JP5566355B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering apparatus including an electric motor that generates steering assist torque.

  An electric power steering device for an automobile detects a turning direction and a turning torque of a steering shaft that is turned by a driver operating a steering wheel, and is based on the detected value and is the same as the turning direction of the steering shaft. The electric motor is driven so as to rotate in the direction, and a steering assist torque is generated. In order to control this electric motor, a control unit (ECU: Electronic Control Unit) is provided.

As a control unit of a conventional electric power steering device, for example, one described in Patent Document 1 is known. As shown in FIG. 1 of Patent Document 1, an electric power steering device described in Patent Document 1 includes an electric motor 101 that outputs an auxiliary torque, and a worm gear 114 and a worm wheel 115 that decelerate the rotation of the electric motor 101. And a control device 120 for controlling the driving of the electric motor 101. The control device 120 includes a semiconductor switching element 121, a circuit board 122, a conductive plate 123, and a cover 124. By arranging the control device 120 between the electric motor 101 and the reduction gear 112, the control device 120 is electrically operated. The power steering device is miniaturized.
JP 2010-269893 A

  However, the connection terminal 110 is welded to the end of the armature winding 109 of the electric motor 101, and the connection terminal 110 is connected to the circuit board 122, while the circuit board 122 passes through the conductive plate 123. The semiconductor switching element 121, which is a heat generating component, is connected, and the semiconductor switching element 121 is fixed to the inner surface of the cover body 124 via a heat spreader 129 for heat dissipation. For this reason, the heat generated in the armature winding 109 of the electric motor 101 moves to the semiconductor switching element 121 via the connection terminal 110, the circuit board 122, and the conductive plate 123. That is, the heat of the armature winding 109 is transmitted to the semiconductor switching element 121, the heat transmitted from the armature winding 109 to the semiconductor switching element 121 and the heat generated by the semiconductor switching element 121 are added, and these heats are added. It is transmitted to the gear case 113 through the heat spreader 129 and the cover body 124 and is discharged from the outer surface of the gear case 113 to the atmosphere. Since the heat of the armature winding 109 is transmitted to the gear case 113 via the semiconductor switching element 121 that is a heat generating component, the electric motor 101 is not sufficiently radiated.

  Further, since the heat from the armature winding 109 is released from the gear case 113 that exists as the heat radiating portion of the semiconductor switching element 121, it is necessary to increase the thermal mass of the gear case 113, leading to an increase in the size of the gear case 113. .

  Accordingly, an object of the present invention is to provide an electric power steering apparatus that solves the above-described problems and that sufficiently dissipates heat of the electric motor.

The invention according to claim 1 includes an electric motor that applies a steering assist force to the steering shaft, and a control unit that controls the electric motor.
The electric motor is housed in a motor housing having a cylindrical portion,
The control unit includes an ECU housing disposed on the opposite side of the motor housing from the axial output shaft, and a power conversion circuit having a semiconductor switch housed in the ECU housing for controlling the driving of the electric motor And an electric power steering apparatus comprising a control circuit that is housed in the ECU housing and controls the semiconductor switch and the like,
An energizing member for electrically connecting the output terminal of the semiconductor switch and the input terminal of the electric motor is provided, and a metal plate portion of the energizing member is brought into contact with the inner surface of the motor housing or the ECU housing. And

  According to the present invention, the heat generated in the armature winding of the electric motor is transmitted from the input terminal of the armature winding to the motor housing or the ECU housing via the energizing member and the insulating material, and from the outside of the housing to the atmosphere Is released.

The invention according to claim 2 is the electric power steering apparatus according to claim 1,
The energizing member is in contact with an inner surface of the motor housing.

  According to this invention, the heat generated in the armature winding of the electric motor is transmitted from the input terminal of the armature winding to the motor housing via the energizing member and the insulating material, and from the outside of the motor housing to the atmosphere. Released. On the other hand, heat generated by the semiconductor switch is transmitted to the ECU housing and released from the outside of the ECU housing into the atmosphere.

The invention according to claim 3 is the electric power steering apparatus according to claim 1 or 2,
A metal substrate is used as the current-carrying member, a holding member made of an insulating material is provided to hold the metal substrate, and the holding member is coupled to any one of the housings so that the metal substrate and the holding member are It is sandwiched between the housings and pressed against the inner surface of any one of the housings.

  According to the present invention, since the metal substrate is pressed against the inner surface of any of the housings, the metal substrate and any of the housings are in close contact, and heat is efficiently transferred from the metal substrate to the housing.

