Patent Publication Number: US-2016248292-A1

Title: Electronic control apparatus, motor control apparatus and electric fluid pump

Description:
TECHNICAL FIELD 
     The present invention relates to control apparatus such as electronic control apparatus, motor control apparatus and electric fluid motor. 
     BACKGROUND ART 
     Recently, with increase in demand for lower fuel consumption of motor vehicles, there is a tendency to use a motor such as brushless motor widely in various control mechanisms in the motor vehicles, and the motor is integrated with a drive control device for controlling the motor, into a compact unit. 
     For example, the function of idle stop is widely used in motor vehicles and the practical use of hybrid vehicles is spreading. In these vehicles, when an internal combustion engine is stopped, a mechanical fluid pump driven by the engine is also stopped. Therefore, another source for driving a fluid pump is required besides the internal combustion engine. Furthermore, electric vehicles and hybrid vehicles require a driving motor, its drive control apparatus and a cooling water pump for cooling a battery. From such a background, there is a tendency of the increasing use of electric fluid pump such as a pump including an impeller driven by an electric motor. 
     Recent electric fluid pumps are produced often in the form of an integrated unit integrated with a drive control section for supplying a controlled driving current to windings of the motor. The integration of the drive control section with the electric fluid pump is intended to minimize adverse influence of external noise by reducing the length of wiring between the windings and drive control section, to reduce the wiring between the windings and drive control section, to reduce the cost for wiring, to facilitate calibration between the pump section and the drive control section, and/or to improve operability and handling ease. 
     A Japanese Patent Document, JP 2010-144693A (Patent Document 1) shows an electric fluid pump including an impeller received in an pump chamber, a rotor received in a rotor chamber communicating with the pump chamber, a stator including windings received in a chamber separated liquid-tightly from the rotor chamber, a drive control section fixed to a motor housing made of resin, and a cover covering the drive control section and the motor section.
     Patent Document 1: JP2010-144693A (≈US2010/0158703A1)   

     SUMMARY OF THE INVENTION 
     In an electronic control apparatus such as an electric fluid pump including therein a drive control section integrally, the drive control section is mounted on a motor section formed by molding of synthetic resin, and covered by a metallic cover fastened to the motor section. The metallic cover of metallic material is employed to use as a radiator plate for dissipating heat generated in the drive control section, to the outside. The drive control section includes an inverter circuit including switching devices formed by insulated gate bipolar transistors (IGBTs), and the switching devices of the inverter circuit generate heat. The metallic cover is used to dissipate heat generated by these switching devices. 
     In the electric fluid pump of this type, static electric charge is created and accumulated to a level of a high voltage in the metallic cover. The static electricity of the high voltage may cause electric discharge impairing the function of electric devices in the drive control section inside the cover and even damage the electric devices in an extreme case. 
     Therefore, there is required measure for releasing the static charge accumulated in the cover, to a vehicle body, to avoid adverse influence of the static electricity on the electric devices. 
     As the measure to remove the electric charge accumulated in the cover, there are a method of providing, along the side surface of the electric fluid pump, a coated copper wire connecting the metallic cover  31  to a part of the internal combustion engine for grounding, and a method of providing, near the metallic cover, a discharge terminal connected to a ground side of the power supply. 
     However, in the case of the coated wire connecting the controller cover to part of the internal combustion engine for grounding, the durability is poor because of the coated wire exposed to the outside, and another protective member is required for protecting the coated wire in order to improve the durability. Therefore, this method increases the number of required component parts and the number of assembly steps, and causes an increase of the production cost. 
     In the case of the discharge terminal near metallic cover for grounding to the power supply ground, the accumulation of static charge to a predetermined threshold level is required and a serge noise at the time of discharge could impair the performance of the electric devices in the drive control section. 
     Furthermore, the complicated construction is disadvantageous to the motor control apparatus required to reduce the production cost by decreasing the number of component parts and the number of production steps. Accordingly, it is required to relieve the static charge from the metallic cover to the ground side with a simple construction without increasing the number of component parts. 
     The above-mentioned problem arises not only in the integrated electric fluid pump including the pump and the drive control section integrally as a unit, but also in an electronic control apparatus of a separate type including a control circuit section disposed in a casing. 
     It is an object of the present invention to provide a novel apparatus, such as electronic control apparatus, motor control apparatus and electric fluid pump, for relieving static charge from a metallic cover to a reference point serving as a ground, such as a vehicle body, with a simple construction. 
     According to the present invention, a conductive gasket is interposed between a joint surface of a resin housing and a joint surface of a metallic cover, and arranged to ground the cover electrically through the conductive gasket. 
     The conductive gasket has a function of serving as a gasket and a function of relieving static charge. 
    
    
     
       BRIEF EXPLANATION ON THE DRAWINGS 
         FIG. 1  is an axial sectional view of an electric fluid pump used for an internal combustion engine, to which the present invention is applied. 
         FIG. 2  is an enlarged sectional view showing a part of the electric fluid pump according to a first embodiment of the present invention. 
         FIG. 3  is an enlarged sectional view showing a joining state of a fastening bolt and a conductive gasket shown in  FIG. 2 . 
