JP3772986B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering apparatus that assists the steering force of a steering.

  Currently, an electric power steering device (hereinafter abbreviated as EPS) that assists the steering force of the steering by the rotational output of the motor has been put into practical use. The EPS controls a motor for assisting a steering force, a torque sensor for detecting a steering torque, an electromagnetic clutch for separating the motor and the steering mechanism when an abnormality occurs, and a motor current based on a detection value of the torque sensor, a vehicle speed signal, and the like. It consists of a control circuit and the like. Since the EPS is attached to the lower position of the engine room of the vehicle, the EPS may be submerged depending on the traveling speed, or muddy water, snow or the like may be attached even at a slight water depth, and is disposed in a poor environment. For this reason, the control circuit is generally mounted in a vehicle compartment with good environment.

  However, the conventional electric power steering apparatus has the following problems.

  (1) The control circuit needs to connect many signal lines to a motor, an electromagnetic clutch, or a rotation angle sensor that detects a steering angle. For this reason, since the number of connectors for connecting these signal lines increases, the size of the control circuit increases.

  Further, the increase in the number of connectors for connection tends to cause contact failure of the connector.

  (2) In order to mount the control circuit in the vehicle interior, it is necessary to penetrate the signal line through a partition wall that partitions the vehicle interior and the engine room, so that the man-hour required for connection increases. In particular, the wiring of the motor current that flows a large current needs to be thick in order to reduce the wiring resistance, and is difficult to handle.

  (3) In EPS, since the motor current is controlled by the switching operation of the transistor, radio noise is generated along with the switching operation.

  The present invention has been made based on the above circumstances, and an object thereof is to provide a highly reliable electric power steering apparatus with reduced radio wave noise and high reliability while miniaturizing the apparatus and simplifying wiring. is there.

The present invention employs the following configuration in order to achieve the above object. According to a first aspect of the present invention, the control circuit includes: an output shaft coupled to a steering mechanism of a vehicle; a motor that assists the steering mechanism via the output shaft; and a control circuit that controls a current flowing through the motor. Is integrated with the motor and accommodated in a motor housing, and the control circuit is disposed on the side of the motor in the motor housing, and the motor housing includes components such as the motor and the control circuit. And a bottomed cylindrical motor case that covers each of the components and is airtightly combined with the end frame, and a connector for external connection between the end frame and the motor case. Is taken out in an airtight manner. Further, the motor has a commutator through which a current flows through a brush on one end side of a shaft constituting a rotating shaft, the commutator is arranged facing the end frame side, and the output shaft is arranged coaxially with the shaft. The drive shaft is connected to the shaft on the end frame side with respect to the motor.

  According to a second aspect of the present invention, in the electric power steering apparatus according to the first aspect, the control circuit is integrally provided with a connector for external connection.

  According to a third aspect of the present invention, in any one of the electric power steering apparatuses according to the first or second aspect, a steering angle detecting unit that detects a steering angle and outputs the detected steering angle to the control circuit is provided. The circuit is integrated with the motor and housed in the motor housing.

  According to a fourth aspect of the present invention, in the electric power steering apparatus according to the third aspect of the present invention, the electric power steering apparatus further includes a protection unit that receives a drive signal output from the control circuit and disconnects the connection state between the motor and the output shaft. Is integrated with the motor together with the control circuit and the steering angle detecting means, and is housed in the motor housing.

  According to a fifth aspect of the present invention, in the electric power steering apparatus according to the fourth aspect, the protection means includes a driving side rotating body that rotates integrally with the motor and a driven side rotating body that rotates integrally with the output shaft. And an electromagnetic clutch that separates the drive-side rotator and the driven-side rotator when receiving the drive signal, the steering angle detecting means comprising: a magnetic body provided on the driven-side rotator; and the driven side It comprises magnetic detection means arranged on the outer periphery of the rotating body so as to face the magnetic body and detecting a change in magnetic flux accompanying rotation of the driven-side rotating body.

  According to a sixth aspect of the present invention, in the electric power steering apparatus according to the fifth aspect, the magnetic detection means is assembled on a substrate of the control circuit.

According to claim 7, in any of the electric power steering system according to claim 1, wherein the control circuit includes a battery current accompanying the switching operation of the four switching elements and the switching elements constituting the H-bridge circuit It has the capacitor | condenser which smoothes, and arrange | positions in the side of a motor in the state parallel to the field device of a motor.

According to claim 8, in any of the electric power steering system according to claim 7, wherein the brush is characterized in that it is arranged on the opposite side to the control circuit about said commutator.

