Steering system for vehicle

• US 20050224277A1
• Filed: 04/04/2005
• Published: 10/13/2005
• Est. Priority Date: 04/07/2004
• Status: Active Grant

• Current Assignee: Jtekt Corporation (Toyota Motor Corporation)
• Original Assignee: Toyoda Koki Kabushiki Kaisha
• Inventors: Kato, Hiroaki, Takeuchi, Shinji, Ohno, Akihiro, Momiyama, Minekazu, Murakami, Tsuyoshi
• Granted Patent: US 7,257,474 B2
• Time in Patent Office: Days
• US Class Current: 180/422
• CPC Class Codes: B60W 10/10 including control of change-speed gearings
• CPC Class Codes: B60W 10/20 including control of steering systems
• CPC Class Codes: B62D 5/008 Changing the transfer ratio between the steering wheel and the steering gear by variable supply of energy, e.g. by using a superposition gear
• CPC Class Codes: B62D 6/007 adjustable by the driver, e.g. sport mode
• CPC Class Codes: B62D 6/008 Control of feed-back to the steering input member, e.g. simulating road feel in steer-by-wire applications
• CPC Class Codes: B62D 6/04 responsive only to forces disturbing the intended course of the vehicle, e.g. forces acting transversely to the direction of vehicle travel

Abstract

In a steering system 30, a transmission ratio R1 which is determined in dependence on the vehicle speed by reference to a transmission ratio decision map is multiplied with a first transmission ratio alteration gain g10 which is determined in dependence on the distribution of a traveling drive torque from an engine 11 to front wheels 14 and rear wheels 15, thereby to alter the ratio R1 of steering torque distribution from a steering handle 31 to the front wheels 14, whereby the variation of the steering feeling due to an increase or decrease in the distribution of the traveling drive torque to the front wheels 14 can be suppressed. Further, the transmission ratio R1 is multiplied with a second transmission ratio alteration gain g11 which is determined in dependence on the gradient of the road surface by reference to a second transmission ratio alteration map, thereby to alter the transmission ratio R1, whereby the variation of the steering feeling due to the variation of the gradient can also be suppressed.

Claims

1. A steering system wherein the transmission ratio of motion between a steering handle and steerable wheels is altered in dependence on the traveling state of a vehicle, the steering system comprising:

a steering mechanical train for transmitting the motion of the steering handle to the steerable wheels at a variable transmission ratio;

judgment means for judging whether the vehicle is in ascent traveling, descent traveling or horizontal traveling; and

transmission ratio alteration means for altering the transmission ratio so that when the vehicle is judged by the judgment means to be in ascent traveling, the manipulation amount of the steering handle necessary to steer the steerable wheels is decreased compared with that in horizontal traveling and so that when the vehicle is judged by the judgment means to be in descent traveling, the manipulation amount of the steering handle necessary to steer the steerable wheels is increased compared with that in horizontal traveling.

2. A steering system as set forth in claim 1, further comprising:

a transmission ratio decision map storing various transmission ratios in correlation with various vehicle speeds as representative of the traveling state;

a transmission ratio alteration map storing various transmission alteration gains in correlation with various gradients in ascent traveling and descent traveling; and

wherein;

the transmission ratio alteration means is constructed to alter the transmission ratio by multiplying a transmission ratio which is determined in dependence on the vehicle speed by reference to the transmission ratio decision map, with a transmission ratio alteration gain which is determined in dependence on the gradient by reference to the transmission ratio alteration map.

3. A steering system wherein the transmission ratio of motion between a steering handle and steerable wheels is altered in dependence on the traveling state of a vehicle, the system comprising:

a steering mechanical train for transmitting the motion of the steering handle to the steerable wheels in a variable responsiveness;

judgment means for judging whether the vehicle is in ascent traveling, descent traveling or horizontal traveling; and

responsiveness alteration means for controlling the steering mechanical train to alter the responsiveness of the steered angle of the steerable wheels to the manipulation amount of the steering handle; and

wherein;

the responsiveness alteration means operates to heighten the responsiveness compared with that in horizontal traveling of the vehicle when the vehicle is judged by the judgment means to be in ascent traveling and to lower the responsiveness compared with that in horizontal traveling of the vehicle when the vehicle is judged by the judgment means to be in descent traveling.

