Patent Publication Number: US-2020295643-A1

Title: Electric motor unit

Description:
TECHNICAL FIELD 
     The present invention relates to an electric motor unit including two electric motors each including a rotational-state-quantity detection device. 
     BACKGROUND ART 
     In an electric motor, a resolver is provided as a rotational-state-quantity detection device which precisely detects the rotational position of an electric motor rotor with respect to an electric motor stator for performing accurate speed control on an electric motor main body in some cases. The resolver includes a resolver rotor and a resolver stator, and the resolver rotor is arranged so as to be integrally rotated with the electric motor rotor. Therefore, an output signal from the resolver is processed to detect the rotational position of the resolver rotor so that the rotational position of the electric motor rotor can be detected. An electric motor control device drives and controls the electric motor by converting a direct current voltage supplied from a direct current power supply into an alternating current voltage using an inverter and supplying the voltage to the electric motor based on the rotational position of the electric motor rotor detected by the resolver or the like. Specifically, the electric motor control device determines the phase of a current to be inputted to the electric motor based on the rotational position of the electric motor rotor or the like, and performs switching control on switching elements of the inverter according to the determination. 
     In this manner, the phase of the current to be inputted to the electric motor is determined based on the detection value of the resolver. Thus, in a case where the corresponding detection value has an error, the phase of the current to be inputted to the electric motor is different from the phase of a current to be actually inputted to the electric motor. Therefore, when the electric motor main body and the resolver are assembled, zero-point correction is performed in which the difference between the reference position of the electric motor stator and the reference position of the resolver stator is acquired and corrected. 
     For example, Patent Literature 1 discloses a vehicle drive device including two electric motors each including a resolver in a housing. 
     PRIOR ART LITERATURE 
     Patent Literature 
     
         
         Patent Literature 1: Japanese Patent No. 5750501 
       
    
     SUMMARY OF THE INVENTION 
     Problem that the Invention is to Solve 
     However, in Patent Literature 1, there is no description on how to set the reference position of the electric motor stator and the reference position of the resolver stator in left and right electric motors when performing zero-point correction. Accordingly, when zero-point correction is performed in the respective electric motors, there is concern that numerical management may be complicated. 
     The present invention provides an electric motor unit capable of easily performing zero-point correction in two electric motors each including a rotational-state-quantity detection device. 
     Means for Solving the Problem 
     The present invention provides the following aspects. 
     According to a first aspect, an electric motor unit (e.g., a rear-wheel drive device  1  in an embodiment to be described below) including: 
     a first electric motor (e.g., a first electric motor  102 A in the embodiment to be described below) that is connected to a left wheel (e.g., a left rear wheel LWr in the embodiment) of a vehicle (e.g., a vehicle  3  in the embodiment); and 
     a second electric motor (e.g., a second electric motor  102 B in the embodiment) that is connected to a right wheel (e.g., a right rear wheel RWr in the embodiment) of the vehicle, wherein 
     the first electric motor and the second electric motor each includes: 
     an electric motor main body (e.g., a first electric motor main body  2 A and a second electric motor main body  2 B in the embodiment) including a stator (e.g., stators  14 A and  14 B in the embodiment), and a rotor (e.g., rotors  15 A and  15 B in the embodiment) that is arranged to be relatively rotatable with respect to the stator; and 
     a rotational-state-quantity detection device (e.g., resolvers  20 A and  20 B in the embodiment) including a detected element (e.g., a resolver rotor  90  in the embodiment) that is installed in the rotor or a rotary body (e.g., cylinder shafts  16 A and  16 B in the embodiment) that rotates in conjunction with the rotor, and a detector (e.g., a resolver stator  93  in the embodiment) that detects a rotational state of the detected element, and 
     relative positions between a reference position (e.g., a reference position MS 1  in the embodiment) of the stator of the first electric motor and a reference position (e.g., a reference position RS 1  in the embodiment) of the detector of the first electric motor and 
     relative positions between a reference position (e.g., a reference position MS 2  in the embodiment) of the stator of the second electric motor and a reference position (e.g., a reference position RS 2  in the embodiment) of the detector of the second electric motor coincide with each other based on a rotational direction of the first electric motor and the second electric motor during forward movement of the vehicle or during backward movement of the vehicle. 
     According to a second aspect, in addition to the configuration of the first aspect, 
     in the rotational direction, the reference position of the stator of the first electric motor and the reference position of the stator of the second electric motor are in same phase. 
