JP2012097585A - Electric pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric pump capable of enhancing its efficiency.SOLUTION: This electric pump is so set that the least common multiple of the number of magnetic poles of a motor and the number of slots may become integral multiple of the number of teeth of a pump rotor, and also a relative angle between a motor rotor and the pump rotor is so set that the maximum necessary torque timing by the pulsation of the pump may not coincide with the minimum torque output timing by the pulsation of the motor.

Description

  The present invention relates to a pump driven by an electric motor.

  Conventionally, the technique of patent document 1 is disclosed as a trochoid type oil pump which has a pump rotor and an outer rotor. In this publication, a drive shaft fixed in the pump rotor and an electric motor are connected, and the pump is driven by the electric motor.

JP 2009-68408 A

However, in the electric pump described in Patent Document 1, in order to maintain a stable pump discharge state, it is necessary to maintain a relationship in which the torque output by the electric motor is larger than the torque required for the pump. At this time, if the pulsation of the pump and the pulsation accompanying the torque fluctuation of the electric motor are individually generated, it is necessary to output a larger torque on the electric motor side, which may cause a decrease in efficiency of the pump.
An object of the present invention is to provide an electric pump capable of improving efficiency.

  In order to achieve the above object, the electric pump according to the present invention is set so that the least common multiple of the number of magnetic poles and the number of slots of the motor is an integral multiple of the number of teeth of the pump rotor, and the required maximum torque due to pump pulsation (Maximum torque required for the pump at a certain time: varies depending on the load acting on the pump) and minimum torque due to motor pulsation (minimum value when the current flowing through the motor is a predetermined value: if the current value changes) The relative angle between the motor rotor and the pump rotor was set so that the output timing did not match (the minimum value also changed).

  Therefore, the torque output from the permanent magnet motor can be reduced, and a highly efficient electric pump can be provided.

It is a front view of the electric pump of Example 1. It is a side view of the electric pump of Example 1. It is BB sectional drawing of the electric pump of Example 1. FIG. It is a disassembled perspective view of the electric pump of Example 1. FIG. It is AA sectional drawing of the electric pump of Example 1. FIG. It is a figure showing the relative angle of the pump element of the electric pump of Example 1, and a motor element. It is a characteristic view showing the mode of torque fluctuation in the composition where the pulsation frequency of the motor element and the pulsation frequency of the pump element are different. It is a characteristic view showing the mode of torque fluctuation in the composition where the pulsation frequency of the motor element of Example 1 and the pulsation frequency of the pump element correspond.

[Example 1]
A first embodiment of the present invention will be described with reference to the drawings. 1 is a front view of the electric pump according to the first embodiment, FIG. 2 is a side view of the electric pump according to the first embodiment, FIG. 3 is a cross-sectional view taken along line BB of the electric pump according to the first embodiment, and FIG. FIG. 5 is an AA sectional view of the electric pump according to the first embodiment. The electric pump according to the first embodiment is a pump mounted for an automatic transmission of a vehicle having an idle stop function. This automatic transmission is a belt-type continuously variable transmission, and is separately provided with a main pump driven by an engine. When the engine is stopped by the idle stop control, the hydraulic pressure by the main pump cannot be secured, and if the hydraulic pressure decreases due to a frictional engagement element in the belt-type continuously variable transmission or a leak from the pulley, the hydraulic pressure required for restarting Since it takes time to secure the operability, drivability is reduced. Therefore, in addition to the main pump, an electric pump that can discharge the hydraulic pressure regardless of the operating state of the engine is provided, and by ensuring the hydraulic pressure corresponding to the leakage from the frictional engagement element and pulley, the engine can be restarted and restarted. Improved drivability.

  The electric pump according to the first embodiment includes a pump element including a pump rotor 22 having external teeth and an outer rotor 21 having internal teeth, and a motor element including a motor rotor 33 connected to the pump rotor 22 and a stator 3. And have. These pump element and motor element are accommodated in one center housing 2. The center housing 2 has an opening at both ends toward the outside in the axial direction, and a cylindrical pump housing portion 2a in which a pump element housing portion 24 for rotatably housing the outer rotor 21 is formed on the inner periphery of one opening. A motor housing portion 2b is formed in the inner periphery of the other opening so as to fix and support the stator 3 and house a motor rotor and the like inside. Further, the motor housing portion 2b is mounted on the outer side in the axial direction for attaching to the automatic transmission. The bracket 2c is formed. 5, the center housing 2 includes a cylindrical support portion 2d that rotatably supports the rotor drive shaft 32, and the cylindrical support portion 2d that is connected to the center housing 2. A partition wall is connected to the outer periphery and defines a space between the pump housing portion 2a and the motor housing portion 2b. A seal member that supports the rotor drive shaft 32 on the inner periphery of the cylindrical support portion 2d and seals between the rotor drive shaft 32 and the inner periphery of the cylindrical support portion 2d at the end on the motor housing portion 2b side. 31 is provided.

