JP2007022165A - Cable type steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cable type steering device capable of accurately determining the steering operation force of a driver with no use of a torque sensor. <P>SOLUTION: The cable type steering device furnished with outer tubes 3c and 3d to cover inner cables 3g and 3h for transmitting the steering operation force to steered wheels comprises a resilient member 3i interposed between the outer tubes 3c and 3d and a pulley case 3b on the side with the steered wheels, a resilient member 3j interposed between the outer tubes 3c and 3d and a pulley case 3a on the steering side, displacement sensing means 3k and 3m to sense the displacement amounts of the resilient members 3i and 3j, and a control unit 5 to sense the steering torque on the basis of the sensed displacement amounts. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention belongs to the technical field of a cable type steering apparatus using a cable type column.

In the conventional cable-type steering device, instead of the torque sensor provided in the vicinity of the steering wheel, an elastic member that elastically deforms according to the steering operation force is provided, and the angle deviation between the steering angle and the turning angle caused by the deformation of the elastic member (See, for example, Patent Document 1).
JP 2004-352111 A

  However, the above-described conventional technique has a problem that if the rigidity of the elastic member is too high, the amount of displacement becomes small, and therefore an accurate steering operation force cannot be estimated unless a steering angle sensor with high resolution is used. On the other hand, when the rigidity of the elastic member is lowered, there is a problem that play is generated in the steering and the steering feeling is deteriorated.

  The present invention has been made paying attention to the above problems, and an object of the present invention is to provide a cable-type steering device that can accurately determine a driver's steering operation force without using a torque sensor. It is in.

In order to achieve the above object, the present invention provides:
In a cable-type steering device having an outer tube that covers an inner cable that transmits steering operation force to a steered wheel,
A first elastic member interposed between the first end of the outer tube and the vehicle;
A second elastic member interposed between the second end of the outer tube and the vehicle;
Steering operation force detecting means for detecting a steering operation force based on displacement amounts of the first elastic member and the second elastic member;
It is characterized by providing.

  In the present invention, since the steering torque is calculated based on the amount of displacement of the two elastic members, the outer tube and the inner cable can be saved while providing a cost-saving and space-saving configuration without providing a torque sensor near the steering wheel. In consideration of the influence of the frictional force generated between the two, the accurate steering torque can be detected based on the true tension applied to the inner cable.

  Hereinafter, the best mode for realizing the cable type steering apparatus of the present invention will be described based on the first embodiment.

First, the configuration will be described.
[overall structure]
FIG. 1 is an overall configuration diagram of a cable-type steering apparatus according to a first embodiment. The cable-type steering apparatus according to the first embodiment includes a steering wheel 1, a steering column 2, a cable-type column 3, an assist motor (assist means). ) 4 and a control unit (corresponding to steering operation force detecting means and assist control means) 5.

[Configuration of cable column]
The cable-type column 3 includes a steering wheel side pulley connected to a steering side pulley case 3a provided on the steering column 2 side and a steering gear box of a steering mechanism that steers a front wheel (steering wheel) (not shown). A case 3b and two outer tubes 3c and 3d provided between the pulley cases 3a and 3b are provided.

  As shown in FIG. 2, the cable column 3 is provided on the steering wheel 1 side, the steering side cable pulley 3 e that rotates integrally with the steering column 2, and the steering wheel provided on the front wheel (steering wheel) side. A side cable pulley 3f, two inner cables 3g and 3h that are coupled to both cable pulleys 3e and 3f while being wound in opposite directions, a steering side pulley case 3a that houses the steering side cable pulley 3e, Steering wheel side pulley case 3b for housing the steered wheel side cable pulley 3f, two outer tubes 3c, 3d for covering both inner cables 3g, 3h and connecting both pulley cases 3a, 3b, and steering torque Elastic members (first elastic member, second elastic member) 3i, 3j and elastic members 3i, 3 Displacement detecting means 3k for measuring the axial displacement of the respective, and a, and 3m.

  Both pulley cases 3a and 3b are fixed to the vehicle body. The steering pulley case 3a is fixed to the vehicle body via a steering post or the like, and the steered wheel pulley case 3b is fixed to the vehicle body via a chassis or the like.

  The elastic member 3i is interposed between the steered wheel side end (first end) of the outer tubes 3c and 3d and the steered wheel side pulley case 3b, and the elastic member 3j is disposed on the outer tubes 3c and 3d. Between the steering side end portion (second end portion) and the steering side pulley case 3a. As these elastic members 3i and 3j, springs that can be elastically deformed in the axial direction of the outer tubes 3c and 3d can be used.

  The inner cables 3g and 3h are wound around the cable pulleys 3e and 3f, and the rotation centers of the cable pulleys 3e and 3f are integrated with the pulley cases 3a and 3b. When the cables 3g and 3h move, due to the frictional force generated between the outer tubes 3c and 3d and the inner cables 3g and 3h, the outer tubes 3c and 3d are made of elastic members 3i and 3j with respect to the pulley cases 3a and 3b. It moves relative to the elastic direction.

