JP5482009B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering device that detects a steering torque transmitted to a steering mechanism and applies a steering assist force to the steering mechanism based on the detected steering torque.

  As this type of electric power steering device, for example, as a torque detection device for detecting a steering torque, a coil assembly including a coil and a housing for housing the coil and a pedestal provided in the housing, and a process for processing a signal from the coil A circuit board including a circuit and received by the pedestal part, and a conductor mounting screw for attaching the circuit board to the pedestal part by being inserted into the pedestal part through the circuit board, and using the mounting screw A simple work of attaching the board to the pedestal is known to achieve electrical continuity between the processing circuit of the circuit board and the coil via the mounting screw without soldering (for example, (See Patent Document 1).

  An electric power steering apparatus having a torque sensor for detecting torque using a coil winding disposed in an electromagnetic yoke, wherein a coil bobbin housed in the electromagnetic yoke and a part of the coil bobbin are moved outward And a connecting pin protruding from the terminal block, the connecting pin including a connecting member for connecting to the sensor circuit board, and the connecting pin is not covered by the sensor circuit board. An electric power steering apparatus configured as described above has been proposed (see, for example, Patent Document 2).

JP 2005-326188 A International Publication No. 2004/009424 Pamphlet

  However, in the conventional example described in Patent Document 1, the processing circuit of the circuit board and the coil can be electrically connected by a mounting screw without using soldering. There is a possibility that metal powder may be generated when tightening the screw, and there is an unresolved problem that the generated metal powder may cause a short-circuit condition, and the mounting screw may be removed due to failure investigation etc. In this case, if there is a problem with the mounting screw, it may not be possible to save the defective part, and the electrical connection status will change, which may affect the subsequent investigation to some extent. There is also a problem to be solved.

  In the conventional example described in Patent Document 2, a connection pin is formed by connecting a connection pin protruding from a terminal block protruding a part of a coil bobbin and a sensor circuit board with a connection member. Is configured so that it is not covered by the sensor circuit board, so that when soldering is performed between the connecting pin and the connecting member, the soldering location can be visually recognized from the outside, so the soldering state can be confirmed. However, since it is necessary to provide a connecting member and the connecting pin and the connecting member are soldered outside the sensor circuit board, there is an unsolved problem that the storage area becomes large.

  Therefore, the present invention has been made paying attention to the unsolved problem of the above-described conventional example, when the circuit board and the terminal of the coil are connected using soldering without using a mounting screw. It is an object of the present invention to provide an electric power steering device that can easily check a soldering point.

In order to achieve the above object, an electric power steering apparatus according to an embodiment includes a steering torque detecting means for detecting a steering torque transmitted to a steering mechanism, and an electric motor for generating a steering assist force for the steering mechanism. An electric power steering device for controlling the electric motor based on the steering torque detected by the steering torque detection means, wherein the steering torque detection means detects the steering torque transmitted to the steering mechanism. A detection unit; a circuit board on which a torque detection circuit for driving the steering torque detection unit to calculate a steering torque detection value is mounted; and a housing facing the steering torque detection unit. It is composed of a substrate accommodating portion for accommodating a circuit board therein, the steering torque detecting unit and said circuit board extension Are connected by electrical connection members interposed member, the circuit board side of the elastic member of the electrical connecting member, the circuit board, from the surface side in a state where the circuit board is accommodated in the board housing portion Solder is soldered so as to reach the back surface side, and the expansion / contraction member expands the expansion / contraction member, thereby moving the circuit board to the outside of the substrate housing portion and making it possible to visually recognize the soldering state on the back surface side. The amount of expansion is set so that

Further, in the electric power steering apparatus according to another embodiment, a solder blocking member is disposed to prevent solder from flowing into the expansion / contraction member when soldering to at least the circuit board side of the electrical connecting member. that it is characterized by.

  Furthermore, an electric power steering apparatus according to another aspect is characterized in that the electrical connection member is configured to be able to maintain the electrical connection state at least during the expansion process of the expansion / contraction member.