According to a ninth aspect of the present invention , in the electric power steering apparatus according to any one of the first to eighth aspects , the control circuit is provided with a connection terminal on an insulating member integrated with the connector, and a motor current is connected to the connection terminal. The switching element for controlling the above is connected by a bonding wire, and the pigtail of the brush is connected.

A tenth aspect of the present invention is the electric power steering apparatus according to any one of the first to ninth aspects, wherein the motor case is made of a magnetic material.

According to an eleventh aspect of the present invention , in any one of the electric power steering apparatuses according to the first to tenth aspects, the motor is a brushless motor that controls a rotational speed by an output frequency of an inverter.

According to a twelfth aspect of the present invention , an output shaft connected to a steering mechanism of a vehicle, a motor that assists the steering mechanism via the output shaft, and a control circuit that controls a current flowing to the motor are provided, and the control circuit Is an electric power steering apparatus that is integrated with the motor and accommodated in a motor housing, the motor housing including an end frame to which the components such as the motor and the control circuit are assembled, and the components. A bottomed cylindrical motor case that covers and is airtightly combined with the end frame, and a connector for external connection is airtightly taken out between the end frame and the motor case. A commutator that allows current to flow through a brush is provided at one end of the shaft, and this commutator is connected to the end frame. The output shaft is arranged coaxially with the shaft, and is drivingly connected to the shaft on the end frame side with respect to the motor, and the control circuit is integrally provided with the connector. And being arranged on the side of the motor in the motor housing.

(Operation and effect of the invention)
(Claim 1) Since the control circuit is integrated with the motor and accommodated in the motor housing, the control circuit and the motor can be connected inside the motor housing. Thus, the system can be downsized by integrating the control circuit and the motor. Further, by internally connecting the control circuit and the motor, an external connection connector provided in the control circuit becomes unnecessary, and the number of harnesses can be reduced. This can reduce the probability of signal transmission failure due to poor connector contact, harness biting, or the like in the entire system, and can thus greatly improve reliability.

Furthermore, by arranging the control circuit on the side of the motor, the motor wiring connecting the control circuit and the motor can be shortened. By assembling each component such as a motor and control circuit to the end frame, and then tightly assembling a cup-shaped (bottomed cylindrical) motor case that covers each component to the end frame, the entire motor housing is waterproofed. It can be a structure. The external connection connector does not lose its waterproof property by being airtightly taken out from between the end frame and the motor case. Since the motor is drivingly connected to the output shaft on the end frame side, in a system including a protection unit between the motor and the output shaft, the protection unit is assembled on the end frame side. Accordingly, in the motor, since the commutator provided on one end side of the shaft is arranged facing the end frame side, the brush that needs to be connected to the control circuit can be arranged close to the protection means. Thereby, the internal wiring connected to the control circuit can be simplified.

  (Claim 2) By arranging the control circuit on the side of the motor, a connector can be provided integrally with the control circuit, and the connector can be taken out between the end frame and the motor case.

  (Claim 3) In the system having the steering angle detecting means for detecting the steering angle, the control circuit and the steering angle detecting means are integrated with the motor and housed in the motor housing in addition to the control circuit. Can also be connected inside the motor housing.

  (Claim 4) In a system having protection means for separating a motor and an output shaft upon receipt of a drive signal from a control circuit, the protection means as well as the control circuit and the steering angle detection means are integrated with the motor and accommodated in the motor housing. Thus, the connection between the control circuit and the protection means can be performed inside the motor housing.

  (Claims 5 and 6) The steering angle detection means magnetically detects a change in magnetic flux generated by providing a magnetic body on the driven-side rotator of the electromagnetic clutch as a protection means and rotating the magnetic body together with the driven-side rotator. With the configuration in which the detection is performed by the means, it is not necessary to separately provide a rotating body as the steering angle detection means. Further, by directly assembling the magnetic detection means on the substrate of the control circuit, wiring with the magnetic detection means becomes unnecessary. As a result, it is possible to greatly reduce the number of components.

( 7 ) The control circuit is arranged on the side of the motor in parallel with the field device of the motor, whereby the four switching elements constituting the H-bridge circuit and the battery accompanying the switching operation of each switching element. Since the capacitor for smoothing the current can be arranged near the end frame, the heat generated by the switching operation of each switching element and the heat generated from the capacitor can be efficiently transmitted to the end frame.

(Claim 8 ) By arranging the brush on the side opposite to the control circuit arranged on the side of the motor with the commutator as the center, the wiring (pigtail) to the brush can have a degree of freedom. That is, when the brush is arranged on the control circuit side, the wiring connecting the control circuit and the brush is shortened, so that the brush is stressed, so that the mobility of the brush is deteriorated. Therefore, the mobility of the brush can be ensured by arranging the brush on the side opposite to the control circuit and providing the wiring with a degree of freedom.

