Power unit for motor vehicles

Abstract: A regenerative braking system in a motor vehicle determines a state of deceleration on the basis of the number of revolutions of a motor and an accelerator signal and performs a regenerative braking according to the state of deceleration. The regenerative braking system includes a revolution sensor (90) for detecting the number of revolutions of a rotor (33) of a vehicle driving motor and an accelerator opening sensor (42) in a RAM stores discrimination data for discriminating between a regenerative braking mode and a drive mode on the basis of the number of revolutions of the rotor and the accelerator opening and also stores on-off duty ratio data of FETs in the regenerative braking mode and that in the drive mode. A CPU (111) retrieves on-off duty ratio data corresponding to the number of revolutions of the rotor and the accelerator opening in the regenerative braking mode when the regenerative braking mode is determined on the basis of the rotor revolutions and the accelerator opening, and controls the FETs at an on-off duty ratio corresponding to the retrieved on-off duty ratio data. The power unit (P) for the motor vehicle is an electric motor (152) mounted in unit cases using at least a portion of the unit cases as a motor case. In the power unit of such construction, a heat sink (166) is attached to the motor case (160). Switching elements are provided for controlling an electric current to be supplied to the electric motor. The switching elements are mounted to the heat sink.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a power unit suitable for providing power to a motor vehicle. Description of Background Art In a motor vehicle, as is well known (see for example US-A-4 532 460), electric power is supplied from a battery to a vehicle driving motor mounted on the vehicle, thereby imparting movement to the vehicle. In such a motor vehicle, when the vehicle is to be braked, a regenerative braking is performed and the kinetic energy of the vehicle is recovered as electric power to charge the battery. On the other hand, for imparting a function corresponding to an engine brake to an automobile using an internal combustion engine, there has been proposed a method (Japanese Patent Publication No. 12446/77) in which, when the accelerator signal level decreases, a differential value thereof is taken and switching is made into a regenerative braking state during a period corresponding to the said differential value, thereby maintaining the motor vehicle in a braked condition during that period. In addition, a motor vehicle is also well known, wherein an output of an electric motor serves as a power source which is transmitted to a wheel to drive the wheel, thereby causing the vehicle to impart motion thereto. Motor vehicles of this type are known as described in Japanese Patent Laid Open No. 38043/79 and Utility Model Laid Open No. 80848/76. In the above motor vehicles, particularly motor-driven two-wheeled vehicles, it is absolutely necessary to provide a power unit which is a combination of an electric motor and a power transmission mechanism. The present inventors have also proposed a power unit for motor vehicles suitable for two-wheeled vehicles as set forth in Japanese Patent Application No. 181496/89, filed in the Japanese Patent Office on July 13, 1989. According to the construction of the power unit for motor vehicles as previously set forth, a power transmission mechanism such as a stepless transmission is enclosed in a unit case, and a motor case of an electric motor is connected to the unit case using bolts or the like. A rotating shaft of the electric motor is connected to the stepless transmission. Further, a drive circuit connected by wiring to the electric motor is provided in the vehicle body for example to supply electric power to the motor. Document US-A-4 532 460 concerns an electric four-wheeled vehicle. The external, ferrite permanent magnet rotor of an A.C. electric motor drivingly engages the input shaft of a transaxle transmission via a V-belt, to operate the front wheels of the vehicle. Separate compartments respectively contain a chemical battery and a control circuit, connected to the electric motor by cables. Document FR-A-2 153 307 describes a DC electric motor and its associated commutating device. This commutating device is located at the end of the motor opposite to its output shaft. The commutating device is carried by a support plate secured to the motor frame and it comprises Hall probes, a printed circuit, and transistors provided with heat sinks facing the motor. Document DE-A-19 05 624 shows a dentist electric drill tool. The tool comprises an electric motor and an electronic commutator provided at the motor end opposite to its output shaft. SUMMARY AND OBJECTS OF THE PRESENT INVENTION Generally, in a power unit for motor vehicles, a relatively large output torque is required for an electric motor. Thus, it is necessary to supply a high electric current to the motor. Consequently, in the power unit for motor vehicles described in the foregoing example wherein a drive circuit is disposed on the vehicle body side, it is required to connect the drive circuit on the vehicle body side and the electric motor through long wiring, resulting in a drop of voltage. The measures necessary to counteract electromagnetic noise are also complicated. The present invention overcomes the above-mentioned problems. It is an object of the invention to provide a power unit for motor vehicles which diminishes the drop in the voltage applied to an electric motor and also permits taking a simple measure against electromagnetic noise. In order to achieve the above-mentioned object with regard to a drop in the voltage, a power unit according to claim 1 is provided. In a preferred embodiment, a construction is provided wherein a cover member covers the switching elements-mounted portion of the heat sink and is mounted on the heat sink. Resin is filled between the cover member and the heat sink to fix the two to each other. The heat sink is fixed to the motor case. The unit case is divided into the motor case and a case body in the axial direction of the rotating shaft between end portions of the same shaft. A bearing rotatably supports one end portion of the rotating shaft. A rotation sensor for detecting