WO2020065676A1

WO2020065676A1 - A vehicle with an electric machine

Info

Publication number: WO2020065676A1
Application number: PCT/IN2019/050707
Authority: WO
Inventors: Chidambaram SUBRAMONIAM; Yogesh DEVIDAS PATIL; Govardan Daggupati; Soumya Saxena
Original assignee: Tvs Motor Company Limited
Priority date: 2018-09-27
Filing date: 2019-09-26
Publication date: 2020-04-02

Abstract

The present subject matter relates generally to a two-wheeled vehicle. The present subject matter specifically but not exclusively related to a stator holder plate (205) structure for said two-wheeled vehicle. The stator plate holder (205) comprises a top plate (205a) and a bottom plate (205b), both extending at an angle till the welding boss (203), fixedly attached, in the middle of the stator holder plate (205) to hold the motor axle. The present subject matter provides improved strength to the stator holder plate (205) and prevents weld crack formation in the welding of the welding boss (203) and also preventing crack formation on the motor covers.

Description

A VEHICLE WITH AN ELECTRIC MACHINE

TECHNICAL FIELD

[0001] The present subject matter relates generally to a vehicle. The present subject matter specifically but not exclusively related to a stator holder plate structure for an electric machine of a vehicle.

BACKGROUND

[0002] Generally, commuting is an essential activity every day for majority of the people. Typically, there are various types of vehicles that are used for community depending on the application and the capacity thereof. Of these, a particular category of vehicles have acquired prominence due to their ease of operation and compact layout. Saddle ride-type vehicles are one such category of motor vehicles that are having at least two-wheels and provide a saddle-ride type posture when being operated. These vehicles have a compact layout and are adapted to accommodate at least one user.

[0003] Generally, these vehicles include at least one electric machine that is either an electric motor or an internal combustion (IC) engine to generate tractive force as a prime mover. Some vehicles incorporate both the electric motor and the internal combustion engine that are referred to as hybrid vehicles. Vehicles incorporating electric motor as one of the electric motor are gaining popularity because of their ease of operation, low cost of operation, and reduced emissions. Therefore, the vehicles incorporating the electric motor that are either purely electrical vehicles or the hybrid vehicles are having the electric motor that is either fixedly mounted to a frame member or is swing ably connected to the structural member of the frame member. The electric motor is driven by a primary and/or auxiliary power source that provides electrical energy that is converted to mechanical energy by excitation of electrical coils provided in the electric motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] The detailed description is described with reference to the accompanying figures. The same numbers are used throughout the drawings to reference like features and components.

[0005] Fig. 1. illustrates a left side view of an exemplary two-wheeled vehicle.

[0006] Fig. 2. illustrates a top view of the present subject matter.

[0007] Fig. 3 illustrates an isometric view of the present subject matter.

[0008] Fig. 4 illustrates a cross sectional view of the present subject matter.

[0009] Fig.4 illustrates a zoomed in view of the relevant portion of the present subject matter.

[00010] Fig. 5 illustrates a front view of the left hand side of the motor cover.

[00011] Fig. 6 illustrates a rear view of the left hand side of the motor cover.

[00012] Fig. 7 illustrates a front view of the right hand side of the motor cover.

[00013] Fig. 8 illustrates a rear view of the right hand side of the motor cover.

DETAILED DESCRIPTION

[00014] An electric two wheeler typically has an Electric motor attached to wheel of the vehicle mounted either on the front or rear wheel hub of the two wheeler. Such vehicles generally have brushless direct current motor where the stator is stationary and the rotor will have magnets attached to the inner mating diameter of the motor while maintaining sufficient operating clearance between stator outer diameter and rotor inner diameter. In such a layout the stator is generally attached to dead axle which is fixed either on the front fork or on the rear swing arm firmly. The stator of the motor is generally connected by sheathed cables to receive power from the battery through motor controller and to receive signal from the Hall Effect sensor mounted on the stator to the controller. The set of cables are generally routed through a hole made in the dead axle attached to stator. [00015] Hub Motor axle is supported on bearings fitted on motor covers. Stator has teeth for carrying motor winding which is supported on axle through stator plate. Stator holder plate has usually flat arms with air holes for ventilation and the arms are riveted together. If this stator structure is not strong enough to take axial vibrations from road, the welded portion of welding boss together with the stator holder plate is prone to failure due to this weak structural form. Stator holder plate takes the axial, lateral and longitudinal vibrations from road, so it should have enough strength to withstand such vibrations. Additionally, there exists a challenge of such hub motor axle system to be able to transfer traction torque from the power train of the prime mover to the wheel to move the vehicle without any durability failures. As the weight of the vehicle increases, it puts higher demand on the strength of the system to be able to transfer higher traction torque. Towards meeting this, axle boss of higher diameter is used which leads to undesirable weight increase of the wheel & vehicle as a whole. The torque experienced by the hub motor axle varies significantly during stall, low speed & cruise conditions & the same is also influenced by type of the power train of the system i.e. IC engine type or EV or Hybrid type. A single design of the stator plate system fails to meet the requirement across above variations thereby leading to more variety in production. Therefore, there is a need to have a design of an electrical machine which overcomes all of the above stated problems.

