JP2009023461A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent radio noise from being emitted to the outside, by controlling a flow of an AC current component and one of a DC current component to a part requiring grounding while preventing deterioration in EMC (electromagnetic compatibility) due to intrusion of an electromagnetic wave from the outside. <P>SOLUTION: An electric power steering device has the following configuration. A control unit 19 has a conductive cover 26 that covers other substrates or the like while being electrically connected with a load circuit 23. The control unit is directly mounted onto the outer periphery of a speed-reduction gearbox 4 so as to form a first ground connection path 31. A ground harness 30 is connected between a power supply means 28 and a vehicle-body-side member. The ground harness and the control unit are connected by an intermediate harness 29 so as to form a second ground connection path 33. The electric power steering device includes a current component control means 34 that controls so as to allow only an AC current component to flow into the first ground connection path and to allow only a DC current component to flow into the second ground connection path in a load current flowing from the load circuit to the first/second ground connection paths. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electric power steering apparatus that drives and controls an electric motor that transmits a steering assist force to a steering shaft via a reduction mechanism in a reduction gear box, using a control unit including a control board on which a control circuit is mounted.

  As an electric power steering device, a steering column having a steering shaft to which steering torque is transmitted, an electric motor that transmits a steering assist force to the steering shaft via a reduction mechanism in a reduction gear box, and drive control of the electric motor And a control unit including a control board on which a control circuit is mounted, and there is a column type electric power steering device in which the control unit is mounted on the outer periphery of a reduction gear box (for example, Patent Document 1).

  As shown in FIG. 10, the control unit of the device of Patent Document 1 detects a drive circuit 51 including an FET (field effect transistor) that controls driving of the electric motor 50 and torque transmitted to the steering shaft. A control circuit 53 that receives a torque detection value of the torque sensor 52 and outputs a command value to the drive circuit 51 based on the detection value, and a power supply circuit that converts the voltage of the battery 54 into a predetermined voltage and supplies it to the control circuit 53 55. The drive circuit 51 and the power supply circuit 55 are connected to the plus side of the battery 54, and the minus side of the battery 54 is grounded to a vehicle body side member (not shown) via the battery ground harness 55.

Here, FIG. 11 shows a general ground structure in which a load current flows from the load (for example, the drive circuit 51) of the control unit to the ground. In this figure, the first ground connection path is formed by directly attaching the control unit to the outer periphery of the reduction gear box, and the unit side harness 56 is connected between the battery ground harness 55 and the control unit. Two ground connection paths are formed, and a load current flows through the first and second ground connection paths of the two paths from the load side.
JP 2001-196770 A

By the way, in the ground structure of FIG. 11, both the AC component (hereinafter, AC current component) and DC component (hereinafter, DC current component) of the load current flow through the first and second ground connection paths.
However, when an AC current component flows through the second ground connection path (unit-side harness 56), radio noise is radiated to the outside from the unit-side harness 56, or electromagnetic waves easily enter from the outside, so that EMC (electromagnetic compatibility) ) Is likely to decrease. Further, when a DC current component flows from the first ground connection path to the reduction gear box, the reduction gear box may become an antenna.

  Therefore, the present invention has been made paying attention to the unsolved problems of the above-described conventional example, and by controlling the flow of the AC current component and the DC current component to the part requiring the ground, the radio noise is externally transmitted. An object of the present invention is to provide an electric power steering device that can prevent a decrease in EMC (electromagnetic environment compatibility) due to radiation or intrusion of electromagnetic waves from the outside.

