JP2007322267A - Rotation angle detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotation angle detection device capable of more secure angle detection, even when axial runout occurs in a detection object shaft. <P>SOLUTION: When being used in a system having a small tolerance on the side wherein an output voltage showing a detection result is small, and having a large tolerance on the side wherein the output voltage is large, in this rotation angle detection device, a magnetic neutral position is set so that a fluctuation width of the detection result resulting from runout of a shaft 15 in the direction (C direction) wherein the runout of the shaft 15 which is a detection object shaft becomes maximum becomes larger in proportion to largeness of a detection allowance carried by each rotation angle. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rotation angle detection device.

  Conventionally, various rotation angle detection devices have been proposed. Patent document 1 discloses the rotation angle detection apparatus as the example.

In the rotation angle detection device of Patent Document 1, a permanent magnet is provided on the detection target shaft side that rotates relative to the fixed portion side, and between the permanent magnet and the fixed portion side as the permanent magnet rotates. The magnetic flux density to be formed is configured to change, and the rotation angle of the detection target shaft is detected by detecting the change in the magnetic flux density with a detection element provided on the fixed portion side.
JP 2001-208510 A

  The detection target shaft that is a detection target by this type of rotation angle detection device may cause shaft runout due to its configuration. Specifically, for example, when the detection target shaft is cantilevered, the shaft runout becomes larger than when both ends are supported, or the detection target shaft includes a cam, and the cam In the case where the force is applied in a specific direction, the detection target shaft is greatly shaken in the specific direction (and the reverse direction) by receiving a reaction force in a direction opposite to the specific direction. In addition, when the attachment object to which the rotation angle detection device is attached vibrates strongly in a specific direction, the shake of the detection target axis in the specific direction increases due to the influence of the vibration of the attachment object.

  On the other hand, the inventor conducted earnest research on the mounting posture (setting of the magnetic neutral position) of the rotation angle detection device with respect to the attachment object. Even when the same rotation angle detection device is used, Depending on the mounting orientation, the fluctuation range of the detection result due to the shake of the detection target axis may exceed the allowable error range (allowable range) in the control, and the system that uses the detection result may not be established. It has been found.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to obtain a rotation angle detection device that enables more reliable angle detection even when a shaft runout occurs on a detection target shaft.

  In order to achieve the above object, according to the first aspect of the present invention, in the rotation angle detecting device, the fluctuation range of the detection result accompanying the shake of the detection target axis in the direction in which the shake of the detection target axis is maximum is an allowable detection. The gist is that the magnetic neutral position is set so that the larger the rotation angle, the larger the error.

  According to a second aspect of the present invention, in the rotation angle detection device, the output voltage is set such that the output voltage increases as the rotation angle has a larger allowable detection error, and the detection target axis in a direction in which the deflection of the detection target axis is maximum. It is intended that the magnetic neutral position is set so that the fluctuation range of the output voltage due to the fluctuation of the angle becomes larger as the rotation angle of the output voltage corresponding to the detection result increases.

  According to the first aspect of the present invention, by appropriately setting the axial deflection direction of the detection target shaft and the direction of the magnetic neutral position of the rotation angle detection device, an angle that requires a small detection error and a high detection accuracy is required. While it is possible to reduce the fluctuation of the detection result due to the shake of the detection target axis in the range, the fluctuation of the detection result due to the shake of the detection target axis should be increased in the angle range where the tolerance is large and the detection accuracy is relatively low. Therefore, it becomes easy to ensure the required detection accuracy over a wider range of detection angles.

  According to the second aspect of the present invention, the axial deflection direction of the detection target shaft and the direction of the magnetic neutral position of the rotational angle detection device are appropriately set, and the increase / decrease of the output voltage relative to the rotational direction is appropriately set. Thus, in the angle range where the tolerance is small and the output voltage of the detection result is small, the output fluctuation accompanying the shake of the detection target axis can be reduced, while the output voltage of the detection result is large and the output voltage of the detection result is large. Then, since the output fluctuation accompanying the shake of the detection target axis can be increased, it is easy to ensure the required detection accuracy over a wider range of detection angles.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments embodying the invention will be described with reference to the drawings. FIG. 1 is an exploded perspective view showing a mounting structure of a rotation angle detection device according to this embodiment, FIG. 2 is a view showing the rotation angle detection device, (a) is a plan view, and (b) is a plan view. FIG. 3 is a schematic side view of the magnetic circuit of the rotation angle detection device, and FIG. 4 shows the output voltage of the detection result by the rotation angle detection device and the fluctuation range of the output voltage due to the shaft runout of the detection target shaft. 4A and 4B are diagrams illustrating an example of the correlation of the two, where (a) is a diagram illustrating the axial runout direction (four directions A to D), and (b) is a side view schematically illustrating the axial runout of the detection target axis. , (C) is a graph illustrating the correlation between the output voltage and the fluctuation range of the output voltage due to shaft runout.

