JP2012194167A - Rotation angle detection device and electric power steering apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotation angle detection device capable of highly accurately detecting a rotation angle by correcting a detection error caused by backlash between a main gear and a detection gear by a simple configuration, and to provide an electric power steering apparatus.SOLUTION: The rotation angle detection device includes: rotation angle calculation means which calculates a rotation angle of a steering shaft based on a detection signal outputted from rotation angle detection means, and when the rotation angular speed of the steering shaft is a predetermined value or more, calculates a backlash correction value for correcting an error caused by backlash between the main gear and the detection gear from a difference between a twist angle of a torsion bar calculated based on steering torque detected by steering torque detection means and the rotation angle of the steering shaft; and rotation angle correction means for correcting the rotation angle of the steering shaft based on the backlash correction value.

Description

  The present invention relates to a rotation angle detection device and an electric power steering device.

  Conventionally, as a method for detecting the rotation angle of the steering shaft, it is composed of a main gear that is engaged with the steering shaft and rotates in conjunction with it, and a detection gear that meshes with and rotates in conjunction with the main gear, and is fixed to the rotation angle detection device. An integrated structure using a magnetic angle sensor and a magnet mounted on a rotating detection gear is known.

  However, a slight gap, that is, a so-called backlash for meshing the teeth is formed between the meshed teeth of the main gear and the detection gear. For this reason, when the right-turn and left-turn steering is repeated, the detection error of the rotation angle increases due to the backlash between the main gear and the detection gear, and the angle accuracy deteriorates. In order to reduce the rotation angle detection error caused by such backlash, a correction value for correcting the rotation delay due to backlash between the main gear and the detection gear at the time of reverse rotation is measured, and the detection error is detected based on this correction value. Correction is being performed. (For example, see Patent Document 1)

JP 2007-132585 A

However, the measurement of the backlash amount between the main gear and the detection gear is performed only at the time of assembling or shipping inspection. Since the measured value at that time is stored as a correction value, if the backlash changes due to gear wear or temperature characteristics due to secular change, the output of the corrected rotation angle may fluctuate.
For this reason, in the electric power steering device, it is an object to obtain a rotation angle detection device that can detect the rotation angle more accurately.

  The present invention has been made to solve the above-mentioned problems, and its purpose is to realize backlash correction in real time even when there is a change in gear wear and temperature characteristics, and the rotation angle of the steering shaft can be accurately adjusted. An object of the present invention is to provide a rotation angle detection device and an electric power steering device that can detect.

In order to solve the above-mentioned problems, the invention according to claim 1 is characterized in that a torque detection means for detecting a rotational torque acting between an input shaft and an output shaft of a rotating body connected to both ends of a torsion bar, and the rotation A rotation angle detecting device comprising: a main gear that rotates in conjunction with a body; a detection gear that rotates in conjunction with the main gear; and a rotation detection means that detects rotation of the detection gear as a detection signal. Calculating the rotation angle of the rotating body based on the detection signal output from the means, and calculating based on the rotation torque detected by the torque detecting means when the rotation angular velocity of the rotating body is a predetermined value or more. For correcting an error caused by backlash between the main gear and the detection gear from a difference between a twist angle of the torsion bar and a rotation angle of the rotating body. A rotation angle calculating means for calculating a Kkurasshi correction value, and summarized in that and a rotation angle correction means for correcting the rotational angle of the rotating body on the basis of said backlash correction value.

  According to the said structure, a main gear rotates in response to rotation of the rotary body which is a to-be-detected body. The rotation of the main gear is transmitted to a detection gear that meshes therewith. The rotation detection means detects the rotation of the detection gear by a detected member provided on the detection gear and a detection member facing the detected member, and a detection signal is output to the rotation angle calculation means. On the other hand, when the rotating body is reversed from rotation in one direction to the other direction, a rotation delay due to backlash between the main gear and the detection gear occurs. The rotation angle calculation means calculates the rotation angle of the rotating body based on the rotation detection signal of the detection gear and, when it is determined that the rotating body is rotating, the torsion calculated from the rotation torque detected by the torque detecting means. A backlash correction value for correcting the backlash between the main gear and the detection gear is obtained by calculation from the difference between the twist angle of the bar and the rotation angle of the rotating body calculated from the rotation detection signal of the detection gear. The rotation angle correction means corrects the calculated rotation angle of the rotating body using the backlash correction value, and can detect the rotation angle of the rotating body with high accuracy.