  In order to achieve the above object, an electric power steering apparatus according to a first aspect includes a steering column having a steering shaft to which steering torque is transmitted, and a reduction mechanism in a reduction gear box having conductivity on the steering shaft. A control including an electric motor that transmits a steering assist force via a control board mounted with a command value calculation unit that calculates a drive command value of the electric motor, and a power module board mounted with a power module that drives and controls the electric motor An electric power steering apparatus comprising: a unit; and a power supply unit that supplies power to a load circuit such as the power module board of the control unit. The control unit is configured to control the control unit while being electrically connected to the load circuit. A conductive cover covering a substrate or the like, and the control unit is connected to the deceleration gear. A first ground connection path is formed by mounting directly on the outer periphery of the box, a ground harness is connected between the power feeding means and the vehicle body side member, and the ground harness and the control unit are connected by an intermediate harness. A second ground connection path is formed, and among the load currents flowing from the load circuit to the first and second ground connection paths, only an AC current component flows through the first ground connection path, and the second ground connection path Is provided with a current component control means for controlling so that only the DC current component flows.

According to a second aspect of the present invention, in the electric power steering apparatus according to the first aspect, the current component control means blocks the flow of the DC current component and allows only the flow of the AC current component. This is provided in the first ground connection path.
Further, the invention according to claim 3 is the electric power steering according to claim 2, wherein the current component control means is a DC correction circuit such as a capacitor coupling circuit or a differential amplifier provided in the first ground connection path. is there.

  According to the electric power steering apparatus of the first aspect of the present invention, the first ground connection path is formed by directly mounting the control unit on the outer periphery of the reduction gear box, and the ground is provided between the power feeding means and the vehicle body side member. A harness is connected, the ground harness and the control unit are connected by an intermediate harness to form a second ground connection path, and the first ground among the load currents flowing from the load circuit to the first and second ground connection paths Since the current component control means for controlling so that only the AC current component flows in the connection path and only the DC current component flows in the second ground connection path, the AC current component is provided in the second ground connection path (intermediate harness). Does not flow, radio noise radiates to the outside, electromagnetic waves easily enter from the outside, EMC (electromagnetic environment compatibility) It is possible to solve the problem of decrease. Also, since no DC current component flows from the first ground connection path to the reduction gear box, there is no possibility that the reduction gear box becomes an antenna.

Hereinafter, the best mode for carrying out the present invention (hereinafter referred to as an embodiment) will be described in detail with reference to the drawings.
FIG. 1 is a perspective view showing a right-hand drive vehicle according to an embodiment of an electric power steering apparatus according to the present invention, and FIG. 2 is a perspective view showing the embodiment from the left. 3 is a front view of the present embodiment, FIG. 4 is a longitudinal sectional view showing an essential part of the reduction gear box, and FIG. 5 is an external view of the reduction gear box having the external connection terminals of the torque sensor of the first embodiment. FIG. 6 is a perspective view showing the connection relationship between the electric motor and the control unit, FIG. 7 is a front view showing the internal structure of the electric motor, FIG. 8 is an exploded perspective view of the control unit, and FIG. It is a figure which shows the ground structure of this embodiment.

  In FIG. 1, reference numeral 1 denotes a column-type electric power steering device. A reduction gear box 4 is connected to a steering column 3 that rotatably houses a steering shaft 2 connected to a steering wheel (not shown). The reduction gear box 4 is provided with an electric motor 5 whose axial direction is extended in a direction perpendicular to the axial direction of the steering column 3.

  The steering column 3 has a double tube structure of an inner tube 3a and an outer tube 3b. The outer tube 3 b and the reduction gear box 4 of the steering column 3 are attached to the vehicle body side by an upper mounting bracket 6 and a lower mounting bracket 7. The lower mounting bracket 7 is composed of a mounting plate portion 7a attached to a vehicle body side member (not shown) and a pair of support plate portions 7b extending in parallel from the lower surface of the mounting plate portion 7a with a predetermined distance in the left-right direction. Is formed. And the lower end of the support plate part 7b is rotatably connected to the support part 4b integrally formed in the vehicle front side of the reduction gear box 4 via the pivot 7c.

