JP2007320416A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device capable of preventing noises of a reduction gear mechanism or bad smell of a lubricant from being directly transmitted to a driver. <P>SOLUTION: The electric power steering device 1 is provided with the reduction gear mechanism 7 for amplifying the output of an electric motor 6. A gear housing 8 for housing the reduction gear mechanism 7 and the reduction gear mechanism 7 is arranged in the vehicle compartment S3. One end of a breather tube 28 is connected to a tubular protrusion demarcating an atmospheric release hole for communicating the inside and the outside of the gear housing 8. The other end of the breather tube 28 penetrates a dashboard 12 and reaches an engine room S2 leading to the atmosphere. A filter permitting only the flow of air is attached in the other end. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to an electric power steering device that generates a steering assist force by an electric motor.

Some electric power steering systems (EPS) for vehicles include a reduction mechanism. The output of the electric motor is amplified by this speed reduction mechanism and transmitted to the steering mechanism. The speed reduction mechanism is accommodated in the housing.
Patent Document 1 below discloses an electric power steering apparatus in which an air opening hole for communicating the inside and the outside of the housing is provided in the housing.
Japanese Patent Laid-Open No. 11-11336

  However, in the electric power steering device described in Patent Document 1, noise due to the operation of the speed reduction mechanism and the odor of the lubricant for lubricating the speed reduction mechanism may leak to the outside of the housing through the air opening hole. Therefore, in the electric power steering apparatus in which the speed reduction mechanism is arranged in the vehicle interior such as a so-called column assist type, there is a possibility that these noises and odors are directly transmitted to the driver.

  The present invention has been made based on such a background, and an object thereof is to provide an electric power steering device capable of preventing the noise of the speed reduction mechanism and the odor of the lubricant from being directly transmitted to the driver.

To achieve the above object, the present invention includes a gear housing (8) that houses a reduction mechanism (7) that decelerates the output rotation of an electric motor (6) and is disposed in a vehicle compartment (S3), and a gear housing. It is an electric power steering device (1) provided with a breather tube (28) for communicating the provided air opening hole (27) outside the vehicle compartment.
According to the present invention, it is possible to increase the surface area where the radiated sound radiated from the air opening hole collides with the breather tube, thereby increasing the absorption of the vibration energy of the sound caused by the collision with the inner surface of the breather tube. Noise can be reduced. Further, by communicating the inside of the gear housing with the outside of the passenger compartment, the odor of the lubricant can be released to the outside of the passenger compartment, so that these noises and odors can be prevented from being directly transmitted to the driver.

Further, in order to communicate the air opening hole to the outside of the passenger compartment by the breather tube, one end (30) of the breather tube passes through the dashboard (12) partitioning the inside and outside of the passenger compartment and reaches the engine room (S2). The other end (29) of the breather tube may be communicated with the atmosphere opening hole.
In this case, a filter (32) that allows only air flow may be provided at the one end of the breather tube. Thus, the lubricant in the gear housing can be prevented from flowing out of the passenger compartment through the breather tube, and foreign substances such as rainwater and dust can be prevented from entering the breather tube and the gear housing.

In the present invention, the air opening hole may be defined by a cylindrical protrusion (26) protruding from the gear housing, and the other end of the breather tube may be connected to the cylindrical protrusion. In this case, by connecting the other end of the breather tube to the cylindrical protrusion, the breather tube and the air release hole can be easily communicated with each other.
In the above description, the alphanumeric characters in parentheses represent reference numerals of corresponding components in the embodiments described later, but the scope of the claims is not limited by these reference numerals.

Embodiments of the present invention will be specifically described below with reference to the drawings.
FIG. 1 is a partial cross-sectional view schematically showing an automobile C1 provided with an electric power steering apparatus 1 according to an embodiment of the present invention. FIG. 2 is provided in the electric power steering apparatus 1 of FIG. It is the expanded sectional view which shows typically the deceleration mechanism 7 and its vicinity. FIG. 3 is an enlarged cross-sectional view of the automobile C1 including the speed reduction mechanism 7 and the vicinity thereof.