  The pump cover 1 has a discharge port 11 extending in a cylindrical shape that communicates with the discharge region of the pump element, and a suction port 12 that communicates with the suction region of the pump element. A seal ring groove 11 a to which a seal ring 11 b is attached is formed on the outer periphery of the discharge port 11 at the tip end. The pump cover 1 has bolt holes 13 formed at three locations in the circumferential direction, and is fastened and fixed to the bolt holes 23 formed in the center housing 2 by bolts 14. The motor cover 4 that closes the motor housing portion 2b includes a closing surface 41 that closes the motor housing portion 2b, and a cylindrical standing portion 42 that is erected from the closing surface 41 and inserted into the inner wall of the motor housing portion 2b. And a flange surface 43 provided with a through hole through which the bolt 5 penetrates while the seal member 16 is pressed against the flange surface of the bracket 2c. Thereby, the inside of the motor accommodating part 2b is comprised as a drying chamber, and the inside of the pump accommodating part 2a and a pump outer periphery are comprised as a wet chamber.

  The pump element includes a pump rotor 22 having an external number of teeth Nr = 12, and an outer rotor 21 having an internal number of teeth of 13. The pump rotor 22 has a connecting hole 22a having a two-sided width at the center, and is fitted with a two-sided width 32a formed at the pump side end of the rotor drive shaft 32. As a result, the relative position in the rotational direction between the rotor drive shaft 32 and the pump rotor 22 is determined and power is transmitted.

  The motor element includes a motor rotor 33 having a magnetic pole number Nm = 4 and a stator 3 having a slot number Ns = 6. That is, the coils 35 are wound around the six teeth formed on the stator core 34 of the stator 3 to form slots. The motor rotor 33 is a cylindrical member having a substantially U-shaped cross section, and four permanent magnets 331 and 332 are attached to the outer circumference of the cylinder so that N poles and S poles are alternately arranged. A connecting hole 33a having a two-sided width is formed at the center of the support surface that closes the cylinder of the motor rotor 33, and is fitted to a two-sided width 32b formed at the motor side end of the rotor drive shaft 32. As a result, the relative position in the rotational direction between the rotor drive shaft 32 and the motor rotor 33 is determined and power is transmitted. The positional relationship based on the rotation angles of the pump rotor 22, the rotor drive shaft 32, and the motor rotor 33 will be described later.

  As shown in FIG. 5, an electric pump housing portion that houses the electric pump is formed in the housing 100 of the automatic transmission. Specifically, a discharge oil passage 103 for supplying hydraulic pressure to a control valve unit (not shown), a suction oil passage opening 102 communicating with the suction port 12 in a state where the pump portion of the electric pump is accommodated, and a suction oil passage A pump support opening 101 having a diameter larger than that of the opening 102 and having substantially the same diameter as the outer periphery of the motor housing portion 2b of the center housing 2, and a tapered surface 15 formed on the outer opening edge of the housing 100 of the pump support opening 101; Have The discharge oil passage 103 is substantially the same as the outer diameter of the discharge port 11 and is fitted and supported by insertion. The suction oil passage opening 102 is a cylindrical space formed at a position surrounding the discharge oil passage 103, and communicates with an oil suction opening that opens in an oil pan (not shown). Moreover, the pump support opening 101 supports the electric pump in the radial direction by fitting between the outer periphery of the motor housing portion 2b. Further, the taper surface 15 holds the seal ring 15 between the outer periphery of the motor housing portion 2b. The electric pump is fastened and fixed to the side wall of the housing 100 by bolts 5.

(For pulse operation of electric pump)
In the electric pump, the rotor drive shaft 32 is driven by driving the motor element, and the pump rotor 22 of the pump element rotates, thereby fluid discharge. At this time, in the motor element, pulsation (cogging torque) is generated between the permanent magnet of the motor rotor 33 and the coil 35 of the stator 3. Further, in the pump element, pulsation occurs when suction and discharge are repeated. FIG. 7 is a characteristic diagram showing a state of torque fluctuation in a configuration in which the pulsation frequency of the motor element and the pulsation frequency of the pump element are different.
The motor pulsation frequency and the pump pulsation frequency are expressed as follows.
Motor pulsation frequency fm: (the least common multiple of the number of magnetic poles Nm and the number of slots Ns) × the number of revolutions N
Pump pulsation frequency fr: number of teeth Nr × number of rotations N
For example,
When N = 50 rps (3000 rpm), Nm = 6, and Ns = 9, fm = 18 × 50 = 900 Hz
When Nr = 7, fr = 7 × 50 = 350 Hz
Thus, if the motor pulsation frequency fm and the pump pulsation frequency fr are different, and the torque peak generated by the motor is deviated at the peak where the pump rotor 22 requires the most torque, the torque transmission is efficiently performed. Can not. That is, unless the output torque of the motor is increased as a whole, the torque required by the pump rotor 22 cannot be applied, and wasteful power must be supplied.

