JP2014169745A - Transmission mechanism of gear pair with intersecting axes and wheel steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain an engaging part between a pinion and a face gear that are engaged to each other when they rotate in a direction of high transmission torque by a tooth form having a small pressure angle and decrease an engagement reaction force.SOLUTION: A tooth surface 24a (tooth surfaces 24a_1, 24a_2) near an inner end 24i of a pinion 24 engaged with face gear tooth surfaces 23in_p, 23in_r in an area B of (a) when an inner ring is steered under a high steering torque becomes large is formed as asymmetrical shape in respect to a central plane Z in a direction of tooth thickness as shown at (c). That is, a tooth surface 24a_1 of the tooth surface 24a engaged with the applied tooth surface 23in_p when an inner ring of the face gear 23 is increased in cutting is formed into a shape in which a pressure angle becomes small. In order to solve a decrease in tooth thickness of the pinion tooth 24a accompanied with this state, an opposite tooth surface 24a_2 of the pinion tooth 24a is formed to have such a shape as one in which the pressure angle becomes large in turn.

Description

  TECHNICAL FIELD The present invention relates to a cross-shaft gear transmission mechanism useful for a wheel steering device and the like, and a wheel steering device configured by using it individually for left and right steering wheels, and in particular, the magnitude of transmission torque differs depending on the rotational direction. The present invention relates to a technique for improving the transmission efficiency of a cross shaft gear transmission mechanism when used in a place.

As the cross shaft gear transmission mechanism, for example, one as described in Patent Document 1 has been proposed.
This proposed technique is related to a cross shaft gear transmission mechanism configured to be used in a vehicle steering device, and a non-circular gear is coaxially disposed on a kingpin axis, and is steered to an input gear that is disposed in a cross relationship and meshed therewith. The wheel is steered by inputting the rotation of the wheel.

The non-circular gear that controls the steering of the wheels can give a steering angle difference between the left and right steered wheels (inner and outer wheels), and the vehicle steering pattern can be diversified.
In addition, by transmitting the rotation of the steering wheel to the non-circular gear via the input gear, the rotational movement direction for turning the wheel can be changed, and in this respect also, the vehicle operation pattern can be diversified. is there.

JP 2010-179665 A

  However, in the conventional crossed shaft gear transmission mechanism described above, if the non-circular gear and the input gear are configured as a single unit to be compact, an inconstant speed face gear is used as the non-circular gear. Of the tooth thickness forming tooth surfaces of the input gear, the pressure angle of the tooth surface that bears power transmission increases during wheel turning (when turning the inner wheel) when the corresponding wheel is an inner wheel.

As the pressure angle increases, the radial load from the input gear in the axial direction of the non-circular gear increases, and the transmission efficiency of the cross-shaft gear transmission mechanism, that is, the steering efficiency decreases due to the increase in friction.
At the time of inner wheel turning, since the inner wheel is increased, a larger turning force is required than in other cases, so the above problem becomes more remarkable.
The reduction in transmission efficiency (steering efficiency) leads to a deterioration in steering feeling and an increase in power loss of the power steering, especially in an electric vehicle in which wheels are driven by individual electric motors (in-wheel motors). It is a problem that cannot be done.

  Although the present invention is not limited to a wheel steering device, for example, when used as a wheel steering device, when the wheel is turned into an inner wheel (at the time of inner wheel steering), that is, a large steering force is generated. Reduces the radial angle (friction) and eliminates the above-mentioned problems related to reduced transmission efficiency (steering efficiency) by reducing the pressure angle of the tooth surface that is responsible for power transmission when the inner ring is increased. It is an object of the present invention to propose a cross shaft gear transmission mechanism that can be used.

For this purpose, the cross shaft gear transmission according to the present invention is constructed as follows.
First, to explain the cross shaft gear transmission mechanism which is the premise of the present invention,
A pinion and a face gear arranged so as to have an axis crossing angle with the pinion are configured to mesh with each other, and are practically used in places where the magnitude of transmission torque differs depending on the rotation direction.

