JP2006284237A - Rotation angle sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotation angle sensor capable of detecting a rotation angle in an instant when powered up. <P>SOLUTION: A plurality of magnetic yokes 2 are so arranged as to circularly surround the periphery of a circular magnet 1 having magnetic poles radially, and gaps 3 are formed at at least two locations by separating the magnetic yokes 2 adjoining mutually in a circumferential direction. Magnetic elements 4 for detecting magnetic densities are set respectively in these gaps 3 provided at the at least two locations, and an operational circuit 5 for finding a rotation angle which the circular magnet 1 forms with respect to a magnetic yoke 2 from the combinations of the magnetic densities detected by these magnetic elements 4. Thus, an absolute rotation angle within one rotation can be detected in an instant when powered up. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a rotation angle sensor that detects a rotation angle of a rotating body such as a steering angle by a steering shaft, and relates to a rotation angle sensor that can instantaneously detect a rotation angle when power is turned on.

  Conventionally, the steering angle by the steering shaft is detected by a rotation angle sensor as shown in FIG.

  This rotation angle sensor obtains an absolute steering angle by a combination of output signals of the two sensors 71 and 72. The absolute steering angle exceeds 360 degrees so that the rotation angle of the first rotation, the second rotation, the third rotation,... Can be distinguished from each other for a rotating body that rotates a plurality of times (also referred to as multiple rotations) like the steering shaft 73. However, the steering angle is represented by an absolute rotation angle that increases without being canceled at 0 degrees.

  That is, the first sensor 71 is an optical encoder plate 74 that is connected to a steering shaft 73 of the vehicle and rotates at the same rotation angle as the steering shaft 73, and an LED and PD (not shown) fixed to the vehicle. And module 75. The optical encoder plate 74 is a disk surrounding 360 degrees around the steering shaft 73, and is provided with a slit (detailed shape is omitted) 76 according to a code value made of a gray code or a bit code corresponding to 360 degrees. The optical encoder module 75 is configured to face each other with a pair of LED and PD sandwiching the optical encoder plate 74 at a plurality of detection points 77 distributed at predetermined positions in the radial direction. When the optical encoder plate 74 rotates, the light emitted from the LED passes through the slit 76 and an output voltage is obtained from the PD. The light is blocked except for the slit 76 and the output voltage of the PD becomes zero. Since there are a plurality of LED / PD pairs, a rotation angle in the range of 360 degrees can be detected by comparing the output voltage pattern of each PD with a gray code or a bit code.

  The second sensor 72 is attached to the steering shaft 73 and rotates at the same rotation angle as that of the steering shaft 73. The second sensor 72 meshes with the gear 78 and rotates at a higher speed (for example, 1.75 times) than the steering shaft 73. A gear 79 that rotates at an angle, a magnet 70 built in the gear 79, and an MR sensor (not shown) that detects a magnetic flux density that changes as the magnet 70 rotates are provided. Thereby, the rotation angle of the gear 79 can be detected by a change in magnetic flux density. The change in the magnetic flux density takes one cycle of the gear 79 as a cycle, but changes faster than one rotation of the steering shaft 73 because the gear 79 is accelerated from the gear 78.

  The combination of the output signals of these two sensors 71 and 72 differs between when the steering shaft 73 rotates once and when it rotates twice or more. Therefore, the absolute steering angle can be obtained by referring to a table in which the relationship between the combination of output signals and the absolute steering angle is stored in advance by an arithmetic circuit using a microcomputer or the like. However, even if the absolute steering angles are different, the combinations of the output signals of the two sensors 71 and 72 may overlap, and in that case, the temporal change in the output signals of these two sensors 71 and 72 The absolute steering angle is specified with reference to the change value of.

JP 2004-271495 A

  In the prior art, the absolute steering angle is obtained by a combination of output signals of the two sensors 71 and 72. However, since the first sensor 71 is an optical encoder system, the resolution of the rotation angle is poor. For this reason, the combination of the output signals of the two sensors 71 and 72 sometimes overlaps. Then, it is necessary to obtain the absolute steering angle from the change values before and after each sensor output. In order to output the change value, it is necessary to rotate the steering shaft 73.

