JP2007071784A - Torque sensing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a torque sensing device capable of effectively using detection results in a normal state of a sensor for abnormality determination and also sensing a surrounding temperature together. <P>SOLUTION: A twist angle of an axis is sensed by a first and a second sensor 51, 52 under the same condition, which have different settings of correction constants for correcting variations of output characteristics by temperature. In an arithmetic operation circuit 50 to which the outputs are provided, a steering torque of a rotating torque is determined by the output of the first sensor 51; abnormality is determined by the output comparison of the first and the second sensor 51, 52; further a surrounding temperature is calculated to output a temperature sensing value, based on the outputs of the sensors 51, 52. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a torque detection device configured to detect a rotational torque applied to a shaft based on a twist angle of the shaft, and more particularly, to have a function as a temperature sensor for detecting an ambient temperature. The present invention relates to a torque detection device.

  2. Description of the Related Art In recent years, an electric power steering apparatus that includes an electric motor that can be easily controlled as an actuator for assisting steering has become widespread as a power steering apparatus for an automobile. In this electric power steering device, a torque detection device is arranged in the middle of a steering shaft that transmits an operation of a steering member such as a steering wheel to a steering mechanism, and the torque is applied to the steering shaft according to the operation of the steering member. Torque (steering torque) is detected, and the rotational force of a steering assist motor that is driven and controlled based on the detection result is applied to the steering mechanism to assist steering.

  Most of the torque detection devices used in this way divide a steering shaft to be detected into a first shaft and a second shaft connected by a small-diameter torsion bar as a torsion spring, and rotate the steering member. When a steering torque is applied to the steering shaft, the steering torque is detected using a twist angle generated between the first and second shafts as the torsion bar is twisted.

  The detection of the torsion angle between the first and second shafts has been realized by various means conventionally. One of them is a cylindrical magnet that rotates integrally with the first shaft, and one that rotates integrally with the second shaft. There is a torque detection device that includes a yoke ring and is configured to detect a change in a magnetic circuit between the cylindrical magnet and the yoke ring by a Hall sensor (see, for example, Patent Document 1).

  The Hall sensor is configured by combining a Hall element as a magnetic detection element and an output correction IC. The IC for output correction performs the function of correcting the change in characteristics of the Hall element due to the influence of the ambient temperature. By setting an appropriate temperature constant in advance according to the combined Hall element, the influence of the ambient temperature is achieved. It is used to correct the degree of change in output due to, and to suppress a decrease in detection accuracy due to the influence of ambient temperature.

On the other hand, the torque detection device used in the electric power steering device is an important detection device that determines the magnitude of the generated force of the steering assist motor, and that inappropriate control based on erroneous detection results is performed. In order to prevent this, an abnormality occurs when two sensors (main sensor and sub sensor) having the same characteristics are arranged under the same conditions and the detection results of the torsion angles by these sensors are different. In these cases, for example, the drive control of the steering assist motor is stopped and the fail safe operation is performed such that the steering assist is not performed (see, for example, Patent Document 2).
JP2003-149062 Japanese Patent No. 3094483

  The fail-safe operation as described above is also implemented in the torque detection device using the Hall sensor described above as a torsion angle detection means. However, one Hall sensor as the auxiliary sensor is used as a main sensor for assisting steering. It is used only for fail determination of the other hall sensor used for driving control of the motor, and it is desired to make effective use of the output of this sub sensor other than at the time of failure.

  Such effective use is also eagerly desired both in a torque detection device using a sensor other than a Hall sensor for detecting a torsion angle and also in a torque detection device applied to other than an electric power steering device.

  The present invention has been made in view of such circumstances, and in a configuration including a sensor configured to be able to adjust a change in characteristics due to temperature, such as a hall sensor, as a twist angle detection unit, a sensor for fail determination is provided. An object of the present invention is to provide a torque detection device that can detect the ambient temperature by using the detection result at the normal time.

  The torque detection device according to the first aspect of the present invention detects the torsion angle of the shaft under the same condition by two sensors capable of setting a correction constant for correcting a change in output characteristics due to temperature. In the torque detection device that obtains rotational torque applied to the shaft by output and determines the failure of both sensors by comparing the outputs of both sensors, different correction constants are set for the two sensors, and based on the outputs of both sensors And a temperature calculating means for calculating the ambient temperature.

