JP2011088587A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device capable of easily and reliably detecting the intrusion of water into a torque computing circuit constituting a steering torque detection means. <P>SOLUTION: An electric power steering device comprises a steering torque detection means for detecting steering torque transmitted to a steering mechanism, an electric motor 12 for imparting steering auxiliary force to the steering mechanism and a control unit 30 for driving and controlling the electric motor 12 on the basis of the steering torque detected by the steering torque detection means. The steering torque detection means consists of a steering torque detection part 19 for detecting the steering torque transmitted to the steering mechanism and a torque computing circuit part 23 for computing a steering torque detection value on the basis of a steering torque detection signal outputted from the steering torque detection part 19. A moisture content detecting part 24 is disposed in proximity to the torque computing circuit part 23. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electric power steering apparatus that detects a steering torque transmitted to a steer mechanism by a torque sensor, and controls an electric motor that applies a steering assist force to the steering mechanism based on the detected steering torque.

  Conventionally, when a water droplet sensor is disposed on the inner peripheral portion of the sleeve at each of the left and right ends of the rack housing of the steering device, and water adheres to the surface of the water droplet sensor due to a torn boot or the like, a pair of water droplet sensors When the water resistance is detected because the electrical resistance between the two electrodes is small, and water is detected by either the left or right water drop sensor, the steering motor etc. There is known a steering system that prevents a failure due to a short circuit or the like (see, for example, Patent Document 1).

JP 2006-111032 A

However, in the conventional example described in Patent Document 1, in order to detect the intrusion of water into the right side steering motor and the left side steering motor disposed in the center portion in the rack housing, Since the water drop sensor is arranged on the inner peripheral part of the sleeve at a position close to the boot at both ends, water intrusion from the boot position can be detected by the water drop sensor. It is not possible to detect the presence of intrusion.
Further, in the case of a steering motor, it is usually designed so that a short circuit or the like does not occur when a small amount of water enters, and the influence of water entering the steering motor on the steering system is not so great. .

However, in the steering torque detection means for detecting the steering torque transmitted to the steering shaft, generally, a steering torque detection unit that outputs a detection signal corresponding to the steering torque, and a detection signal in the vicinity of the steering torque detection unit. A torque calculation circuit board that performs a predetermined calculation process and calculates a steering torque detection value is arranged. When water enters the torque calculation circuit board, the steering torque detection value cannot be calculated. For this reason, since it becomes impossible for the control unit to calculate the steering assist current command value for driving and controlling the electric motor based on the detected steering torque value, it is possible to accurately detect the intrusion of water into the torque calculation circuit board. Required.
Therefore, the present invention has been made paying attention to the unsolved problems of the above-described conventional example, and electric power steering capable of easily and reliably detecting water intrusion into the torque calculation circuit constituting the steering torque detecting means. The object is to provide a device.

  In order to achieve the above object, an electric power steering apparatus according to an embodiment includes a steering torque detection unit that detects a steering torque transmitted to a steering mechanism, an electric motor that applies a steering assist force to the steering mechanism, An electric power steering apparatus comprising: a control unit that drives and controls the electric motor based on the steering torque detected by the steering torque detection means; wherein the steering torque detection means is a steering torque transmitted to the steering mechanism. And a torque calculation circuit unit that calculates a steering torque detection value based on a steering torque detection signal output from the steering torque detection unit, and a moisture detection unit is provided in the torque calculation circuit unit. It is characterized by the formation.

Further, in the electric power steering device according to another aspect, the moisture detection unit arranges the pair of comb-like electrodes so that the other comb tooth is positioned between the comb teeth of the one comb-like electrode, It is characterized in that the impedance between the two comb-like electrodes is changed by moisture.
Moreover, the electric power steering apparatus according to another aspect is characterized in that the torque calculation circuit unit includes an impedance monitoring unit that monitors the impedance of the moisture detection unit.
An electric power steering apparatus according to another aspect is characterized in that the control unit includes an impedance monitoring unit that monitors the impedance of the moisture detection unit.

Further, in the electric power steering apparatus according to another aspect, the impedance monitoring unit is configured to determine a moisture detection state when the impedance of the moisture detection unit falls below a preset setting value. It is a feature.
Further, in the electric power steering apparatus according to another aspect, when the control unit determines that the moisture monitoring state is detected by the impedance monitoring unit, an abnormality control unit that performs at least one of outputting an alarm signal and stopping the control of the electric motor It is characterized by having.