4. A steering system as set forth in claim 3, further comprising:

a responsiveness decision map storing various steered angle control gains of the steerable wheels relative to the manipulation amount of the steering handle in correlation with various vehicle speeds;

a responsiveness alteration map storing various responsiveness alteration gains in correlation with various gradients in ascent traveling and descent traveling; and

wherein;

the responsiveness alteration means alters the responsiveness by multiplying a steered angle control gain which is determined in dependence on the vehicle speed by reference to the responsiveness decision map, with a responsiveness alteration gain which is determined in dependence on the gradient by reference to the responsiveness alteration map.

5. A steering system wherein the assist force for the manipulation of a steering handle provided in a vehicle is altered in dependence on a steering torque applied to the steering handle, the steering system comprising:

a steering mechanical train for transmitting the motion of the steering handle to the steerable wheels and for generating an assist force of the steering manipulation of the steering handle;

a torque sensor for detecting a steering torque applied to the steering handle;

judgment means for judging whether the vehicle is in ascent traveling, descent traveling or horizontal traveling; and

assist force alteration means for decreasing the assist force generated by the steering mechanical train compared with that in horizontal traveling of the vehicle when the vehicle is judged by the judgment means to be in ascent traveling and for increasing the assist force generated by the steering mechanical train compared with that in horizontal traveling of the vehicle when the vehicle is judged by the judgment means to be in descent traveling.

6. A steering system as set forth in claim 5, further comprising:

an assist force decision map storing various command values of the assist force in correlation with various steering torques;

an assist force alteration map storing various assist force alteration gains in correlation with various gradients in ascent traveling and descent traveling; and

wherein;

the assist force alteration means alters the assist force by multiplying a command value of the assist force which is determined in dependence on the steering torque detected by the torque sensor by reference to the assist force decision map, with an assist force alteration gain which is determined in dependence on the gradient by reference to the assist force alteration map.

7. A steering system provided in a vehicle wherein a torque transmission device alters the torque distribution of a traveling drive torque from an engine to steerable wheels and non-steerable wheels in dependence on the traveling state of the vehicle, the steering system comprising:

a steering mechanical train for transmitting a steering torque applied to a steering handle to the steerable wheels, the steering mechanical train being capable of altering the transmission ratio of the steering torque from the steering handle to the steerable wheels; and

transmission ratio alteration means for controlling the steering mechanical train to alter the transmission ratio so that the manipulation amount of the steering handle necessary to steer the steerable wheels is decreased when the torque transmission device increases the distribution of the traveling drive torque to the steerable wheels, and is increased when the torque transmission device decreases the distribution of the traveling drive torque to the steerable wheels.

8. A steering system as set forth in claim 7, further comprising:

a transmission ratio decision map storing various transmission ratios in correlation with various vehicle speeds as representative of the traveling state;

a transmission ratio alteration map storing various transmission ratio alteration gains in correlation with various values of the distribution of the traveling drive torque; and

wherein;

the transmission ratio alteration means alters the transmission ratio of the steering torque by multiplying a transmission ratio which is determined in dependence on the vehicle speed by reference to the transmission ratio decision map, with a transmission ratio alteration gain which is determined in dependence on the distribution of the traveling drive torque by the torque transmission device by reference to the transmission ratio alteration map.

