FIELD OF THE INVENTION

The present invention relates to an electric water pump with improved shaft. More particularly, the present invention relates to an electrically controlled BLDC motor based electric water pump equipped with a symmetrical hex shaped shaft having grooves on its both ends for providing a greater breaking torque and to increase breaking axial force during undesirable rotational and axial motion of shaft and having applications in cabin heating, cooling of engine, inverter and battery in electric/hybrid vehicles.

BACKGROUND OF THE INVENTION

Conventionally, water pumps are driven by a belt attached to the crankshaft of internal combustion engine which takes mechanical power from the engine to circulate coolant through the engine and heater to cool the engine or heat the vehicle's occupant cabin. The rotational speed of internal combustion engine is responsible for determining the amount of refrigerant flowing out of the mechanical water pump. Therefore, in order to operate the heater and the radiator normally, the engine speed must be increased. Thus, on increasing the engine speed the fuel consumption also increases.

At present, in contrast with the mechanical water pump, the large number of vehicles are shifted towards an electric water pump since the electric water pump is capable of determining the amount of refrigerant regardless of the rotational speed of the internal combustion engine. The electric water pump is driven by an electric motor and is controlled by a controlling unit. The electrically driven water pump employed in the electric /hybrid vehicles is used for the cooling of its components. During the operation of electric water pump, sometimes the rotor shaft produces an undesirable rotational and axial movement in the rotor casing assembly which may cause vibration and creates negative effect on the efficiency of the pump.

JP2011106438A discloses an electric water pump with improved operating performance and improved durability comprising a vortex chamber is formed between a stator that generates a magnetic field by a control signal applied from outside, a rotor that rotates by a magnetic field generated by the stator, a pump cover i.e. volute casing that includes a cooling water inlet and a cooling water outlet, and a pump cover. A stator chamber formed on a front surface and an outer peripheral portion to which a stator is mounted, a body including a rotor chamber formed on an inner peripheral portion of the stator chamber and mounted with a rotor, and a rotor having a central axis A shaft mounted on the rotor chamber by rotating with it, an impeller fixed to the front end of the shaft and pressurized with cooling water flowing through the inlet to be mounted on the vortex chamber, and mounted on the rear end of the body A driver case with a case surface formed and a rear surface opened and a driver chamber formed inside, a control signal to the stator attached to the driver chamber Including the driver to be applied. The disadvantage of cited document is that the normal design of rotor shaft produces axial movement and may cause vibration in the pump.

Therefore, in order to overcome the aforementioned drawback, there exists a need to develop highly reliable and affordable electric water pump having an improved shaft that prevents undesirable rotational motion and axial movement of shaft in rotor casing assembly in order to maintain the smooth functioning of the electric pump.

OBJECT OF THE INVENTION

The main object of the present invention is to provide an electrically controlled BTDC Motor based electric water pump having applications in cabin heating, low pressure EGR cooling, battery cooling, inverter cooling and alike.

Another object of the present invention is to provide an improved shaft with grooves on its both ends inserted in the rotor casing to avoid undesirable rotational motion and axial movement of shaft in the rotor casing assembly.

Another object of the present invention is to develop a symmetrical shaped hex shaft for minimizing the risk of wrong loading of shaft which leads to part failure during manufacturing of rotor casing.

Still another object of the present invention is to develop an electric water pump with improved shaft that is highly reliable, efficient and cost effective.

SUMMARY OF THE INVENTION The present invention relates to an electric water pump with improved shaft having grooves on its both ends to provide a greater breaking torque and resist the rotational motion of shaft in the rotor casing. Moreover, the improved shaft provides an increased breaking axial force and resists the axial force acting on the shaft thereby maintaining the smooth functioning of the pump.

In an embodiment, the present invention provides an electric pump with improved shaft comprising of a volute casing; a washer; a housing with at least two mounting assembly; a rotor assembly; a cylindrical bush with grooves embedded in the rotor assembly; a rotor; a rotor casing; a shaft insert molded in the rotor casing; a stator assembly; a printed circuit board (PCB); a self-tapping screw; and a cover for covering lower part of pump; wherein, the rotor casing is made up of resin including but not limited to polyphenylene sulphide (PPS), polyphthalamide (PPA) and other synthetic resins; the housing accommodates plurality of electric pump components such as stator assembly, rotor assembly, rotor casing, cylindrical bush and PCB; the shaft is of preferably symmetric hex shape with grooves at its both ends; the hex shape of shaft at both ends provide a much greater breaking torque to resist the undesirable rotational moment of shaft in rotor casing; and the grooves on both ends of shaft provide an increased breaking axial force to resist the axial forces acting on the shaft and thus maintaining the reliability of the electric water pump.