  The upper mounting bracket 6 includes a mounting plate portion 6a attached to a vehicle body side member (not shown) and a pair of support plate portions fixed to the lower end of the mounting plate portion 6a and spaced apart in the left-right (vehicle width) direction. 6b and a tilt mechanism 6c for supporting the outer tube 3b of the steering column 3 formed on the pair of support plate portions 6b. Then, the tilt lever 6g of the tilt mechanism 6c is rotated to release the support state of the outer tube 3b, whereby the tilt position of the steering column 3 can be adjusted up and down around the pivot 7c of the lower mounting bracket 7. .

As shown in FIG. 4, the steering shaft 2 includes an input shaft 2a whose upper end is connected to the steering wheel, and an output shaft 2c covering the torsion bar 2b connected to the lower end of the input shaft 2a via a torsion bar 2b. It consists of
The reduction gear box 4 is formed by die-casting, for example, any one of materials having high thermal conductivity and conductivity such as aluminum, aluminum alloy, magnesium and magnesium alloy. As shown in FIGS. 4 and 5, the reduction gear box 4 includes a worm storage portion 12 that stores a worm 11 connected to an output shaft (not shown) of the electric motor 5, and a lower side of the worm storage portion 12. A worm wheel housing part 14 for housing a worm wheel 13 having a central axis perpendicular to the central axis thereof and meshing with the worm 11, and a torque integrally and coaxially connected to the vehicle rear side of the worm wheel storage part 14 Torque sensor storage portion 16 for storing the sensor 15, motor mounting portion 17 for attaching the electric motor 5 formed on the open end surface of the worm storage portion 12, and a cylindrical shape formed at the vehicle rear end of the torque sensor storage portion 16 A control unit device for mounting a column mounting portion 18 and a control unit 19 formed over part of the worm storage portion 12 and the worm wheel storage portion 14. And a part 20. The vehicle front end portion of the steering column 3 is externally fitted and connected to the column mounting portion 18 of the reduction gear box 4.

  As shown in FIG. 4, the torque sensor 15 magnetically detects a twisted state between the input shaft 2a and the output shaft 2c of the steering shaft 2 and transmits a steering torque transmitted to the steering shaft to a pair of detection coils 15a and 15b. The external connection terminals 15c, 15d and 15e projecting outward in parallel to the direction perpendicular to the central axis of the steering column 3 at the start and end of winding of the pair of detection coils 15a and 15b, respectively. 15f is connected, and the projecting portions of the external connection terminals 15c to 15f are bent in the central portion in parallel with the central axis of the steering column 3 to form an L shape.

  As shown in FIG. 6, the electric motor 5 has connection terminals 5c and 5d formed at positions close to and opposed to the control unit 19 mounted on the control unit mounting portion 20 at a position close to the mounting flange 5b. As shown in FIG. 7, each of the connection terminals 5c and 5d is insulated from each other in a synthetic resin brush support 5f having an armature insertion hole in the center of the bottom, and is connected to two sets of brushes 5g and 5h. The arc-shaped connection terminals 5i and 5j that are individually connected are integrally formed at opposite ends.

  As shown in FIG. 5, the control unit mounting portion 20 formed in the reduction gear box 4 is formed so as to face the vehicle body rear side at the worm storage portion 12 and the upper side of the worm wheel storage portion 14 below the worm storage portion 12. The horizontal mounting surface 20a and the rectangular unit mounting surface 20b extending in the horizontal direction perpendicular to the flat mounting surface 20a formed on the flat mounting surface 20a and the upper surface of the torque sensor storage portion 16 It is formed in an L shape when viewed from the direction.

Here, an opening portion 20 d communicating with the internal space of the torque sensor storage portion 16 that stores the torque sensor 15 is formed in the center portion in the left-right direction of the unit mounting surface 20 b of the control unit mounting portion 20. The external connection terminals 15c to 15f of the torque sensor 15 are provided so as to protrude above the unit mounting surface 20b through the opening 20d.
Also, a frame mounting surface 20c having a narrow width is formed on the rear end surface of the motor mounting portion 17 in parallel to the flat mounting surface 20a and at a position on the rear side of the vehicle body from the flat mounting surface 20a.