         FIG. 4  is a perspective view of the conductive gasket shown in  FIG. 3 . 
         FIG. 5  is a sectional view taken across a line A-A in  FIG. 4 . 
         FIG. 6  is a sectional view taken across a line B-B in  FIG. 4 . 
         FIG. 7  is a sectional view taken across a line C-C in  FIG. 4 . 
         FIG. 8  is a perspective view of an electronic control apparatus according to a second embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Following is explanation on embodiments according to the present invention, with reference to the drawings. However, the present invention is not limited to the following embodiments. Various modifications and applications are possible under the technical concept of the present invention, and included in the purview of the present invention. 
     First Embodiment 
     In the following embodiment, the present invention is applied to a motor control apparatus including an electric fluid pump and a drive control device united as a unit. However, the present invention is not limited to the motor control apparatus of this type. The present invention is applicable to various electronic control apparatus and to various motor control apparatus such as an electric power steering apparatus, for example. 
       FIG. 1  is a sectional view showing the overall structure of an electric fluid pump according to a first embodiment of the present invention, and  FIGS. 2-7  are views more in detail. The electric fluid pump shown in  FIG. 1  is a cooling pump which uses a cooling water as an operating fluid, and which is adapted to be incorporated in a cooling water circulating circuit connected with a heat exchanger in the form of a radiator. For example, this electric fluid pump can be used as water pump for supplying the cooling water to an internal combustion engine, a driving motor, an inverter, etc. in a hybrid vehicle. 
     The electric fluid pump  10  according to this embodiment is an assembly of a pump section  11 , a motor section  12  serving as a drive section for driving the pump section  11 , and a drive control section  13  for controlling the operation of motor section  12 . These sections  11 ,  12  and  13  are united as a single assembly. 
     The pump section  11  includes a pump housing  15  defining a pump chamber  14 , and an impeller  16  received rotatably in pump chamber  14 . 
     The pump housing  15  includes an inlet opening (not shown) opening into the pump chamber  14 , and an outlet opening (not shown) opening from a peripheral portion of pump chamber  14  to the outside of pump chamber  14 . The pump section  11  of this example is a centrifugal pump raising the pressure of the liquid in the radial direction by the rotation of impeller  16 . By the rotation of impeller  16 , the cooling water is sucked from the inlet opening into pump chamber  14 , and discharged under pressure from the outlet opening through a discharge passage on the outer circumferential side of impeller  16 . 
     Impeller  16  is a wheel having a plurality of vanes  17 . Impeller  16  is integral and coaxial with a rotor  18  of the motor section  12 . Impeller  16  is disposed in pump chamber  14 . Vanes  17  are arranged radially around a center axis of rotor  18 . Each vane  17  of this example extends radially outwards in a slanting manner that the vane  17  inclines to the direction opposite to the rotational direction of impeller  16 . As a whole, vanes  17  are arranged in a volute or swirl form. 
     The pump housing  15  is formed integrally with a movement limiting member  19  for limiting axial movement of the rotor  18  and impeller  16 . The movement limiting member  19  includes a center hole into which a first (left) end of a support shaft  20  of rotor  18  is inserted, so that the end of support shaft  20  is supported by the movement limiting member  19 . 
     The motor section  12  of this example is an inner rotor type brushless DC motor. Motor section  12  includes a stator  21  shaped like a hollow cylinder, the rotor  18  surrounded by stator  21 , a motor housing  23  defining a motor chamber  22  for enclosing the stator  21  ad rotor  18 , and the support shaft  20  provided in motor housing  23  and arranged to support the rotor  18  rotatably. 
     The motor housing  23  is a resin housing made of a synthetic resin. Stator  21  is formed integrally in motor housing  23  by insert molding. Similarly, the rotation shaft  20  is formed integrally by insert molding, in motor housing  23 . Motor housing  23  of the synthetic resin includes a cylindrical wall having a hollow cylindrical shape and surrounding the stator  21 , and a bottom or end  23 A closing one end of the hollow cylindrical shape formed by the cylindrical wall. In this example, the bottom  23 A has a shape like a circular plate and includes a center portion supporting a second (right) end of the rotation shaft  20  so that rotation shaft  20  stands upright from bottom  23 A. The second end of rotation shaft  20  is buried in the synthetic resin of bottom  23 A. 
     The stator  21  includes a plurality of windings  24  to produce magnetic flux on the inner circumferential side by receiving the supply of current. The rotor  18  includes a pole holding portion  25  and a shaft portion  26  as an integral unit. In this example, rotor  18  is formed integrally with impeller  16  by injection molding of synthetic resin, for example. The pole holding portion  25  includes permanent magnet(s). Pole holding portion  25  is firmly attached in by the synthetic resin in rotor  18 . Since rotor  18  contacts with the cooling water, the pole holding portion  25  is covered with the synthetic resin. As another example, the impeller  16  may be formed as a member separate from rotor  18 , and fastened to rotor  18 . 