The present invention, in such a cross shaft gear transmission mechanism,
When the tooth of the pinion that meshes with the face gear is rotated in the direction in which the pressure angle of the tooth surface, which bears power transmission when rotating in the direction in which the transmission torque is large, of the tooth thickness forming tooth surface, the transmission torque is small. It is characterized in that it is formed to be smaller than the pressure angle of the tooth surface that is sometimes responsible for power transmission.

In the crossed shaft gear transmission mechanism of the present invention, the tooth having the above difference between the pressure angles of the tooth thickness forming tooth surface forming the pinion teeth, and the tooth that bears the power transmission when rotating in the direction in which the transmission torque is large. Because the pressure angle of the surface is smaller than the pressure angle of the tooth surface that bears power transmission when rotating in the direction where the transmission torque is small,
The radial load from the tooth surface that bears power transmission to the face gear during rotation in the direction in which the transmission torque is large is reduced, and the reduction of the friction caused by this reduces the transmission efficiency of the cross shaft gear transmission mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view showing an in-wheel motor-driven wheel of a vehicle provided with a cross shaft gear transmission mechanism as a wheel steering mechanism according to a first embodiment of the present invention, as viewed from the rear of the vehicle, along with its suspension device and steering system. . FIG. 2 is a plan view showing an in-wheel motor drive wheel of a vehicle provided with the wheel steering mechanism in FIG. 1 as viewed from above the vehicle. FIG. 2 is an enlarged plan view showing the wheel turning mechanism in FIG. 1 as viewed from above the vehicle. FIG. 4 is an enlarged longitudinal side view of the steered device that is shown in cross-section on the line IV-IV in FIG. 3 and viewed in the direction of the arrow. FIG. 5 is a plan view showing a gear set in the cross shaft gear transmission mechanism of the first embodiment used as a steering mechanism in FIGS. FIG. 6 is a tooth profile explanatory diagram showing the tooth profile of the face gear in the meshing tooth surface region during outer wheel turning of FIG. 5 as viewed from the inner peripheral side of the face gear. FIG. 6 is a tooth profile explanatory diagram showing the tooth profile of the face gear in the meshing tooth surface region at the time of inner wheel turning shown in FIG. 5 when viewed from the inner peripheral side of the face gear. FIG. 6 is a tooth profile explanatory diagram showing a basic axial perpendicular cross-sectional tooth profile of the pinion in FIG. 5; It is a characteristic diagram which shows the change characteristic of the steering gear ratio requested | required by the steering mechanism using an inconstant speed face gear. The meshing state of the pinion and the face gear in the steering mechanism configured using an inconstant speed face gear is shown. (A) is an explanatory diagram of the meshing state of the pinion and the face gear at the time of outer wheel steering, (b) is FIG. 4 is an explanatory diagram of a meshing state of a pinion and a face gear at the time of inner wheel turning. FIG. 2 is an explanatory diagram of tooth profiles showing tooth shapes of a pinion and a face gear in the differential gear transmission mechanism (steering mechanism) according to the first embodiment of the present invention. It is a figure which shows the cross-shaft gear transmission mechanism used as a turning mechanism which becomes 2nd Example of this invention, (a) is a gear group in this cross-shaft gear transmission mechanism (steering mechanism) seen from upper direction. FIG. 5 is a plan view similar to FIG. 5, (b) is a tooth profile explanatory view showing the tooth profile at the outer peripheral side end of the pinion, (c) is a tooth profile explanatory diagram showing the tooth profile at the inner peripheral end of the pinion face gear, (d) is a tooth profile comparison diagram in which the tooth profile at the outer peripheral side end of the pinion shown in (b) and the tooth profile at the inner peripheral end of the face gear shown in (c) are superimposed on each other for comparison. It is. It is a figure which shows the cross-shaft gear transmission mechanism used as a steering mechanism which becomes 3rd Example of this invention, (a) is a gear set in this cross-shaft gear transmission mechanism (steering mechanism) seen from upper direction. FIG. 5 is a plan view similar to FIG. 5, (b) is a tooth profile explanatory view showing the tooth profile at the outer peripheral side end of the pinion, (c) is a tooth profile explanatory diagram showing the tooth profile at the inner peripheral end of the pinion face gear, (d) is a tooth profile comparison diagram in which the tooth profile at the outer peripheral side end of the pinion shown in (b) and the tooth profile at the inner peripheral end of the face gear shown in (c) are superimposed on each other for comparison. It is.