(Claim 9 ) Generally, a copper mesh wire is used for the pigtail of the brush to lower the resistance. On the other hand, in the control circuit, the switching element is connected by a bonding wire. As described above, since the connection method is different between the brush and the switching element, a connection terminal is provided on the insulating member of the control circuit, and the bonding wire from the switching element is connected to the connection terminal and the pigtail of the brush is connected. The structure.

(Claim 10 ) By manufacturing the motor case from a magnetic material, radio noise generated by the switching operation of the switching element can be reduced by the electromagnetic shielding effect of the motor case.

(Claim 11 ) A brushless motor that controls the rotation speed according to the output frequency of the inverter may be employed.

(Claim 12 ) Since the control circuit is integrated with the motor and accommodated in the motor housing, the control circuit and the motor can be connected inside the motor housing. Thus, the system can be downsized by integrating the control circuit and the motor. Further, by internally connecting the control circuit and the motor, an external connection connector provided in the control circuit becomes unnecessary, and the number of harnesses can be reduced. This can reduce the probability of signal transmission failure due to poor connector contact, harness biting, or the like in the entire system, and can thus greatly improve reliability.

  In addition, the motor housing and the control circuit are assembled to the end frame, and a cup-shaped (bottomed cylindrical) motor case that covers each component is assembled to the end frame in an airtight manner. Can have a waterproof structure. The external connection connector does not lose its waterproof property by being airtightly taken out from between the end frame and the motor case.

  Furthermore, since the motor is drivingly connected to the output shaft on the end frame side, in a system including a protection unit between the motor and the output shaft, the protection unit is assembled on the end frame side. Accordingly, in the motor, since the commutator provided on one end side of the shaft is arranged facing the end frame side, the brush that needs to be connected to the control circuit can be arranged close to the protection means. Thereby, the internal wiring connected to the control circuit can be simplified.

  Further, by arranging the control circuit on the side of the motor, a connector can be provided integrally with the control circuit, and the connector can be taken out between the end frame and the motor case. Also, the motor wiring connecting the control circuit and the motor can be shortened.

  Next, an embodiment of the electric power steering apparatus (EPS) of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing the internal structure of the EPS, and FIG. 3 is a block diagram showing an EPS drive system. As shown in FIG. 3, the EPS 1 includes an output shaft 4 connected to the steering mechanism 3 via the speed reducer 2, a motor 5 that generates a rotational output, and an electromagnetic clutch that transmits the rotational output of the motor 5 to the output shaft 4. 6, a steering angle sensor 7 for detecting a steering angle (a rotation angle of the output shaft 4), a control circuit 9 for controlling a motor current according to the steering force and the vehicle speed of the steering 8, and the like. The components (the motor 5, the electromagnetic clutch 6, the steering angle sensor 7, and the control circuit 9) are integrated and accommodated in one motor housing 10 (see FIG. 1).

(Description of motor housing 10)
As shown in FIG. 1, the motor housing 10 includes an end frame 11 to which the above-described components are assembled, and a motor case 12 that covers the components and is air-tightly assembled to the end frame 11. The end frame 11 is made of a material having good thermal conductivity (for example, aluminum), is in close contact with the end surface of the rack housing 13 that houses the steering mechanism 3, and is fixed to the rack housing 13 by tightening bolts 14. The motor case 12 is provided with a magnetic material (for example, iron), has a cylindrical shape with one end side (upper end side in FIG. 1) closed, that is, a cup shape, and a fixing portion 12a provided on the outer periphery of the opening peripheral portion. The bolt 15 is fastened to the end frame 11. An outlet 17 (see FIG. 2) for taking out the connector 16 of the control circuit 9 is formed between the end of the motor case 12 and the end frame 11.

(Description of motor 5)
The motor 5 includes a field device (for example, a cylindrical magnet shown in FIG. 1) 18, an armature 19 that rotates on the inner periphery of the magnet 18, a commutator 21 provided on one end side of the shaft 20, and an outer peripheral surface of the commutator 21. The brush 22 (see FIGS. 2 and 8) that is in sliding contact with the brush 22, the brush holder 23 that holds the brush 22, and the like, the armature 19 is assembled in an upright posture (state shown in FIG. 1) with respect to the end frame 11. It is attached. As shown in FIG. 1, the armature 19 has one end side of the shaft 20, that is, the commutator 21 side rotatably supported by the housing 25 of the electromagnetic clutch 6 via the bearing 24, and the other end side via the bearing 26. The motor case 12 is rotatably supported by a bearing portion 12c provided on the bottom surface.