Therefore, Nm, Ns, and Nr are adjusted so that fm / fr = integer, and the pulsation frequencies are substantially matched. In particular, when fm / fr = 1 (fm = fr), the highest efficiency is obtained.
Therefore, in Example 1,
When n = 50 rps (3000 rpm), Nm = 4, Ns = 6,
fm = 12 × 50 = 600 Hz
If Nr = 12, then
fr = 12 × 50 = 600 Hz
Thus, fm / fr = 600 Hz / 600 Hz = 1 (integer) is achieved. Thus, the highest efficiency can be obtained when the timing at which a large torque is required in the pump element and the torque peak of the motor are matched.
However, if the pump element and the motor element have the same pulsation frequency and the pump element is in a phase that outputs the smallest torque at the timing when the largest torque is required, the motor element Needs to exceed the maximum torque of the pump element, and unnecessary power is required. In other words, if the timing at which the motor element outputs the smallest torque and the timing at which the pump element requires the largest torque are shifted, the efficiency is improved, and the motor element outputs the smallest torque. Maximum efficiency is achieved when the timing matches the timing at which the pump element requires the least torque.

FIG. 6 is a diagram showing a relative angle between the pump element and the motor element of the electric pump according to the first embodiment, and FIG. 8 is a state of torque fluctuation in a configuration in which the pulsation frequency of the motor element and the pulsation frequency of the pump element according to the first embodiment match. FIG. In this way, the relative positions of the pump rotor 22 and the motor rotor 33 are adjusted so that the pulsation frequencies of the motor element and the pump element coincide with each other, and the peak positions of the pulsation torque coincide with each other. The center of the magnet 331 is shifted by θ. This shift in the relative angle is caused by the number of magnet poles, the number of slots, and the order of energization of the coils, whereby the pulsation torque peaks can be matched. This relative angle may be adjusted by the relative angle of the two-surface width formed at both ends of the rotor drive shaft 32, or may be adjusted by the relative angle of the coupling holes 22a and 33a.
The timing at which the maximum torque of the pump is required and the maximum torque peak of the motor, or the timing at which the minimum torque of the pump is required and the minimum torque peak of the motor may be deviated without departing from the present invention (for example, , 1/4 phase).

[effect]
Hereinafter, the effects of the electric pump ascertained from the first embodiment will be listed.
(1) A permanent magnet motor having a motor rotor 33 having a plurality of magnetic poles and a stator 3 having a plurality of slots, a rotor drive shaft 32 connected to the motor rotor 33, and a plurality of teeth connected to the rotor drive shaft 32 And a pump that converts the transmitted torque into fluid discharge work, and the least common multiple (= 12) of the number of magnetic poles Nm (= 4) and the number of slots Ns (= 6), Nm, Ns, and Nr are set so as to be an integral multiple (= 1) of the number of teeth Nr (= 12), and the necessary maximum torque timing due to the pulsation of the pump and the minimum torque output timing due to the pulsation of the motor, The relative angle θ between the motor rotor 33 and the pump rotor 22 was set so as not to coincide.
Therefore, an efficient electric pump can be provided.
(2) The relative angle θ was set so that the required maximum torque timing due to pump pulsation and the maximum torque output timing due to motor pulsation coincided. Therefore, the peak positions of the pulsation torque can be matched, and the motor output torque can be efficiently used as the pump drive torque, so that high efficiency can be obtained.
(3) The least common multiple of the number of magnetic poles Nm and the number of slots Ns and the number of teeth were set to coincide. Therefore, the torque required for the pump can be matched with the torque output from the motor, and the pump can be driven with higher efficiency.

2 Center housing 2a Pump housing portion 2b Motor housing portion 3 Stator 4 Motor cover 5 Bolt 11 Discharge port 12 Outlet port 21 Outer rotor 22 Pump rotor 22a, 33a Connection hole 33 Motor rotor 33a Connection hole 34 Stator core 35 Coil
103 Discharge oil passage
331,332 Permanent magnet fm Motor pulsation frequency fr Pump pulsation frequency N Number of rotations Nm Number of magnetic poles Nr Number of external teeth Nr Number of teeth Ns Number of slots θ Relative angle

Claims (3)

A permanent magnet motor having a motor rotor having a plurality of magnetic poles and a stator having a plurality of slots;
A drive shaft connected to the motor rotor;
A pump having a pump rotor having a plurality of teeth connected to the drive shaft, and converting the transmitted torque into fluid discharge work;
With
The number of magnetic poles, the number of slots and the number of teeth are set so that the least common multiple of the number of magnetic poles and the number of slots is an integral multiple of the number of teeth, and the necessary maximum torque timing due to pump pulsation, and a motor An electric pump characterized in that a relative angle between the motor rotor and the pump rotor is set so that the minimum torque output timing due to the pulsation of the motor does not coincide. The electric pump according to claim 1,
An electric pump characterized in that the relative angle is set so that a required maximum torque timing due to pump pulsation coincides with a maximum torque output timing due to motor pulsation. The electric pump according to claim 1 or 2,
An electric pump characterized in that the least common multiple and the number of teeth are set to coincide with each other.

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