This invention relates to a guide device for guiding a car along guide rails provided in a hoistway and, in particular, to a guide device for an elevator capable of restraining horizontal vibrations of a car.
FIG. 15 is a front view of a main portion of a conventional elevator as disclosed, for example, in JP 8-26624 A, and FIG. 16 is a plan view of the elevator of FIG. 15.
Referring to the drawings, a pair of guide rails 2 with a T-shaped section are arranged in parallel in a hoistway 1. A car 3 is suspended in the hoistway 1 by a main cable (not shown), and is raised and lowered along the guide rails 2 by a drive device (not shown).
The car 3 has a car frame 4, a cab 5 supported by the car frame 4, and a plurality of rubber vibration isolators 6 arranged between the car frame 4 and the cab 5. A car door 7 is provided in the cab 5. Further, a control board 8 is mounted in the cab 5.
First, second, and third acceleration sensors 9a, 9b, and 9c are mounted on the upper end portion of the car frame 4. Fourth, fifth, and sixth acceleration sensors 9d, 9e, and 9f are mounted on the lower end portion of the car frame 4. Vibration of the car frame 4 in the direction of the width of the car 3 (the Y-axis direction) is detected by the first and fourth acceleration sensors 9a and 9d mounted at the center of the car frame 4. Vibration in the direction of the depth of the car 3 (the Z-axis direction) is detected by the second, third, fifth, and sixth acceleration sensors 9b, 9c, 9e, and 9f arranged on either side of the first and fourth acceleration sensors 9a and 9d. 
The guide rails 2 have installation-mounting portions 2a fixed to the walls (not shown) of the hoistway 1 and guide portions 2b extending perpendicularly from the installation-mounting portions 2a. Each guide portion 2b has first and second guide surfaces 2c and 2d for guiding the car 3 with respect to the depth direction and a third guide surface 2e for guiding the car 3 with respect to the width direction.
At each of the four corners of the car frame 4, there is mounted a roller guide main body 10 engaged with the first, second, and third guide surfaces 2c, 2d, and 2e. Each roller guide main body 10 has a first roller 11a rolling on the first guide surface 2c, a second roller 11b rolling on the second guide surface 2d, a third roller 11c rolling on the third guide surface 2e, and a plurality of springs 12 for pressing the first, second, and third rollers 11 a, 11b, and 11c against the first, second, and third guide surfaces 2c, 2d, and 2e. 
Further, mounted on each roller guide main body 10 are first, second, and third actuators 13a, 13b, and 13c for adjusting the force with which the first, second, and third rollers 11a, 11b, and 11c are pressed against the guide rail 2 by generating electromagnetic forces with respect to the guide rail 2.
FIG. 17 is a circuit diagram showing a part of the circuits in a control board 8 of FIG. 15. Detection signals from the first through sixth acceleration sensors 9a through 9f are processed by first, second, third, fourth, fifth, and sixth controllers 14a, 14b, 14c, 14d, 14e, and 14f in the control board 8. The actuators 13a, 13b, and 13c are controlled by corresponding controllers 14a through 14f. 
Each of the controllers 14a through 14f has a signal processing circuit 15, a phase inverter 16, and a pair of current amplification devices 17a and 17b. The signal processing circuits 15 receive detection signals from the acceleration sensors 9a through 9f and perform computation processing for restraining acceleration and outputting processing signals. The current amplification devices 17a and 17b amplify/adjust signals from the signal processing circuits 15 and output them to the actuators 13a through 13c. Each phase inverter 16 is connected between the signal processing circuit 15 and one current amplification device 17b. 
Next, the operation of the device will be described. When horizontal vibrations are generated in the car frame 4 during traveling of the car 3, the acceleration of the vibrations are detected by the acceleration sensors 9a through 9f. The detection signals are processed by the controllers 14a through 14f, and the actuators 13a through 13c are controlled so as to cancel the acceleration.
Regarding the vibration component in the direction of the width of the car 3, the acceleration is detected by the first and fourth acceleration sensors 9a and 9d, and the detection signals are processed by the controllers 14a and 14d, the acceleration being canceled by the actuators 13c. 
Regarding the vibration component in the direction of the depth of the car 3, the acceleration is detected by the second, third, fifth, and sixth acceleration sensors 9b, 9c, 9e, and 9f, and the detection signals are processed by the controllers 14b, 14c, 14e, and 14f, the acceleration being canceled by the actuators 13a and 13b. 
The trouble with the above-described conventional elevator is that a pair of expensive current amplification devices 17a and 17b, composed of a large number of various parts, are provided in each of the controllers 14a through 14f, with the result that the number of current amplification devices is large and that the control board 8 is expensive.
The present invention has been made with a view toward solving the above problem in the prior art. It is an object of the present invention to provide an inexpensive guide device for an elevator which is superior in restraining horizontal vibrations of the car.
In accordance with this invention, there is provided a guide device for an elevator, which is engaged with a pair of guide rails each having first and second guide surfaces for guiding a car in a car depth direction and a third guide surface for guiding the car in a car width direction and which is adapted to guide the traveling of the car, the guide device comprising: a plurality of guide members mounted in the car and abutting the first through third guide surfaces; a plurality of urging means provided between the car and the guide members and adapted to press the guide members against the guide rails; a plurality of actuators mounted in the car and adapted to adjust the force with which the guide members are pressed against the guide rails; a plurality of acceleration sensors mounted in the car and adapted to detect accelerations in the depth direction and the width direction of the car; and a plurality of controllers for respectively controlling pairs of actuators reversing the force applied to the guide members in accordance with information from the acceleration sensors, wherein each controller has: a signal processing circuit for receiving detection signals from one of the acceleration sensors and adapted to perform computation processing for restraining any acceleration generated in the car; a current amplification device for amplifying/adjusting signals from the signal processing circuit; and a plurality of diodes respectively provided between the current amplification device and one of the pairs of actuators and adapted to selectively output signals from the current amplification device to the pair of actuators.