(Description of electromagnetic clutch 6)
The electromagnetic clutch 6 is provided between the motor 5 and the output shaft 4. The coil 27 is energized and controlled via the control circuit 9. The housing 25 holds the coil 27 and is fixed to the end frame 11. 20 is connected to one end of the rotor 20 and rotates integrally with the shaft 20 (drive-side rotating body of the present invention), and is connected to the output shaft 4 and is rotated integrally with the output shaft 4 (driven side of the present invention). Rotating body).

  In the electromagnetic clutch 6, when the coil 27 is energized via the control circuit 9, the armature 29 is attracted to the magnetized rotor 28 by receiving the magnetic force of the coil 27, and the armature 29 rotates integrally with the rotor 28. Thus, the rotational output of the motor 5 is transmitted to the output shaft 4 through the rotor 28 and the armature 29. However, when the EPS 1 is operating abnormally, the connection between the shaft 20 and the output shaft 4 is stopped by stopping the energization of the coil 27 via the control circuit 9 so that the rotation output of the motor 5 is not transmitted to the output shaft 4. The state is disconnected.

(Description of the steering angle sensor 7)
As shown in FIG. 2 (enlarged sectional view in the vicinity of the end frame 11 shown in FIG. 1), the steering angle sensor 7 includes a magnetic body 30 (for example, a magnet) fixed to the outer peripheral surface of the armature 29 of the electromagnetic clutch 6, and an armature. The magnetic detection means 31 (for example, Hall IC) disposed on the outer periphery of the magnetic body 30 so as to face the magnetic body 30. The magnetic detection means detects a change in magnetic flux generated by the rotation of the magnetic body 30 as the armature 29 rotates. Detect at 31. The magnetic detection means 31 is directly soldered on the substrate 9a (see FIG. 6) of the control circuit 9.

(Description of control circuit 9)
The control circuit 9 is integrally provided with a connector 16 for external connection, and is disposed on the side of the motor 5 in the motor housing 10. As shown in FIGS. 1 and 2, the connector 16 is taken out airtightly from a take-out port 17 formed between the motor case 12 and the end frame 11 via a seal member 32.

  As shown in FIG. 4, the control circuit 9 includes four switching elements 33 (33a to 33d) constituting an H bridge circuit, a torque sensor 34 for detecting a steering torque, and inputs from a vehicle speed sensor 35 for detecting a vehicle speed. From the I / F circuit 36 for digitally converting the signal, the microcomputer (CPU) 37 for setting the motor current necessary for torque assist according to the steering force and the vehicle speed converted by the I / F circuit 36, An I / F circuit 38 that converts an output digital signal into an analog value, a current detector 39 that detects a current flowing through the motor 5, an analog current command value converted by the I / F circuit 38 and a current detector 39 A current control unit 40 for creating a duty signal of each switching element 33 based on the current value thus obtained. The generated duty signal and the direction to be torque-assisted determined by the microcomputer 37 are input, and the gate drive circuit 41 for driving each switching element 33 and the battery current accompanying the switching operation of each switching element 33 are smoothed. It is composed of a capacitor 42 and the like.

  In addition, the control circuit 9 is provided with a temperature sensor (not shown) in the vicinity of the switching element 33 assembled on the substrate 9 a, and current is limited by the operating temperature of the switching element 33. That is, in EPS1, a large current may flow in a short time, and overheating is expected depending on usage conditions. Therefore, the motor 5 can always be used within the allowable temperature range by detecting the operating temperature of the switching element 33, which is generally set lower than the winding operating temperature of the motor 5, by the temperature sensor and limiting the current. it can. Wiring can be eliminated by assembling the temperature sensor directly on the substrate 9a.

  The motor wiring connecting the control circuit 9 (each switching element 33) and the motor 5 (brush 22) is connected via a connection terminal 43 provided in the control circuit 9, as shown in FIGS. Has been. That is, the pigtail 44 (see FIGS. 2 and 8) connected to the brush 22 is generally made of a copper mesh wire to lower the resistance. On the other hand, each switching element 33 is connected by a bonding wire 45. In this way, since the connection method is different between the brush 22 and each switching element 33, in this embodiment, the connection terminal 43 is provided (insert molding) on the outer case 9b (made of resin) of the control circuit 9, and this connection is made. Motor wires are realized by connecting the bonding wires 45 from the respective switching elements 33 to the terminals 43 and connecting (welding or the like) the pigtails 44 of the brushes 22 (see FIG. 8).

