Patent Publication Number: US-2015086405-A1

Title: Electric oil pump

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 U.S.C. §119 to Japanese Patent Application 2013-195803, filed on Sep. 20, 2013, the entire content of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     This disclosure relates to an electric oil pump for discharging oil. 
     BACKGROUND DISCUSSION 
     Conventionally, an electric oil pump has been used for controlling a hydraulically driven device driven according to oil pressure or for supplying lubricant oil to lubricate a mechanical device, etc. Further, in some arrangements provided with a main oil pump (mechanical), an auxiliary pump (electric) is used as an oil pressure source for use in an idling stop and an EV run. In case such an electric oil pump is used in a vehicle, from the viewpoints of space saving, weight reduction and cost reduction, it is conceivable to configure a single electric oil pump to provide supplying of lubricant oil even if oil pressure supply is needed for a plurality of portions (e.g. Patent Document 1: JPH07-243385). 
     In a variable displacement type pump disclosed in Patent Document 1, oil discharged from its discharge-side opening is circulated temporarily to a pump discharge-side pressure chamber formed outside a pump body. The downstream side of this pump discharge-side pressure chamber is communicated to a pump discharge-side passage provided in the pump body. Therefore, oil discharged from the discharge-side opening of the variable displacement pump is temporarily circulated to the outside from the pump body and then returned to the pump body. Further, the oil returned to the pump discharge-side passage is distributed to a passage for supplying to a power steering device through a metering orifice and a passage for supplying to a tank through a spool-type switching valve. 
     SUMMARY 
     With the technique disclosed in Patent Document 1, oil discharged from a discharge-side opening is circulated to a pump discharge-side pressure chamber provided outside a pump body. For this reason, although a single electric oil pump is used for supplying oil from the viewpoints of space saving, weight reduction and cost reduction, there inevitably occurs enlargement of the outer size due to the presence of the multiple oil passages. Thus, degree of freedom in disposing is small and the layout is limited. Also, the mass is increased. 
     In view of the above-described problem, a need thus exists for an electric oil pump which is capable of realizing space saving and weight reduction. 
     According to a characterizing feature of an electric oil pump relating to this disclosure, the pump comprises: 
     a rotor driven to rotate by a motor; and 
     a pump body having:
         a pump chamber accommodating the rotor;   an intake port for introducing oil into the pump chamber according to rotation of the rotor;   a discharge port for discharging oil from the pump chamber according to rotation of the rotor;   a first discharge passage communicated to a first communication hole provided in the discharge port and circulating oil discharged from the discharge port, the first discharge passage having a smaller cross sectional area than the discharge port; and   a second discharge passage communicated to a second communication hole provided in the discharge port separately from the first communication hole and circulating oil discharged from the discharge port, the second discharge passage having a smaller cross sectional area than the discharge port.       

    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The foregoing and additional features and characteristics of this disclosure will become more apparent from the following detailed description considered with the reference to the accompanying drawings, wherein: 
         FIG. 1A  is a view schematically showing a configuration of a hydraulic system having an electric oil pump, 
         FIG. 1B  is a view schematically showing a power source for EV run, 
         FIG. 2  is a view schematically showing the electric oil pump, 
         FIG. 3  is a view schematically showing a second check valve relating to a further embodiment, and 
         FIG. 4  is a view schematically showing a second check valve relating to a further embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     An electric oil pump disclosed here is configured to be capable of supplying oil pressure to a hydraulically driven device driven hydraulically and capable also of supplying lubricant oil to mechanical components. Next, the electric oil pump  1  relating to the present embodiment will be described. In this embodiment, there will be described an exemplary case in which the electric oil pump  1  is provided in an automatic speed changer mounted in e.g. a hybrid vehicle.  FIG. 1A  is a view schematically showing a configuration of a hydraulic system  100  incorporating the electric oil pump  1  provided in a vehicle.  FIG. 1B  is a view schematically showing a drive motor M as a power source for EV run. 