[00016] It is an aspect of the present subject matter that the structural member can be a swingarm or a crankcase that support at least one wheel of the vehicle. The electric motor that is brush less direct current (BLDC) type and the electric motor is functionally connected to a high capacity battery/battery pack(s) through a master control unit.

[00017] It is a feature that the structural member as per the present subject matter may include one or more arms that extends substantially in a longitudinal direction of the vehicle. The electric motor is mounted to the one or more arms acting as axle support thereof, wherein, in a structural member with two arms the electric motor is either mounted to the arms or between the arms. The electric motor is preferably hub mounted to a wheel and is disposed away from a pivot portion of the structural member. Therefore, it is an advantage that the vehicle utility space that includes the step-through space or the utility box space is retained.

[00018] It is a feature that the electric motor includes a stationary member and a rotating member that are supported by a shaft that acts as axle for the electric motor and also the wheel. The shaft is disposed substantially in width direction of the vehicle and is supported by the structural member. The stationary member is fixedly mounted to the shaft and the rotating member is rotatable about the shaft. In one embodiment, the rotating member is connected to a rim portion of the wheel. Therefore, the current electric motor provides the benefit of direct torque transfer.

[00019] The stationary member includes plurality of teeth provided with windings/coils. The rotating member rotates about the stationary member with an inner peripheral surface of the rotating member facing the teeth. The inner peripheral surface is provided with magnets affixed thereat. Further, a cable assembly functionally connected to the windings provides required current/voltage for operation thereof.

[00020] Another embodiment of the present subject matter is to provide a stator holder plate which is designed in such a way that it can withstand vibrations from road and also have strength to support a larger diameter shaft with bearing for support.

[00021] Another embodiment of the present subject matter provides a stator holder plate with conical shape welding of welding boss with stator plate instead of conventional planar surface to get the form strength. The welding is done in convex shape so that there is no line mark in weld area and no porosity is present.

[00022] Yet another embodiment of the present subject matter provides a stator holder plate where stator arms are raised in conical shape instead of keeping it flat and the conical shape meets to form a plateau near inner periphery of stator holder plate.

[00023] Another embodiment of the present subject matter provides a grommet at the shaft end to prevent water entry through the ends of shaft by capillary action. The present subject matter along with all the accompanying embodiments and their advantages would be described in greater detail in conjunction with the figures in the following paragraphs.

[00024] Fig. 1 illustrates a left side view of an exemplary two-wheeled vehicle (100), in accordance with an embodiment of the present subject matter. The vehicle (100) illustrated, has a frame member (105). In the present embodiment, the frame member (105) is step-through type includes a head tube (105 A), and a main frame (105B) that extend rearwardly downward from an anterior portion of the head tube (105A). The main frame (105B) extends inclinedly rearward to a rear portion of the vehicle (100).

[00025] The vehicle (100) includes one or more movers that are connected to the frame member (105). In the present implementation, one of the prime movers is an internal combustion (IC) engine (115) mounted to the frame member (105). In the depicted embodiment, the IC engine (115) is mounted to a structural member (135) that is pivoted to the frame member (105). In one embodiment, the structural member (135) is a rigid member made of metal. The vehicle (100) also includes another prime mover, which is an electric motor (120). In a preferred embodiment, the electric motor (120) is hub mounted to one wheel of the vehicle (100). In another embodiment, more than one electric motor is mounted to wheels of the vehicle. In the depicted embodiment, the vehicle (100) includes at least two-wheels and the electric motor (120) is hub mounted to the rear wheel (125) of the vehicle. A front wheel (110) is rotatably supported by the frame member (105) and is connected to a handle bar assembly (130) that enables manoeuvring of the vehicle (100).