Referring to FIG. 1, an electric power steering apparatus 1 includes a steering member 2 such as a steering wheel, a steering shaft 3 to which the steering member 2 is connected to one end, and the other end of the steering shaft 3 via an intermediate shaft 4. And a steering mechanism 5 such as a rack and pinion mechanism connected thereto.
The steering shaft 3 is rotatably supported by a steering column 34 supported by the vehicle body. Further, the steering shaft 3 is disposed in an inclined state with respect to the vertical direction, and extends downward from the rear of the automobile C1 toward the front (from the right side to the left side in FIG. 1). Around the steering shaft 3, an electric motor 6 for assisting steering and a speed reduction mechanism 7 for amplifying the output of the electric motor 6 and transmitting it to the steering shaft 3 are arranged. The speed reduction mechanism 7 is accommodated in a cylindrical gear housing 8.

A steered wheel 10 is connected to each end of the steering mechanism 5 in the left-right direction of the automobile C1 (direction perpendicular to the paper surface of FIG. 1) via a knuckle arm 9.
On the other hand, the automobile C1 includes a vehicle interior space S1 partitioned by a body 11, and this vehicle interior space S1 is partitioned into an engine room S2 and a vehicle interior S3 by a dashboard 12. The engine room S2 is disposed at the front of the automobile C1 and houses an engine and the like. The passenger compartment S3 is a space where a driver or the like gets in, and an instrument panel 35 is provided in the passenger compartment S3 so as to face the dashboard 12.

In this embodiment, the steering member 2, the steering shaft 3, the electric motor 6, the speed reduction mechanism 7, and the gear housing 8 are disposed in the vehicle interior S3. The intermediate shaft 4 passes through the dashboard 12 and reaches the engine room S2, and is connected to the steering mechanism 5 in the engine room S2.
Next, the speed reduction mechanism 7 and its vicinity will be described in detail.

  Referring to FIG. 2, the steering shaft 3 is divided into an input shaft 13 as an upper shaft connected to the steering member 2 and an output shaft 14 as a lower shaft connected to the intermediate shaft 4. The input shaft 13 and the output shaft 14 are each formed in a cylindrical shape, and a part of the input shaft 13 is fitted inside the output shaft 14. Further, a torsion bar 15 is inserted into the input shaft 13 and the output shaft 14, and each end portion of the torsion bar 15 is connected to the input shaft 13 and the output shaft 14 via pins 33, respectively. . Thereby, the input shaft 13 and the output shaft 14 are connected so that relative rotation is possible on the same axis.

A torque sensor 16 for detecting a steering torque input from the driver to the steering member 2 is provided around the fitting portion of the input shaft 13 and the output shaft 14. The torque sensor 16 detects the steering torque based on the relative rotation amount of the input shaft 13 and the output shaft 14.
The speed reduction mechanism 7 includes a worm shaft 17 as a drive gear that is rotationally driven by the electric motor 6 and a worm wheel 18 as a driven gear that meshes with the worm shaft 17.

Although not shown, the worm shaft 17 is connected to the rotating shaft of the electric motor 6 via a joint, and a worm is formed at an intermediate portion in the axial direction of the worm shaft 17.
The worm wheel 18 includes an annular metal core 19 connected to the output shaft 14 so as to be integrally rotatable, and a synthetic resin member 20 that surrounds the metal core 19 and has teeth that mesh with the worm. The metal core 19 is fixed to the output shaft 14 by press-fitting, for example. Further, the core metal 19 is inserted into a mold when the synthetic resin member 20 is molded, for example, and is integrally coupled to the synthetic resin member 20. Thereby, the worm wheel 18 is connected to the output shaft 14 so as to be integrally rotatable and immovable in the axial direction.