the rotation of the rotating shaft and the heat sink are provided in the motor case. The heat sink is disposed on one side of the bearing in the axial direction of the rotating shaft, while the rotation sensor is disposed on the other side of the bearing in the axial direction of the rotating shaft. A stator of the electric motor is fixed to the motor case. The stator and the rotation sensor are disposed adjacent each other in the axial direction of the rotating shaft. Connecting terminals are provided on the heat sink-side face of the motor case and power supply terminals are provided on the motor case-side face of the heat sink. A plate member is disposed in a predetermined position between the motor case and the heat sink. Terminals for electrical conduction and connection between the power supply terminals of the heat sink and the connecting terminals of the motor case are provided on the plate member. The heat sink is provided in the unit case in proximity to the electric motor and switching elements which constitute a drive circuit which are mounted to the heat sink. Thus, it is possible to shorten the wiring which connects the drive circuit and the motor, resulting in a diminished drop of voltage. Further, it is easy to take a measure to reduce electromagnetic noise. Since the switching elements are mounted to the heat sink provided in the unit case, it is not necessary to use a special support member for supporting the drive circuit. The number of parts can be decreased and a reduction of size of the device is attainable. The switching elements-mounted portion of the heat sink is covered with resin. It is possible to protect the switching elements without impairing the cooling property and without an increase in weight. The motor case is divided from the case body. In the case body, the heat sink is disposed together with a bearing and rotation sensor in the axial direction of the rotating shaft. It is possible to attain a further reduction of size, and the assembly can be facilitated by mounting the heat sink, etc. beforehand to the divided case. The stator of the electric motor is also fixed to the divided case, electric parts such as the stator coil of the motor, rotation sensor and drive circuit can be mounted in a unitized form. The assembly thereof can be accomplished more easily, and it is also possible to simplify the wiring. The motor case terminals and the heat sink terminals are rendered conductive with each other through terminals. It is not necessary to wire the terminals. The mounting of the heat sink to the motor case can be accomplished very easily. Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the scope of the invention as defined by the appended claims will become apparent to those skilled in the art from this detailed description. BRIEF DESCRIPTION OF THE DRAWINGS The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from scope of the invention, as defined by the following claims. Figure 1 is a side view of a motor-driven two-wheeled vehicle equipped with a power unit for a motor vehicle according to an embodiment of the present invention; Figure 2 is a sectional view of the power unit for a motor vehicle; Figure 3 is a partially cut-away sectional view showing a principal portion of the power unit for a motor vehicle; Figure 4 is a left side view of the principal portion; Figure 5 is a right side view of the principal portion; Figure 6 is an exploded perspective view on a larger scale of a part of the principal portion; Figure 7 is an electrical circuit diagram of the power unit for a motor vehicle; Figure 8 is a sectional view of a principal portion of a power unit for a motor vehicle according to another embodiment of the present invention; Figure 9 is a partially sectional view showing another mode of a motor case in the power unit for a motor vehicle; Figure 10 is a partial left side view of the motor case; Figure 11 is a partial right side view of the motor case; Figure 12 is an exploded perspective view of a principal portion of a power unit for a motor vehicle according to a further embodiment of the present invention; Figure 13 is a view as seen in the direction of arrows 13-13 in Figure 12; Figured 14 is a partially enlarged sectional view of the power unit for a motor vehicle; Figure 15 is a view as seen in the direction of arrows 15-15 in Figure 14; Figure 16 is a view showing main parts of the power unit for a motor vehicle; Figure 17 is a view showing other main parts of the power unit for a motor vehicle; Figure 18 is a partially enlarged view of the power unit for a motor vehicle; Figure 19 is a sectional view of a principal portion of the power unit for a motor vehicle; Figure 20 is a sectional view of another principal portion of the power unit for a motor vehicle; Figure 21 is a sectional view of a principal portion of a power unit for a motor vehicle according to a still further embodiment of the present invention; Figure 22 is a right side view of the principal portion; Figure 23 is an enlarged view of a principal portion of the power unit for a motor vehicle; Figure 24 is a sectional view thereof; and Figure 25 is a sectional view showing another mode in the power unit for a motor vehicle. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Figures 1-8 illustrate a power unit for a motor vehicle according to an embodiment of the present invention. Figure 1 illustrates a vehicle body frame 111 which is generally U-shaped in side view. The vehicle body frame 111 has a front frame 111f, a center frame 111d and a rear frame 111r, and it is covered with a synthetic resin body 121 which includes a front cover 121f, a leg shield 121a, a step floor 121b, a rear cover 121c and an under cover 121d. A head tube 112 is fixed to the front portion of the front frame 111f of the vehicle body frame 111, and a front wheel 114f is supported by the head tube 112 through a front fork 113 so that it can be steered with a steering handle 115. The steering handle 115 has an accelerator grip 115a. A potentiometer 115b for detecting an operation angle of the accelerator grip 115a is attached to the steering handle 15, see Figure 7. A control box 116 is mounted to the front portion of the head tube 112, and the front side of the control box 116 is covered with the front cover 121f. In the interior of the control box 116 is accommodated