Measuring and testing – Dynamometers – Responsive to torque
Reexamination Certificate
1999-07-07
2001-03-06
Noori, Max (Department: 2855)
Measuring and testing
Dynamometers
Responsive to torque
Reexamination Certificate
active
06196072
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cable-type steering device in which a steering wheel is connected with a steering gearbox with cables, such as Bowden cables, and more particularly, to a steering torque-detecting device for the cable-type steering device.
2. Description of the Prior Art
A cable-type steering device is proposed in which a flexible transmission means, such as a Bowden cable, replaces a steering shaft for connecting a steering wheel with a steering gearbox (for example, as shown in Japanese Patent Unexamined Publication No. Hei. 8-2431). Adopting such a cable-type steering device enables not only the free selection of a position for the steering wheel relative to the position of the steering gearbox but also the transmission of less vibrations of the steering gearbox to the steering wheel.
In a case where a power steering device is combined with a cable-type steering device, such as described above, it is necessary to detect a steering torque that is to be inputted into a steering wheel in order to control the operation of an assist motor. In a conventional steering torque-detecting device, a potentiometer is disposed between a pair of cables extending from a driving pulley, and rollers provided at ends of a V-shaped detecting arm fixed to a detecting shaft of the potentiometer are adapted to be brought into elastically springing abutment with the pair of cables, respectively. When a steering torque applied to the steering wheel rotates the driving pulley, the tension of one of the pair of cables increases, while that of the other decreases, and this rotates, together with the detecting shaft, the detecting arm, the roller of which is pressed against the cable, the tension of which increases, whereby the output from the potentiometer is changed, a steering torque being thereby detected.
With the conventional steering torque-detecting device described above, however, since there are provided therein a number of components and moving portions, the construction of the device becomes complicated, resulting in a drawback that it is difficult to secure sufficient durability. In addition, since the detecting arm generates micro-vibrations when an inner cable made of a stranded metal wire comprising a metallic strand moves along the roller while rotating it, micro-vibrations so-generated are then transmitted to the detecting shaft of the potentiometer leading to a drawback that the detection accuracy of the potentiometer is deteriorated. Moreover, since the inner cable is bent in a substantially V-shape at a portion where it abuts with the roller in response to the fluctuation in tension of the cable itself, there is also provided a drawback that the rigid feeling of the steering wheel is lowered, whereby the steering feeling is deteriorated.
SUMMARY OF THE INVENTION
The present invention was made in view of the aforementioned disadvantageous circumstances and, accordingly, an object thereof is to provide a cable-type steering device that can securely detect a steering torque inputted into the steering wheel with a simple construction and which can prevent the deterioration of the steering feel by maintaining a rigid feeling of the steering wheel.
To attain the above object, according to the present invention, there is provided a torque, detecting device for a cable-type steering device. The cable-type steering device comprises a driving pulley connected to a steering wheel, a follower pulley connected to a steering gearbox for turning vehicle wheels, and a pair of cables for connecting the driving pulley with the follower pulley for transmission of a steering torque therebetween. Each of the pair of cables comprises an outer tube and an inner cable. The outer tube is supported at one end thereof on a driving pulley housing accommodating therein the driving pulley, while the inner cable is wound around the driving pulley. The torque-detecting device comprises a pair of coils fixed, one to each of the driving pulley housings and a pair of magnetostriction elements which are disposed with respect to each of the pair of coils, in such a manner that an axial compression force acting on the outer tube in accordance with the tension of the inner cable is applied to the magnetostriction element, and that a steering torque inputted into the steering wheel is detected based on the change in inductance of the coil in response to the change in magnetic permeability of the magnetostriction element.
According to the above construction, when a steering torque is inputted in the steering wheel to rotate the same, the tension of one of the inner cables increases, while the tension of the other decreases, and the outer tube accommodating therein the inner cable, the tension of which is increased, is pulled in the same direction as that in which the inner cable is pulled, whereby an axial compression force is generated. When the axial compression force, so generated, is applied to the magnetostriction element disposed in the interior of the coil fixed to the driving pulley housing, the magnetic permeability of the magnetostriction element is changed, which changes the inductance of the coil, whereby a steering torque can be detected based on the change in inductance. Thus, with the simple construction of the above detecting device, since no moving portion is provided and not many components are used, a steering torque can be positively detected with high reliability, and, moreover, since there is generated no deflection in the cables, the rigid feel of the steering wheel can be maintained to thereby prevent the deterioration in steering feel.
Furthermore, in the above-mentioned construction of the torque detecting device according to the present invention, it is preferable that the magnetostriction element is made of a annular shape, and the inner cable penetrates through the interior of the annularly shaped magnetostriction element.
According to the above construction, since the inner cable penetrates through the interior of the annularly shaped magnetostriction element, not only can an axial compression force applied to the outer tube accommodating therein the inner cable effectively be transmitted to the magnetostriction element, but also the magnetostriction element can be disposed compactly relative to the inner cables.
REFERENCES:
patent: 4632049 (1986-12-01), Hall et al.
patent: 4697460 (1987-10-01), Sugiyama et al.
patent: 5097714 (1992-03-01), Kabuto et al.
patent: 5924520 (1999-07-01), Ehara et al.
patent: 8-2431 (1996-01-01), None
Suyama Kouichi
Toyohira Tomoya
Armstrong, Westerman Hattori, McLeland & Naughton
Honda Giken Kogyo Kabushiki Kaisha
Noori Max
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