     As shown in  FIG. 1A , the hydraulic system  100  includes the electric oil pump  1 , an engine  2 , a gear unit  3 , a mechanical oil pump  4 , an oil pan  5 , a forward traveling clutch  6 , a hydraulic circuit  8 , and a check valve  9 . The engine  2  constitutes a power source of the vehicle and outputs a rotational power with combustion of a fuel such as gasoline. The rotational power of the engine  2  is transmitted to an automatic speed changer A. As shown in  FIG. 1B , the drive motor M is a power source for EV run and outputs a rotational power with electric power stored in e.g. a battery. The rotational power of the drive motor M is transmitted to wheels  7 . 
     The gear unit  3  has multiple gear positions providing different gear ratios and is configured such that the gear position is automatically changed according to a traveling state (e.g. according to a traveling speed of the vehicle or an amount of stepping on an accelerator, etc.). The rotational power of the engine  2  is transmitted to a gear position via a torque converter and the forward traveling clutch  6  and the gear position is changed as well. The output from the gear unit  3  is transmitted via an output shaft  3 A to some of the wheels  7  which are mounted on the front portion of the vehicle. 
     The mechanical oil pump  4  is driven to rotate by the rotational power of the engine  2 , thereby to supply oil stored in the oil pan  5  as lubricant oil via a discharge passage  4 A to the gear unit  3  and also to provide an engaging oil pressure via a discharge passage  4 B to the forward traveling clutch  6  (clutch engaged at the time of start of the vehicle). With this arrangement, during an operation of the engine  2 , oil can be supplied to the gear unit  3  and the forward traveling clutch  6 . 
     On the other hand, the vehicle mounting the present hydraulic system  100  can effect an EV run. For this reason, when the vehicle makes a stop at a traffic light or required power can be supplied by the drive motor M, the operation of the engine  2  is stopped and the mechanical pump  4  too is stopped. Therefore, the supply of oil to the gear unit  3  and the forward traveling clutch  6  will be stopped also. As a result, with stop of supply of oil pressure to the forward clutch  6 , the forward traveling clutch  6  will be rendered into a completely disengaged state. When traveling of the vehicle is to be resumed under this condition, the engine  2  will restart its operation, thereby to rotate the oil pump  4 , in which case an oil pressure needs to be fed to the forward traveling clutch  6 . In such a case like this, as the forward traveling clutch  6  is now under the completely disengaged state, a certain period will be required until establishment of engagement of this forward traveling clutch  6 . Further, if the engagement is tried hasteningly, this may cause a significant shock at the time of engagement. 
     Then, the electric oil pump  1  disclosed here is configured as follows. Namely, for the purpose of shortening the period required for establishment of engagement of the forward traveling clutch  6  and preventing the engagement shock occurring at the time of release of idling stop from becoming too large, during stop of the engine  4  at the time of idling stop, oil is supplied supplementarily to the forward traveling clutch  6  so as to maintain this clutch  6  under the engaged state and also oil as lubricant oil is supplied to the gear unit  3  at the time of EV run. Next, the electric oil pump  1  will be explained with reference to the drawings. 
       FIG. 2  is a view schematically showing the electric oil pump  1 . Here, the electric oil pump  1  relating to the present embodiment is configured as a trochoid pump which per se is known. Therefore, the following description will be provided on the assumption of the electric oil pump  1  being a trochoid pump. As shown in  FIG. 2 , the electric oil pump  1  relating to the present embodiment includes a rotor  10  and a pump body  20 . 
     The rotor  10  is driven to rotate by a motor  13 . The motor  13  is rotated with electric energy supplied from the battery during idling stop of the engine  2 , and a resultant rotational power of the motor  13  is inputted to a rotor shaft  11  mounted at the radially center portion of the rotor  10 . In association with rotation of this rotor shaft  11 , the rotor  10  is driven to rotate. The rotor  10  includes a plurality of outer teeth  10 A in its outer circumferential face and is rotated about the axis of the rotor shaft  11 . The outer teeth  10 A of the rotor  10  have a tooth profile according to a trochoid curve or a cycloid curve. 
     On the radially outer side of the rotor  10 , an outer rotor  12  is provided. The outer rotor  12  has an annular shape having a plurality of inner teeth  12 A to mesh with the outer teeth  10 A of the rotor  10  and the outer rotor  12  is rotated about a rotational axis offset from the rotational axis of the rotor  10 . The inner teeth  12 A of the outer rotor  12  are provided in a number one more than the number of the outer teeth  10 A of the rotor  10  and these inner teeth  12 A have a tooth profile to come into contact with the outer teeth  10 A of the rotor  10  when the outer rotor  12  is rotated. Therefore, the outer rotor  12  defines a predetermined space on the radially inner side thereof and in this space, the rotor  10  is accommodated. In the instant embodiment, this space corresponds to “a pump chamber  30 ” disclosed here. And, this pump chamber  30  is formed in the pump body  20 . Further, as the rotor  10  is accommodated in the pump chamber  30 , a predetermined gap Q is formed between the outer teeth  10 A and the inner teeth  12 A. 