Hereinafter, embodiments of the present invention will be described in detail based on examples shown in the drawings.
<Configuration of the first embodiment>
1 and 2 show an in-wheel motor-driven wheel 1 of a vehicle in which the cross shaft gear transmission mechanism according to the first embodiment of the present invention is used as a turning mechanism for an Ackermann type steering, together with its suspension device and a turning system. Show.
FIG. 1 is a front view showing the in-wheel motor drive wheel 1 as seen from the rear of the vehicle, and FIG. 2 is a plan view showing the in-wheel motor drive wheel 1 as seen from above the vehicle.

The wheel 1 includes individual in-wheel motor drive units 2 and is driven individually by the unit 2.
Therefore, the in-wheel motor drive unit 2 incorporates an electric motor and a speed reducer (not shown in FIGS. 1 and 2) in the unit case 3, and connects the electric motor to the input shaft of the speed reducer and outputs the output shaft of the speed reducer. Connect the wheel hub 4 to

  The wheel hub 4 is connected to the wheel 1 and the brake disc 5, thereby allowing the vehicle to travel by transmitting the power from the electric motor to the wheel 1 under deceleration by the speed reducer. The brake caliper 13 (see FIG. 2) attached to the in-wheel motor drive unit 2 is clamped from both sides in the axial direction so that the vehicle can be braked.

When the wheel 1 is suspended from the vehicle body, the wheel 1 is suspended by the following suspension device via the case 4 of the in-wheel motor drive unit 2.
As clearly shown in FIG. 1, the suspension device is an upper arm 6 that is an upper suspension arm extending in the vehicle width direction above the unit case 4, and a lower suspension arm that extends in the vehicle width direction below the unit case 4. The lower arm 7, the third link 8, and the shock absorber 9 (including the suspension spring) are generally configured.

The upper arm 6 and the lower arm 7 are respectively supported at the base ends 6a and 7a on the left side (vehicle width direction inner side) in FIG.
The free end 6b on the opposite side of the upper arm 6 (the vehicle width direction outer side) is pivotally supported by the upper end of the third link 8 so as to be swingable in the vertical direction, and the lower end of the third link 8 is swung to the piston rod 9a of the shock absorber 9. Pivot to move.
The shock absorber 9 attaches the cylinder 9b to the vehicle body via the insulator 10.

The in-wheel motor drive unit case 4 is provided with an upper fixed seat 11 extending upward from the upper side surface and a lower fixed seat 12 extending downward from the lower side surface.
The upper end of the upper fixed seat 11 is attached so that it can swing around the kingpin axis Kp that is the turning axis of the wheel 1 in the vicinity of the upper end of the third link 8, and the lower end of the lower fixed seat 12 is attached to the vehicle of the lower arm 7. The free end 7b on the outer side in the width direction is attached so as to be able to swing around the kingpin axis Kp.

The wheel 1 suspended on the vehicle body by the suspension device can be bounced and rebounded in the vertical direction together with the in-wheel motor drive unit 2, and the vertical vibration can be attenuated by the shock absorber 9 during this time.
The wheel 1 and the in-wheel motor drive unit 2 can use a steering knuckle that can be steered around the kingpin axis Kp, and can steer the vehicle.

<Wheel steering device>
A steering mechanism 21 for turning the wheel 1 and the in-wheel motor drive unit 2 around the kingpin axis (Kp) is attached to the third link 8 as shown in FIGS. And disposed above the in-wheel motor drive wheel 1.
This steering mechanism 21 is configured as clearly shown in FIGS. 3 and 4, FIG. 3 is a plan view showing the steering mechanism 21 as viewed from above, and FIG. 4 is a cross-section on the line IV-IV in FIG. It is a detailed sectional view showing the direction of the arrow.