As shown in FIG. 8, the control unit 19 mounted on the control unit mounting unit 20 includes a heat radiating plate 21 made of an aluminum alloy having a high thermal conductivity, a power substrate 23, a rectangular frame-shaped synthetic resin frame 24, and the like. The control board 25 and the conductive cover 26 are provided.
The heat radiating plate 21 is directly fixed to the flat mounting surface 20a of the control unit mounting portion 20 via heat radiating grease.

The power board 23 is a discrete component such as an H bridge circuit configured by a power switching element such as an FET (field effect transistor) that controls the driving of the electric motor 5 and a pulse width modulation circuit that drives the power switching element of the H bridge circuit. 23a and 23b are mounted. A synthetic resin frame 24 surrounds the power board 23.
The control board 25 is attached to the front surface of the synthetic resin frame 24 and has through holes 25a to 25d through which the external connection terminals 15c to 15f of the torque sensor 15 are inserted, and a torque detection value from the torque sensor 15 or not shown. A steering assist current command value is calculated based on a vehicle speed detection value from the vehicle speed sensor, and current feedback control is performed based on the steering assist current command value and a detected value of the motor current output to the electric motor 5 to perform the power board 23. By calculating a voltage command value to the pulse width modulation circuit, a discrete component 25e such as a micro control unit (MCU) for controlling a steering assist force generated by the electric motor 5 and its peripheral devices is mounted. The conductive cover 26 covers the power board 23, the synthetic resin frame 24, and the control board 25.

  The synthetic resin frame 24 includes a rectangular frame-shaped frame main body 24a, a mounting plate portion 24b formed on the left end of the frame main body 24a and fixed to the frame mounting surface 20c of the reduction gear box 4, and the mounting plate portion 24b. A terminal block 24c fixed on the top and electrically connected to the connection terminals 5c and 5d of the electric motor 5 and a female connector 45 fixed to the right end of the frame body 24a are provided. The female connector 45 is connected to a power supply connector 45a connected to a battery (not shown) via a power supply male connector 46, and a network such as CAN that exchanges data with control devices in each part of the vehicle body. And a signal connector 45b. The power board 23 and the control board 25 are connected via the connection terminal 22a.

  The control unit 19 configured as described above is mounted on the control unit mounting portion 20 of the reduction gear box 4 and, as shown in FIG. 6, a terminal block 24c fixed to the mounting plate portion 24b of the synthetic resin frame 24. The connection terminals 5c and 5d of the electric motor 5 are electrically connected. As shown in FIGS. 1 to 3, the electrically connected terminal block 24 c and the connection terminals 5 c and 5 d are covered with a synthetic resin terminal cover denoted by reference numeral 27.

Here, as shown in FIG. 9, the positive side of the battery indicated by reference numeral 28 is connected to the power connector 45 a via the harness 29 and the power male connector 46, and is connected to the power board 23 accommodated in the control unit 19. A predetermined voltage is supplied. The negative side of the battery 28 is grounded to a vehicle body side member (not shown) via a battery ground harness 30.
On the other hand, the power board 23 is grounded to the conductive reduction gear box 4 via the conductive heat radiation plate 21. Further, since the control unit 19 is directly mounted on the control unit mounting portion 20 of the reduction gear box 4 via the conductive cover 26, the first ground in which the entire control unit 19 is directly connected to the reduction gear box 4. A connection path 31 is formed. In the present embodiment, the second ground connection path 33 is formed by connecting the unit side harness 32 between the conductive cover 26 of the control unit 19 and the battery ground harness 30. As described above, the load current flows from the power board 23 side to the two ground connection paths of the first and second ground connection paths 31 and 33.

