TECHNICAL FIELD

[0001] The present subject matter generally relates to an electric machine and particularly but not exclusively relates to a terminal holder assembly for the electric machine.

BACKGROUND OF THE INVENTION

[0002] Typically, an electric machine includes a housing, and a stator assembly housed within the housing. The stator assembly includes a plurality of terminal lead wires to be connected to feed wires emerging from a source of power/electricity. As per International Electrotechnical Commission (IEC) standards, electric machines typically employ a terminal box mounted on a housing of the electric machine. The terminal box houses the connections between the lead wires and the feed wires. Particularly, the terminal box houses the ends of motor wiring leads that are accessible in the terminal box by removing a cover plate of the terminal box.

[0003] Providing an exclusive terminal box typically involves providing a separate haylam platform or a platform made of non-conducting material on the housing of the electric machine, thereby leading to an overall increase in the number of components constituting the electric machine. Further, the terminal box in itself typically includes a plurality of components including a terminal box support member, and different linking members that are used for linking different terminals. Further, most of the terminal boxes include a cover plate for covering the terminals housing the lead wires. Thus, the terminal box is typically large and occupies significant space on the housing of the electric machine, thereby leading to a significant increase in the size of the electric machine. Size of the electric machine has different implications on the product into which the electric machine is packaged. For example, in compact two-wheeled saddle-type vehicles in which space is a constraint, packaging large sized electric machines having a large terminal box becomes difficult. Moreover, in terminal boxes that do not have a cover plate, the terminals are often exposed to dust and water, as the terminal box is mounted on an external surface of the housing of the electric machine.

[0004] In cases where separate terminal boxes are not provided, typically glands are used for sealing the lead wires in order to prevent dust/water from contacting the lead wires. However, individual glands have to be used for sealing each wire separately, adding to the number of components in the electric machine. Moreover, assembly time involved in sealing lead wires individually is significantly long, especially in high rated (three phase or greater) electric machines where the number of lead wires is large. Another technique used for sealing lead wires is potting, where the area around the lead wires is filled with solid or gelatinous compound to prevent moisture from contacting the lead wires and thereby prevent short circuits. However, this technique is cost intensive. Additionally, serviceability of the wires is also affected since removal of potting is cumbersome and it tends to cause damage to the lead wires.

[0005] Therefore, there is a need for providing an improved means for connecting lead wires of the electric machine to the feed wires while ensuring compactness of the electric machine. Additionally, there is also a need to ensure that the lead wires are effectively sealed while ensuring serviceability of the lead wires while also ensuring that the time involved in assembling the sealant for the lead wires is significantly minimized.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The detailed description described with reference to the accompanying figures. The same numbers have been used throughout the drawings to reference like features and components.

[0007] Fig.l is an exploded view depicting parts of an electric machine in accordance with an embodiment of the present subject matter.

[0008] Fig.2 is a detailed exploded view depicting assembly of a terminal holder of the electric machine in accordance with an embodiment of the present subject matter. [0009] Fig.3 is a cross-sectional view of the terminal holder in accordance with an embodiment of the present subject matter.

[00010] Fig.4 is a perspective view of the terminal holder in accordance with an embodiment of the present subject matter.

DETAILED DESCRIPTION BACKGROUND OF THE INVENTION

[00011] Typically, multi phase electric machines including three phase electric machines are used for wide range of applications including automotive applications for powering motor vehicles. These electric machines have a stator that has three or more phases of windings. For example, a three-phase electric machine includes three lead wires/conductors, each carrying an alternating current of the same frequency and voltage. Similarly, other multi phase electric machines have corresponding number of lead wires/conductors, each carrying an alternating current of the same frequency and voltage. Therefore, multi phase electric machines typically have a plurality of lead wires to be connected to corresponding number of feed wires emerging from the power source. Typically, these lead wires are connected to the feed wires of the power source via terminals provided in a terminal box. The terminal boxes containing terminals are secured on an external surface of a housing of the electric machine and occupy a significant area on the external surface of the electric machine, thereby enlarging the overall size of the electric machine. Moreover, the use of terminal boxes also increase the number of components constituting the electric machine. Additionally, since the terminal boxes are disposed on the external surface of the electric machine, the terminals in the terminal boxes are prone to damage due to dust and water entry. In order to prevent damage to the terminals, the terminal boxes are provided with an additional protective cover. In cases where the separate terminal boxes are not provided, typically glands are used for sealing the lead wires in order to prevent dust/water from contacting the lead wires. However, individual glands have to be used for sealing each wire separately, adding to the number of components in the electric machine. Moreover, assembly time involved in sealing lead wires individually is significantly long, especially in high rated (three phase or greater) electric machines where the number of lead wires is large. Another technique used for sealing lead wires is potting, where the area around the lead wires is filled with solid or gelatinous compound to prevent moisture from contacting the lead wires and thereby prevent short circuits. However, this technique is cost intensive. Additionally, serviceability of the wires is also affected since removal of potting is cumbersome and it tends to cause damage to the lead wires. Therefore, there is a need for an improved means for accommodating the lead wires of the electric machine while connecting the lead wires to the feed wires.