  The rotation angle detection device 1 according to the present embodiment is attached to the attachment object 11 on the shaft end side of a shaft 15 as a detection object axis.

  That is, the rotation angle detection device 1 includes a cylindrical body 1a as a casing made of a molded resin, and a pair of flange portions 1f and 1f projecting laterally from the side surface of the cylindrical body 1a. The cylindrical body 1a is fitted into a circular hole 11a formed in the attachment object 11, and the flange portions 1f, 1f are abutted against the surface of the attachment object 11, and are elongated holes formed in the flange portions 1f, 1f. By screwing a screw or bolt (not shown) penetrating the through hole 1g into a female screw hole (not shown) formed on the surface of the attachment object 11, the opening of the circular hole 11a is closed. Attached to the attachment object 11. As shown in FIG. 2, it is preferable that an O-ring 12 is attached to the insertion portion of the cylindrical body 1a into the circular hole 11a to ensure a seal in the gap between the circular hole 11a and the cylindrical body 1a. It is.

  Further, a concave portion 1b is formed on the surface side of the cylindrical body 1a (upper side in FIGS. 1 and 2B), and an electronic component such as a capacitor is mounted on the bottom surface of the concave portion 1b as a substrate. 9 is formed. A cover 1c bulging in a dome shape is attached so as to cover the opening of the recess 1b.

  In addition, a connector 1d is provided at one end of the cylindrical body 1a, and a detection result (voltage) is externally output via the connector 1d and a connector (not shown) coupled to the connector 1d. It has come to be. A conductor 10 electrically connected to the circuit 9 is insert-molded in the cylindrical body 1a and used as a connection terminal in the connector 1d (see FIG. 2).

  On the other hand, the attachment 13 is fixed to the tip of the shaft 15 as a detection target shaft that rotates relative to the attachment target 11 by press-fitting or bonding, and the permanent magnet 2 is fixed to the shaft 15 side. .

  Here, with reference to FIG. 3, the magnetic circuit of the rotation angle detection apparatus 1 concerning this embodiment is demonstrated.

  As shown in FIG. 3, the magnetic circuit includes a permanent magnet 2 that rotates in conjunction with the shaft 15, and a pair of yokes 3, 4 that are provided on the outer circumference of the permanent magnet 2 so as to face each other. It is configured with.

  The permanent magnet 2 is magnetized in the radial direction (along the diameter). As described above, the permanent magnet 2 is formed in an annular disk shape (see FIG. 1), but in FIG. 3, a direction perpendicular to the magnetization direction is cut out for easy understanding of the magnetization direction. The shape is schematically shown.

  The yokes 3 and 4 have arc-shaped magnetic pole piece portions 3a and 4a centering on the rotation center M of the permanent magnet 2, and connecting portions 3c and 4c facing each other with two parallel hall elements 5 and 6 interposed therebetween. And intermediate portions 3b and 4b for connecting the magnetic pole piece portions 3a and 4a and the connecting portions 3c and 4c, respectively. These yokes 3 and 4 correspond to fixed portions.

  The two magnetic pole piece portions 3a and 4a are each provided in an arc shape over a range of about 90 ° with respect to the rotation center M of the permanent magnet 2, and between the two magnetic pole piece portions 3a and 4a, By setting the arc-shaped isolation sections 7 and 8 each extending over a range of approximately 90 °, a magnetic path is not directly formed between the two magnetic pole piece portions 3a and 4a.

  Further, a substantially constant gap is formed between the outer peripheral surface of the permanent magnet 2 and the magnetic pole piece portions 3a and 4a regardless of the rotation angle of the permanent magnet 2.