     The pole holding portion  25  of rotor  18  is a cylindrical member disposed to confront radially the inside circumferential surface of stator  21  across a minute clearance (air gap). Pole holding portion  25  includes therein a plurality of magnetic poles (permanent magnets arranged so that the N and S poles are arranged alternately in the circumferential direction) corresponding to the plurality of the windings  24 . 
     The shaft portion  26  of rotor  18  serves as a shaft for transmitting a driving force to rotate impeller  16 . Shaft portion  26  is in the form of a hollow shaft coaxial with the pole holding portion  25 . Shaft portion  26  is formed with a first bearing hold portion holding a a first bearing  27  near the pole holding portion  25  and a second bearing hold portion holding a second bearing  28  near the impeller  16 . The first and second bearings  27  and  28  are attached to rotor  18 , and these bearings  27  and  28  are sliding bearings. The diameter of the inside circumference of each of the first and second bearing  27  and  28  is slightly greater than the diameter of support shaft  20 . 
     The support shaft  20  extends through a center axial hole formed in rotor  18  at the center. Rotor  18  is mounted rotatably on support shaft  20  through first and second bearings  27  and  28  which are supported fixedly by rotor  18 , and arranged to slide on support shaft  20 . There is a small clearance between the outside circumferential surface of support shaft  20  and the inside circumferential surfaces of first and second bearings  27  and  28 . 
     The stator  21  includes an iron core  29  formed integrally with a plurality of salient poles  29 A and the windings  24  wound around the salient poles  29   a , respectively, through bobbins of synthetic resins. The rotor  18  is located on the inner circumferential side of teeth formed, in the shape of circular arc, in the salient poles  29 A. Therefore, the rotor  18  is rotated by supplying electric power sequentially to the windings  24 . 
     The drive control section  13  is attached to the bottom  23 A of motor housing  23 . The bottom  23 A includes an inner surface facing toward rotor  18  and an outer surface facing in the opposite direction away from rotor  18 . Drive control section  13  is fastened to the outer surface of bottom  23 A. Drive control section  13  serves as a driver for supplying a driving current for the motor section  12 . Drive control section  13  includes a controller cover  31  defining a board receiving chamber  30 , and a control board  32  disposed in the board receiving chamber  30  and arranged to support electronic parts. The controller cover  31  is a metallic housing member made of a metallic material such as aluminum alloy, and adapted to serve as a radiator plate for dissipating heat generated in drive control section  13 , to the outside. 
     The control board  32  is a board on and in which electric or electronic device(s) (such as CPU and transistors) are mounted. These circuit elements and capacitor(s) form a converter and a control circuit. The converter receives power from a dc power source in the form of a battery and supplies ac power to the windings  24  of motor section  12 . The control circuit includes a microcomputer and other components, for controlling the on-off state of IGBT(s) of the converter. 
     A partition member  33  is disposed between stator  21  and rotor  18 . This partition member  33  is made of metal sheet having a thin section and shaped like a hallow cylinder extending straight from a first open end  33 A to a second open end  33 B in the axial direction of the rotor  18 . The first open end  33 A of partition member  33  is joined to a side portion  23 B of motor housing  23  located axially between stator  21  and impeller  16 , and the second open end  33 B of partition member  33  is buried in bottom  23 A of motor housing  23 . It is optional to employ an arrangement in which the first open end  33 A is also buried in the side portion  23 B of motor housing  23 . In either case, both of the first and second open ends  33 A and  33   b  are joined liquid-tightly to the synthetic resin of motor housing  23  directly. 
     Rotor  18  is disposed in partition member  33  as shown in  FIG. 1 , and a coolant such as cooling water is introduced into the inside of partition member  33 . The inside circumferential surface of the arched teeth formed in the salient poles  29 A of stator  21  are formed in the form of a circular arc conforming to the outside circumferential surface of partition member  33  and set in metal-to-metal contact with the outside circumferential surface of partition member  33 . Therefore, heat due to copper loss of the windings  24  and heat of the internal combustion engine incoming from the surrounding is conducted through the salient poles  29 A to partition member  33 , and further conducted to the cooling water for heat dissipation. 
     In the thus-constructed electric fluid pump  10 , static electricity is generated occasionally on or in the surface of pump  10 , and static charge is accumulated to a level of a high voltage in the controller cover  31 , as mentioned before. The buildup of high voltage static charge can impair the operation of an electric device in drive control section  13  and even damage the electric device in an extreme case if the high voltage static charge flows by discharge into the electric device. 
     As measure to remove the electric charge accumulated in controller cover  31  by the flow of excess charge to the main body of the motor vehicle serving as a ground, there are the method of providing, along the side surface of electric fluid pump  10 , a coated copper wire connected with the metallic controller cover  31 , and disposed in part of the internal combustion engine, and a method of providing, near the metallic controller cover  31 , a discharge terminal connected to a power supply ground, as mentioned before. 
     However, in the case of the coated wire connecting the controller cover  31  to part of the internal combustion engine for grounding, the durability is poor because of the coated wire exposed to the outside, and another protective member is required for protecting the coated wire in order to improve the durability. Therefore, this method increases the number of required component parts and the number of assembly steps, and causes an increase of the production cost. 