  In the torque detection device according to the second aspect of the present invention, the two sensors are configured such that the gains of the respective outputs are set to opposite polarities, and the temperature calculation means is configured to perform the above-described operation based on the sum of the outputs of both sensors. The configuration is characterized in that the ambient temperature is calculated.

  In the torque detection device according to the first aspect of the present invention, when the twist angle of the target shaft is detected under the same condition by two sensors having different correction constants, they are set to the outputs of both sensors, respectively. Since the difference between the corrected constants is used and the ambient temperature of the torque detector is calculated based on the outputs of both sensors, the sensor provided for fail determination is effectively used. It becomes possible.

  In the torque detector according to the second invention, since the two sensors have gain characteristics of opposite polarities, more specifically, based on the sum of the outputs of both sensors, more specifically, The present invention has an excellent effect, such as being able to detect easily and with high accuracy using a deviation amount from zero.

  Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof. FIG. 1 is a schematic diagram showing a configuration of an electric power steering apparatus provided with a torque detection device according to the present invention. The electric power steering apparatus is installed in a rack housing 10 that extends in the left-right direction of a vehicle body (not shown). A rack-and-pinion type steering mechanism including a rack shaft 1 supported so as to be movable in the axial direction and a pinion shaft 2 supported rotatably inside a pinion housing 20 that intersects the middle of the rack housing 10 is provided. ing.

  Both ends of the rack shaft 1 projecting outward from both sides of the rack housing 10 are connected to left and right front wheels 12 and 12 as steering wheels via separate tie rods 11 and 11, respectively, and from one side of the pinion housing 20 to the outside. The upper end of the pinion shaft 2 protruding in the direction is connected to a steering wheel 30 as a steering member via the steering shaft 3. A pinion (not shown) is formed at the lower part of the pinion shaft 2 extending into the pinion housing 20, and the pinion is formed on the outer surface of the rack shaft 1 at an appropriate length at the intersection with the rack housing 10. Meshed with the rack teeth.

  The steering shaft 3 is rotatably supported inside a cylindrical column housing 31 and is fixed via the column housing 31 to the interior of a vehicle compartment (not shown) while maintaining an inclined posture with the front facing down. . A pinion shaft 2 is connected to a protruding end of the steering shaft 3 below the column housing 31, and a steering wheel 30 is fixed to the protruding end.

  With the above configuration, when the steering wheel 30 is rotated for steering, this rotation is transmitted to the pinion shaft 2 via the steering shaft 3, and the rotation of the pinion shaft 2 is engaged with the pinion and the rack teeth. In this part, the rack shaft 1 is converted into a movement in the axial direction. By this movement, the left and right front wheels 12, 12 are pushed and pulled through the respective tie rods 11, 11, and steering is performed.

  A steering assisting motor 4 is mounted in the middle of the column housing 31 that supports the steering shaft 3, and the steering shaft 3 is moved to the steering shaft 3 by rotating the steering wheel 30 inside the column housing 31 above the motor 4. A torque detection device 5 according to the present invention is configured to detect the applied steering torque.

  The steering assist motor 4 is attached to the outside of the column housing 31 with its axis substantially orthogonal, and for example, a worm fixed to the output end of the motor 4 extending inside the column housing 31 is attached to the steering shaft 3. The worm wheel meshes with the fitted worm wheel, and the transmission of the rotation of the motor 4 is decelerated by the worm and the worm wheel and transmitted to the steering shaft 3. According to this configuration, the rotation of the steering assist motor 4 is transmitted to the steering shaft 3 at a reduced speed, and a rotational force is applied to the pinion shaft 2 connected to the lower end of the steering shaft 3. Accordingly, the steering performed as described above is assisted.

  The torque detection device 5 divides the steering shaft 3 to be detected into two upper and lower axes, and these two shafts are connected coaxially by a torsion bar having a known torsion characteristic. It has a known configuration for detecting a twist angle generated between the two axes with a twist of.

