Rotation angle detector

Abstract

The present invention relates to a rotation angle detector for use mainly in detecting rotation angles of a vehicle's steering shaft with a simplified and low-cost configuration. For the purpose, the first detection head and the second detection head are disposed perpendicularly to the rotor, and the spur gear formed outside the periphery of the first detection head is allowed to engage with the gear formed on the bottom of the periphery of the rotor. This can provide the first detection head with a simplified configuration and can form magnetic sensors together with a controller on a single circuit board. The configuration enables the rotation angle detector to perform the detection reliably and cheaply.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an exploded perspective view of the rotation angle detector used in an exemplary embodiment of the present invention.

FIG. 2 shows a partial perspective view of the rotation angle detector used in another exemplary embodiment of the present invention.

FIG. 3 shows an exploded perspective view of a conventional rotation angle detector.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

The exemplary embodiments of the present invention are described now with reference to FIGS. 1 and 2. The similar elements described in the background art have the same reference marks and details are described simply.

Exemplary Embodiments

FIG. 1 shows an exploded perspective view of the rotation angle detector used in the exemplary embodiment of the present invention. Rotor 21 made of insulation resin or metal has gear 21A formed on the bottom of the periphery and has key 21B formed at the center of inside the periphery to engage with the steering shaft (not shown) that is inserted through rotor 21 as shown in the drawing.

First detection head 22 made of insulation resin or metal and second detection head 23 similarly made of insulation resin or metal are disposed perpendicularly to rotor 21. Spur gear 22A formed outside the periphery of first detection head 22 engages with gear 21A formed on the bottom of the periphery of rotor 21. Spur gear 23A formed outside the periphery of second detection head 23 with number of teeth different from spur gear 22A engages with spur gear 22A of first detection head 22.

A plurality of wiring patterns (not shown) are formed on the top and bottom surfaces of circuit board 24 disposed collaterally and approximately parallel to first detection head 22 and second detection head 23. Magnetic sensors 5B and 6B such as anisotropic magneto-resistive (AMR) elements or the like are fixed by insert molding or the like on a surface facing magnets 5A and 6A fixed in the center of first detection head 22 and second detection head 23 respectively.

Magnet 5A and magnetic sensor 5B both facing each other form the first detection section and similarly magnet 6A and magnetic sensor 6B form the second detection section respectively. Controller 8 is formed on circuit board 24, which includes electronic components such as micro-computers and is connected to magnetic sensors 5B and 6B.

Rotor 21 is disposed rotatably in hollow cylinder 25A formed on the top surface of insulation resin-made case 25. First detection head 22 and second detection head 23 are disposed rotatably in cylinders 25B and 25C formed on a side surface of case 25 respectively.

Insulation resin-made cover 26 covers the top surface of case 25 that houses rotor 21 and similarly insulation resin-made cover 27 covers the side surface of case 25 that houses first detection head 22, second detection 23, circuit board 24 or the like.

Spring 28 made of copper alloy, steel plate or the like is disposed between the bottom surface of cover 26 and the top surface of rotor 21 in a slightly sagged condition to form a biasing spring, causing rotor 21 to contact first detection head 22 resiliently thereby completing the rotation angle detector.

Namely, disposing first detection head 22 and second detection head 23 perpendicularly to rotor 21, spur gear 22A formed on the side periphery of first detection head 22 is allowed to engage with gear 21A formed on the bottom of the periphery of rotor 21. Additionally, the same spur gear 22A is allowed to engage with spur gear 23A formed on the side periphery of second detection head 23, where first detection head 22 can do with only one gear, thus realizing a simplified configuration consequently.

Furthermore, magnetic sensors 5B and 6B, controller 8 or the like are all formed on circuit board 24 disposed in the side of first detection head 22 and second detection head 23, which can reduce the quantity of circuit board to use to only one thereby realizing a low-cost configuration.

The rotation angle detector with the above configuration is mounted on a vehicle, connecting controller 8 to an electronic circuit (not shown) of the vehicle via a connector (not shown) or the like, and inserting a steering shaft through the center of rotor 21. Since the steering shaft engages with key 21B, rotor 21 rotates in response to a rotation of the steering shaft.

