JP3951736B2 - Electric power steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric power steering apparatus, and more particularly to an arrangement structure of a housing and a controller box that house the torque sensor.
[0002]
[Prior art]
The electric power steering apparatus currently in practical use is generally a torque sensor that detects steering torque, an actuator that supplies steering assist force to the steering mechanism by an electric motor, a torque detection circuit, and a control circuit that controls the actuator. And a controller integrated with a motor drive circuit.
[0003]
The torque sensor, for example, connects a torsion bar to a part of the steering shaft, converts the torsion bar's torsion magnitude into a magnetic change, detects this magnetic change with a detection coil, and detects the resulting signal as a torque A configuration in which a signal is processed by a circuit to obtain torque is employed. A detection coil for detecting a change in magnetism is disposed in the vicinity of the steering shaft where the torsion bar is provided, and a torque detection circuit is also disposed in the vicinity of the detection coil, that is, in the vicinity of the steering shaft.
[0004]
In addition, the actuator is configured as a column assist type that transmits the rotational force of the electric motor to the steering shaft, and a pinion assist type that transmits the rotational force of the electric motor to the pinion shaft of the rack and pinion mechanism disposed below the steering shaft. There are several types, such as a so-called configuration and a configuration called a rack assist type that transmits the rotational force of the electric motor to the rack shaft of the rack and pinion mechanism disposed below the steering shaft. Is arranged in the vehicle interior, and pinion assist type and rack assist type actuators are arranged in the engine room.
[0005]
On the other hand, since the outer dimensions of the controller are relatively large, the controller is generally arranged in the engine room or in the vehicle compartment away from the actuator, and the torque detection coil and the controller are generally connected by a wire. .
[0006]
[Problems to be solved by the invention]
Since the electric power steering apparatus is configured to supply power from a battery, it is required to reduce power consumption as much as possible. For this reason, it is required to reduce the power loss due to the resistance of the wiring between the controller that controls and drives the actuator and the electric motor. For this purpose, the length of the wiring between the battery, the controller, and the electric motor is required. It is a problem to shorten as much as possible.
[0007]
In order to cope with such a problem, it is conceivable to arrange the controller in the engine room, that is, outside the vehicle compartment. In this case, the wiring connecting the detection coil and the controller is a sealed structure, and dust is contained inside the controller. In addition, it is necessary to prevent the intrusion of water droplets and a configuration in which the characteristics of the torque detection circuit can be adjusted on the controller side after connection. The present invention aims to solve the various problems described above.
[0008]
[Means for Solving the Problems]
The present invention solves the above-mentioned problems, and the invention according to claim 1 detects the detection by detecting the torque based on the torsion bar by connecting the input shaft and the output shaft arranged coaxially with a torsion bar. In an electric power steering device that controls a steering assist electric motor coupled to an output shaft via a speed reduction mechanism according to the torque that is detected, the torsion of the input shaft , output shaft, torsion bar, and torsion bar is detected. a housing for accommodating the torque detection unit that houses a torque detection circuit for detecting a torque based on the output of the torque sensor, a controller and a control circuit for controlling the electric motor in accordance with the detected torque A controller box, wherein the housing and the controller box have a cylindrical projection on one side and the projection on the other side. Sectional-cylindrical recess for fitting, both an electric power steering apparatus characterized by being removably and tightly coupled.
[0009]
The controller box may include a protrusion having a cylindrical cross section, and the housing may include a recess having a cylindrical cross section that fits into the protrusion.
[0010]
In addition, a seal member may be disposed between a projection having a cylindrical cross section between the housing and the controller box and a recess having a cylindrical cross section fitted to the other projection.
[0011]
And the said controller box can be equipped with the storage space which accommodates the wiring member which connects the said torque detection part and a controller.
[0012]
The wiring member that connects the torque detection unit and the controller includes a connection board that is detachably attached to a connection terminal of the torque detection unit and is electrically connected to the connection terminal, and the connection board is screwed inside the housing. It is good to fix.
