JP2003261044A - Scissors gear and electric power steering device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a scissor gear which has a relatively simple configuration and realizes effective suppression of gear tapping sound and an electric power steering device using the scissor gear. An idler gear (38) includes a first helical gear (71), a second helical gear (73), and both helical gears (7).
1 and 73, and a compression coil spring 75 interposed between them. On the inner end surface of the first helical gear 71, a connecting shaft 83 having a male spline 81 engraved on the outer peripheral surface.
On the other hand, a connection hole 87 having a female spline 85 formed in the inner peripheral surface is formed in the axis of the second helical gear 73 so that the male spline 81 and the female spline 85 are engaged with each other. Thus, the first helical gear 71 and the second helical gear 73 are slidably connected in the axial direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scissors gear and an electric power steering device, and more particularly to a technique for realizing effective suppression of gear hammering sound while adopting a relatively simple structure.

[0002]

2. Description of the Related Art In a steering system of an automobile, a so-called power steering device is widely used, which assists steering by using an external power source. Conventionally, a vane type hydraulic pump has been used as a power source for a power steering device, and many of these hydraulic pumps are driven by an engine. However, this type of power steering device has a large engine drive loss due to the constant drive of the hydraulic pump (several horsepower to 10 horsepower at maximum load), so it is recommended to be used in light vehicles such as small displacement vehicles. It was difficult and it was unavoidable that the running fuel consumption could not be neglected even in a car with a relatively large displacement.

To solve these problems, an electric power steering device using an electric motor as a power source (Electric Power Steering, hereinafter referred to as EPS)
Has been attracting attention in recent years. Since the EPS uses an on-vehicle battery as a power source of the electric motor, there is no direct engine drive loss, and since the electric motor is started only during steering assist, reduction in running fuel consumption is suppressed and electronic control is performed. It has features such as extremely easy operation.

On the other hand, as a steering gear for passenger cars, a rack and pinion type is now predominant because of its high rigidity and light weight. As the EPS for rack and pinion type steering gear, in addition to the column assist type in which an electric motor is arranged on the column side part to drive the steering shaft and the pinion itself, the rack shaft is driven by an electric ball screw mechanism. A ball screw type rack assist type is also used. In the ball screw type rack assist type EPS (hereinafter, simply referred to as a rack assist type EPS), the assist force does not act on the meshing surface between the pinion and the rack, so that the contact surface pressure between both members that causes wear and deformation. Becomes relatively small.

In the rack assist type EPS, the male screw groove of the ball screw shaft formed on the rack shaft and the female screw groove formed on the ball nut are engaged with each other through a plurality of circulating balls (steel balls). The rack shaft moves in the axial direction by rotationally driving the ball nut with an electric motor. As a method of transmitting power between the electric motor and the ball nut, there is a timing belt type disclosed in Japanese Utility Model Publication No. 6-49489, etc., but Japanese Patent No. 306285.
No. 2 and Japanese Utility Model Publication No. 5-14939 (first prior art),
The gear type described in Japanese Utility Model Publication No. 2-46455 (second prior art) is generally used. In a rack assist type EPS that employs a gear type power transmission method, an idler gear is usually interposed between the gears on the electric motor side and the ball nut side in order to avoid large diameters. It

[0006]

In the rack assist type EPS described above, a helical gear or a spur gear is used as a gear of the power transmission gear train. As is well known, in order to operate these gears smoothly, it is necessary to provide a proper backlash between the meshing gears. However, in the case of EPS, the rotation direction of the gear changes with the reversal of steering, so when the driver gives a slight steering angle in the forward and reverse directions during straight traveling, a rattle sound (gearing sound of the gear) is generated. There was a problem that occurs. This is because the gear repeats forward and reverse rotations at relatively short intervals, and the tooth flank of the gear that has moved by the amount of backlash collides with the tooth flank of the mating gear.

Conventionally, a scissors gear of the type described in Japanese Patent Application Laid-Open No. 2-116495 exists as a technique for suppressing the hitting sound of a spur gear. This scissors gear divides the spur gear into two parts in the axial direction and urges the spar gear divided in two by a tension coil spring or a compression coil spring in the direction of relative rotation. It has a structure that clamps and holds it and prevents collision due to loose movement. However, this type of scissors gear requires about two to four tension coil springs or compression coil springs, and the space for installing the tension coil springs or compression coil springs (or storage space) or locking pins on both spur gears. However, it is inevitable that the number of components and the number of assembling steps will increase, and the structure and gear shape will become complicated. The present invention has been made in view of the above circumstances, and provides a scissors gear that achieves effective suppression of gear hammering sound and the like, and an electric power steering device that uses the scissors gear, while adopting a relatively simple configuration. To aim.