     According to a third aspect, in addition to the configuration of the second aspect, 
     the first electric motor and the second electric motor are housed in a housing, 
     the electric motor main body of the first electric motor and the electric motor main body of the second electric motor are constituted of same members, and 
     the rotational-state-quantity detection device of the first electric motor and the rotational-state-quantity detection device of the second electric motor are constituted of same members. 
     Advantageous Effects of the Invention 
     According to the first aspect, since the relative positions between the reference position of the stator of the first electric motor and the reference position of the detector of the first electric motor and the relative positions between the reference position of the stator of the second electric motor and the reference position of the detector of the second electric motor coincide with each other based on the rotational direction of the first electric motor and the second electric motor during forward movement or backward movement of the vehicle, a value serving as a guide when zero-point correction is performed is common, thereby easily performing numerical management. 
     According to the second aspect, since the reference position of the stator of the first electric motor and the reference position of the stator of the second electric motor are in the same phase based on the rotational direction of the first electric motor and the second electric motor during forward movement of the vehicle, the electric motors are easily assembled. 
     According to the third aspect, the number of parts can be reduced by sharing parts and thus the manufacturing cost can be reduced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram showing a schematic configuration of a hybrid vehicle as an embodiment on which an electric motor according to the present invention is mountable. 
         FIG. 2  is a vertical cross-sectional view of a rear-wheel drive device. 
         FIG. 3  is an enlarged cross-sectional view of an upper part of the rear-wheel drive device illustrated in  FIG. 2 . 
         FIG. 4A  is a side view illustrating an end wall of a right side case housing a second electric motor on a right side as viewed from the right side. 
         FIG. 4B  is a side view illustrating an end wall of a left side case housing a first electric motor on a left side as viewed from the left side. 
         FIG. 5A  is a side view illustrating the second electric motor on the right side as viewed from the right side when removing the right side case. 
         FIG. 5B  is a side view illustrating the first electric motor on the left side as viewed from the left side when removing the left side case. 
         FIG. 6  is an explanatory diagram illustrating zero-point correction. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, an example of a hybrid vehicle as a vehicle on which an electric motor according to an embodiment is mountable will be described. 
     A vehicle  3  illustrated in  FIG. 1  is a hybrid vehicle including a drive device  6  (hereinafter, referred to as a front-wheel drive device) at the front part of the vehicle, the drive device  6  being formed by connecting an electric motor  5  and an internal combustion engine  4  in series. While power of the front-wheel drive device  6  is transmitted to front wheels Wf through a transmission  7 , power of a drive device  1  (hereinafter, referred to as a rear-wheel drive device), which is provided below a floor panel (not shown) in the rear part of the vehicle separately from the front wheel drive device  6 , is transmitted to rear wheels Wr (RWr and LWr). The rear-wheel drive device  1  includes first and second electric motor main bodies  2 A and  2 B, power of the first electric motor main body  2 A is transmitted to a left rear wheel LWr and power of the second electric motor main body  2 B is transmitted to a right wheel RWr. The electric motor  5  of the front-wheel drive device  6 , and first and, second electric motor main bodies  2 A and  2 B of the rear-wheel drive device  1  are connected to a battery  9 , thereby enabling electric power supply from the battery  9  and energy regeneration to the battery  9 . 
       FIG. 2  is vertical cross-sectional view of the entire rear-wheel drive device  1 , and  FIG. 3  is an enlarged cross-sectional view of an upper part of the rear-wheel drive device illustrated in  FIG. 2 . A case  11  serving as a housing of the rear-wheel drive device  1  includes a central case  11 M arranged in approximately the middle in a vehicle width direction (hereinafter, also referred to as a left and right direction of the vehicle), and a left side case  11 A and a right side case  11 B arranged on the right and left of the central case  11 M so as to interpose the central case  11 M. The entire case  11  is formed in a substantially cylindrical shape. Inside the case  11 , axles  10 A and  10 B for the rear wheels Wr, first and second electric motor main bodies  2 A and  2 B for driving the axles, and first and second planetary gear speed reducers  12 A and  12 B for reducing the drive rotation of the first and second electric motor main bodies  2 A and  2 B are respectively arranged in parallel on the same rotation axis x. The axle  10 A, the first electric motor main body  2 A, and the first planetary gear speed reducer  12 A drive and control the left rear wheel LWr, and the axle  10 B, the second electric motor main body  2 B, and the second planetary gear speed reducer  12 B drive and control the right rear wheel RWr. The axle  10 A, the first electric motor main body  2 A, and the first planetary gear speed reducer  12 A, and the axle  10 B, the second electric motor main body  2 B, and the second planetary gear speed reducer  12 B are arranged symmetrically to a center surface M orthogonal to the rotation axis x and located at the center in the case  11  in the vehicle width direction. 
