JP2006322794A - Steering angle sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering angle sensor, capable of instantaneously detecting steering angles when the power of a sensor is turned on, without having to make an object to be measured rotate and detecting the steering angles even in multiple rotations. <P>SOLUTION: The steering angle sensor is constituted of two parts of a shaft rotation angle detecting part A, having a gearwheel 6 having a larger diameter than that of a shaft 1 and an MR sensor part B, having a small-diameter gearwheel 8 provided, in such a way as to be engaged with the gearwheel 6. By a combination of sensor signals from magnetic detection elements 4a and 4b in the shaft rotation angle detection part A and from a magnetoresistive element 9 in the MR sensor part B, rotation angles are detected. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a steering angle sensor that detects a rotation angle of a shaft of a vehicle or the like.

10 and 11 show an example of a rotation angle detection device used for a vehicle steering angle sensor.
In this rotation angle detection device, a slit row composed of a plurality of slits 23 is arranged at a constant pitch near the periphery of a circular rotary slit plate 21 having a rotation shaft 22 at the center, and this slit row is formed from both sides. A U-shaped photocoupler 24 is fixedly installed so as to be sandwiched.

  The photocoupler 24 has a light source unit 25 and a light receiving unit 26 arranged to face each other with a gap interposed therebetween. A light emitting diode (LED) is used as the light source unit 25, and the slit row is illuminated from one side with the light from the LED, and a light / dark pattern is generated by the slit row on the surface of the light receiving unit 26 on the opposite side.

The light receiving unit 26 includes a photodiode array (PDA) is used, for example, as shown in FIG. 11, 10 photodiodes _P 0 to P ₉ are arranged linearly in the array direction of the slit 23. The light receiving unit 26 is provided with one light receiving element 27 on the same side as the PDA, and detects the number of passages of the slit 23 when the rotary slit plate 21 rotates. Each of the photodiodes P _{0 to} P ₉ in the PDA operates independently with respect to the light and dark pattern, and a photoelectric conversion signal is output from the photodiode that has been irradiated with light through the slit 23, and becomes a shadow of the rotating slit plate 21. A photoelectric conversion signal is not output from the photodiode.

  In this rotation angle detection device, it is detected to which position on the PDA the light / dark boundary line in the light / dark pattern has moved, in other words, to which position on the PDA the edge h of the slit 23 has moved, and to receive light. The number of the passage slits 23 is detected by the element 27, and the rotation angle of the rotary shaft 22 is measured based on both detection information (see Patent Document 1).

FIG. 12 shows another example of a vehicle steering angle sensor.
In this steering angle sensor, a reduction gear mechanism 32 is attached to a steering shaft 31, and the reduction gear mechanism 32 is connected to a maximum radius gear 32a that rotates integrally with the steering shaft 31, and a maximum radius gear 32a. A large radius gear 32b that rotates in mesh with each other, a small radius gear 32c that is attached to the rotation shaft of the large radius gear 32b and rotates integrally with the large radius gear 32b, and a medium radius gear 32d that rotates in mesh with the small radius gear 32c. It consists of and. The reduction gear mechanism 32 converts the entire rotation angle range of the steering shaft 31 (for example, an angle range of two rotations left and right; ± 720 degrees) into a rotation angle range of less than one rotation (360 degrees) in both directions, and outputs the output shaft. The rotation shaft of the medium radius gear 32d constituting the rotation rotates within an angular range of less than one rotation left and right. The detection unit 33 is attached to the rotation shaft of the medium radius gear 32 d, and the output of the detection unit 33 is guided to the signal processing circuit 34.

FIG. 13 shows a specific configuration of the detection unit 33.
In the detection unit 33, an annular belt yoke 42 is fixed to the rotation shaft 41 of the medium radius gear 32d, and an annular belt magnet 43 is bonded to the outer peripheral side surface of the annular belt yoke 42. The annular belt-like yoke 42 is made of a soft magnetic material such as soft iron. The annular belt magnet 43 is magnetized in the radial direction. Four stators 44 are fixedly arranged at intervals of 90 degrees with a predetermined gap 45 around the outer periphery of the annular belt-shaped magnet 43. Hall elements 46 and 47, which are magnetic sensors, are provided in two adjacent gaps of the four gaps 45, respectively. The output ends of the hall elements 46 and 47 are connected to the signal processing circuit 34.