The steering mechanism 21 will be described in detail with reference to FIGS. 3 and 4. Reference numeral 22 denotes a casing, and an annular face gear 23 and a pinion gear 24 meshing with the annular face gear 23 are arranged in a cross-axis relationship in the casing 22. And store.
The face gear 23 is a non-constant speed face gear as shown in FIG. 5, and a key 26 (or a spline) is used on a steered shaft 25 protruding from the upper end of the upper fixed seat 11 so as to provide a kingpin axis Kp as shown in FIG. ) Engageably displaceable in the axial direction, and can rotate around the kingpin axis Kp together with the steered shaft 25.

As shown in FIG. 5, the pinion gear 24 has an angle of 90 degrees with respect to the kingpin axis Kp (face gear 23), but is slightly offset from the kingpin axis Kp so that it can rotate into the housing 22 as shown in FIG. As shown in FIG. 5, the fixed position is set to a position where the pinion gear 24 meshes with the face gear 23.
Although the input shaft 27 is not shown in the figure, it is assumed that the driver is mechanically coupled to a steering wheel that is operated when steering the vehicle, and rotation from the steering wheel is input to the input shaft 27 as rotation.
Thus, the steering force from the steering wheel reaches the turning shaft 25 from the input shaft 27 via the pinion gear 24 and the annular face gear 23, and connects the in-wheel motor drive unit 2 and the wheel 1 via the upper fixed seat 11 to the kingpin axis Kp. Can be steered around.

As shown in FIG. 4, the face gear 23 engaged with the steered shaft 25 so as to be axially displaceable by the key 26 is urged toward the pinion gear 24 by the coil spring 28 wound around the steered shaft 25. Backlash at the meshing portion between the gear 23 and the pinion gear 24 is reduced.
Thus, when the face gear 23 is pushed downward in FIG. 4 against the coil spring 28 by the radial load from the pinion gear 24 to the face gear 23 due to the meshing reaction force, the face gear 23 is moved through the thrust bearing 29. It is supported by the housing 22.

The pinion gear 24 and the inconstant speed face gear 23 will be described in detail below with reference to FIGS.
FIG. 5 is an explanatory diagram showing the meshed state of the pinion gear 24 and the inconstant speed face gear 23 when the wheel 1 is in a non-steering neutral state (straight vehicle traveling state) as viewed from above the kingpin axis Kp.
In FIG. 5, A is a meshing tooth surface region of the face gear 23 (meshing tooth surface region at the time of outer wheel steering) that the pinion 24 meshes with when the wheel 1 is turned as an outer wheel (outer wheel steering). B is a meshing tooth surface region (meshing tooth surface region at the time of inner wheel steering) of the face gear 23 with which the pinion 24 meshes when the wheel 1 is turned as an inner wheel (when the inner wheel is steered).

  FIG. 6 shows an enlarged portion showing meshing tooth surfaces 23out_p and 23out_r of the outer gear wheel when turning the outer ring when the meshing tooth surface area A of the non-constant speed gear 23 is turned from the inner peripheral side of the face gear 23. FIG. 7 is a detailed view, and FIG. 7 shows the meshing tooth surface region B of the infinite speed face gear 23 at the time of inner ring steering when viewed from the inner peripheral side of the face gear 23, and the meshing tooth surface 23in_p of the face gear 23 at the time of inner ring steering. , 23in_r. FIG.

The tooth surface 23out_p shown with short line hatching in FIG. 6 is the tooth surface used when the outer ring is increased, and the tooth surface 23out_r shown with dotted hatching in FIG. 6 is the tooth surface used when the outer ring is cut back. Yes,
The tooth surface 23in_p shown with dotted hatching in FIG. 7 is the tooth surface used when the inner ring is increased, and the tooth surface 23in_r shown with short line hatching in FIG. 7 is the tooth surface used when the inner ring is turned back.