[00012] With the above objectives in view, the present subject matter provides an electric machine that comprises a housing that houses a stator assembly operatively connected to a rotor assembly, and a terminal holder that comprises three or more terminals for receiving three or more lead wires emerging from the stator assembly. Particularly, the terminal holder is assembled in a corresponding slot formed on an external surface of the housing. More particularly, the terminal holder is assembled from an inner side of the housing. Further, the terminal holder is assembled in a manner such that a portion of the terminal holder extends partially outside the external surface of the housing, so that the three or more lead wires emerging from the stator assembly can be connected to the corresponding feed wires from a power supply/control unit.

[00013] As per an embodiment of the present subject matter, the terminal holder integrally includes an inner plate and an outer plate wherein the inner plate and the outer plate together hold the three or more terminals. In one embodiment, the inner plate and the outer plate are integrally moulded, wherein the outer plate is formed on the surface of the inner plate. Further, three or more holes are formed in the terminal holder, wherein the three or more holes being formed in both the inner plate and the outer. Particularly, the three or more holes are formed in a manner such that each hole formed on the inner plate is coaxial with a corresponding hole formed in the outer plate. Further, each hole of the three or more holes holds a terminal each of the three or more terminals. Particularly, the terminals are disposed in a manner such that each terminal extends orthogonally from a body of the terminal holder. Additionally, each terminal of three of more terminals has one rim opening towards an inner side of a housing of the electric machine and another rim opening towards an outside of the housing. In other words, while one portion of the terminals faces the inner side of the housing comprising the stator assembly and the rotor assembly, another portion of the terminals faces an outside of the housing. The portion of the terminals facing the stator assembly receives the three or more lead wires emerging from the stator assembly. These lead wires drawn in through the portion of the terminals facing the stator assembly are drawn out through the portion of the terminals facing the outside of the housing for connection with the feed wires. In order to ensure that the lead wires are not exposed to moisture/dust, a sealant member is disposed between the inner plate and the outer plate of the terminal holder. Disposing the sealant member between the inner plate and the outer plate ensures that moisture does not contact the lead wires due to water entry through the holes in the inner plate. Thus, disposing a single sealant member ensures that all the lead wires of the stator assembly are protected and the requirement for providing individual sealant members such as glands for each lead wire is eliminated. Moreover, assembling the terminal holder from the inner side of the housing also ensures that the lead wires that are directly inserted into the portion of terminals extending towards the inner side of the housing are not exposed to dust/moisture.

[00014] As per an aspect of the present subject matter, the terminal holder is very compact and can be easily assembled on an external surface of the housing of the electric machine. For example, as per an embodiment of the present subject matter, the housing of the electric machine includes a front cover and a rear cover configured to be detachably attached to one another for enclosing the stator assembly and the rotor assembly, wherein the rear cover is formed with a corresponding slot for receiving the terminal holder. In one embodiment, the corresponding slot is formed on an external surface that is a circumferential surface of the rear cover. Further, two or more apertures are formed around the slot for detachable attachment of the terminal holder on the external surface of the housing. Thus, a mere slot and few apertures have to be formed on the external surface of the housing of the electric machine for assembling the terminal holder and there is no requirement for mounting a separate terminal box on the external surface of the housing of the electric machine. Therefore, the numbers of components disposed on the external surface of the housing are very few, thereby ensuring that there is no compromise in the strength of the housing. Further, servicing the lead wires is also simple and convenient as it merely involves removal of fasteners securing the terminal holder to the external surface of the housing.