  According to the present invention, a torque detection unit that detects steering torque transmitted to the steering mechanism and a signal processing circuit that calculates a steering torque detection value by performing signal processing on the torque detection signal detected by the torque detection unit are implemented. Steering torque detection means including a circuit board is provided, the torque detection unit and the circuit board are coupled by an electrical connection member having an elastic member interposed therebetween, and the electrical connection member and the circuit board are soldered. Therefore, by extending the expansion / contraction member of the electrical connection member, it is possible to visually recognize the soldering state on the back surface side of the circuit board, and the effect that the quality of soldering can be judged accurately can be obtained.

  At this time, it is possible to confirm the soldering location in the energized state by configuring so that the electrical connection state between the torque detection unit and the circuit board by the electrical connection member can be maintained at least in the extension process of the expansion / contraction member. it can.

1 is a schematic configuration diagram illustrating a first embodiment of an electric power steering apparatus according to the present invention. It is an expanded sectional view which shows the steering gear mechanism of FIG. It is a perspective view which shows a torque detection part. It is a figure which shows the connection relation of a torque detection part and a circuit board. It is sectional drawing which shows the specific structure of an electrical connection member. It is a figure explaining the magnitude | size of the torque of a torque sensor, and the inductance change of two detection coils. It is a circuit diagram which shows a torque detection circuit. It is a figure similar to FIG. 4 which shows the 2nd Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view showing an electric power steering apparatus according to the present invention, in which SM denotes a steering mechanism. The steering mechanism SM includes a steering wheel 1 to which a steering torque is transmitted from a driver, and a steering shaft 2 that supports the steering wheel 1. The steering shaft 2 is rotatably mounted on the steering column 3, and the end of the steering shaft 2 opposite to the steering wheel 1 is composed of two yokes 4a and 4b and a cross connecting portion 4c for connecting them. For example, a rack-and-pinion type steering gear is connected to the intermediate shaft 5 via the universal joint 4 and further includes a universal joint 6 including two yokes 6a and 6b and a cross-connecting portion 6c for connecting them. It is connected to the mechanism 8. The left and right tie rods 9 of the steering gear mechanism 8 are connected to left and right steered wheels (not shown).

  As shown in FIG. 2, the steering gear mechanism 8 is configured by dividing the housing 11 into an input-side half 11a and an output-side half 11b. Inside the housing 11, an input shaft 12 connected to the yoke 6b of the universal joint 6 and an output shaft 14 connected to the input shaft 12 via a torsion bar 13 are rotatable by bearings 15a, 15b and 15c. It is supported by.

  The input shaft 12, the torsion bar 13 and the output shaft 14 are coaxially arranged, and the input shaft 12 and the torsion bar 13 are spline-coupled, and the torsion bar 13 and the output shaft 14 are also spline-coupled. 2, a pinion shaft 16 is integrally formed on the opposite side of the output shaft 14 from the torsion bar 13, and the pinion shaft 16 meshes with a rack 17 to constitute a rack and pinion type steering mechanism. .

A worm wheel 18 that is coaxial and rotates integrally with the output shaft 14 is fixed to the torsion bar 13 side, and a worm 20 driven by an electric motor 19 is engaged with the worm wheel 18. . The worm wheel 18 has a synthetic resin tooth portion 18b fixed to a metal hub 18a.
The rotational force of the electric motor 19 is transmitted to the output shaft 14 via the worm 20 and the worm wheel 18, and a steering assist force in an arbitrary direction is applied to the output shaft 14 by appropriately switching the rotational direction of the electric motor 19. The

  As shown in FIG. 2, a steering torque sensor 21 is disposed on the inner peripheral surface of the input side half body 11 a that faces the outer peripheral surface of the engagement end portion of the input shaft 12 with the output shaft 14. As shown in FIG. 3, the steering torque sensor 21 includes a sensor shaft portion 22 as a magnetic quantity variable portion made of a magnetic material formed on the output shaft 14 side of the input shaft 12, and an input-side half body 11a of the housing 11. The torque detection unit DT includes a pair of magnetic yoke units 25 and 26 that house detection coils 23 and 24 arranged inside the motor.