     Partition walls  18 A and  18 B extending radially inwardly are provided on the center case  11 M side of the left and right side cases  11 A and  11 B and the first and second electric motor main bodies  2 A and  2 B are respectively arranged between end walls  17 A and  17 B and the partition walls  18 A and  18 B of the left and right side cases  11 A and  11 B, respectively. In addition, the first and second planetary gear speed reducers  12 A and  12 B are arranged in a space surrounded by the center case  11 M and the partition walls  18 A and  18 B. 
     The rear-wheel drive device  1  is provided with a breather device  40  which communicates with the inside and the outside of the case  11  so that the internal air can escape through a breather chamber  41  in order to prevent the internal air from becoming excessively high in temperature and pressure. The breather chamber  41  is arranged vertically above the case  11 , and is constituted of the space that is formed by the outer wall of the central case  11 M, a first cylindrical wall  43  which extends toward the left side case  11 A in a substantially horizontal direction in the central case  11 M, a second cylindrical wall  44  which extends toward the right side case  11 B in a substantially horizontal direction in the central case  11 M, a right-and-left dividing wall  45  which connects the inner ends of the first and second cylindrical walls  43  and  44 , a baffle plate  47 A which is attached to come into contact with the distal end of the left side case  11 A of the first cylindrical wall  43 , and a baffle plate  47 B which is attached to come into contact with the distal end of the right side case  11 B of the second cylindrical wall  44 . 
     The first and second cylindrical walls  43  and  44 , and the right-and-left dividing wall  45  which forms the lower surface of the breather chamber  41  are formed so that the first cylindrical wall  43  is located radially inwardly from the second cylindrical wall  44 , and the right-and-left dividing wall  45  extends from the inner end portion of the second cylindrical wall  44  to the inner end portion of the first cylindrical wall  43  while bending to reduce the size in the radial direction. The right-and-left dividing wall  45  further extends radially inwardly and reaches a third cylindrical wall  46  which extends in a substantially horizontal direction. The third cylindrical wall  46  is located at substantially the center on the inner side of both outer ends of the first cylindrical wall  43  and the second cylindrical wall  44 . 
     In the central case  11 M, the baffle plates  47 A and  47 B are fixed so as to partition the space between the first cylindrical wall  43  and the outer wall of the central case  11 M, and the space between the second cylindrical wall  44  and the outer wall of the central case  11 M in order to separate the first planetary gear speed reducer  12 A and the second planetary gear speed reducer  12 B, respectively. 
     In the first and second electric motor main bodies  2 A and  2 B, stators  14 A and  14 B are respectively fixed to the left and right side cases  11 A and  11 B, and ring-shaped rotors  15 A and  15 B are arranged to be relatively rotatable to the stators  14 A and  14 B within the inner circumference of the stators  14 A and  14 B. In the inner circumference of the rotors  15 A and  15 B, cylindrical shafts  16 A and  16 B, which respectively surround the outer circumference of the axles  10 A and  10 B, are secured thereto, and are supported through bearings  19 A and  19 B on the end walls  17 A and  17 B and the partition walls  18 A and  18 B of the side cases  11 A and  11 B, respectively, so that the cylindrical shafts  16 A and  16 B are rotatable relative to the axles  10 A and  10 B on the same axis. 