  The fact that the absolute steering angle cannot be obtained unless the change value before and after each sensor output is detected by rotating the steering shaft 73 means that the absolute steering angle does not appear at the moment the main power is turned on in the vehicle. It is. This is inconvenient in the driving operation of the vehicle. This is a problem not only in vehicles but also in the field of detecting the absolute rotation angle of a rotating body that rotates a plurality of times.

  In the optical encoder method, in general, when the absolute type is used, the rotation angle can be read at the moment when the main power is turned on, but when the number of bits is increased to increase the detection accuracy, the diameter of the optical encoder plate increases. When the increment type is used, there is a problem that a backup power source is required to hold the count value when the power is turned off.

  In addition, there are demands for reducing the power consumption of the rotation angle sensor, demands for reducing the influence of the surrounding environment such as temperature, and demands for making the sensor characteristics less susceptible to the material.

  Accordingly, an object of the present invention is to solve the above-described problems and provide a rotation angle sensor capable of instantaneously detecting the rotation angle when the power is turned on.

  To achieve the above object, according to the present invention, a plurality of magnetic yokes are arranged so as to annularly surround a circular magnet having magnetic poles in the radial direction, and at least two magnetic yokes adjacent to each other are separated in the circumferential direction. Magnetic elements for detecting the magnetic flux density are installed in at least two gaps, and the rotation angle of the circular magnet with respect to the magnetic yoke is determined from the combination of the magnetic flux densities detected by these magnetic elements. An arithmetic circuit to be obtained is provided.

  It is also possible to form at least two gaps having different circumferential angles of 90 degrees, and to install the magnetic elements in these two gaps.

  The arithmetic circuit previously stores in a table the relationship between the combination of magnetic flux density detected by the magnetic element and the rotation angle while the circular magnet makes one rotation around the axis, and the detected combination of magnetic flux densities. Thus, the rotation angle may be obtained by referring to the table.

  Reed switches that are opened / closed by a change in magnetic flux density are installed in at least two gaps, and the arithmetic circuit roughly determines the rotation angle of the circular magnet with respect to the magnetic yoke from the combination of opening / closing of these reed switches. Also good.

  The arithmetic circuit obtains the number of rotations of the circular magnet from the history of change in combination of opening and closing of the reed switch, and adds the rotation angle obtained from the combination of magnetic flux densities detected by the magnetic element to the number of rotations × 360 degrees. The cumulative rotation angle may be obtained.

  The arithmetic circuit comprises: a rough arithmetic circuit that roughly obtains a rotation angle of the circular magnet with respect to the magnetic yoke from a combination of opening and closing of the reed switch; and the circular magnet is determined from the combination of magnetic flux densities detected by the magnetic element. A fine arithmetic circuit for obtaining a rotation angle made with respect to the magnetic yoke, and when the coarse arithmetic is sufficient, the fine arithmetic circuit and the magnetic element are stopped from being supplied with power, and only when the fine arithmetic is necessary, the fine arithmetic circuit and A power saving control circuit for supplying power to the magnetic element.

  As the magnetic yoke, four fan-shaped magnetic yokes may be provided so as to divide the circumference of the circular magnet into four, and the magnetic elements may be installed in two gaps having a circumferential angle of 90 degrees.

  Reed switches that can be opened and closed by changing the magnetic flux density may be installed in the remaining two gaps.

  The present invention exhibits the following excellent effects.

  (1) The rotation angle can be detected instantaneously when the power is turned on.

  (2) The absolute rotation angle in a plurality of rotations can be detected.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  As shown in FIG. 1, in the rotation angle sensor according to the present invention, a plurality of magnetic yokes 2 are arranged so as to surround a circular magnet 1 having magnetic poles N and S in the radial direction, and adjacent to each other. The yokes 2 are separated from each other in the circumferential direction to form at least two gaps 3, and magnetic elements 4 for detecting the magnetic flux density are installed in the at least two gaps 3, respectively. An arithmetic circuit 5 for obtaining a rotation angle of the circular magnet 1 with respect to the magnetic yoke 2 from the combination is provided. The circular magnet 1 and the magnetic yoke 2 only need to rotate relatively, but here, the circular magnet 1 rotates around the axis, and the magnetic yoke 2 is fixed.