     Further, the pump body  20  forms an intake port  40  and a discharge port  50 . The intake port  40  is an opening formed in a wall portion  20 A of the pump body  20 . Specifically, the intake port  40  is provided in a wall portion  20 A of the inner wall of the pump body  20 , which wall portion  20 A is in opposition to an axial end face of the outer rotor  12 , and along the radial direction of the outer rotor  12 . From this intake port  40 , oil is introduced into the pump chamber  30  in association with rotation of the rotor  10 . As described above, the outer teeth  10 A and the inner teeth  12 A define therebetween the predetermined gap Q, and the oil is introduced into this gap Q with rotation of the rotor  10 . 
     The intake port  40  is communicated to an intake passage  41  which circulates oil from the oil pan  5 . And, this intake passage  41  too is formed in the pump body  20 . 
     Like the intake port  40 , the discharge port  50  too is constituted of an opening defined in the wall portion  20 A of the pump body  20 . Specifically, the discharge port  50  is provided in the wall portion  20 A of the inner wall of the pump body  20 , which wall portion is in opposition to the axial end face of the outer rotor  12 , and along the radial direction of the outer rotor  12 . In the instant embodiment, the discharge port  50  is provided in the wall portion  20   a  on the side where the intake port  40  is provided. That is, the intake port  40  and the discharge port  50  are provided in the wall portion  20 A oriented in the same direction. Further, the opening constituting the discharge port  50  is spaced from the opening constituting the intake port  40  and along the radial direction of the outer rotor  12 . From this discharge port  50 , oil is discharged from the pump chamber  30  in association with rotation of the rotor  10 . That is, from the discharge port  50 , oil introduced through the intake port  40  is discharged from the predetermined gap Q formed between the outer teeth  10 A and the inner teeth  12 A. 
     A first discharge passage  60  circulates oil discharged from the discharge port  50 . Here, the discharge port  50  forms a first communication hole  52  constituted of an opening hole. The first discharge passage  60  is communicated via this first communication hole  52  to the discharge port  50 . And, this first discharge passage  60  is formed in the pump body  20 . The oil circulated through the first discharge passage  60  is supplied to the forward traveling clutch  6  described above. More particularly, the oil is circulated to the forward traveling clutch  6  via a discharge passage  61  and a discharge passage  4 B (see  FIG. 1A ) which are formed outside the pump body  20 . And, this first discharge passage  60  has a smaller cross sectional area than the discharge port  50 . 
     A second discharge passage  70  circulates oil discharged from the discharge port  50 . Further, the discharge port  50  defines a second communication hole  54  constituted of an opening hole. The second discharge passage  70  is communicated via this second communication hole  54  to the discharge port  50 . This second discharge passage  70  too is formed in the pump body  20 . Oil circulated through the second discharge passage  70  is supplied as lubricant oil to the gear unit  3  described above. More specifically, the oil is circulated to the gear unit  3  via a discharge passage  71  and the discharge passage  4 A (see  FIG. 1A ) which are provided outside the pump body  20 . This second discharge passage  70  has a smaller cross sectional area than the discharge port  50 . 
     In the instant embodiment, in the discharge port  50 , the first communication hole  52  and the second communication hole  54  are provided separately. Being provided separately means that the first communication hole  52  and the second communication hole  54  are not used together. Therefore, the first discharge passage  60  and the second discharge passage  70  are branched on the downstream side of the discharge port  50 . Rather, these passages  60 ,  70  are branched directly from the discharge port  50 . 
     By forming the first communication hole  52  and the second communication hole  54  separately inside the pump body, it is possible to form the first discharge passage  60  and the second discharge passage  70  as shortest possible passages in correspondence with the disposing positions of the discharge passage  61  and the discharge passage  71 . Therefore, the manufacture of the pump body  20  can be facilitated, so that manufacture cost can be reduced. 