     In the end walls  17 A and  17 B on the outer circumference of one end side of the cylinder shafts  16 A and  16 B, a cylinder wall  81  which surrounds the axles  10 A and  10 B arranged to be relatively rotatable on the inner circumference of the cylinder shafts  16 A and  16 B is provided to extend. A resolver rotor  90  is attached to one end side of the cylinder shafts  16 A and  16 B as a detected element, and a resolver stator  93  is attached to the end walls  17 A and  17 B as a detector for detecting the rotational state of the resolver rotor  90  so as to face the outer diameter side of the resolver rotor  90 . The resolver rotor  90  and the resolver stator  93  constitute the resolvers  20 A and  20 B and the resolvers  20 A and  20 B are provided for feeding back the rotational state quantities of the rotors  15 A and  15 B such as the rotation angles, angular speeds, and the number of revolutions to controllers (not shown) of the first and second electric motor main bodies  2 A and  2 B. In addition, since the resolver rotors  90  and the rotors  15 A and  15 B of the first and second electric motor main bodies  2 A and  2 B provided on the cylinder shafts  16 A and  16 B and the axles  10 A and  10 B are mechanically connected through the first and second planetary gear speed reducers  12 A and  12 B as described later, a wheel speed can be calculated from the rotational state quantities of the rotors  15 A and  15 B and the gear ratio. The resolver  20 A constitutes a first electric motor  102 A together with the first electric motor main body  2 A and the resolver  20 B constitutes a second electric motor  102 B together with the second electric motor main body  2 B. 
     The first and second planetary gear speed reducers  12 A and  12 B respectively include sun gears  21 A and  21 B, a plurality of planetary gears  22 A and  22 B engaged with the sun gears  21 A and  21 B, planetary carriers  23 A and  23 B for supporting the planetary gears  22 A and  22 B, and ring gears  24 A and  24 B engaged with the outer circumferential side of planetary gears  22 A and  22 B, and the drive rotations of the first and second electric motor main bodies  2 A and  2 B are inputted through the sun gears  21 A and  21 B, respectively, and reduced drive rotations are outputted to the axles  10 A and  10 B through the planetary carriers  23 A and  23 B. 
     The sun gears  21 A and  21 B are formed integrally with the cylindrical shafts  16 A and  16 B. The planetary gears  22 A and  22 B are each twin pinion including first major diameter pinions  26 A and  26 B which are directly engaged with the sun gears  21 A and  21 B, and second pinions  27 A and  27 B having a diameter smaller than that of the first pinions  26 A and  26 B. The first pinions  26 A and  26 B and the second pinions  27 A and  27 B are integrally formed on the same axis with an offset in the axial direction. The planetary gears  22 A and  22 B are supported by the planetary carriers  23 A and  23 B to be rotatable and revolvable, and the axial inner ends of the planetary carriers  23 A and  23 B extend radially inwardly to be spline-fitted to and supported by the axles  10 A and  10 B in an integrally rotatable manner, and are supported by the partition walls  18 A and  18 B through bearings  33 A and  33 B. 
     The ring gears  24 A and  24 B include gears portions  28 A and  28 B, the inner circumferential surfaces of which are engaged with the minor diameter second pinions  27 A and  27 B, minor diameter gear portions  29 A and  29 B which each have a diameter smaller than that of the gears portions  28 A and  28 B and are arranged to face each other at the middle position of the case  11 , and coupling portions  30 A and  30 B which respectively radially couple the axially inner ends of the gears portions  28 A and  28 B to the axially outer ends of the minor diameter gear portions  29 A and  29 B. 
     The gear portions  28 A and  28 B are axially opposed to each other with respect to the third cylindrical wall  46 , which is formed at the inner diameter end of the right-and-left dividing wall  45  of the central case  11 M. The outer circumferential surfaces of the minor diameter gear portions  29 A and  29 B are each spline-fitted to an inner race  51  of the below-described one-way clutch  50 , and the ring gears  24 A and  24 B are connected to the inner race  51  of the one-way clutch  50  so as to rotate integrally therewith. 
     A hydraulic brake  60  which serves as a braking device for the ring gear  24 B is arranged between the second cylindrical wall  44  of the central case  11 M included in the case  11 , and the gear portion  28 B of the ring gear  24 B on the side of the second planetary gear speed reducer  12 B so that the hydraulic brake radially overlaps with the first pinion  26 B and axially overlaps with the second pinion  27 B. In the hydraulic brake  60 , a plurality of fixed plates  35  which are spline-fitted to the inner circumferential surface of the second cylindrical wall  44 , and a plurality of rotary plates  36  which are spline-fitted to the outer circumferential surface of the gear portion  28 B of the ring gear  24 B are alternately arranged in the axial direction so that an engaging or releasing operation is performed on the plates  35  and  36  by a ring-shaped piston  37 . The piston  37  is retractably housed in a ring-shaped cylinder chamber which is formed between the right-and-left dividing wall  45  of the central case  11 M and the third cylindrical wall  46 , and is further constantly biased by an elastic member  39  in a direction such that the fixed plates  35  and the rotary plates  36  are released, and the elastic member  39  is supported by a receiving member which is provided on the outer circumferential surface of the third cylindrical wall  46 . 