9. A steering system provided in a vehicle wherein a torque transmission device alters the torque distribution of a traveling drive torque from an engine to steerable wheels and non-steerable wheels in dependence on the traveling state of the vehicle, the steering system comprising:

a steering mechanical train for transmitting the motion of a steering handle to the steerable wheels in a variable responsiveness; and

responsiveness alteration means for controlling the steering mechanical train to alter the responsiveness of the steered angle of the steerable wheels to the manipulation amount of the steering handle in the vehicle; and

wherein;

the responsiveness alteration means operates to heighten the responsiveness of the steering mechanical train when the torque transmission device increases the distribution of the traveling drive torque to the steerable wheels and to lower the responsiveness of the steering mechanical train when the torque transmission device decreases the distribution of the traveling drive torque to the steerable wheels.

10. A steering system as set forth in claim 9, further comprising:

a responsiveness decision map storing various steered angle control gains of the steerable wheels relative to the manipulation amount of the steering handle in correlation with various vehicle speeds;

a responsiveness alteration map storing various responsiveness alteration gains in correlation with various values of the distribution of the traveling drive torque; and

wherein;

the responsiveness alteration means alters the responsiveness of the steering mechanical train by multiplying a steered angle control gain which is determined in dependence on the vehicle speed by reference to the responsiveness decision map, with a responsiveness alteration gain which is determined in dependence on the distribution of the traveling drive torque to the steerable wheels and the non-steerable wheels by reference to the responsiveness alteration map.

11. A steering system provided in a vehicle wherein a torque transmission device alters the torque distribution of a traveling drive torque from an engine to steerable wheels and non-steerable wheels in dependence on the traveling state of the vehicle, the steering system comprising:

a steering torque sensor for detecting a steering torque applied to a steering handle;

a steering mechanical train for transmitting the steering torque applied to the steering handle to the steerable wheels and for generating an assist force to steer the steerable wheels in dependence on the steering torque detected by the steering torque sensor, the steering mechanical train being capable of altering the assist force generated by itself; and

assist force alteration means for decreasing the assist force generated by the steering mechanical train when the torque transmission device increases the distribution of the traveling drive torque to the steerable wheels and for increasing the assist force when the torque transmission device decreases the distribution of the traveling drive torque to the steerable wheels.

12. A steering system as set forth in claim 11, further comprising:

an assist force decision map storing various command values of the assist force in correlation with various steering torques;

an assist force alteration map storing various assist force alteration gains in correlation with various values of the distribution of the traveling drive torque to the steerable wheels and the non-steerable wheels; and

wherein;

the assist force alteration means alters the assist force by multiplying a command value of the assist force which is determined in dependence on the steering torque detected by the steering torque sensor by reference to the assist force decision map, with an assist force alteration gain which is determined in dependence on the distribution of the traveling drive torque to the steerable wheels and the non-steerable wheels by reference to the assist force alteration map.

13. A steering system provided in a vehicle wherein a torque transmission device alters the torque distribution of a traveling drive torque from an engine to steerable wheels and non-steerable wheels in dependence on the traveling state of the vehicle, the steering system comprising:

a steering mechanical train for transmitting the steering motion applied to a steering handle to the steerable wheels, the steering mechanical train being capable of altering the transmission ratio of the steering motion from the steering handle to the steerable wheels;

a transmission ratio decision map storing various transmission ratios in correlation with various vehicle speeds as representative of the traveling state;

a first transmission ratio alteration map storing various first transmission alteration gains in correlation with various values of the distribution of the traveling drive torque to the steerable wheels and the non-steerable wheels;

a second transmission ratio alteration map storing various second transmission alteration gains in correlation with various angles of the gradient in ascent traveling and descent traveling; and

transmission ratio alteration means for altering the transmission ratio of the steering mechanical train by multiplying a transmission ratio (hereafter as “

determined transmission ratio”