a controller 149 comprising an ECU for example. The potentiometer 115b and a charging circuit, a drive circuit and a battery which will be described later are connected to the controller 149. A battery box 122 is provided on the center frame 111d of the vehicle body frame 111, and a power swing unit, power unit for a motor vehicle, 150 is supported pivotably by a pivot shaft, not shown. As will be described later, the power swing unit 150 includes an electric motor 152, etc. mounted in a case 151, and it supports a rear wheel 114r rotatably at the rear end of the case 151. A cushion unit 199 is disposed between the rear portion of the power swing unit 150 and the vehicle body frame 111. The battery box 122 is mounted on a battery holder 123 fixed to the center frame 111d and is clamped with a band 124. A plurality of batteries are positioned within the battery box 122, see Figure 7. The batteries 136 are connected together in parallel or in series and then connected to a later-described drive circuit and the foregoing controller 149. Though not clearly shown in the drawings, the battery holder 123 comprises a plate-like member mounted bridgewise in the vehicle width direction below the center frame 111d, and the step floor 121b is secured through the band 124 onto the battery box 122 mounted on the battery holder 123. Further, the rear cover 121c is fixed to the rear frame 111r of the vehicle body frame 111. The rear cover 121c is generally in the form of a hollow cylinder having an open upper portion. A seat 126 is supported on the top of the rear cover so that it can close the opening. The front portion of the seat 126 is mounted to the upper portion of the rear cover 121c using a hinge or the like. When used as a seat, a driver is permitted to sit thereon, see Figure 1. The seat closes the opening of the rear cover 121c, while in a forwardly brought-down state of the seat, it allows the opening of the rear cover 121c to be exposed. A trunk box 25 and a charging box 27 are positioned within the rear cover 121c obliquely forward and upward of the rear wheel 114r and in front and rear positions, respectively. The upper portion of the trunk box 125 is open and this opening is covered with the seat 126 so that it can be opened and closed. The trunk box 125 has size and capacity permitting a helmet to be received therein. The charging box 127 is generally L-shaped in side view having an upwardly projecting front portion, and a front upper portion thereof is open. The charging box 127 houses therein a charger, etc. for charging from a commercial AC power source, and its front upper opening is closed with a lid 128 so that it can be opened and closed. On one face of the lid 128 is provided a charging circuit 197, and this charging circuit and the charger are connected to the batteries 136, etc. In Figure 1, an intake duct 188 is disposed within the rear cover 121c. One end of the intake duct 188 is connected to a cooling air inlet of the power swing unit 150 and an opposite end thereof is open into the rear cover 121c. The power swing unit 150 is constructed as shown in Figure 2. The electric motor 152, a stepless transmission 153 and a final reduction mechanism 154 are integrally mounted to the case body 151 wherein the front end is supported pivotably by the vehicle body frame 111. The case body 151 is formed by the casting of an aluminum alloy for example, and a recess 151a is formed in a front right-hand side portion of the case body and a recess 151b formed in a rear left-hand side portion thereof. In the case body 151, a motor case 160 is fixed to the front right-hand recess 151a to define a motor chamber 131 for accommodating the electric motor 152, while a bearing member 157 is fixed to the rear left-hand recess 151b to define a gear chamber 158 for accommodating the final reduction mechanism 154. Further, a side cover 155 is fixed to the left side portion of the case body to define a transmission chamber 156 for accommodating the stepless transmission 153. The motor chamber 131 and the transmission chamber 156 are in communication with each other for ventilation through a through hole 134 formed near the bottom of the recess 151a of the case body 151. The transmission chamber 156 is open to the atmosphere through an exhaust port, not shown. It is also possible to construct the case body 151 as illustrated in Figures 9, 10 and 11. As shown in Figures 9, 10 and 11, in the case body 151, a boss 151e is formed centrally of the bottom of the recess 151a. A plurality of spoke-like ribs 151f are formed on the left side face of the case body and extend radially outward from the boss 151e. Through holes 151g are formed each between adjacent ribs 151f. In the box 151e is formed a through hole 151h, through which there extends a rotating shaft 161 of an electric motor as will be described later. The through holes 151g are formed in a corresponding relation to a cooling fan which will be described later, and cooling air flows through the through holes 151g into the transmission chamber 156. In Figure 10, a rib 151i is provided for improving rigidity. The motor case 160 is in the form of a bottomed cylinder having one open end and it is fixed with bolts 130 to the case body 151 in an aligned state of the opening with the opening of the recess 151a to define the motor chamber 131. At the bottom of the motor case 160 there is provided a bearing 132, and the rotating shaft 161 is supported rotatably by both the bearing 132 in the motor chamber 131 and a bearing 133 disposed at the bottom of the recess 151a of the case body 151. One end of the rotating shaft 161 extends through the bottom of the recess 151a and is connected to the stepless transmission 153 in the transmission chamber 156, while an opposite end thereof extends through the bottom of the motor case 160. A cooling fan 159 is mounted on the rotating shaft 161 in close proximity to the bottom of the recess 151a in the motor chamber 131 and in a position facing the through hole 134. Further, a rotor 163 including a magnet is fixed onto the rotating shaft 161 in a central position of the motor chamber 131. A rotation sensor 170 is mounted onto an end portion of the rotating shaft extending through the bottom of the motor case 160. As is well known, the rotor 163 including the magnet are positioned inside the