Fuel vapor leak check module

A fuel vapor leak check module has a pump for generating a pressure gradient between an inside and an outside of a fuel tank. The pump is driven by a motor which has driving shaft supported by a bearing. A lubricant is provided between the driving shaft and the bearing. When the pump is operated, a pressure gradient between a pump-side space and a motor-side space is generated whereby a lubricant is introduced from one of the pump-side space and the motor-side space to another, so that the introduced lubricant deteriorates the pump performance or motor performance. To avoid such a situation, communication passage is provided which communicates the motor-side space and the pump-side space. The inner pressure of the motor-side space becomes equal to that of the pump-side space.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2003-300157 filed on Aug. 25, 2003, the disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a fuel vapor leak check module, which detects leakage of fuel vapor generated in a fuel tank, especially relates to a pump and a motor thereof. The pump pressurizes or depressurizes the interior of the fuel tank and the motor drives the pump.

BACKGROUND OF THE INVENTION

In view of protecting the environment, fuel vapor escaping from the fuel tank has been controlled as well as the exhaust emission control. According to the regulation established by the Environmental Protection Agency (EPA) and the California Air Resourced Board (CARB), a leak detection of the fuel vapor flowing out through a small aperture of the fuel tank is strictly required.

A conventional leak check system shown in JP-10-90107A, which is a counterpart of U.S. Pat. No. 5,890,474, has a pump which generate a pressure gradient between an inside and an outside of a fuel tank. When the fuel vapor leaks from the fuel tank, a load of a motor driving the pump fluctuates. The detection of fuel vapor leakage is conducted by checking the fluctuation of the motor load.

For generating the pressure gradient between the inside and the outside of the fuel tank, the interior of the fuel tank must be pressurized or depressurized by the pump. When the pump pressurizes the interior of the fuel tank, if an opening or a hole causing leakage of fuel vapor exists at the fuel tank, the fuel vapor is expelled to the atmosphere through the opening or the hole. To prevent the leakage of the fuel vapor into the atmosphere, the interior of the fuel tank must be depressurized.

The motor has a driving shaft for driving the pump, the driving shaft being supported by a bearing. A lubricant is provided between the driving shaft and the bearing to obtain a smooth rotation of the driving shaft.

When the interior of the fuel tank is depressurized, the inside pressure of the pump decreases and the inside pressure of the motor is kept atmospheric pressure. Thus, the lubricant is introduced into the pump due to the pressure gradient, so that the lubricant adheres to the inner surface of the motor to cause a deterioration of the motor performance.

On the other hand, when the interior of the fuel tank is pressurized, the lubricant is introduced into the motor to deteriorate the motor performance.

SUMMARY OF THE INVENTION

An object of the present invention is to maintain the inner pressure of the pump as same as the inner pressure of the motor, so that the lubricant at the bearing is hardly introduced into the motor or the pump.

According to the present invention, the pump and the motor are isolated from each other by an isolating plate through which a driving shaft of the motor penetrates. The interior space of the pump and the interior space of the motor are communicated with each other through a communicating passage. Thus, the inner pressures of those are substantially equal to prevent the lubricant from flowing between the motor and the pump.

DETAILED DESCRIPTION OF EMBODIMENT

First Embodiment

FIGS. 2 and 3show a fuel vapor leak check system to which a fuel vapor leak check module is applied. The fuel vapor leak check system is referred to as the leak check system, the fuel vapor leak check module is referred to as the leak check module herein after.

The leak check system10includes the leak check module100, a fuel tank20, a canister30, an intake device40, and an ECU50. As shown inFIG. 3, the leak check module100is provided with a housing110, a pump200, brushless motor210, a switching valve300, and a pressure sensor400. The leak check module100is disposed above the fuel tank20and the canister30to prevent a flow of a liquid fuel or other liquid which flows from the fuel tank20into the canister30and the leak check module100.