According to the present invention, since the moisture detection unit is formed in the torque calculation circuit unit that receives the torque detection signal from the steering torque detection unit and calculates the steering torque detection value, the intrusion of moisture into the torque calculation circuit unit Can be directly and accurately detected.
In addition, the moisture detection unit is constituted by a pair of comb-like electrodes, and the moisture is detected based on the impedance change between the comb-like electrodes, so that the effect of accurately detecting moisture adhesion can be obtained.

1 is a schematic configuration diagram illustrating a first embodiment of an electric power steering apparatus according to the present invention. It is sectional drawing which shows a reduction gear mechanism. It is a schematic diagram which shows the connection relation of a torque sensor board | substrate and a control unit. It is a flowchart which shows an example of the steering assistance control processing procedure performed with a control unit. It is a characteristic diagram which shows a steering auxiliary current command value calculation map. It is a schematic diagram which shows the connection relation of the torque sensor board | substrate and control unit which show the 2nd Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention, where SM is a steering mechanism. The steering mechanism SM has an input shaft 2a through which a steering force applied from a driver is transmitted to the steering wheel 1, and an output shaft 2c connected to the input shaft 2a via a torsion bar 2b shown in FIG. A steering shaft 2 is provided. The steering shaft 2 is rotatably mounted on the steering column 3, one end of the input shaft 2a is connected to the steering wheel 1, and the other end is connected to a torsion bar (not shown).

The steering force transmitted to the output shaft 2c is transmitted to the intermediate shaft 5 through the universal joint 4 constituted by the two yokes 4a and 4b and the cross connecting portion 4c for connecting them, It is transmitted to the pinion shaft 7 through a universal joint 6 composed of yokes 6a and 6b and a cross connecting portion 6c for connecting them.
The steering force transmitted to the pinion shaft 7 is transmitted to the left and right tie rods 9 via the steering gear mechanism 8, and the left and right steered wheels WL and WR are steered by these tie rods 9. Here, the steering gear mechanism 8 is configured in a rack and pinion type having a pinion 8b connected to the pinion shaft 7 and a rack shaft 8c meshing with the pinion 8b in the gear housing 8a, and is transmitted to the pinion 8b. The rotational motion obtained is converted into a linear motion in the vehicle width direction by the rack shaft 8 c and transmitted to the tie rod 9.

A steering assist mechanism 10 for transmitting a steering assist force to the output shaft 2c is connected to the output shaft 2c of the steering shaft 2. The steering assist mechanism 10 includes a reduction gear mechanism 11 connected to the output shaft 2c, and an electric motor 12 composed of, for example, a brushless motor that generates a steering assist force connected to the reduction gear mechanism 11.
Further, as shown in FIG. 2, the reduction gear mechanism 11 includes a gear housing 13 that opens the lower end side, and a cover 14 that closes an opening portion of the gear housing 13. The gear housing 13 accommodates a worm housing portion 16 for housing a worm 15 connected to the output shaft of the electric motor 12, and a worm wheel housing for meshing with the worm 15 and housing a worm wheel 17 integrally attached to the output shaft 2c. Part 18 and a torque sensor storage part 20 for storing a steering torque sensor 19 as a torque detection part connected to the upper end side of the worm wheel storage part 18, and at the upper end of the torque sensor storage part 20, The lower end is fitted.

  The steering torque sensor 19 detects the steering torque applied to the steering wheel 1 and transmitted to the input shaft 2a. For example, the torsion bar 2b is twisted by inserting the steering torque between the input shaft 2a and the output shaft 2c. It converts into angular displacement, this torsional angular displacement is detected as a magnetic change or resistance change, and it converts into an electrical signal. Specifically, as shown in FIG. 2, the torque sensor 19 indicates a twisted state between the input shaft 2a and the output shaft 2c of the steering shaft 2, and the steering torque transmitted to the steering shaft as a pair of detection coils 19a and 19b. The pair of detection coils 19a and 19b are projected in the direction perpendicular to the central axis of the steering column 3, and the tip is parallel to the central axis of the steering column 3. The external connection terminals 19c, 19d and 19e, 19f, which are bent upward, are connected. As shown in FIG. 2, these external connection terminals 19 c to 19 f are inserted and soldered through through holes 22 a to 22 d formed in the torque sensor substrate 22 accommodated in the substrate accommodating portion 21 formed in the gear housing 13. Has been.

  As shown in FIG. 3, torque detection signals output from the detection coils 19 a and 19 b of the steering torque sensor 19 supplied to the through holes 22 a to 22 d are input to the torque sensor substrate 22, and the torque detection signals are included in the torque detection signals. A torque calculation circuit unit 23 for calculating the steering torque detection value T based on this is mounted. The steering torque detection value T calculated by the torque calculation circuit unit 23 is supplied to the control unit 30. Here, the steering torque sensor 19 and the torque calculation circuit unit 23 constitute a steering torque detection means.