stator. The cooling fan 159, which rotates integrally with the rotating shaft 161, introduces cooling air into the motor chamber 131 through the intake duct 188 and delivers it into the transmission chamber 156 through the through hole 134. The rotation sensor 170 includes a magnet fixed onto the rotating shaft 161 and a magnetism sensitive element such as an MR element mounted to the right-hand face of the bottom of the motor case 160. The magnetism sensitive element is connected to the controller 149. The rotation sensor 170 detects a rotational position and a rotating speed of the rotational shaft 161. Three stator coils 162 which include the stator are fixed to the left-hand face on the motor chamber 131 side of the motor case 160, and a heat sink 166 is fixed to the right-hand face. The three stator coils 162 are Y-connected together, see Figure 7, and three terminals are connected to a drive circuit which will be described later. The motor case 160 corresponds to a divided case and constitutes a unit case together with the case body 151. The heat sink 166 is constituted by a generally hexagonal, cylindrical extrude of an aluminum alloy having an outer periphery which is hexagonal in section, and a large number of cooling fins 167 are formed on the inner periphery of the heat sink. The heat sink 166 is fixed to the motor case 160 by threaded engagement of three bolts 198 extending axially through the heat sink with the motor case 160, and the outer periphery thereof is covered with a cover member 165. The cover 165 houses therein a substrate 147 provided internally with a gate drive circuit 148, and is fixed to the heat sink 166 with resin 146, e.g. an epoxy resin, filled between the cover 165 and the outside surface of the heat sink 166. An intake port is formed in the cover 165 which is connected to the intake duct 188. The heat sink 166 can also be formed by the casting of an aluminum alloy. A total of six field effect transistors (FETs) 135a, 135b, 135c, 135d, 135e and 135f, hereinafter represented by the subscript-free numeral where required, are provided on the six faces of the outer periphery of the heat sink 166. One transistor is provided for each face to constitute a drive circuit 164. Further, a power stabilizing capacitor 168 is disposed along the inner peripheral portion of the heat sink. Between the capacitor 168 and the inner peripheral portion of the heat sink 166 is formed a cooling air passage 137 which is in communication with the intake duct 188, with the cooling fins 167 projecting into the cooling air passage 137. The capacitor 168 is connected between plus and minus terminals of each battery 136 in parallel with the drive circuit 164. The FETs 135 can each include plural FETs connected in parallel. The drive circuit 164 comprises the FETs 135 connected bridgewise, as shown in Figure 7. More specifically, the source of FET 135a and the drain of FET 135d, the source of FET 135b and the drain of FET 135e, and the source of FET 135c and the drain of FET 135f, are bridgewise connected, respectively. In the drive circuit 164, a line 140 is connected to the plus terminal of each battery 136 and is positioned on one side of the outer periphery of the heat sink 166 A line 141 is connected to the minus terminal of the battery 136 and is positioned on another side of the outer periphery of the heat sink. The drains of FETs 135a, 135b, 135c are connected to the line 140, while the sources of FETs 135d, 135e, 135f are connected to the line 141. As shown in detail in Figures 1 and 2, terminals 139 are connected between the sources and the drains of the FETs 135 and end portions of the three terminals 139 are each covered with an insulator 143 and secured to an end face of the heat sink 166 with bolts 142. The bolts 142 are inserted along the inner periphery of the heat sink 166 from the case body 151 side until their end portions project to the exterior of the cover 165 through a boss portion 165b which projects from the cover 165 toward the inner periphery of the heat sink 166. As shown in Figure 5, the three bolts 142 are disposed at approximately equal intervals in the circumferential direction in which a manner that one of the bolts is located in a vertical top position and the other two are located in positions higher than a vertical bottom position. One end on the case body 151 side of the bolts 142 are electrically insulated from the heat sink 166 each through the insulator 143 and are brought into electric conduction with the terminals 139, while opposite ends thereof are connected with terminals 138 outside the cover 165. As shown in Figure 6, the terminals 138 are each disposed between a pair of ribs 165b for swivel stop formed integrally on the outer surface of the cover 165, then fixed to the bolt 142 with a nut 144 which is threadedly engaged with the end portion of the bolt 142, and thereby connected electrically to the bolt 142. The terminals 138 are connected to the stator coils 162 through lines 145 laid along the inner periphery of the heat sink 166 and are connected between the sources and the drains of FETs 135. The line 140, etc. for connection of these FETs 135 terminals 139 with the batteries 136 are coated with the resin 146 filled between the outer periphery of the heat sink 166 and the cover 165. The gates of the FETs 135 are connected to the gate drive circuit 148 in the substrate 147. As shown in Figure 7, the gate drive circuit 148 includes a booster circuit, etc. and is connected to the controller 149 and outputs a drive signal to the FETs 135 on the basis of an output signal provided from the controller 149. In Figure 7, an accelerator sensor 115b is provided for detecting an operation angle of the accelerator grip 115a. A brake sensor 195 is provided for detecting the operation of a brake. A vehicle speed sensor 196 is provided for detecting the vehicle speed, the sensors 115b, 195 and 196 are connected to the controller 149. The stepless transmission includes stretching a belt 174 between a driving pulley 172 and a driven pulley 173. The driving pulley 172 is mounted on the rotating shaft 161 of the electric motor 152. The driven pulley 173 is mounted-on a sleeve 178 which is mounted rotatably on an input shaft 171 of the final reduction mechanism 154. The driven pulley 173 is connected in parallel to the input shaft 171 