JP2004101284A - Rotation angle detecting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multiple-rotation type rotation angle detecting device having high detecting accuracy. <P>SOLUTION: In this rotation angle detecting device 1, a second gear 4 meshes with a first gear 3 rotated integrally with a measured shaft 2. A projection 18 rotated integrally with the measured shaft 2 and a counting gear 19 turned in 45-degree arc in engagement with the projection 18 at intervals of designated period of the first gear 3, for example, at intervals of 180°are provided on the same axis as the measured shaft 2. The counting gear 19 obtains the count value of designated period of the first gear 3. According to the detected angle of a first rotation angle detecting sensor 13 for detecting the rotation angle of the second gear 4 and the count value of the counting gear 19, an absolute rotation angle of the measured shaft 2 is detected. In the multiple rotation of the measured shaft, the rotation angle output of the second gear 4 detected by the first rotation angle detecting sensor 13 becomes repetitive waveform with a fixed period to the rotation angle of the second gear 4. The count value of the counting gear 19 is used to discriminate which period the output value of the first rotation angle detecting sensor 13 exists in. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a rotation angle detection device that detects an absolute rotation angle of a multi-rotation shaft.
[0002]
2. Description of the Related Art
Usually, the measurement range of the rotation angle detection sensor is within one rotation (360 °). A rotation angle detection device that detects the absolute rotation angle of a multi-rotation type rotation shaft using such a rotation angle detection sensor has been provided.
For example, in a conventional rotation angle detecting device, a pair of small diameter gears having different numbers of teeth are meshed with a large diameter gear surrounding a multi-rotation body, and the rotation angle of each small diameter gear is detected by a corresponding rotation angle detection sensor. In some cases, the absolute rotation angle is detected based on the phase difference between the small-diameter gears (for example, see Patent Documents 1 and 2).
[0003]
However, in this rotation angle detection device, since the detection of the absolute rotation angle is based on the deviation of the rotation angles of the pair of small-diameter gears, each of which is accelerated with respect to the rotation angle of the multi-rotor, to increase the detection accuracy, Both the rotation angle detection sensors are required to have high accuracy.
Further, some rotation angle detecting devices obtain an absolute rotation angle by combining the detection angles of the first and second sensors for accelerating the rotation angle of the multi-rotation body at the first and second speed ratios ( For example, see Patent Document 3.) In this case as well, the detection of the absolute rotation angle is based on the detection angles of a pair of sensors that both accelerate the rotation angles of the multi-rotational body. High precision is required.
[0004]
Therefore, an object of the present invention is to solve the above-mentioned technical problem and to provide a multi-rotation type rotation angle detection device with high detection accuracy.
[0005]
[Patent Document 1]
Japanese Patent Publication No. 11-500828 [Patent Document 2]
Japanese Patent Application Publication No. 2001-505667 [Patent Document 3]
Japanese Patent Application Laid-Open No. 2000-9415
Means for Solving the Problems and Effects of the Invention
According to the first aspect of the present invention, the first gear and the protrusion and the first gear which are arranged coaxially with the rotatable shaft to be measured and are axially separated from each other and rotate integrally with the shaft to be measured are meshed with each other. A second gear, a rotation angle detection sensor that detects a rotation angle of the second gear, a counting gear that engages with the protrusion at a predetermined period of the first gear, and a detection angle and counting by the rotation angle detection sensor. Calculating means for detecting the absolute rotation angle of the shaft to be measured based on the count value of the gear.
[0007]
According to the present invention, when the shaft to be measured makes multiple rotations, the first and second gears rotate accordingly, and the rotation angle detection sensor that detects the rotation of the second gear has high accuracy but is not measured. It outputs a detection signal that repeats periodically according to the rotation angle of the shaft. In which cycle the detection signal of the rotation angle detection sensor is a detection signal is detected based on the count value of the counting gear, and the absolute rotation angle of the measured shaft can be accurately detected. In addition, a complicated speed reduction mechanism or the like is not required, so that the structure can be simplified and the manufacturing cost can be reduced.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a rotation angle detection device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic plan view of a rotation angle detection device according to one embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of the rotation angle detection device, showing an example of a case where the rotation angle detection device shown in FIG. 1 is actually packaged. Please refer to FIG. 1 and FIG.
The rotation angle detecting device 1 includes a first gear 3 that is coaxially arranged around a rotatable shaft 2 to be measured and rotates integrally with the shaft 2 to be measured, and a second gear that meshes with the first gear 3. 4 is provided.