  According to the electric power steering apparatus of the first aspect, the heat generated in the armature winding of the electric motor is transmitted to any one of the housings via the input terminal, the energizing member, and the insulating material of the electric motor, and the housing Is released from the outside into the atmosphere, so that the heat dissipation of the electric motor is improved. Further, heat generated in the armature winding of the electric motor is suppressed from being transmitted to the semiconductor switch via the output terminal of the semiconductor switch.

  According to the electric power steering apparatus of the second aspect, the heat generated in the armature winding of the electric motor is transmitted to the motor housing, while the heat generated in the semiconductor switch is transmitted to the ECU housing, Since each is released into the atmosphere from the atmosphere, heat dissipation efficiency is good. In other words, since heat is dissipated in a distributed manner, proper heat dissipation can be realized without increasing the thermal mass of the housing.

  According to the electric power steering apparatus of the third aspect, since the metal substrate is in close contact with any of the housings, heat is efficiently transferred from the metal substrate to any of the housings, and the heat generated in the armature winding of the electric motor. Is efficiently released from the exterior of either housing into the atmosphere. Further, the metal substrate is firmly fixed to any of the housings by pressing and holding the metal substrate to any of the housings by the holding member, and the metal substrate is highly attachable.

The perspective view which concerns on the principal part of an electric power steering device and abbreviate | omits a holding member (embodiment). The perspective view which shows the principal part of an electric power steering device (embodiment). A sectional view of an electric power steering device (embodiment). The expanded sectional view of the principal part of an electric power steering device (embodiment). 1 is an external perspective view of an electric power steering device (embodiment). (A) is an explanatory view showing a conventional heat transfer state, and (b) is an explanatory view showing a heat transfer state according to the present invention (embodiment). ). FIG. 4A is a graph showing a conventional temperature change, and FIG. 5B is a graph showing a temperature change of the present invention (embodiment) according to a temperature change of each part in the electric power steering apparatus.

Embodiments of an electric power steering apparatus according to the present invention will be described below.
(Constitution)
A steering mechanism for steering the front wheels of an automobile is shown in FIG. A pinion (not shown) is provided at the lower end of the steering shaft 1 connected to a steering wheel (not shown), and the pinion meshes with a rack (not shown) that is long in the left-right direction of the vehicle body. Tie rods 2 for steering the front wheels in the left-right direction are connected to both ends of the rack, and the rack is covered with a rack housing 3. A rubber boot 4 is provided between the rack housing 3 and the tie rod 1.

  An electric power steering device 6 is provided to assist the torque when the steering wheel is turned. That is, a torque sensor 5 that detects the rotation direction and the rotation torque of the steering shaft 1 is provided, and an electric motor 7 that applies a steering assist force to the steering shaft 1 based on a detection value of the torque sensor 5; A control unit (ECU) 8 that controls the electric motor 7 is provided.

  As shown in FIG. 3, the electric motor 7 is accommodated in motor housings 7a and 7b having cylindrical portions. The motor housing 7a and the motor housing 7b are stacked in the axial direction and are connected by a hexagon socket head bolt 7f. A partition wall 7g is formed on the motor housing 7a, and a partition wall 7h is formed on the motor housing 7b. An output shaft 7c is rotatably supported by the partition wall 7g and the partition wall 7h via bearings 7i and 7j. A pinion 7d is provided at the tip of the output shaft 7c, and the pinion 7d is connected to the steering shaft 1 via a gear 9 portion in FIG. The gear housing of the gear 9 is formed integrally with the rack housing 3.

  The control unit 8 includes an ECU housing 8a, a power conversion circuit 26, and a control circuit 10.

  The ECU housing 8a is disposed on the side opposite to the axial output shaft 7c of the motor housings 7a and 7b, and an O-ring 28 is provided between the motor housing 7a and the ECU housing 8a. The ECU housing 8a also serves as an ECU heat sink for cooling a MOSFET 12 described later. A partition wall 29 for partitioning the interior in the axial direction is provided inside the ECU housing 8a, and a power conversion chamber 30 is formed above the partition wall 29. Below the partition wall 29, the ECU housing 8 A control chamber 31 is formed between the inside of 8a and the inside of the motor housing 7a.

  The power conversion chamber 30 accommodates the power conversion circuit 26, and the power conversion circuit 26 has a MOSFET 12 as a semiconductor switch for driving and controlling the electric motor 7 mounted on the first metal substrate 11. It is configured. 32 is an aluminum capacitor.

