JP5045585B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering device (hereinafter referred to as EPS) that assists steering of a steered wheel by the output of an electric motor.

  Conventionally, energization of an electric motor in EPS is controlled mainly based on torque applied to a steering wheel by an occupant. The torque is detected by, for example, a torque sensor incorporated in the steering shaft and output to an electronic control unit (ECU), and the ECU executes energization control of the electric motor in accordance with the detected torque. .

  In recent years, mounting of EPS has become common not only in light cars but also in ordinary passenger cars, and the number of vehicles that assist steering of steering wheels by EPS has increased remarkably. For this reason, it is necessary to take some measures in order to avoid the sudden change of the steering feeling of the occupant due to the stop of the EPS assist when the EPS fails, and various control means are used. It is considered (for example, refer to Patent Document 1).

  That is, according to the EPS of Patent Document 1, even if a failure occurs in the EPS, the assist by the EPS is not stopped completely, but the operation control of the electric motor is continued according to the control method at the time of the EPS failure, and the occupant This avoids sudden fluctuations in the steering feeling.

  By the way, the control means of Patent Document 1 is mainly intended to avoid abrupt fluctuations in steering feeling by continuing the assist, so the assist force is limited and weak, and is considered a measure as an emergency measure. . For this reason, according to the control means of Patent Document 1, it is necessary to gradually decrease the assist force and finally stop the assist.

Then, after the engine is stopped, even when the engine is started again, the assist force is weak or the state where the assist is stopped is maintained, and the occupant will drive while feeling uncomfortable with steering.
Therefore, as a further improvement measure in the future, there is a demand for a control means that can avoid the final assist stop without weakening the assist force even in the event of an EPS failure.
JP 2007-283891 A

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a control means capable of avoiding a final assist stop without weakening the assist force even when an EPS failure occurs. It is in.

[Means of Claim 1]
The EPS according to claim 1 is incorporated in an electric motor that generates an output that assists steering of a steered wheel, a shaft that forms a transmission path of torque applied to the steered wheel between the steered wheel and the steered wheel, and the shaft. A torque detecting means for generating a plurality of electrical outputs for detecting torque according to the relative rotational displacement between the steered wheel shaft and the steered wheel shaft; and an electric motor based on the plurality of electrical outputs. And a control means for controlling the energization.

  The torque detection means includes magnetic flux generation means for generating a magnetic flux that changes according to the relative rotational displacement amount, and a plurality of output generation means for generating an electrical output according to the magnetic flux generated by the magnetic flux generation means. Then, when the engine is started, the control means energizes the electric motor to generate a relative rotational displacement amount and generates a plurality of electrical outputs from the torque detecting means, thereby causing a malfunctioning output from the plurality of output generating means. It has a fault device specifying means for specifying the generating means.

  Further, the fault device specifying means temporarily changes a current value to be supplied to the electric motor so that the electric output temporarily changes over a predetermined threshold value, and the electric output is a temporary value of the current value. By determining whether or not the change has occurred across the threshold due to a change, a faulty output generation means is specified from among the plurality of output generation means.

  Thereby, the faulty device specifying means can specify the faulty output generating means (hereinafter referred to as a faulty device) with high accuracy. That is, if the current value to be supplied to the electric motor is temporarily changed, the relative rotational displacement amount is also temporarily changed, and the magnetic flux generated by the magnetic flux generating means is also changed. For this reason, if a failure has not occurred in the output generation means that is the specific target, the electrical output also temporarily changes across the threshold value.

  Therefore, by temporarily changing the value of the current to be supplied to the electric motor, it is determined whether or not the electrical output of the output generation means that is the specific target has temporarily changed across the threshold. It is possible to reliably determine whether or not the output generation means that is the specific target is a fault device. If the use of the electrical output obtained from the fault device is stopped and the control is continued based on the electrical output obtained from other non-failed output generating means, the assist force can be reduced without weakening the assist force. The assist by EPS can be continued without stopping.

  Moreover, in the case of an EPS failure, it is rarely considered that a mechanical structural part will fail, and it is considered that some sort of malfunction occurs only in the signal output system of the torque detection means. Therefore, when the torque detecting means is provided with a plurality of output generating means, by constructing the control means as described above, it is possible to cope with the EPS failure almost completely without weakening the assist force. In addition, it is possible to continue assist with EPS without stopping the assist.