[0013]
The screw for fixing the connection board inside the housing has a configuration in which the space between the screw head and the protrusion of the controller box is shorter than the effective screw length of the screw, and the screw does not fall off even if the screw is loose. It is good to do.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0015]
[First Embodiment]
The first embodiment is a pinion assist type electric power steering device. FIG. 1 is a cross-sectional view showing the configuration of the main part of the electric power steering device of the first embodiment, and FIG. FIG. 3 is an enlarged cross-sectional view of a main part showing a modification of the mounting position of the seal member on the mounting surface of the controller box of the electric power steering apparatus shown in FIGS. 1 and 2. FIG. 4 is a perspective view showing a configuration of a torque detector of the torque sensor.
[0016]
1 and 2, reference numerals 1a and 1b denote housings, each of which has a two-part structure of an input shaft side 1a and an output shaft side 1b. Inside the housings 1a and 1b, there are an input shaft 2 rotatably supported by a bearing 6, a torsion bar 3 disposed therein, and an output shaft 4 connected to the input shaft 2 via the torsion bar 3. 7a and 7b are rotatably supported.
[0017]
The input shaft 2, the torsion bar 3, and the output shaft 4 are arranged coaxially. The input shaft 2 and the torsion bar 3 are fixedly coupled by a pin 2a, and the torsion bar 3 and the output shaft 4 are formed by a spline SP formed therebetween. They are coupled together in the rotational direction and movably in the axial direction. Further, a steering shaft (not shown) and a steering wheel are integrally attached to the left end side of the input shaft 2 in FIG.
[0018]
A pinion shaft 4 a is formed integrally with the output shaft 4, and the teeth of the pinion shaft 4 a mesh with the rack teeth of the rack shaft 8 to constitute a known rack and pinion type steering mechanism.
[0019]
A worm wheel 9 that is coaxial with and rotates integrally with the output shaft 4 is fixed to the output shaft 4 and meshes with a worm 10 that is driven by a steering assisting electric motor (not shown). The rotational force of the electric motor is transmitted to the output shaft 4 via the worm 10 and the worm wheel 9, and a steering assist torque in an arbitrary direction is applied to the output shaft 4 by appropriately switching the rotation direction of the electric motor.
[0020]
Next, the torque sensor will be briefly described. Since the configuration and operation are not directly related to the gist of the present invention, detailed description thereof is omitted here, but the details are disclosed in Japanese Patent Laid-Open No. 10-38715.
[0021]
Hereinafter, the configuration of the torque detector of the torque sensor will be described with reference to FIGS. 2 and 4. The torque detector includes a sensor shaft portion 11 formed on the input shaft 2, detection coils 13 and 14 disposed inside the housing 1a, and a cylinder disposed between the sensor shaft portion 11 and the detection coils 13 and 14. The member 12 is configured.
[0022]
As apparent from FIG. 2, a sensor shaft portion 11 made of a magnetic material is formed on the outer peripheral surface near the left end in FIG. 2 of the input shaft 2, and on the surface of the sensor shaft portion 11, A plurality of ridges 11a extending in the axial direction are formed at equal intervals along the circumferential direction, and groove portions 11b wider than the width of the ridges are formed between the ridges.
[0023]
Further, on the outside of the sensor shaft portion 11, a cylindrical member 12 made of a conductive and non-magnetic material, for example, aluminum, which is close to the sensor shaft portion 11, is arranged coaxially with the sensor shaft portion 11, The extension 12 e of the cylindrical member 12 is fixed to the outside of the end of the output shaft 4.
[0024]
The cylindrical member 12 includes a first window row 12a composed of a plurality of rectangular windows arranged at equal intervals in the circumferential direction at a position facing the protrusions 11a on the surface of the sensor shaft portion 11, and A second window row 12b comprising a plurality of rectangular windows having the same shape as the window and having different phases in the circumferential direction is provided at a position shifted in the axial direction from the first window row.
[0025]
The outer periphery of the cylindrical member 12 is surrounded by a yoke 15 around which detection coils 13 and 14 of the same standard are wound. The detection coils 13 and 14 are arranged coaxially with the cylindrical member 12, and the detection coil 13 surrounds the first window row 12a portion, and the detection coil 14 surrounds the second window row portion 12b. The yoke 15 is fixed inside the housing 1a, and the output lines of the detection coils 13 and 14 are connected to the terminals 13a and 14a.