[0009]
In the present embodiment, the rotation angle detection device 1 is applied to an electric power steering device of an automobile to detect the rotation angle of a steering member 5 (partially shown in FIG. 2) such as a steering wheel. explain. However, the present invention can be applied to detection of an absolute angle of a general multi-rotation axis.
The shaft 2 to be measured is constituted by, for example, a shaft which rotates integrally with the steering member 5, and is formed by a hollow shaft formed of a synthetic resin. A key 7 is provided on the inner periphery 6 of the measured shaft 2 as a connecting member for connecting the steering shaft 5 and the steering member 5 so as to be integrally rotatable. The key 7 protrudes radially inward, and is fitted into a key groove 9 formed on the outer periphery 8 of the steering member 5. Thereby, the steering member 5 and the measured shaft 2 are connected so as to be integrally rotatable. The keys 7 are evenly arranged at a plurality of locations in the circumferential direction, for example, at two locations, and are formed integrally with the shaft 2 to be measured. The key 7 may be formed separately from the shaft 2 to be measured and fixed to the inner periphery 6 of the shaft 2 to be measured. The shaft 2 to be measured is rotatably supported around an axis 11 by, for example, a member 10 that supports the shaft 2 via a steering member 5, for example, a steering column.
[0010]
The first and second gears 3 and 4 are spur gears. The first gear 3 is formed integrally with the shaft 2 to be measured. The first gear 3 has a larger diameter than the second gear 4 and is set, for example, to twice the diameter of the second gear 4. The second gear 4 is rotatably supported around an axis 12 parallel to the axis 11 of the first gear 3.
Further, the rotation angle detection device 1 has a first rotation angle detection sensor 13 for detecting a rotation angle of the second gear 4.
[0011]
The first rotation angle detection sensor 13 has a fixed part 14 and a movable part 15 which are relatively displaced from each other. The first rotation angle detection sensor 13 is, for example, a magnetic displacement sensor, the fixed unit 14 is formed of, for example, a sensor body including a magnetoresistive element, and the movable unit 15 is formed of, for example, a magnet. The output signal from the sensor main body is different depending on the relative position between the fixed part 14 and the movable part 15.
The movable part 15 of the first rotation angle detection sensor 13 is fixed to the end face of the second gear 4 so as to be integrally rotatable. The fixed portion 14 is disposed to face the vicinity of the movable portion 15 and is fixed to, for example, a circuit board 16 as a support member. The output signal of the first rotation angle detection sensor 13 periodically changes every predetermined period (for example, 360 °) of the second gear 4.
[0012]
Around the measured shaft 2, two projections 18 that rotate integrally with the measured shaft 2 are provided outward, for example, at 180 ° intervals. The protrusion 18 is arranged apart from the first gear 3 in the axial direction of the measured shaft 2 (see the arrow S). The protrusion 18 can be formed integrally with the shaft to be measured 2 or can be formed integrally with the first gear 3. The protrusion 18 is, for example, a key provided on the outer periphery of the measured shaft 2.
In addition, the rotation angle detection device 1 has a counting gear 19 that engages with the above-described protrusion 18 at a predetermined cycle (for example, 180 °) of the first gear 3. Here, the predetermined period of the first gear 3 for the projection 18 is made equal to the period in which the output signal of the first rotation angle detection sensor 13 changes.
[0013]
The counting gear 19 is rotatably supported around an axis 20 parallel to the axis 11 of the first gear 3. The counting gear 19 has a plurality of, for example, eight teeth 21 evenly arranged on its outer periphery. The teeth 21 and the projections 18 abut.
At the rotation angle of the shaft 2 to be measured, the teeth 21 of the counting gear 19 and the projection 18 come into contact only in a rotation angle range that is very short as compared with the above-described predetermined period of the first gear 3. Between the rotation angle range in which the counting gear 19 and the projection 18 are engaged, a rotation angle range that is larger than this rotation angle range and in which the counting gear 19 and the projection 18 are not engaged is provided.
[0014]
The counting gear 19 rotates only while the counting gear 19 and the projection 18 are engaged. For example, each time the shaft 2 to be measured rotates by 180 °, one of the two projections 18 comes into contact with and engages with any one of the teeth 21 of the counting gear 19 in an angular range near the rotation. Each time, the counting gear 19 rotates by a predetermined angle, for example, 45 °. In this manner, a change in the rotation angle of the counting gear 19 that changes stepwise can be obtained from a change in the rotation angle of the shaft 2 to be measured that changes linearly. It is possible to obtain a count value corresponding to the number of engagements or the number of times the first gear 3 reaches the predetermined cycle.