[Means of claim 2]
According to the EPS of the second aspect, the fault device specifying means repeats the temporary fluctuation of the current value a plurality of times.
As a result, the temporary fluctuation of the current value and the temporary change of the electrical output are stably repeated. For this reason, since the reliability with respect to the determination whether the electrical output has changed across the threshold value can be enhanced, the reliability with respect to the faulty device identification can be enhanced as a result.

[Means of claim 3]
According to the EPS of the third aspect, the faulty unit specifying means stores two different threshold values, the larger threshold value of the two threshold values is stored as the larger threshold value, and the smaller threshold value is decreased. It is stored as a side threshold value. In addition, the fault device identification means increases the current value so that the electrical output temporarily exceeds the upper threshold temporarily exceeding the large threshold and the electrical output temporarily decreases below the small threshold alternately. It is temporarily changed alternately to the side and the small side.

Then, the faulty unit specifying means specifies the faulty unit from among the plurality of output generating units by determining whether or not both overshooting and undercutting have occurred in the electrical output.
Thereby, for example, even when the electrical output changes according to the fluctuation of the current value but is shifted to the large side or the small side, it can be reliably identified as a faulty device. For this reason, the reliability with respect to faulty device identification can be improved.

[Means of claim 4]
According to the EPS of the fourth aspect, the fault device specifying means temporarily changes the current value by making the current value follow a sine function or a cosine function.
As a result, the electrical output is stabilized at the maximum or minimum when it temporarily changes. For this reason, the reliability with respect to faulty device identification can be improved.

[Means of claim 5]
According to the EPS of the fifth aspect, the control means includes a failure determination means for determining whether or not there is a fault device in the plurality of output generation means, and a fault device in the plurality of output generation means. A failure history storage means for storing that there is a faulty device among the plurality of output generation means. The faulty device specifying means temporarily changes the current value when the fault history storage means stores that there is a faulty device among the plurality of output generating means.
As a result, the control means executes the faulty unit specifying process only when the presence of the faulty unit is confirmed. For this reason, a faulty device can be identified efficiently.

  The EPS of the best mode 1 is incorporated in an electric motor that generates an output that assists steering of a steered wheel, a shaft that forms a transmission path of torque applied to the steered wheel between the steered wheel and the steered wheel, Torque detection means for generating a plurality of electrical outputs for detecting torque in accordance with the relative rotational displacement between the steered wheel side shaft and the steered wheel side shaft, and to the electric motor based on the plurality of electrical outputs Control means for controlling energization.

  The torque detection means includes magnetic flux generation means for generating a magnetic flux that changes according to the relative rotational displacement amount, and a plurality of output generation means for generating an electrical output according to the magnetic flux generated by the magnetic flux generation means. Then, when the engine is started, the control means energizes the electric motor to generate a relative rotational displacement amount and generates a plurality of electrical outputs from the torque detecting means, thereby causing a malfunctioning output from the plurality of output generating means. It has a fault device specifying means for specifying the generating means.

  Further, the fault device specifying means temporarily changes a current value to be supplied to the electric motor so that the electric output temporarily changes over a predetermined threshold value, and the electric output is a temporary value of the current value. By determining whether or not the change has occurred across the threshold due to a change, a faulty device is specified from a plurality of output generating means.

Further, the faulty device specifying means repeats the temporary fluctuation of the current value a plurality of times.
Further, the faulty unit specifying means stores two threshold values, and stores a larger threshold value among the two threshold values as a larger threshold value, and stores a smaller threshold value as a smaller threshold value. In addition, the fault device identification means increases the current value so that the electrical output temporarily exceeds the upper threshold temporarily exceeding the large threshold and the electrical output temporarily decreases below the small threshold alternately. It is temporarily changed alternately to the side and the small side.

Then, the faulty unit specifying means specifies the faulty unit from among the plurality of output generating units by determining whether or not both overshooting and undercutting have occurred in the electrical output.
Further, the fault device specifying means temporarily varies the current value by making the current value follow a sine function or a cosine function.

  The control means includes a failure determination means for determining whether or not there is a faulty device in the plurality of output generation means, and a plurality of outputs when it is determined that there is a faulty device in the plurality of output generation means. Fault history storage means for storing the presence of a faulty device in the output generation means. The faulty device specifying means temporarily changes the current value when the fault history storage means stores that there is a faulty device among the plurality of output generating means.