  As shown in FIG. 3, a plurality of, for example, nine ridges 22 a having a relatively narrow width extending in the axial direction are formed on the sensor shaft portion 22 in the circumferential direction at regular intervals. Further, on the outside of the sensor shaft portion 22, a cylindrical member 27 made of a conductive and non-magnetic material such as aluminum is disposed close to the sensor shaft portion 22 and coaxially with the sensor shaft portion 22. The extension 27 e of the cylindrical member 27 is fixed to the outside of the end 14 e of the output shaft 14.

  The cylindrical member 27 includes a plurality of, for example, nine rectangular windows 27a arranged at equal intervals in the circumferential direction at positions facing the protrusions 22a formed on the surface of the sensor shaft portion 22 described above. A first window row and a plurality of, for example, nine rectangular windows 27b having the same shape as the window 27a but having different phases in the circumferential direction are arranged at positions shifted in the axial direction from the first window row. Two window rows are formed.

  The outer periphery of the cylindrical member 27 is surrounded by magnetic yoke portions 25 and 26 around which detection coils 23 and 24 of the same standard are wound. That is, the detection coils 23 and 24 are arranged coaxially with the cylindrical member 27, the detection coil 23 surrounds the first window row portion made of the window 27a, and the detection coil 24 has the second window row portion made of the window 27b. Siege.

  As shown in FIGS. 3 and 4, each of the magnetic yoke portions 25 and 26 includes an annular portion 29 formed in a concave section by forming a groove portion 28 for receiving the detection coils 23 and 24 on the inner peripheral surface, It is composed of a terminal support portion 30 protruding from a part of the outer peripheral surface of the annular portion 29, and two rod-like terminals led out from both ends of the detection coils 23 and 24 protruding from the terminal support portion 30, respectively. Electrical connection members 31a and 31b.

  As shown in FIG. 4, each of the electrical connecting members 31 a and 31 b is a pair of upper and lower conductive rod portions 32 and 33, and a conductive elastic member that connects the rod portions 32 and 33. And a tension coil spring 34. The tension coil spring 34 is formed with locking portions 35 extending inward in the radial direction at both upper and lower ends thereof, and these locking portions 35 are press-fitted into the insertion holes 36 formed in the rod portions 32 and 33 and fixed. Has been. Here, the extension amount of the tension coil spring 34 is set so that soldering on the back side of the circuit board 42 described later can be visually recognized. In addition, a ring-shaped solder blocking member 37 serving as a solder return facing the circuit board described later at a predetermined distance from below is fixed to the upper bar portion 32.

  On the other hand, as shown in FIG. 2, a substrate housing portion 40 is formed in the housing 11 at a position facing the electrical connection members 31 a and 31 b of the magnetic yoke portions 25 and 26, and the magnetic yoke portion 25 is formed in the substrate housing portion 40. A circuit board 42 on which a torque detection circuit 41 as a torque detection unit for detecting torque by energizing and driving the detection coils 23 and 24 housed in 26 and 26 is mounted in parallel with the axial direction of the input shaft 12.

  In the circuit board 42, through holes 43a and 43b are formed through which the rod portions 32 of the electrical connection members 31a and 31b are inserted, and the rod portion 32 is inserted into the through holes 43a and 43b from the lower surface side. Then, the back surface of the circuit board 42 is placed and positioned on the support member 44 formed in the housing portion 40, and in this state, the bar portion 32 is soldered from the upper side of the circuit board 42.

  The circuit board 42 has a steering assist current command value for causing the electric motor 19 to generate a steering assist force corresponding to the steering torque applied to the steering system based on at least the torque detection value output from the torque detection circuit 41. An arithmetic processing device 45 that calculates and calculates a voltage command value and a motor drive circuit 46 that drives the electric motor 19 based on the voltage command value output from the arithmetic processing device 45 are mounted.

Next, the operation of the above embodiment will be described.
Now, when the steering torque when the steering wheel 1 is not being steered is zero, the torsion bar 13 is not twisted, and the input shaft 12 and the output shaft 14 are not relatively rotated. Yes. In this state, relative rotation does not occur between the protrusion 22a on the surface of the sensor shaft portion 22 on the input shaft 2 side and the cylindrical member 27 on the output shaft 14 side.