[00015] Thus, the construction of the electric machine including the terminal holder as per the present subject matter is very compact for it to be accommodated in any compact space available, including in automobiles such as two wheeled and three wheeled vehicles. Further, compactness of the electric machine is ensured without compromising on the serviceability of the electric machine, including the parts of the electric machine such as lead wires. In addition, it is ensured that the components of the electric machine are dust proof/water proof while using a single sealant member. Further, since the numbers of components constituting the electric machine are few no complexities are involved during assembly of the electric machine and the assembly time is considerably reduced. Thus, the overall productivity in manufacturing the electric machine is increased while the cost of production is kept minimal.

[00016] Various other features and advantages of the invention are described in detail below with reference to the accompanying drawings. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements.

[00017] Fig.l is an exploded view depicting parts of the electric machine 100 as per an embodiment of the present subject matter. In the present embodiment, the electric machine 100 is a three phase electric machine. The electric machine 100 as per the present embodiment comprises a housing 101 including a front cover 101a and a rear cover 101b. The housing 101 is provided to enclose a stator assembly a stator assembly 102 having a plurality of stator coils 102a arranged around a core of the stator assembly 102 and three or more lead wires 102b extending from the stator coils 102a. The stator assembly 102 is operatively connected to a rotor assembly 103 including a central drive shaft 103a. For the working of the electric machine 100, electrical energy is supplied to the stator assembly via the three or more lead wires 102b. For example, the lead wires 102b of the electric machine 100 are connected to corresponding feed wires (not shown) of a source of power supply such as battery (not shown). The passage of electrical energy through the plurality of stator coils 102a produces a magnetic field around the rotor assembly 103 whose drive shaft 103a is inserted in the core of the stator assembly 102, causing the drive shaft 103a to rotate. Spinning or rotation of the rotor assembly 103 generates mechanical energy that may in turn be used to power different devices including automobiles such as two-wheelers and three-wheelers. Thus, passage of electricity through the three or more lead wires 102b of the stator assembly 102 is key to the working of the electric machine 100. The three or more lead wires 102b have to be safely secured/connected to the feed wires to ensure seamless flow of electricity to the stator assembly 102. Any damage to the three or more lead wires 102b of the stator assembly 102 is therefore not desirable. It is especially important to protect the three or more lead wires 102b more damage due to moisture/water entry. The three or more lead wires 102b are typically prone to damage due to water/dust entry because the three or more lead wires 102b are drawn outside the housing 101 of the electric machine 100 for connection to the feed wires through corresponding terminals/connectors, exposing them to water and dust.