     In addition, more specifically, between the right-and-left dividing wall  45  and the piston  37 , an operating chamber into which oil is directly introduced is formed, and when the pressure of the oil introduced into the operating chamber S exceeds the biasing force of the elastic member  39 , the piston  37  moves forward (moves to the right) so that the fixed plates  35  and the rotary plates  36  are pressed each other and then engaged. On the other hand, when the biasing force of the elastic member  39  exceeds the pressure of the oil introduced into the operating chamber S, the piston  37  moves backward (moves to the left) so that the fixed plates  35  and the rotary plates  36  are separated from each other and then released. The hydraulic brake  60  is connected to an electric oil pump  70  (refer to  FIG. 1  and others). 
     In a case of the hydraulic brake  60 , the fixed plates  35  are supported by the second cylindrical wall  44  extending from the right-and-left dividing wall  45  of the central case  11 M which constitutes the case  11 , while the rotary plates  36  are supported by the gear portion  28 B of the ring gear  24 B. Thus, when both plates  35  and  36  are pressed each other by the piston  37 , frictional engagement between the plates  35  and  36  causes a braking force to be applied to the ring gear  24 B which is then fixed. In the above-described state, when the engagement caused by the piston  37  is released, the ring gear  24 B is allowed to rotate freely. As described above, the ring gears  24 A and  24 B are connected to each other, and thus engagement of the hydraulic brake  60  also causes a braking force to be applied to the ring gear  24 A, and release of the hydraulic brake  60  also allows the ring gear  24 A to rotate freely. 
     A space is also secured between the coupling portions  30 A and  30 B of the ring gears  24 A and  24 B which are axially opposed to each other, and in the space, the one-way clutch  50  is arranged which allows power to be transmitted to the ring gears  24 A and  24 B only in one direction and prevents power transmission in the other direction. The one-way clutch  50  is a clutch in which a large number of sprags  53  are interposed between the inner race  51  and an outer race  52 , and has a configuration such that the inner race  51  rotates integrally with the minor-diameter gear portions  29 A and  29 B of the ring gears  24 A and  24 B by spline fitting. The outer race  52  is positioned and whirl-stopped by the third cylindrical wall  46 . 
     The one-way clutch  50  is configured to engage and lock rotation of the ring gears  24 A and  24 B when the vehicle  3  moves forward under the power of the first and second electric motor main bodies  2 A and  2 B. More specifically, when forward direction (rotation direction when the vehicle  3  moves forward) rotational power of the first and second electric motor main bodies  2 A and  2 B is inputted to the rear wheels Wr, the one-way clutch  50  is set in an engaged state, and when reverse direction rotational power of the first and second electric motor main bodies  2 A and  2 B is inputted to the rear wheels Wr, the one-way clutch  50  is set in a disengaged state. When forward direction rotational power of the rear wheels Wr is inputted to the first and second electric motor main bodies  2 A and  2 B, the one-way clutch  50  is set in a disengaged state, and when reverse direction rotational power of the rear wheels Wr is inputted to the first and second electric motor main bodies  2 A and  2 B, the one-way clutch  50  is set in an engaged state. 
     Thus, in the rear-wheel drive device  1  in the embodiment, the one-way clutch  50  and the hydraulic brake  60  are provided in parallel on the power transmission path between the first and second electric motor main bodies  2 A and  2 B, and the rear wheels Wr. The hydraulic brake  60  is controlled in a released or engaged state, a partially engaged state, or an engaged state by the pressure of the oil supplied from the electric oil pump  70  according to a running state of the vehicle and an engaged or disengaged state of the one-way clutch  50 . For example, when the vehicle  3  moves forward by driving power of the first and second electric motor main bodies  2 A and  2 B (at the time of low vehicle speed or medium vehicle speed), the one-way clutch  50  is engaged and thus is set in a state which allows power transmission. However, the hydraulic brake  60  is controlled to be in a partially engaged state, and thus input of forward direction rotational power from the first and second electric motor main bodies  2 A and  2 B is temporarily reduced, and even in a case where the one-way clutch  50  is set in a disengaged state, power transmission between the first and second electric motor main bodies  2 A and  2 B and the rear wheels Wr is possible. In addition, when the vehicle  3  moves forward by driving power of the internal combustion engine  4  and/or the electric motor  5  (at the time of high vehicle speed), the one-way clutch  50  is disengaged and the hydraulic brake  60  is further controlled in a released state, and thus excessive rotation of the first and second electric motor main bodies  2 A and  2 B is prevented. On the other hand, when the vehicle  3  moves backward or power regeneration is performed, the one-way clutch  50  is disengaged, and thus by controlling the hydraulic brake  60  to be in an engaged state, reverse direction rotational power of the first and second electric motor main bodies  2 A and  2 B is outputted to the rear wheels Wr, or forward direction rotational power of the rear wheels Wr is inputted to the first and second electric motor main bodies  2 A and  2 B. 