Here, in the present embodiment, a capacitor coupling circuit that allows the flow of the AC current component of the load current in the middle of the first ground connection path 31 formed by directly attaching the control unit 19 to the reduction gear box 4. 34 is arranged.
Next, the operation of the above embodiment will be described.
When an ignition switch (not shown) of the vehicle is turned on and electric power is supplied from the battery 28 to the power board 23 and the control board 25, a steering assist control process is executed by a micro control unit (MCU), and a torque sensor 15 and a vehicle speed sensor (not shown) are executed. A steering assist current command value is calculated based on the detected value. A current feedback process is executed based on the steering assist current command value and the motor current detected by the motor current detection unit to calculate a voltage command value. By supplying this voltage command value to the gate drive circuit of the power board 23 and controlling the H bridge circuit, a motor drive current flows through the electric motor 5 and the electric motor 5 needs to be operated in the forward or reverse direction. Drive to generate force.

For this reason, a steering assist force corresponding to the steering torque of the steering wheel is generated from the electric motor 5, and this steering assist force is transmitted to the output of the steering shaft 2 via the worm 11 and the worm wheel 13, whereby the steering wheel Can be steered with a light steering force.
Here, in the present embodiment, as the ground connection path through which the load current flows from the power board 23 side, the first ground connection path 31 in which the entire control unit 19 is directly connected to the reduction gear box 4 and the control unit 19 A second ground connection path 33 formed by connecting the unit side harness 32 is formed between the conductive cover 26 and the battery ground harness 30, and a capacitor coupling circuit 34 is provided in the middle of the first ground connection path 31. Has been placed.

  With this configuration, the AC current component of the load current flowing from the power board 23 side flows only in the first ground connection path 31, and the DC current component flows only in the second ground connection path 33 (unit-side harness 32). For this reason, since an AC current component does not flow through the unit-side harness 32, problems such as radio noise radiating to the outside or electromagnetic waves easily entering from the outside to reduce EMC (electromagnetic environment compatibility) are solved. be able to. Further, since no DC current component flows from the first ground connection path 31 to the reduction gear box 4, there is no possibility that the reduction gear box 4 becomes an antenna.

Therefore, the present embodiment controls the flow of the AC current component and the DC current component of the ground connection portion to radiate radio noise to the outside, or to reduce EMC (electromagnetic environment compatibility) due to intrusion of electromagnetic waves from the outside. Can be prevented.
In the above embodiment, the capacitor coupling circuit 34 is arranged in the middle of the first ground connection path 31 so that only the AC current component of the load current flows. However, a DC correction circuit such as a differential amplifier is arranged. Thus, only the AC current component may flow.

Further, the case where the electric motor 5, the control unit 19, and the female connector 45 are arranged in a straight line along a line orthogonal to the central axis of the steering column 3 has been described. It may be arranged in a straight line along a line that intersects the central axis of the column 3.
Moreover, in the said embodiment, although the case where a brush motor was applied as the electric motor 5 was demonstrated, it is not limited to this, You may make it apply a brushless motor, In this case, a connection terminal 5c and 5d are connected to the power supply side of the excitation coil of each phase, and, for example, an inverter circuit having a field effect transistor (FET) for driving a brushless motor on the power board 23 and a gate of the field effect transistor of the inverter circuit are pulse width modulated. A gate driving circuit driven by a signal may be mounted.

  Furthermore, in the above-described embodiment, the case where the present invention is applied to a right-hand drive vehicle has been described. However, the present invention is not limited to this, and when applied to a left-hand drive vehicle, the reduction gear box 4 and the electric motor 5 are used. The control unit 19 is arranged symmetrically with respect to the vertical plane passing through the central axis of the steering column 3, that is, the electric motor 5 is arranged on the right side of the control unit 19, and the female connector 45 and the terminal block 24c of the control unit 19 are connected. What is necessary is just to arrange | position on the left side, Furthermore, you may make it arrange | position the electric motor 5 on the vehicle outer side, and arrange | position the female connector 45 and the terminal block 24c on the vehicle inner side.