The pinion 24 that meshes with the tooth surfaces 23out_p, 23out_r, 23in_p, and 23in_r of the face gear 23 as described above is an involute gear similar to that used in the parallel shaft gear set. But it is the same shape.
FIG. 8 shows the tooth surface shape of the tooth 24a in a cross section perpendicular to the axis of the pinion 24. Normally, the tooth thickness forming tooth surfaces 24a_1 and 24a_2 are symmetrical with respect to the center surface Z in the tooth thickness direction as shown in FIG. It is.

By the way, as is apparent from the comparison between FIGS. 6 and 7, the inconstant speed face gear 23 changes the shape of the tooth surface 23out_p, 23out_r, 23in_p, 23in_r and the distance from the face gear center Kp to the tooth surface in various ways. Thus, the steering gear ratio characteristic at the time of inner wheel turning and outer wheel turning as shown in FIG. 9 can be realized, and a difference can be given between the turning angle of the inner wheel and the turning angle of the outer wheel among the left and right steering wheels. Configure as follows.
For this reason, the pressure angle at the meshing portion of the pinion 24 and the face gear 23 is large at the time of inner ring steering, and the rotation angle when the meshing advances by one tooth by the rotation of the pinion 24 is large.

FIGS. 10 (a) and 10 (b) schematically show the meshed state of the pinion 24 and the inconstant speed face gear 23 during outer wheel turning and inner wheel turning, respectively.
Since the radial load is proportional to Tan α of the tangential force as shown in the vector diagram of FIG. 10, the larger the pressure angle α is, the larger the radial load (in the face gear axial direction) with respect to a certain tangential force required for torque transmission. Load), which acts in the axial direction of the face gear 23.

By the way, the radial load is a load in a direction irrelevant to the torque transmission, and the larger the radial load, the larger the friction of the thrust bearing 29 (see FIG. 4) that receives the load. Gets worse.
The efficiency η of the steering mechanism 21 is Tout as output torque (face gear rotation torque), Tof as output shaft friction, Tin as input torque (pinion rotation torque), and Tif as input shaft friction.
η = (Tout-Tof) / (Tin + Tif)
It is expressed by the following formula.
The friction of the thrust bearing 29 (see FIG. 4) includes the output shaft friction described above in Tof. When this friction increases due to an increase in radial load, the efficiency η of the steering mechanism 21 decreases as is apparent from the above equation.

Moreover, in general automobiles, the steering torque required for wheel steering increases as the steering wheel turns when the steered wheel is an inner wheel (when the inner wheel is increased and turned). The deterioration of η becomes even more remarkable.
Thus, when the efficiency η of the steering mechanism 21 is deteriorated, the steering feeling is deteriorated, or the required assist force value of the power steering is increased, which causes a problem that a large assist motor for realizing this is required. .

From the above viewpoint, at the time of turning the inner ring while turning the inner ring where the efficiency η of the steering mechanism 21 is significantly deteriorated, it is indispensable to reduce the above-described radial load in order to avoid this deterioration in efficiency.
Therefore, in this embodiment, the teeth 24a (tooth surfaces 24a_1, 24a_2) of the pinion 24 that mesh with the non-constant speed face gear 23 at the time of inner ring turning shown in FIG. Rather than a symmetrical shape with respect to Z, it is formed in a laterally asymmetric shape as described below with reference to FIG.

First, the tooth surface 24a_1 of the pinion tooth 24a meshing with the tooth surface 23in_p used when the inner ring of the face gear 23 is increased is changed from the general shape shown by the broken line in FIG. 11, that is, from the shape shown in FIG. As shown by a solid line in FIG. 10, the pressure angle α in FIG.
Such deformation of the pinion tooth surface 24a_1 is accompanied by insufficient strength of the pinion teeth 24a by reducing the thickness of the pinion teeth 24a.

  Therefore, in this embodiment, in order to avoid insufficient strength of the pinion teeth 24a, the opposite tooth surface 24a_2 of the pinion teeth 24a has a general shape shown by a broken line in FIG. 11, that is, a shape shown in FIG. 10 (b). Then, as shown by a solid line in FIG. 11, the pressure angle is deformed to a large shape.

