Patent Application
20080019856
Now, referring to
The electric pump 1 includes a motor portion 10 for driving a rotary shaft 11, a first pressed member 20 for holding a first rolling ball bearing (bearing member) 21 which rotatably supports the rotary shaft 11, a second pressed member 30 formed with a recess 30a for receiving an inner rotor 31 of the trochoid pump, and a pump plate 40 for covering the recess 30a. According to the present invention, the pump case which has been produced by mechanical work from an aluminum die casting or a cast product as material, in the conventional electric pump as shown in
The motor portion 10 includes a motor rotor 12 having the rotary shaft 11, and a motor stator 14 which is provided on an outer periphery of the motor rotor 12. The motor rotor 12 has a permanent magnet 13 in a cylindrical shape fixed to an outer periphery of the rotary shaft 11. The motor stator 14 includes a stator core 15 having a plurality of teeth, and a coil 17 which is wound around the stator core 15 with interposing an insulator 16. The above described motor portion 10 is contained in a motor case 18. The rotary shaft 11 is rotatably supported by the first rolling ball bearing 21 which is held by the first pressed member 20 and the second rolling ball bearing 19 which is held by the motor case 18.
The first pressed member 20 is formed of a metal plate and produced by deep-drawing work. The first pressed member 20 has a cylindrical part 20a which is formed in its center part, a flat part 20b opposed to the second pressed member 30, and a spigot joint part 20c which is cylindrically formed on its outer circumference. A seal member 22 in an annular shape for preventing oil in the recess 30a of the second pressed member 30 from intruding into the motor portion 10 is press-fitted to an inner periphery of the cylindrical part 20a as the holding portion, and the first rolling ball bearing 21 is secured and supported, by caulking an end portion 20d of the cylindrical part 20a. An end portion 18a of the motor case 18 is coupled to the spigot joint part 20c by caulking.
The second pressed member 30 is formed of a metal plate and produced by deep-drawing work, in the same manner as the first pressed member 20. The second pressed member 30 has the recess 30a which contains the inner rotor 31, a through hole 30b formed in its center part, a flat part 30c opposed to the flat part 20b of the first pressed member 20, and a flat part 30d opposed to the pump plate 40. An outer rotor 32 in mesh with the inner rotor 31 is provided on an inner periphery of the recess 30a. The outer rotor 32 is provided having its rotation center offset from a rotation center of the inner rotor 31, and has the number of teeth which is larger than the number of teeth of the inner rotor 31. An outer periphery of the outer rotor 32 is rotatably supported by the inner peripheral face of the recess 30a. The rotary shaft 11 of the motor portion 10 is passed through the through hole 30b. The inner rotor 31 is fixed to the tip end of the rotary shaft 11, whereby the inner rotor 31 will be driven to rotate.
A liquid-tight packing 33 formed of paper packing or the like is interposed between the flat part 20b of the first pressed member 20 and the flat part 30c of the second pressed member 30. The flat part 20b and the flat part 30c are coupled together by spot welding. The first pressed member 20 and the second pressed member 30 are coupled to each other in this manner, whereby the oil in the recess 30a is prevented from leaking through a coupled part between the first pressed member 20 and the second pressed member 30.
The pump plate 40 is formed in a plate-like shape, and has a suction port 40a for sucking the oil into the recess 30a, a discharge port 40b for discharging the oil from the recess 30a, and a groove 40c in which an O-ring 41 is fitted. The suction port 40a and the discharge port 40b are formed in the pump plate 40 in a manner of passing it through. The groove 40c is formed so as to be opposed to the flat part 30d of the second pressed member 30, and the oil is prevented from leaking through a gap between the pump plate 40 and the second pressed member 30 by the O-ring 41 which has been fitted in the groove.
In the electric pump 1 having the above described structure, a bracket for securing and supporting the electric pump 1 may be integrally formed with the second pressed member 30.
Then, operation of the electric 1 will be described. This electric pump 1 will be operated, when electric current to the coil 17 of the motor stator 14 is supplied and controlled by a control device which is not shown. When the electric current has been supplied to the coil 17, the motor rotor 12 is rotated, and in association with this rotation, the inner rotor 31 fixed to the rotary shaft 11 is rotated. As the inner rotor 31 is rotated, the outer rotor 32 in mesh with the inner rotor 31 is also rotated. Since the number of the teeth of the inner rotor 31 is smaller than the number of the teeth of the outer rotor 32, the outer rotor 32 will rotate with the smaller rotation number than the inner rotor 31. For this reason, while the inner rotor makes one rotation, a position and a capacity of a space which is formed between the inner rotor 31 and the outer rotor 32 will be sequentially displaced. When the capacity has become larger, the pressure is lowered so as to suck the oil from the suction port 40a, and when the capacity has become smaller, the pressure is increased so as to push out the oil from the discharge port 40b. In this manner, pumping action is generated between the inner rotor 31 and the outer rotor 32, whereby the oil is supplied from the electric pump 1 under pressure.