  As shown in FIG. 3, the displacement detectors 3 k and 3 m detect displacement amounts of the elastic members 3 i and 3 j according to the driver's steering operation, and output them to the control unit 5.

  The control unit 5 calculates, for example, the displacement amount and the steering torque shown in FIG. 4 from the displacement amount of the elastic member 3i detected by the displacement detection means 3k or the displacement amount of the elastic member 3j detected by the displacement detection means 3m. The steering torque (steering operation force) is estimated using the relationship.

  Then, the control unit 5 calculates a target assist torque for reducing the driver's steering load according to the estimated steering torque and the traveling state such as the vehicle speed, and sets a command current value for matching the actual assist torque with the target assist torque. Supply to the assist motor 4.

Next, the operation will be described.
[Steering torque calculation logic based on displacement of elastic member]
First, consider the case where the outer tubes 3c and 3d and the inner cables 3g and 3h are attached straight as shown in FIG.

  As mentioned above, a frictional force is generated on the inner diameter side of the outer tubes 3c, 3d and the outer diameter side of the inner cables 3g, 3h, and in a range not exceeding the static friction force when the steering wheel 1 is turned, The outer tubes 3c and 3d and the inner cables 3g and 3h move together, and elastic force is generated in the elastic members 3i and 3j attached to the outer tubes 3c and 3d.

  Further, when the steering wheel 1 is further rotated, the elastic force of the elastic members 3i, 3j is further increased, and after the static friction force between the outer tubes 3c, 3d and the inner cables 3g, 3h is exceeded, the state is balanced by the dynamic friction force Thus, the outer tubes 3c and 3d and the inner cables 3g and 3h slide. That is, the outer tubes 3c and 3d and the inner cables 3g and 3h move as a unit within a range where the frictional force does not exceed the static frictional force, and the force to turn the steering wheel 1 is proportional to the force that displaces the elastic members 3i and 3j. Therefore, the steering torque can be measured by measuring the displacement of the elastic members 3i and 3j.

  Here, when the outer tubes 3c, 3d and the inner cables 3g, 3h are attached straight (on a straight line) as shown in FIG. 2, the outer tubes 3c, 3d after the frictional force exceeds the static frictional force. Since the inner cables 3g and 3h slip inside, the steering torque cannot be measured. However, as shown in FIG. 3, the outer tubes 3c and 3d are curved so that the directions of displacement of the elastic members 3i and 3j intersect. By arranging, the force to turn the steering wheel 1 acts in a direction to straighten the outer tubes 3c, 3d (in the state of the dotted line in FIG. 3), and due to the displacement in the direction in which the outer tubes 3c, 3d are straightened The elastic members 3i and 3j are displaced. Therefore, the steering torque can be measured by bending the outer tubes 3c and 3d and measuring the displacement of the elastic members 3i and 3j.

[Assist control action considering frictional force]
When the outer tubes 3c and 3d are bent as shown in FIG. 3, a force is applied to straighten the outer tubes 3c and 3d in the entire range of the static friction force and the dynamic friction force. Here, when the steering torque is applied with the outer tubes 3c and 3d being bent as shown in FIG. 3, the elastic members 3i and 3j are displaced toward the pulley case as shown by the arrows in the figure. Since the frictional force (regardless of the static frictional force or the dynamic frictional force) acts, a difference occurs in the displacement amount of the elastic members 3i, 3j (the displacement amount on the side where the inner cables 3g, 3h are pulled is large). The frictional force can be calculated by taking the difference between the displacement amounts 3i and 3j.

  In other words, an accurate steering torque can always be calculated even if the frictional force changes due to a change in the contact state between the outer tubes 3c and 3d and the inner cables 3g and 3h during the steering operation. Further, by removing this frictional force component from the steering torque, the steering torque for operating the steered wheels can be obtained, and accurate control can be performed when torque assisting the steered wheels.

[Steering feeling improvement]
For example, when the assist motor 4 is controlled so as to assist the detected steering torque, if the friction force between the outer tubes 3c, 3d and the inner cables 3g, 3h is known, the change occurs when the friction force changes. The assist amount is changed according to the amount. As a result, the steering torque can be made constant, and the driver does not feel the fluctuation of the frictional force, so that a good steering feeling can be obtained.

[Preventing erroneous detection of steering torque]
When the friction force between the outer tubes 3c and 3d and the inner cables 3g and 3h exceeds the static friction force and changes to dynamic friction force, the steering torque becomes unstable momentarily because the dynamic friction force is generally smaller than the static friction force. In Example 1, in preparation for such a case, a case where the steering torque exceeds the maximum static friction force (predetermined value) and shifts to the dynamic friction force is predicted, and the steering torque is calculated in a region where the predetermined value is passed. Absent. Thereby, it can suppress that an inaccurate steering torque is detected.

Next, the effect will be described.
In the cable type steering apparatus of the first embodiment, the following effects can be obtained.

  (1) In a cable-type steering apparatus having outer tubes 3c and 3d covering inner cables 3g and 3h for transmitting steering torque to a steered wheel, an intervene between outer tubes 3c and 3d and a steered wheel side pulley case 3b is provided. A control for detecting steering torque based on the mounted elastic member 3i, the elastic member 3j interposed between the outer tubes 3c, 3d and the steering pulley case 3a, and the axial displacement of the elastic members 3i, 3j A unit 5. Therefore, the steering torque can be accurately calculated based on the true frictional force generated between the outer tubes 3c, 3d and the inner cables 3g, 3h without providing a torque sensor in the vicinity of the steering wheel 1.

  (2) Since the elastic members 3i and 3j are attached to the vehicle body so that their displacement directions cross each other, regardless of the friction force generated between the outer tubes 3c and 3d and the inner cables 3g and 3h (static friction force, Steering torque can be detected in all regions (regardless of dynamic friction force).

  (3) The control unit 5 calculates the friction force between the outer tubes 3c and 3d and the inner cables 3g and 3h according to the difference in the axial displacement amount of the elastic members 3i and 3j, and calculates the calculated friction force. Based on this, the steering torque is estimated. Therefore, even when the contact state between the outer tubes 3c and 3d and the inner cables 3g and 3h changes during the steering operation and the frictional force changes, it is possible to always calculate an accurate steering torque.

  (4) The control unit 5 detects the steering torque within a predetermined range except when the frictional force between the outer tubes 3c, 3d and the inner cables 3g, 3h exceeds the static frictional force and changes to dynamic frictional force. Thus, calculation of an unstable steering torque can be suppressed.

  (5) Provided with an assist motor 4 that outputs an assist force that reduces the steering burden on the driver, and the control unit 5 controls the assist motor 4 based on the detected steering torque, and therefore assists in consideration of the frictional force. Can be realized. For example, by assisting to eliminate the frictional force, a favorable steering feeling can be obtained without causing the driver to feel the fluctuation of the frictional force.

(Other examples)
As described above, the best mode for carrying out the cable type steering apparatus of the present invention has been described based on the first embodiment. However, the specific configuration of the present invention is not limited to the first embodiment, and the invention is not limited thereto. Any design changes and the like within a range not departing from the gist of the present invention are also included in the present invention.

  For example, in Example 1, although the example which provided the displacement detection means 3k and 3m which detect the displacement amount of the elastic members 3i and 3j in the outer tube 3d side was shown, you may provide in the outer tube 3c side.

1 is an overall configuration diagram of a cable-type steering device according to Embodiment 1. FIG. FIG. 3 is a plan view showing the configuration of the cable column 3 according to the first embodiment. It is a figure which shows the state at the time of vehicle assembly | attachment of the cable type column 3 of Example 1. FIG. It is a figure which shows the relationship between the displacement amount difference of the elastic members 3i and 3j of Example 1, and steering torque.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering column 3 Cable type column 3a Steering side pulley case 3b Steering wheel side pulley case 3c, 3d Outer tube 3e Steering side cable pulley 3f Steering wheel side cable pulley 3g, 3h Inner cable 3i, 3j Elastic member 3k , 3m Displacement detection means 4 Assist motor 5 Control unit

Claims (6)

In a cable-type steering device having an outer tube that covers an inner cable that transmits steering operation force to a steered wheel,
A first elastic member interposed between the first end of the outer tube and the vehicle;
A second elastic member interposed between the second end of the outer tube and the vehicle;
Steering operation force detecting means for detecting a steering operation force based on axial displacement amounts of the first elastic member and the second elastic member;
A cable-type steering apparatus comprising: In the cable type steering apparatus according to claim 1,
A cable-type steering apparatus, wherein the first elastic member and the second elastic member are attached to a vehicle body so that displacement directions thereof cross each other. In the cable-type steering apparatus according to claim 1 or 2,
The steering operation force detecting means is configured to detect friction between the outer tube and the inner cable according to a difference between an axial displacement amount of the first elastic member and an axial displacement amount of the second elastic member. A cable-type steering apparatus characterized by calculating a force and estimating a steering operation force based on the calculated frictional force. In the cable type steering apparatus according to any one of claims 1 to 3,
The steering operation force detecting means detects the steering operation force in a predetermined range except when the friction force between the outer tube and the inner cable exceeds a static friction force and changes to a dynamic friction force. Cable type steering device. In the cable type steering apparatus according to any one of claims 1 to 4,
Assist means for outputting an assist force to reduce the steering burden on the driver;
Assist control means for controlling the assist means based on the steering operation force detected by the steering operation force detection means;
A cable-type steering apparatus comprising: In a cable-type steering device having an outer tube that covers an inner cable that transmits steering operation force to a steered wheel,
An elastic member is interposed between both ends of the outer tube and the vehicle body, and a steering operation force is detected based on an axial displacement amount of both elastic members.

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