  The control circuit 31 is accommodated in the control chamber 31. The control circuit 10 controls the MOSFET 12 and the like, and is configured by mounting electronic components on a printed board 13 disposed at a boundary position between the motor housing 7a and the ECU housing 8a.

  Reference numeral 27 denotes a connector connected to a battery (not shown), and power is supplied from the connector 27 to the power conversion circuit 26 and the control circuit 10.

  The control chamber 31 is provided with a heat radiating mechanism for releasing heat generated in the armature winding 7e of the electric motor 7 from the outer surface of the motor housing 7a. FIG. 4 shows an enlarged view of the portion of the heat dissipation mechanism in FIG. As shown in FIG. 1, the perspective view of the portion of FIG. 4 includes the output terminals 14u, 14v, 14w of the MOSFET 12, which is a semiconductor switch, and the input terminals 16u, 16v, 16w of the electric motor 7 as a current-carrying member. The two metal substrates 15 are electrically connected. Here, the energizing member refers to a member in which an insulating layer is formed on a metal plate and a wiring portion constituting a circuit is formed on the insulating layer. The first metal substrate 11 and the second metal substrate 15 are In either case, an insulating layer is formed on an aluminum plate, and a wiring pattern made of copper foil is printed on the insulating layer. The output terminals 14u, 14v, 14w are coupled to one side (upper side) of the second metal substrate 15, and the input terminals 16u, 16v, 16w are coupled to the other side (lower side). These terminals are connected to the second metal substrate. 15 is connected to the wiring pattern on the top.

  Two motor relays 18 u and 18 v are mounted on the second metal substrate 15. These motor relays 18u and 18v are constituted by semiconductor elements for energizing or stopping energization of the electric motor 7.

  Next, electrical connection between the motor relays 18u and 18v will be described. Due to the wiring pattern on the second metal substrate 15, the motor relay 18u is connected between the output terminal 14u of the MOSFET 12 as the semiconductor switch and the input terminal 16u of the electric motor 7, and the motor relay 18v is connected to the semiconductor switch. The output terminal 14v of the MOSFET 12 as a switch and the input terminal 16v of the electric motor 7 are connected. And the output terminal 14w of MOSFET12 as a semiconductor switch and the input terminal 16w of the said electric motor 7 are directly connected, without interposing a motor relay.

  In the second metal substrate 15 on which the motor relay 18 is mounted, the aluminum plate portion of the second metal substrate 15 is pressed and held on the inner surface of the motor housing 7a. And in order to press, the holding member 19 shown in FIG. 2 is provided. As shown in FIG. 1, the holding member 19 is formed by molding three connection fittings 20u, 20v, and 20w that are long in the horizontal direction with a resin as an insulating material.

  As shown in FIG. 2, the holding member 19 is formed in a plate shape along the axial direction. The holding member 19 has two convex portions 19a on one side in order to secure a wiring space for a resolver signal terminal 25 described later. And two recesses 19b into which the motor relays 18u and 18v enter are formed on the other side. A mounting seat 19c that protrudes in the horizontal direction is formed below the holding member 19. A screw 21 is inserted into a mounting hole formed in the mounting seat 19c and screwed into the partition wall 7g of the motor housing 7a. By being coupled to the motor housing 7a, the second metal substrate 15 is sandwiched between the holding member 19 and the motor housing 7a and pressed against the inner surface of the motor housing 7a.

  Ends 23u, 23v, 23w of the armature winding 7e of the electric motor 7 are guided along the axial direction to the opposite side of the pinion 7d of the output shaft 7c and penetrate the partition wall 7g. Ends 23u, 23v, and 23w of winding 7e are welded to one end on the radially inner side of the three connection fittings 20u, 20v, and 20w molded with resin. The radially outer ends of the three molded connection fittings 20u, 20v, 20w are connected to the lower ends of the input terminals 16u, 16v, 16w via screws 22a and nuts 22b. A work hole 7k is formed through the motor housing 7a so that the screw 22a can be rotated from the outside of the motor housing 7a.

1 and 2, reference numeral 24 is a resolver, 24 a is a rotor fixed to the output shaft 7 c of the electric motor 7, and 24 b is a stator fixed to the partition wall 7 g to detect the rotational speed of the rotor 24 a. In order to send the rotational speed of the output shaft 7 c detected by the resolver 24 to the control circuit 10, six resolver terminals 25 that connect the resolver 24 and the printed circuit board 13 are arranged along the axial direction.
(Function)
Next, the operation of the electric power steering device will be described.