[0015]
Further, the present rotation angle detecting device 1 has a support member 24 that rotatably supports the counting gear 19 and the second gear 4 via support shafts 22 and 23 formed thereon. The support member 24 is positioned with respect to the measured shaft 2 via, for example, the member 10 described above.
In addition, the rotation angle detection device 1 includes a second rotation angle detection sensor 25 for detecting a rotation angle of the counting gear 19 as counting means for obtaining a count value of the counting gear 19, and a first rotation angle detection sensor 13 And an absolute angle calculation unit 26 as calculation means for calculating the absolute rotation angle of the shaft 2 to be measured based on the detection angle of the shaft 2 and the count value of the counting gear 19.
[0016]
The second rotation angle detection sensor 25 has, for example, substantially the same structure as the first rotation angle detection sensor 13, and has the same fixed portion 27 and movable portion 28. The movable part 28 of the second rotation angle detection sensor 25 is fixed to the end face of the counting gear 19 and rotates integrally with the counting gear 19. The fixed portion 27 is disposed to face the vicinity of the movable portion 28 and is fixed to, for example, the circuit board 16 as a support member. The rotation angle output by the second rotation angle detection sensor 25 corresponds to the count value of the counting gear 19, that is, if the output rotation angle is within a predetermined range, the rotation angle corresponds to this predetermined range. It can be determined that it is a count value. Such a determination is integrally processed by the absolute angle calculation unit 26.
[0017]
The absolute angle calculation unit 26 is configured by a signal processing electric circuit including a microcomputer, for example, and is mounted on the circuit board 16, for example. Detection signals from the first and second rotation angle detection sensors 13 and 25 are input to the absolute angle calculation unit 26. The absolute angle calculator 26 calculates the absolute rotation angle of the shaft 2 to be measured based on the rotation angle of the second gear 4 and the rotation angle of the counting gear 19 detected by the first and second rotation angle detection sensors 13 and 25. Is calculated.
[0018]
When the measured shaft 2 is rotated, for example, clockwise in FIG. 1 (see arrow M1), the second gear 4 meshing with the first gear 3 is turned in the opposite direction, for example, counterclockwise in FIG. (See arrow M2). At this time, the rotation angle of the second gear 4 is larger than the rotation angle of the first gear 3. Further, for example, when the measured shaft 2 rotates 90 ° from the state shown in FIG. 1, the counting gear 19 rotates 45 ° (see the arrow M3). Each time the shaft 2 to be measured rotates by 180 °, the counting gear 19 rotates by 45 °.
[0019]
FIG. 3 is a graph showing the relationship between the rotation angle of the measured shaft 2 and the output waveforms of the first and second rotation angle detection sensors 13 and 25. When, for example, the steering shaft as the measured shaft 2 is rotated four times, as shown in FIG. 3, the output S1 of the first rotation angle detection sensor 13 for detecting the rotation angle of the second gear 4 (solid line in FIG. 3) Is a saw-tooth waveform having a cycle of 180 deg, for example. Although the output S1 of the first rotation angle detection sensor 13 has high detection accuracy, the output S1 is repeated eight times in a 180 deg cycle, so it is not known which cycle it is.
[0020]
On the other hand, the output S2 of the second rotation angle detection sensor 25 (indicated by a broken line in FIG. 3) has a waveform that changes stepwise in a stepwise manner each time the projection 18 and the teeth of the counting gear 19 engage. . Each stage corresponds to the count value of the counting gear 19. A count value is obtained based on the level of the output S2 of the second rotation angle detection sensor 25, and it is determined in which cycle the output value of the first rotation angle detection sensor 13 is based on the count value. it can. Therefore, the absolute rotation angle of the measured shaft 2 can be accurately detected.
[0021]
In addition, a complicated speed reduction mechanism or the like is not required, so that the structure can be simplified and the manufacturing cost can be reduced. For example, the projection 18 has a simpler structure than a gear.
Further, for example, when the inner diameter of the measured shaft 2 is 25 mm, the rotation angle detecting device 1 can be downsized to an annular outer shape having an outer diameter of about 70 mm and a height of about 10 mm.