     In the case of the discharge terminal disposed near metallic controller cover  31  and connected to the power supply ground, the accumulation of static charge to a predetermined threshold level is required and a serge noise at the time of discharge could impair the performance of the electronic devices in the drive control section  13 . 
     Furthermore, the complicated construction is disadvantageous to the motor control apparatus required to reduce the production cost by decreasing the number of component parts and the number of production steps. Accordingly, it is required to relieve the static charge from metallic controller cover  31  to the ground side with a simple construction capable of reducing the number of component parts as much as possible. 
     The electric fluid pump of this type is disposed in the engine compartment of a motor vehicle. Therefore, rainwater and salt water entering the engine compartment may cause corrosion in the interface between the controller cover  31  and motor housing  23 . When minute corrosion proceeds and grows in the interface, the rain water and salt water may enter the chamber in which the control board  32  is disposed, and the inside of motor section  12 . Therefore, there arises a possibility of causing short circuit in the electric devices on control board  32  and the windings of motor section  12 . 
     Therefore, to prevent the ingress of water, generally a gasket is interposed between controller cover  31  and motor housing  23 . 
     According to this embodiment, the gasket is utilized, as measure to the problem, in a following construction. Specifically, a conductive gasket is interposed between a metallic housing member such as the metallic controller cover and a resin or plastic housing member such as the resin motor housing, and arranged to remove static electricity by connecting the metallic member with the ground such as the board&#39;s side grounding portion of the drive control section. 
     With the conductive gasket having the grounding function of allowing flow of static charge to the ground portion of the board of the drive control section, as well as the gasket function, the construction can reduce the number of component parts, simplify the construction and prevent influence of serge due to discharge with electric connection always relieving static charge from the controller cover to the ground side of the board. 
       FIG. 2  shows, in enlarged section, the joint structure between the controller cover  31  and motor housing  23  in the construction according to this embodiment.  FIG. 3  shows the joint structure more in detail. 
     As shown in  FIG. 2 , the resin motor housing  23  includes a housing joint portion  23 A, and the metallic controller cover  31  includes a cover joint portion  31 A. Either or both of the joint portions may be in the form of a flange. The housing joint portion  23 A of resin motor housing  23  abuts on and contacts with the cover joint portion  31 A of controller cover  31 . The housing joint portion  23 A and cover joint portion  31 A are joined together by at least one fastening bolt  34  which is made of metallic material and which is screwed into a metallic insert nut  35  provided in housing joint portion  23 A. 
     The insert nut  35  is inserted in the synthetic resin at the time of molding of the resin motor housing  23 . Insert nut  35  is made of metallic material to prevent a fastening force of the fastening bolt  34  from being applied directly to the housing joint portion  23 A of the synthetic resin, and thereby to prevent breakage of the housing joint portion  23 A. Moreover, the insert nut  35  serves as a conductor for the static electricity, as mentioned later. 
     A grounding conductive member or grounding terminal forming member  36  is also buried in the synthetic resin by molding at the time of forming the motor housing  23  by molding. The grounding conductive member  36  includes a board side grounding terminal  36 A (or bared end segment), a connector side grounding terminal  36 B (or bared end segment) and a buried connecting intermediate section or segment  36 C connecting both terminals  36 A and  36 B together. 
     The board side grounding terminal  36 A of grounding conductive member  36  is exposed from motor housing  23  and protruded to be connected with a power supply grounding terminal formed in control board  32 . The connector side grounding terminal  36 B of grounding conductive member  36  is exposed from a connecting portion  37  of motor housing  23  and adapted to be connected with the vehicle main body. The vehicle main body is used as the ground, and the grounding conductive member  36  is used as a conductor for grounding the control board  32 . 
       FIGS. 3 ˜ 7  specifically show the structure and method for joining motor housing  23  and controller cover  31  together. As shown in  FIG. 3 , the housing joint portion  23 A of motor housing  23  includes a joint surface which is adapted to be held in surface contact with a confronting joint surface of the cover joint portion  31 A of controller bovver  31 . A housing side gasket receiving portion  37  and a cover side gasket receiving portion  38  are formed around insert nut  35 , respectively in the joint surfaces of housing joint portion  23 A and cover joint portion  31 A. 
     The gasket receiving portions  37  and  38  form an annular space receiving the conductive gasket  39  characteristic of this embodiment. The conductive gasket  39  is constructed as shown in  FIGS. 4 ˜ 7 . 
     The conductive gasket  39  extends, in the form of a strip, along the mating joint surfaces of the housing joint portion  23 A and cover joining surface  31 A so as to form a closed figure as shown in  FIG. 4 , and includes a plurality of joint portions or hole portions  40  each defining a through hole and surrounding a corresponding one of the insert nuts  35 . The joint or hole portions  40  are distributed in the circumference of conductive gasket  39 .  FIG. 3  shows one of the joint portions  40 . 
     The conductive gasket  39  includes strip-like gasket segments and the joint or hole portions  40  (or boss portions), and the gasket segments and joint portions  40  are arranged alternately along the circumference. Each of the gasket segments is shaped like a strip and extends from one of the joint portions  40  to a next one. The conductive gasket  39  extends, to describe the closed figure of  FIG. 4 , circumferentially around the inside space  30  of the cover  31 . 