  In accordance with the above-described deformation of the pinion tooth surfaces 24a_1 and 24a_2, the shapes of the tooth surface 23in_p used when the inner ring is increased and the tooth surface 23in_r used when the inner ring is turned back are also shown by broken lines in FIG. Needless to say, the shape is changed from the general shape shown to the shape shown by the solid line.

<Effects of the first embodiment>
According to the steering mechanism 21 of the first embodiment described above, the tooth surface used when the inner ring of the face gear 23 is increased at the time of turning, the inner ring is increased and the inner ring is increased because of the Ackermann type steering that steers the inner ring larger than the outer ring. Since the tooth surface 24a_1 of the pinion tooth 24a meshing with 23in_p is deformed so that the pressure angle α becomes small,
The radial load from the pinion 24 to the face gear 23 can be reduced by the decrease in the pressure angle α.

Therefore, even when turning the inner ring with increased steering force, the radial load from the pinion 24 to the face gear 23 does not increase, and the friction of the thrust bearing 29 and the like can be kept small. The transmission efficiency (steering efficiency) can be increased.
Accordingly, it is possible to avoid problems related to deterioration in steering feeling during turning of the inner wheel where the steering force is increased and a large energy loss in power steering.

Further, in this example, the deformation of the pinion tooth surface 24a_1 performed to achieve the above action / effect reduces the strength of the pinion tooth 24a by reducing the thickness of the pinion tooth 24a, but the pressure on the opposite tooth surface 24a_2 of the pinion tooth 24a Since the corners are deformed to increase, it is possible to avoid a reduction in the thickness of the pinion teeth 24a, and the strength of the pinion teeth 24a does not decrease.
The above-described deformation of the pinion tooth surface 24a_2 results in an increase in the pressure angle, but during the inner ring switchback turning performed by the engagement of the pinion tooth surface 24a_2 and the tooth surface 23in_r used when the face gear 23 is switched back to the inner ring Since the steering force is originally small, the aforementioned radial load does not become a problem even if the pressure angle increases.

<Second embodiment>
FIG. 12 shows a main part of the steering mechanism 21 using the cross shaft gear transmission mechanism according to the second embodiment of the present invention.
FIG. 12 (a) is a drawing similar to FIG. 5 showing the internal gear set of the steering mechanism 21, and in this embodiment, the pinion 24 located on the outer peripheral side edge 24o of the pinion 24 located in the outer peripheral direction of the face gear 23. The pinion teeth 24a that mesh with the tooth surface 23out_p when the outer ring of the face gear 23 is increased and the tooth surface 23out_r when the outer ring is turned back are formed as shown by the thick solid line in FIG. FIG. 12 (c) shows the pinion teeth 24a at the inner peripheral side edge 24i of the pinion 24 located in the circumferential direction and meshing with the tooth surface 23in_p when the inner ring of the face gear 23 is increased and the tooth surface 23in_r when the inner ring is turned back. ) As shown by the thin solid line.

As clearly shown in FIG. 12 (d), the pinion teeth 24a at the face gear outer peripheral side end 24o and the face gear inner peripheral side end 24i of the pinion 24 are overlapped for comparison.
The pinion teeth 24a at the face gear outer peripheral end 24o of the pinion 24 meshing with the tooth surface 23out_p used when the outer ring of the face gear 23 is increased and the tooth surface 23out_r used when the outer ring is turned back are connected to the pressure angle of the tooth surface 24a_1 and the tooth surface 24a_2. Form the pressure angle difference between the pressure angles to be minimal,
The pinion tooth 24a at the face gear inner peripheral end 24i of the pinion 24 that meshes with the tooth surface 23in_p used when the inner ring of the face gear 23 is increased and the tooth surface 23in_r used when the inner ring is turned back is replaced with the pressure angle of the tooth surface 24a_1 and the tooth surface 24a_2. The pressure angle difference between the pressure angles is maximized (same as in the first embodiment),
The teeth 24a of the pinion 24 are formed so that the pressure angle difference is gradually reduced from the face gear inner peripheral end 24i of the pinion 24 toward the face gear outer peripheral end 24o.