  Since the circular magnet 1 has a magnetization period of 360 degrees, the magnetic flux density is high in the vicinity of the north pole and the south pole on the opposite side of 180 degrees, and the magnetic flux density is low around 90 degrees from the north and south poles. Have.

  As will be apparent from the operation principle described later, the number of magnetic yokes 2 (the number of gaps 3) may be two or more, and the shape of each magnetic yoke 2 and the circumferential angle formed by the gaps 3 are arbitrary. However, the example shown here is used.

  The gap 3 is provided for inserting a sensor, and the gap 3 is preferably narrowed so that a large amount of magnetic flux from the circular magnet 1 enters the magnetic yoke 2.

  In the illustrated rotation angle sensor, the magnetic yoke 2 is provided with four fan-shaped magnetic yokes 2a, 2b, 2c, and 2d having the same shape so as to divide the circumference of the circular magnet 1 into four equal parts, and the gap 3a is provided every 90 degrees of the circumferential angle. , 3b, 3c, 3d, and linear Hall sensors 4a, 4d are respectively installed in two gaps 3a, 3d having different circumferential angles of 90 degrees. The linear Hall sensors 4a and 4d are each connected to an A / D converter 6 so that the output signal is digitized and input to the arithmetic circuit 5.

  This rotation angle sensor obtains a rotation angle (absolute rotation angle) within one rotation. The operation will be described below.

  The magnetic flux that has exited almost radially outward from the N pole of the circular magnet 1 enters the magnetic yoke 2, is guided in the circumferential direction by the magnetic yoke 2, travels to the S pole side, and passes through the other magnetic yoke 2 via the gap 3. Then, it goes out radially inward toward the south pole of the circular magnet 1 and returns to the south pole. At this time, since the linear Hall sensors 4a and 4d are at positions shifted by 90 degrees from each other, when one is positioned in the vicinity of the N pole or the S pole, the other is positioned around 90 degrees from the N pole and the S pole. is doing. Thus, for example, when the output signal of one linear Hall sensor 4a is large, the output signal of the other linear Hall sensor 4d is small. When the circular magnet 1 rotates, the positions of the linear Hall sensors 4a and 4d with respect to the magnetic poles change, so that the respective output signals change.

Depending on which direction the sensing direction of the linear Hall sensors 4a and 4d is directed,
Since the angles of the N pole and the S pole where the output signal becomes maximum can be known in advance, the rotation angle can be obtained from the change in the output signal.

  As shown in FIG. 2, the horizontal axis represents the rotation angle of the circular magnet 1, the vertical axis represents the magnitude of the output signal representing the N polarity facing upward, and the magnitude of the output signal representing the S polarity facing downward. Thus, the output signal 21 of the linear Hall sensor 4a and the output signal 22 of the linear Hall sensor 4d are drawn. The output signal 21 linearly changes from the maximum value of S polarity (in this example, when the rotation angle = 0 degree) to 0 (90 degrees), and further linearly to the maximum value of N polarity (180 degrees). From then on, the change is reversed and changes linearly up to the maximum value of S polarity (360 degrees). On the other hand, the output signal 22 linearly changes from 0 (0 degree) to the maximum value of N polarity (90 degrees), and then linearly changes to the maximum value of S polarity (270 degrees). It changes linearly to 0 (360 degrees).

  As described above, the output signals 21 and 22 of the two linear Hall sensors 4a and 4d change in phase by 90 degrees. Looking at the combination of the output signals 21 and 22, there is no same pattern from 0 degrees to just before 360 degrees. That is, when the value of the output signal 21 is α, there is only one rotation angle of 360 ° where the value of the output signal 22 is β. Therefore, the rotation angle of the circular magnet 1 can be obtained from the combination of the output signals 21 and 22.

  If the circular magnet 1 is attached to the steering shaft and the linear Hall sensors 4a and 4d are fixed to the vehicle, the rotation angle of the circular magnet 1 is the rotation angle of the steering shaft.