     The gasket receiving portions or grooves  37  and  38  formed, respectively, in the joint surfaces of housing joint portion  23 A and cover joint portion  31 A extend along the conductive gasket  39  and define a gasket receiving space extending circumferentially to form the closed figure as shown in  FIG. 4 , and having a shape in which the gasket segments and hole portions  40  are fit snugly. 
     Conductive gasket  39  includes a grounding base member  41  and a seal member  42  (or seal portion) as shown in  FIGS. 3 ˜ 7 . The grounding base member  41  is made of conductive metallic sheet such as copper sheet or aluminum sheet. The seal member  42  is made of material having a good sealing performance such as a rubber material, and formed or fixed on the outside surfaces of grounding base member  41 . The grounding base member  41  extends circumferentially along the joint surfaces of joint portions  23 A and  31 B of motor housing  23  and controller cover  31 , so as to form the closed figure of conductive gasket  39  as shown in  FIG. 4 . Seal member  42  is fixed by baking, for example, on the grounding base member  41 . 
     The seal member  42  of this example is made of rubber material selected from natural rubber, nitrile rubber, chloroprene rubber, ethylene propylene rubber, butyl rubber, silicone rubber, fluororubber, and perfluororubber. It is possible to use other seal material or other rubber material capable of preventing liquid such as water from entering the interface between motor housing  23  and controller cover  31 . 
     Reverting to  FIG. 3 , the insert nut  35  includes a larger portion  35 A having a larger cross sectional size or a larger diameter and a smaller portion  35 B having a smaller cross sectional size or a smaller diameter. The smaller portion  35 B of insert nut  35  is inserted or fit in a connection hole  44  (shown in  FIG. 5 ) of grounding base member  41  of conductive gasket  39 , to make electrical connection therebetween. Therefore, the fastening bolt  34  is electrically connected with the grounding base member  41  when the fastening bolt  34  is tightened into the insert nut  35 . 
     The internally threaded hole of insert nut  35  extends through the smaller portion  35 B and the larger portion  35 A. The insert nut  35  includes an annular shoulder surface extending around the threaded hole, between the smaller portion  35 B and the larger portion  35 A and facing toward the joint portion  31 A of cover  31 . In the example of  FIG. 3 , the smaller portion  35 B abuts on the joint portion  31 A of cover  31 , and is sandwiched between the joint portion  31 A and the larger portion  35 A of insert nut  35 . 
       FIG. 5  shows the conductive gasket  39  in section taken across a line A-A shown in  FIG. 4 . The grounding base member  41  is buried mostly in the material of seal member  42  formed or baked on the surfaces of grounding base member  41  and arranged to server as the gasket.  FIG. 5  is the sectional view of conductive gasket  39  at one of the joint portions  40  (or hole portions). Each of joint portions  40  surrounds the smaller portion  35 B of one of insert nuts  35 B, and has an annular shape. As shown in  FIG. 5 , the joint portion  40  includes an annular seal portion which is a part of the seal member  42 , and an annular conductive portion which is a part of the grounding base member  41 . The annular conductive portion of grounding base member  41  includes an outer circumferential portion buried in the annular seal portion and an inner circumferential portion which is projected and bared radially inwards from the annular seal portion and formed with one of connection holes  44 , at or near the center. The connection hole  44  of each joint portion  40  is arranged and shaped to receive the smaller portion  35 B of insert nut  35  to make electrical connection between the smaller portion  35 B of insert nut  35  and the inner circumferential portion of grounding base member  41 . Moreover, the bared inner circumferential portion of the annular conductive portion of grounding base member  41  abuts on the controller cover  31 , or is clamped between controller cover  31  and an annular portion of motor housing  23  surrounding the smaller portion  35 B of inset nut  35 , so that electric connection is established between controller cover  31  and grounding base member  41 . 
       FIG. 6  shows the conductive gasket  39  in section taken across a line B-B shown in  FIG. 4 . The grounding base member  41  is buried mostly in the material of seal member  42  formed or baked on the surfaces of grounding base member  41  and arranged to server as the gasket.  FIG. 6  is the sectional view of conductive gasket  39  at a connect portion formed with a connection terminal  43  to be connected with the board side grounding terminal  36 A of grounding conductive member  36 . As shown in  FIG. 6 , the connection terminal  43  is an extended portion of grounding base member  41 . The connection terminal  43  extends laterally from the gasket segment, for example, to a forward end portion formed with a connection hole  45  for receiving the board side grounding terminal  36 A. In the example of  FIG. 4 , the connection terminal  43  is formed on the inner side within the space enclosed by the closed figure of the conductive gasket  39 . The board side grounding terminal  36 A is inserted through the connection hole  45  and arranged to connect the grounding base member  41  and the grounding conductive member  36 . Thus, the fastening bolt  34  is connected electrically with the board side grounding terminal  36 A through insert nut  35 , the through hole  44  of grounding base member  41 , grounding base member  41 , connection terminal  43  and connection hole  45 . 