  The EPS 1 composed of the above-described components is integrated with the motor 5, the control circuit 9, the electromagnetic clutch 6, and the steering angle sensor 7 and accommodated in one motor housing 10, so that the function of each component is not impaired. The component layout for improving the mounting density is important. In addition, since heat generating parts such as the motor 5 and the control circuit 9 are concentrated, it is important to ensure good heat dissipation.

  Therefore, in this embodiment, the layout structure shown in FIG. 1 is adopted in order to obtain good heat dissipation without impairing the function of each component. Basically, from the viewpoint of heat dissipation design, as shown in FIG. 7 (model diagram showing heat flow), heat generated from the motor 5 and the control circuit 9 is transmitted to the end frame 11, and from the end frame 11. The rack housing 13 (made of aluminum) of the steering mechanism 3 is configured to dissipate heat. Therefore, the heat generated from the armature 19 and the brush 22 of the motor 5, which are the main heat generating parts, and the switching element 33 (heat generation due to the switching operation) and the capacitor 42 (loss due to the reactive current) of the control circuit 9 is efficiently end-framed. It is necessary to consider the arrangement for transmitting to the terminal 11.

  a) First, the arrangement of the motor 5 will be described. In the motor 5, a shaft 20 is coaxially arranged via an electromagnetic clutch 6 with respect to the output shaft 4 taken out to the end frame 11 side. Therefore, in order to efficiently transmit the heat generated from the brush 22 to the end frame 11, it can be said that the commutator 21 should be disposed toward the end frame 11 side. That is, the thermal resistance between the brush 22 and the end frame 11 can be reduced by arranging the brush 22 near the end frame 11.

  In terms of function, it is desirable to arrange the brush 22 on the opposite side of the commutator 21 with respect to the control circuit 9 arranged on the side of the motor 5 (see FIG. 8). That is, the brush 22 is configured to move by being pressed by the spring 46 (see FIG. 2) so that contact pressure with the commutator 21 is always obtained even if the brush 22 is worn by sliding contact with the outer peripheral surface of the commutator 21. ing. For this reason, when the brush 22 is disposed on the control circuit 9 side with the commutator 21 as the center, the pigtail 44 connected to the brush 22 is shortened, so that the brush 22 is stressed and the mobility of the brush 22 is deteriorated. Therefore, as shown in FIG. 8, by arranging the brush 22 on the opposite side of the control circuit 9 with the commutator 21 as the center, the pigtail 44 becomes longer, and accordingly, the pigtail 44 can have a degree of freedom. The mobility of the brush 22 is not impaired.

  In order to efficiently transfer the heat generated from the brush 22 to the end frame 11, as shown in FIG. 9, the pigtail 44 is covered with a sleeve 47 made of an insulating member having a low thermal resistance, and this pigtail 44 is covered with the end frame 11, Alternatively, it can be fixed to a metal member (for example, the housing 25 of the electromagnetic clutch 6) in thermal contact with the end frame 11 with a clamp 48 or the like. Thereby, the heat generated from the brush 22 can be transmitted to the end frame 11 or the metal member (hereinafter referred to as the housing 25) through the pigtail 44. Note that the pigtail 44 may be fixed to the end frame 11 or the housing 25 with a bare wire without covering with the sleeve 47 by performing an insulation treatment such as anodizing on the surface of the end frame 11 or the housing 25. .

  On the other hand, heat generated from the brush 22 can be radiated to the end frame 11 through the brush holder 23. Specifically, the brush holder 23 is made of a material having good thermal conductivity (for example, aluminum), and the end frame 11 or the surface of the housing 25 is provided with an alumite layer 11a having a low thermal resistance and an insulating property (described above). Alumite treatment), the brush holder 23 is fixed from above the alumite layer 11a with screws 50 or the like (see FIG. 10). Thereby, the heat generated from the brush 22 is transmitted to the end frame 11 or the housing 25 via the brush holder 23. 1 and 2, the brush holder 23 is fixed to the housing 25 of the electromagnetic clutch 6. However, since the housing 25 is in thermal contact with the end frame 11, the heat transferred to the housing 25 is It is well transmitted to the end frame 11.