[0026]
When a rotational force is applied to the input shaft 2 by operating the steering wheel, the rotational force is transmitted to the output shaft 4 via the torsion bar 3. At this time, a frictional force between the steering wheel and the road surface or a frictional force due to the meshing of the gear of the steering mechanism coupled to the output shaft 4 acts on the output shaft 4. A twist occurs in the torsion bar 3 that joins between the projections 11a and 11b on the surface of the sensor shaft portion 11 on the input shaft 2 side and the first window row 12a of the cylindrical member 12 on the output shaft 4 side. , Relative rotation occurs between the second window row 12b and the magnetic flux generated in the sensor shaft portion 11 increases or decreases. As the magnetic flux increases or decreases, one of the inductances of the detection coils 13 and 14 increases and the other decreases. To do. Since the torsion angle of the torsion bar 3 changes in proportion to the magnitude of the torque and the amount of increase / decrease in the inductance of the detection coils 13 and 14 changes, the magnitude of the torque is detected from the difference in inductance between the detection coils 13 and 14. be able to.
[0027]
FIG. 5 is a circuit block diagram of the controller 30. The controller 30 includes a torque detection circuit 22, a control circuit 25, a motor drive circuit 26, and the like.
[0028]
The torque detection circuit 22 includes a bridge circuit including a first arm in which the detection coil 13 and the resistor R1 are connected in series, and a second arm in which the detection coil 14 and the resistor R2 are connected in series. The
[0029]
The detection coils 13 and 14 of the first arm and the second arm are connected to a power source VDD that outputs an alternating voltage of a predetermined frequency via a PNP transistor Tr, and the resistance R1 of the first arm and the second arm. And the other end of R2 is grounded. Reference numeral 21 denotes a diode that allows current only when an electromotive force in the reverse direction is generated in the detection coils 13 and 14.
[0030]
It is assumed that the values of the resistors R1 and R2 are adjusted in advance so that the voltages appearing at both ends of the detection coils 13 and 14 are equal when no torque is applied.
[0031]
The voltage signals appearing at both ends of the detection coil 13 and the detection coil 14 are converted into a difference signal between the two detection coils by the differential amplifier 23, amplified, and output to the control circuit 25 through the sample hold circuit 24.
[0032]
The control circuit 25 calculates the direction and magnitude of the relative rotational displacement between the input shaft 2 and the cylindrical member 12, that is, the output shaft 4, based on the difference signal between the two detection coils supplied from the sample hold circuit 24. The direction and magnitude of the steering torque are obtained by multiplying by a predetermined constant, the magnitude and direction of the current supplied to the steering assist electric motor are determined, and the motor drive circuit 26 is controlled. The motor drive circuit 26 uses an H bridge circuit configured using four known field effect transistors (FETs), and controls the magnitude of the current supplied to the electric motor by controlling the duty ratio of the FETs. Changed and executed.
[0033]
Although the description has been given here assuming that the motor drive circuit 26 is incorporated in the controller 30, the motor drive circuit 26 may be separated from the controller 30 and integrated into the steering assisting electric motor.
[0034]
Next, the arrangement of the controller 30 and its mounting structure will be described with reference to FIGS. A controller box 31 that houses the controller 30 is attached to the outside of the housing 1a. A cylindrical space 1d is formed on the outside of the housing 1a in the vicinity of where the detection coils 13 and 14 are arranged, and a cylindrical protrusion 31a that fits into the space 1d is formed in the controller box 31. The protrusion 31 a is fitted into the cylindrical space 1 d and fixed with the mounting bolt 32.
[0035]
If sealing is performed by interposing a seal member 33 such as an O-ring on the fitting surface between the space 1d and the protrusion 31a, an airtight seal can be achieved, and dust and water droplets can be effectively prevented from entering.