  In the arithmetic circuit 5, the relationship between the rotation angle and the combination of the magnetic flux density detected by the magnetic element 4 (that is, the output signals 21 and 22 of the linear Hall sensors 4 a and 4 d) while the circular magnet 1 makes one rotation around the axis. Is stored in advance in a table (not shown), and the rotation angle is obtained by referring to the table based on the combination of the detected magnetic flux densities. As a result, a rotation angle within one rotation, that is, an absolute rotation angle is output.

  Next, the rotation angle sensor of the present invention is configured as shown in FIG. 3 so that the rotation angle of the circular magnet can be roughly determined and the number of rotations of the circular magnet can be determined.

  As shown in FIG. 3, in the rotation angle sensor according to the present invention, reed switches 31 that are opened and closed by a change in magnetic flux density are installed in at least two gaps 3, respectively, and an arithmetic circuit 32 is connected to each of the reed switches 31. The rotational angle formed by the circular magnet 1 with respect to the magnetic yoke 2 is roughly determined from the combination of opening and closing. The conditions regarding the number of magnetic yokes, the shape, and the circumferential angle of the gap are the same as those in the case where the magnetic element 4 is provided, but here the circular magnet 1, the magnetic yoke 2, and the magnetic element 4 in the rotation angle sensor of FIG. A description will be given of a case in which the reed switches 31b and 31c are respectively installed in the two gaps 3b and 3c having the same shape and arrangement and having a circumferential angle of 90 degrees.

  The arithmetic circuit 32 includes input trigger detection circuits 33b and 33c and pulse generation circuits 34b and 34c for the respective reed switches 31b and 31c, and an up / down counter 35. The input trigger detection circuit 33b outputs a logical value 1 when the reed switch 31b is closed, and outputs a logical value 0 when the reed switch 31b is open (the logic may be reversed). The pulse generation circuit 34b is a circuit that is triggered at the first rising edge of the output of the input trigger detection circuit 33b and changes to a logical value 1, and is triggered at the second rising edge and changes to a logical value 0 (rising). A falling edge may be used). The input trigger detection circuit 33c and the pulse generation circuit 34c are also circuits that perform the same operation.

  The up / down counter 35 up-counts or counts down the count value according to an event (rising, falling, order, etc.) generated in the output signals of the pulse generation circuits 34b and 34c, thereby providing a rough accuracy (angle resolution 90 °). ) Represents the absolute rotation angle.

  This rotation angle sensor can determine the absolute rotation angle with an infinite number of rotations within the range of the maximum value of the up / down counter 35.

  The movement of the reed switches 31b and 31c will be described. The state of the magnetic flux emitted from the circular magnet 1 has already been described with reference to FIG. At this time, since the reed switches 31b and 31c are at positions shifted by 90 degrees from each other, when one is positioned near the N pole or the S pole, the other is positioned around 90 degrees from the N pole and the S pole. Yes. Thus, for example, when one reed switch 31b is closed, the other reed switch 31c is open (each reed switch 31b, 31c has its magnetic force and repulsive force adjusted so as to open and close in this way. And). When the circular magnet 1 rotates, the positions of the reed switches 31b and 31c with respect to the magnetic poles change, so that the respective open / close states change.

  As shown in FIG. 4, the rotation angle of the circular magnet 1 (however, the 0-degree standard is different from that of FIG. 2) is taken on the horizontal axis (see the horizontal axis with the highest scale), and the N polarity in the gap 3 Taking the vertical axis with the magnetic field strength of S (the magnetic element 4 as shown in FIG. 1 can be taken out as the magnitude of the output signal) upward and the magnetic field strength of S polarity downward, A magnetized pattern 41 obtained from the gap 3b and a magnetized pattern 42 obtained from the gap 3c are drawn. This represents a change in the strength of the magnetic field appearing in each of the gaps 3b and 3c as the circular magnet 1 rotates.

  With respect to the horizontal axis drawn on the same scale as the horizontal axis of the magnetized patterns 41, 42, the open / close waveforms (logical value waveforms of the input trigger detection circuits 33b, 33c) 43, 44 of the two reed switches 31b, 31c, 2 The logic value waveforms 45 and 46 of the two pulse generation circuits 34b and 34c are drawn.