  In the configuration of the detection unit 33 having the above configuration, when the annular belt-shaped magnet 43 rotates, the magnetic flux density in the gap 45 changes linearly according to the rotation angle. The output corresponding to the rotation angle can be taken out in analog by 47.

In the signal processing circuit 34, the steering angle is obtained by correcting the amount converted by the reduction gear mechanism 32 based on the output obtained by the Hall element 46 or 47 (see Patent Document 2).
JP-A-62-7173 JP 2002-148015 A

  However, in the method shown in FIGS. 10 and 11, it is necessary to operate the steering when detecting the absolute steering angle. Further, since the sensor is an optical encoder system, there is a problem that the resolution of the sensor becomes coarse. In addition, since the absolute steering angle is calculated by counting the pulse signal of the optical encoder with a counter, the power supply of the counter that counts the pulse signal must be attached to the steering shaft, adjusted, and always energized. Don't be. Therefore, when a battery is used for a power source such as an automobile, current is consumed regardless of whether or not a sensor signal is necessary, which causes the battery to rise.

  On the other hand, in the method shown in FIGS. 12 and 13, the absolute angle itself could not be detected when it was rotated at an angle larger than 360 ° from the reference position due to multiple rotations. For example, when the rotation is performed by 500 ° from the reference position, the rotation is once reset at 360 °, and 500-360 = 140 ° is detected as the detection angle.

  Therefore, an object of the present invention is to provide a steering angle sensor that can detect the rotation angle instantaneously when the sensor is turned on without rotating the object to be measured and can detect the absolute angle even in multiple rotations. .

  In order to solve the above problems, a steering angle sensor of the present invention includes a shaft rotation angle detection unit having a gear I having a diameter larger than the diameter of the shaft, and a magnetic sensor I provided inside the gear I. An MR sensor unit having a small-diameter gear II provided so as to mesh with the gear I, and a part of which is provided with a magnetic sensor II, and a shaft rotation angle signal detected by the magnetic sensor I, A calculation unit that calculates an absolute angle by combining sensor signals detected from the magnetic sensor II, the number of teeth of the gear I is larger than the number of teeth of the gear II, and the number of teeth of the gear I is The number of teeth of the gear II is a non-integer multiple.

  The shaft rotation angle detector has a plurality of magnetic yokes fixedly arranged on the outer peripheral surface of an annular magnet provided around the shaft with a predetermined gap therebetween, and a magnetic sensor I is provided in the gap. The MR sensor unit may be provided with a magnet at the center of the gear II, and the magnetic sensor II may be fixedly installed below the magnet.

  In the shaft rotation angle detection unit, four magnetic yokes are fixedly arranged with a predetermined gap between them, a magnetic detection element as a magnetic sensor I is provided in two of the gaps, and the MR sensor unit The magnetic resistance element as the magnetic sensor II can be fixedly installed.

  According to the present invention, the absolute steering angle can be detected when the sensor is turned on without rotating the measurement target. For this reason, since the power source is used only when the absolute steering angle value is required, it is possible to minimize the current consumption and to minimize the battery rising.

  Further, according to the present invention, the absolute angle can be detected not only in the range of 360 ° from the reference position, but also when rotating at an angle larger than 360 ° from the reference position by multiple rotations. Can be detected over a wide range.

Hereinafter, embodiments of a steering angle sensor of the present invention will be described with reference to the accompanying drawings.
(overall structure)
1 (a) and 1 (b) show an embodiment of the steering angle sensor of the present invention.
The steering angle sensor includes two shaft rotation angle detection units A having a gear 6 having a diameter larger than the diameter of the shaft 1 and MR sensor unit B having a small diameter gear 8 provided so as to mesh with the gear 6. Consists of parts.