[0008]

In order to solve the above-mentioned problems, according to the invention of claim 1, a part of the gear train is formed, and the teeth of the gears that are meshed with each other are sandwiched and held in order to suppress the gear striking sound. A scissors gear, the teeth of which are not parallel to the shaft and the outer shape of which is cylindrical and engages the first gear slidably in the axial direction, and the teeth of which are parallel to the shaft. However, it is proposed to provide a second gear having a cylindrical outer shape and an urging means for axially separating or approaching the first gear and the second gear.

The invention of claim 2 proposes the scissors gear of claim 1 in which the first gear and the second gear are helical gears.

According to the first and second aspects of the present invention, the teeth of the gear meshing with the scissors gear are pinched and held by the first gear and the second gear being separated or approaching each other in the axial direction. The occurrence of gear rattling noise is prevented.

According to the invention of claim 3, there is provided a scissors gear which constitutes a part of a gear train and clamps and holds the teeth of meshed gears in order to suppress the gear striking sound. A first gear parallel to the cylinder and having a cylindrical outer shape;
Second gear, which is slidably engaged with the gear in the axial direction with a predetermined relative swivel motion, and whose teeth are parallel to the shaft and has a cylindrical outer shape, the first gear and the first gear. It is proposed to provide an urging means for separating or approaching the second gear in the axial direction.

The invention of claim 4 proposes the scissors gear of claim 3 in which the first gear and the second gear are spur gears.

According to the third and fourth aspects of the present invention, the teeth of the gear meshing with the scissors gear are clamped by the first gear and the second gear being separated or approaching in the axial direction along with the relative turning motion. This is held, and the generation of gear hammering sound due to loose movement is prevented.

In the invention of claim 5, claims 1 to 4 are provided.
In the scissors gear of (1), it is proposed that the biasing means is a coil spring.

According to the present invention, for example, by disposing the coil spring on the shaft center between the first gear and the second gear, both gears are axially separated or separated by one coil spring. approach.

According to a sixth aspect of the present invention, there is provided an electric power steering apparatus for performing steering assist by transmitting the driving force of an electric motor to a steering driving element via a gear train including a scissors gear, The scissors gear engages with the first gear, the teeth of which are not parallel to the axis and the outer shape is cylindrical, slidably in the axial direction of the first gear, and the teeth of the teeth are not parallel to the axis; It is proposed to provide a second gear having a cylindrical outer shape, and a biasing unit that axially separates or approaches the first gear and the second gear.

Further, the invention of claim 7 proposes the electric power steering device of claim 6 in which the first gear and the second gear are helical gears.

According to the sixth and seventh aspects of the present invention, the teeth of the gear meshing with the scissors gear are pinched and held by the first gear and the second gear moving away from or approaching each other in the axial direction. The occurrence of gear rattling noise is prevented.

Further, according to the invention of claim 8, there is provided an electric power steering apparatus for performing steering assist by transmitting a driving force of an electric motor to a steering driving element through a gear train including a scissors gear, wherein: The scissors gear slidably engages with a first gear whose tooth line is parallel to the shaft and has a cylindrical outer shape, and slidably engages the first gear in the axial direction with a predetermined relative swivel motion. It is proposed to provide a second gear whose streaks are parallel to the axis and whose outer shape is cylindrical, and an urging means that separates or approaches the first gear and the second gear in the axial direction.

Further, the invention of claim 9 proposes the electric power steering apparatus of claim 8 in which the first gear and the second gear are spur gears.

According to the eighth and ninth aspects of the invention, the teeth of the gear meshing with the scissors gear are clamped by the first gear and the second gear moving away or approaching each other in the axial direction with relative swiveling motion. This is held, and the generation of gear hammering sound due to loose movement is prevented.

Further, in the invention of claim 10, claims 6 to 6 are provided.
In the electric power steering device of No. 9, it is proposed that the biasing means is a coil spring.

According to the present invention, for example, by disposing the coil spring on the shaft center between the first gear and the second gear, both gears are axially separated or separated by one coil spring. approach.

[0024]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing a schematic configuration of an electric power steering device (EPS) according to the first embodiment. A member indicated by reference numeral 1 in the figure is a steering column, and rotatably supports the upper steering shaft 3. A steering wheel 5 is attached to an upper end of the upper steering shaft 3, and a lower steering shaft 9 is connected to a lower end of the upper steering shaft 3 via a universal joint 7. The lower steering shaft 9 further includes a steering gear 1 at the lower end thereof, which includes a rack and pinion mechanism, a power assist mechanism, and the like.
1 is connected. In FIG. 1, reference numeral 15 indicates a tie rod connected to the left and right ends of the steering gear 11.