The above-mentioned key 7 can use a known structure, but is more preferably configured as follows. Please refer to FIG. 4 and FIG.
[0022]
The width (dimension L1) of the key 7 is set to be longer than the width (dimension L2) of the key groove 9 by a predetermined length (L1> L2). Thereby, when the key 7 is fitted into the key groove 9, rattling can be prevented, and generation of abnormal noise due to rattling can be prevented. Further, for example, the rotation angle of the steering member 5 can be precisely controlled. Preferred for detection.
The key 7 has a groove-like slit 31 extending linearly in the axial direction. The slits 31 are opened at both ends in the axial direction and inward in the radial direction. The key 7 is constituted by a pair of cantilevered elastic protrusions 32 arranged in the circumferential direction of the inner circumference 6 of the measured shaft 2 with a predetermined gap amount opened by the slit 31. The key 7 is elastically fitted into the key groove 9 by the pair of elastic projections 32. When the key 7 is fitted into the key groove 9 which is narrower than the key groove 9, the elastic projections 32 bend, and the slit 31 absorbs a dimensional error or an assembly error of the fitting. Further, it is possible to prevent an excessive load from being applied to the periphery of the key 7 and the key groove 9.
[0023]
The side of the key 7 has a tapered inclined portion 33. The inclined portions 33 are formed on both sides in the circumferential direction of the inner circumference 6 of the shaft 2 to be measured, and the portions near the axial ends are close to each other, and the ends of the keys 7 are narrow in the circumferential direction. It is supposed to be. When the key 7 is fitted into the key groove 9, the inclined portion 33 is guided along the edge 35 of the key groove 9, thereby guiding the key 7 to a position centered on the key groove 9 which is narrower. The inclined portions 33 are formed on both sides in the axial direction, so that the key 7 can be easily fitted into the key groove 9 even when the fitting direction between the key 7 and the key groove 9 is any direction.
[0024]
It should be noted that the present invention is not limited to the above-described embodiment, and the following may be considered. In the following description, points different from the above-described embodiment will be mainly described, and the description of the same components will be omitted, and the same reference numerals will be given.
In the above-described embodiment, the configuration for obtaining the count value of the counting gear 19 may be any sensor that can obtain a resolution of about the count value per rotation, and is, for example, more than the first rotation angle detection sensor 13. A simple structure can also be used.
[0025]
Further, as the first rotation angle detection sensor 13, for example, a known configuration such as a magnetic displacement sensor, a potentiometer, a photoelectric displacement sensor, or the like can be used. In addition, such a displacement sensor may be an incremental type that detects a relative displacement amount between the movable part and the fixed part, or an absolute type that detects an absolute position change between the movable part and the fixed part. preferable. In addition, various changes can be made within the scope of the claims of the present invention.
[Brief description of the drawings]
FIG. 1 is a schematic plan view of a rotation angle detection device according to an embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view of the rotation angle detection device, showing an example of actually packaging the rotation angle detection device of FIG. 1;
FIG. 3 is a graph showing a relationship between a rotation angle of a measured shaft and an output of each rotation angle detection sensor in the embodiment of FIG. 1;
FIG. 4 is a cross-sectional view showing a modification of the key and the key groove shown in FIG. 1, and FIGS. 4A and 4B show a key and a measured shaft near the key groove before fitting, respectively. The key fitted in 4C and the shaft to be measured near the key groove are illustrated.
5 is a view of the key and the key groove shown in FIG. 4 as viewed from the center of rotation. FIG. 5A shows a state before fitting, FIG. 5B shows a state during fitting, and FIG. Indicates the status.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Rotation angle detection device 2 Measured shaft 3 First gear 4 Second gear 13 First rotation angle detection sensor (rotation angle detection sensor)
18 Projection 19 Counting gear 26 Absolute angle calculation unit (Calculation means)
S axis direction

Claims (1)

A projection and a first gear which are arranged coaxially with the rotatable shaft to be measured and are axially separated from each other and rotate integrally with the shaft to be measured;
A second gear meshing with the first gear;
A rotation angle detection sensor for detecting a rotation angle of the second gear;
A counting gear engaged with the projection at a predetermined period of the first gear;
A rotation angle detection device comprising: a calculation unit configured to detect an absolute rotation angle of the shaft to be measured based on a detection angle of the rotation angle detection sensor and a count value of the counting gear.

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