[0036]
1 and 2, the connection terminals 13a and 14a of the detection coils 13 and 14 are exposed in a cylindrical space 1d formed in the housing 1a, and the controller 30 disposed inside the controller box 31. A flexible lead wire 28 is connected to the terminals on the substrate. When connecting the lead wire 28, the controller box 31 is removed from the housing 1a, and after adjusting the characteristics of the torque detection circuit 22 by connecting the lead wire 28, the lead wire 28 is folded to form a cylindrical shape of the controller box 31. It is assumed that it is housed in a recess 31e provided in the protrusion 31a.
[0037]
According to this configuration, when the electric motor is attached to the housing 1b, the length of the wiring between the controller and the electric motor can be shortened, and the torque detection circuit and the controller can be sealed. In addition, it is necessary to prevent the intrusion of water droplets and water, and after connecting the torque detection circuit and the controller, the characteristics of the torque detection circuit can be adjusted on the controller side.
[0038]
FIG. 3 is an enlarged cross-sectional view of a main part showing a modification of the mounting position of the seal member on the mounting surface of the controller box of the electric power steering apparatus shown in FIGS. 1 and 2. Since it is substantially the same as the structure shown in FIG.1 and FIG.2, and only the attachment position of a sealing member is different, the same code | symbol is attached | subjected to the same member and description is abbreviate | omitted.
[0039]
In the configuration shown in FIGS. 1 and 2, a groove for fitting the seal member 33 is provided on the housing 1 a side. However, in the configuration shown in FIG. 3, the seal member 33 is fitted on the protrusion 31 a of the controller box 31. Grooves are provided. With this configuration, the groove for fitting the seal member can be easily processed.
[0040]
[Second Embodiment]
The second embodiment has a configuration similar to that of the first embodiment described above, except that the structure for attaching the lead wire on the controller side to the connection terminal of the detection coil is different. Portions common to the configuration of the embodiment are given the same reference numerals, description thereof will be omitted, and only differences will be described.
[0041]
FIG. 6 is an enlarged cross-sectional view of a main part of the electric power steering apparatus according to the second embodiment. The connection terminals 13a and 14a of the detection coil are connected by a coupler (wiring connection tool) 28a provided at the tip of the lead wire 28 on the controller side. According to this configuration, the detection coil and the controller can be easily connected.
[0042]
[Third Embodiment]
The third embodiment has a configuration similar to the configuration of the first embodiment described above, and is configured to connect to the tip of a lead wire on the controller side connected to the connection terminal of the detection coil via a connection board. Since only the points are different, portions common to the configuration of the first embodiment are denoted by the same reference numerals, description thereof is omitted, and only differences are described.
[0043]
FIG. 7 is an enlarged cross-sectional view of the main part of the electric power steering apparatus according to the third embodiment, showing a state in which the controller box and the connection board are attached to the housing, and FIG. 8 is a view in which the controller box is removed from the housing. It is sectional drawing which shows a state.
[0044]
In the third embodiment, a connection board 29 is connected to the tip of the lead wire 28 on the controller side, and the contact piece of the connection board 29 is inserted into the connection terminals 13a and 14a of the detection coil, This is a configuration for connecting to the controller.
[0045]
First, as shown in FIG. 8, with the controller box 31 removed from the housing 1a, the contact piece of the connection board 29 is inserted into the connection terminals 13a and 14a of the detection coil, and the connection board 29 is fixed to the housing 1a with the fixing screw 29a. Secure to. At this time, the space between the screw head of the fixing screw 29a and the protrusion of the controller box 31 is made shorter than the effective screw length of the fixing screw 29a. Thereby, even if the fixing screw 29a is loosened, it does not fall off.
[0046]
The member 29b on the connection board 29 is a characteristic adjustment member for the torque detection circuit, and is for adjusting the characteristics after the connection board 29 is fixed to the housing 1a.
[0047]
Next, as shown in FIG. 7, the cylindrical protrusion 31 a of the controller box 31 is fitted into the cylindrical space 1 d formed in the housing 1 a and fixed by the mounting bolt 32.
[0048]
Also with this configuration, the detection coil and the controller can be easily connected, and the characteristics of the torque detection circuit can be easily adjusted by removing the controller box 31.