  In such a configuration, when the magnetization direction of the permanent magnet 2 is directed in a direction θo (vertical direction in FIG. 3) perpendicular to a line (left-right direction in FIG. 3) connecting the centers of the two magnetic pole piece portions 3a and 4a. The magnetic flux density is the lowest. Therefore, the position of the permanent magnet 2 at this time becomes the magnetic neutral position θo.

  When the permanent magnet 2 is rotated from the magnetic neutral position θo, a magnetic path passing through the permanent magnet 2 and the yokes 3 and 4 is formed and the magnetic flux density is increased, and the rotation direction of the permanent magnet 2 is increased. Although the direction of the magnetic path differs depending on (clockwise or counterclockwise), the magnetic flux density increases as the rotation angle (θ) of the axis along the longitudinal direction of the permanent magnet 2 with respect to the magnetic neutral position θo increases. The magnetic flux density is the highest in a posture in which both end portions in the longitudinal direction of the permanent magnet 2 are oriented toward the centers of the magnetic pole piece portions 3a and 4a (that is, the posture in which the permanent magnet 2 extends in the left-right direction in FIG. 3).

  In the present embodiment, an angle detection range (angle detectable range) X (θa to θb) having a substantially equal angle range on both sides around the magnetic neutral position θo is set. In this range X, the magnetic flux density changes substantially linearly (substantially as a linear function) with respect to the rotation angle, but in this embodiment, as an example, the output voltage of the rotation angle detection device 1 is The magnetic flux density is set (adjusted) so that the minimum value is obtained at the rotation angle θa having the smallest magnetic flux density and the maximum value is obtained at the rotation angle θb having the largest magnetic flux density.

  In addition, as long as it is within the range of the angle detection range X, it is not essential to set the range used for actual angle detection symmetrically about the magnetic neutral position θo. The range used for angle detection is the casing for the mounting direction (magnetization direction) of the permanent magnet 2 with respect to the shaft 15 as the detection target axis, the arrangement of the yokes 3 and 4, and the circular hole 11 a formed in the mounting target 11. Those skilled in the art will readily understand that the cylindrical body 1a can be appropriately set or adjusted by changing the mounting angle (rotation posture) or the like. Further, in order to perform such adjustment (particularly fine adjustment), as shown in FIG. 2A, a through hole 1g provided in the flange portions 1f and 1f is an elongated hole along an arc centered on the rotation center M. It is possible to adjust the attachment angle around the rotation center M with respect to the attachment object 11 of the cylindrical body 1a as a casing.

  The rotation angle detection device 1 having the above configuration may be used in a system in which the tolerance increases as the rotation angle of the shaft 15 as the detection target axis, that is, the permanent magnet 2 increases in one rotation direction. is there.

  As an example, in a variable valve operating apparatus for an internal combustion engine, this corresponds to a case where the rotation angle of a control shaft (detection target shaft) for controlling the lift amount is detected. That is, the rotation of the camshaft of the internal combustion engine is converted into the swing of the swing cam via a link mechanism consisting of a plurality of link members, and the intake or exhaust valve of the internal combustion engine is driven to open and close by the swing cam. An intake valve or an exhaust gas that is driven to open and close by the swing cam by variably setting the swing center of one link member in the link mechanism using an eccentric cam provided on a control shaft that is rotatable with respect to the portion. With respect to a variable valve apparatus that variably controls the lift amount of the valve, a permanent magnet provided on the fixed portion side or the control shaft side and the permanent magnet is formed so as to pass through the fixed portion side and the control shaft side. And a rotation angle detection device that detects a rotation angle of the control shaft with respect to the fixed portion based on a change in the magnetic flux density.

  In such a case, a high detection accuracy is required at one rotation angle (for example, θa), and a low detection accuracy is sufficient at the other rotation angle (the same θb).

  In many cases, the output voltage is set to be small on the angle side where high detection accuracy is required and the output voltage is set to be large on the angle side where detection accuracy may be low.

  Here, the inventors conducted extensive studies on the detection error (variation width) due to the shaft runout of the shaft 15 as the detection target axis. As a result, the shaft 15 has a large shaft runout and the magnetic neutral position θo. It was found that the detection results due to shaft runout differ greatly depending on their relative positional relationship. That is, depending on the setting of the magnetic direction (direction of the magnetic neutral position θo) of the rotation angle detection device 1 with respect to the axial deflection direction (maximum direction) of the detection target shaft, the fluctuation range due to the axial deflection causes a detection allowable error. It has been found that even in such a case, by changing the setting, the fluctuation range due to the shaft runout can be kept within the detection tolerance for a wide angle range.