In the above configuration, rotating the steering shaft while driving a vehicle, or while the rotation angle detector is in an energized condition, rotor 21 engaged with the steering shaft rotates in response to the rotation of the steering shaft and subsequently first detection head 22 whose spur gear 22A engages with gear 21A formed on the bottom of the periphery of rotor 21 starts rotating in response to the rotation of rotor 21. Then, second detection head 23 whose gear 23 A engages with spur gear 22A starts rotating in response to the rotation of first detection head 22.

Along with rotating of respective detection heads, magnets 5A and 6A mounted in the center of the heads rotate as well and subsequently magnetic sensors 5B and 6B detect the changing magnetic intensity from magnets 5A and 6A as detection signals in voltage waveform including sine waves and cosine waves.

The detection signals are input into controller 8 in an approximately saw-tooth waveform data. However, the number of gear teeth or rotation speed differs between first detection head 22 and second detection head 23, causing the waveform data to be phase-shifted due to different frequency cycle between first detection head 22 and second detection head 23.

Using the two different detection signals from first detection head 22 and second detection head 23, and respective number of teeth, controller 8 runs a predetermined calculation to output a detected rotation angle of rotor 21 or the steering shaft to the electronic circuit of the vehicle, thereby performing various controls in vehicle operation.

At this time, spring 28 is fixed between the bottom surface of cover 26 and the top surface of rotor 21 in a slightly sagged condition, thus forming a biasing spring by which rotor 21 rotates in a condition contacting on first detection head 22 resiliently. Therefore, the gear clearance between gear 21A and spur gear 22A or so-called backlash is eliminated enabling the rotation angle detector to perform a highly accurate detection without any error.

First detection head 22 and second detection head 23 are disposed perpendicularly to rotor 21, and enlarging the diameters or increasing the number of teeth can be realized relatively easily, which can perform the rotation angle detection in a still higher accuracy.

As described in the exemplary embodiment of the present invention, first detection head 22 and second detection head 23 are disposed perpendicularly to rotor 21. By allowing spur gear 22A formed outside the periphery of first detection head 22 to engage with gear 21A formed on the bottom of the periphery of rotor 21, first detection head 22 can be provided with a simplified configuration with only one spur gear 22A. Furthermore, since magnetic sensors 5B and 6B, and controller 8 can be formed on a single circuit board 24, the rotation angle detector can perform the detection reliably and cheaply.

By contacting rotor 21 on first detection head 22 resiliently using biasing spring of spring 28, the clearance between gears of rotor 21 and first detection head 22 or so-called backlash can be eliminated, enabling the rotation angle detector to perform a highly accurate detection without any error.

Moreover, another exemplary embodiment is shown in the partial perspective view in FIG. 2. Auxiliary detection head 30 with spur gear 30A formed outside the periphery is provided further, which is allowed to engage with gear 21A formed on the bottom of the periphery of rotor 21 and is provided with a detection section to detect rotation of auxiliary detection head 30 itself. Controller 8 compares the rotations between auxiliary detection head 30, and first detection head 22 and second detection head 23. If any difference between the detection signals is detected, for instance in a case of a gear out of mesh from rotor 21 or an occurrence of breakage or crack in either gear of the rotation angle detector, it can prevent erroneous detections of the rotation angle.

The rotation angle detector of the present invention can detect the rotation angle reliably with a simplified and low-cost configuration and is useful mainly to detect the rotation angle of steering shaft of a vehicle.

Claims

1. A rotation angle detector comprising: a rotor to rotate in response to a steering shaft rotation;a first detection head to rotate in response to a rotation of the rotor;a second detection head to rotate in response to the rotation of the first detection head;a first detection section to detect the rotation of the first detection head;a second detection section to detect the rotation of the second detection head; anda controller to detect a rotation angle of the rotor according to detection signals output from the first detection section and the second detection section, wherein the first detection head and the second detection head are disposed perpendicularly to the rotor.

2. The rotation angle detector of claim 1, wherein a gear is formed on a bottom of a periphery of the rotor, and a gear formed outside of a periphery of the first detection head is engaged with the gear formed on the bottom of the rotor.

3. The rotation angle detector of claim 1 further comprising a biasing spring, wherein the biasing spring allows the rotor to contact the first detection head resiliently.

4. The rotation angle detector of claim 2 further comprising a biasing spring, wherein the biasing spring allows the rotor to contact the first detection head resiliently.