  When the steering shaft 1 is turned in either direction by operating the steering wheel, the torque sensor 5 detects the turning direction and turning torque of the steering shaft 1, and based on the detected value. Then, the control circuit calculates the drive operation amount of the electric motor 7, and the electric motor 7 is driven by the MOSFET 12 of the power conversion circuit 26 based on the calculated numerical value. The output shaft 7c of the electric motor 7 is rotated so as to drive the steering shaft 1 in the same direction as the operation direction, and the rotation of the output shaft 7c is transmitted from the pinion 7d to the steering shaft 1 via the gear 9 in FIG. Is done.

  According to this embodiment, the heat generated in the armature winding 7e of the electric motor 7 is input from the end portions 23u, 23v, 23w of the armature winding 7e through the connection fittings 20u, 20v, 20w to the input terminals 16u, 16v, 16w, the input terminal 16u, 16v, 16w is transmitted to the motor housing 7a through the second metal substrate 15 and the insulating material, and discharged from the outside of the motor housing 7a to the atmosphere, or the motor housing. 7a is also transmitted to the gear 9 through the motor housing 7b. Further, not only the heat generated in the armature winding 7e of the electric motor 7, but also the heat generated in the semiconductor element as the motor relay 18 is transmitted to the motor housing 7a via the second metal substrate 15, and the motor housing 7a. Or is transmitted from the motor housing 7a to the gear 9 via the motor housing 7b.

  On the other hand, the heat generated in the MOSFET 12 is transmitted to the ECU housing 8a via the first metal substrate 11, and released from the outside of the ECU housing 8a to the atmosphere.

  According to this electric power steering device, heat generated in the armature winding 7e of the electric motor 7 is transmitted to the motor housing 7a via the input terminals 16u, 16v, 16w of the electric motor 7 and the second metal substrate 15. Since the motor housing 7a is discharged into the atmosphere from the outside or is transmitted from the motor housing 7a to the gear 9 through the motor housing 7b, the heat dissipation of the electric motor 7 is improved. Further, the heat generated in the armature winding 7e of the electric motor 7 is suppressed from being transmitted to the MOSFET 12 as the semiconductor switch via the output terminals 14u, 14v, 14w.

  According to this electric power steering apparatus, the heat generated in the armature winding 7e of the electric motor 7 is transmitted to the motor housing 7a, while the heat generated in the MOSFET 12 is transmitted to the ECU housing 8a, from outside the different housing. Since each is released into the atmosphere, heat dissipation efficiency is good. In other words, since heat is dissipated in a distributed manner, proper heat dissipation can be realized without increasing the thermal mass of the housing.

  According to this embodiment, since the second metal substrate 15 is pressed against the inner surface of the motor housing 7a, the second metal substrate 15 and the motor housing 7a are in close contact with each other, and the second metal substrate 15 is transferred to the motor housing 7a. Heat is transmitted efficiently.

  According to this electric power steering apparatus, since the second metal substrate 15 is in close contact with the motor housing 7a, heat is efficiently transferred from the second metal substrate 15 to the motor housing 7a, and is generated in the armature winding 7e of the electric motor 7. The heat is efficiently released from the outside of the motor housing 7a to the atmosphere. Further, the second metal substrate 15 is firmly fixed to the motor housing 7a by the pressing and holding of the second metal substrate 15 to the motor housing 7a by the holding member 19, so that the second metal substrate 15 is highly attachable.

  According to this electric power steering apparatus, since the motor relay 18 is composed of a semiconductor element, the heat generated in the semiconductor element is transmitted to the motor housing 7a via the second metal substrate 15, and from the outside of the motor housing 7a to the atmosphere. Or is transmitted from the motor housing 7a to the gear 9 via the motor housing 7b, and has higher heat dissipation than the mechanical relay in which heat is accumulated in the relay from the structure. Temperature rise is suppressed.

  FIG. 6 (a) in the conventional case and the present embodiment show the magnitude of the amount of heat generated when the heat generated by MOSFET 12 as a semiconductor switch and armature winding 7e of electric motor 7 is transmitted to other parts. This is shown in FIG. The point that the heat generated in the MOSFET 12 is transmitted to the ECU housing (heat sink) 8a through the first metal substrate 11 as indicated by arrows (b) and (b) is largely different between the conventional and the present embodiment. There is no. On the other hand, most of the heat generated in the armature winding of the electric motor conventionally flows to the MOSFET via the bus bar terminal and the motor relay as shown by arrows (c) (d) (e) in FIG. The heat generated in the motor relay also flows to the MOSFET as indicated by an arrow (e), and the remaining part is transmitted to the gear through the motor housing as indicated by the arrows (f) and (g). In addition, heat is transmitted from the motor housing having a high temperature to the ECU housing (heat sink) having a low temperature as indicated by an arrow (H).