  In the gear housing 8, at least the meshing portion of the worm shaft 17 and the worm wheel 18 is filled with a lubricant. As the lubricant, for example, a lubricant containing buffer particles as shown in JP-A-2003-214529 can be mentioned. By using this lubricant, the collision between the tooth surfaces of the worm shaft 17 and the worm wheel 18 can be buffered. Thereby, the rattling sound resulting from backlash can be reduced.

  The lubricant may be a lubricating oil as a liquid lubricant or a grease as a semi-solid lubricant, but the lubricant has an average particle size of 0.1 to 0.1 as buffer particles. 50 μm fine powder of elastic material (round block shape or stick shape) may be included. Since the minute buffer material particles are interposed in the meshing portion between the worm shaft 17 and the worm wheel 18, the rattling noise can be significantly reduced.

As the lubricating oil used for the lubricant, for example, a lubricating oil having a kinematic viscosity in the range of 10 to 500 mm ² / s (40 ° C.) can be used, and a synthetic hydrocarbon oil (for example, poly α-olefin oil) is preferably used. However, mineral oil, silicone oil, fluorine-based synthetic oil and the like can be used. Add solid lubricants (molybdenum disulfide, graphite, PTFE), extreme pressure additives such as phosphorus and sulfur compounds, antioxidants such as tributylphenol and trimethylphenol as additives. Also good.

  As the grease used for the lubricant, for example, grease having a consistency of NGL 1 number 000 to 2 is preferably used. As the base oil in the grease, a synthetic hydrocarbon oil (for example, a poly α-olefin oil) is preferably used, but in addition, mineral oil, silicone oil, fluorine-based synthetic oil, and the like can be used. Further, as the thickener, various conventionally known thickeners (soap and non-soap) can be used, solid lubricants (molybdenum disulfide, graphite, PTFE), phosphorus compounds and sulfur compounds, and the like. These extreme pressure additives, antioxidants such as tributylphenol and trimethylphenol may be added as additives.

In particular, it is very preferable because the noise can be reduced at low cost without changing the design of each member only by adding the buffer particles to the lubricant.
Furthermore, it is considered that the buffer material particles compressed at the meshing portion adhere to the surface of the gear teeth to form a thin film with the lapse of the use time of the speed reduction mechanism 7, and thus a high noise reduction effect over a long period of time. Can be maintained.

The average particle size of the buffer material particles is set in the range of 0.1 to 50 μm because the noise reduction effect is small if the average particle size of the buffer material particles is less than 0.1 μm, and the average particle size of the buffer material particles If the thickness exceeds 50 μm, the backlash may be clogged too much and the rotational resistance may increase.
Moreover, it is preferable if the filling ratio of the buffer material particles in the lubricant is 0.1 to 30% by weight. This is because when the amount is less than 0.1% by weight, the noise reduction effect can hardly be expected. When the amount exceeds 30% by weight, the base oil is mixed with the buffer material particles, and the lubricant is uniformly mixed. This may be difficult.

  In particular, the filling ratio of the buffer material particles in the lubricant is preferably 3 to 10% by weight. For example, if it is 3% by weight or more, a noise reduction effect of, for example, 3 dB or more can be expected, but even if the filling ratio of the buffer particles exceeds 10% by weight, the noise level is further lowered. This is because it cannot be expected. In view of cost performance, 3 to 5% by weight is most preferable.

  A synthetic resin having an average molecular weight of 1000 to 20000 can be used as the buffer material particles. If the average molecular weight is less than 1000, the buffer particles become too soft, and if the average molecular weight exceeds 20000, the buffer particles become too hard. In any case, the noise prevention effect may be lowered. The above range is set. Examples of the synthetic resin include polyolefin resins, polyamide resins, polyester resins, polyacetal resins, polyphenylene sulfide resins, polyimide resins, fluororesins, and the like, and mixtures of the above resins (including eutectoids).