  Looking at these waveforms, when the rotation angle is 0 degree, the reed switch 31b is closed and has a logical value of 1, but when the rotational angle is slightly increased, the reed switch 31b is opened and has a logical value of 0. The reed switch 31b closes to a logical value 1 just before the rotation angle is 180 degrees, and the reed switch 31b opens to a logical value 0 when the rotation angle is slightly increased from 180 degrees. Thus, opening and closing are repeated each time the rotation angle of the circular magnet 1 increases by 180 degrees, and the opening and closing waveform 43 of the reed switch 31b becomes a pulse waveform.

  Since the pulse generation circuit 34b outputs one pulse with 50% duty every time two pulses are received from the input trigger detection circuit 33b, the logical value waveform 45 of the pulse generation circuit 34b is logically from 0 degree to 180 degrees before. Value 1, a pulse waveform of logical value 0 from a little before 180 degrees to a little 360 degrees before, a logical value 1 from a little before 360 degrees to 360 degrees, and even if the rotation angle of the circular magnet 1 is 720 degrees, 1080 degrees, etc. Repeat the same thing.

  The open / close waveform 44 of the reed switch 31c and the logic value waveform 46 of the pulse generation circuit 34c need not be described any more, and it is clear that the phase changes by 90 degrees with respect to the open / close waveform 43 and the logic value waveform 45. is there.

  Looking at the combination of the logical values of the two logical value waveforms 45 and 46, four different patterns are obtained every 90 degrees from slightly before 0 degrees to slightly 360 degrees. Therefore, the rotation angle of the circular magnet 1 can be roughly determined from this pattern (specifically, with a resolution of 90 degrees).

  The up / down counter 35 of the arithmetic circuit 32 changes the count value in accordance with an event occurring in the output signals of the pulse generation circuits 34b and 34c. That is, a history of change in combination of opening and closing of the reed switches 31b and 31c is held as a count value. The number of rotations of the circular magnet 1 can be obtained from this count value.

  In this way, the rotation angle sensor of FIG. 3 can determine the number of rotations of the circular magnet 1.

  Next, the rotation angle sensor of the present invention is configured as shown in FIG. 5 so that the absolute rotation angle in a plurality of rotations can be obtained with high resolution.

  Since the configuration of FIG. 5 is a combination of the configuration of FIG. 1 and the configuration of FIG. The arithmetic circuit 51 includes, in addition to the arithmetic circuit 5 and the arithmetic circuit 32, a rotation number acquisition circuit 52 that acquires the number of rotations output from the calculation circuit 32, and a rotation angle corresponding to the rotation number by multiplying the rotation number by 360 degrees. The calculated rotation angle is added to the absolute rotation angle within one rotation output from the arithmetic circuit 5, so that the rotation angle that accumulates from 0 degrees and continues beyond 360 degrees without being canceled, that is, the absolute rotation And an absolute rotation angle calculation circuit 53 for obtaining an angle.

  1 and FIG. 3 have been described in detail, so that the description thereof will not be required here. However, the rotation number of the circular magnet 1 output by the rotation angle sensor of FIG. The rotation angle of one large rotation such as 720 degrees, 1080 degrees, etc. is obtained, and the high-resolution absolute rotation angle output from the rotation angle sensor of FIG. 1 is added.

  The configuration of FIG. 5 further includes a configuration for power saving. That is, the arithmetic circuit 51 determines the circular magnet 1 from the combination of the rough arithmetic circuit 32 that roughly determines the rotation angle that the circular magnet 1 makes with respect to the magnetic yoke 2 from the combination of opening and closing of the reed switch 31, and the magnetic flux density detected by the magnetic element. And the fine calculation circuit 5 for determining the rotation angle made by the magnetic yoke 2 and when the rough calculation is sufficient, the power supply to the fine calculation circuit 5 and the magnetic element 4 is stopped and only the rough calculation circuit 32 is supplied with power. And a power-saving control circuit (not shown) that supplies power to the dense arithmetic circuit 5 and the magnetic element 4 together with power supply to the coarse arithmetic circuit 32 only when dense arithmetic is required.