  On the other hand, when the steering wheel 1 is operated and a rotational force is applied to the input shaft 12, the rotational force is transmitted to the output shaft 14 via the torsion bar 13. At this time, the friction force such as the friction force between the steered wheels and the road surface and the meshing of the gear of the steering mechanism 8 coupled to the output shaft 14 acts on the output shaft 14, so that the input shaft 12 and the output shaft 14 Torsion occurs in the torsion bar 13 that connects the two, and relative rotation occurs between the ridge 22 a on the surface of the sensor shaft portion 22 on the input shaft 12 side and the output shaft 14.

  At this time, since the windows 27a and 27b are formed in the cylindrical member 27, when an alternating current is generated by flowing an alternating current through the detection coils 23 and 24, an eddy current generated on the outer peripheral surface of the cylindrical member 27 is The inner circumferential surface of the cylindrical member 27 wraps around the inner circumferential surface side of the cylindrical member 27 along the end surfaces of the 27a and 27b, flows in the same direction as the coil current through the inner circumferential surface, and the inner circumferential surface of the cylindrical member 27 along the end surfaces of the adjacent windows 27a and 27b. Wrap around the inner peripheral surface in the same direction as the coil current, and return to the outer peripheral surface side along the end surfaces of the adjacent windows 27a and 27b to form a loop. That is, a state occurs in which eddy current loops are periodically arranged in the circumferential direction inside the detection coils 23 and 24.

Here, the magnetic field due to the coil current and the magnetic field due to the eddy current are superposed, and the inside and outside of the cylindrical member 27 have a magnetic field that periodically changes in strength in the circumferential direction and a gradient in the radial direction that becomes smaller toward the center. A magnetic field is formed. The strength of the periodic magnetic field in the circumferential direction is strong at the centers of the windows 27a and 27c affected by the adjacent eddy currents, and becomes weaker as they deviate from the center.
A sensor shaft portion 22 made of a magnetic material is coaxially arranged inside the cylindrical member 27, and the ridges 22a are arranged at the same cycle as the windows 27a and 27b.

  A magnetic substance placed in a magnetic field is magnetized to generate a magnetic flux, but the amount of magnetic flux increases according to the strength of the magnetic field until it is saturated. For this reason, the magnetic flux generated in the sensor shaft portion 22 by the cylindrical member 27 due to the strength of the periodic magnetic field in the circumferential direction and the magnetic field having a gradient in the radial direction that decreases toward the center is generated between the cylindrical member 27 and the sensor. It increases or decreases depending on the relative phase with the shaft portion 22.

The phase at which the magnetic flux becomes maximum is such that the centers of the windows 27a and 27b of the cylindrical member 27 and the center of the ridge 22a of the sensor shaft portion 22 coincide with each other, and the inductances of the detection coils 23 and 24 also vary according to the increase or decrease of the magnetic flux Increase / decrease and change to a substantially sinusoidal shape.
In the state where torque does not act, the center of the ridge 22a of the sensor shaft portion 22 is 360 ° / phase with respect to the phase where the inductance is maximum (the phase where the windows 27a and 27b and the center of the ridge 22a coincide). If the position is shifted by an angle of (the number of convex portions × 4), the torque acts to twist the torsion bar 13 and a phase is generated between the sensor shaft portion 22 and the cylindrical member 27. One of the inductances of the coils 23 and 24 increases and the other decreases as shown in FIG.

For this reason, when the steering torque in the clockwise direction is generated, the cylindrical member 27 rotates in the clockwise direction, so that the inductance L23 of the detection coil 23 increases as the torque increases, as shown in FIG. L24 decreases.
Further, when the counterclockwise steering torque is generated, the cylindrical member 27 rotates counterclockwise, so that the inductance L23 of the detection coil 23 decreases as the torque increases, as shown in FIG. The inductance L24 increases.