The housing110comprises a housing body111, and a housing cover112. The housing110accommodates he pump200, the brushless motor210, and the switching valve300. The housing110forms a pump accommodating space120and a valve accommodating space130therein. The pump200and the brushless motor210are disposed in the pump accommodating space120, and the switching valve300is disposed in the valve accommodating space120. The housing body111is provided with a canister port140and an atmospheric vent port150. The canister port140communicates with the canister30through a canister passage141. The atmospheric vent port150communicates with an atmospheric passage151having an open end153at which an air filter152is disposed. The atmospheric passage151communicates with an atmosphere. The housing body111can be made with the housing of the canister30integrally.

As shown inFIG. 2, the housing110has a connecting passage161, a pump passage162, a discharge passage163, a pressure introducing passage164, and a sensor room170. The connecting passage161connects the canister port140with the atmospheric vent port150. The pump passage162connects the connecting passage161with an inlet port201of the pump200. The discharge passage163connects the outlet port202of the pump200to the atmospheric vent port150. The pressure introducing passage164is branched from the pump passage162and connects the pump passage162and the sensor room170. Since the sensor room170communicates with the pressure introducing passage164, the inner pressure of the sensor room170is almost the same as the pressure in the pump passage162.

The discharge passage163is formed between the housing110and the pump200and between the housing110and the brushless motor210in the pump accommodating space120, and is formed between the housing110and the switching valve300in the valve accommodating space130. An air discharged from the outlet port202of the pump flows into a clearance (not shown) between the switching valve300and the housing110through a clearance203between the pump200and the housing110, and a clearance204between the brushless motor210and the housing110. The air flowing into the clearance between the switching valve300and the housing110flows into the atmospheric vent port150along the clearance.

The housing110has an orifice portion500at the side of the canister port140. The orifice portion500has an orifice passage510which branches from the canister passage141. The orifice passage510connects the canister port140with the pump passage162and has an orifice520therein. The orifice520corresponds to the size of an opening for which leakage of fuel vapor is acceptable. For example, the CARB and EPA regulations provide for accuracy of detecting leakage of fuel vapor from fuel tank20. The regulations require that fuel vapor leakage through an opening equivalent to an opening having a diameter of 0.5 mm should be detected. In the present embodiment, the orifice520has a diameter of 0.5 mm or less. The orifice passage510is concentrically formed at the inside of the canister port140, so that the connecting passage161is formed outside and the orifice passage510is formed inside in a shape of a double cylinder.

The pump200having an inlet port201and the outlet port202is provided in the pump accommodating space120. The inlet port201is exposed to the pump passage162and the outlet port is exposed to the discharge passage163. A check valve220is disposed at the vicinity of the inlet port201of the pump200. When the pump is driven, the check valve220is opened. When the pump is not driven, the check valve is closed to restrict the flowing of air-mixed fuel into the pump200.

The pump200is provided with a cover250and a case260to form a housing in which a rotor251is disposed as shown inFIG. 1. The rotor251has a groove in which a vane253is slidablly inserted in a radial direction of the rotor251. The air introduced into the pump chamber through an inlet201is pressurized and is discharged from the outlet202. The inlet201communicates with the fuel tank20through the canister30. Thus, when the pump is operated as a suction pump, the inner pressure of the fuel tank20is reduced.

The pump200is provided with a brushless motor210of which driving shaft211is connected to the rotor251having the vane253. That is, the brushless motor210drives the pump200. The brushless motor210has a casing212which accommodates a stator214on which a coil is wounded, and a rotor216on which a magnet215is disposed. The brushless motor is a DC motor which has no electric contact point, and rotates the rotor216by changing a current applying position to a coil. The brushless motor210is electrically connected to a control circuit280which controls the brushless motor210in a constant speed by controlling electricity from an electric source. The control circuit280is disposed in a clearance204which forms the discharge passage163. The control circuit280includes an electronic part generating heat such as a Zener diode. By disposing the control circuit280in the clearance204, the control circuit280is cooled by air discharged from the pump200.