  Furthermore, according to the above configuration, the rotation angle calculation means can arbitrarily acquire the backlash correction value of the detection gear if the rotation angular velocity of the rotating body is equal to or greater than a predetermined value. As a result, the backlash can be corrected in real time even if there is gear wear or temperature characteristic change, and the rotation angle of the rotating body can be detected with high accuracy.

The gist of the second aspect of the present invention is that the electric power steering apparatus includes the rotation angle detection apparatus according to the first aspect.
According to the rotation angle detection device of the first aspect, since the accuracy of the detected rotation angle is improved, an electric power steering device with improved steering feeling of the vehicle can be obtained.

  It is possible to provide a rotation angle detection device and an electric power steering device capable of correcting a detection error due to backlash between the main gear and the detection gear with a simple configuration and detecting a rotation angle with high accuracy.

The conceptual diagram of an electric power steering apparatus. (a) is a top view explaining schematic structure of the rotation angle detection apparatus which concerns on this form, (b) is BB sectional drawing of Fig.2 (a). The side view seen from the arrow A direction of FIG. The flowchart figure which shows the process sequence of backlash correction value acquisition. The flowchart figure which shows the process sequence of backlash correction. The figure which shows the backlash correction value acquisition and the backlash correction method.

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.
FIG. 1 is a conceptual diagram embodying an embodiment of the present invention in a column type electric power steering apparatus.

  As shown in FIG. 1, the electric power steering apparatus 100 includes a shaft 102 between steered wheels passed between a pair of steered wheels 101, 101 provided in a vehicle 110, and an outer side of the shaft 102 between steered wheels. And a covered shaft case 103.

  Both ends of the shaft 102 between the steered wheels are connected to the steered wheels 101 and 101 via tie rods 102T and 102T, and the shaft case 103 is fixed to the main body of the vehicle 110. In addition, a rack (not shown) is formed at an intermediate portion of the inter-steering wheel shaft 102, and a pinion (not shown) penetrating the intermediate portion of the shaft case 103 from the side meshes with the rack.

  An intermediate shaft 105 (hereinafter referred to as an intermediate shaft) is connected to the upper end of the pinion, a steering shaft 106 is connected to the upper end of the intermediate shaft 105, and a steering wheel is connected to the upper end of the steering shaft 106. 107 are connected. A motor 109 is connected to a connecting portion between the intermediate shaft 105 and the steering shaft 106 via a speed reduction mechanism 108.

  A torque sensor (steering torque detection means) 112 detects a steering torque τ applied to the steering shaft 106 by operating the steering wheel 107. A rotation angle detection device 111 mounted (add-on) to the torque sensor 112 is attached to the steering shaft 106 and detects the steering angle θ of the steering wheel 107. Further, a vehicle speed sensor 113 for detecting the vehicle speed V based on the rotation of the steered wheel 101 is provided in the vicinity of the steered wheel 101.

  Then, a steering control device (hereinafter referred to as ECU) 114 drives the motor 109 according to the driving situation based on the vehicle speed V of the detection signals of the rotation angle detection device 111 and the vehicle speed sensor 113, and thereby the steering wheel by the driver. The steered wheels 101 and 101 can be steered by assisting the operation 107 with the motor 109.

  Next, FIG. 2 (a) is a plan view of the rotation angle detection device according to the embodiment of the present invention, FIG. 2 (b) is a cross-sectional view taken along the line BB of FIG. 2 (a), and FIG. It is the side view seen from the direction.

  As shown in FIGS. 2A and 2B, the main gear 1 is a rotating body made of an insulating resin having a spur gear formed on the outer periphery, and a torque sensor 112 press-fitted into a steering shaft 106 inserted through the central portion. The magnetic yoke 115 is fitted on the outer periphery. There is a detection body of the detection gear 2 that detects the rotation angle of the steering shaft 106.

  The detection gear 2 is an insulating resin detector that is rotatably supported by an insulating resin case. The spur gear on the outer periphery meshes with the spur gear of the main gear 1. A magnet 15 as a member to be detected is mounted by insert molding or the like.

  A magnetic angle sensor 16 such as a Hall IC (magnetic field detection element) serving as a detection member is provided on a surface of the circuit board 12 disposed substantially parallel to the upper space of the detection gear 2 and facing the magnet 15 of the detection gear 2. It is installed.