  FIG. 4 shows an example thereof, in which the yokes 3 and 4 are fixed to the rotation angle detection device 1 and the permanent magnet 2 is fixed to the shaft 15 (for example, the yokes 3 and 4 are in the direction D in FIG. 4). In the state where the magnetization direction of the permanent magnet 2 coincides with the C direction when the magnetic neutral position θo is at the magnetic neutral position θo). 4 is changed into four patterns A to D as shown in FIG. 4 (a), the fluctuation range of the output voltage (detection result) due to the shaft shake with respect to the output voltage (detection result) is They are different as shown in FIG. In FIG. 4C, the upper limit and the lower limit of the fluctuation range are indicated by each line, and the larger the interval between the two upper and lower lines, the greater the fluctuation range. FIG. 4B is a side view showing the state of shaft runout of the shaft 15.

  Specifically, first, when the shaft shake direction of the shaft 15 is the A direction, the fluctuation range of the output voltage due to the shaft shake is large over the entire detection range (that is, from an angle where the output voltage is small to a large angle). It was found that the state remained unchanged. In this case, if the detection tolerance of the system is small on the angle side where the output voltage is small, and the detection tolerance of the system is large on the angle side where the output voltage is large, the fluctuation range is within the detection tolerance in the system in the angle region where the output voltage is small. The error will be exceeded and the system will no longer be usable.

  Next, when the shaft runout direction of the shaft 15 is the B direction, the fluctuation range of the output voltage (detection angle) due to the shaft runout from the small angle to the large angle (width between the two dash-dot lines). Is linearly smaller. In this case as well, if the detection tolerance of the system is small on the angle side where the output voltage is small and the detection tolerance of the system is large on the angle side where the output voltage is large, the fluctuation range will be the detection tolerance in the system in the angle region where the output voltage is small. The error will be exceeded and the system will no longer be usable.

  Next, when the shaft runout direction of the shaft 15 is the C direction, the fluctuation width (width between two broken lines) of the output voltage (detection angle) due to shaft runout from a small angle to a large angle of the output voltage is It grows linearly. In this case, if the system detection tolerance is small on the angle side where the output voltage is small and the system detection tolerance is large on the angle side where the output voltage is large, the fluctuation range may fall within the tolerance for the entire angle range. It becomes possible.

  Next, when the shaft runout direction of the shaft 15 is the D direction, the fluctuation range of the output voltage (detection angle) due to the shaft runout is large between the case where the output voltage is a small angle and the case where the output voltage is a large angle. For a given angle, the fluctuation range of the output voltage due to the shaft runout is small. In this case as well, if the detection tolerance of the system is small on the angle side where the output voltage is small and the detection tolerance of the system is large on the angle side where the output voltage is large, the fluctuation range will be the detection tolerance in the system in the angle region where the output voltage is small. The error will be exceeded and the system will no longer be usable.

  Therefore, in the above four cases, when the system detection tolerance is small on the angle side where the output voltage is small and the system detection tolerance is large on the angle side where the output voltage is large, the shaft runout direction is as shown in FIG. Only the C direction will fit the system.

  As described above, according to the present embodiment, if the axial deflection direction of the shaft 15 as the detection target axis and the direction of the magnetic neutral position θo of the rotation angle detection device 1 are appropriately set, the axis of the shaft 15 The fluctuation range of the detection result due to the shake of the shaft 15 in the direction in which the shake is maximum (C direction in the above example) increases as the allowable detection error increases, and the configuration allowable error is small and high detection accuracy is required. While it is possible to reduce the fluctuation of the detection result due to the shake of the shaft 15 as the detection target axis in the range, the fluctuation of the detection result due to the shake of the detection target axis in the angle range where the tolerance is large and the detection accuracy is relatively low. Therefore, it is easy to ensure necessary detection accuracy over a wider range of detection angles.

