Power steering device

• US 20040182640A1
• Filed: 02/04/2004
• Published: 09/23/2004
• Est. Priority Date: 03/18/2003
• Status: Active Grant

• Current Assignee: Toyoda Koki Kabushiki Kaisha
• Original Assignee: Toyoda Koki Kabushiki Kaisha
• Inventors: Katou, Hideki, Asada, Atsuhisa
• Granted Patent: US 6,983,817 B2
• Time in Patent Office: Days
• US Class Current: 180/446
• CPC Class Codes: B62D 5/049 detecting sensor failures
• CPC Class Codes: B62D 6/10 characterised by means for sensing or determining torque

Abstract

A power steering device is provided which is capable of preventing a wrong operation from occurring in a steering control state even when an initial torque of torque detection means was not detected normally due to a human error. Upon receipt of a trigger signal, a CPU reads an initial setting program from a program storage area of a ROM and executes the initial setting program in the following order of steps. That is, the CPU detects by torque detection means an initial torque which is generated primarily by the cause of the difference between origin positions of a pair of resolvers 12, 12 which together with a torsion bar constitutes the torque detection means. Then, the CPU operates an assist motor to rotate a steering handle from a neutral position a predetermined rotational angle in one direction about the handle axis to stop the steering handle at a first judgment position and detects a first judgment torque value by the torque detection means with the steering handle being stopped at the first judgment position. Then, the CPU rotates the steering handle from the neutral position the same angular position in the other direction to stop the steering handle at a second judgment position and detects a second judgment torque value by the torque detection means with the steering handle being stopped at the second judgment position. Further, the CPU judges whether the initial torque has been detected normally or not, based on the first and second judgment torque values.

Claims

1. A power steering device of the type wherein a steering torque applied to a handle shaft through a steering handle is detected by torque detection means which is provided with a torsion bar and a pair of angle detection sensors arranged apart from each other in the axial direction of said torsion bar and wherein a drive power corresponding to said steering torque is applied from assist power generating means to steerable wheels, said power steering device comprising:

initial torque detection command means for issuing a command to detect an initial torque which is generated primarily by the cause of the difference between origin positions of said pair of angle detection sensors; and

initial torque judgment command means for detecting a first judgment torque value by said torque detection means, with said steering handle being stopped at a first judgment position after being rotated by said assist power generating means form a neutral position a predetermined rotational angle in one direction about the handle axis;

then for detecting a second judgment torque value in the same manner, with said steering handle being stopped at a second judgment position after being rotated the same rotational angle from said neutral position in the other direction; and

for issuing a command to judge whether said detected initial torque is normal or not, based on said first and second judgment torque values.

2. The power steering device as set forth in claim 1, wherein:

a predetermined time interval is set in said initial torque judgment command means for detecting said first and second judgment torque values.

3. The power steering device as set forth in claim 1, wherein:

said initial torque judgment command means calculates the sum of first and second net applied torque values which are led from said first and second judgment torque values, to cancel positive and negative-going torque values each other;

judges that said detected initial torque is normal, when said sum of said both net applied torque values is within a predetermined range; and

further judges that said detected initial torque is abnormal, when said sum of said both net applied torque values is not within said predetermined range.

4. A power steering device of the type wherein a steering torque applied to a handle shaft through a steering handle is detected by torque detection means which is provided with a torsion bar and a pair of angle detection sensors arranged apart from each other in the axial direction of said torsion bar and wherein a command signal is issued from a steering control section for applying a drive power corresponding to said steering torque from an electric motor as assist power generating means to steerable wheels, said power steering device comprising:

initial torque detection command means for issuing a command to detect an initial torque which is generated primarily by the cause of the difference between origin positions of said pair of angle detection sensors; and

initial torque judgment command means for detecting a first judgment torque value by said torque detection means, with said steering handle being stopped at a first judgment position after being rotated by said electric motor from a neutral position a predetermined rotational angle in one direction about the handle axis;

then for detecting a second judgment torque value in the same manner, with said steering handle being stopped at a second judgment position after being rotated from said neutral position the same rotational angle in the other direction; and

for issuing a command to judge whether said detected initial torque is normal or not, based on said first and second judgment torque values;

initial torque storage command means for issuing a command to store said initial torque as a compensation value for said steering torque in initial torque storage means of said steering control section when-said initial torque is normal; and

abnormality reporting command means for issuing a command to report an abnormality when said initial torque is abnormal.