  On the other hand, in this embodiment, as shown in FIG. 6B, a part of the heat generated by the MOSFET 12 and the armature winding 7e of the electric motor 7 is indicated by arrows (i) (nu). Both are transmitted to the second metal substrate 15 at the center, and transmitted from the second metal substrate 15 to the motor housings 7a and 7b and the ECU housing 8a as indicated by arrows (l) (wo). The remainder of the heat generated by the motor relays 18u, 18v is transmitted to the gear 9 through the motor housings 7a, 7b as shown by arrows (W) (f). Heat is transmitted from the ECU housing (heat sink) 8a whose temperature has been increased to the motor housings 7a and 7b as indicated by arrows (Y).

  Since the MOSFET 12 generates a large amount of heat, there is a limit to the self-heat dissipation of the MOSFET 12, and if the heat generated by the armature winding 7e of the electric motor 7 and the motor relays 18u, 18v is transferred to the MOSFET 12, excessive heat is generated. If the amount of heat stored in the MOSFET 12 increases and the amount of heat stored in the MOSFET 12 increases, the fail-safe function of the electric power steering acts, and the driving force of the electric motor is reduced to gradually lower the steering driving force. Since the electric motor is stopped, the operation of the steering wheel becomes heavy. In the present embodiment, heat generated by the armature winding 7e of the electric motor 7 and the motor relays 18u, 18v is transmitted to the motor housings 7a, 7b and the ECU housing 8a via the second metal substrate 15. The transmission to the MOSFET 12 is suppressed, and the fail safe function of the electric power steering is suppressed from acting.

  The relationship between the time and temperature of each part due to the transfer of heat generated by the MOSFET 12 as a semiconductor switch, the armature winding 7e of the electric motor 7 and the motor relays 18u and 18v is shown in FIG. FIG. 7B shows the case of the embodiment. Although there is no difference between the temperature in the gear and the motor housing between the conventional embodiment and the present embodiment, it can be seen that the temperature of the input terminal of the electric motor is lower in the present embodiment than in the conventional embodiment.

  In addition, although the 2nd metal substrate 15 was used as an electricity supply member, members other than a metal substrate can also be used. Further, the second metal substrate 15 is pressed against the motor housing 7a via the holding member 19, but the metal substrate may be directly pressed against the motor housing 7a with a bolt. Further, although the energizing member is in contact with the inner surface of the motor housing 7a, it may be in contact with the inner surface of the ECU housing 8a.

DESCRIPTION OF SYMBOLS 1 ... Steering shaft 7 ... Electric motor 7a, 7b ... Motor housing 8 ... Control unit 8a ... ECU housing 10 ... Control circuit 12 ... MOSFET (semiconductor switch)
14u, 14v, 14w ... Output terminal 15 ... Second metal substrate (current-carrying member / metal substrate)
16u, 16v, 16w ... input terminal 19 ... holding member 26 ... power conversion circuit

Claims (2)

An electric motor that applies steering assist force to the steering shaft, and a control unit that controls the electric motor,
The electric motor is housed in a motor housing having a cylindrical portion,
The control unit is mounted with an ECU housing disposed on the opposite side of the motor housing in the axial direction and a semiconductor switch housed in the ECU housing for controlling the drive of the electric motor. In an electric power steering device comprising a power conversion circuit configured by one substrate,
Providing an energization member formed by forming a wiring pattern on a second substrate which is a metal substrate different from the first substrate;
While electrically connecting the output terminal of the semiconductor switch and the input terminal of the electric motor by the energization member,
An electric power steering apparatus characterized in that a metal plate portion of the energizing member is brought into contact with an inner surface of the motor housing or the ECU housing. The electric power steering apparatus according to claim 1, wherein
A holding member made of an insulating material is provided to hold the second substrate, and the holding member is coupled to any one of the housings so that the second substrate is interposed between the holding member and any one of the housings. An electric power steering apparatus, wherein the electric power steering apparatus is sandwiched and pressed against an inner surface of any one of the housings.