[Configuration of Example]
The EPS 1 of the embodiment will be described with reference to the drawings.
As shown in FIG. 1, the EPS 1 assists steering of the steering wheel 3 by the output of the electric motor 2, and is controlled mainly based on the torque applied to the steering wheel 3 by an occupant. The torque is detected by, for example, a torque sensor 5 incorporated in a steering shaft (hereinafter referred to as the shaft 4) and output to the ECU 6. The ECU 6 applies to the electric motor 2 in accordance with the detected torque or the like. Energization control is being executed.

  That is, the EPS 1 includes an electric motor 2 that generates an output for assisting steering of the steered wheel 3, a shaft 4 that forms a transmission path of torque applied to the steered wheel 3, and a shaft 4 that is incorporated in the shaft 4 and that is on the steered wheel 3 side. A torque sensor 5 that generates an electrical output for detecting torque according to a relative rotational displacement amount (hereinafter simply referred to as a relative rotational displacement amount) with the shaft 4 on the steered wheel 8 side, and obtained from the torque sensor 5 ECU6 which controls energization to electric motor 2 based on an electrical output to be provided.

  In the following description, the shaft 4 closer to the steered wheel 3 than the torque sensor 5 is called an input shaft 9, and the shaft 4 closer to the steered wheel 8 than the torque sensor 5 is called an output shaft 10.

The torque applied to the steered wheels 3 is transmitted from the shaft 4 to the steered wheels 8 via the rack and pinion mechanism 11 and the like, and the steered wheels 8 are steered. Further, the output of the electric motor 2 is transmitted to, for example, the rack and pinion mechanism 11, and the steering of the steered wheels 8, that is, the steering by the steered wheels 3 is assisted.
The electric motor 2 may employ various types of motors such as a direct current motor, a brushless DC motor, a switched reluctance motor, and an embedded magnet type synchronous motor.

  As shown in FIG. 2 and FIG. 3, the torque sensor 5 has a magnetic flux generating means 13 that generates a magnetic flux that changes according to the relative rotational displacement amount, and an electrical output according to the magnetic flux generated by the magnetic flux generating means 13. Two output generating means 15 and 16 are provided.

  The magnetic flux generating means 13 includes, for example, a magnet 17 that rotates integrally with the input shaft 9, a comb-shaped yoke 19 that rotates integrally with the output shaft 10 and collects the magnetic flux generated from the magnet 17, and both ends are respectively The pin 20 is configured by a torsion bar 21 or the like that is locked to the input and output shafts 9 and 10 and is twisted in accordance with the steering of the steering wheel 3.

  The output generators 15 and 16 respectively provide a Hall element that is sensitive to the magnetic flux collected by the ring 22 via the yoke 19, a magnetic flux density of the magnetic flux that is sensitive to the Hall element, and an electrical output corresponding to the applied voltage. The Hall IC is composed of an output circuit that generates the output (hereinafter, the output generation means 15 and 16 are referred to as Hall ICs 15 and 16).

  Here, the Hall ICs 15 and 16 have output terminals 24 and 25 for outputting electrical outputs to the ECU 6, respectively, as shown in FIG. The Hall ICs 15 and 16 have a common input terminal 26 for receiving an applied voltage from the power supply 14 and a common GND terminal 27 for grounding. Further, a noise removing capacitor 28 is disposed between the wirings of the Hall ICs 15 and 16 and the respective terminals, and wirings are assembled so as to mainly absorb electromagnetic waves as disturbances.

  In place of the common input terminal 26 for receiving the applied voltage from the power supply 14 and the common GND terminal 27 for grounding, the input terminals for receiving the applied voltage and the grounding are provided for the Hall ICs 15 and 16 respectively. A GND terminal may be provided.

With such a configuration, in the torque sensor 5, when the torsion bar 21 is twisted by the steering wheel 3, the magnet 17 and the yoke 19 are displaced relative to each other, so that the magnetic flux density of the magnetic flux that the Hall element is sensitive to changes. Thus, the electrical outputs obtained from the Hall ICs 15 and 16 change.
As a result, the torque sensor 5 can generate a magnetic flux that changes according to the amount of relative rotational displacement.