  The magnet 15 and the magnetic angle sensor 16 opposed to the magnet 15 formed as described above, together with the detection gear 2 to which the magnet 15 is attached and the circuit board 12 to which the magnetic angle sensor 16 is attached, are used to detect the rotation angle. 111 is arranged in a case (not shown).

  In the above configuration, when the steering wheel 107 is steered, the main gear 1 rotates in conjunction with the rotation of the steering shaft 106, and the spur gear of the detection gear 2 meshes with the spur gear on the outer periphery of the main gear 1 to rotate in conjunction with it. To do.

  The magnet 15 mounted at the center of the detection gear 2 also rotates, the magnetic angle sensor 16 detects a change in the magnetic field direction of the magnet 15, and a PWM signal is detected as a detection signal by a microcomputer (hereinafter referred to as CPU). Is output to a control circuit (rotation angle calculation means and rotation angle correction means) 13 formed by the electronic components, and is converted into a rotation angle signal of the main gear 1.

  In FIG. 3, the steering shaft 106 includes an input shaft 5, an output shaft 6, and a torsion bar 7 provided between the input shaft 5 and the output shaft 6. The main gear 1 is a rotating body having a multi-rotatable gear fitted and connected to the magnetic yoke 115 of the torque sensor 112. The torsion bar 7 is disposed on a concentric axis between the input shaft 5 and the output shaft 6. The detection gear 2 is a rotating body provided so as to be engaged with the gear of the main gear 1, and a detection circuit 14 (see FIG. 2A) is disposed at the center thereof. A control circuit 13 (see FIG. 2B) is disposed on a circuit board 12 provided in the upper space of the detection gear 2.

  The gear of the main gear 1 and the gear of the detection gear 2 are connected, and when the main gear 1 rotates, the detection gear 2 rotates at a speed according to the ratio of the number of teeth of each gear.

Next, an embodiment of a method for detecting the rotation angle of the main gear 1 of the present invention will be specifically described based on the drawings.
First, the processing procedure of backlash correction value acquisition and backlash correction calculation by the control circuit 13 of the present embodiment will be described.
In the present embodiment, the control circuit 13 executes each process of Step 401 to Step 412 shown in the flowchart of FIG. 4 and Step 501 to Step 506 shown in the flowchart of FIG.

  As shown in FIG. 4, the CPU (not shown) in the control circuit 13 acquires the steering torque τ detected by the torque sensor 112, that is, the torque value of the detected torque. Further, the rotation angle (detected steering angle) of the main gear 1 is calculated based on the output signal from the magnetic angle sensor 16 that detects the rotation angle of the detection gear 2 (step S401).

  Subsequently, the CPU calculates a detected torque differential value from the detected torque, and calculates a steering angular velocity from the detected steering angle by differential calculation (step S402).

  Next, it is determined whether or not the detected torque differential value is greater than or equal to a predetermined value (step S403), and whether or not the steering angular velocity is greater than or equal to a predetermined value (step S404). When the detected torque differential value is equal to or greater than a predetermined value (step S403: YES) and the steering angular velocity is equal to or greater than a predetermined value (step S404: YES), the steering wheel 107 is steered without backlash, that is, backlash (hereinafter referred to as “backlash”). This is referred to as steering wheel steering), and the backlash correction value acquisition and backlash correction processing are executed. If the detected torque differential value is smaller than the predetermined value (step S403: NO) or the steering angular velocity is smaller than the predetermined value (step S404: NO), the process is terminated and the flow is exited.

  First, the CPU determines whether the steering wheel is in the right direction or the steering direction in the left direction depending on whether the detected torque differential value is positive or negative (step S405). In the case of rightward steering (for example, the torque differential value is negative, step S405: YES), the torsion angle of the torsion bar 7 is calculated from the detected torque when the detected torque exceeds a predetermined value and the spring constant of the torsion bar 7. The difference between the twist angle and the detected rudder angle is one side, that is, backlash during rightward steering (step S406, see FIG. 6B described later). Subsequently, a backlash acquisition completion flag for rightward steering is set (step S407), and the process proceeds to step S410.