[00026] Further, the vehicle (100) includes a high capacity on-board battery (not shown) that drives the electric motor (120). The high capacity battery may include one or more high capacity battery packs or one or more low capacity cells. The high capacity battery can be disposed at a front portion, a rear portion, or at the center of the vehicle (100). The high capacity battery is supported by the frame member (105) and the vehicle (100) includes plurality of body panels, mounted to the frame member (105) for covering various components of the vehicle (100). The plurality of panels includes a front panel (140A), a leg shield (140B), an under-seat cover (140C), and a left and a right side panel (140D). A glove box may be mounted to a leg shield (140B).

[00027] A floorboard (145) is provided at the step-through portion defined by the main tube (105B). A seat assembly (150) is disposed rearward to the step-through portion and is mounted to the main frame (105B). The seat assembly (150) that is elongated in a longitudinal direction F-R of the vehicle (100) enables the user to operate the vehicle in a saddle ride-type posture. One or more suspension(s) connect the wheels (110), (125) to the vehicle (100) and provide comfortable ride. The vehicle (100) comprises of plurality of electrical and electronic components including a headlight (155A), a taillight (155B), a starter motor (not shown), a horn etc. Also, the vehicle (100) includes a master control unit (not shown) that takes control of the overall operation of the vehicle (100) including the function of the IC engine (115), the electric motor (120), charging of the batteries from a magneto/integrated starter generator (ISG), driving of loads by the magneto/ISG, charging of the high capacity batteries by the electric motor operating in generator mode, and any other operations associated with the operation of the vehicle (100). the vehicle (100) can be a two-wheeled saddle type or a three wheeled vehicle.

[00028] Fig. 2 illustrates the top view of the present subject matter. The stator holder plate (205) removably attached onto the stator of the motor or the wheel hub. Presence of a stator holder plate (205) provides additional strength to the stator of the motor during various driving conditions of the vehicle. Stator comprises of two parts, first part is stator holder plate (205) and second part is the teeth (201) designed to hold the motor windings which are supported on the outer periphery of the stator holder plate (205). Stator holder plate (205) comprises two types of surfaces, one is the planar surface (208) and the other is in trapezoidal shape which are the at least three or more trapezoidal surfaces (202a, 202b, 202c, 202d, 202e and 202f).

[00029] During the operation of the electric motor, heat is generated from the windings when current flows through it and also during continuous motion of the rotor. In order to dissipate the heat generated from the electric motor and to allow proper air circulation the stator holder plate (205) is provided with at least three or more plurality of ventilation holes (206a, 206b, 206c, 206d, 206e and 206f) on the at least three or more trapezoidal surface (202a, 202b, 202c, 202d,202e and 202f). The stator holder plate (205) comprises of two back-to-back plates, a top plate (205a) and a bottom plate (205b) as shown in Fig 4. The two stator holder plates comprising the trapezoidal surfaces are riveted together using at least three or more rivets (204 a, 204b, 204c, 204d, 204e and 204f). Arms (211) are formed between every two adjacent trapezoidal surfaces. The arms (211) are formed by the two stator holder plates (205) forming a hollow cone (not shown). All the starts from the outer periphery of the stator holder plate (205) and gradually elevate till the point where the stator holder plate (205) has the inner periphery. All the arms (211) merge near the inner periphery of the stator holder plate (205) to form an elevated plateau (207). The inner periphery of the stator holder plate (205) is welded to the welding boss (203) in a substantially convex shaped profile when viewed from the side of the stator holder plate (205). The welding boss is provided with a keyway (203a) which aids the axle of the motor to fit in properly & engage it rigidly for torque transfer. The welding boss (203) can accommodate the axle of the electric motor. The welding boss (203) welded to the stator holder plate (205) in substantial convex shaped profile provides improved strength. As per another embodiment of the present invention the profile is substantially concave in shape. Internal diameter of stator has tight fit with the axle to hold the motor axle with sufficient clearance to avoid deformation. Diameter of boss Dl at the welding portion is optimized with respect to the diameter of the stator D2 i.e. (ratio D1/D2) to provide more welding strength. As per an embodiment of the present subject matter the ratio D1/D2 is in the range of 0.2 to 0.4 to achieve best weld strength, joint rigidity as well as low weight & cost of manufacturing the stator assembly. A ratio lower than 0.2 is detrimental in terms of the torsional rigidity of the welded joint to withstand the traction or torque provided by the prime mover & a ratio more than 0.4 leads to undesirable weight & inertia increase at the wheel leading to poor handling & manoeuvrability of the vehicle. As per another embodiment of the present subject matter, the ratio D1/D2 is proportional to the ratio of Torque T at the wheel & the weight W of the vehicle. D1/D2 = K x (W/T) where K is a pre-determined co-efficient. As per an embodiment of the present invention, the value of K ranges from 1 to 2.