  In addition, the Hall ICs 15 and 16 generate electrical outputs of different magnitudes even when the torsion amount of the torsion bar 21 (that is, the relative rotational displacement amount and thus the torque applied to the steering wheel 3) is the same. Is provided. For example, the electrical output obtained from the Hall ICs 15 and 16 changes along different output lines L1 and L2 according to a change in torque (see FIG. 4).

  Here, as shown in FIG. 4, the output lines L1 and L2 are set such that the electrical output changes between the upper limit value VH and the lower limit value VL, and further, the upper limit value VH and the lower limit value VL. Are set to be line symmetric with respect to the straight line Lm passing through the intermediate value VM. The straight line Lm is represented as a correlation line that satisfies the relationship “electrical output = intermediate value VM”, where the vertical axis represents electrical output and the horizontal axis represents torque. Further, it is assumed that the torque when turning the steerable wheel 3 to the right is indicated by a positive value, and the torque when turning the steerable wheel 3 to the left is indicated by a negative value.

  And according to the output line L1, for example, when the torque changes in a negative region and the absolute value of the torque changes in a range larger than the negative threshold value TL, the electrical output indicates the lower limit value VL, When the torque changes in the positive region and the absolute value of the torque changes in a range larger than the positive threshold value TH, the electrical output indicates the upper limit value VH. In addition, when the torque changes in a range between the threshold value TL and the threshold value TH, the electrical output is a positive value that connects (TL, VL) and (TH, VH) in the coordinate system of (torque, electrical output). It changes along a primary correlation line having a slope.

  Further, according to the output line L2, for example, when the torque changes in a negative region and the absolute value of the torque changes in a range larger than the negative threshold value TL, the electrical output indicates the upper limit value VH, When the torque changes in the positive region and the absolute value of the torque changes in a range larger than the positive threshold value TH, the electrical output indicates the lower limit value VL. Further, when the torque changes in a range between the threshold value TL and the threshold value TH, the electrical output is a negative slope connecting (TL, VH) and (TH, VL) in the coordinate system of (torque, electrical output). Varies along a primary correlation line with

  The output lines L1 and L2 are stored in the microcomputer 30 of the ECU 6, and are used for various control processes such as calculation of a torque detection value.

  As shown in FIG. 3, the ECU 6 receives an electrical output from the Hall ICs 15 and 16 and performs a calculation process for controlling energization to the electric motor 2, a drive circuit 31 for the electric motor 2, A noise removing capacitor 28, a pull-down resistor 32 that stabilizes the electrical output obtained from the torque sensor 5, and the like are mounted on the substrate. The microcomputer 30 has a well-known structure including a CPU that performs control processing and arithmetic processing, a ROM that stores various data and programs, a storage device such as a RAM and an EEPROM, an input device, and an output device. Have.

  The microcomputer 30 obtains various detection values necessary for energization control of the electric motor 2 based on the electric output obtained from the torque sensor 5 and the electric output obtained from other sensors. A command value of a current to be supplied to 2 is calculated. Further, the microcomputer 30 synthesizes and outputs a control signal applied to the drive circuit 31 based on the calculated command value. As a result, the electric motor 2 is energized according to the command value, and assist according to the torque.

[Features of Examples]
The features of the EPS 1 of the embodiment will be described with reference to the drawings.
First, the microcomputer 30 of the ECU 6 has failed in the Hall ICs 15 and 16 by energizing the electric motor 2 to generate a relative rotational displacement amount and generating an electrical output from the torque sensor 5 when the engine is started. (Hereinafter, in Hall ICs 15 and 16, those identified as having failed by the failure device identifying means are referred to as failure devices and identified as having failed by the failure device identifying means. What was not done is called a non-failure device).

  The relative rotational displacement generated by the function of the failure device specifying means is generated by the torque applied to the output shaft 10 by the electric motor 2, and is generated when the torque applied to the steering wheel 3 is transmitted to the input shaft 9. The torque is transmitted from a direction different from the relative rotational displacement amount.

  In addition, as a function of the failure device specifying means, the microcomputer 30 energizes the electric motor 2 so that the electrical output based on the generation of the relative rotational displacement at the time of starting the engine temporarily changes over a predetermined threshold. Temporarily vary the current value. Then, the microcomputer 30 identifies the faulty device by determining whether or not the electrical output has changed across the threshold due to the temporary fluctuation of the current value.