  The detailed members and circuit configuration of the power saving control circuit will not be described, but the circuit that constantly supplies power within the broken line in FIG. 5 and supplies power only when necessary in other parts can be easily realized in various forms. it can.

  Here, since the reed switch 31 is a contact that is opened and closed by magnetic force, no driving power is required. In addition, the rough calculation circuit 32 that performs the rough rotation angle detection and the rotation number detection with a resolution of 90 degrees can be configured by an extremely small number of logic circuits, and thus consumes little power. On the other hand, the magnetic element 4 consumes a large amount of power, and the dense arithmetic circuit 5 is composed of a microcomputer. Therefore, if the power saving control circuit performs power supply to the dense arithmetic circuit 5 and the magnetic element 4 only when necessary, only the coarse arithmetic circuit 32 and the power saving control circuit need to have power in other cases. , Power consumption can be greatly reduced. Since the number of rotations can be detected in the rough calculation circuit 32, if the absolute rotation angle within one rotation is detected by supplying power to the fine calculation circuit 5 when necessary, the absolute rotation angle in a plurality of rotations can be obtained. As a result, this power-saving control is not a limitation or an obstacle to absolute rotation angle detection.

  In the rotation angle sensor of FIG. 1 and FIG. 5, four sector magnetic yokes 2a, 2b, 2c and 2d having the same shape are provided as the magnetic yoke 2 so as to divide the circumference of the circular magnet 1 into four equal parts. Although the gaps 3a, 3b, 3c, and 3d are formed every 90 degrees, since this structure is a structure in which the magnetic element 4 is surrounded by the magnetic yoke 2, external noise to the magnetic element 4 can be reduced by the magnetic shielding effect by the magnetic yoke 2. .

  Further, according to the above structure, since the magnetic element 4 is surrounded by the magnetic yoke 2, the fluctuation of the output signal of the magnetic element 4 due to the eccentricity of the shaft is small.

  FIG. 6 shows an example in which a rotation angle sensor for detecting the steering angle by the steering shaft is mounted on the vehicle. The main part of the vehicle includes a handle 61, a torsion bar 62 that transmits the rotation of the handle 61, a steering shaft 63, and a power mechanism (not shown) that increases the rotational force applied to the torsion bar 62 and transmits it to the steering shaft 63. ), A pinion 64 provided at the tip of the steering shaft 63, a rack 65 meshing with the pinion 64, and left and right drive wheels 66 and 67 connected to both ends of the rack 65.

  The circular magnet 1 described so far is provided coaxially with the steering shaft 63 at the steering angle detector 68 at the base end of the steering shaft 63, and the circular magnet 1 is rotated at the same rotational angle as the steering shaft 63 rotates. It is designed to rotate. The magnetic yoke 2, the magnetic element 4, and the reed switch 31 are disposed so as to surround the circular magnet 1 and are fixed to the vehicle. The arithmetic circuit 51 is connected to a signal line appropriately routed from the magnetic element 4 and the reed switch 31, and is provided at an appropriate location in the vehicle. The signal lines for the absolute steering angle, rough steering angle, and number of rotations output from the arithmetic circuit 51 are connected to a motion control controller 69 that controls the overall motion of the vehicle. It is assumed that power is always supplied within the broken line in the arithmetic circuit 51 without passing through the main power switch of the vehicle.

  If the steering angle is detected by the conventional rotation angle sensor, the absolute steering angle cannot be detected immediately after the main power supply is turned on in the vehicle, so the absolute steering angle cannot be detected. It was necessary to rotate the steering shaft by turning the steering wheel. On the other hand, if the steering angle is detected by the rotation angle sensor of the present invention, the absolute steering angle can be detected immediately even after the main power is turned on in the vehicle.

  In addition, the conventional rotation angle sensor has to supply power to the optical encoder module, the MR sensor, and the microcomputer (arithmetic circuit) regardless of whether the steering angle is detected. On the other hand, in the rotation angle sensor of the present invention (the form shown in FIG. 5), power supply to the microcomputer (fine calculation circuit 5) and the magnetic element 4 can be cut except when necessary. This is useful for avoiding the serious situation of battery exhaustion in a vehicle that uses the battery.