through first and second centrifugal clutches 175, 176. The driving pulley 172 includes a fixed face 172a fixed to the rotating shaft 161 and a movable face 172b mounted axially movably on the shaft 161. In the drive pulley 172, the movable face 172b is driven by a governor mechanism 177 having a weight 177a and thereby moves axially, resulting in the diameter of the belt 174 on the pulley changes in accordance with the rotating speed of the rotating shaft 161. Likewise, the driven pulley 173 comprises a fixed face 173a fixed to the sleeve 178 and a movable face 173b supported axially movably on the sleeve 178. In the driven pulley 173, the movable face 173b is urged to the fixed face 173a side by means of a spring 180a disposed in a compressed state between the second centrifugal clutch 176 and a clutch outer 179. The movable face 173b moves in accordance with the change in the belt diameter on the driving pulley 172 to change the belt diameter on the driven pulley. In the second centrifugal clutch 176, the clutch outer 179 is fixed to the sleeve 178. A clutch inner 180 is provided in a clutch outer 181 of the first centrifugal clutch 175. The second centrifugal clutch 176 is engaged and released according to the rotating speed of the clutch outer 181 of the first centrifugal clutch 175. In the first centrifugal clutch 175, the clutch outer 181 is fixed to the input shaft 171, and a clutch inner 182 is provided in the clutch outer 179 of the second centrifugal clutch 176. The first centrifugal clutch 175 is engaged and released according to the rotating speed of the clutch outer 179 of the second centrifugal clutch 176. The first centrifugal clutch 175 is engaged at a number of revolutions somewhat smaller than that of a maximum efficiency of the electric motor 152, while the second centrifugal clutch 176 is engaged at a number of revolutions smaller than that at which the first centrifugal clutch 175 is engaged. A detailed explanation of the structures of the first and second centrifugal clutches 175, 176 is here omitted for brevity. The final reduction mechanism 154 has a gear 171a fixed onto the input shaft 171, gears 183a and 183b fixed onto an intermediate shaft 183, and a gear 184a fixed to an output shaft 184. The gears 171a and 183a are in mesh with each other, while the gears 183b and 184a are also in mesh with each other. The input shaft 171 is supported rotatably by both the case 151 and the bearing member 157. As mentioned above, the left end portion of the input shaft 171 projects into the transmission chamber 156 and is connected with the stepless transmission 153. The output shaft 184 is projecting to the right-hand side of the case 151, and the rear wheel 114 is fixed to an end portion of the output shaft 184. The operation of this embodiment will be described below. In a motor-driven two-wheeled vehicle according to the present invention, the electric power of the batteries 136 is supplied to the electric motor 152 of the power swing unit 150 by means of the drive circuit 164. The rear wheel 114r is driven by the motor 152, thereby causing the vehicle to run. Output signals provided from accelerator sensor 194 and vehicle speed sensor 196 are subjected to an arithmetic processing in the controller 149 and the electric power to be fed to the motor 152 is controlled in accordance with the operation of the accelerator grip 115a and the vehicle speed. In the power swing unit 150, the recess 151a is formed in the case body 151. The motor case 160 is connected to the recess 151a of the case body 151 to define the motor chamber 131. The rotating shaft 161 and stator coils 162 are disposed within the motor chamber 131 to mount the electric motor 152. The heat sink 166 is fixed to the motor case 160, and FETs 135 which constitute the drive circuit 164 are mounted to the heat sink 166. Consequently, the wiring 145 between the stator coils 162 and the drive circuit 164 can be shortened, and it is possible to attain a reduction of size because any special parts are not required for the mounting of the drive circuit 164. In the power swing unit 150, the motor case 160 is formed in the shape of a bottomed cylinder having a face for connection with the case body 151 at an axially intermediate portion of the rotating shaft 161. The heat sink 166 is provided in the motor case 160. In addition, the bearing 132, for the rotating shaft 161, and the rotation sensor 170 are provided within the motor case 160. Consequently, the number of parts can be decreased as a whole and it is possible to attain a further reduction of size. The stator coils 162 which constitute the stator are fixed to the motor case 160, so it is possible to mount the stator coils 162, the rotations sensor 170, etc. beforehand to the motor case 160. Thereafter, the case 160 is mounted on the case body 151 with the stator coils 162, etc. already mounted therein. Thus, this assembling operation is easy. In the power swing unit 150, moreover, the heat sink 166 is formed in a generally hexagonal shape in section, then FETs 135 which are provided in the drive circuit 164 are attached to the outer faces of the hexagon. Thereafter, the outer surface of the heat sink 166 is covered with the cover 165, and resin is filled between the cover 165 and the heat sink 166 to coat the FETs 135 and terminals 139. Therefore, it is possible to fix the FETs 135, etc. firmly and protect them effectively against dust and water. The stator coils 162 of the electric motor 152 and the drive circuit 164 are connected together through three bolts 142 which are inserted at equal intervals in the circumferential direction along the inner periphery of the heat sink 166. The bolts 142 are arranged in a distributive manner so as not to assume the lowest vertical position of the heat sink. Therefore, even in the event of stagnation of water which has entered the lower portion of the heat sink 166, no inconvenience, e.g. electrical contact with the water, will occur. Since the bolts 142 extend through the boss portion 165b of the cover 165 to keep the spacing from the fins 167 of the heat sink 166, it is not necessary to use collars or the like for insulation and hence it is possible to decrease the number of parts. Further, since the cover 165 is integrally formed with ribs 165b serving as swivel stop ribs for the terminals 