Here, the microcomputer 30 stores two different thresholds for electrical output separately from the thresholds TL and TH for torque, and stores the larger threshold of the two thresholds as the larger threshold, and the smaller one. Is stored as the small threshold.
Then, as shown in FIG. 5, the microcomputer 30 alternately causes an excess of electrical output that temporarily exceeds the large threshold value and an excessive excess of electrical output that temporarily falls below the small threshold value. The current value is temporarily changed alternately between the large side and the small side.

At this time, the microcomputer 30 causes the current value to temporarily and fluctuate alternately between the large side and the small side by making the current value follow a sine function or cosine function. Further, the microcomputer 30 repeats such a temporary fluctuation of the current value a plurality of times.
Then, the microcomputer 30 identifies the faulty device by determining whether or not both the excess excess and the excess excess have occurred in the electrical output.

  That is, as shown in FIG. 5A, the microcomputer 30 energizes the electric motor 2 so that the current value follows a sine function when the engine is started, and temporarily changes the current value alternately between the large side and the small side. To fluctuate.

  As a result, for example, as shown in FIG. 5B, when the electrical output of the Hall IC 15 fluctuates according to the sine function, exceeds the large threshold value and falls below the small threshold value, the microcomputer 30 It is determined that both overshoot and overshoot have occurred in the electrical output, and the Hall IC 15 is identified as a non-failure device. If the electrical output of the Hall IC 16 changes, for example, while maintaining a constant value and does not exceed the large-side threshold and does not fall below the small-side threshold, the microcomputer 30 causes the Hall IC 16 to malfunction. Is identified.

  Further, the microcomputer 30 functions as a failure determination unit that determines whether or not there is a failure device in the Hall ICs 15 and 16. For example, the microcomputer 30 constantly calculates the sum sumV of electrical outputs obtained from the Hall ICs 15 and 16. In the microcomputer 30, the sum sumV becomes larger than the upper limit 2VM + α obtained by adding the allowable range α to the numerical value 2VM obtained by doubling the intermediate value VM, or smaller than the lower limit 2VM−α obtained by subtracting the allowable range α from the numerical value 2VM. It is determined that there is a malfunction in the Hall ICs 15 and 16.

  Further, the microcomputer 30 functions as a failure history storage unit that stores the presence of a faulty device when it is determined that there is a faulty device in the Hall ICs 15 and 16. In other words, the microcomputer 30 causes its own EEPROM to function as a failure history storage means, and stores that this EEPROM has a failure device.

  Then, the microcomputer 30 reads the EEPROM failure history at the initial check when the engine is started, and stores the failure device in the Hall ICs 15 and 16 as a function of the failure device specifying means. 2 is energized, and the current value is temporarily changed according to a sine function.

[Control Method of Example]
The control method of EPS1 of an Example is demonstrated based on the flowchart shown in FIG.
Note that the flowchart is divided into one showing processing during engine operation (see FIG. 6A) and one showing processing at engine startup (see FIG. 6B).

  First, during engine operation, the sum sumV is calculated based on the electrical output obtained from the Hall ICs 15 and 16 in step S1. Next, in step S2, it is determined whether or not the sum sumV is within the range of 2VM ± α. If it is determined that the sum V is not within the range of 2VM ± α (NO), it is determined that there is a fault device in the Hall ICs 15 and 16, and the process proceeds to step S3 to determine that there is a fault device in the EEPROM. Remember. When it is determined that the sum sumV is within the range of 2VM ± α (YES), this flow is finished.

  Next, when the engine is started, it is determined in step S4 whether or not the EEPROM stores that there is a faulty device in the Hall ICs 15 and 16. If it is determined that the EEPROM stores the presence of a faulty device (YES), the process proceeds to step S5 to execute processing for specifying the faulty device. If it is determined that the EEPROM does not store that there is a fault device (NO), the process proceeds to step S6 and normal control processing is continued.

  In step S5, the electric motor 2 is energized so that the current value follows a sine function, and the current value is temporarily changed alternately between the large side and the small side. Then, by determining whether or not both the overshoot and overshoot have occurred in the electrical outputs obtained from the Hall ICs 15 and 16 due to temporary fluctuations in the current value, the Hall ICs 15 and 16 Each is identified as a faulty device or a non-faulty device. And it progresses to step S7 and controls the electric motor 2 based on the electrical output of a non-failure device.