Synthetic rubber can be used as the buffer material particles. Examples of the synthetic rubber include ethylene / propylene rubber such as EPM (ethylene propylene diene copolymer) and EPDM (ethylene propylene diene terpolymer).
Moreover, when the said buffer material particle | grains have self-lubricating property, it is preferable at the point which can aim at reduction of sliding resistance and wear amount. Examples of the self-lubricating buffer material particles include polyolefin resins, polyamide resins, synthetic resins such as mixtures (including eutectoids) obtained by adding fluororesins thereto, and synthetic rubbers added with fluororesins. be able to.

In this embodiment, grease using ester oil as the base oil is used as the lubricant.
Referring to FIGS. 1 and 2, a sensor housing 22 that accommodates the torque sensor 16 is connected to the lower portion of the steering column 34, and a gear housing 8 is connected to the lower portion of the sensor housing 22. . As shown in FIG. 2, the end of the sensor housing 22 is fitted into the end of the gear housing 8. A gap between the end of the gear housing 8 and the end of the sensor housing 22 is sealed by a seal member 23 such as an O-ring accommodated in an annular groove formed at the end of the sensor housing 22.

  The steering shaft 3 is inserted into the cylindrical gear housing 8 and the sensor housing 22 and is rotatably supported by the gear housing 8 and the sensor housing 22 via a plurality of bearings. Specifically, the output shaft 14 is rotatably held by the gear housing 8 and the sensor housing 22 via a pair of bearings 24 and 25 disposed on both sides of the worm wheel 18 with respect to the axial direction of the steering shaft 3. ing.

  An example of the pair of bearings 24 and 25 is a rolling ball bearing. In this embodiment, a double-seal ball bearing is used. One bearing 24 is disposed at the lower end of the gear housing 8 in the axial direction of the steering shaft 3. The inner ring of one bearing 24 is fixed to the output shaft 14 by press-fitting, for example. Moreover, the outer ring | wheel of one bearing 24 is being fixed to the gear housing 8 by press injection, for example. That is, the lower end portion of the gear housing 8 and the output shaft 14 are sealed by one bearing 24.

  The other bearing 25 is disposed at the lower end of the sensor housing 22 with respect to the axial direction of the steering shaft 3. The inner ring of the other bearing 25 is fixed to the output shaft 14 by press-fitting, for example. The outer ring of the other bearing 25 is fixed to the sensor housing 22 by, for example, press fitting. In other words, the lower end of the sensor housing 22 and the output shaft 14 are sealed by the other bearing 25.

  Therefore, the space S4 defined by the output shaft 14, the gear housing 8, the sensor housing 22, and the pair of bearings 24 and 25 is a sealed space except for a part (the air release hole 27 described later). The worm shaft 17 and the worm wheel 18 are disposed in the space S4. Accordingly, since the lubricant filled in the worm shaft 17 and the worm wheel 18 is also disposed in the space S4, the lubricant can be prevented from flowing out of the gear housing 8.

The pair of bearings 24 and 25 may be single seal ball bearings. In this case, the seals of the bearings 24 and 25 are preferably arranged on the worm wheel 18 side.
Next, a configuration for communicating the inside (space S4) of the gear housing 8 that is a feature of the present embodiment with the atmosphere will be described.
With reference to FIG. 3, the gear housing 8 is formed with a cylindrical protrusion 26 that protrudes radially outward of the steering shaft 3. An air release hole 27 for communicating the space S4 in the gear housing 8 with the atmosphere is defined by the inner peripheral surface of the cylindrical protrusion 26.

The cylindrical protrusion 26 is preferably formed on the upper portion of the gear housing 8 in the vertical direction, and is formed on the upper portion of the gear housing 8 in the vertical direction and on the upper portion of the gear housing 8 in the axial direction of the steering shaft 3. More preferably. Thereby, it can suppress that the lubricant in space S4 flows out outside.
In addition, a breather tube 28 is connected to the cylindrical projection 26 to guide the air that enters and exits the space S4 through the atmosphere opening hole 27. Specifically, one end 29 of the breather tube 28 is fitted on the outer periphery of the cylindrical protrusion 26. As the breather tube 28, for example, a synthetic resin tube having an inner diameter of about 20 to 30 mm is used.