       FIG. 7  shows the conductive gasket  39  in section taken across a line C-C shown in  FIG. 4 . As shown in  FIG. 7 , the grounding base member  41  is buried in the material of seal member  42  formed or baked on the surfaces of grounding base member  41  and arranged to server as the gasket. The grounding base member  41  serves as a conductor for connecting the insert nut(s)  35  and the board side grounding terminal  36 A electrically. 
     The conductive gasket  39  can be produced by the following method. In this practical example, the grounding base member  41  is formed into the shape shown in  FIG. 4  by punching of a copper sheet with a press machine. The grounding base member  41  includes at least one connecting portion including the connecting terminal  43  as shown in  FIG. 4 . Therefore, the grounding base member  41  is formed by punching into the shape having at least one connecting portion  43 . Then, the sealing material such as the rubber material is baked and fixed to the punched copper sheet, to form the seal member  42  having the required shaped. Thereafter, the connecting terminal  43  is bent to the predetermined shape. Thus, the conductive gasket  39  is completed. 
     The thus-produced conductive gasket  39  is set in the gasket receiving portion  37  of motor housing  23  as shown in  FIG. 3 . In this case, the annular bared inner circumferential portion of conductive gasket  39  around the hole  44  at each joint portion is fit over the smaller portion  35 B of the insert nut  35  and connected electrically with the insert nut  35 . The connection hole  45  of the connection terminal  43  of the grounding base member  41  is fit over the board side grounding terminal  36 A of grounding conductive member  36  and electrically connected with grounding conductive member  36 . 
     In this state, the control board  32  is fixed and the controller cover  31  is put on the motor housing  23 . Then, the controller cover  31  is fastened firmly to motor housing  23  by tightening each fastening bolt  34  into the mating insert nut  35 . The connection terminal  43  of grounding base member  41  may be connected with the board side grounding terminal  36 A of grounding conductive member  36  on the upper side of control board  32 . In this case, the connection terminal  43  is connected with the board side grounding terminal  36 A after the board  32  is installed. 
     Therefore, the seal member  42  of conductive gasket  39  can serve as a seal between the mating joint surfaces of the fixing portions  23 A and  31 A of motor housing  23  and cover  31 . Furthermore, the grounding base member  41  of conductive gasket  39  can make electric connection between fastening bolts  34  and the board side grounding terminal  36 A through fastening bolts  34 , insert nuts  35 , the through holes  44  of grounding base member  41 , grounding base member  41 , connection terminal  43  and connection hole  45 . 
     When the thus-produced electric fluid pump  10  is installed in a vehicle, static electric charge is created in electric fluid pump  10  as mentioned before, and static electricity accumulated in the surface of controller cover  31  can always flow through the heads of fastening bolts  34  held in contact with controller cover  34 . 
     From the fastening bolts  34 , the charge of the static electricity flows into insert nuts  35 , and from insert nuts  35 , through the through holes  44  of grounding base member  41 , grounding base member  41 , connection terminal  43  and connection hole  45 , to the board side grounding terminal  36 A. From the board side grounding terminal  36 A, the static electricity flows through the buried connecting portion  3 C of grounding conductive member  36 , to the connector side grounding terminal  36 B. 
     With the conductive gasket  39  combining the function of the seal and the function of grounding, this embodiment can reduce the number of constituent parts and simplify the construction. 
     Furthermore, the grounding conductive member  36  is molded together with the motor section  12 . Therefore, there is no need for providing a protective member for protecting the grounding conductive member  36 , and it is possible to reduce the number of constituent parts and the number of steps in the assembly process. 
     Fastening bolts  34  are always connected electrically with the board side grounding terminal  36 A. Therefore, the static electricity accumulated in controller cover  31  can flow to the board side grounding terminal  36 A any time, so that this structure can prevent influence of serge due to a discharge. 
     In the illustrated practical example, the conductive gasket  39  has the structure composed of the grounding base member  41  and the seal member or seal material  42  fixed on the grounding base member  41  by baking. However, it is possible to produce the conductive gasket  39  by preparing a mixture of conductive metallic power such as silver or copper powder, and a rubber material such as silicone rubber at a predetermined mixing ratio, and forming the conductive gasket from the mixture by extrusion molding or hot press forming. The use of silicone rubber as a binder is advantageous for improving the heat resistance and the sealing performance. 
     The conductive metal powder can be connected electrically with the connection terminal  43  by burying the connecting terminal  43  in the seal member  42 . On the other hand, electrical connection with the controller cover  31  is made by direct contact with the controller cover  31 , without the need for additional connection terminal. 
     According to the first embodiment, the conductive gasket is interposed between the metallic cover and resin housing and arranged to connect the metallic cover with the member for grounding or with the board side grounding terminal to relieve the static electricity to the member for grounding. 
     With this arrangement, the conductive gasket can serve as the gasket and as the conductor for grounding. Therefore, it is possible to reduce the number of component parts, simplify the construction and prevent discharge and surge. 
     Second Embodiment 
       FIG. 8  shows a second embodiment of the present invention. In the second embodiment, a drive control section  53  is enclosed in a casing  50  as an electronic control apparatus not integrated with another apparatus such as a motor or a fluid pump whereas the drive control section  13  according to the first embodiment is integrated with the motor and/or the pump. The arrangement for transferring the static electricity toward the ground is basically the same as the arrangement in the first embodiment, so that the explanation is simplified. 
