Evaporative emission leak detection system with brushless motor

• US 20040000187A1
• Filed: 06/12/2003
• Published: 01/01/2004
• Est. Priority Date: 06/28/2002
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Kobayashi, Mitsuyuki, Nagasaki, Kenji, Kano, Masao, Yamada, Yoshichika
• Granted Patent: US 7,004,013 B2
• Time in Patent Office: Days
• US Class Current: 73/49.7
• CPC Class Codes: F02M 25/0809 Judging failure of purge control system

Abstract

An evaporative emission leak detection system provides for detecting a leakage of a fuel vapor evaporating in a fuel tank by using a pressure difference between an inside and outside of the fuel tank. The system includes a pump for providing the pressure difference between the inside and outside of the fuel tank, a brushless motor for operating the pump, a first passage connecting to the fuel tank, a second passage connecting to the outside of the fuel tank, and a switching device for switching connections between the pump and at least one of the first passage and the second passage. The first passage has an adsorbent for adsorbing the fuel vapor. This system ensures a long life time and high accuracy of the leak detection.

Claims

1. An evaporative emission leak detection system for detecting a leakage of a fuel vapor evaporating in a fuel tank, the system comprising:

a pump for providing a pressure difference between an inside and outside of the fuel tank;

a brushless motor for operating the pump;

a first passage having an adsorbent for adsorbing the fuel vapor, the first passage connecting to the fuel tank;

a second passage connecting to the outside of the fuel tank; and

a switching means for switching connections between the pump and at least one of the first passage and the second passage.

2. The evaporative emission leak detection system according to claim 1,

wherein the pump and the brushless motor are disposed in space, where the fuel vapor is filled.

3. The evaporative emission leak detection system according to claim 1, further comprising:

a throttle disposed between the second passage and the pump for throttling air flow at a predetermined amount.

4. The evaporative emission leak detection system according to claim 1,

wherein the pump depressurizes air in the fuel tank at least below the atmospheric pressure.

5. The evaporative emission leak detection system according to claim 1, further comprising:

a detecting means disposed in a passage between the pump and the switching means for detecting a pressure.

6. The evaporative emission leak detection system according to claim 1, further comprising:

a load detecting means for detecting a load of the brushless motor as an operation characteristic of the pump.

7. The evaporative emission leak detection system according to claim 6,

wherein the load detecting means detects current of the brushless motor or rotation speed of the brushless motor as the load of the brushless motor.

8. The evaporative emission leak detection system according to claim 6,

wherein the load detecting means outputs information about the operation characteristic of the pump by using at least one of a voltage ratio signal, a duty ratio signal, and a bit output signal.

9. The evaporative emission leak detection system according to claim 1,

wherein the brushless motor is operated with a constant rotation speed control.

10. The evaporative emission leak detection system according to claim 1,

wherein the pump and the brushless motor are disposed at a higher position than the fuel tank and the adsorbent.

11. The evaporative emission leak detection system according to claim 1,

wherein the switching means is supplied with a holding electric power when the switching means maintains its operation,

and the holding electric power is smaller than an electric power in a case where the switching means starts to operate.

12. The evaporative emission leak detection system according to claim 1,

wherein the brushless motor is operated with a constant voltage control.

13. The evaporative emission leak detection system according to claim 1,

wherein the brushless motor is operated with a constant current control.

14. The evaporative emission leak detection system according to claim 1,

wherein the pump pressurizes air in the fuel tank at least above the atmospheric pressure.

15. The evaporative emission leak detection system according to claim 3,

wherein the throttle provides an air flow corresponding to a leakage opening at φ

0.5 mm and less.

16. The evaporative emission leak detection system according to claim 1, further comprising:

a throttle disposed between the second passage and the pump; and

a detecting means disposed in the passage between the pump and the switching means for detecting a pressure,

wherein the pump depressurizes air in the fuel tank at least below the atmospheric pressure,

the throttle throttles air flow at a predetermined amount so that a pressure in a passage between the pump and the switching means is decreased to a reference pressure and is stabilized at the reference pressure when the first and second passages connect to the pump only through the throttle and the pump depressurizes the air in the passage,

and the detecting means detects the atmospheric pressure, the fuel vapor pressure, and the reference pressure.

17. The evaporative emission leak detection system according to claim 16, further comprising:

a microcomputer for controlling the switching means, the detecting means, and the brushless motor,

wherein the pressure in the passage between the pump and the switching means is decreased to a leak detection pressure when the fuel tank connects to the pump through the first passage and the pump depressurizes air in the fuel tank,

and the microcomputer determines that the leakage of the fuel vapor exceeds the predetermined amount of the air flow limited by the throttle when the leak detection pressure becomes larger than the reference pressure.