  In the shaft rotation angle detection unit A, an annular magnet 2 is provided around the shaft 1, and four magnetic yokes 3 are fixed to the outer peripheral surface of the annular magnet 2 at predetermined intervals with a predetermined gap 5. Has been placed. Magnetic detecting elements 4a and 4b, which are magnetic sensors, are provided in two adjacent gaps among the four gaps 5, respectively.

On the other hand, in the MR sensor portion B, a circular magnet 7 is attached to the center of the gear 8, and a magnetoresistive element 9 is fixedly installed below the gear 8.
In this steering angle sensor, the rotation angle is detected by a combination of sensor signals from the magnetic detection elements 4a and 4b in the shaft rotation angle detection unit A and the magnetoresistive element 9 in the MR sensor unit B. Hereinafter, each component will be described in detail.

(Shaft rotation angle detector A)
FIG. 2 shows a partial configuration of the shaft rotation angle detector A (FIG. 2A) and output waveforms (FIG. 2B) of the magnetic detection elements 4a and 4b.

  In FIG. 2 (a), on the outside of the annular magnet 2, a magnetic yoke 3 made of four magnetic bodies is installed in non-contact with the annular magnet 2, and the magnetic yokes 3 are installed at equal intervals. Has been. Magnetic detection elements 4a and 4b are arranged between the magnetic yokes. When the shaft 1 rotates, the annular magnet 2 rotates in synchronization therewith. Since the magnetic field generated by the annular magnet 2 returns from the north pole to the south pole while passing through the magnetic yoke 3, the magnetic detection elements 4a and 4b change in magnetic flux density according to the rotation of the shaft 1.

FIG. 2B shows an example of the relationship between the rotation angle of the shaft 1 and the output waveforms of the magnetic detection elements 4a and 4b. As shown in the figure, according to the rotation angle of the magnet, the output of the magnetic detection element 4a shows a sin waveform, and the output of the magnetic detection element 4b shows a cos waveform. The rotation angle waveform of the shaft 1 is obtained by taking in two signals of the output of the magnetic detection element 4a and the output of the magnetic detection element 4b by an A / D converter and obtaining tan ^-1 . An example of the output waveform after the calculation is shown in FIG.

(MR sensor part B)
The MR sensor unit B detects the rotation angle of the gear 8 that has been accelerated from the rotation of the shaft 1.
When the gear 8 rotates, the magnetoresistive element 9 fixedly installed at the lower portion of the gear 8 is affected by the magnetic field generated by the circular magnet 7 attached to the center of the gear 8, and the rotation angle of the gear 8 is, for example, The output waveform shown in FIG. 4 is shown.

(Relationship between the gear 6 of the shaft rotation angle detector A and the gear 8 of the MR sensor B)
In this steering angle sensor, the absolute angle is calculated by combining the output waveform from the shaft rotation angle detector A having the gear 6 and the output waveform from the MR sensor B having the gear 8. Here, the number of teeth of the gear 6 and the gear 8 is formed so as to satisfy the following condition.
(1) Number of teeth of gear 6> Number of teeth of gear 8 (2) The number of teeth of gear 6 should not be an integral multiple of the number of teeth of gear 8.

Under the condition (1), the gear 8 is increased in speed with respect to the rotation of the shaft 1 and rotates. The number of accelerations of the MR sensor portion B is determined by the number of teeth of the gear 6 attached to the shaft 1 and the gear 8.
The requirement (2) is required because when the number of teeth of the gear 6 is an integral multiple of the number of teeth of the gear 8, the output waveform signal from the shaft rotation angle detection unit A having the gear 6 and the gear 8 are required. This is because the output waveform signal from the MR sensor section B having the above overlaps and the absolute angle cannot be calculated by combining these signals.
For this reason, the absolute angle with respect to the arbitrary rotational speed can be detected by the combination of the gear 6 and the gear 8 only when the above conditions (1) and (2) are satisfied.