[Effects of Examples]
According to the EPS 1 of the embodiment, the ECU 6 controls energization to the electric motor 2 based on two electrical outputs obtained from the Hall ICs 15 and 16 of the torque sensor 5. Then, the microcomputer 30 of the ECU 6 has failed in the Hall ICs 15 and 16 by energizing the electric motor 2 to generate a relative rotational displacement amount and generating an electrical output from the torque sensor 5 when the engine is started. It functions as a faulty device specifying means for specifying.

  In addition, as a function of the failure device specifying means, the microcomputer 30 energizes the electric motor 2 so that the electrical output based on the generation of the relative rotational displacement at the time of starting the engine temporarily changes over a predetermined threshold. Temporarily vary the current value. Then, the microcomputer 30 identifies the faulty device by determining whether or not the electrical output has changed across the threshold due to the temporary fluctuation of the current value.

  Thereby, the microcomputer 30 can specify the fault device with high accuracy. In other words, if the current value to be supplied to the electric motor 2 is temporarily changed, the relative rotational displacement amount is also temporarily changed, and the magnetic flux generated by the magnetic flux generating means 13 is also changed. For this reason, if a failure does not occur in the Hall ICs 15 and 16, the electrical output obtained from the Hall ICs 15 and 16 also temporarily changes across the threshold value.

  Therefore, when the current value for energizing the electric motor 2 is temporarily changed, it is determined whether the electrical output of the Hall ICs 15 and 16 has temporarily changed across the threshold value, thereby determining the Hall IC 15, It is possible to reliably determine whether it is a faulty device every 16 or not. Then, if the use of the electrical output obtained from the faulty device is stopped and the control is continued based on the electrical output obtained from the non-failure device, the EPS1 can be used without weakening the assist force and without stopping the assist. Assist can continue.

  Further, in the case of the failure of the EPS 1, it is hardly considered that the mechanical structural part is broken, and it is considered that some trouble occurs in the signal output system of the torque sensor 5 very rarely. Therefore, when the torque sensor 5 is provided with two Hall ICs 15 and 16, by constructing the ECU 6 as described above, it is possible to almost completely cope with the failure of the EPS 1 without weakening the assist force. In addition, it is possible to continue the assist by the EPS 1 without stopping the assist.

Further, the microcomputer 30 repeats the temporary fluctuation of the current value a plurality of times.
As a result, the temporary fluctuation of the current value and the temporary change of the electrical output are stably repeated. For this reason, since the reliability with respect to the determination whether the electrical output has changed across the threshold value can be enhanced, the reliability with respect to the faulty device identification can be enhanced as a result.

  The microcomputer 30 stores two threshold values, a large threshold value and a small threshold value. When the electrical output temporarily exceeds the large threshold value, the electrical output temporarily exceeds the small threshold value. The current value is temporarily changed alternately between the large side and the small side so that under-under excess is alternately generated. Then, the microcomputer 30 identifies the faulty device by determining whether or not both the excess excess and the excess excess have occurred in the electrical output.

  Thereby, for example, even when the electrical output fluctuates in accordance with the fluctuation of the current value but shifts to the large side or the small side, it can be reliably identified as a fault device. For this reason, the reliability with respect to faulty device identification can be improved.

Further, the microcomputer 30 temporarily varies the current value by causing the current value to follow a sine function or a cosine function.
As a result, the electrical output is stabilized at the maximum or minimum when it temporarily changes. For this reason, the reliability with respect to faulty device identification can be improved.

Further, the microcomputer 30 determines whether or not there is a faulty device in the Hall ICs 15 and 16, and when it is determined that there is a faulty device, the fact that there is a faulty device is stored in the EEPROM. Then, when the EEPROM stores that there is a faulty device, the microcomputer 30 temporarily changes the current value for specifying the faulty device.
Thereby, the microcomputer 30 executes the faulty device specifying process only when the presence of the faulty device is confirmed. For this reason, a faulty device can be identified efficiently.

[Modification]
According to the EPS 1 of the embodiment, the torque sensor 5 has the two Hall ICs 15 and 16, but the torque sensor 5 may be configured to have three or more Hall ICs. In this case, if there are two or more non-failure devices, check whether there is an output abnormality for these non-failure devices by a separate means. Based on this, the energization control of the electric motor 2 can be continued.

  Further, according to the EPS 1 of the embodiment, the microcomputer 30 determines whether or not there is a malfunction in the Hall ICs 15 and 16 during engine operation. Although the failure device is specified later, it may be determined every time the engine is started without determining whether or not there is a failure device in the Hall ICs 15 and 16.