According to the electric pump in the above described first embodiment, the following advantages can be obtained.
(1) In the first embodiment, the pump case of the electric pump 1 is constructed by coupling the first pressed member 20 having the cylindrical part 20a for holding the first rolling ball bearing 21 which rotatably supports the rotary shaft 11, and the second pressed member 30 in which the recess 30a for receiving the inner rotor 31 which is provided at the tip end of the rotary shaft 11 to each other. As described, because the pump case is constructed by coupling the first pressed member 20 and the second pressed member 30 which have been formed by deep-drawing work to each other, it is possible to simplify the structure and to reduce the cost, as compared with the expensive pump case in the related art which has been produced by mechanical work with high precision employing an aluminum die casting or a cast product as the material. Moreover, because the pump case is composed of the pressed members 20 and 30, useless thickness of the pump case can be saved, and weight reduction can be achieved. The structure of the pump case employing the pressed members 20, 30 can be favorably utilized in the electric pump in which a level of working precision required for the pump case in not so high, for example, the electric pump which is used in the low pressure region of about 0.1 MPa, such as the electric pump for cooling the motor in the hybrid vehicle or the like.
(2) In the first embodiment, the first pressed member 20 and the second pressed member 30 are coupled together with interposing the liquid-tight packing 33 between the flat part 20b and the flat part 30c. As the results, it is possible to prevent the pressure of the oil supplied from the electric pump 1 from being lowered due to leakage of the oil in the recess 30a through the coupled part between the first pressed member 20 and the second pressed member 30.
(3) In the first embodiment, the seal member 22 is press-fitted to the inner periphery of the cylindrical part 20a of the first pressed member 20, and the first rolling ball bearing 21 is secured and supported by caulking the end portion 20d of the cylindrical part 20a. As the results, it is possible to construct the first pressed member 20 as a housing in which the seal member 22 and the first rolling ball bearing 21 are unitized, and hence, the electric pump 1 can be easily handled in its assembling step.
(4) In the first embodiment, it is possible to form the bracket for securing and supporting the electric pump 1 integrally with the second pressed member 30. By providing the bracket part 30e on the second pressed member 30, there is no necessity of providing a bracket member which has been separately attached to the pump plate 40 or the like in the prior case. As the results, the number of components can be reduced and the assembling steps can be shortened, whereby the production cost can be reduced.
Now, referring to
According to the electric pump in the above described second embodiment, in addition to the advantages (1) to (3) in the first embodiment, the following advantages can be obtained.
(5) In the second embodiment, the motor case part 20e which contains the motor portion 10 of the electric pump 2 is integrally formed with the first pressed member 20. Therefore, by integrally forming the motor case which is generally formed of a pressed member, it is possible to reduce the number of components and the production cost.
Further, the above described embodiments can be modified as follows;
Although the invention is applied to the electric pumps 1, 2 for driving the trochoid pump in the first and second embodiments, it is also possible to apply the invention to an electric pump for driving other internal gear pumps besides the trochoid pump.
Although the first pressed member 20 and the second pressed member 30 are coupled together by spot welding in the first and second embodiments, it is also possible to couple the first pressed member 20 and the second pressed member by other means such as caulking.
Although the electric pumps 1, 2 are hydraulic pumps for supplying oil under pressure in the first and second embodiments, it is also possible to apply the invention to an electric pump for supplying other liquid than oil, such as water.
Although the bearing member for rotatably supporting the rotary shaft 11 is the rolling ball bearings 19, 21 in the first and second embodiments, the bearing member may include a roller bearing, or other bearings than the rolling bearing.
The structures of the electric pumps 1, 2 in the first and second embodiments can be favorably utilized in the electric pump to be used in the low pressure region. However, the structures of the electric pumps 1, 2 may be utilized in the electric pump to be used in the higher pressure region, depending on precision of the pressing work of the first pressed member 20 and the second pressing member 30. Specifically, in case where the precision of the stamping work of the pressed members 20, 30 can be improved, the sealing performance or the like can be enhanced, and therefore, it is possible to apply the structure of the invention to the electric pump to be used in the higher pressure region.
| Number | Date | Country | Kind |
|---|---|---|---|
| P2006-199315 | Jul 2006 | JP | national |