[0049]
[Fourth Embodiment]
The fourth embodiment is a column assist type electric power steering apparatus. FIG. 9 is a cross-sectional view showing the configuration of the main part of the electric power steering apparatus according to the fourth embodiment, which includes a torque detection unit arranged in the steering column, a worm wheel arranged under the steering shaft, and a worm. The arrangement | positioning of the worm gear mechanism and controller which become is shown.
[0050]
In FIG. 9, reference numerals 41a and 41b denote housings, which have a two-part structure of an input shaft side 41a and an output shaft side 41b. A steering shaft housing 42 has one end fixed to the housing 41a.
[0051]
An input shaft 45 rotatably supported by a bearing 43 is disposed inside the steering shaft housing 42, and a steering wheel is integrally attached to the input shaft 45, although not shown at the right end in FIG. ing.
[0052]
Further, one end of the torsion bar 46 is coupled to the left side of the input shaft 45 in FIG. 8, and the output shaft 47 is fixedly coupled to the other end of the torsion bar 46 by a pin 47a so as to surround the torsion bar 46. The output shaft 47 is rotatably supported by bearings 48a and 48b. The left side of the output shaft 4 in FIG. 9 is connected to a known rack and pinion type steering mechanism via a universal joint, although not shown.
[0053]
A worm wheel 50 that is coaxial with and rotates integrally with the output shaft 47 is fixed to the output shaft 47 and meshes with a worm 51 that is driven by an electric motor for steering assistance (not shown). The rotational force of the electric motor is transmitted to the output shaft 47 via the worm 51 and the worm wheel 50, and a steering assist torque in an arbitrary direction is applied to the output shaft 47 by appropriately switching the rotation direction of the electric motor.
[0054]
Since the torque detection unit is the same as that of the third embodiment described above, the same reference numerals are assigned to the same members and the description thereof is omitted. Even in this configuration, the housing 41a has a cylindrical shape. A space 41d is formed, and the cylindrical protrusion 31a of the controller box 31 is fitted into the cylindrical space 41d and fixed by the mounting bolt 32.
[0055]
This configuration is obtained by applying the connection configuration of the torque detection unit and the controller of the third embodiment to a column assist type electric power steering device. Similarly to the third embodiment, the detection coil and The controller can be easily connected, and the controller box 31 can be removed to easily adjust the characteristics of the torque detection circuit.
[0056]
FIG. 10 is a diagram for explaining the state of the harness (wiring) WR between the controller box 31, the electric motor MT, and the battery BT in the first to third embodiments. The controller box 31 is attached to the provided housing 1a, and the electric motor MT is attached to the housing 1b that is paired with the housing 1a, so that the harness (wiring) WR from the battery BT is connected to the controller box 31. By connecting and wiring between the controller box 31 and the electric motor MT, all wiring is completed.
[0057]
In the first to third embodiments, since the controller box 31 is in the engine room outside the vehicle compartment, the length of the harness (wiring) WR from the battery BT can be shortened.
[0058]
Further, even in the column assist type electric power steering apparatus of the fourth embodiment, the controller box 31 is attached to the housing 1a provided with the torque detector, and the housing 1a portion is provided in the engine room outside the vehicle compartment. When arranged, the length of the harness (wiring) WR from the battery BT can be similarly reduced.
[0059]
【The invention's effect】
As described above, the present invention provides an electric power steering apparatus that controls a steering assisting electric motor coupled to an output shaft via a speed reduction mechanism in accordance with detected torque, and includes an input shaft, an output shaft, and a torsion bar. and a housing for accommodating a torque detector for detecting a magnitude of torsion of the torsion bar, a torque detection circuit for detecting a torque based on the output of the torque detector for detecting the magnitude of the torsion of the torsion bar, detection A controller box that houses a controller that includes a control circuit that controls the electric motor in accordance with torque, and a cylindrical section that fits into a projection having a cylindrical section provided on one side and the projection provided on the other side Since the concave and concave portions are detachably and tightly coupled, the controller and the electric motor are placed close to each other and the length of the wiring Can be shortened, it is possible to reduce the power loss due to the wiring resistance.