[00018] In order to protect the three or more lead wires 102b from damage, the electric machine as per the present subject matter and as may be seen in Fig.l comprises a terminal holder 104 configured to receive the three or more lead wires 102b from the stator assembly 102. In the present embodiment and as may be seen in Fig.l and Fig.2, the terminal holder 103 is assembled from an inner side of the housing 101 to an external surface 101c of the housing 101. Particularly, in the present embodiment as may be seen in Fig.l and Fig.2, the terminal holder 104 is assembled on the rear cover 101b of the housing 101. The terminal holder 104 is assembled in a corresponding slot 105 formed on an external surface 101c (shown in Fig.2) of the housing 101. In the present embodiment, the corresponding slot 105 is formed on the rear cover 101b of the housing 101. In another embodiment, the corresponding slot 105 can also be formed on the rear cover 101b of the housing 101. The terminal holder 104 is assembled in the corresponding slot 105 from the inner side of the housing 101. In the present embodiment, the terminal holder 104 is assembled in the corresponding slot 105 from the inner side of the rear cover 101b. For example, as may be seen in Fig.2, the terminal holder 104 is located in the corresponding slot 105 from the inner side of the rear cover 101b. Once located in the corresponding slot 105 formed on the rear cover 101b, the terminal holder 104 is fastened to the rear cover 101b. As may be seen, fasteners 108 are used to fasten the terminal holder 104 to the external surface 101c of the rear cover. Two or more apertures 109 are formed around the corresponding slot 105 for receiving fasteners 108 used to fasten the terminal holder 104. In the present embodiment, the terminal holder 104 is assembled on the rear cover 101b once the primary components of the electric machine such as the stator assembly 102 and the rotor assembly have been assembled. For example, in the present embodiment, the stator assembly 102 including the plurality of stator coils 102a is press fitted onto the front cover 101a predisposed with a front end bearing 110. Further, the rotor assembly 103 including the drive shaft 103a is inserted into the core of the stator assembly 102 from a non-drive end, wherein a portion of the drive shaft 103a facing the rear cover 101b constitutes the non-drive end. In other words, it can be stated that in the present embodiment, the rear cover 101b constitutes the non-drive side of the electric machine 100 and the front cover 101a constitutes the drive side of the electric machine 100. Subsequently, the terminal holder 104 is assembled onto the rear cover 101b. Further, the three or more lead wires 102b emerging from the stator assembly 102 are connected to the terminal holder 104. Finally, the rear cover 101b is attached to the front cover 101a to complete the housing 101 and also the electric machine 100. [00019] Fig.3-Fig.4 exemplify the construction of the terminal holder 104 as per an embodiment of the present subject matter. Fig.3 illustrates a perspective view of the terminal holder 104. As may be seen in Fig.3, the terminal holder 104 comprises an inner plate 104a and an outer plate 104b. In the present embodiment, the inner plate 104a and the outer plate 104b are integrally moulded. Particularly, the inner plate 104a and the outer plate 104b are formed in such a way that the inner plate 104a is longer than the outer plate 104b. The portions of the inner plate 104a that extend away from the outer plate 104b are formed with two or more corresponding apertures 112 that will be coaxially held with two or more apertures 109 formed around the slot 105 to enable detachable attachment of the terminal holder 104 on the external surface 101c of the housing 101. In a substantially central portion of the terminal holder, both the inner plate 104a and the outer plate 104b are formed with three or more holes 106, wherein each hole of the three or more holes 106 on the inner plate 104a is formed to be coaxial with the corresponding hole of the three or more holes 106 formed on the outer plate 104b. Further, each hole of the three or more holes 106 formed on the terminal holder 104 is configured to hold one terminal 107 each. Thus, the terminal holder 104 as per the present embodiment is configured to hold three or more terminals 107. Each terminal of the three or more terminals 107 extends orthogonally from the body of the terminal holder 104. Further, while one portion of the terminals faces the inner side of the housing 101 (shown in Fig.l) comprising the stator assembly 102 (shown in Fig.l) and the rotor assembly 103 (shown in Fig.l), another portion of the terminals faces an outside of the housing 101. The portion of the terminals facing the stator assembly 102 receives the three or more lead wires 102b (shown in Fig.l) emerging from the stator assembly 102. These lead wires 102b are drawn in through the portion of the terminals facing the stator assembly 102 and are drawn out through the portion of the terminals facing the outside of the housing 101 for connection with the feed wires (not shown).

[00020] Fig.4 illustrates a cross sectional view of the terminal holder 104 as per an embodiment of the present subject matter. The terminal holder 104 is an integral member and as may be seen in Fig.3 is formed in the form of a step and comprises an integrally moulded inner plate 104a and the outer plate 104b. Further, the terminal holder 104 comprises three or more holes 106 for receiving three or more terminals 107. As may be seen, while one portion of said terminals 107 extends away from the inner plate 104a towards a stator assembly of the electric machine, other portion of said terminals 107 extends away from the outer plate 104b towards the outside of the housing 101 (shown in Fig.l) including the rear cover 101b. In order to prevent water or dust from damaging the three or more lead wires 102b (shown in Fig.l), due to water entry through the three or more holes 106, the terminal holder 104 is provided with a sealant member 114 disposed between the inner plate 104a and the outer plate 104b. Particularly, the sealant member 114 is disposed on the step formed between the inner plate 104a and the outer plate 104b. Presence of the sealant member 114 ensures that no sealant members such as glands have to be individually provided for each lead wire accommodated in the terminals. Further, the construction of the terminal holder 104 as per the present subject matter also ensures that the lead wires can be easily serviced by merely dismantling the terminal holder 104 without the need for dismantling individual sealant members that were previously provided.

[00021] As can be made out from the teachings of the present subject matter, the construction of the electric machine including the terminal holder is very compact and can be used for variety of applications including automotive applications where compactness is much desired. The teachings of the present subject matter offer a cost effective and reliable solution for preventing water/dust entry into the lead wires while also ensuring effective servicing of the lead wires.

[00022] Improvements and modifications may be incorporated herein without deviating from the scope of the invention.