     Here, the zero-point correction of the resolvers  20 A and  20 B (hereinafter, in a case where the resolvers  20 A and  20 B are not distinguished, the resolvers  20 A and  20 B are referred to as the resolver  20 . The same applies to the first and second electric motor main bodies  2 A and  2 B, the stators  14 A and  14 B, and the rotors  15 A and  15 B.) will be described with reference to  FIGS. 4A to 6 . Here, a case where the first and second electric motor main bodies  2 A and  2 B are three-phase alternating current electric motors and a zero-point correction process is performed based on a U phase will be described. In  FIGS. 4A, 4B, 5A, and 5B , reference numeral  95  indicates connectors of the first and second electric motor main bodies  2 A and  2 B, and the connector  95  of the first electric motor main body  2 A is arranged on the end wall  17 A of the left side case  11 A so as to face the outer side (left direction), while the connector  95  of the second electric motor main body  2 B is arranged on the end wall of the right side case  11 B so as to face the outer side (right direction). 
     The zero-point correction is performed such that a predetermined current for zero-point correction is supplied to the stator  14  of the electric motor main body  2  and an induction voltage of the electric motor main body  2  obtained from the U phase is acquired. In addition, the rotor  15  is rotated by the current supplied to the stator  14 , and the resolver rotor  90  rotates in conjunction with the rotation of the rotor  15  so that electrical angle signals generated from the resolver stator  93  can be acquired. 
       FIG. 6  shows a U-phase current, a U-phase induction voltage, and electrical angle signals of the resolver generated by the zero-point correction and the zero-point correction is performed by obtaining a correction amount from the relationship between the electrical angle of the U-phase current and the electrical angle of the resolver  20  and correcting the electrical angle of the resolver based on the correction amount. Specifically, for example, when the U-phase induction voltage is shifted from positive to negative (hereinafter, referred to as a falling zero-cross point), that is, when the phase of the U-phase induction voltage is 180°, the electrical angle (α°) of the resolver is detected, a value obtained by subtracting the detected electrical angle (α°) of the resolver from 360° is acquired as a correction value (β°), and the correction value is added to the electrical angle of the resolver. 
     The zero-point correction is performed on the left and right first and second electric motors  102 A and  102 B respectively since the electric motor main body  2 , the resolver  20 , and the case  11  respectively have size errors and assembly errors. However, when the left and right first and second electric motors  102 A and  102 B have completely irrelevant correction values, numerical management becomes complicated. Therefore, it is advantageous to have a common correction reference value which serves as a guide for a correction value from the viewpoint of numerical management. 
     In the present invention, relative positions between a reference position MS 1  of the stator  14 A of the first electric motor  102 A and a reference position RS 1  of the resolver stator  93  of the first electric motor  102 A and relative positions between a reference position MS 2  of the stator  14 B of the second electric motor  102 B and a reference position RS 2  of the resolver stator  93  of the second electric motor  102 B coincide with each other based on one of the rotational direction of the first electric main body  2 A and the second electric main body  2 B (in the embodiment, the rotational direction during forward movement of the vehicle  3 ). 