Further, a moisture detector 24 is formed on the torque sensor substrate 22 above the torque calculation circuit unit 23. The moisture detection unit 24 has a configuration in which a pair of comb-like electrodes 25 and 26 are arranged to face each other so that the comb teeth are alternately arranged, and one end of the comb-like electrodes 25 and 26 is a torque calculation circuit unit. The impedance monitoring circuit 27 is connected to the impedance monitoring circuit 27.
In the impedance monitoring circuit 27, one of the comb-like electrodes 25 and 26 is connected to the positive power source, the other is connected to the negative power source, and the current flowing through one of the electrodes 25 and 26 is detected, for example. The impedance Z between the comb-like electrodes 25 and 26 is detected, the change in the detected impedance is monitored, and when the impedance Z becomes equal to or less than a preset value Zs, moisture is inserted between the comb-like electrodes 25 and 26. For example, a moisture detection signal WS having a logical value “1” is output to the control unit 30.

  The control unit 30 includes, for example, a micro control unit (MCU), and is preset based on a steering torque detection value T calculated by the torque calculation circuit unit 23 and a vehicle speed detection value detected by a vehicle speed sensor (not shown). Referring to the calculated steering assist current command value calculation map, the steering assist current command value Iref is calculated, and the current deviation between the calculated steering assist current command value and the detected motor current supplied to the electric motor 12 is PI controlled. An arithmetic process is performed to calculate a voltage command value, and the calculated voltage command value is supplied to an inverter 31 that constitutes a motor drive circuit that drives and controls the electric motor 12, and a three-phase motor drive current is formed by the inverter 31, The formed three-phase motor drive current is supplied to the electric motor 12.

Specifically, the control unit 30 executes a steering assist control process shown in FIG.
In this steering assist control process, first, in step S1, the moisture detection signal WS input from the impedance monitoring circuit 27 of the torque calculation circuit unit 23 is read. Then, the process proceeds to step S2 where the moisture detection signal WS is a logical value “ When the moisture detection signal WS is the logical value “1”, it is highly likely that the steering torque detection value T calculated by the torque calculation circuit unit 23 is low in reliability and abnormal. The process proceeds to step S3 to stop the driving of the electric motor 12, and then the steering assist control process is terminated. When the moisture detection signal WS is the logical value “0”, the torque calculation circuit unit 23 is normal. If it is determined, the process proceeds to step S4.

  In step S4, the steering torque detection value T calculated by the torque calculation circuit unit 23, the vehicle speed detection value detected by a vehicle speed sensor (not shown), the motor currents Iu, Iv, Iw detected by the motor current detection unit 33, and the like. The detected value is read, and then the process proceeds to step S5, where the steering assist current command value Iref is calculated based on the steering torque T with reference to the steering assist current command value calculation map shown in FIG.

  Here, as shown in FIG. 5, the steering assist current purchase value calculation map has a parabolic shape in which the horizontal axis represents the steering torque detection value T, the vertical axis represents the steering assist current command value Iref, and the vehicle speed Vs is a parameter. The current command value Iref is maintained at “0” while the steering torque T is from “0” to a set value Ts1 in the vicinity thereof, and the steering torque T is set at the set value Ts1. When the steering torque T is exceeded, initially, the steering assist current command value Iref increases relatively slowly as the steering torque T increases. However, when the steering torque T further increases, the steering assist current command value Iref increases steeply. The characteristic curve is set so that the inclination becomes smaller as the vehicle speed increases.

  Next, the process proceeds to step S6, where d-q axis command value calculation processing is executed based on the calculated steering assist current command value Iref to calculate the d-axis current command value Idref and the q-axis current command value Iqref, and then step S7. Then, the d-axis current command value Idref and the q-axis current command value Iqref are two-phase / 3-phase converted to calculate the three-phase current command values Iuref, Ivref, and Iwref, and then the process proceeds to step S8.

  In this step S8, the motor current detection values Iw, Iv and Iw are individually subtracted from the three-phase current command values Iuref, Ivref and Iwref to calculate current deviations ΔIu, ΔIv and ΔIw, and then the process proceeds to step S9. The calculated current deviations ΔIu, ΔIv, and ΔIw are subjected to PI (proportional / integral) control calculation to calculate the three-phase voltage command values Vuref, Vvref, and Vwref.

Next, the process proceeds to step S10, a pulse width modulation process is performed based on the calculated three-phase voltage command values Vuref, Vvref and Vwref to form a gate drive signal for the inverter, and then the process proceeds to step S11. The gate drive signal thus output is output to the inverter 31 constituting the motor drive circuit, and the process returns to step S1.
In the process of FIG. 4, the process of step S2 corresponds to the abnormality control unit.