) which is determined in dependence on the vehicle speed by reference to the transmission ratio decision map, with a first transmission alteration gain and a second transmission alteration gain which are determined in dependence respectively on the distribution of the traveling drive torque to the steerable wheels and the non-steerable wheels and the gradient by reference respectively to the first and second transmission ratio alteration maps; and

wherein;

the various first transmission alteration gains are set to decrease, by being multiplied with the determined transmission ratio, the manipulation amount of the steering handle necessary to steer the steerable wheels when the torque transmission device increases the distribution of the traveling drive torque to the steerable wheels and to increase, by being multiplied with the determined transmission ratio, the manipulation amount of the steering handle necessary to steer the steerable wheels when the torque transmission device decreases the distribution of the traveling drive torque to the steerable wheels; and

the various second transmission alteration gains are set to decrease, by being multiplied with the determined transmission ratio, the manipulation amount of the steering handle necessary to steer the steerable wheels in ascent traveling and to increase, by being multiplied with the determined transmission ratio, the manipulation amount of the steering handle necessary to steer the steerable wheels in descent traveling.

14. A steering system provided in a vehicle wherein a torque transmission device alters the torque distribution of a traveling drive torque from an engine to steerable wheels and non-steerable wheels in dependence on the traveling state of the vehicle, the steering system comprising:

a steering mechanical train for transmitting the motion of a steering handle to the steerable wheels in a variable responsiveness;

responsiveness alteration means for controlling the steering mechanical train to alter the responsiveness of the steered angle of the steerable wheels to the manipulation amount of the steering handle;

a responsiveness decision map storing various steered angle control gains of the steerable wheels relative to the manipulation amount of the steering handle in correlation with various vehicle speeds;

a first responsiveness alteration map storing various first responsiveness alteration gains in correlation with various values of the distribution of the traveling drive torque to the steerable wheels and the non-steerable wheels, the various first responsiveness alteration gains being set to become large as the distribution of the traveling drive torque to the steerable wheels is increased;

a second responsiveness alteration map storing various second responsiveness alteration gains in correlation with various gradients in ascent traveling and descent traveling, the various second responsiveness alteration gains being set to become larger as the angle of the gradient in ascend traveling increases and to become smaller as the angle of the gradient in descend traveling increases; and

responsiveness alteration means for altering the responsiveness of the steering mechanical train by multiplying a responsiveness alteration gain which is determined in dependence on the vehicle speed by reference to the responsiveness decision map, with a first responsiveness alteration gain and a second responsiveness alteration gain which are determined in dependence respectively on the distribution of the traveling drive torque to the steerable wheels and the non-steerable wheels and the gradient by reference respectively to the first and second responsiveness alteration maps.

15. A steering system provided in a vehicle wherein a torque transmission device alters the torque distribution of a traveling drive torque from an engine to steerable wheels and non-steerable wheels in dependence on the traveling state of the vehicle, the steering system comprising:

a steering torque sensor for detecting a steering torque applied to a steering handle;

a steering mechanical train for transmitting the steering torque applied to the steering handle to the steerable wheels and for generating an assist force to steer the steerable wheels in dependence on the steering torque detected by the steering torque sensor, the steering mechanical train being capable of altering the assist force generated by itself; and

an assist force decision map storing various command values of the assist force in correlation with various steering torques applied to the steering handle;

a first assist force alteration map storing various first assist force alteration gains in correlation with various values of the distribution of the traveling drive torque to the steerable wheels and the non-steerable wheels, the various first assist force alteration gains being set to become smaller as the distribution of the traveling drive torque to the steerable wheels is increased;

a second assist force alteration map storing various second assist force alteration gains in correlation with various gradients in ascent traveling and descent traveling, the various second assist force alteration gains being set to become smaller gradually as the angle of the gradient in ascend traveling increases and to become larger gradually as the angle of the gradient in descend traveling increases; and

assist force alteration means for altering the assist force generated by the steering mechanical train by multiplying a command value of the assist force which is determined in dependence on the steering torque detected by the torque sensor by reference to the assist force decision map, with a first assist force alteration gain and a second assist force alteration gain which are determined in dependence respectively on the distribution of the traveling drive torque to the steerable wheels and the non-steerable wheels and the angle of the gradient by reference respectively to the first and second assist force alteration maps.