The switching valve300includes a valve body310, a valve shaft320, and a solenoid actuator330. The valve body310is disposed in the valve accommodating space130. The switching valve300includes an opening-closing valve340and a reference valve350. The opening-closing valve340includes a first valve sheet341and a washer342which is provided on the valve shaft320. The reference valve350includes a second valve sheet351formed on the housing110and a valve cap352fixed on one end of the valve shaft320.

The valve shaft320is actuated by the solenoid actuator330and has the washer342and valve cap352. The solenoid actuator330has a spring331biasing the valve shaft320toward the second valve sheet351. The solenoid actuator330has a coil332which is connected to the ECU50as shown inFIG. 3. The ECU50controls an electric supply to the coil332. When the electric current is not supplied to the coil332, no attracting force is generated between a fixed core333and a movable core334. Thus, the valve shaft320fixed to the movable core334moves downwardly inFIG. 2by biasing force of the spring331so that the valve cap352closes the second valve sheet351. Thereby, the connecting passage161is disconnected from the pump passage162. The washer342opens the first valve sheet341to communicate the canister port140to the atmospheric vent port150through the connecting passage161. Therefore, when the electric current is not supplied to the coil332, the canister port140is disconnected from the pump passage162and the canister port140is communicated to the atmospheric vent port150.

When the electric current is supplied to the coil332according to the signal from the ECU50, the fixed core333attracts the movable core334. The valve shaft320connected with the movable core334moves upwardly against the biasing force of the spring331. The valve cap352opens the second valve sheet351, and the washer342closes the first valve sheet341, whereby the connecting passage161communicates the pump passage162, and the canister port140is disconnected to the atmospheric port150. Therefore, when the coil is energized, the canister port140communicates with the pump passage162and the canister port140disconnects from the atmospheric vent port. The orifice passage510always communicates with the pump passage162, regardless of whether the coil332is energized.

The canister30, as shown inFIG. 3, has therein a fuel vapor adsorbent material31such as activated carbon granules, which adsorbs fuel vapor generated in the fuel tank20. The canister30is disposed between the leak check module100and the fuel tank20. The canister passage141connects the canister30with the leak check module100, and a tank passage32connects the canister30with the fuel tank20. A purge passage33connects the canister31to an intake pipe41of the intake device40. The fuel vapor generated in the fuel tank20is adsorbed by the adsorbent material31while flowing through the canister30. The fuel concentration in the air flowing out from the canister30is less than a predetermined value. The intake pipe31has a throttle valve42therein which controls air amount flowing in the intake pipe31. The purge passage33has a purge valve34which opens and closes the purge passage33according to the signal from the ECU50.

The pressure sensor400, as shown inFIG. 2, is disposed in the sensor room170. The pressure sensor400detects the pressure in the sensor room170and outputs signals to the ECU170according to the detected pressure. The sensor room170communicates with the pump passage162through the pressure introducing passage164. Thus, the pressure in the sensor room170is substantially equal to the pressure in the pump passage162. The pressure sensor400is disposed far from the pump200by which pressure fluctuation caused by the pump200is more reduced than the case in which the pressure sensor400is disposed close to the inlet port201of the pump200. Therefore, the pressure sensor400detects the pressure in the sensor room170more precisely.

The ECU50is comprised of microcomputer, which has CPU, ROM, and RAM (not shown) and controls the leak check module100and other components on the vehicle. The ECU50receives multiple signals from sensors to execute control programs memorized in ROM. The brushless motor210and the switching valve300are also controlled by the ECU50.

The structures of the pump200and brushless motor210are described herein after.

The pump200and the brushless motor210are accommodated in the pump accommodating space120. The pump200has the cover250and the case260between which a flange230is disposed as shown inFIGS. 1 and 2. The cover250, the case260and the flange230are integrally assembled by a bolt270.