  The steering assist motor 4 is driven in accordance with a control command given from the assist control unit 6 via a drive circuit (not shown). The assist control unit 6 is provided with the detected value of the steering torque by the torque detecting device 5 and the detected value of the driving current of the motor 4 from the motor current sensor 40 attached to the steering assisting motor 4. ing.

  The assist control unit 6 includes a CPU, a ROM, and a RAM, and is configured as an ECU that performs assist control by the operation of the CPU according to a control program stored in the ROM, and is based on the steering torque detected by the torque detection device 5. Then, a control command is issued to the steering assist motor 4, and a known assist control operation is performed to increase / decrease the drive current of the motor 4 using the detected value of the drive current by the motor current sensor 40 as a feedback signal.

  FIG. 2 is a block diagram illustrating a configuration example of a main part of the torque detection device 5. For example, as disclosed in Patent Document 1, the torque detection device 5 detects a change in a magnetic circuit between a cylindrical magnet that rotates integrally with one of the two shafts and a yoke ring that rotates integrally with the other. First and second sensors 51 and 52, and an arithmetic processing circuit 50 for inputting the output signals of these sensors 51 and 52 to calculate torque and for determining whether or not both sensors 51 and 52 are abnormal. I have.

  The first and second sensors 51 and 52 are hall sensors each including a hall element as a magnetic detection element and an IC for correcting the output of the hall element. The first and second sensors 51 and 52 Are set so that each gain has the same gain value but opposite polarity.

  FIG. 3 is a diagram showing the relationship between the outputs of the first and second sensors 51 and 52 and the steering torque. With the above gain setting, the first sensor 51 has an output characteristic that changes at a predetermined change rate (gain value) so as to be positive with respect to the steering torque in one direction and negative with respect to the steering torque in the other direction. The second sensor 52 has an output characteristic that changes at the same rate of change as the first sensor 51 so as to be negative with respect to the steering torque in one direction and positive with respect to the steering torque in the other direction. Indicates.

  In the arithmetic processing circuit 50 to which the output signals of the first and second sensors 51 and 52 are provided, the output of one (for example, the first sensor 51) is used for calculation of the steering torque, and the other (for example, for example, The output of the second sensor 52) is used for fail determination of the first sensor 51 (or the second sensor 52).

  The steering torque is obtained as indicated by a broken line arrow in FIG. 3 by applying the output of the first sensor 51 sequentially applied to, for example, a calculation table corresponding to FIG. Further, the fail judgment of the first and second sensors 51 and 52 is performed when the outputs of the first and second sensors 51 and 52 set to gains of opposite polarities are correct. For example, the sum of the outputs of the first and second sensors 51 and 52 given sequentially is obtained, and this sum is obtained from a predetermined dead band centered on zero. If it is off, it is determined that an abnormality has occurred.

  The result of such a fail determination is given to the assist control unit 6. In response to the fail determination, the assist control unit 6 performs a fail-safe operation such as stopping the assist control operation and generating an alarm, for example. carry out. Note that the fail determination according to the above procedure may be performed in the arithmetic processing circuit 50, and only the determination result may be given to the assist control unit 6 as shown in FIG. , 52 may be directly applied to the assist control unit 6 so that the fail control is performed in the assist control unit 6.

  Furthermore, in the torque detection device 5 according to the present invention, the ambient temperature of the torque detection device 5 can be detected using the outputs of the first and second sensors 51 and 52. This temperature detection is performed as follows using output correction ICs provided in the first and second sensors 51 and 52 configured as Hall sensors.

  The output correction ICs provided in the first and second sensors 51 and 52 correct the temperature dependence of the output held by the Hall element so that substantially the same output characteristics can be obtained regardless of the temperature. And is used to achieve the purpose by externally setting correction constants in advance.

  In the present invention, different correction constants are set in the output correction ICs of the first and second sensors 51 and 52, respectively. That is, the correct correction constant is set for the first sensor 51 used for calculating the steering torque so as to eliminate the temperature dependence of the output characteristic, which is the original purpose, whereas the correct correction constant is set for the second sensor 52. Set a correction constant that deviates from the correction constant.