FIG. 2 is a cross-sectional plan view of an essential part of the steering gear 11 according to the first embodiment, and FIG. 3 is a sectional view taken along the line AA in FIG.
It is an expanded sectional view. A member denoted by reference numeral 21 in these drawings is a rack and pinion housing that constitutes a steering gear case, and holds a rack shaft 23 and a pinion (not shown) that constitute a rack and pinion mechanism. The rack shaft 23 has a rack 25 that meshes with a pinion on the left side in the drawing, and a spherical joint 27 that swingably supports the tie rods 15 is fixed to the left and right ends thereof.

The power assist mechanism includes a gear housing 31 which is a second housing formed at the right end of the rack and pinion housing 21 in the figure, and a gear housing 31 which is bolted to the rack and pinion housing 21 to form a steering gear case. The ball screw housing 33, which is the first housing, is used as an outer shell. An electric motor 35 is bolted to the rear of the gear housing 31. Note that in FIG. 2, the electric motor 35 is drawn downward for convenience of description.

Between the gear housing 31 and the ball screw housing 33, a drive gear 37 fixed to a motor shaft (not shown) of the electric motor 35 and a drive gear 37 via an idler gear 38 which is a scissors gear.
A driven gear 39 that meshes with is stored. In the case of this embodiment, each gear 37, 38, 39 is a helical gear.

A ball nut 41 having a driven gear 39 formed at its end is rotatably held in the ball screw housing 33. The ball nut 41 includes a ball nut main body 43 and a double-row angular ball bearing 45 fitted on the ball nut main body 43.

A male screw groove 61 is formed on the rack shaft 23, while a female screw groove 63 is formed on the ball nut body 43.
Is formed, and a large number of steel balls 65, which are circulating balls, are interposed between the male screw groove 61 and the female screw groove 63. Further, the ball nut body 43 is equipped with a circulating top (not shown) for circulating the steel balls 65.

FIG. 4 shows an idler gear 38 which is a scissors gear.
FIG. 3 is a cross-sectional plan view of a main part of FIG. As shown in the figure, the idler gear 38 is composed of a first helical gear 71, a second helical gear 73, and a compression coil spring 75 interposed between the helical gears 71 and 73. In FIG.
Reference numerals 77 and 79 denote rolling bearings (deep groove ball bearings) that rotatably support the first helical gear 71 and the second helical gear 73.

On the inner end surface of the first helical gear 71, a connecting shaft 83 having a male spline 81 engraved on the outer peripheral surface is projected, and on the other hand, a female spline 85 is formed on the inner peripheral surface of the axial center of the second helical gear 73. The formed connecting hole 87 is bored, and the male spline 81 and the female spline 85 are engaged with each other so that the first helical gear 71 and the second helical gear 73 are axially slidably coupled.

Annular recesses 89 and 90 are formed on the inner end surfaces of the first helical gear 71 and the second helical gear 73, respectively, and the above-mentioned compression coil springs 75 are fitted and housed in these annular recesses 89 and 90. .. In the case of the present embodiment, the first helical gear 71 and the second helical gear 73 are formed so that the tooth traces match when the helical gears 71, 73 approach a predetermined amount from the state of FIG. Further, at the time of assembly, the idler gear 38 is engaged with the drive gear 37 and the driven gear 39 in a state where the first helical gear 71 and the second helical gear 73 are brought close to each other against the spring force of the compression coil spring 75.

The operation of the first embodiment will be described below. When the driver steers the steering wheel 5 to the left or right, a torque sensor (not shown) detects a steering torque, so that the electric motor 35 is activated by receiving a drive current from an EPS ECU (not shown). It As a result, the drive gear 37 fixed to the motor shaft of the electric motor 35 rotates, and the rotational force thereof is driven by the driven gear 39 via the idler gear 38 as shown by the arrow in FIG.
Be transmitted to.

Normally, there is a backlash between the teeth of the drive gear 37 and the teeth of the idler gear 38, but since the idler gear 38 is a scissors gear in this embodiment, the rattle noise ( Generation of gear hitting sound is suppressed. That is, backlash b is generated between the drive gear 37 and the first helical gear 71.
6 is present, the first helical gear 71 and the second helical gear 73 are axially separated from each other by the compression coil spring 75 as shown in FIG. 5, and as shown in FIG. , 73 teeth press and hold the teeth of the drive gear 37.