  Then, in the torque detection circuit 41, as shown in FIG. 7, the resistor R1 and the detection coil 23 are connected in series, the resistor R2 and the detection coil 24 are connected in series, and both are connected in parallel. A bridge circuit is configured, and the connection point between the resistors R1 and R2 is connected to the AC power source 47, the connection point between the detection coils 23 and 24 is grounded, and the connection point between the resistors R1 and 23 and the connection between the resistors R1 and 24 is connected. By detecting the voltage signal appearing at both ends of the detection coils 23 and 24 from the point and amplifying and smoothing the voltage signal by the signal processing unit 48, the detected steering torque value T can be obtained.

  Then, the obtained steering torque detection value T is input to the arithmetic processing unit 45 to calculate the steering auxiliary current command value, and the motor current detection value obtained by detecting the steering auxiliary current command value and the motor current flowing through the electric motor 19. The voltage command value is calculated by performing PI (proportional / integral) calculation processing on the calculated current deviation, and the calculated voltage command value is supplied to the motor drive circuit 46. Therefore, the motor drive circuit 46 forms a motor drive current, and the generated motor drive current is supplied to the electric motor 19 so that the electric motor 19 is rotationally driven, and the steering assist force according to the steering torque detection value T. And the steering assist force is transmitted to the output shaft 14 via the worm 20 and the worm wheel 18, so that the steering wheel 1 can be steered with a light steering force.

  By the way, in this embodiment, as mentioned above, the steering torque sensor 21 calculates the steering torque detection value T by energizing and driving the detection coils 23 and 24 constituting the steering torque detector and the detection coils 23 and 24. And the circuit board 42 on which the torque detection circuit 41 is mounted, and the detection coils 23 and 24 and the circuit board 42 are electrically connected by electrical connection members 31a and 31b. At this time, the rod portion 32 and the circuit board 42 are soldered in a state in which the rod portion 32 of the electrical connection members 31a and 31b is inserted into the through holes 42a and 42b formed in the circuit board 42, thereby electrically connecting the two. Can be firmly connected.

  As described above, when the electrical connection members 31a and 31b and the circuit board 42 are soldered, it is necessary to inspect whether the soldering is normally performed. On the surface side of the circuit board 42, The direct soldering location can be visually recognized, and the quality of the soldered state can be immediately determined, but the soldered state on the back side of the circuit board 42 cannot be directly visually confirmed.

  At this time, since the tension coil spring 34 is inserted between the bar portions 32 and 33 of the electrical connection members 31a and 31b, by lifting the circuit board 42 upward, as shown by the one-dot chain line in FIG. The tension coil spring 34 extends and the back surface of the circuit board 42 can be moved upward from the board housing portion 40, and the soldering state on the back surface side of the circuit board 42 can be easily visually confirmed. Can be judged.

Moreover, since the tension coil spring 34 has conductivity, the torque detection circuit 41 can determine whether the soldering is good or not while the detection coils 23 and 24 are energized with the AC power supply, and the soldering state can be accurately determined. Can be determined.
In addition, the bar portion 32 is formed with a solder blocking member 37 that is opposed to the lower surface of the circuit board 42 at a predetermined distance, so that when soldering between the bar portion 32 and the circuit board 42, solder is not applied. Even if the rod portion 32 flows down, the solder blocking member 37 prevents the flow downward from the rod portion 32. Therefore, it is ensured that the solder adheres to the tension coil spring 34 and the tension coil spring 34 cannot be extended. Can be prevented.

Next, a second embodiment of the present invention will be described with reference to FIG.
In the second embodiment, a telescopic rod is applied in place of the tension coil spring 34 as the expansion / contraction member of the electrical connection members 31a and 31b.
That is, in the second embodiment, as shown in FIG. 8, a telescopic telescopic rod 51 having electrical conductivity as a telescopic member is provided between the bar portions 32 and 33 constituting the electrical connection members 31a and 31b. Except for the fact that they are connected with each other, the configuration is the same as that of the first embodiment described above, and the same reference numerals are given to the corresponding parts to those in FIG. 4, and the detailed description thereof will be omitted.