  FIG. 4 is a diagram showing output characteristics of the first and second sensors 51 and 52 under various temperatures. A solid line in the figure shows an output characteristic under a standard temperature, and a broken line in the figure The output characteristics under a temperature lower than the standard temperature are shown, and the alternate long and short dash line shows the output characteristics under a temperature higher than the standard temperature. As shown in this figure, the output characteristic of the first sensor 51 with the correct correction constant set shows substantially the same output characteristic as that under the standard temperature regardless of the ambient temperature, but it is erroneously corrected. The output characteristics of the second sensor 52 in which the constants are set greatly change according to the level of the ambient temperature.

  Therefore, the sum of the outputs of the first and second sensors 51 and 52 is biased from the zero point to the output side of the second sensor 52 at a high temperature as indicated by A in FIG. α increases as the ambient temperature increases. Conversely, the sum of the outputs at low temperatures is biased toward the first sensor 51, and the amount of bias increases with a decrease in temperature.

  As described above, when the first and second sensors 51 and 52 having different correction constants are used, the sum of the outputs of both the sensors 51 and 52 can be set so that the ambient temperature can be increased or decreased. It will be included. In the arithmetic processing unit 50, the sum of the outputs of the first and second sensors 51 and 52 given sequentially is obtained, the ambient temperature is calculated using this sum, the result is output as a temperature detection value, and assist control is performed. Part 6 is given. As in the case of the fail determination, the outputs of the first and second sensors 51 and 52 can be directly given to the assist control unit 6 to calculate the temperature in the above-described procedure in the assist control unit 6. it can.

  The assist control unit 6 recognizes the temperature detection value given in this way as the ambient temperature of the torque detection device 5 and, for example, uses this temperature detection value as an overload of the steering assisting motor 4 and from the motor 4 to the steering shaft. 3 is used to determine whether or not there is an abnormality around the torque detection device 5 such as a transmission system failure to No. 3, and when it is determined that there is an abnormality, a predetermined fail-safe operation such as suspension of the assist control operation is performed.

  Such temperature detection can be performed by a simple calculation that uses the outputs of the first and second sensors 51 and 52 that are originally required for the torque detection device 5 and calculates the sum of these outputs. A peripheral abnormality can be determined without using a sensor, and a fail-safe operation can be performed for reasons other than the sensor abnormality.

  Further, such temperature detection can be performed without affecting the abnormality determination performed as described above by limiting the maximum value of the deviation amount α that occurs at an assumed temperature. Specifically, the maximum value of the deviation amount α may be set within the dead band set as described above in the abnormality determination, and this is realized by appropriately setting the correction constant.

  In the above embodiment, the application example to the torque detection device provided for detecting the steering torque in the electric power steering device has been described. However, the torque detection device according to the present invention is a rotation applied to the rotation shaft. Needless to say, the present invention can be applied to all applications for detecting torque. In the above embodiment, the case where Hall sensors are used as the first and second sensors 51 and 52 has been described, but any sensor other than the Hall sensor can be used as long as it has a function of correcting a change in output characteristics due to temperature. These sensors may be provided.

It is a schematic diagram which shows the structure of an electric power steering apparatus provided with the torque detection apparatus which concerns on this invention. It is a block diagram which shows the structural example of the principal part of a torque detection apparatus. It is a figure which shows the relationship between the output of each 1st, 2nd sensor, and steering torque. It is a figure which shows the output characteristic of the 1st, 2nd sensor under various temperature.

Explanation of symbols

3 Steering shaft (shaft)
5 Torque detection device
50 Arithmetic processing circuit (temperature calculation means)
51 First sensor
52 Second sensor unit (control means)

Claims (2)

Two sensors capable of setting correction constants that correct changes in output characteristics due to temperature detect the torsion angle of the shaft under the same conditions, and determine the rotational torque applied to the shaft by the output of one sensor. In the torque detection device that performs fail determination of both sensors by comparing the outputs of the sensors,
A torque detection apparatus comprising temperature calculating means for setting different correction constants for the two sensors and calculating an ambient temperature based on outputs of both sensors.   2. The configuration according to claim 1, wherein each of the two sensors has an output gain set to a reverse polarity, and the temperature calculation unit calculates the ambient temperature based on a sum of outputs of both sensors. Torque detection device.

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