On the other hand, the other end 30 of the breather tube 28 passes through a through hole 31 formed in the dashboard 12 that partitions the vehicle compartment S3 and the engine room S2, and reaches the engine room S2. The through hole 31 formed in the dashboard 12 is disposed above the air opening hole 27 in the vertical direction.
A filter 32 that allows only air flow is attached to the opening provided at the other end 30 of the breather tube 28. Examples of the filter 32 include a porous body such as foamed resin and polyurethane, and a thin film having a large number of micropores. In this embodiment, Gore-Tex (registered trademark, Japan Gore-Tex Co., Ltd.) is used as the filter 32.

  Thus, the space S4 communicates with the engine room S2 that communicates with the atmosphere. Therefore, it is possible to prevent the air from contracting and the pressure in the space S4 from changing as the temperature in the space S4 changes. As a result, it is possible to prevent problems associated with changes in the pressure in the space S4, for example, the seals of the bearings 24 and 25 stick to rolling elements, movable wheels, etc., and the rotational resistance of the output shaft 14 increases.

  Further, by disposing the through hole 31 above the atmosphere opening hole 27, it is possible to suppress the lubricant that has flowed from the space S4 to the breather tube 28 from flowing into the engine room S2. Further, the filter 32 attached to the other end 30 of the breather tube 28 can prevent the lubricant from flowing into the engine room S2. Further, the filter 32 can prevent foreign matters such as rainwater and dust from entering the breather tube 28.

  As described above, in this embodiment, by providing the air release hole 27 in the gear housing 8, it is possible to prevent the pressure in the space S4 from changing. Further, by connecting the air release hole 27 to the engine room S2 outside the vehicle compartment S3 by the breather tube 28, the surface area on which the radiated sound radiated from the air release hole 27 collides can be increased, whereby the inner surface of the breather tube 28 is increased. The absorption of the vibration energy of the sound caused by hitting can be increased, and as a result, the noise of the speed reduction mechanism 7 can be reduced. Further, the odor of the lubricant can be released out of the passenger compartment S3. Thereby, even if it is the structure by which the speed reduction mechanism 7 is arrange | positioned in vehicle interior S3, it can prevent that the noise of the speed reduction mechanism 7 and the odor of a lubricant are transmitted directly to the driver | operator in vehicle interior S3, etc.

  The present invention is not limited to the contents of the above embodiments, and various modifications can be made within the scope of the claims.

1 is a partial cross-sectional view schematically showing an automobile provided with an electric power steering device according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view schematically showing a speed reduction mechanism provided in the electric power steering device of FIG. 1 and its vicinity. It is an expanded sectional view of a car including a deceleration mechanism and its neighborhood.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electric power steering device, 6 ... Electric motor, 7 ... Reduction mechanism, 8 ... Gear housing, 12 ... Dashboard, 26 ... Cylindrical protrusion, 27 ... Atmosphere Open hole, 28 ... breather tube, 29 ... end (other end of breather tube), 30 ... end (one end of breather tube), 32 ... filter, S2 ... engine room, S3 ... Car cabin

Claims (4)

A gear housing that houses a reduction mechanism that decelerates the output rotation of the electric motor and is disposed in the vehicle interior;
An electric power steering apparatus comprising a breather tube for communicating an air opening hole provided in a gear housing to the outside of a vehicle compartment.   2. The electric power steering apparatus according to claim 1, wherein one end of the breather tube passes through a dashboard that partitions the inside and outside of the passenger compartment and reaches the engine room.   3. The electric power steering apparatus according to claim 2, wherein a filter that allows only air flow is provided at the one end of the breather tube.   4. The electric power steering apparatus according to claim 1, wherein the air opening hole is defined by a cylindrical protrusion protruding from the gear housing, and the other end of the breather tube is connected to the cylindrical protrusion. .

Images