     Specifically, as shown in  FIGS. 5A and 5B , a U-phase coil center line MC 1  passing through the center of one coil of four U-phase coils of the stator  14 A of the first electric motor  102 A in the circumferential direction and the rotation axis x is set to a reference position MS 1  of the stator  14 A, and a connector center line RC 1  passing through the center of a connector  94  of the resolver stator  93  in the circumferential direction and the rotation axis x is set to a reference position RS 1  of the resolver stator  93 . On the other hand, a U-phase coil center line MC 2  passing through the center of one coil of four U-phase coils of the stator  14 B of the second electric motor  102 B and the rotation axis x is set to a reference position MS 2  of the stator  14 B and a connector center line RC 2  passing through the center of the connector  94  of the resolver stator  93  in the circumferential direction and the rotation axis x is set to a reference position RS 2  of the resolver stator  93 . In this manner, the relative positions between the U-phase coil center line MC 1  and the connector center line RC 1  in the first electric motor  102 A and the relative positions between the U-phase coil center line MC 2  and the connector center line RC 2  in the second electric motor  102 B coincide with each other based on the rotational direction of the first electric motor main body  2 A and the second electric motor main body  2 B when the vehicle  3  moves forward as indicated by an arrow in  FIGS. 5A and 5B , that is, a forward direction. 
     Here, any one of a plurality (four in the embodiment) of U-phase coils may be set as a reference. However, when the reference position RS 1  of the stator  14 A of the first electric motor  102 A and the reference position RS 2  of the stator  14 B of the second electric motor  102 B are set to have the same phase, that is, for example, a vertical line Y passing through the rotation axis x is set as a reference, the same phase (γ° in the embodiment) is preferably set from Y in the forward direction. Thus, the first and second electric motors  102 A and  102 B are easily assembled. 
     In addition, the reference is not limited to the U-phase coil and any one of a plurality of V-phase coils or W-phase coils may be used as a reference. Regarding the resolver stators  93 , the reference position is not limited to the connector  94  and as long as the reference position is the same position in the left and right resolver stators  93 , the reference position can be set to an arbitrary position. 
     Further, it is preferable that the first and second electric motor main bodies  2 A and  2 B are constituted of the same members and the resolvers  20 A and  20 B are constituted of the same members. Therefore, the number of parts can be reduced by sharing parts and thus the manufacturing cost can be reduced. 
     As described above, according to the embodiment, since the relative positions between the reference position MS 1  of the stator  14 A of the first electric motor  102 A and the reference position RS 1  of the resolver stator  93  of the first electric motor  102 A and the relative positions between the reference position MS 2  of the stator  14 B of the second electric motor  102 B and the reference position RS 2  of the resolver stator  93  of the second electric motor  102 B coincide with each other based on the rotational direction of the first electric motor main body  2 A and the second electric motor main body  2 B when the vehicle  3  moves forward, a value which serves as a guide is common during zero-point correction and numerical management becomes easy. 
     In addition, the present invention is not limited to the above-described embodiment and appropriate modifications, improvements, and the like can be made. 
     For example, in the above-described embodiment, a hybrid vehicle has been described as a vehicle for application. However, the present invention is not limited thereto and for example, an electric automobile only using a motor as a driving source may be used. 
     In addition, in the embodiment, the rear-wheel drive device  1  including the two first and second electric motor main bodies  2 A and  2 B, the first and second planetary gear speed reducers  12 A and  12 B, the case  11  for housing the first and second electric motor main bodies  2 A and  2 B and the first and second planetary gear speed reducers  12 A and  12 B, and the two resolvers  20 A and  20 B is described as an example. However, as the electric motor unit of the present invention, two electric motors may each include electric motor main bodies and rotational-state-quantity detection devices. 
     The present application is based on Japanese Patent Application (No. 2016-065530) filled on Mar. 29, 2016, the contents of which are incorporated herein by reference. 
     DESCRIPTION OF REFERENCE NUMERALS AND CHARACTERS 
     
         
         
           
               1  Rear-wheel drive device (electric motor unit) 
               2 A First electric motor main body (electric motor main body) 
               2 B Second electric motor main body (electric motor main body) 
               3  Vehicle 
               14 A,  14 B Stator (stator) 
               15 A,  15 B Rotor (rotor) 
               16 A,  16 B Cylinder shaft (rotary body) 
               20 A,  20 B Resolver (rotational-state-quantity detection device) 
               90  Resolver rotor (detected element) 
               93  Resolver stator (detector) 
             MS 1  Reference position (reference position of stator of first electric motor) 
             MS 2  Reference position (reference position of stator of second electric motor) 
             RS 1  Reference position (reference position of detector of first electric motor) 
             RS 2  Reference position (reference position of detector of second electric motor)