     Further, the first discharge passage  60  and the second discharge passage  70  are formed to extend to joining faces of the pump body  20  to destinations of oil supply. Here, the “destinations of oil supply” are the forward traveling clutch  6  and the gear unit  3 . And, the “joining faces” correspond to joining faces  150 ,  151  relative to the forward traveling clutch  6  and the gear unit  3 . Therefore, the first discharge passage  60  and the second discharge passage  70  are formed to extend to the joining faces  150 ,  151  included in the pump body  20 . 
     Here, as described hereinbefore, this electric oil pump  1  is used for supplying oil to the gear unit  3  and the forward traveling clutch  6  when the mechanical pump  4  is stopped. For this reason, during an operation of the mechanical pump  4 , a sufficient amount of oil is supplied from the mechanical pump  4  to the gear unit  3  and the forward traveling clutch  6 , so that operation of the electric oil pump  1  will be stopped. As shown in  FIG. 1A  and  FIG. 2 , the first discharge passage  60  of the electric oil pump  1  is provided to communicate via the discharge passage  61  to the discharge passage  4 C of the mechanical pump  4  and the second discharge passage  70  of the electric oil pump  1  is provided to communicate via the discharge passage  71  to the discharge passage  4 A provided on the downstream side of the hydraulic circuit  8 . Therefore, in order to prevent oil discharged from the mechanical pump  4  from entering the electric oil pump  1  during stop of operation of this pump  1 , the first discharge passage  60  incorporates a first check valve  65  and the second discharge passage  70  incorporates a second check valve  75 . 
     The first check valve  65  is opened/closed according to a pressure of oil discharged from the discharge port  50 . The first check valve  65  includes a spring  66 , a steel ball  67  and a cage  68 . The cage  68  is provided as a tubular member having a groove portion or an opening extending along the axial direction and the cage  68  is disposed to surround the spring  66  and the steel ball  67 . When the pressure of oil discharged from the discharge port  50  is greater than an urging force of the spring  66 , a gap is formed between the steel ball  67  and a tubular member  99 , which constitutes a valve-opened state of the first check valve  65 . On the other hand, when the pressure of oil discharged from the discharge port  50  is smaller than the urging force of the spring  66 , no gap is formed between the steel ball  67  and the tubular member  99 , which constitutes a valve-closed state of the first check valve  65 . With this, inflow of oil discharged from the mechanical pump  4  during stop of operation of the electric oil pump  1  can be prevented. 
     In the instant embodiment, the first check valve  65  incorporated in the first discharge passage  60  is fixed by a leading end portion of a fixing screw  90  which advances into the first discharge passage  60  through an opening hole  23  defined in the pump body  20 . Preferably, the axis of the opening hole  23  is disposed orthogonal to at least a portion of the first discharge passage  60  (a portion of the first discharge passage  60  upstream the opening hole  23 , which will be referred to “a first discharge passage upstream portion  69 ” hereinafter). Still preferably, the axis is disposed be orthogonal at the vicinity of the shank  91  of the fixing screw  90  advanced into the opening hole  23 . Further, in the instant embodiment, the first check valve  65  is fixed by the fixing screw  90  via a tubular member  99  formed of a tubular iron member. 
     In the instant embodiment, the first discharge passage  60  (the first discharge passage upstream portion  69 ) merges with the opening hole  23  orthogonally. Also, the fixing screw  90  supports and fixes the first check valve  65  via the tubular member  99 . In the opening hole  23 , an outer oil passage  93  and an inner oil passage  95  are formed for allowing oil introduced into the opening hole  23  from the first discharge passage  60  (the first discharge passage upstream portion  69 ) to circulate toward the first check valve  65 . 
     The outer oil passage  93  is provided in a tubular form between an outer circumferential face  91 A of the shank  91  of the fixing screw  90  and an inner circumferential face  60 A of the first discharge passage  60 . The outer circumferential face  91 A of the shank  91  of the fixing screw  90  refers to the surface of the advancing portion of the fixing screw  90  advancing into the opening hole  23 . The inner circumferential face  60 A of the first discharge passage  60  refers to the inner circumferential face of the first discharge passage  60  merged with the opening hole  23 . The outside diameter of the shank  91  of the fixing screw  90  is formed smaller than the inside diameter of the first discharge passage  60  into which the fixing screw  90  advances. Therefore, at least a tubular gap is present between the outer circumferential face  91 A and the inner circumferential face  60 A. This tubular gap corresponds to the outer oil passage  93 . Oil discharged from the discharge port  50  first enters this outer oil passage  93 . 