The cover250has a cup portion254in which the rotor251and the vane253are disposed. The cup portion254is covered by the case260at the side opposite to the brushless motor210. A clearance is formed between the driving shaft211and the cover250, whereby the interior of the cup portion254communicates to a space formed between the cover250and the flange230. The interior of the cup portion254, the clearance between the shaft211and the cover250, and the space between the cover250and the flange230form a pump-side space255.

The brushless motor210has the casing212which accommodates the stator214and the rotor216. The casing212is attached to the flange230to form a motor-side space217therein. The motor-side space217is isolated from the pump-side space255by the casing212, a wall212aof the casing212, and the flange230, which comprise an isolating plate. The driving shaft211of the brushless motor210penetrates the wall212aand the flange230.

As shown inFIGS. 1 and 4, the flange230has an inner hole231into which an end portion212bof the casing212is inserted. The end portion212bis cylindrically shaped, into which a bearing240is press-fitted. The bearing240rotatably supports the driving shaft211. The bearing240has a concave portion241abetween an inner surface241of the bearing240and the outer surface of the driving shaft211. A lubricant is provided in the concave portion241a.

As shown inFIG. 6, the bearing240has a plurality of grooves243at the outer periphery thereof in a constant interval or inconstant interval. The groove243extends in an axial direction of the bearing240. The cross section of the groove243is semi-circle. The inner surface212cof the casing212confronts the groove243to form a communicating passage244which is semi-cylindrical. One end of the communicating passage244is opened in the pump-side space255and another end is opened in the motor-side space217. That is, the pump-side space255and the motor-side space217communicate with each other through the communicating passage244.

When the pump200is driven by the brushless motor210, the internal pressure of the pump-side space255is reduced. Thus, the internal pressure of the motor-side space217is to become higher than the internal pressure of the pump-side space255, so that a suction force is to be generated from the motor-side space217toward the pump-side space255. However, the motor-side space217and the pump-side space255are communicated with each other through the communicating passage244. Therefore, each of the inner pressure of both spaces217,255becomes substantially equal to each other. The lubricant in the bearing240does not flow out into the pump-side space255.

In another embodiment, the pump200can be a pump which pressurizes the interior of the fuel tank20. The pressure in the pump-side space255is to become higher than that in the motor-side space217. However, because the space217communicates with the space255, the inner pressure of both spaces become equal to keep the lubricant in the concave portion241a, not to generate flowing of lubricant toward the motor-side space217.

The operation of the leak check module100is described herein after.

When a predetermined period elapses after the engine is turned off, the fuel vapor leak check is conducted. The predetermined period is set to stabilize the vehicle temperature. While the engine is running and until the predetermined period elapses after the engine is turned off, the fuel vapor leak check by the leak check module100is not conducted. The coil332is not energized, and the canister port140and the atmospheric vent port150are connected with each other through the connecting passage161. The fuel vapor fraction of the fuel vapor/air mixture adsorbs in the canister30. Then, the air fraction is expelled from the opening end153of the atmospheric passage151. At this moment, the check valve220is closed, air including fuel vapor generated in the fuel tank20is prevented from flowing into the pump200.

(1) When the predetermined period elapses after the engine is turned off, an atmospheric pressure is detected prior to the fuel vapor leak check. That is, since the fuel vapor leak check is conducted based on the pressure change with the pressure sensor400, it is necessary to reduce an atmospheric effect due to altitude. When the coil332is not energized, the atmospheric vent port150communicates with the pump passage162through the orifice passage510. Because the sensor room170communicates with the pump passage162through the pressure introducing passage164, the pressure in the sensor room170is substantially equal to the atmospheric pressure. The atmospheric pressure detected by the pressure sensor400is converted to a pressure signal, the pressure signal being output to the ECU50. The pressure signal from the pressure sensor400is outputted as a ratio of voltage, a duty ratio, or a bit output. Thus, the noise effect generated by the solenoid actuator330or other electric actuators can be reduced to maintain the detection accuracy of the pressure sensor400. At this moment, only the pressure sensor400is turned on and the brushless motor210and the switching valve300are turned off. This state is indicated as an atmospheric pressure detection period A inFIG. 7. The pressure detected in the sensor room170is equal to the atmospheric pressure.