[00030] Stator holder plate (205) is also provided with wire perforations (209a, 209b, 2l0a, 2 lOb) to tie the sensor wires routed to PCB on stator. As per an embodiment, the sensor is hall sensor.

[00031] Fig. 3 illustrates the isometric view of the stator provided with circumferentially arranged teeth to wind the wire. A stator holder plate (205) to hold the stator and the axle of the electric motor is accommodated within a welding boss (203). The inner periphery of the stator holder plate (205) is welded to the welding boss (203) and the welding boss is provided with a keyway (203a) which allows the axle of the motor to fit at specific position rigidly and discourages any free play. Two stator holder plates (205) are riveted together. Both of the stator holder plates (205) are of same structure complimentary to each other. The trapezoidal surface (202a, 202b, 202c, 202d, 202e and 202f) is provided on the stator holder plate (205).

[00032] Fig. 4 illustrates the cross section of the present subject matter. The stator holder plate (205) is divided into two plates, a top plate (205a) and a bottom plate (205b). The top plate (205a) and bottom plate (205b) are fixedly attached at the contact area (400) formed by both top plate (205a) and bottom plate (205b) by fastening means like rivets (204a, 204b, 204c, 204d, 204e, 204f) in such a manner that that both the top plate (205a) and bottom plate (205b) are mirroring each other. The top plate (205a) and the bottom plate (205b) extend from the outer periphery of the stator holder plate (205) towards the inner periphery of the stator holder plate (205). Both top plate (205a) and bottom plate (205b) forms an angle a with the imaginary line of separation (401). This angle enables forming a substantially concave or convex profile of the stator holder plate.

[00033] The top plate (205a) and bottom plate (205b) forms an arm (211) which is welded in conical form to the welding boss (203). When viewed from the side (cross-sectional view) the top plate (205a) and the bottom plate (205b) forms conical shape at the inner periphery of the stator holder plate (205) to which a welding boss (203), in the middle of the stator holder plate (205), is welded to accommodate the axle of the motor.

[00034] The outer surface of stator holder plate (205) gradually rises from outer periphery of the stator holder plate (205), at a predetermined angle a, till the inner periphery of the stator holder plate (205). As per an embodiment of the present invention, the angle a varies from 5 degrees to 15 degrees. Angle lower than 5 degrees or higher than 15 degrees is detrimental to the rigidity of the system as well as the strength of welded joint.

[00035] Stator is designed in such a way that there is no notch in the stator holder plate (205) and the top plate (205a) and the bottom plate (205b) makes a gradual curve rather than a sharp curve which avoid the creation of stress points on stator holder plate (205) and hence the welding of welding boss (203) with the top plate (205a) and bottom plate (205b), which are curved, provides improved strength as the welding is not done on the same line of plane.

[00036] Fig.4 (a) illustrates zoomed in view of the cross section of the stator holder plate (205). Imaginary line of separation (401) extends an angle from outer periphery of the stator holder plate (205) at an angle (a) with inclined line A (40 la). This gradual rise of the top plate (205a) with respect to the imaginary line of separation (401) forms a cone shape or a substantially convex profile with the welding boss (203). Similarly, the bottom plate (205b) extends in the same manner at an angle (a) and bottom plate (205b) mirroring the top plate (205a). line B (40lb) forms angle (b) with the imaginary line of separation (401). The maximum vibration is generated from the axle of the motor which is inside the welding boss (203) and by increasing the area of contact near the welding boss (203) reduces the chances of cracks building up in the stator holder plate (205). Also, the top plate (205a) and the bottom plate (205b) are kept at a certain distance from each other near the inner periphery of the stator holder plate (205) which is determined by the angle a, which increases the strength and the grip on the welding boss and thereby the weld strength. As per an embodiment of the present invention, angle a is equal to angle b

[00037] Fig. 5, 6, 7 and 8 depicts the motor covers of different structure. Fig.6 and fig. 8 show the rear side of the motor cover which will be hidden from the view when installed on the motor. Fig. 5 and fig. 7 show the front side of the motor cover which is visible to the eyes after installation. A motor cover holds bearing to support large diameter axle as that axle has to carry high current capacity wires. In order to provide additional strength to the motor cover to sustain under severe stress and impact load of the vehicle, plurality of ribs (601,602,603,801,802) are added radially on both the motor covers (refer figure 6 and figure 8, which is depicting the inner structure of the motor cover comprising ribs) to provide necessary strength to the motor cover so as to support the axle.