     The casing  50  of the electronic control apparatus shown in  FIG. 8  includes a controller housing  51  and a controller cover  52 . The drive control section  53  is disposed in the inside interspace formed between controller housing  51  and controller cover  52 . The drive control section  53  of this example is a driver for supplying a driving current to an electric component such as an electric motor, and includes a control board  54  including electric or electronic device(s). The controller housing  51  is made of a synthetic resin, and the controller cover  52  is a metallic cover made of a metallic material such as aluminum alloy. The metallic controller cover  52  serves as a radiator plate for dissipating heat generated in the drive control section  53 . 
     The control board  54  is a board on and in which electric or electronic device(s) (such as CPU and transistors) are mounted. These electric devices and capacitor(s) form a converter and a control circuit, for example. The converter receives power from a dc power source in the form of a battery and supplies ac power to the windings of a motor, for example. The control circuit includes a microcomputer and other components, for controlling the on-off state of IGBT(s) of the converter. 
     As shown in  FIG. 8 , the resin controller housing  51  includes a housing joint portion  51 A, and the metallic controller cover  52  includes a cover joint portion  52 A. At least one of the joint portions may be in the form of a flange. The housing joint portion  51 AA of resin controller housing  51  abuts on and contacts with the cover joint portion  52 A of controller cover  52 . The housing joint portion  51 A and cover joint portion  52 A are joined together by at least one fastening bolt  55  which is screwed into a metallic insert nut (not shown in  FIG. 8 ) provided in the controller housing  51 . As in the first embodiment, the housing side gasket receiving portion (not shown in  FIG. 8 ) and the cover side gasket receiving portion (not shown in  FIG. 8 ) are formed, respectively in the joint surfaces of housing joint portion  51 A and cover joint portion  52 A. 
     The conductive gasket  39  similar to that of the first embodiment is received in the annular space formed by the gasket receiving portions. The conductive gasket  39  extends along the mating joint surfaces of the housing joint portion  51 A and cover joining surface  52 A so as to form a closed figure as shown in  FIG. 4 , and includes a plurality of joint portions or hole portions each defining a through hole and surrounding a corresponding one of the insert nuts. The joint or hole portions are distributed in the circumference of conductive gasket  39 . 
     The conductive gasket  39  includes the gasket segments and the joint or hole portions  40  (or boss portions or joint portions), and the gasket segments and joint portions  40  are arranged alternately along the circumference. Each of the gasket segments is shaped like a strip and extends from one of the joint portions to the next. 
     The gasket receiving space defined by the gasket receiving portions formed, respectively, in the joint surfaces of housing joint portion  51 A and cover joint portion  52 A—extends along the circumference of conductive gasket  39  to form the closed figure and receives the gasket segments and the joint portions of conductive gasket  39 . 
     Conductive gasket  39  includes the grounding base member  41  of the shaped conductive metal sheet such as copper sheet or aluminum sheet, and the seal member or seal portion  42  as shown in  FIGS. 3 ˜ 7 . The seal member  42  is made of material having a good sealing performance such as a rubber material, and formed or fixed on the outside surfaces of grounding base member  41 . The grounding base member  41  extends circumferentially along the joint surfaces of joint portions  51 A and  52 A of controller motor housing  51  and controller cover  52 , so as to form the closed figure of conductive gasket  39  as shown in  FIG. 4 . Seal member  42  is fixed by baking, for example, on the thus-constructed grounding base member  41 . 
     As in the first embodiment shown in  FIG. 3 , each insert nut  35  includes the larger portion having a larger cross sectional size or a larger diameter and teh smaller portion having a smaller cross sectional size or a smaller diameter. The smaller portion of insert nut  35  is inserted or fit in the connection hole of grounding base member  41  of conductive gasket  39 , to make electrical connection therebetween. Therefore, the fastening bolt  55  is electrically connected with the grounding base member  41  when the fastening bolt  34  is tightened into the insert nut. 
     The grounding base member  41  is buried mostly in the material of seal member  42  which is formed or baked on the surfaces of grounding base member  41  and which is arranged to server as the gasket. As shown in  FIG. 6 , the connection terminal  43  of grounding base member  41  extends laterally from one of the gasket segments, and then extends upwards as viewed in  FIG. 6 , to the forward end portion bent and formed with the connection hole  45 . This connection hole  45  of the forward end portion of connection terminal  43  of grounding base member  41  of conductive gasket  39  is connected electrically with the board side grounding terminal (not shown in  FIG. 8 ) by a connection bolt  56  shown in  FIG. 8 . Thus, the controller cover  51  is electrically connected with the board side grounding terminal through the fastening bolts  55 , the insert nuts, the grounding base member  41 , and connection bolt(s)  56 . 
     When the thus-produced casing  50  of the electronic control apparatus is installed in a vehicle, static electric charge is created in casing  50  as mentioned before, and static electricity accumulated in the surface of controller cover  52  can always flow through the heads of fastening bolts  55  contacting with controller cover  52 . 