  Further, as shown in FIG. 11, the contact surfaces of the brush 22 and the brush holder 23 can be made uneven so that the heat transfer property can be improved by expanding the contact area between the two. In this case, an insulator 51 (an insulating member having a low thermal resistance) may be interposed between the brush holder 23 and the end frame 11 or the housing 25, and the above-described alumite treatment is performed on the surface of the end frame 11 or the housing 25. You may give it. Alternatively, an insulating film (painting or the like) that can ignore the thermal resistance is provided on the inner surface of the brush holder 23, that is, the surface in contact with the brush 22 to insulate the brush 22 from the end frame 11 or the surface of the housing 25. You may fix the brush holder 23 directly, without performing an insulation process (or without interposing an insulator).

  b) Next, the arrangement of the control circuit 9 will be described. As shown in FIG. 1, the control circuit 9 is formed on the side of the motor 5 in a state parallel to the magnet 18 of the motor 5, thereby forming the connector 16 integrally with the outer case 9 b of the control circuit 9. It can be taken out from the outlet 17 as it is. Also, with this arrangement, each switching element 33 and the capacitor 42 can be arranged near the end frame 11, so that the heat generated by the switching operation of each switching element 33 and the heat generated from the capacitor 42 can be efficiently obtained from the end frame. 11 can be transmitted. In order to reduce the thermal resistance between the control circuit 9 and the end frame 11, a substrate 9a (metal base) in the control circuit 9 is provided on the end frame 11, as shown in FIG. It may be fixed with screws 52 or the like.

  Next, the operation of the EPS 1 of this embodiment will be described. When the driver steers the steering 8, the steering force is detected by the torque sensor 34 and input to the control circuit 9. In the control circuit 9, the assisting torque is calculated according to the input signal from the torque sensor 34 and the vehicle speed signal input from the vehicle speed sensor 35, and the motor current for generating the torque is set. Then, a duty signal for driving each switching element 33 is created from the current command value for commanding the motor current and the current flowing through the motor 5, and each switching element 33 is determined from the duty signal and the direction in which torque assist is to be performed. Is turned ON / OFF, the voltage from the battery 53 (see FIGS. 3 and 4) to the motor 5 is varied, and the current flowing through the motor 5 is controlled.

  Torque generated by the motor current is transmitted to the output shaft 4 via the electromagnetic clutch 6 and further transmitted to the speed reducer 2 meshing with the output shaft 4 to assist the steering mechanism 3 with torque. As a result, the driver's steering force is reduced, the output of the torque sensor 34 is reduced, and the steering operation ends. However, when the computer 37 in the control circuit 9 diagnoses that the EPS 1 is operating abnormally, the coil 27 of the electromagnetic clutch 6 is de-energized and the motor 5 and the steering mechanism 3 are disconnected. As a result, the driver can manually operate regardless of the state of the motor 5, and safety is ensured.

  When the vehicle is turning, a self-aligning torque (SAT: force for restoring the steering wheel 8 to the neutral position) is generated in the tire 54 (see FIG. 3). When the control is released, the steering 8 always acts to return to the neutral rudder angle position by the SAT. However, when the EPS 1 is mounted, the friction torque of the motor 5 (load torque at the time of non-assist) is amplified by the speed reducer 2 and becomes larger than SAT. Therefore, even if the steering wheel 8 is released, the steering wheel 8 remains neutral. It will not return to the corner position. Therefore, by detecting the steering angle with the steering angle sensor 7 and controlling the motor current based on the detected value, it is possible to restore control to the neutral steering angle position when the steering 8 is released.

(Characteristics and effects of this embodiment)
(1) The EPS 1 of the present embodiment integrates the control circuit 9, the electromagnetic clutch 6, and the steering angle sensor 7 with the motor 5 into a single motor housing 10 to make it smarter. 5, the electromagnetic clutch 6 and the steering angle sensor 7 can be connected inside the motor housing 10. Thereby, the signal lines (that is, the number of harnesses) to the outside can be reduced, and the number of external connection connectors provided in the control circuit 9 can be reduced. As a result, the entire system can be reduced in size and weight, and the probability of signal transmission failure due to poor connector contact or harness biting can be greatly reduced, improving reliability.

  (2) Further, when each switching element 33 for controlling the motor current is switched, generally, more radio noise is radiated from the harness to the motor 5 than the power line of the battery 53. However, in the EPS 1, since the control circuit 9 and the motor 5 are internally connected, the radio noise generated by the switching operation of each switching element 33 is reduced by the electromagnetic shielding effect by the motor case 12, so that the radio noise The problem can be solved.

  (3) Further, the heat generated from the motor 5 and the control circuit 9 is efficiently radiated to the end frame 11, so that the heat radiation due to the convection of the air layer inside the motor housing 10 is reduced, and the internal ambient temperature is reduced. Since the rise can be suppressed, stable operation can be guaranteed.

  Further, the heat transmitted to the end frame 11 can be radiated to the atmosphere via the rack housing 13 of the steering mechanism 3. Since the rack housing 13 is made of aluminum and has good heat dissipation and mechanical strength is required, the rack housing 13 is thick and therefore has a large heat capacity. Therefore, the end frame 11 is fixed in close contact with the rack housing 13. Thus, the heat capacity of the rack housing 13 can be considered to be included in the heat capacity of the end frame 11 equivalently. The steering mechanism 3 is located at a lower position in the vehicle and is lower (low temperature) than in the high temperature engine room, but it may be heated by a high temperature exhaust pipe or the like. However, it can be easily shielded by installing a shielding plate between the exhaust pipe and the temperature rise due to radiant heat can be suppressed.