[00038] As per an embodiment of the present subject matter, the motor cover is provided with two types of ribs. One type of rib which starts from the inner periphery of the motor cover and extends radially towards the outer circumference of the motor cover and another type in which the rib starts from the inner periphery of the motor cover and crosses through the drive pin (603) and the drive pin (603) lies in the middle of the rib. Both types of ribs are arranged in alternate manner. By increasing the rib length from drive pin (and not restricting the length of the ribs till drive pins) to the outer circumference of the motor cover, it allows the motor cover to withstand the impact generated from the axle of the motor and the torque from the power train thereby preventing the cracking of the motor cover. The number of ribs are increased in number in order to provide more strength. Some of the ribs, for example, discontinuous rib (602) are extended beyond the drive pins (603) and extended till the point of the outer circumference of the motor cover.

[00039] In fig .6 discontinuous ribs (602) on drive pins (603) are provided from bearing boss (604) till the motor cover end and continuous ribs (601) are also provided in between two drive pins (603) which run completely from bearing boss (604) to motor cover end.

[00040] In fig. 8 the ribs (801) are provided from bearing boss (802) till motor cover end. When the vehicle is under the effect of lateral vibration, tractor torque and impact load during driving conditions the axle of the motor puts the entire load on the motor cover which leads to formation of the cracks on the motor cover. The present structure of the motor cover with additional ribs and increased thickness of the inner ring (604) reduces the cracks produced on motor when subjected under the impact of the motor axle.

[00041] The present subject matter helps in achieving strengthening of stator to withstand traction forces, torques and road vibrations and achieve better durability at lower cost, ease of manufacturing as well as less variety. The solution explained as per the present subject matter enables having a robust design of the stator & motor cover to be able to configure to vehicles with different powertrains like IC engines, EV, HEV etc.

[00042] Arrows provided in the top right corner of each figure depicts direction with respect to the two-wheeled vehicle, wherein an arrow F denotes front direction, an arrow R indicated Rear direction, Up denotes upward direction and Dw denotes downward direction as and where applicable.

[00043] Many modifications and variations of the present subject matter are possible in the light of above disclosure. Therefore, within the scope of claims of the present subject matter, the present disclosure may be practiced other than as specifically described.

Claims

We claim:

1. An electrical machine for a vehicle, said vehicle comprising:

a wheel (110), said wheel (110) comprising a hub, said hub is provided with a motor, said motor is mounted on an axle of said wheel (110), said motor comprises a rotor and a stator, and said stator of said motor is encased in a stator holder plate (205);

said stator holder plate (205) comprising a top plate (205a) and a bottom plate (205b), said top plate(205a) and said bottom plate (205b) fixedly attached to each other by attaching means (204), said stator holder plate (205) configured to form a plurality of trapezoidal surfaces (202a, 202b, 202c, 202d, 202e and 202f); and said top plate (205a) and said bottom plate (205b) starts from the outer periphery of said stator holder plate (205) and extends towards the inner periphery of said stator holder plate (205) by forming an angle (a) with an imaginary line of separation (401).

2. The electrical machine as claimed in claim 1, wherein an arm (211) is formed between any two adjacent said plurality of trapezoidal surfaces (202a, 202b, 202c, 202d, 202e and 202f).

3. The electrical machine as claimed in claiml or claim 2, wherein said arm (211) is formed with said top plate (205a) and said bottom plate (205b).

4. The electrical machine as claimed in claiml, wherein a line A (40 la) makes angle (a) with said imaginary line of separation (401).

5. The electrical machine as claimed in claiml, wherein a line B (40lb) makes angle (b) with said imaginary line of separation (401) and said angle (b) is in the range of 5 to 15 degrees.

6. The electrical machine as claimed in previous claims, wherein said arm (211) is having substantially conical profile.

7. The electrical machine as claimed in claim 1, wherein said stator holder plate (205) is welded to a welding boss (203) in a at least one of a convex shape or concave shape.

8. The electrical machine as claimed in claim 1, wherein said fastening means are rivets (204 a, 204b, 204c, 204d, 204e and 204f).

9. The electrical machine as claimed in claim 1, wherein said plurality of trapezoidal surfaces (202a, 202b, 202c, 202d, 202e and 202f) are provided with ventilation holes (206).

10. The electrical machine as claimed in claim 1, wherein a constant K is in the range of 1 to 2 and range of a ratio (D1/D2) is 0.2 to 0.4.