As a result, in this embodiment, the drive gear 37 is prevented from idling with respect to the idler gear 38 at the time of steering reversal, etc., and the quietness during EPS operation is greatly improved. Although the above description relates to the drive gear 37 and the idler gear 38, if the amount of backlash is the same, the idler gear 38 and the driven gear 39 are the same.
Similar effects can be obtained for and.

FIG. 7 shows an idler gear 3 according to the second embodiment.
8 is a cross-sectional plan view of relevant parts of FIG. As shown in the figure, the idler gear 38 is composed of a first spur gear 91, a second spur gear 93, and a compression coil spring 75 interposed between both spur gears 91, 93. In FIG. 3, reference numerals 77 and 79 denote rolling bearings (deep groove ball bearings), which rotatably support the first spur gear 91 and the second spur gear 93.

On the inner end surface of the first spur gear 91, a connecting shaft 9 in which a male twist spline 95 is engraved on the outer peripheral surface.
7 is projectingly provided, the female spline 99 is formed on the inner peripheral surface of the connecting hole 10 of the second spur gear 93.
1 is bored, and the male twist spline 95 and the female twist spline 99 are engaged with each other, whereby the first spur gear 9
The first spur gear 93 and the second spur gear 93 are slidably connected in the axial direction with a predetermined relative turning motion.

First spur gear 91 and second spur gear 93
Annular recesses 89 and 90 are respectively formed on the inner end surfaces of the, and the compression coil springs 75 described above are fitted and housed in the annular recesses 89 and 90. In the case of the present embodiment, the first spur gear 91 and the second spur gear 93 are formed so that the tooth traces match when both spur gears 91, 93 approach a predetermined amount from the state of FIG. 7.

The operation of the second embodiment will be described below. When the backlash b ′ exists between the drive gear 37 and the first spur gear 91, as shown in FIG. 8, the compression coil spring 75 biases the first spur gear 91 and the second spur gear 91.
The spur gear 93 and the spur gear 93 rotate away from each other in the axial direction, and
As shown in FIG. 5, the teeth of both spur gears 91 and 93 hold and hold the teeth of the drive gear 37.

As a result, in the second embodiment as well, as in the first embodiment, the drive gear 37 is used when the steering is reversed.
Will no longer idle with respect to the idler gear 38,
Quietness during EPS operation has been greatly improved. Although the above description relates to the drive gear 37 and the idler gear 38, similar effects can be obtained for the idler gear 38 and the driven gear 39 as long as the amount of backlash is the same.

The description of the specific embodiment is completed above.
Aspects of the present invention are not limited to the above embodiment.
For example, the above-described embodiment is an application of the present invention to an idler gear of a driving force transmission gear train of EPS, but is also applicable to a scissors gear used for a valve train of an internal combustion engine or a power transmission system of industrial machinery. Good. Further, in the above embodiment,
Although the helical gear pair or the spur gear pair is separated from each other by one compression coil spring, the helical gear pair or the spur gear pair may be arranged closer to each other, or a tension coil spring, a disc spring, a leaf spring or the like may be used as the biasing means. Alternatively, the number and the number of them, and the installation form can be appropriately selected. Also, the first
In the embodiment, a spiral gear may be used instead of the helical gear. In addition, the overall configuration of the steering gear, the structure of the power assist mechanism, and the like can be appropriately changed according to design or specification requirements, as long as they do not depart from the scope of the invention.

[0042]

As described above, according to the scissors gear of the first aspect of the invention and the electric power steering device of the sixth aspect, the teeth are not parallel to the shaft and the outer shape is cylindrical. A gear, a second gear engaged with the first gear slidably in the axial direction, the tooth line of which is not parallel to the shaft and the outer shape of which is cylindrical; the first gear and the second gear; Since the first gear and the second gear are separated from each other or approached in the axial direction, the teeth of the gear meshing with the scissors gear are pinched by the biasing means for separating or approaching the gear in the axial direction. -Because it is held, the occurrence of gear rattling noise due to free movement is effectively prevented while adopting a simple configuration with a relatively small number of parts.

According to the scissors gear of the third aspect of the invention and the electric power steering apparatus of the eighth aspect, the first gear whose teeth are parallel to the axis and the outer shape is cylindrical, and the first gear. A second gear, which is slidably engaged with the gear in the axial direction with a predetermined relative swivel motion, whose teeth are parallel to the shaft, and has a cylindrical outer shape, the first gear, and the second gear. Since the first gear and the second gear are separated or approached in the axial direction along with the relative turning motion, the scissors gear is provided. The teeth of the gears that are meshed with each other are clamped and held, and the occurrence of gear rattle due to loose movement is effectively prevented while adopting a simple configuration with a relatively small number of parts.