  Further, in the case of leftward steering (for example, the torque differential value is positive, step S405: NO), the torsion angle of the torsion bar 7 is calculated from the detected torque when the detected torque exceeds a predetermined value and the spring constant of the torsion bar 7. To do. The difference between the twist angle and the detected rudder angle is one side, that is, backlash at the time of leftward steering (step S408, see FIG. 6A described later). Subsequently, a backlash acquisition completion flag during leftward steering is set (step S409), and the process proceeds to step S410.

Here, the CPU determines whether or not the backlash acquisition at the time of left and right steering is completed (step S410). When the backlash acquisition at the time of left and right steering is completed (step S410: YES), the CPU calculates the total backlash correction value. Calculation is performed (step S411).
Backlash correction value = ± ((backlash during left steering-backlash during right steering) / 2)
Also, if the backlash acquisition at the time of left and right steering is not completed, the process is terminated and the flow is exited.

  Subsequently, the CPU sets a backlash correction value acquisition completion flag, and ends the arithmetic processing (step S412).

Next, the backlash correction calculation process will be described.
As shown in FIG. 5, the CPU in the control circuit 13 acquires the steering angle of the steering shaft 107, that is, the rotation angle (detected steering angle) of the main gear 1 (step S501), and then calculates the steering angular velocity (step S502). ).

  Next, the CPU determines whether or not the steering wheel is being steered (step S503). If the steering is in a stopped state (step S503: NO), the backlash correction value is set to 0, the process is terminated, and the flow is exited. If the steering wheel is being steered (step S503: YES), the CPU determines whether the steering torque is in the right direction or the steering direction in the left direction depending on whether the detected torque differential value is positive or negative (step S504). In the case of rightward steering (for example, the torque differential value is a negative value, step S504: YES), the backlash correction value acquired by the backlash correction value acquisition process (see FIG. 4) for the detected steering angle according to the positive / negative value of the steering angular velocity. Is added and subtracted to perform backlash correction during rightward steering (step S505, addition if the sign of the steering angular velocity is positive, subtraction if negative).

  Further, in the case of determination of leftward steering (for example, the torque differential value is a positive value, step S504: NO), similarly, the backlash correction value (see FIG. 4) is added to or subtracted from the detected steering angle in accordance with the positive / negative value of the steering angular velocity. Then, backlash correction at the time of leftward steering is executed (step S506, addition is performed when the sign of the steering angular velocity is positive, and subtraction is performed when it is negative).

FIG. 6 shows an embodiment of the backlash correction value acquisition and backlash correction calculation processing in the steering wheel state described above.
FIG. 6 is a diagram showing the detected torque and detected angle of the main gear 1, the torque differential value and the steering angular velocity obtained by the calculation of the CPU, the horizontal axis of FIG. 6 shows time, and the vertical axis shows the torque and angle respectively. , Torque differential value, and angular velocity. The detected torque represents the steering torque detected by the torque sensor 112, and the backlash correction value is calculated from the difference from the torsion angle of the torsion bar 7 using the spring constant of the torsion bar 7. The detected steering angle represents a steering angle including an error due to backlash, and a steering angular velocity for determining whether or not there is backlash between the main gear 1 and the detection gear 2 at the time of steering is calculated from the detected angle. Further, the steering state and steering direction of the steering wheel 107 are detected from the detected torque differential value calculated from the detected torque. The post-correction steering angle represents the steering angle after the backlash correction is actually executed and the backlash correction value is added to or subtracted from the detected steering angle. Here, the steering angle when the steering of the steering wheel is stopped (detected angular velocity = 0) is a value smaller than the ideal steering steering angle without backlash (not shown) by the backlash correction value. Note that the steering angular velocity and torque differential value are set to positive values during leftward steering, and the steering angular velocity and torque differential value are set to negative values during rightward steering.

In this embodiment, specifically, when the detected torque differential value is 50 [Nm / s] or more and the steering angular velocity is 50 [deg / s] or more, the detected rudder when the detected torque exceeds 5 [Nm]. The corner is stored (FIG. 6A). In FIG. 6, the detected torque value immediately after the detected torque exceeds 5 [Nm] is 5.103 [Nm], and the detected steering angle is 1.7 [deg]. The backlash is calculated using these values and the spring constant of the torsion bar 7. (Spring constant of torsion bar 7: 1.89 [Nm / deg])
Backlash during left steering = 5.103 [Nm] /1.89 [Nm / deg] −1.7 [deg] = 1 [deg]

Subsequently, the backlash when the steering wheel 107 is steered in the right direction is similarly calculated (FIG. 6B).
Backlash when steering rightward = -1 [deg]
As a result, the backlash becomes 2 [deg] (= 1 [deg] − (− 1 [deg])), and ± 1 [deg] (= ± 2 [deg] / 2) is calculated as the backlash correction value. The
The actual correction is executed by adding or subtracting the backlash correction value 1 [deg] to the detected steering angle in accordance with the sign of the steering angular velocity.