     From the fastening bolts  55 , the static electricity flows into the insert nuts, and further flows from the insert nuts, through the grounding base member  41 , and the connecting bolt  56 , to the board side grounding terminal of the grounding conductive member. 
     With the conductive gasket  39  combining the function of the seal and the function of grounding, the second embodiment can reduce the number of constituent parts and simplify the construction like the first embodiment. Furthermore, the fastening bolts  55  are always connected electrically with the board side grounding terminal. Therefore, the static electricity accumulated in controller cover  52  can flow to the board side grounding terminal any time, so that this structure can prevent influence of serge due to a discharge. 
     In the second embodiment, the motor drive control section for the motor is enclosed in the casing of the electronic control apparatus. However, it is optional to enclose any of various control circuit sections in the casing. 
     As explained above, an electronic control apparatus according to the present invention comprises a resin housing, a metallic cover, and a conductive gasket interposed between a joint surface of the resin housing and a joint surface of the metallic cover, and arranged to ground the metallic cover electrically through the conductive gasket, to a ground or to a grounding conductive member for electrical grounding or to a board side grounding terminal. 
     With this arrangement, the conductive gasket can serve as a gasket, and at the same time serve as an electric conductor for conducting static electricity to the ground or to the grounding conductive member. Therefore, it is possible to reduce the number of component parts, to simplify the construction and the production process, and to prevent the influence of serge due to discharge. 
     The present invention contains various modifications and variations, and the present invention is not limited to the illustrated embodiments. It is possible to omit part of the constructions of the illustrated embodiments, to add one or more additional features, to replace the features of the illustrated embodiments with different features or to replace one or more features of one embodiment with one or more features of another embodiment. 
     The electronic control apparatus according to the present invention may be a motor control apparatus comprising a resin motor housing enclosing a motor including a rotor and a stator, a drive control section including a circuit to supply a drive signal to winding(s) of the stator and thereby to control rotation of the rotor, and a metallic cover arranged to cover the drive control section and joined to the motor housing by at least one fastening bolt through a conductive gasket arranged to connect the metallic cover to a member for grounding. The electronic control apparatus according to the present invention may be an electric fluid pump comprising a pump section to transfer a fluid, a resin motor housing enclosing a motor to drive the pump section (an impeller of the pump section), a drive control section to control the motor, and a metallic cover arranged to cover the drive control section and joined to the motor housing by at least one fastening bolt through a conductive gasket arranged to connect the metallic cover to a member for grounding. 
     According to one aspect of the present invention, an electronic control apparatus (such as a motor control apparatus or an electric fluid pump) comprises: a housing of synthetic resin; a cover of metallic material, fixed to the housing by a fastening bolt; an electronic control section (which may include an electronic control board) enclosed in an interspace formed between the housing and the cover; and a conductive gasket interposed or clamped between a joint surface of the housing and a joint surface of the cover to fill a clearance between the mating joint surfaces, and arranged to ground the cover electrically through the conductive gasket. The conductive gaskets includes a grounding base member of conductive metallic material arranged to connect the cover with a grounding conductive member for electrical grounding, and a seal member or seal portion covering the grounding base member (and serving as a gasket or seal). The electronic control apparatus may further comprise the grounding conductive member formed or buried (by insert molding, for example) in the synthetic resin of the housing and connected electrically with the grounding base member. The electronic control apparatus may further comprise an insert nut made of a metallic material, formed fixedly in the synthetic resin of the housing, and arranged to join the cover to the housing with the fastening bolt screwed into an internally threaded hole of the insert nut, and to make electrical connection from the cover, through the fastening bolt and the insert nut, to the grounding base member of the conductive gasket. 
     The grounding base member of the conductive gasket may include an annular portion surrounding the fastening bolt (or an insert nut), and the seal member may include a first (upper) annular portion formed on a first (upper) surface of the annular portion of the grounding base member, and received in an annular groove formed in the joint surface of the cover and a second (lower) annular portion formed on a second (lower) surface of the annular portion of the grounding base member, and received in an annular groove formed in the joint surface of the housing, and the annular portion of the grounding base member may include an outer circumferential region buried in the synthetic resin between the first and second annular portions of the seal member, and an inner circumferential region bared from the synthetic resin of the seal member and clamped between the cover and the housing to make electrical connection between the cover and the grounding base member. In the example of  FIG. 3 , the bared inner circumferential region of the annular portion of the grounding base member ( 41 ) is clamped directly between the joint portion ( 31 A) of the cover ( 31 ) and the joint portion ( 23 A) of the housing ( 23 ). The electronic control section may include a control board supported by the housing and covered by the cover, and the electronic control apparatus may further comprise the grounding conductive member ( 36 ) including a board side grounding terminal ( 36 A) bared from the synthetic resin of the housing, and connected with the control board, an intermediate buried segment ( 36 C) buried in the synthetic resin of the housing and a ground side terminal ( 36 B) adapted to be connected with a predetermined member serving as a ground, and the grounding base member of the conductive gasket may include a connecting projection connected with the board side grounding terminal of the grounding conductive member.