Next, the operation of the first embodiment will be described.
When an ignition switch (not shown) of the vehicle is turned on and electric power is supplied to the control unit 30 from a battery (not shown), the control assisting control process shown in FIG.
At this time, in a state where moisture does not enter the substrate housing portion 21 of the gear housing 13, the impedance between the comb-like electrodes 25 and 26 of the moisture detector 24 is maintained at a high level. A moisture detection signal WS having a logical value “0” is output.

  For this reason, when the steering assist control process of FIG. 4 is executed, the moisture detection signal WS read in step S1 is the logical value “0”, so that the routine proceeds from step S1 to step S4, and normal steering is performed. Auxiliary control processing is executed. Therefore, referring to the steering assist current command value calculation map of FIG. 5 based on the steering torque detection value T calculated by the torque calculation circuit unit 23 and the vehicle speed detection value detected by the vehicle speed sensor (not shown), the steering assist current is calculated. The command value Iref is calculated. Based on the steering assist current command value Iref, a dq axis current command value calculation process is performed to calculate a d axis current command value Idref and a q axis current command value Iqref, and the calculated d axis current command values Idref and q The shaft current command value Iqref is subjected to a two-phase / three-phase conversion process to calculate three-phase current command values Iuref, Ivref and Iwref.

  Then, current deviations ΔIu, ΔIv and ΔIw between the three-phase current command values Iuref, Ivref and Iwref and the motor currents Iu, Iv and Iw detected by the current detection unit 33 are calculated, and the calculated current deviations ΔIu, ΔIv and ΔIw are calculated. PI control processing is performed for the three-phase voltage command values Vuref, Vvref and Vwref, and these three-phase voltage command values Vuref, Vvref and Vwref are subjected to pulse width modulation processing to form a gate drive signal for the inverter 31. The formed gate drive signal is output to the inverter 31. For this reason, a motor drive current is supplied from the inverter 31 to the electric motor 12 to drive the electric motor 12 so as to generate a steering assist force required in the forward rotation or reverse rotation direction.

Therefore, a steering assist force corresponding to the steering torque generated by steering the steering wheel 1 from the electric motor 12 is generated, and this steering assist force is applied to the output shaft 2 c of the steering shaft 2 via the worm 15 and the worm wheel 17. By being transmitted, the steering wheel 1 can be steered with a light steering force.
By the way, if for some reason water enters the substrate housing portion 21 of the gear housing 13 and water adheres between the comb teeth of the comb-like electrodes 25 and 26 of the moisture detector 24 or is immersed in water. When it is detected that the impedance Z between the comb-like electrodes 25 and 26 has greatly decreased and the impedance Z detected by the impedance monitoring circuit 27 has decreased below the set value Zs, the moisture detection signal WS is changed from the logical value “0”. Inverted to logic “1”.

  For this reason, in the steering assist control process shown in FIG. 4, the moisture detection signal WS read in step S <b> 1 becomes a logical value “1”, and thus the steering torque detection value T calculated by the torque calculation circuit unit 23 is reliable. If it is determined that there is not, the process proceeds from step S1 to step S2, and an abnormal control process is performed in which the voltage command values Vuref to Vwref are set to “0”, the electric motor 12 is stopped, and the steering assist control process is terminated. As a result, the generation of the steering assist force by the electric motor 12 is immediately stopped.

For this reason, it is possible to reliably prevent the steering assist control process based on the unreliable steering torque detection value T calculated by the torque calculation circuit unit 23 from being executed.
As described above, according to the first embodiment, since the moisture detection unit 24 is disposed in the vicinity of the torque calculation circuit unit 23, the intrusion of moisture into the torque calculation circuit unit 23 can be accurately detected. A decrease in reliability of the detected steering torque value T calculated by the arithmetic circuit unit 23 can be detected quickly and accurately.

  In the first embodiment, the impedance between the comb-like electrodes 25 and 26 of the moisture detector 24 is monitored by the impedance monitoring circuit 27, and the impedance between the comb-like electrodes 25 and 26 is below a set value. The case where the steering assist control process is stopped and the driving of the electric motor 12 is stopped when it is lowered has been described. However, the present invention is not limited to this. When detected, an abnormal control process for suppressing the motor drive current for the electric motor 12 or issuing an alarm to the driver may be executed.