  According to the present embodiment, furthermore, by appropriately setting the increase / decrease of the output voltage with respect to the rotation direction of the shaft 15, that is, in the example of FIG. 4, the output voltage is lowered on the side where high detection accuracy is required. On the other hand, by increasing the output voltage on the side where the pull detection accuracy is good, it is possible to reduce the output fluctuation due to the shake of the detection target axis in the angle range where the tolerance is small and the output voltage of the detection result is small. In the angle range where the output voltage of the detection result is large and the output voltage of the detection result is large, the output fluctuation due to the shake of the detection target axis can be increased, so the necessary detection accuracy is ensured over a wider range of detection angles. It becomes easy.

  Further, according to the present embodiment, since it becomes easy to ensure the required detection accuracy even for a system in which the shaft deflection of the detection target shaft is larger, the bearing of the detection target shaft is omitted, thereby reducing cost and downsizing. There is an advantage of being able to plan.

  The present invention can be embodied in another embodiment as follows. In other embodiments described below, the same operations and effects as in the above embodiments can be obtained.

  (1) First, the basic configuration of the rotation angle detection device is not limited to the above embodiment, and any permanent magnet can be used as long as the magnetic flux density is changed according to the rotation of the detection target shaft. May be provided on the fixed portion side.

  (2) Also, depending on the attachment object, shaft runout may occur in various directions. In such a case, it is preferable to adjust the direction in which the shaft runout is maximum.

  (3) Further, the object whose angle is to be detected is not limited to the control shaft of the variable valve operating device of the internal combustion engine, but can be variously applied to the shaft of the throttle valve of the internal combustion engine.

  Further, technical ideas other than the claims that can be grasped from the above embodiment will be described together with the effects thereof.

  (A) The rotation angle detection device according to claim 1 detects the rotation angle of the end portion of the detection target shaft that is cantilevered and supported by the attachment object of the rotation angle detection device. Is preferred.

  In this way, a bearing or the like for supporting both ends of the detection target shaft can be omitted, the apparatus configuration can be made smaller, and the manufacturing cost can be reduced. Further, even when the shaft runout becomes larger as compared with the case where both ends are supported by the cantilever support, the required detection accuracy can be ensured by the configuration of claim 1.

The disassembled perspective view which shows the attachment structure of the rotation angle detection apparatus concerning embodiment of this invention. It is a figure which shows the rotation angle detection apparatus concerning embodiment of this invention, Comprising: (a) is a top view, (b) is a sectional side view. The schematic diagram which shows the magnetic circuit of the rotation angle detection apparatus concerning embodiment of this invention. It is a figure which shows the correlation with the fluctuation range of the output voltage by the axial fluctuation of the detection result axis | shaft by the rotation angle detection apparatus concerning embodiment of this invention, and the detection object axis | shaft, Comprising: (a) is an axial deflection direction. The figure which shows (4 directions), (b) is a side view which shows the axial runout of a detection object axis | shaft typically, (c) illustrates the correlation with the fluctuation range of the output voltage by an output voltage and an axial runout. Graph.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotation angle detection apparatus 2 Permanent magnet 3, 4 Yoke (fixed part)
15 Shaft (Detection target axis)
θo Magnetic neutral position A to D direction Shaking direction

Claims (2)

Used in a system in which the permissible detection error of the rotation angle of the detection target shaft with respect to the fixed portion increases in one rotation direction, a permanent magnet provided on the fixed portion side or the detection target shaft side, and the fixed magnet side by the permanent magnet A rotation angle detection device that detects a rotation angle based on a change in the magnetic flux density, and a detection element that detects a magnetic flux density of a magnetic path formed so as to pass through the detection target shaft side.
The magnetic neutral position is set so that the fluctuation range of the detection result due to the shake of the detection target axis in the direction in which the shake of the detection target axis is maximum becomes larger as the rotation angle has a larger allowable detection error. A rotation angle detection device. Used in a system in which the permissible detection error of the rotation angle of the detection target shaft with respect to the fixed portion increases in one rotation direction, a permanent magnet provided on the fixed portion side or the detection target shaft side, and the fixed magnet side by the permanent magnet A rotation angle detection device that detects a rotation angle based on a change in the magnetic flux density, and a detection element that detects a magnetic flux density of a magnetic path formed so as to pass through the detection target shaft side.
It is set so that the output voltage increases as the rotation angle has a larger allowable detection error.
The magnetic neutral position is set so that the fluctuation range of the output voltage due to the shake of the detection target axis in the direction where the shake of the detection target axis is maximum becomes larger as the output voltage corresponding to the detection result is larger. A rotation angle detection device characterized by that.

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