Next, operations and effects of the torque sensor 112 and the rotation angle detection device 111 applied to the electric power steering device 100 of the present embodiment configured as described above will be described.
As described above, the backlash correction value is obtained from the difference between the detected torque detected by the torque sensor 112 and the torsion angle of the torsion bar 7 determined from the spring constant of the torsion bar 7 and the detected steering angle detected from the detection gear 2. The detection error of the rotation angle due to the backlash between the main gear 1 and the detection gear 2 is corrected by adding / subtracting the detected rudder angle and the backlash correction value. According to the embodiment of the present invention, the torque sensor 112 and the rotation angle detection device 111 are used, and the backlash correction value can be acquired even if the vehicle is running and the steering wheel is being steered. Further, even if gear wear or temperature characteristics change, real-time backlash correction can be realized, so that the output of the corrected rotation angle of the steering shaft 106 is always constant and a high-precision rotation angle can be obtained. . As in this embodiment, particularly when steering is performed such that the steering direction is repeatedly switched by the steering wheel 107 of the vehicle, the rotation angle of the steering wheel 107 can be detected with high accuracy.

  Furthermore, since the rotation angle detection device of the present invention can detect the rotation angle with a simple configuration and can reduce the mounting space and cost, it can be applied to rotation angle detection used in vehicle power steering and the like. Useful for.

In addition, you may change the said embodiment as follows.
In the embodiment of the present invention, the rotation angle calculation unit and the rotation angle correction unit are provided in the rotation angle detection device.
Further, according to the present embodiment, the rotation angle detection device is mounted on the torque sensor (add-on). However, the rotation angle detection device and the torque sensor can be integrated into a single structure, and the size can be reduced.
-In embodiment of this invention, although comprised with one detection gear with respect to one main gear, you may be comprised with two or more detection gears meshing with a main gear.
Furthermore, the present invention can also be implemented as a configuration in which the first detection gear is engaged with the main gear and the second detection gear is engaged with the first detection gear.
-Although this invention demonstrated the example used for the electric power steering apparatus, it is not limited to embodiment mentioned above, Various application is possible in the structure which arrange | positions a torque sensor and a rotation angle detection apparatus on the same axis | shaft. Further, the present invention can be applied not only to the above-described column assist type electric power steering apparatus but also to a pinion assist type or rack assist type electric power steering apparatus.

1: main gear, 2: detection gear, 5: input shaft, 6: output shaft, 7: torsion bar,
12: Circuit board, 13: Control circuit (rotation angle calculation means and rotation angle correction means),
14: detection circuit (rotation detection means), 15: magnet, 16: magnetic angle sensor,
100: Electric power steering device, 105: Intermediate shaft,
106: Steering shaft, 107: Steering wheel (handle),
108: deceleration mechanism, 109: motor, 110: vehicle, 111: rotation angle detection device,
112: Torque sensor (steering torque detection means), 113: Vehicle speed sensor,
114: Steering control device (ECU), 115: Torque sensor magnetic yoke,
θ: Steering angle, τ: Steering torque, V: Vehicle speed

Claims (2)

Torque detecting means for detecting rotational torque acting between the input shaft and the output shaft of the rotating body connected to both ends of the torsion bar;
A main gear that rotates in conjunction with the rotating body;
A detection gear that rotates in conjunction with the main gear;
In a rotation angle detection device comprising rotation detection means for detecting rotation of the detection gear as a detection signal,
While calculating the rotation angle of the rotating body based on the detection signal output from the rotation detection means,
From the difference between the torsion angle of the torsion bar calculated based on the rotational torque detected by the torque detection means and the rotational angle of the rotating body when the rotational angular velocity of the rotating body is a predetermined value or more, A rotation angle calculating means for calculating a backlash correction value for correcting an error caused by backlash between the main gear and the detection gear;
And a rotation angle correction unit that corrects the rotation angle of the rotating body based on the backlash correction value.   An electric power steering device comprising the rotation angle detection device according to claim 1.

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