5. The power steering device as set forth in claim 4, wherein:

said initial torque detection command means, said initial torque judgment command means, said initial torque storage command means and said abnormality reporting command means are stored along with an initial setting program in said steering control section; and

said initial setting program is able to be initiated in response to a particular trigger signal transmitted from an external device which is provided other than a vehicle installing said power steering device thereon.

6. The power steering device as set forth in claim 4, wherein:

a predetermined time interval is set in said initial torque judgment command means for detecting said first and second judgment torque values.

7. The power steering device as set forth in claim 4, wherein:

said initial torque judgment command means calculates the sum of first and second net applied torque values which are led from said first and second judgment torque values, to cancel positive and negative-going torque values each other;

judges that said detected initial torque is normal, when said sum of said both net applied torque values is within a predetermined range; and

further judges that said detected initial torque is abnormal, when said sum of said both net applied torque values is not within said predetermined range.

8. A power steering device of the type wherein a steering torque applied to a handle shaft through a steering handle is detected by torque detection means which is provided with a torsion bar and a pair of angle detection sensors arranged apart from each other in the axial direction of said torsion bar, and wherein a drive power corresponding to said steering torque is applied from assist power generating means to steerable wheels, said power steering device further including initial torque detection command means which comprises:

first torque detection means for rotating said steering handle by said assist power generating means a predetermined rotational angle in one direction about the handle axis to a first position after said steering handle is held stationarily at a neutral position in the steering direction and for detecting a first torque value by said torque detection means with said steering handle being stopped at said first position, said first torque value including a residual torque which exists as hysteresis between said steering handle and said torque detection means;

second torque detection means for rotating said steering handle from said neutral position the same rotational angle in the other direction and for detecting a second torque value also including another residual torque, with said steering handle being stopped at said second position; and

initial torque setting means for calculating an average value of the first and second torque values to cancel positive and negative-going residual torques included in said first and second torque values and for setting said calculated average value as an initial torque which is generated by the cause of the difference between origin positions of said pair of angle sensors.

9. The power steering device as set forth in claim 8, wherein:

a predetermined time interval is set in said initial torque detection command means for detecting said first and second judgment torque values.

10. The power steering device as set forth in claim 8, wherein:

said initial torque detection command means detects each of said first and second torque values plural times with or without altering the rotational angle of said steering handle.

11. A power steering device of the type wherein a steering torque applied to a handle shaft through a steering handle is detected by torque detection means which is provided with a torsion bar and a pair of angle detection sensors arranged apart from each other in the axial direction of said torsion bar and wherein a command signal is issued from a steering control section for applying a drive power corresponding to said steering torque from an electric motor as assist power generating means to steerable wheels, said power steering device comprising:

initial torque detection command means including;

(a) first torque detection means for rotating said steering handle a predetermined rotational angle in one direction about the handle axis to a first position after said steering handle is held stationarily at a neutral position in the steering direction and for detecting a first torque value by said torque detection means with said steering handle being stopped at said first position, said first torque value including a residual torque which exists as hysteresis between said steering handle and said torque detection means;

(b) second torque detection means for rotating said steering handle by said electric motor from said neutral position the same rotational angle in the other direction and for detecting a second torque value, also including another residual torque, by said torque detection means with said steering handle being stopped at said second position; and

(c) initial torque setting means for calculating an average value of said first and second torque values to cancel positive and negative-going residual torques included said first and second torque values and for setting said calculated average value as an initial torque which is generated by the cause of the difference between origin positions of said pair of angle sensors; and

initial torque storage command means for issuing a command to store said initial torque as a compensation value for said steering torque in initial torque storage means of said steering control section.

12. The power steering device as set forth in claim 11, wherein:

said initial torque detection command means and said initial torque storage command means are stored along with an initial setting program in said steering control section; and

said initial setting program is able to be initiated in response to a particular trigger signal transmitted from an external device which is provided other than a vehicle installing said power steering device thereon.

13. The power steering device as set forth in claim 11, wherein:

a predetermined time interval is set in said initial torque command means for detecting said first and second judgment torque values.

14. The power steering device as set forth in claim 11, wherein:

said initial torque detection command means detects each of said first and second torque values plural times with or without altering the rotational angle of said steering handle.