That is, the pinion tooth 24a is formed such that, among the tooth surfaces 24a_1 and 24a_2, the pressure angle of one tooth surface decreases as it goes toward the outer end 24o, and the pressure angle of the other tooth surface increases as it goes toward the outer end 24o. .
The wheel turning device is the same as that of the first embodiment except that the pinion 24 of the turning mechanism 21 is formed as described above.

<Effect of the second embodiment>
The effects of the second embodiment will be described below.
As in the first embodiment described above, when the tooth surface 24a_1 used for turning the inner ring of the pinion 24 is steered so as to reduce the pressure angle, the inconstant speed face gear 23 is hatched in FIG. The pressure angles of the tooth surface 23out_r used when the outer ring is cut back and the tooth surface 23in_p used when the inner ring is increased are reduced.

As is apparent from a comparison between FIG. 6 showing the meshing tooth surface area A during outer ring steering and FIG. 7 showing the meshing tooth surface area B during inner ring steering, the meshing tooth surface area A during outer wheel steering is more inner. The pressure angle is smaller than that of the meshing tooth surface region B at the time of wheel steering, and a phenomenon of so-called gear down is likely to occur.
Further, as can be seen from FIG. 6, the tooth surfaces 23out_p and 23out_r in the meshing tooth surface region A of the inconstant speed face gear 23 at the time of turning the outer ring have a smaller pressure angle toward the inner peripheral side end of the face gear and are likely to be cut down. .
Here, the term “cut down” refers to a phenomenon in which after the tooth surfaces mesh with each other, the counterpart tooth tip cuts into the tooth surfaces. When the cut down occurs, there is no effective tooth surface for torque transmission.

As shown in Fig. 7, because the tooth angle 23in_p used when the inner ring is increased with a large number of hatches has a large pressure angle, the pressure angle difference between the tooth surface 23in_p when the inner ring is increased and the tooth surface 23in_r used when the inner ring is turned back Even if a pressure angle difference as in the first embodiment is set between the pressure angle and the pressure angle, the problem of devaluation is unlikely to occur.
However, as shown in FIG. 6, the tooth surface 23out_r that is used when the outer ring is cut back with hatching is easily cut down and the effective tooth surface is inevitably reduced.
When the effective tooth surface becomes small in this way, there arises a problem that the teeth of the face gear 23 become insufficient in strength.

Incidentally, in this embodiment, as described above with reference to FIG. 12, the pressure angle difference between the tooth surfaces 24a_1 and 24a_2 of the pinion teeth 24a at the inner end 24i of the pinion 24 is the same as that in the first embodiment, and this pressure angle difference Since the teeth 24a of the pinion 24 are formed so as to gradually become smaller toward the outer end 24o of the pinion 24,
Effective for torque transmission by avoiding the above-mentioned problem of lowering at the outer end 24o of the pinion 24 that meshes with the tooth surface 23out_p used when the outer ring of the face gear 23 is increased and the tooth surface 23out_r used when the outer ring is turned back. The problem that the tooth surface does not exist can be solved.

  However, the pressure angle difference between the tooth surfaces 24a_1 and 24a_2 of the pinion tooth 24a at the inner end 24i of the pinion 24 that meshes with the tooth surface 23in_p when the inner ring is increased and the tooth surface 23in_r when the inner ring is turned back is increased. Since the teeth 24a of the pinion 24 are formed to have the same size as that of the first embodiment, the operation and effect of the first embodiment can be achieved as they are.

<Third embodiment>
FIG. 13 shows a third embodiment of the present invention in which the same effect as that of the second embodiment, that is, the effect of avoiding the above-described devaluation problem at the outer end 24o of the pinion 24 is achieved by another countermeasure. The principal part of the steering mechanism 21 using the cross shaft gear transmission mechanism which becomes an Example is shown.
FIG. 13 (a) is a drawing similar to FIG. 5 showing the internal gear set of the steered mechanism 21, and in this embodiment, the pinion 24 located on the outer peripheral side 24o of the pinion 24 located in the outer peripheral direction of the face gear 23. The pinion teeth 24a that mesh with the tooth surface 23out_p when the outer ring of the face gear 23 is increased and the tooth surface 23out_r when the outer ring is turned back are formed as shown by a thick solid line in FIG. FIG. 13 (c) shows the pinion teeth 24a at the inner peripheral side edge 24i of the face gear of the pinion 24 located in the circumferential direction and meshing with the tooth surface 23in_p used when the inner ring of the face gear 23 is increased and the tooth surface 23in_r used when the inner ring is turned back. ) As shown by the thin solid line.