[Brief description of drawings]

FIG. 1 is a perspective view showing a schematic configuration of a steering device according to the present invention.

FIG. 2 is a cross-sectional plan view of relevant parts of the steering gear according to the first embodiment.

3 is an enlarged cross-sectional view taken along the line AA in FIG.

FIG. 4 is a cross-sectional plan view of a main part of the idler gear according to the first embodiment.

FIG. 5 is an explanatory diagram showing an operation of the first embodiment.

FIG. 6 is an explanatory diagram showing the operation of the first embodiment.

FIG. 7 is a cross-sectional plan view of a main part of an idler gear according to a second embodiment.

FIG. 8 is an explanatory diagram showing the operation of the second embodiment.

FIG. 9 is an explanatory diagram showing the operation of the second embodiment.

[Explanation of symbols]

11 ... Steering gear 35 Electric motor 37 ... Drive gear 38 .. idler gear (scissors gear) 39: Driven gear 71 ... 1st helical gear 73 ... Second helical gear 75 ... Compression coil spring 81 Male Spline 83 ... Connection shaft 85 .. Female spline 87 ... Connection hole 91 ... 1st spur gear 93 ... Second spur gear 95 ... Male Twist Spline 97 ... Connection shaft 99 .. Female twist spline 101 ... Connection hole

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toshihiro Fukuda             Gunma Prefecture Maebashi City 1-8-1 Sojamachi Japan             Within Seiko Co., Ltd. (72) Inventor Osamu Saito             Gunma Prefecture Maebashi City 1-8-1 Sojamachi Japan             Within Seiko Co., Ltd. (72) Inventor Jun Okada             Gunma Prefecture Maebashi City 1-8-1 Sojamachi Japan             Within Seiko Co., Ltd. F-term (reference) 3D033 CA04                 3J030 AB05 BA01 BA05 BB03 BB07                       BB11 CA10

Claims (10)

[Claims] Claims: 1. A scissors gear which constitutes a part of a gear train and clamps and holds the teeth of meshed gears in order to suppress gear hammering sound, the tooth traces of which are not parallel to the shaft and whose outer shape is A cylindrical first gear, a second gear engaged with the first gear so as to be slidable in the axial direction, the tooth line of which is not parallel to the axis and the outer shape of which is cylindrical; A scissors gear, comprising: a gear and an urging means that separates or approaches the second gear in the axial direction. 2. The scissors gear according to claim 1, wherein the first gear and the second gear are helical gears. 3. A scissors gear which constitutes a part of a gear train and clamps and holds the teeth of meshed gears in order to suppress gear hammering noise, the tooth traces of which are parallel to the shaft and whose outer shape is cylindrical. -Shaped first gear and a second gear which is slidably engaged with the first gear in the axial direction with a predetermined relative swivel motion, and whose teeth are parallel to the shaft and whose outer shape is cylindrical. A scissors gear, comprising: a gear; and an urging unit that axially separates or approaches the first gear and the second gear. 4. The scissors gear according to claim 3, wherein the first gear and the second gear are spur gears. 5. The scissors gear according to claim 1, wherein the urging means is a coil spring. 6. An electric power steering apparatus for assisting steering by transmitting a driving force of an electric motor to a steering driving element through a gear train including a scissors gear, wherein the scissors gear has tooth traces thereof. A first gear which is not parallel to the shaft and has a cylindrical outer shape, and a second gear which is engaged with the first gear so as to be slidable in the axial direction and whose teeth are not parallel to the shaft and has a cylindrical outer shape. And an urging unit that axially separates or approaches the first gear and the second gear from each other. 7. The electric power steering apparatus according to claim 6, wherein the first gear and the second gear are helical gears. 8. An electric power steering device for assisting steering by transmitting a driving force of an electric motor to a steering driving element via a gear train including a scissors gear, wherein the scissors gear has tooth traces thereof. A first gear, which is parallel to the shaft and has a cylindrical outer shape, is slidably engaged with the first gear along with a predetermined relative swivel motion in the axial direction, and its teeth are parallel to the shaft. An electric power steering apparatus comprising: a second gear having a cylindrical outer shape; and an urging unit that axially separates or approaches the first gear and the second gear. 9. The electric power steering apparatus according to claim 8, wherein the first gear and the second gear are spur gears. 10. The electric power steering apparatus according to claim 6, wherein the urging means is a coil spring.