JP2778678B2 - Motor cooling device for electric power steering - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling device which can efficiently cool a brushless motor of an electric power steering of an automobile, for example.

[0002]

2. Description of the Related Art Conventionally, a drive motor used as a power steering device of an automobile is disposed at an intermediate portion of a steering shaft, for example, as disclosed in Japanese Patent Laid-Open No. 59-50 / 1984.
No. 864 is known. In this apparatus, a brushed motor is used as a drive motor, and cooling is performed by rotating an electromagnet rotor that is a heating element.

[0003]

However, such a motor with a brush as described above causes problems such as abrasion of a commutator and generation of mechanical noise. It is desirable to extend the life, but in this case, for example, when an electromagnet is used on the stator side, how to cool the heat generated on the stator side has been a problem.

[0004]

[Means for Solving the Problems] To solve such problems.
The present invention relates to a motor cooling device for an electric power steering for cooling a brushless motor provided at an intermediate portion of a steering shaft, wherein a pair of left and right exterior members connected to the brushless motor and exteriorly covering a steering shaft are provided. with connecting the other end of the telescopic pair of boots for connecting the exterior member to the tie rod, before
The boot, the exterior member, and the brushless motor communicate with each other through an air passage, and the brushless motor is provided in the air passage.
A power switching element for driving the motor was provided .

[0005]

[Action] internal boot and the package member and the brushless motor if ask communicated with the air passage, it is possible to cool the brushless motor by using the blowing action of the boot to stretch by the steering wheel, and a brushless motor drive power vinegar
Since the switching element also generates heat, it is provided in the air passage and cooled together.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a cooling device for a motor of an electric power steering according to the present invention will be described with reference to the accompanying drawings. 1 is a sectional view of the electric power steering device, FIGS. 2 and 3 are operation diagrams, and FIG. 4 is an operation diagram of a check valve provided in a part of an air passage.

An electric power steering apparatus for a vehicle is configured to rotate a brushless motor in accordance with a signal detected by a torque sensor, and to convert the rotation of the brushless motor into left and right movements of a steering shaft to supplement a steering wheel operating force. I have.

[0008] Such a brushless motor is
For example, when the stator side is a coil winding and the rotor side is a permanent magnet, if the heat generated on the stator side is not effectively cooled, the function will not be fully exhibited or the wear will be accelerated. It could be the cause.

[0009] Therefore, merits is constructed as an apparatus for effectively cooling a heating of such stator, also the power switching <br/> element simultaneous Meaux <br/> drive current control incorporated into the data I'm trying to cool it down.

[0010] In other words, the power switching element,
This is because, for example, a MOS-FET of a field-effect transistor or the like easily generates heat.

As shown in FIG. 1, a pinion 2a at the lower end of a handle shaft 2 meshes with a rack (a back side in the figure) formed on a part of the steering shaft 1, and the rotation of the handle is controlled by the steering shaft 1. And a ball screw groove 3 as a ball screw portion is formed in a part of the steering shaft 1.

A nut screw 5 is screwed into the ball screw groove 3 via a plurality of balls 4, and the rotation of the nut screw 5 assists the reciprocation of the steering shaft 1. That is,
The nut screw 5 is connected to the rotor 7 of the adjacent brushless motor 6, and the outer peripheral portion is supported by the first housing 10 via the bearing 8.

The brushless motor 6 includes a second housing 1
A stator 12 comprising a coil winding provided in
And a cylindrical rotor 7 rotatably inserted into the steering shaft 1. A permanent magnet 9 is attached to an outer peripheral portion of the rotor 7, and an outer member connected to the second housing 11. Third housing 1
A power circuit unit 14 is provided in 3. The power circuit unit 14 is connected to an end of a winding of the stator 12.

The power circuit unit 14 includes a plurality of power units mounted on a cylindrical base block 16.
A switching element 17 and a board 18 including a thin circuit board, a connection board, a power supply board, and the like connected to the power switching element 17 are provided, and the board 18 is connected to a battery (not shown).

The power switching element 17
Is , for example, a field effect transistor (MOS-FET) having an oxide film formed on the surface, and in the case of the embodiment, six pieces are provided along the circumferential direction.

On the left side of the brushless motor 6, a fourth housing 20 is provided as the other exterior member, and a predetermined portion is supported by a bracket 21.
The end of the fourth housing 20 is connected to a telescopic boot 22. The other end of the boot 22 is connected to the tie rod 23.

On the other hand, an end of the third housing 13 is also connected to a telescopic boot 24, and the other end of the boot 24 is connected to a tie rod 25.

The boot 22, the fourth housing 2
0, the brushless motor 6, the third housing 13, and the boot 24 communicate with each other. That is, the boot 2 on the left side of FIG.
The connecting member 28 connecting the second and fourth housings 20 includes:
For example, four air vent holes (not shown) are provided in the circumferential direction, and a clearance is provided between the stator 12 and the rotor 7 of the motor 6. Also, the third housing 1
The small diameter portion 7a of the rotor 7 extending toward the inside 3 is provided with a through hole 26 penetrating the inside and outside of the cylinder.

Further, clearances are provided between the fourth housing 20 and the steering shaft 1 and between the third housing 13 and the steering shaft 1 so as to allow the steering shaft 1 to move left and right. A clearance for rotating the rotor 7 is also provided between the steering shaft 7 and the steering shaft 1.