(2) After the atmospheric pressure is detected, the altitude at which the vehicle is parked is calculated according to the detected atmospheric pressure. For example, the altitude is calculated based on a map showing a relationship between the atmospheric pressure and the altitude, which is memorized in ROM of the ECU50. The other parameters are corrected according to the calculated altitude. The calculation and the correction above are executed by ECU50.

After the correction of parameters is executed, the coil332of the switching valve300is energized of which state is indicated as a fuel vapor detection period B inFIG. 7. Since the coil332is energized, the fixed core333attracts the movable core334so that the washer342closes the first valve sheet341and the valve cap352opens the second valve sheet351. The atmospheric vent port150disconnects from the pump passage162, and the canister port140connects to the pump passage162. As a result, the sensor room170connected to the pump passage162is connected with the fuel tank20through the canister30. The pressure in the fuel tank20is larger than the ambient pressure due to the fuel vapor. The pressure detected by the pressure sensor400is slightly larger than the atmospheric pressure as shown inFIG. 7.

(3) When the increment of the pressure in the fuel tank20is detected, the coil332of the switching valve300is deenergized. This state is indicated as a reference detection range C inFIG. 7. The moving core334and the valve shaft320move in biasing direction of the spring331so that the washer342opens the first valve sheet341and the valve cap352closes the second valve sheet351. The pump passage162communicates with the canister port140and the atmospheric vent port150through the orifice passage510. The canister port140communicates with the atmospheric vent port150through the connecting passage161.

When the brushless motor210is energized, the pump200is driven to reduce the pressure in the pump passage162, so that the check valve220is opened. The air flowing into the canister port140from atmospheric vent port150and air/fuel mixture flowing from the canister port140flow into the pump passage162through the orifice passage510. Because the air flowing into the pump passage162is restricted by the orifice520in the orifice passage510, the pressure in the pump passage162is decreased as shown inFIG. 7. Since the orifice520has a constant aperture, the pressure in the pump passage162is decreased to a reference pressure Pr, which is memorized in RAM of the ECU50. After the reference pressure Pr is detected, the brushless motor210is deenergized.

(4) When the detection of reference pressure is finished, the coil332of the switching valve300is energized again. The washer342closes the first valve seat341and the valve cap352opens the second valve sheet351, so that the canister port140communicates with the pump passage162. That is, the fuel tank20communicates with the pump passage162, so that the pressure in the pump passage162becomes equal to the pressure in the fuel tank20. The pressure in the fuel tank20is almost the atmospheric pressure. The brushless motor210is energized again to drive the pump and to open the check valve220so that the pressure in the fuel tank20decreases. The pressure in the sensor room170, which is detected by the pressure sensor400, decreases gradually. This state is illustrated as decompression range D inFIG. 7.

While the pump200is operated, when the pressure in the sensor room170, which is equal to the pressure in the fuel tank20, becomes under the reference pressure Pr, it is determined that the amount of fuel vapor leakage is under the permissible value. In other words, no air is introduced into the fuel tank20from outside, or amount of air introducing into the fuel tank is less than the amount which is equivalent to the orifice leakage. Therefore, it is determined that the sealing of the fuel tank20is enough.

On the other hand, when the pressure in the fuel tank20does not decrease to the reference pressure Pr, it is determined that the amount of fuel vapor leakage is over the permissible value. It is likely that the outside air is introduced into the fuel tank20during the depressurization. Therefore, it is determined that the sealing of the fuel tank20is not enough. In this case, it is likely that the fuel vapor in the fuel tank20escapes over the permissible value. When it is determined that impermissible amount of fuel vapor leakage exists, a warning lamp on a dashboard (not shown) is turned on to notify the driver of fuel vapor leakage at a successive operation of the vehicle.