Next, a second embodiment of the present invention will be described with reference to FIG.
In the second embodiment, the impedance monitoring circuit 27 provided in the torque calculation circuit unit 23 is omitted, and instead, the impedance between the comb-like electrodes 25 and 26 of the moisture detection unit 24 is controlled on the control unit 30 side. It is intended to be monitored.
That is, in the second embodiment, as shown in FIG. 6, the other ends of the comb-like electrodes 25 and 26 of the moisture detection unit 24 are directly input to the control unit 30 via the signal lines 41a and 41b. . The impedance monitoring circuit 27 is provided on the input side of the control unit 30 and the moisture detection signal WS output from the impedance monitoring circuit 27 is read by the steering assist control process executed by the control unit 30 as described above. The parts corresponding to those of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  According to the second embodiment, the impedance monitoring circuit 27 is provided on the control unit 30 side, and the impedance monitoring circuit 27 detects the impedance Z between the comb-like electrodes 25 and 26 of the moisture detector 24. The same effect as the first embodiment can be obtained. In addition to this, by providing the impedance monitoring circuit 27 on the control unit 30 side, the impedance monitoring circuit 27 is not affected by the intruding moisture, and the intrusion of moisture into the torque calculation circuit unit 23 is accurately detected. be able to.

In the first and second embodiments, the column type electric power steering apparatus in which the steering assist mechanism 10 is connected to the output shaft 2c of the steering shaft 2 has been described. However, the present invention is not limited to this. The auxiliary mechanism 10 may be connected to the pinion shaft 7 of the steering gear mechanism 8 or the rack shaft may be directly driven by a steering motor as in the conventional example described above.
Further, the installation position of the steering torque sensor 19 is not limited to being installed at a position above the intermediate shaft 5, and can be arranged at an intermediate portion between the intermediate shaft 5 and the pinion shaft 7.

Moreover, although the said 1st and 2nd embodiment demonstrated the case where the external connection terminals 19c-19f of the steering torque sensor 19 were bent and formed in the L-shape, it is not limited to this, External connection terminals 19c to 19f may be formed in a straight line extending in a direction orthogonal to the central axis of the steering shaft 2, and the torque sensor substrate 22 may be disposed in parallel to the central axis of the steering shaft 2.
Moreover, in the said embodiment, although the case where the motor drive circuit was comprised by the inverter 31 was demonstrated, when not applying to this and a brushed electric motor is applied as an electric motor, motor drive An H-bridge circuit may be applied as the circuit.

SM ... steering mechanism, 1 ... steering wheel, 2 ... steering shaft, 3 ... steering column, 4 ... universal joint, 5 ... intermediate shaft, 7 ... pinion shaft, 8 ... steering gear mechanism, 9 ... tie rod, WL, WR ... rolling Steering wheel, 10 ... steering assist mechanism, 11 ... reduction gear mechanism, 12 ... electric motor, 13 ... gear housing, 19 ... steering torque sensor, 21 ... board housing part, 22 ... torque sensor board, 23 ... torque calculation circuit part, 24 ... Moisture detector, 25, 26 ... comb-like electrode, 27 ... impedance monitoring circuit, 30 ... control unit, 31 ... inverter, 33 ... motor current detector

Claims (6)

Steering torque detection means for detecting steering torque transmitted to the steering mechanism, an electric motor for applying steering assist force to the steering mechanism, and drive control of the electric motor based on the steering torque detected by the steering torque detection means An electric power steering device comprising a control unit for
The steering torque detector includes a steering torque detector that detects a steering torque transmitted to the steering mechanism, and a torque calculation circuit that calculates a steering torque detection value based on a steering torque detection signal output from the steering torque detector. And consists of
An electric power steering apparatus, wherein a moisture detector is formed in the vicinity of the torque calculation circuit.   The moisture detecting unit arranges a pair of comb-like electrodes so that the other comb-tooth is located between the comb-teeth of one comb-like electrode, and the impedance between the two comb-like electrodes is changed by moisture. The electric power steering apparatus according to claim 1, wherein the electric power steering apparatus is configured as follows.   The electric power steering apparatus according to claim 1, wherein the torque calculation circuit unit includes an impedance monitoring unit that monitors an impedance of the moisture detection unit.   The electric power steering apparatus according to claim 1, wherein the control unit includes an impedance monitoring unit that monitors the impedance of the moisture detection unit.   5. The electric power according to claim 3, wherein the impedance monitoring unit is configured to determine a moisture detection state when the impedance of the moisture detection unit falls below a preset set value. Steering device.   6. The control unit according to claim 1, further comprising an abnormality control unit that performs at least one of outputting an alarm signal and stopping the control of the electric motor when the impedance monitoring unit determines that the moisture is detected. The electric power steering device according to any one of the above.

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