138, the operation for connection of the terminals 138 is easy. Figure 8 illustrates a power unit for a motor vehicle according to another embodiment of the present invention. Figure 8 is an enlarged sectional view of a principal portion, in which the same portions as in the above embodiment are indicated by the same reference numerals and explanations thereof are omitted. In this embodiment, as shown in Figure 8, a heat sink 166 is formed integrally with a motor case 160. In the motor case 160, a bearing portion 160a is formed centrally in the axial direction, the heat sink 166 is formed on the right-hand side, and a cylindrical portion 160b which covers stator coils 162 is formed on the left-hand side. A bearing 32 is provided in the bearing portion 160a which supports a rotating shaft 161. A rotation sensor is disposed on the left-hand side of the bearing 132 in close proximity thereto. According to this embodiment, since the heat sink 166 is formed integrally with the motor case 160, it is possible to further decrease the number of parts, and the assembling operation can be accomplished very easily. In addition, since the rotation sensor 170 is disposed on the side opposite to the heat sink 166, it is possible to prevent the interference thereof and also possible to attain a further reduction of size. Figures 12 to 20 illustrate a further embodiment of the present invention. In this embodiment, the same members as in the above embodiments are indicated by the same reference numerals and explanations thereof will be omitted. In this embodiment, a motor case 160 is formed in the shape of a cylinder with right and left ends both being open. Coils 162 are each wound around a core 221, see Figure 21 relating to a still further embodiment as will be described later, which are disposed within the motor case 160 and fixed therein. As shown in detail in the drawings, three connecting terminals 521 are disposed on a right end face of the core 221 and positioned at equal intervals in the circumferential direction. The connecting terminals 521, with a nut 521a, see Figure 19, fixed to each of them, are connected to three terminals of the coils 162 which are Y-connected as is apparent also from the circuit diagram of Figure 22 explained previously. A fixing machine screw 255 is threadedly engaged with the nut 521a, and the connecting terminals 521 are each brought into conduction with a terminal 260 electrically through the fixing machine screw 255, as will be described later. A mounting member 210 is fixed to the right end opening of the motor case 160, and a heat sink 166 is attached to the mounting member 210 through a terminal plate member 240. The mounting member 210 has a Y shape comprising three spoke portions 211 and a boss portion 212 which are molded together integrally. The spoke portions 211 are each positioned between adjacent connecting terminals 521 and in this state the heat sink is fixed to the mounting member 210. A mounting boss 211a having a threaded hole is formed on a front end side of each spoke portion 211, and a through hole 212a for supporting a rotating shaft is formed in the boss portion 212. A rotating shaft 161 is inserted through the through hole 212a rotatably through a bearing 132. A magnetism sensitive element 170a, as illustrated in Figure 25, will be described later in connection with a still further embodiment. As also shown in Figures 16 to 20, the terminal plate 240 is disk-like and formed of an electrical insulating material. From the inner periphery of the terminal plate 240 three nut holder portions 241 project radially inwards at equal intervals. In each nut holder portion 241, there is formed a rectangular concave 241a which is open on the right-hand side thereof, and a slot 241b for registration is formed in a side wall portion on the counterclockwise side of the concave 241a. In the terminal plate 240, a square nut 250 is loosely fitted in the concave 241a of each nut holder portion 241, and a connecting bolt 251 which will be described later is brought into threaded engagement with the square nut 250 for mounting the associated terminal 260. The size of the concave 241a is larger than that of the square nut 250 to permit a predetermined wobbling motion of each nut 250. For example, if one side of the concave 241a is assumed to be 10, one side of the square nut 250 is set to 9.5 or so, and in this case, the diameter of an insertion hole formed in each terminal 260, which will be described below, is set to 6, while that of each connecting bolt 251 is set to 5. The concave 241a may be formed as a square through hole. As shown in Figures 17 to 20, the terminals 260 are each formed in a stepped shape using an electroconductive material, e.g. brass, by a pressing operation for example. Insertion holes 260a and 260b are formed in the stepped portions, respectively, and a lug 260c for registration is formed on the insertion hole 260a side. The lug 260c is fitted in the corresponding slot 241b to restrict the position of the terminal 260. The connecting bolt 251 engaged threadedly with each square nut 250 is inserted into the insertion hole 260a, and the fixing machine screw 255 engaged threadedly with the nut of each connecting terminal 521 is inserted into the insertion hole 260b. As shown in the drawings, the terminals 260 are connected for electrical conduction with the connecting terminals 521 of the electric motor 152 through the fixing machine screws 255. Further, as will be described below, the terminals 260 are also brought into electrical conduction with terminals 139 for power supply of the heat sink 166 through the connecting terminals 521, see Figure 20. As shown also in Figures 13 to 15, three power supply terminals 139 are disposed on a left end face of the heat sink 166 and positioned at equal intervals. The connecting bolts 251 and fixing bolts 299 are inserted through the end face from the right-hand side. As shown in Figure 20, the connecting bolts 251 come into threaded engagement with the square nuts 250 of the terminal plate 240 to bring the terminals 260 and the power supply terminals 139 into electrical conduction with each other. The fixing bolts 299 come into threaded engagement with the threaded holes formed in the bosses 211a of the spoke portions 211 of the mounting member 210 to fix the heat sink 166 to the