Therefore, as described above, the boot 22, the fourth
The air in the housing 20, the brushless motor 6, the third housing 13, and the boot 24 is applied to the clearance described above.
Therefore , a check valve 30 is provided between the first housing 10 and the nut screw 5 in the air passage.
Check valve 3 between one end of the shaft and the steering shaft 1
1 is provided.

The former check valve 30 is shown in FIG.
As shown in (1), the passage of air flowing from the brushless motor 6 is allowed, and the passage of air in the opposite direction is prevented as shown in (a). The air passage of the nut screw 5 is constituted by two passages: an outer passage on the bearing 8 side provided with the check valve 30 and an inner passage of the nut screw 5 screwed via the ball 4. Become. Further, as shown in FIG. 5, the latter check valve 31 blocks the passage of air from the right side in the figure and conversely allows the passage of air from the left side.

Next, a plurality of fin-like projections 27 are provided on the small diameter portion 7a of the rotor 7 at predetermined intervals along the outer periphery. The projections 27 are provided, for example, at six locations in the circumferential direction, so that air sucked from the through holes 26 with the rotation of the rotor 7 can be blown toward the power switching element 17. ,
In order to give directionality to the direction of flow of the blowing air, the upper surface is inclined to lower the motor 6 side. That is,
In FIG. 1, the fluid flows from the right to the left.

The operation of the cooling device of the present invention configured as described above will be described.

When a signal is sent from the torque sensor by operating the steering wheel, the electric power steering operates to assist the operating force. That is, the stator 1 of the brushless motor 6 passes through the power element 17 of the power circuit unit 14.
2, the rotor 7 rotates to assist the lateral movement of the steering shaft 1.

At this time, as shown in FIG. 2, the steering shaft 1 moves rightward in FIG.
Considering the case where 4 has contracted and the left boot 22 has expanded, the air in the boot 24 that has been compressed and has increased pressure flows in the direction of the arrow toward the negative pressure boot 22.

Since the passage between the rotor 7 and the steering shaft 1 is blocked by the check valve 31, the air passes through the gap between the third housing 13 and the steering shaft 1 and passes through the through hole of the rotor small diameter portion 7 a. 26 blown toward the power switching element 17, after cooling the power switching element 17, to cool the stator 12 and flow in the interstices between the rotor 7 and the stator 12.

The air used for the cooling passes through the bearing 8 through the check valve 30 and passes through the fourth housing 2.
The fluid flows into the gap between the steering wheel 1 and the steering shaft 1 and enters the boot 22 on the other side. The air heated during the cooling is cooled by the heat radiation during this flow. still,
A radiating fin 13a is provided outside the third housing 13 provided with the power switching element 17 so as to enhance the radiating effect by traveling wind.

Next, as shown in FIG. 3, when the steering shaft 1 is moved to the left in FIG. 3 by reversing the steering wheel operation, the left boot 22 contracts, the right boot 24 expands, and the compression occurs. The air in the boot 22 whose pressure is increased by the pressure flows toward the boot 24 on the negative pressure side in the direction indicated by the arrow.

That is, the air passing through the gap between the fourth housing 20 and the steering shaft 1 is blocked by the check valve 30 from the bearing 8 side, so that the threaded portion between the nut screw 5 and the ball screw groove 3 is formed. Through the gap,
A part enters the gap between the rotor 7 and the steering shaft 1, passes through the check valve 31, and is partly sucked from the through hole 26 and used for cooling the power switching element 17 and the stator 12, and partly depending on the situation, partly on the other side. It gets inside the boots 24.

The increased cooling effect of the stator 12 and by the circulation action of the air as described above, power Sui simultaneously
Cooling the switching element 17 may also FIG Rukoto.

[0031]

As described above , according to the present invention , the
The brushless motor provided in the middle of the
Cooling device for electric power steering motor cooling
Connected to the brushless motor and
A pair of left and right exterior members are provided to exteriorize the shaft.
Connect the other end of a pair of elastic boots to the member
As well as boots, exterior members, and brassieres.
The interior of each cylinder motor is communicated with an air passage,
Power switching for brushless motor drive in passage
Since the elements are provided, as a cooling device for the motor of the electric power steering , the boot, the exterior member, and the brushless motor can be communicated with each other through the air passage, and the stator can be cooled by using the air supply action by the expansion and contraction action of the boot. ,brush
The cooling effect of the motor for brushless drive is enhanced, and brushless drive
It can be expected that the performance of the motor will be sufficient. So
And, since it <br/> embedded I into the air passage of the power switching elements described above, device not only is compact, the heat power switching element is also generated effectively it is possible to cool.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an electric power steering device.

FIG. 2 is an operation diagram of the cooling device of the present invention, showing a state in which the cooling device is steered to one side;

FIG. 3 is an operation diagram of the cooling device, showing a state in which the cooling device is steered to the other side.

FIG. 4 is an operation diagram of a check valve.

FIG. 5 is an operation diagram of a check valve.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Steering shaft 6 Brushless motor 7 Rotor 12 Stator 13 3rd housing as an exterior member 17 Power switching element 20 4th housing as an exterior member 22 and 24 Boots 23 and 25 Tie rod

Claims (1)

(57) [Claims] 1. A cooling device for an electric power steering motor for cooling a brushless motor provided at an intermediate portion of a steering shaft , comprising a pair of left and right exterior members connected to the brushless motor and exteriorly covering a steering shaft. brushless with connecting the other end of the telescopic pair of boots for connecting the exterior member to the tie rod, and said boot, the outer member, each inner of the brushless motor is communicated with the air passage, and the air passage
A motor cooling device for an electric power steering, comprising a power switching element for driving a motor.