     The inner oil passage  95  is communicated to the outer oil passage  93  via a communication portion  97  formed in the shank  91  on its radially inner side. The communication portion  97  refers to a portion which establishes communication between the inner oil passage  95  and the outer oil passage  93 . In the instant embodiment, the communication portion corresponds to a through hole extending radially through the shank  91 . In particular, in this embodiment, as shown in  FIG. 2 , there are formed communication portions  97  opposed to each other along the radial direction. And, such communication portions  97  are formed at positions axially different from each other. With this, the oil introduced into the outer oil passage  93  flows into the inner oil passage  95  and can then flow into the first check valve  65 . With this, since the fixing screw  90  for fixing the first check valve  65  can be used as an oil passage, the electric oil pump  1  can be formed compact, in comparison with a case providing an oil passage separately. 
     The second check valve  75  is opened/closed according to a pressure of oil discharged from the discharge port  50 . The second check valve  75  relating to the instant embodiment includes a spring  76 , a steel ball  77 , a cage  78  and a bush  79 . The cage  78  is provided as a tubular member having a groove portion or an opening extending along the axial direction and the cage  78  is disposed to surround the spring  76  and the steel ball  77 . The bush  79  is formed of iron. When the pressure of oil discharged from the discharge port  50  is greater than an urging force of the spring  76 , a gap is formed between the steel ball  77  and the bush  79 , which constitutes a valve-opened state of the second check valve  75 . On the other hand, when the pressure of oil discharged from the discharge port  50  is smaller than the urging force of the spring  76 , no gap is formed between the steel ball  77  and the bush  79 , which constitutes a valve-closed state of the second check valve  75 . With this, inflow of oil discharged from the mechanical pump  4  into the electric oil pump  1  during stop of operation of the electric oil pump  1  can be prevented. 
     In the instant embodiment, the second discharge passage  70  incorporates, on the downstream side of the second check valve  75 , an orifice  80  for distributing an amount of oil to the first discharge passage  60  and an amount of oil to the second discharge passage  70 . Here, oil circulating through the second discharge passage  70  is used as lubricant oil. Therefore, the aperture area of the orifice  80  will be set according to an amount of oil required by the gear unit  3  to which this lubricant oil is to be supplied and an oil pressure required by the forward traveling clutch  6 . This arrangement eliminates need for providing the orifice  80  outside the pump body  20 , so that the hydraulic system  100  having the electric oil pump  1  can be formed compact. 
     Further, this orifice  80  is provided in the form of a unit having a predetermined thickness T in its oil flowing direction. And, this unit will be pressed in from the outer side of the pump body  20  toward the second check valve  75 . In such case, preferably, the unit will be pressed in so that e.g. a portion of the predetermined thickness T of the unit projects from the pump body  20 . With this pressing-in, the projecting remaining portion (e.g. a half portion of the thickness T) can be used for positioning when the pump body  20  is assembled. 
     As described above, according to this disclosure, since the first discharge passage  60  and the second discharge passage  70  can be provided inside the pump body  20 , the piping to the discharge passage  61  and the discharge passage  71  to which the first discharge passage  60  and the second discharge passage  70  are connected respectively can be formed compact. Therefore, it is possible to realize an electric oil pump  1  achieving space saving and weight reduction. Further, since such first discharge passage  60  and the second discharge passage  70  are provided inside the pump body  20 , there will occur no interference with any devices present around the electric oil pump  1 . Therefore, the degree of freedom in the disposing position of the electric oil pump  1  and the degree of freedom in the layouts of the first discharge passage  60  and the second discharge passage  70  can be improved. 
     OTHER EMBODIMENTS  
     In the foregoing embodiment, it was explained that the electric oil pump  1  is a trochoid pump. However, the application of this disclosure is not limited thereto. It is possible as a matter of course to configure the pump as any other pump than a trochoid pump, as long as such other pump too is driven to rotate by electric energy. 