mounting member 210, namely, the motor case 160. For mounting the heat sink 166 to the motor case 160 in this embodiment, first the lugs 260c of the terminals 260 are retained in the slots 241b formed in side walls of the concaves 241a of the terminal plate 240, on the right-hand side of the terminal plate. In this state the fixing machine screws 255 are inserted through the insertion holes 260b into threaded engagement with the nuts of the connecting terminals 521 of the electric motor 152 to hold the terminal plate 240 between the terminals 260 and the mounting member 210. At this time, the connecting terminals 521 and the terminals 260 conduct electrically and contact with each other as shown in Figure 20. Thereafter, the fixing bolts 299 and the connecting bolts 251 are inserted from the right-hand side of the mounting member 210 so that the bolts 299 are threadedly engaged with the threaded holes formed in the bosses 211a of the mounting member 210 and the bolts 251 are threadedly engaged with the square nuts 250 of the terminal plate 240. Consequently, the heat sink 166 is fixed to the motor case 160, namely, the mounting member 210, and as shown in the drawing, the terminals 260 and the power supply terminals 139 come into contact with each other while maintaining electrical connection. In this embodiment, as described above, the power supply terminals 139 of the heat sink 166 and the connecting terminals 521 of the electric motor 132 can be brought into electrical conduction with each other by means of the terminals 260 of the terminal plate 240 without the use of wiring. Consequently, the operation for the connection of wiring is not required at the time of mounting the heat sink 166 and hence the heat sink can be mounted easily. Figures 21 to 24 illustrate a still further embodiment of the present invention. The same elements as in the previous embodiments are indicated by the same reference numerals and explanations thereof will be omitted. According to this embodiment, a capacitor 168 is mounted along the inner periphery of a heat sink 166 by means of a mounting stay 681. As shown in detail in the drawings, the mounting stay 681 has an annular band portion 681a and a stopper portion 681b. The annular band portion 681a clamps the outer periphery of the capacitor 168 through a machine screw 683, while the stopper portion 681b is brought into engagement with a left end face of the capacitor 68. The mounting stay 681 is fixed to a right end face of the heat sink 166 at three points with machine screws 682 to mount the capacitor 168 to the heat sink 166. As is shown clearly in Figure 21, a right end face of the capacitor 168 is positioned more to the left than the right end face of the heat sink 166. In other words, the capacitor 168 is buried completely into the inner periphery portion of the heat sink 166. Further, the capacitor 168 is disposed in such a manner that connecting terminals 168a are positioned on the left-hand side, that is, the portion of the capacitor where the connecting terminals 168a are provided faces the left-hand side, see Figure 13. In this embodiment, as shown in Figures 23 and 24, a magnetism sensitive element 170a of a rotation sensor 170 is mounted to an annular sensor stay 710 with machine screws 712 and the sensor stay 710 is mounted with bolts 711. As is clear from Figure 23 and 24, the magnetism sensitive element 170a is coated with resin and projects at a predetermined height on the right-hand side, and the connecting terminals 168a of the capacitor 168 are positioned symmetrically with respect to the sensor stay 710. According to this embodiment, since the capacitor 168 is disposed so that the connecting terminals 168a face the electric motor 152 side, it is possible to prevent the connecting terminals 168a of the capacitor from coming into contact with other devices, etc. Besides, since the capacitor 168 is buried in the heat sink 166, it is possible to prevent its abutment with external devices. Further, since the left end face of the capacitor is retained by the stay, its leftward displacement can be prevented effectively. The capacitor 168 may be disposed in such a manner that a right end portion projects from the inner peripheral portion of the heat sink 166, as shown in Figure 25. Also in this case, the terminals 168a of the capacitor 168 can be prevented from contact with external devices because they face inwards. Other constructional points as well as the function and effect are the same as in the above embodiments, so explanations thereof are here omitted. The heat sink is fixed to the motor case integral with the case body and the switching elements which constitute the drive circuit are mounted to the heat sink. Thus, it is possible to shorten the wiring for connection between the drive circuit and the electric motor, and reduce the size of the unit. The switching elements-mounted portion of the heat sink is covered with the cover member and resin is filled between the cover member and the heat sink. Thus, it is possible to firmly fix the switching elements and wiring and protect the switching elements, etc. The heat sink, the bearing for the rotating shaft and the rotation sensor are mounted in a divided case which is divided from the case body in an intermediate position of the rotating shaft and the rotation sensor is disposed on the side axially opposite to the heat sink with the bearing positioned therebetween. Thus, it is possible to avoid interference with the heat sink and attain a further reduction of size. A construction is adopted wherein the stator is mounted to the divided case. Thus, it is possible to mount the stator beforehand to the divided case and hence the assembly thereof becomes easier. A construction is provided wherein the motor case and the heat sink are each provided with terminals. A plate member is disposed in a predetermined position between the motor case and the heat sink, and power supply terminals of the heat sink and connecting terminals of the motor case are rendered conductive with each other through terminals provided on the plate member. Thus, it is not necessary to use wiring and the mounting of the heat sink to the motor case can be easily accomplished. The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the scope of the invention, as defined by the following claims.