  Further, according to the EPS 1 of the embodiment, the microcomputer 30 energizes the electric motor 2 so that the current value of the electric motor 2 follows a sine function, and temporarily varies the current value alternately between the large side and the small side. However, it is not limited to such an embodiment. For example, the microcomputer 30 may energize the electric motor 2 so that the current value follows a triangular wave, or may energize the electric motor 2 so as to follow an on / off pulse. Further, the microcomputer 30 may temporarily vary the current value only on one side of the large side or the small side so as to generate only one of over excess or under excess in the electrical output. Alternatively, the current value may be temporarily changed only once.

It is a block diagram of an electric power steering device. It is a block diagram of a torque sensor. It is a partial circuit block diagram of an electric power steering device. It is a correlation diagram of the electrical output and torque which are obtained from a torque sensor. (A) is a time chart which shows transition of the electric current value supplied with an electric motor, (b) is a time chart which shows transition of the electrical output of a torque sensor. (A) is a flowchart which shows the control flow of the electric power steering device during engine operation, (b) is a flowchart which shows the control flow of the electric power steering device at the time of engine starting.

Explanation of symbols

1 EPS (Electric Power Steering Device)
2 Electric motor 3 Steering wheel 4 Shaft 5 Torque sensor (torque detection means)
6 ECU (control means)
8 Steering wheel 9 Input shaft (steering wheel side shaft)
10 Output shaft (steering wheel side shaft)
13 Magnetic flux generation means 15 Hall IC (output generation means)
16 Hall IC (output generation means)
30 microcomputer (failure device identification means, failure determination means, failure history storage means)

Claims (5)

An electric motor that generates an output that assists steering of the steering wheel;
A shaft forming a transmission path of torque applied to the steered wheel between the steered wheel and the steered wheel;
Torque detection means that is incorporated in the shaft and generates a plurality of electrical outputs for detecting the torque according to the relative rotational displacement amount of the shaft on the steered wheel side and the shaft on the steered wheel side;
Control means for controlling energization to the electric motor based on the plurality of electrical outputs,
The torque detector includes a magnetic flux generator that generates a magnetic flux that changes according to the relative rotational displacement amount, and a plurality of output generators that generate the electrical output according to the magnetic flux generated by the magnetic flux generator. Have
When the engine is started, the control means energizes the electric motor to generate the relative rotational displacement amount, and generates the plurality of electrical outputs from the torque detection means. A faulty device specifying means for specifying the output generating means that has failed from
This fault device identification means is
Temporarily changing the current value to be applied to the electric motor so that the electrical output temporarily changes over a predetermined threshold,
Identifying the failed output generating means from the plurality of output generating means by determining whether or not the electrical output has changed across the threshold due to a temporary fluctuation of the current value; An electric power steering device. The electric power steering apparatus according to claim 1, wherein
The electric power steering apparatus according to claim 1, wherein the faulty unit specifying means repeats the temporary fluctuation of the current value a plurality of times. In the electric power steering device according to claim 1 or 2,
The faulty device specifying means stores two different threshold values,
Of the two threshold values, the larger threshold value is stored as a larger threshold value, and the smaller threshold value is stored as a smaller threshold value,
The faulty device specifying means includes
The current value is increased between a large value and a small value so that an overshoot that temporarily exceeds the large side threshold and an overshoot that the electric output is temporarily below the small threshold alternately occur. Alternately and temporarily fluctuate to the side,
The faulty output generating means is identified from among the plurality of output generating means by determining whether or not both the overshoot and the overshoot have occurred in the electrical output. Electric power steering device. In the electric power steering apparatus according to any one of claims 1 to 3,
The electric power steering apparatus according to claim 1, wherein the fault device specifying means temporarily changes the current value by following a sine function or a cosine function. In the electric power steering apparatus according to any one of claims 1 to 4,
The control means includes
A failure determining means for determining whether or not there is the failed output generating means among the plurality of output generating means;
A failure history storage unit for storing that the plurality of output generation units include the failed output generation unit when it is determined that the plurality of output generation units include the failed output generation unit; Have
The faulty unit specifying means is configured to temporarily change the current value when the fault history storing means stores that the output generating means that has failed is among the plurality of output generating means. An electric power steering device.

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