[0060]
In addition, since the wiring that connects the detection coil and the controller is housed in a sealed structure, dust and water droplets can be prevented from entering the controller, and the housing and controller box can be attached and detached. After the coil and the controller are connected by wiring, it is possible to adjust the characteristics of the torque detection circuit on the controller side before sealing, thereby providing excellent operational effects.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating a configuration of a main part of an electric power steering apparatus according to a first embodiment.
FIG. 2 is an enlarged cross-sectional view of a main part of the electric power steering apparatus shown in FIG.
FIG. 3 is an enlarged cross-sectional view of a main part showing a modification of the mounting position of the seal member on the mounting surface of the controller box of the electric power steering apparatus.
FIG. 4 is a perspective view showing a configuration of a torque detector of the torque sensor.
FIG. 5 is a circuit block diagram of a controller.
FIG. 6 is an enlarged cross-sectional view of a main part of the electric power steering apparatus according to the second embodiment.
FIG. 7 is an enlarged cross-sectional view of a main part of an electric power steering apparatus according to a third embodiment.
8 is an enlarged cross-sectional view of a main part showing a state in which a controller box is removed in the electric power steering apparatus shown in FIG. 7;
FIG. 9 is an enlarged cross-sectional view of a main part of an electric power steering apparatus according to a fourth embodiment.
FIG. 10 is a diagram illustrating a state of a harness (wiring) between a controller box, an electric motor, and a battery in the first to third embodiments.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1a, 1b Housing 1d Cylindrical space part 2 Input shaft 3 Torsion bar 4 Output shaft 4a Pinion shaft 8 Rack shaft 9 Worm 10 Worm wheel 11 Sensor shaft part 12 Cylindrical member 13, 14 Detection coil 15 Yoke 22 Torque detection circuit 23 Differential Amplifier 24 Sample hold circuit 25 Control circuit 26 Motor drive circuit 28 Lead wire (wiring)
28a coupler (wiring connector)
29 Connection board 29a Fixing screw 30 Controller 31 Controller box 31a Cylindrical protrusion 31e Recess 32 Mounting bolt 33 Seal member 33

Claims (6)

Steering assistance in which the input shaft and the output shaft arranged on the same axis are coupled by a torsion bar, torque is detected based on torsion of the torsion bar, and coupled to the output shaft via a speed reduction mechanism according to the detected torque. In the electric power steering device for controlling the electric motor for
A housing that houses an input shaft , an output shaft, a torsion bar, and a torque detector that detects a torsional magnitude of the torsion bar ;
A controller box that houses a controller including a torque detection circuit that detects torque based on an output of the torque detection unit , and a control circuit that controls the electric motor according to the detected torque;
The housing and the controller box are provided with a protrusion having a cylindrical cross section on one side and a recess having a cylindrical cross section fitting on the other, and the two are detachably and tightly coupled. An electric power steering device.   2. The electric power steering apparatus according to claim 1, wherein the controller box includes a protruding portion having a cylindrical cross section, and the housing includes a recessed portion having a cylindrical cross section that fits into the protruding portion. A seal member is disposed between a projection having a cylindrical cross section between the housing and the controller box and a recess having a cylindrical cross section fitted to the other projection. the electric power steering apparatus according to claim 1. 4. The electric power steering apparatus according to claim 1, wherein the controller box includes a storage space for storing a wiring member that connects the torque detection unit and the controller. 5. The wiring member that connects the torque detection unit and the controller includes a connection board that is detachably attached to a connection terminal of the torque detection unit and that is electrically connected to the connection terminal, and the connection board is fixed inside the housing with a screw. The electric power steering device according to claim 1, wherein the electric power steering device is a power steering device.   The screw for fixing the connection board inside the housing has a configuration in which the space between the screw head and the protrusion of the controller box is shorter than the effective screw length of the screw, and the screw does not fall off even when the screw is loosened. The electric power steering apparatus according to claim 5, wherein the electric power steering apparatus is provided.

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