  Since the absolute steering angle can be detected by the rotation angle sensor of the present invention, it is possible to provide one element technology necessary for future automatic steering of the vehicle. It can also be used for self-contained navigation using a car navigation system.

It is an axial sectional structure figure of a rotation angle sensor showing one embodiment of the present invention. It is a wave form diagram of the output signal of the magnetic element in the rotation angle sensor of FIG. It is an axial sectional structure figure of a rotation angle sensor showing one embodiment of the present invention. FIG. 3 is a waveform diagram of a magnetic field change and each part of an arithmetic circuit in the rotation angle sensor of FIG. 2. It is an axial sectional structure figure of a rotation angle sensor showing one embodiment of the present invention. It is a block diagram of the steering angle detection system using the rotation angle sensor of this invention. It is an axial cross-section figure of the conventional rotation angle sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Circular magnet 2 Magnetic yoke 2a, 2b, 2c, 2d Fan-shaped magnetic yoke 3, 3a, 3b, 3c, 3d Gap 4 Magnetic element 4a, 4d Linear Hall sensor 5 Calculation circuit (fine calculation circuit)
31, 31b, 31c Reed switch 32 arithmetic circuit (coarse arithmetic circuit)
51 Arithmetic circuit

Claims (8)

  A plurality of magnetic yokes are arranged so as to annularly surround a circular magnet having magnetic poles in the radial direction, and the adjacent magnetic yokes are separated from each other in the circumferential direction to form at least two gaps. A magnetic element for detecting a magnetic flux density is installed in each gap, and an arithmetic circuit for obtaining a rotation angle of the circular magnet with respect to the magnetic yoke from a combination of magnetic flux densities detected by the magnetic elements is provided. Rotation angle sensor.   2. The rotation angle sensor according to claim 1, wherein at least two gaps having a circumferential angle of 90 degrees are formed, and the magnetic element is installed in each of the two gaps.   The arithmetic circuit previously stores in a table the relationship between the combination of magnetic flux density detected by the magnetic element and the rotation angle while the circular magnet makes one rotation around the axis, and the detected combination of magnetic flux densities. The rotation angle sensor according to claim 1 or 2, wherein the rotation angle is obtained by referring to the table.   Reed switches that are opened / closed by a change in magnetic flux density are installed in at least two gaps, and the arithmetic circuit roughly obtains a rotation angle of the circular magnet with respect to the magnetic yoke from a combination of opening / closing of these reed switches. The rotation angle sensor according to any one of claims 1 to 3.   The arithmetic circuit obtains the number of rotations of the circular magnet from the history of change in combination of opening and closing of the reed switch, and adds the rotation angle obtained from the combination of magnetic flux densities detected by the magnetic element to the number of rotations × 360 degrees. 5. The rotation angle sensor according to claim 4, wherein a cumulative rotation angle is obtained.   The arithmetic circuit comprises: a rough arithmetic circuit that roughly obtains a rotation angle of the circular magnet with respect to the magnetic yoke from a combination of opening and closing of the reed switch; and the circular magnet is determined from the combination of magnetic flux densities detected by the magnetic element. A fine arithmetic circuit for obtaining a rotation angle made with respect to the magnetic yoke, and when the coarse arithmetic is sufficient, the fine arithmetic circuit and the magnetic element are stopped from being supplied with power, and only when the fine arithmetic is necessary, the fine arithmetic circuit and 6. The rotation angle sensor according to claim 4, further comprising a power saving control circuit for supplying power to the magnetic element.   4. The magnetic yoke is provided with four fan-shaped magnetic yokes so as to divide the circumference of the circular magnet into four parts, and the magnetic elements are respectively installed in two gaps having different circumferential angles by 90 degrees. 6. The rotation angle sensor according to any one of 6. 8. The rotation angle sensor according to claim 7, wherein reed switches that are opened and closed by changing the magnetic flux density are respectively installed in the remaining two gaps.

Images