BRIEF DESCRIPTION OF THE DRAWINGS

The object of the invention may be understood in more details and more particularly description of the invention briefly summarized above by reference to certain embodiments thereof which are illustrated in the appended drawings, which drawings form a part of this specification. It is to be noted, however, that the appended drawings illustrate preferred embodiments of the invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective equivalent embodiments.

Fig. 1 represents an exploded view of electric water pump with improved shaft in accordance with an embodiment of the present invention. Fig. 2 represents a side view of electric water pump with improved shaft in accordance with an embodiment of the present invention.

Fig. 3 represents a cross-sectional view of electric water pump with improved shaft in accordance with an embodiment of the present invention.

Fig. 4(a) represents an improved shaft with grooves in accordance with an embodiment of the present invention.

Fig. 4(b) represents exploded view of shaft with rotor casing in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Many aspects of the invention can be better understood with references made to the drawings below. The components in the drawings are not necessarily drawn to scale. Instead, emphasis is placed upon clearly illustrating the components of the present invention. Moreover, like reference numerals designate corresponding parts through the several views in the drawings. Before explaining at least one embodiment of the invention, it is to be understood that the embodiments of the invention are not limited in their application to the details of construction and to the arrangement of the components set forth in the following description or illustrated in the drawings. The embodiments of the invention are capable of being practiced and carried out in various ways. In addition, the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.

The present invention discloses the electric water pump having symmetrical hex shaped shaft with grooves on its both ends. Moreover, the hex shape at both ends of shaft provide greater breaking torque and the grooves at both ends of shaft provide greater breaking axial force to resist the axial forces acting on the shaft.

In an embodiment referring to Fig. 1 and Fig. 2, the exploded and side view of the electric water pump is illustrated. Said electric water pump 100 with improved shaft comprising of a volute casing 1; a washer 2; a housing 3; a mounting assembly 3(a); a rotor assembly 4; a rotor 5; a rotor casing 6; a symmetrical hex shaped shaft 7 with at least two grooves on both the shaft ends; a stator assembly 8; a PCB 9; a self-tapping screw 10; and a cover 11. The side view of the electric water pump 100 comprising a volute casing 1; a housing 3 with at least two mounting assembly 3(a) and 3b and a cover 11 is depicted in Fig. 2.

Now referring to Fig. 3, a cross-sectional view of the electric water pump with improved shaft is illustrated. Said electric water pump 100 with improved shaft comprises of a volute casing 1 mounted on upper part of pump; a washer 2; a housing 3 for accommodating plurality of electric pump components such as a rotor assembly 4, a cylindrical bush 12 with grooves embedded in the rotor assembly 4, a rotor 5, a rotor casing 6 for holding a symmetrical hex shaped shaft 7 and a PCB 9; and a cover 11 for covering lower part of electric pump.

Now referring to Fig. 4(a), an improved design of shaft 7 with grooves on its both ends 7(a) and 7(b) is illustrated and Fig. 4(b) represents exploded view of shaft 12 with rotor casing 6. The shaft 7 with symmetric hex shape and grooves at both the ends 7(a) and 7(b) is inserted in the rotor casing 6 which is preferably made up of resin PPS. The improved shaft 7 with symmetric hex at both ends 7(a) and 7(b) provide greater breaking torque in order to resist the rotational moment of shaft 7 in the rotor casing 6 and the grooves at both ends 7(a) and 7(b) increases the breaking axial force to resist the axial forces acting on the shaft 7. The improved shaft provides a minimum breaking torque of 4.0 N-m and a minimum breaking axial force of 690 N.

Hence, the present invention provides a highly efficient and affordable 40 W electrically controlled BTDC motor based electric water pump 100 with improved shaft 7 having applications in cooling of engine, power electronics inverter and battery in electric /hybrid vehicles. During the operation of electric water pump 100, a rotational and axial motion of shaft 7 in the rotor casing 6 causes a negative effect on efficiency of the water pump. Therefore, in order to avoid such undesirable movement of shaft 7, the electric pump is equipped with an improved shaft 7 having grooves on its both ends 7(a) and 7(b).

The symmetric hex shape at both ends 7(a) and 7(b) of shaft 7 provide greater breaking torque and resist the undesirable rotational motion of shaft in the rotor casing 6. The symmetric design of shaft 7 also removes the risk of wrong loading of shaft 7 that leads to part failure during the manufacturing of rotor casing 6 and in order to resist the axial force acting on the shaft 7, grooves are provided at both the ends 7(a) and 7(b) to increase breaking axial force and thus maintains the smooth functioning, reliability and efficiency of the water pump.

The foregoing description of embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principals of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated.