Steering device

• US 7,260,458 B2
• Filed: 05/26/2003
• Issued: 08/21/2007
• Est. Priority Date: 05/27/2002
• Status: Active Grant

• Current Assignee: Aisin Seiki Co., Ltd. (Aisin Corp.), Jtekt Corporation (Toyota Motor Corporation)
• Original Assignee: Aisin Seiki Co., Ltd. (Aisin Corp.), Jtekt Corporation (Toyota Motor Corporation)
• Inventors: Tanaka, Wataru, Kato, Hiroaki, Ono, Eiichi, Asano, Kenji, Yasui, Yoshiyuki, Muragishi, Yuji, Momiyama, Minekazu, Ogawa, Shoji, Imoto, Yuzou
• Primary Examiner(s): Tran; Dalena
• Application Number:
  US10/515,178
• Publication Number:
  US 20050161279A1
• Time in Patent Office: 1,548 Days
• Field of Search: 701/41, 701/75, 701/80, 701/73, 701/74, 701/69, 701/70, 701/71, 701/72, 701/76, 701/82, 701/84, 180/197, 180/412, 180/446, 303/139, 303/140, 303/145
• US Class Current: 701/41
• CPC Class Codes: B62D 15/029 Steering assistants using warnings or proposing actions to the driver without influencing the steering system
• CPC Class Codes: B62D 6/006 using a measured or estimated road friction coefficient
• 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

Abstract

In a steering apparatus, in accordance with a grip limit control process (30b′), it is determined whether or not a grip degree ε estimated by a grip degree estimation arithmetically operating process (30a) is less than a predetermined grip degree (ε′), and in the case that it is determined that an estimated grip degree (ε) is less than the predetermined grip degree (ε′), the process applies such a feeling that a steering operation by a steering wheel suddenly becomes light to a driver, by suddenly increasing an assist quantity by a motor (M), thereby notifying the driver of the matter that the grip degree of a steered wheel is close to a limit. Therefore, it is possible to transmit to the driver a probability that a side slip is generated by further turning the steering wheel 21 in the same direction as the current direction, thereby calling the driver'"'"'s attention for steering. Accordingly, there is an effect that a stability of a vehicle behavior can be improved without applying any fear of insecurity to the driver.

Claims

1. A steering apparatus provided with a motor generating an assist force for assisting for a steering force on the basis of a steering torque generated in a steering shaft, comprising:

a steering force index detecting means for detecting at least one steering force index among steering indexes including a steering torque and a steering force applied to a steering system from a steering wheel of a vehicle to a suspension;

a self-aligning torque estimating means for estimating a self-aligning torque generated in a front wheel of said vehicle on the basis of a detected signal of said steering force index detecting means;

a vehicle state quantity detecting means for detecting a state quantity of said vehicle;

a front wheel index estimating means for estimating at least one front wheel index among front wheel indexes including a side force with respect to the front wheel of said vehicle and a front wheel slip angle on the basis of a detected signal of said vehicle state quantity detecting means;

a grip degree estimating means for estimating a grip degree with respect to at least the front wheel of said vehicle on the basis of a change of the self-aligning torque estimated by said self-aligning torque estimating means, with respect to the front wheel index estimated by said front wheel index estimating means;

a determining means for determining whether or not the grip degree estimated by said grip degree estimating means is less than a predetermined value; and

a notifying means for notifying a driver of a fact that the grip degree of the front wheel of said vehicle is close to a limit, in the case that it is determined by said determining means that said estimated grip degree is less than the predetermined value,

wherein the grip degree is indicative of a grip level of tire on a road surface in a vehicle-wheel lateral direction.

2. A steering apparatus as claimed in claim 1, wherein said notifying means is constituted by an increase of the assist force generated in said motor.

3. A steering apparatus as claimed in claim 1, wherein said notifying means is constituted by a decrease of the assist force generated in said motor.

4. A steering apparatus as claimed in claim 1, wherein said notifying means is constituted by a vibration of a drive current applied to said motor.

5. A steering apparatus provided with a motor generating an assist force for assisting for a steering force on the basis of a steering torque generated in a steering shaft, comprising:

a steering force index detecting means for detecting at least one steering force index among steering indexes including a steering torque and a steering force applied to a steering system from a steering wheel of a vehicle to a suspension;

a self-aligning torque estimating means for estimating a self-aligning torque generated in a front wheel of said vehicle on the basis of a detected signal of said steering force index detecting means;

a vehicle state quantity detecting means for detecting a state quantity of said vehicle;

a front wheel index estimating means for estimating at least one front wheel index among front wheel indexes including a side force with respect to the front wheel of said vehicle and a front wheel slip angle on the basis of a detected signal of said vehicle state quantity detecting means;

a grip degree estimating means for estimating a grip degree with respect to at least the front wheel of said vehicle on the basis of a change of the self-aligning torque estimated by said self-aligning torque estimating means, with respect to the front wheel index estimated by said front wheel index estimating means;

a determining means for determining whether or not the grip degree estimated by said grip degree estimating means is less than a predetermined value; and

a notifying means for notifying a driver of a fact that the grip degree of the front wheel of said vehicle is close to a limit, in the case that it is determined by said determining means that said estimated grip degree is less than the predetermined value,

wherein said notifying means is constituted by a vibration of a drive current applied to said motor.