  FIG. 5 is a graph showing the shaft rotation angle detection signal from the shaft rotation angle detection unit A and the output signal of the magnetoresistive element 9 from the MR sensor unit B on the horizontal axis. . Here, the ratio of the number of teeth of the gear 6 of the shaft rotation angle detector A and the number of teeth of the gear 8 of the MR sensor B was 1.13: 1, and the absolute angle range was −540 ° to 540 °. In order to detect an absolute angle, it is necessary to combine two signal waveform values in all absolute angle regions. In this figure, the shaft rotation angle detection signal value indicates a repetitive waveform of the absolute steering angle every 180 °. Therefore, if the output signals of the magnetoresistive elements 9 do not overlap in the region of every 180 °, these values The absolute angle can be calculated by combining the signal waveforms.

(Absolute angle conversion method)
Two detection signals, a shaft rotation angle detection signal from the shaft rotation angle detection unit A and an output signal of the magnetoresistive element 9 from the MR sensor unit B, are once taken into a personal computer by an AD converter, and an absolute steering angle described later is calculated. Calculated by the table (FIG. 6) to be converted into an absolute steering angle. The table is created at the same 180 ° shaft rotation angle period, but the MR sensor period is less than 180 °. For this reason, when the output signals of the magnetoresistive element 9 in the respective ranges of 0 to 540 ° are superimposed on the table, if these output signals do not overlap, the output signal of the magnetoresistive element 9 and the shaft rotation angle detection signal The absolute steering angle can be calculated by comparing the two levels.

Specifically, when the number of teeth of the gear 6 is X ₁ and the number of teeth of the gear 8 is X ₂ , the rotation period of the gear 6 is 180 [°], and the rotation period of the gear 8 is (X ₂ / X ₁ ) * 180 [°].
As an example, FIG. 6A shows an absolute angle conversion table showing a change at an absolute angle of 0 to 180 ° in 0 <X ₂ / X ₁ <1. Since 0 <X ₂ / X ₁ <1, the output signal of the magnetoresistive element 9 has a period of (X ₂ / X ₁ ) * 180 [°], so that one wavelength and {(X ₁ −X ₂ ) / X ₁ } * 180 period signal waveforms are detected. Further, when the waveforms of 0 to 180 ° and 180 ° to 360 ° of the magnetoresistive element 9 are overlapped, as shown in (b), the signal waveform of the magnetoresistive element 9 does not overlap. When the position at which the sensor signal of the magnetoresistive element 9 becomes 0 due to multiple rotations returns to the origin, the same repetitive signal is obtained thereafter, and the absolute angle cannot be calculated. Therefore, by adjusting the number of teeth X ₁ and X _2, it is possible to detect the absolute steering angle until the same waveform as 0 to 180 °.

The case where the same waveform as 0 to 180 ° is detected is as follows.
If the rotation angle of the shaft is Φ, the rotation angle of the gear 8 is (X ₂ / X ₁ ) * Φ. Since the rotation angle of the shaft is repeated every 180 °, (X ₂ / X ₁ ) * Φ is divisible by 180.

(Effect of this steering angle sensor)
(1) In this steering angle sensor, by combining the rotation angle detected by the shaft rotation angle detector A and the rotation angle detected in the gear with a magnet accelerated by the MR sensor B from the rotation of the shaft, An absolute angle can be detected. For example, when rotating by 500 ° from the reference position, the conventional angle sensor detects an angle of 140 ° (reset at 360 °), whereas the steering angle sensor detects an absolute angle of 500 °. The
(2) The absolute steering angle can be detected when the sensor is turned on without operating the steering. For this reason, since the power source is used only when the absolute steering angle value is required, it is possible to minimize the current consumption and to minimize the battery rising.
(3) The absolute rotation angle of the measurement object can be detected without contact.
(4) Since the steering angle information can be obtained by this steering angle sensor, it is possible to provide one elemental technology for future automatic driving of the automobile.
(5) It can also be used for autonomous navigation in car navigation.

