.

[0037] In the present embodiment, the permanent magnet 61 attached to the moving core 60 is attracted to the stator core 55, the moving core 60 urges the pressure receiving member 30 to contact the valve member 20, and the valve member 20 seats on the valve seat 14, for shutting the communication between the first passage 12aand the second passage 13a.

[0038] Contrary to this, when a permanent magnet is not used and an elastic member such as a spring urges a moving core to be apart from the stator core to make the pressure receiving member 30 to contact the valve member 20 and the valve member 20 seats on the valve seat 14, a coil has to be energized while the moving core is apart from the stator core to attract the moving core toward the stator core. Thus, a large magnetic force is required to attract the moving core toward the stator core. For generating the large magnetic force, the wind number of the coil has to be increased, thereby enlarging an electromagnetic operating unit.

[0039] Further, according to the present invention, the electromagnetic valve 10 starts to open under the state that the permanent magnet 61 abuts on the stator core 55 and the first passage 12adoes not communicate with the second passage 13a.As an air gap between the permanent magnet 61 and the stator core 55 decreases, an attraction force due to a magnetic force generated therebetween increases. Thus, even when the permanent magnet 61 is small, a large force for closing valve is attained.

[0040] According to the present embodiment, the coil 52 is energized such that magnetic pole repelling the permanent magnet 61 is generated in the stator core 55 facing the permanent magnet 61, so that the permanent magnet 61 leaves the stator core 55. Here, since the air gap between the permanent magnet 61 and the stator core 55 is small, the repelling force generated between the permanent magnet 61 and the stator core 55 is large. Thus, even when the magnetic force generated by the coil 52 is small, the permanent magnet 61 leaves the stator core 55. The wind number of the coil 52 can be decreased, thereby compacting the electromagnetic valve.

[0041] In the above-described embodiments, the pressure receiving member 30 moves due to a pressure difference between the first pressure chamber 45 and the second pressure chamber 46, and the electromagnetic valve 10 operates as a pressure adjusting valve. When the coil 52 is energized to move the pressure receiving member 30 apart from the valve member 20, the first passage 12acommunicates with the second passage 13aregardless the valve member 20 leaves the valve seat 14 or not, so that the electromagnetic valve 10 works as a opening/closing valve.

[0042] In this way, the electromagnetic valve 10 working as pressure adjusting valve and opening/closing valve is used in the ORVR system. That is, a single electromagnetic valve 10 regulates the pressure inside the fuel tank 100 under a predetermined pressure, discharges the vapor fuel arising during fuel supply into the canister 110, and detects the vapor fuel leak. Further, a pipe connection line is simplified. Thus, the number of parts is reduced, so that the system is easily assembled. The system is compacted, so that the system is easily installed in a narrow space.

[0043] According to the present embodiment, the pressure receiving area of the valve member 20 receiving a pressure from the first passage 12ais almost the same as the pressure receiving area of the pressure receiving member 30 receiving a pressure from the second pressure chamber 46. When the pressure receiving member 30 shuts the communication between the first communication passage 20aand the first pressure chamber 45, the first communication passage 20acommunicates with the second pressure chamber 46 through the second communication passage 30a. When the valve member 20 contacts the pressure receiving member 30 and seats on the valve seat 14, pressure inside the second pressure chamber 46 is the same as pressure inside the first passage 12a. Thus, a force the valve member 20 receives from the first passage 12acancels a force the pressure receiving member 30 receives from the second pressure chamber 46.

[0044] The magnet force of the permanent magnet 61 can be reduced, since the pressure receiving area of the valve member 20 receiving pressure from the first passage 12ais larger than the pressure receiving area of the pressure receiving member 30 receiving pressure from the second pressure chamber 46. The urging force of the spring 23 can be reduced since the pressure receiving area of the pressure receiving member 30 receiving pressure from the second pressure chamber 46 is larger than the pressure receiving area of the valve member 20 receiving pressure from the first passage 12a.Therefore, the size of electromagnetic valve 10 can be compacted.

[0045] According to the present embodiment, the stator core 55 magnetically attracts the permanent magnet 61, and the communication between the first passage 12aand the second passage 13ais shut when the permanent magnet 61 abuts on the stator core 55. Thus, even when the magnetic force of the permanent magnet 61 is small, sufficient force for closing valve is attained. The coil 52 is energized to generate a magnetic repelling force between the permanent magnet 61 and the stator core 55, so that the permanent magnet 61 leaves the stator core 55. Even when the wind number of the coil 52 is small, the electromagnetic valve 10 can open, thereby compacting the electromagnetic valve 10.

[0046] A moving core may be formed by magnetic material instead of the permanent magnet 61 and the resin portion 62 in the above-described embodiment, and a permanent magnet may be attached to the stator core 55. When the coil 52 is not energized, the moving core is attracted to the stator core 55 due to the magnetic force of the permanent magnet attached to the stator core 55. When the coil 52 is energized such that a magnetic flux of which the direction is opposite to a magnetic flux direction of the permanent magnet is generated within the stator core 55, the magnetic attraction force between the moving core and the stator core 55 decreases. At this time, the moving core leaves the stator core 55 due to the urging force of the spring 23 urging the valve member 20 toward the pressure-receiving member 30.

[0047] A spring may urge the moving core to leave the stator core 55 to close an electromagnetic valve, and a coil may be energized to attract the moving core toward the stator core to open the electromagnetic valve.

[0048] According to the above-described embodiment, an electromagnetic valve is applied to an ORVR system. Alternatively, the electromagnetic valve in the present invention may be applied to a system in which a pressure is adjusted between two pressure sources and a communication therebetween is made if necessary.