  Therefore, even if the amount of heat generated from the motor 5 or the control circuit 9 is large, heat is sequentially transferred from the end frame 11 to the rack housing 13, so that an increase in temperature of the end frame 11 can be suppressed. Note that in order to fix the end frame 11 in close contact with the rack housing 13, the surface of the rack housing 13 to which the end frame 11 is fixed has a low heat resistance and a high sealing performance (the coating material of the present invention). Etc. may be applied.

  Incidentally, the EPS 1 does not perform torque assist when the vehicle is running straight, but performs torque assist only when turning and consumes energy. However, since the turn traveling is less frequent than the straight travel, the energy consumption is small, and therefore, it can be said that the average heat generation from the motor 5 and the control circuit 9 is also small. For this reason, the heat transmitted from the motor 5 or the control circuit 9 to the end frame 11 is easily radiated from the rack housing 13 into the air.

  On the other hand, when moving from a narrow parking lot, a stationary state that is a large torque assist exists for a short time. For this reason, although it is a short time, the emitted-heat amount from the motor 5 or the control circuit 9 becomes large. However, even if the calorific value is large, it can be said that the temperature of the end frame 11 does not rise so much because the overall heat capacity including the rack housing 13 is large as described above. Further, since the armature 19 of the motor 5 having the largest heat generation amount is composed of a core made of a magnetic material and a copper wire, the heat capacity is large and the temperature does not rise in a short time. Therefore, the temperature of each part is determined by the average temperature of the end frame 11, that is, the average temperature of the rack housing 13.

  4) In the EPS 1 of this embodiment, since the steering angle sensor 7 is provided on the motor 5 side of the speed reducer 2, the resolution, that is, the detection accuracy is improved more than the actual steering angle. For this reason, even if the detection accuracy per rotation is lowered, there is little influence on the detection accuracy of the steering angle, so it is possible to use a low-cost sensor. Further, the steering angle sensor 7 shares the armature 19 of the electromagnetic clutch 6 as a rotating body, and the magnetic detection means 31 is directly soldered on the substrate 9a of the control circuit 9, so that the components are greatly increased. Can be reduced.

[Modification]
In this embodiment, the DC motor 5 is used, but a brushless motor that controls the rotation speed by the output frequency of the inverter may be employed. The EPS 1 of the present embodiment has a system configuration including an electromagnetic clutch 6 and a steering angle sensor 7 as protection means, but the electromagnetic clutch 6 and the steering angle sensor 7 are not necessarily required. That is, any configuration may be used as long as at least the control circuit 9 and the motor 5 are integrated and accommodated in one motor housing 10.

  In the present embodiment, the rack mounting method in which the end frame 11 of the EPS 1 is fixed to the rack housing 13 outside the vehicle compartment has been described, but a column mounting method in which the EPS 1 is mounted near the column in the vehicle interior may be employed. That is, even in the column assist system in which torque assist is performed with respect to the steering shaft via a speed reducer, since the metal housing having a good heat conductivity covering the steering mechanism such as the steering gear is provided, the end frame of the EPS 1 is provided on the metal housing. 11 may be fixed and heat may be radiated from the end frame 11 to the metal housing.

It is a whole sectional view showing the internal structure of EPS. It is an enlarged view which shows the structure of the end frame vicinity of FIG. It is a block diagram which shows the drive system of EPS. It is a block diagram which shows the internal structure of a control circuit. It is a perspective view which shows the connection terminal of a control circuit. It is side surface sectional drawing which shows the connection terminal of a control circuit. It is a model figure which shows the flow of heat. It is a top view which shows arrangement | positioning of a brush. It is a side view which shows the attachment state of a pigtail. It is sectional drawing which shows the example of attachment of a brush holder. It is a perspective view which shows the example of attachment of a brush holder. It is sectional drawing which shows the example of attachment of a control circuit.