FIG. 7 shows an example in which the present steering angle sensor is applied to a steering shaft angle sensor.
The steering shaft angle sensor 10 uses a steering angle sensor having the configuration shown in FIG. 1 as a sensor portion. In addition, the mounting area is minimized by arranging the arithmetic processor 11 on the same substrate.

  FIG. 8 is an explanatory diagram of the entire vehicle steering system. The steering shaft angle sensor 10 corresponds to the absolute steering angle sensor 12 and the arithmetic circuit 13 among the absolute steering angle sensor 12, the arithmetic circuit 13, the motion control controller 14 and the steering shaft 15 shown in FIG. is doing.

  FIG. 9 shows a magnetic field simulation result of the shaft rotation angle detection unit. The analysis was performed by rotating the annular magnet 2 using the shape of the shaft rotation angle detector A shown in FIG. Thus, an output waveform corresponding to FIG. 2B was obtained for both the magnetic detection elements 4a and 4b.

It is a block diagram which shows one Embodiment of the steering angle sensor of this invention, (a) is a top view, (b) is a side view. It is explanatory drawing of the steering angle sensor of this embodiment, (a) is a partial block diagram of a shaft rotation angle detection part, (b) is an absolute angle output waveform figure by two magnetic detection elements. It is an absolute angle output waveform figure after the calculation in the shaft rotation angle detection part A of the steering angle sensor of this embodiment. It is an absolute angle output waveform figure in MR sensor part B of the steering angle sensor of this embodiment. It is the graph which showed the combination of the shaft rotation angle detection signal and the output signal of a magnetoresistive element. It is the graph which showed the combination of the shaft rotation angle detection signal and the output signal of a magnetoresistive element, (a) shows the change in an absolute angle 0-180 degree, (b) is absolute angle 0-180 degree and 180. It is a superposition of changes of ° to 360 °. It is a top view which shows an example of the angle sensor for steering shafts. It is explanatory drawing which shows a motor vehicle steering whole system. It is a graph which shows the magnetic field simulation result of a shaft rotation angle detection part. It is a partial cross section figure which shows the rotation angle detection apparatus used for the steering angle sensor of the conventional vehicle. It is the elements on larger scale of the part of the light-receiving part in FIG. It is a block diagram which shows the conventional steering angle sensor. It is the elements on larger scale of the detection part in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Shaft 2 Ring magnet 3 Magnetic yoke 4a, 4b Magnetic detection element 5 Gap 6 Gear 7 Circular magnet 8 Gear 9 Magnetoresistive element A Shaft rotation angle detection part B MR sensor part 10 Steering shaft angle sensor 11 Calculation processor 12 Absolute steering Angle sensor 13 Arithmetic circuit 14 Motion control controller 15 Steering shaft 16 Tire 17 Pinion 18 Rack

Claims (3)

A shaft rotation angle detector having a gear I having a diameter larger than the diameter of the shaft, and a magnetic sensor I provided inside the gear I;
An MR sensor portion having a small-diameter gear II provided so as to mesh with the gear I and having a magnetic sensor II disposed in part;
A calculation unit that calculates an absolute angle by combining the sensor rotation angle signal detected by the magnetic sensor I with the sensor signal detected by the magnetic sensor II;
The steering angle sensor, wherein the number of teeth of the gear I is larger than the number of teeth of the gear II, and the number of teeth of the gear I is a non-integer multiple of the number of teeth of the gear II.   In the shaft rotation angle detection unit, a plurality of magnetic yokes are fixedly disposed on an outer peripheral surface of an annular magnet provided around the shaft with a predetermined gap therebetween, and a magnetic sensor I is provided in the gap. The steering angle sensor according to claim 1, wherein the MR sensor unit is provided with a magnet at the center of the gear II, and the magnetic sensor II is fixedly installed at a lower portion of the magnet.   In the shaft rotation angle detection unit, four magnetic yokes are fixedly arranged with a predetermined gap therebetween, a magnetic detection element as a magnetic sensor I is provided in two of the gaps, and the MR sensor The steering angle sensor according to claim 1, wherein a magnetoresistive element as the magnetic sensor II is fixedly installed in the section.

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