When the pressure in the fuel tank20is almost equal to the reference pressure Pr, it means that the fuel vapor leakage arises, the fuel vapor leakage being equivalent to the fuel vapor leakage through the orifice520.

(5) When the detection of fuel vapor leakage is finished, the brushless motor210and the switching valve300are turned off. This state is illustrated as a range E inFIG. 7. In the ECU50, it is confirmed that the pressure in the pump passage162is recovered to the atmospheric pressure as shown inFIG. 7. Then, the pressure sensor400is turned off to finish the all-detecting step.

In the first embodiment, the communicating passage244communicates the pump-side space255with the motor-side space217to equalize the inner pressure of both spaces255,217. Therefore, the lubricant in the concave portion241ais prevented from flowing out toward the pump-side space200.

The communicating passage244is formed between the groove243and the inner surface212cof the casing212. That is, the communicating passage244is formed only by making a groove243without machining the casing212and the flange230.

Multiple communicating passages244are arranged in the circumferential direction on the bearing240. Although the depth of the groove243is small, enough of area of the communicating passage244is obtained by a summation of each area of the communicating passage244. Because it is needless to make the depth of the groove244large to obtain the enough area of communicating passage244, a deterioration of the strength of the bearing240is restricted.

Modification of the First Embodiment

FIG. 8shows a modification of the first embodiment. In this modification, eight communicating passages244are provided between the bearing240and the casing212in a constant interval. The interval can be inconstant.

FIG. 9shows another modification. The cross section of the groove243is substantially rectangle instead of semi-circle.

FIG. 10shows another modification. The cross section of the groove243is substantially triangle.

Second Embodiment

FIG. 11shows a part of brushless motor of the second embodiment. The same parts and components as those in the first embodiment are indicated with same reference numerals and the same descriptions are not reiterated. The bearing240is press-fitted into the flange230instead of the casing212. The communication passage244is formed between the bearing240and the flange230. The flange230can support the bearing240.

Third Embodiment

FIG. 12shows a flange600viewed from the side of pump200. The bearing240is inserted into an inner hole610of a flange600as well as the second embodiment. The outer surface of the bearing240is a continuous surface without any grooves. On the other hand, the flange600has four grooves620at an inner periphery thereof in constant interval. The communicating passages640are made between the flange600and the bearing240to communicate the motor-side space217with the pump-side space255.

When the pump200is driven, the pressure gradient arises between the motor-side space217and the pump-side space255. The communicating passage640communicates both spaces217,255, so that the pressure gradient is diminished to the same pressure. The lubricant in the concave portion241ais prevented from flowing out toward the pump-side space255.

In the third embodiment, because the grooves620are formed on the flange600, a complicated shape of the bearing240can be avoided.

Fourth Embodiment

FIG. 13shows a brushless motor and the pump of the fourth embodiment. The same parts and components as those in the first embodiment are indicated with same reference numerals and the same descriptions are not reiterated. The communicating passage710is formed in such a manner that the communicating passage710penetrates the flange700. The communicating passage710can be positioned at any position of the flange700in which the motor-side space217communicates with the pump-side space255.

Another Modification

As shown inFIG. 14, the communicating passage211acan be made in the driving shaft211, which communicates the motor-side space217with the pump-side space255.

The same parts and components as those in the first embodiment are indicated with same reference numerals and the same descriptions are not reiterated.

In the embodiments described above, the brushless motor is used and the vane-type pump is used. The motor is not limited to the brushless motor but conventional DC motor or an induction motor can be used. A turbine-type pump or impeller-type pump can be used.

Each of the embodiments can be combined to achieve the effect of the present invention.