Electric power assist module for steering system

• US 20080264713A1
• Filed: 05/09/2007
• Published: 10/30/2008
• Est. Priority Date: 04/24/2007
• Status: Active Grant

• Current Assignee: JTEKT India Ltd.
• Original Assignee: SONA KOYO Steering Systems Limited
• Inventors: Deshmukh, Kiran Manohar, Sharma, Ravindra Nath
• Granted Patent: US 7,789,191 B2
• Time in Patent Office: Days
• US Class Current: 180/446
• CPC Class Codes: B62D 5/0406 including housing for electronic control unit
• CPC Class Codes: B62D 5/0412 the axes of motor and steering column being parallel

Abstract

An electric power assist module for a steering system has an integrated housing for accommodating the torque sensor, motor and electronic control unit. A helical gear train including a pinion gear, an intermediate gear and steering gear are provided to transfer the motion from the motor to an output shaft that is coupled to an input shaft by way of a torsion bar.

Claims

1. An electric power assist module for a steering system, with the electric power assist module comprising:

an integrated housing;

a torque sensor that is at least partially contained by the integrated housing;

a motor that is at least partially contained by the integrated housing;

an electronic control unit that is at least partially contained by the integrated housing;

an input shaft;

an output shaft;

a torsion bar having opposite first and second ends, wherein the first end of the torsion bar is connected to the input shaft so that the first end of the torsion bar rotates with the input shaft, and the second end of the torsion bar is connected to the output shaft so that the second end of the torsion bar rotates with the output shaft; and

a reduction gear assembly for transferring motion from the motor to the output shaft, wherein the reduction gear assembly comprises a helical gear train including a pinion gear, an intermediate gear and a steering gear.

2. The electric power assist module according to claim 1, comprising a lower housing that is mounted to the integrated housing, wherein the lower housing at least partially contains the helical gear train.

3. The electric power assist module according to claim 2, comprising an upper cover mounted to the integrated housing, wherein the input shaft is rotatably mounted to the upper cover so that the input shaft is aligned with the output shaft.

4. The electric power assist module according to claim 2, comprising a cover, wherein:

the integrated housing defines a cavity with an opening;

the cover substantially hermetically closes the opening; and

the electronic control unit is positioned in the cavity.

5. The electric power assist module according to claim 2, wherein wiring of the electronic control unit is provided with a substantially water-proof connector that is on the integrated housing.

6. The electric power assist module according to claim 2, wherein:

the motor comprises a drive shaft;

the pinion gear is carried by a carrying shaft having opposite first and second ends;

the first end of the carrying shaft is mated to the drive shaft; and

the second end of the carrying shaft is supported in the lower housing.

7. The electric power assist module according to claim 2, wherein:

the pinion gear is meshed with the intermediate gear;

the intermediate gear is meshed with the steering gear;

the intermediate gear is carried by a carrying shaft having opposite first and second ends;

the first end of the carrying shaft is supported in the integrated housing;

the second end of the carrying shaft is supported in the lower housing; and

the steering gear is press fit onto the output shaft.

8. The electric power assist module according to claim 2, comprising a first bearing and a second bearing, wherein:

the first bearing is supported by the integrated housing;

the second bearing supported by the lower housing; and

the output shaft is rotatably carried by each of the first and second bearings.

9. The electric power assist module according to claim 1, wherein:

the input shaft and the output shaft are operatively associated with one another via a cavity being in receipt of a profile; and

the cavity and the profile are cooperative for allowing, yet restricting to a predetermined limit, relative rotation between the input shaft and the output shaft.

10. The electric power assist module according to claim 1, wherein:

the electronic control unit comprises a processing apparatus;

the processing apparatus is operatively associated with the torque sensor for receiving signals indicative of torque applied to the input shaft;

the processing apparatus is operative for generating a pulse width modulation signal that is proportional to the torque applied to the input shaft; and

the motor operates responsively to the pulse width modulation signal.

11. The electric power assist module according to claim 3, wherein:

the motor extends through an opening in the upper cover; and

a seal is provided between the motor and the upper cover for providing a substantially hermetic seal between the upper cover and the motor.