     In the foregoing embodiment, it was explained that the first discharge passage  60  incorporates the first check valve  65  and the second discharge passage  70  incorporates the second check valve  75 . However, the application of this disclosure is not limited thereto. It is possible as a matter of course to configure the first discharge passage  60  without the first check valve  65  and to configure the second discharge passage  70  without the second check valve  75 . In such case, preferably, the respective check valves may be provided outside the pump body  20 . Further, it is also possible as a matter of course to provide a check valve in only one of the first discharge passage  60  and the second discharge passage  70  and to provide the other check valve outside the pump body  20 . 
     In the foregoing embodiment, it was explained that the orifice  80  is pressed into the pump body  20 . However, the application of this disclosure is not limited thereto. As shown in  FIG. 3  for instance, it is also possible to employ an arrangement of fastening it with a screw. In such case, preferably, in order to prevent e.g. deformation of the cage  78  formed as a resin member due to excessive fastening of the screw, the unit of the orifice  80  is provided with a flange portion  80   a  having a seat face which comes into contact with the pump body  20 . With this, it becomes possible to prevent deformation, etc. of the cage  78 . 
     In the foregoing embodiment, it was explained that the second discharge passage  70  has the orifice  80  on the downstream side of the second check valve  75 . However, the application of the present invention is not limited thereto. It is also possible as a matter of course not to provide the orifice  80  on the downstream side of the second check valve  75 . 
     Further, as shown in  FIG. 4 , it is also possible to provide the orifice  80  on the side of the bush  79 . In this case too, the oil amount can be adjusted appropriately. And, if a fit-in portion  78   a  is formed in the cage  78  for allowing snap-fitting of the cage  78  to the pump body  20 , the number of components can be restricted. 
     In the foregoing embodiment, it was explained that the first check valve  65  is fixed by the fixing screw  90 . However, the application of this disclosure is not limited thereto. For instance, it is also possible as a matter of course to configure the first check valve  65  in a different form. 
     Further, it was explained that the outer oil passage  93  and the inner oil passage  95  are formed in the vicinity of the fixing screw  90 . However, the application of this disclosure is not limited thereto. For instance, it is also possible to configure such that by merging the first discharge passage  60  in the vicinity of the tubular member  99 , both the outer oil passage  93  and the inner oil passage  95  are omitted. Further, it is also possible to provide only one of the outer oil passage  93  and the inner oil passage  95 . 
     Further, in the foregoing embodiment, it was explained that the axis of the opening hole  23  is set preferably orthogonal to at least a portion of the first discharge passage  60 . However, the application of this disclosure is not limited thereto. It is also possible as a matter of course to provide the axis of the opening hole  23  not orthogonal relative to the first discharge passage  60 . 
     Further, in the foregoing embodiment, it was explained that the first check valve  65  is fixed by the fixing screw  90  via the tubular member  99 . However, the application of this disclosure is not limited thereto. It is also possible as a matter of course to fix the first check valve  65  by the fixing screw  90 , without using the tubular member  99 . 
     Further, in the foregoing embodiment, it was explained that the communication portion  97  is a portion which establishes communication between the inner oil passage  95  and the outer oil passage  93  and that this portion corresponds to a through hole which radially extends through the shank  91  of the fixing screw  90 . However, the application of this disclosure is not limited thereto. Namely, it is also possible as a matter of course to configure the communication portion  97  not as a through hole, but as a groove portion. 
     Further, in the foregoing embodiment, it was explained that the communication portions  97  are formed in opposition to each other along the radial direction and at positions axially different from each other. However, the application of this disclosure is not limited thereto. The fixing screw  90  may be provided with only one communication portion  97 . Further alternatively, it is also possible as a matter of course to provide the communication portions at respective positions thereof in agreement with each other along the axial direction of the fixing screw  90 . 
     In the foregoing embodiment, it was explained that the first check valve  65  is fixed by the fixing screw  90  and the orifice  80  is provided on the downstream side of the second check valve  75 . However, the application of this disclosure is not limited thereto. It is also possible as a matter of course to configure such that the orifice  80  is provided on the downstream side of the first check valve  65  and the second check valve  75  is fixed by the fixing screw  90 . 
     This disclosure may be implemented in an electric oil pump for discharging oil. And, as the destination of oil supply, aside from the gear unit, a power steering unit, a shock absorber unit, etc. may be used as such. 