It is the perspective view shown from the right direction at the time of applying one Embodiment of the electric power steering device which concerns on this invention to a right-hand drive vehicle. It is the perspective view which showed the apparatus of FIG. 1 from the left direction. It is a front view of the apparatus of FIG. It is a longitudinal cross-sectional view which shows the principal part of the reduction gear box which comprises an electric power steering apparatus. It is a perspective view which shows the external appearance of the reduction gear box which comprises an electric power steering device. It is a perspective view which shows the connection relation of the electric motor which comprises an electric power steering apparatus, and a control unit. It is a front view which shows the internal structure of the electric motor which comprises an electric power steering apparatus. It is a disassembled perspective view of a control unit. It is a figure which shows the grand structure of this embodiment. It is a block diagram which shows the circuit of an electric power steering apparatus. It is a figure which shows the general ground structure of an electric power steering device.

Explanation of symbols

  2 ... steering shaft, 2a ... input shaft, 2b ... torsion bar, 2c ... output shaft, 3 ... steering column, 3a ... inner tube, 3b ... outer tube, 4 ... reduction gear box, 4b ... support, 5 ... electric motor 5b ... mounting flange, 5c, 5d ... connection terminal, 5f ... brush support, 5g, 5h ... brush, 5i, 5j ... connection terminal, 6 ... upper mounting bracket, 6a ... mounting plate, 6b ... support plate, 6c ... Tilt mechanism, 6g ... Tilt lever, 7 ... Lower mounting bracket, 7a ... Mounting plate part, 7b ... Supporting plate part, 7c ... Axis, 11 ... Worm, 12 ... Worm storage part, 13 ... Worm wheel, 14 ... Worm Wheel housing part, 15 ... torque sensor, 15a, 15b ... detection coil, 15c-15f ... external connection terminal, 16 ... torque sensor housing part, 17 ... motor mounting part, 18 ... Ram mounting portion, 19 ... control unit, 20 ... control unit mounting portion, 20a ... flat mounting surface, 20b ... unit mounting surface, 20c ... frame mounting surface, 20d ... opening, 21 ... radiation plate, 22a ... connection terminal, DESCRIPTION OF SYMBOLS 23 ... Power board, 23a, 23b ... Discrete components, 24 ... Synthetic resin frame, 24a ... Frame main body, 24b ... Mounting plate part, 24c ... Terminal block, 25 ... Control board, 25a-25d ... Through hole, 25e ... Discrete Components: 26 ... Conductive cover, 27 ... Terminal cover, 28 ... Battery (power supply means), 29 ... Harness, 30 ... Battery ground harness (ground harness), 31 ... First ground connection path, 32 ... Unit side harness (intermediate) Harness), 33 ... second ground connection path, 34 ... capacitor coupling circuit (current component) Control means), 45 ... female connector, 45a ... power connector, 45b ... signal connector, 46 ... male connector for power supply

Claims (3)

A steering column having a steering shaft to which steering torque is transmitted, an electric motor for transmitting a steering assist force via a reduction mechanism in a reduction gear box having conductivity to the steering shaft, and a drive command value for the electric motor Power is supplied to a control unit including a control board mounted with a command value calculation unit for calculating the power, a power module board mounted with a power module for driving and controlling the electric motor, and a load circuit such as the power module board of the control unit An electric power steering apparatus comprising:
The control unit includes a conductive cover that covers the control board and the like while being electrically connected to the load circuit, and forms a first ground connection path by directly mounting the control unit on the outer periphery of the reduction gear box. And
A ground harness is connected between the power supply means and the vehicle body side member, and the ground harness and the control unit are connected by an intermediate harness to form a second ground connection path,
Control is performed so that only an AC current component flows through the first ground connection path and only a DC current component flows through the second ground connection path among load currents flowing from the load circuit to the first and second ground connection paths. An electric power steering apparatus, characterized in that current component control means is provided.   2. The electric power steering according to claim 1, wherein the current component control means is provided in the first ground connection path so as to cut off the flow of the DC current component and allow only the flow of the AC current component. .   3. The electric power steering according to claim 2, wherein the current component control means is a DC correction circuit such as a capacitor coupling circuit or a differential amplifier provided in the first ground connection path.

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