  In the second embodiment, since the upper and lower rod portions 32 and 33 of the electrical connection members 31a and 31b are connected by the conductive telescopic rod 51, the telescopic rod 51 is contracted. In this state, the rod part 32 of the electrical connection members 31a and 31b is inserted into the through holes 43a and 43b of the circuit board 42, and the rod part 32 and the circuit board 42 are soldered, whereby the circuit board 42 is detected. 23 and 24 can be held in the substrate housing portion 40 in an electrically connected state.

  When the soldering between the bar portion 32 and the circuit board 42 is completed and the soldered state is inspected, the surface side of the circuit board 42 is directly visually recognized as in the first embodiment. Thus, whether the soldering state is good or not can be determined. The soldering state on the back side of the circuit board 42 is determined by lifting the circuit board 42 upward and extending the telescopic rod 51. As in the first embodiment, the back surface side of the circuit board 42 can be drawn upward from the upper surface of the substrate housing portion 40. In this state, the soldering state on the back surface side of the circuit board 42 can be visually confirmed. The quality of the attached state can be determined.

Further, since the telescopic rod 51 has conductivity, the torque detection circuit 41 can visually recognize the soldering state on the back side of the circuit board 42 in a state where the detection coils 23 and 24 are energized. Can be accurately determined.
In addition, in the said 1st and 2nd embodiment, although the case where the tension coil spring 34 or the telescopic rod 51 was applied as an expansion-contraction member was demonstrated, it is not limited to these, A bamboo child spring and electroconductivity are used. An elastic member such as a rubber material that does not have can be applied. If the elastic member does not have conductivity, a flexible wiring for electrically connecting the rod portions 32 and 33 is separately provided. do it. Further, the rod portions 32 and 33 may be stretchable by spline coupling or serration coupling, and may be urged by an elastic member in the contraction direction.

  DESCRIPTION OF SYMBOLS 11 ... Housing, 11a ... Input side half, 11b ... Output side half, 12 ... Input shaft, 13 ... Torsion bar, 14 ... Output shaft, 16 ... Pinion shaft, 17 ... Rack, 18 ... Worm wheel, 19 ... Electric Motor, 20 ... Worm, 21 ... Torque sensor, 22 ... Sensor shaft, 23, 24 ... Detection coil, 25, 26 ... Magnetic yoke, 27 ... Cylindrical member, 30 ... Terminal support, 31a, 31b ... Electrical connection Member, 32, 33 ... Rod, 34 ... Tension coil spring, 40 ... Substrate housing space, 41 ... Torque detection circuit, 42 ... Circuit board, 43a, 43b ... Through hole, 51 ... Nested rod

Claims (3)

Steering torque detection means for detecting a steering torque transmitted to the steering mechanism; and an electric motor for generating a steering assist force for the steering mechanism, and the electric motor is controlled based on the steering torque detected by the steering torque detection means. An electric power steering device to control,
The steering torque detection means includes a steering torque detection unit that detects a steering torque transmitted to the steering mechanism, and a circuit board on which a torque detection circuit that drives the steering torque detection unit and calculates a steering torque detection value is mounted. , Provided in a housing facing the steering torque detection unit, and is configured by a board housing part that opens the outside and houses the circuit board inside ,
The steering torque detector and the circuit board are connected by an electrical connection member having an expansion / contraction member interposed therebetween, and the circuit board side from the expansion / contraction member of the electrical connection member is connected to the circuit board. Solder so that the solder reaches the back side from the front surface side in a state of being accommodated in the substrate housing part,
The stretchable member is set to have an extension amount so that the stretchable member is stretched to move the circuit board to the outside of the board housing portion so that the soldered state on the back side can be visually recognized. An electric power steering device.   2. The electric power according to claim 1, wherein a solder blocking member that prevents solder from flowing into the expansion and contraction member during soldering is disposed at least on the circuit board side of the electrical connecting member. Steering device. 3. The electric power steering apparatus according to claim 1, wherein the electrical connection member is configured to be able to maintain the electrical connection state at least during the extension process of the expansion and contraction member.

Images