12. The electric power assist module according to claim 1 in combination with at least:

an upper shaft, a lower shaft, a rack and pinion mechanism, and a steering shaft, wherein

the upper shaft comprises two universal joints;

the lower shaft comprises two universal joints;

the upper shaft is positioned between and connected to each of the steering shaft and the input shaft;

the lower shaft is positioned between and connected to each of the output shaft and a pinion gear of the rack and pinion mechanism; and

axes of the pinion gear of the rack and pinion mechanism, the input shaft, the output shaft and the steering shaft are in different planes.

13. The electric power assist module according to claim 9, wherein the cavity and the profile are each substantially triangular.

14. The electric power assist module according to claim 1, wherein:

the torque sensor is for providing a signal that is indicative of torque applied to the input shaft;

the electronic control unit is for providing a pulse width modulation signal in response to at least the signal from the torque sensor; and

the motor is for driving the reduction gear assembly in response to at least the pulse width modulation signal.

15. The electric power assist module according to claim 1, wherein the first end of the torsion bar being connected to the input shaft, so that the first end of the torsion bar rotates with the input shaft, comprises:

a dowel mounted to both the first end of the torsion bar and the input shaft.

16. The electric power assist module according to claim 1, wherein the second end of the torsion bar being connected to the output shaft, so that the second end of the torsion bar rotates with the output shaft, comprises:

a dowel mounted to both the second end of the torsion bar and the output shaft.

17. The electric power assist module according to claim 1, wherein:

the pinion gear is connected to a drive shaft of the motor so that the pinion gear rotates with the drive shaft;

the pinion gear is meshed with a first gear of the intermediate gear;

the steering gear is meshed with a second gear of the intermediate gear;

the first gear of the intermediate gear is connected to the second gear of the intermediate gear so that the second gear of the intermediate gear rotates with the first gear of the intermediate gear; and

the steering gear is connected to the output shaft so that the output shaft rotates with the steering gear.

18. An electric power assist module for a steering system, with the electric power assist module comprising:

a housing including

(a) an upper chamber,

(b) a lower chamber,

(c) a side chamber that is beside and contiguous with at least one chamber selected from the group consisting of the upper chamber and the lower chamber, and

(d) a passageway between the upper chamber and the side chamber;

a torque sensor that is at least partially contained by the upper chamber of the housing;

a motor that is at least partially contained by the upper chamber of the housing;

an electronic control unit that is at least partially contained by the side chamber of the housing, wherein at least one electrical connection between the electronic control unit and at least one component, which is selected from the group consisting of the torque sensor and the motor, extends through the passageway of the housing;

an input shaft;

an output shaft;

a torsion bar having opposite first and second ends, wherein the first end of the torsion bar is connected to the input shaft so that the first end of the torsion bar rotates with the input shaft, and the second end of the torsion bar is connected to the output shaft so that the second end of the torsion bar rotates with the output shaft; and

a reduction gear assembly at least partially positioned in the lower chamber of the housing, wherein the motor drives the output shaft by way of the reduction gear assembly.

19. The electric power assist module according to claim 18, wherein:

the torque sensor is fully enclosed within the upper chamber;

the electronic control unit is fully enclosed within the side chamber;

the reduction gear assembly comprises a pinion gear, an intermediate gear and a steering gear; and

each of the pinion gear, the intermediate gear and the steering gear is fully enclosed in the lower chamber of the housing.

20. The electric power assist module according to claim 18, wherein:

the upper chamber comprises

(a) at least an upper portion of a main section of the housing, and

(b) an upper cover;

the upper portion of the main section defines an upwardly oriented opening that is at least partially closed by the upper cover;

the lower chamber comprises

(a) a lower portion of the main section of the housing, and

(b) a lower cover;

the lower cover defines an upwardly oriented opening that is at least partially closed by the lower portion of the main section;

the side chamber comprises

(a) a side section of the housing, and

(b) a side cover; and

the side section of the housing defines a side opening that is at least partially closed by the side cover.