Explanation of symbols

1 EPS (Electric Power Steering Device)
3 Steering mechanism 4 Output shaft 5 Motor 6 Electromagnetic clutch (protection means)
9 Control circuit 9b Outer case (insulating member)
10 Motor housing 11 End frame (motor housing)
11b Heat sink 12 Motor case (motor housing)
13 Rack housing (mounting member)
16 Connector 20 Shaft 21 Commutator 22 Brush 23 Brush holder 25 Electromagnetic clutch housing (metal member)
28 Rotor (Drive-side rotating body)
29 Armature (driven rotating body)
30 Magnetic body (steering angle detection means)
31 Magnetic detection means (steering angle detection means)
33 Switching element 43 Connection terminal 44 Pigtail 45 Bonding wire 47 Sleeve (insulating member with low thermal resistance)
51 Insulator (insulating member with low thermal resistance)

Claims (12)

An output shaft coupled to the steering mechanism of the vehicle;
A motor for torque assisting the steering mechanism via the output shaft;
A control circuit for controlling the current flowing to the motor,
The control circuit is integrated with the motor and accommodated in a motor housing,
The control circuit is disposed on the side of the motor in the motor housing ,
The motor housing is composed of an end frame to which each component such as the motor and the control circuit is assembled, and a bottomed cylindrical motor case that covers each component and is airtightly combined with the end frame.
A connector for external connection is taken out airtightly between the end frame and the motor case,
The motor has a commutator through which a current flows through a brush on one end side of a shaft forming a rotating shaft, and the commutator is arranged facing the end frame side,
The electric power steering apparatus , wherein the output shaft is arranged coaxially with the shaft, and is drivingly connected to the shaft on the end frame side with respect to the motor. In the electric power steering apparatus according to claim 1,
The electric power steering apparatus according to claim 1, wherein the control circuit is integrally provided with a connector for external connection. In the electric power steering apparatus according to claim 1 or 2,
Steering angle detection means for detecting the steering angle and outputting it to the control circuit;
An electric power steering apparatus characterized in that the steering angle detecting means is integrated with the motor together with the control circuit and is accommodated in the motor housing. In the electric power steering apparatus according to claim 3,
A protection means for receiving a drive signal output from the control circuit and disconnecting a connection state between the motor and the output shaft;
An electric power steering apparatus characterized in that the protection means is integrated with the motor together with the control circuit and the steering angle detection means and is accommodated in the motor housing. In the electric power steering apparatus according to claim 4,
The protection means includes a driving side rotating body that rotates integrally with the motor, and a driven side rotating body that rotates integrally with the output shaft, and the driving side rotating body and the driven side when receiving the driving signal. It is an electromagnetic clutch that separates the rotating body,
The steering angle detecting means is arranged to face the magnetic body on the outer periphery of the driven-side rotating body and the magnetic body provided on the driven-side rotating body, and to detect a change in magnetic flux accompanying the rotation of the driven-side rotating body. An electric power steering device comprising magnetic detection means for detecting. In the electric power steering apparatus according to claim 5,
The electric power steering apparatus, wherein the magnetic detection means is assembled on a substrate of the control circuit. The electric power steering apparatus according to any one of claims 1 to 6 ,
The control circuit includes four switching elements constituting an H-bridge circuit and a capacitor for smoothing a battery current associated with the switching operation of the switching elements, and is arranged in the side of the motor in a state parallel to the motor field device. An electric power steering device characterized by being arranged in The electric power steering apparatus according to any one of claims 1 to 7 ,
The electric power steering apparatus according to claim 1, wherein the brush is disposed on the side opposite to the control circuit with the commutator as a center. The electric power steering apparatus according to any one of claims 1 to 8 ,
In the control circuit, a connection terminal is provided on an insulating member integrated with the connector, a switching element for controlling a motor current is connected to the connection terminal by a bonding wire, and a pigtail of the brush is connected to the control circuit. An electric power steering device. The electric power steering apparatus according to any one of claims 1 to 9 ,
The electric power steering apparatus, wherein the motor case is made of a magnetic material. The electric power steering apparatus according to any one of claims 1 to 10 ,
The electric power steering apparatus according to claim 1, wherein the motor is a brushless motor that controls a rotation speed according to an output frequency of an inverter. An output shaft coupled to the steering mechanism of the vehicle;
A motor for torque assisting the steering mechanism via the output shaft;
A control circuit for controlling the current flowing to the motor,
An electric power steering device in which the control circuit is integrated with the motor and accommodated in a motor housing,
The motor housing is composed of an end frame to which each component such as the motor and the control circuit is assembled, and a bottomed cylindrical motor case that covers each component and is airtightly combined with the end frame.
A connector for external connection is taken out airtight from between the end frame and the motor case,
The motor has a commutator through which a current flows through a brush on one end side of a shaft forming a rotating shaft, and the commutator is arranged facing the end frame side,
The output shaft is arranged coaxially with the shaft, and is drivingly connected to the shaft on the end frame side with respect to the motor,
The electric power steering apparatus according to claim 1, wherein the control circuit is provided integrally with the connector and is disposed on a side of the motor in the motor housing.