     As described above, according to a characterizing feature of an electric oil pump relating to this disclosure, the pump comprises: 
     a rotor driven to rotate by a motor; and 
     a pump body having:
         a pump chamber accommodating the rotor;   an intake port for introducing oil into the pump chamber according to rotation of the rotor;   a discharge port for discharging oil from the pump chamber according to rotation of the rotor;   a first discharge passage communicated to a first communication hole provided in the discharge port and circulating oil discharged from the discharge port, the first discharge passage having a smaller cross sectional area than the discharge port; and   a second discharge passage communicated to a second communication hole provided in the discharge port separately from the first communication hole and circulating oil discharged from the discharge port, the second discharge passage having a smaller cross sectional area than the discharge port.       

     With the above-described characterizing feature, since the first discharge passage and the second discharge passage are provided from the discharge port separately from each other inside the pump body, there is no need to provide, outside the pump body, pipes to connecting portions to external pipes connected respectively to the first discharge passage and the second discharge passage. Therefore, a compact arrangement is made possible, so that an electric oil pump achieving space saving and weight reduction can be realized. Moreover, since the first discharge passage and the second discharge passage are provided from the discharge port separately from each other inside the pump body, there will occur no interference with some device or the like present around the electric oil pump. Therefore, the degree of freedom in the disposing position of the electric oil pump and the degree of freedom in the layouts of the first discharge passage and the second discharge passage can be improved. Further, with the above-described arrangement, there is no branching of the first discharge passage and the second discharge passage inside the pump body, so that the first discharge passage and the second discharge passage respectively can be disposed according to directions of their oil supplying destinations in the electric oil pump. Therefore, there can be realized a configuration with the shortest possible paths according to the directions of the oil supplying destinations of the first discharge passage and the second discharge passage. Hence, the manufacture thereof can be made easier, thus manufacture cost reduction is made possible. 
     Preferably, the first discharge passage and the second discharge passage extend to joining faces to the oil supplying destinations in the pump body. 
     With this arrangement, oil discharged from the discharge port is circulated through the first discharge passage and the second discharge passage respectively, so that direct oil pressure supply to a plurality of positions is made possible. 
     Still preferably, a first check valve opened/closed according to a pressure of oil discharged from the discharge port is provided in the first discharge passage, and a second check valve opened/closed according to a pressure of oil discharged from the discharge port is provided in the second discharge passage. 
     With this arrangement, even when a pressure downstream the first discharge passage and the second discharge passage becomes higher than pressures of the first discharge passage and the second discharge passage, it is still possible to prevent inflow of the oil from this downstream side into the electric oil pump. Accordingly, no inflow of oil from the outside will occur even during stop of operation of the electric oil pump, so that the electric oil pump can be effectively protected. Further, as a check valve is provided in each one of the discharge passages, an entire hydraulic system having the electric oil pump can be formed compact. Therefore, the degree of freedom in layout or the like can be further improved. 
     Still preferably, the second discharge passage includes, downstream the second check valve, an orifice for distributing an amount of flow to the first discharge passage and an amount of flow to the second discharge passage. 
     With this arrangement, since an orifice can be provided inside the pump body, the entire hydraulic system having the electric oil pump can be formed compact. Therefore, the degree of freedom in layout or the like can be further improved. 
     Still preferably, the first check valve is fixed by a fixing screw which advances through an opening hole formed in the pump body into the first discharge passage; a tubular outer oil passage is formed between an outer circumferential face of a shank of the fixing screw and an inner circumferential face of the first discharge passage; and an inner oil passage is formed on a radially inner side of the shank to communicate to the outer oil passage through a communication portion formed in the shank. 
     With this arrangement, it is possible to use a fixing screw for fixing the first check valve as an oil passage. Thus, the electric oil pump can be formed compact. Therefore, the degree of freedom in layout or the like can be further improved. 
     The principles, preferred embodiments and mode of operation of the present invention have been described in the foregoing specification. However, the invention which is intended to be protected is not to be construed as limited to the particular embodiments disclosed. Further the embodiments described herein are to be regarded as illustrative rather than restrictive. Variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such variations, changes and equivalents which fall within the spirit and scope the present invention as defined in the claims, be embraced thereby.