Claims: A power unit (150) for a motor vehicle having an electric motor (152), said power unit being characterized in that it comprises : a unit case with at least a portion of the unit case forming a motor case (160); a rotating shaft of the electric motor (152) being operatively connected for supplying power to an output shaft (161) supported rotatably relative to the unit case and said power of the electric motor (152) outputted from the output shaft (161) being transmitted to a driven wheel (114r) of said motor vehicle; a heat sink (166) operatively connected to said motor case (160), said heat sink including an outer periphery and an inner periphery, cooling fins (167) being formed on said inner periphery; and switching elements (135a-135f) for switching an electric current to be supplied to said electric motor (152) being mounted to said heat sink (166). The power unit according to claim 1, and further including a cover member (165) covering the switching elements (135a-135f) mounted on said heat sink (166) and resin (146) being filled between said cover member and said heat sink to fix the cover member to said heat sink and for fixing the heat sink to the motor case (160). The power unit according any one of claims 1 and 2, wherein said unit case is divided into said motor case (160) and a case body (151) in an axial direction of said rotating shaft (161) between end portions of the rotating shaft, a bearing (132) for rotatably supporting one end portion of said rotating shaft, a rotation sensor (170) for detecting the rotation of the rotating shaft; said bearing (132), said rotation sensor (170) and said heat sink (166) being mounted within said motor case (160); and said heat sink (166) being disposed on one side of said bearing (132) in the axial direction of the rotating shaft and said rotation sensor (170) being disposed on the other side of the bearing in the axial direction of the rotating shaft (161). The power unit according to claim 3, and further including a stator (162) of said electric motor (152) being fixed to said motor case (160), said stator (162) and said rotation sensor (170) being disposed adjacent to each other in the axial direction of said rotating shaft (161). The power unit according to claim 1, and further including connecting terminals (521) exposed on a heat sink side face of said motor case (160); a plate member (240) including terminals (260) being mounted to the motor case (160) in a predetermined position for supplying electrical current between said connecting terminals (521) and said terminals (260); power supply terminals (139) operatively positioned relative to said heat sink (166) and connected to said switching elements (135a-135f); and said heat sink (166) being mounted to said motor case (160) through said plate member (240) to render said power supply terminals (139) and said terminals (260) electrically conductive relative to each other. The power unit according to claim 1, wherein a capacitor (168) is mounted along an inner portion of the heat sink (166). The power unit according to claim 1, wherein said switching elements (135a-135f) are mounted on said outer periphery of the heat sink (166).

Inventors: CHO TOSHIYUKI, FUJII TAKAAKI, HONDA SATOSHI, KAWAGUCHI KENJI, MOTODATE SHOJI, TORIYAMA MASAYUKI, CHO, TOSHIYUKI, FUJII, TAKAAKI, HONDA, SATOSHI, KAWAGUCHI, KENJI, MOTODATE, SHOJI, TORIYAMA, MASAYUKI, Cho, Toshiyuki, c/o K.K. HONDA GIJUTSU KENKYUSHO, Fujii, Takaaki, c/o K.K. HONDA GIJUTSU KENKYUSHO, HONDA, SATOSHI, C/O K.K. HONDA GIJUTSU KENKYUSHO, KAWAGUCHI, KENJI, C/O K.K. HONDA GIJUTSU KENKYUSHO, MOTODATE, SHOJI, C/O K.K. HONDA GIJUTSU KENKYUSHO, TORIYAMA, MASAYUKI, C/O KK HONDA GIJUTSU KENKYUSHO
Applicants: HONDA MOTOR CO LTD, HONDA GIKEN KOGYO KABUSHIKI KAISHA
Application year: 1992
Main classification: B60L7
IPC codes: H02P6, B60L11, H02K29, H02K11, B60L7