1. Field of the Invention
The present invention relates to a cable-type steering device in which a steering wheel and a steering gear box are connected to each other by flexible cables such as Bowden cables.
2. Related Art
A conventional steering device for a vehicle is designed such that a steering shaft having a steering wheel at its upper end is connected at its lower end to a steering gear box, so that a steering torque inputted to the steering wheel is transmitted through the steering shaft to a rack and pinion mechanism provided within the steering gear box.
However, if the steering wheel and the steering gear box are connected to each other using the steering shaft, the following problem is encountered: it is difficult to freely select the position of the steering wheel relative to the position of the steering gear box. For this reason, not only the degree of freedom of the design is limited, but the steering gear box also cannot be commonly used in both of a right-side driven vehicle and a left-side driven vehicle. Moreover, there is another problem that the vibration received from a road surface through a tire and the vibration of an engine are transmitted through the steering shaft to the steering wheel, so that such vibrations detract from the calmness within a vehicle compartment and thus the riding comfort.
Therefore, in place of the conventional steering shaft, a cable-type steering device has been proposed which uses a flexible transmitting means such as Bowden cables (for example, see Japanese Patent Application Laid-open No.8-2431).
The use of a cable-type steering device allows the position of the steering wheel relative to the position of the steering gear box to be freely selected. Additionally, the vibration of the steering gear box has difficulty being transmitted to the steering wheel. Thus, the above-described problems can be eliminated.
When the cable-type steering device is combined with a power steering device, the driver's steering operation can be assisted by detecting a steering torque inputted to the steering wheel to drive an actuator for the power steering device. In this case, if a steering torque detecting means is provided in the steering gear box, the following problem is encountered: it is impossible to detect a steering torque including a friction of cables interposed between the steering wheel and the steering torque detecting means. For this reason, an assisting force offsetting the friction cannot be generated in the actuator, resulting in a reduced steering feeling.