As clearly shown in FIG. 13 (d), the pinion teeth 24a on the face gear outer peripheral side end 24o and the face gear inner peripheral side end 24i of the pinion 24 are overlapped for comparison.
The pinion tooth 24a at the face gear inner peripheral end 24i of the pinion 24 that meshes with the tooth surface 23in_p used when the inner ring of the face gear 23 is increased and the tooth surface 23in_r used when the inner ring is turned back is replaced with the pressure angle of the tooth surface 24a_1 and the tooth surface 24a_2. The pressure angles are respectively the same as in the first embodiment,
The pinion tooth 24a at the outer end 24o of the pinion 24 meshed with the tooth surface 23out_p used when the outer ring of the face gear 23 is increased and the tooth surface 23out_r used when the outer ring is cut back, the pressure angle of the tooth surface 24a_1 and the pressure angle of the tooth surface 24a_2 are Respectively, it is formed to be larger than the pressure angle of the tooth surface 24a_1 of the pinion tooth 24a and the pressure angle of the tooth surface 24a_2 at the inner end 24i of the pinion 24,
The teeth 24a of the pinion 24 are formed such that the pressure angle of the tooth surface 24a_1 and the pressure angle of the tooth surface 24a_2 gradually increase from the inner end 24i of the pinion 24 toward the outer end 24o.

That is, the pinion teeth 24a are formed so that the pressure angles of the tooth surfaces 24a_1 and 24a_2 both increase toward the outer end 24o.
When continuously changing the pressure angle of the pinion tooth surfaces 24a_1 and 24a_2 in the pinion axis direction, it is only necessary to set the parameters so that the dislocation coefficient increases toward the outer end 24o of the pinion 24, that is, the pinion 24 It is only necessary to change the dislocation coefficient in the direction of the pinion axis at the time of manufacture.

And when changing the above dislocation coefficient, the pinion 24 only moves the cutter in the radial direction of the pinion 24 at the same time while creating the pinion tooth surface by moving the cutter in the axial direction of the pinion 24 at the time of producing the pinion. Is easy to manufacture and is very advantageous in terms of cost.
The wheel turning device is the same as that of the first embodiment except that the pinion 24 of the turning mechanism 21 is formed as described above.

<Effect of the third embodiment>
The effects of the third embodiment will be described below.
In this embodiment, as described above with reference to FIG. 13, the pressure angles of the tooth surfaces 24a_1 and 24a_2 of the pinion teeth 24a at the inner end 24i of the pinion 24 are set in the same manner as in the first embodiment, and these pinion tooth surfaces 24a_1 , 24a_2 because the teeth 24a of the pinion 24 are formed so that both pressure angles gradually increase toward the outer end 24o of the pinion 24,
Effective for torque transmission by avoiding the above-mentioned problem of lowering at the outer end 24o of the pinion 24 that meshes with the tooth surface 23out_p used when the outer ring of the face gear 23 is increased and the tooth surface 23out_r used when the outer ring is turned back. The problem that the tooth surface does not exist can be solved.

  Moreover, when the pressure angles of both the pinion tooth surfaces 24a_1 and 24a_2 are continuously changed in the pinion axial direction as in this embodiment, the pinion tooth surface is created by moving the cutter in the axial direction of the pinion 24 during the production of the pinion. At the same time, since it is only necessary to move the cutter in the radial direction of the pinion 24, it is easy to manufacture the pinion 24 and it is advantageous in terms of cost, so the same effect as the second embodiment can be obtained easily and inexpensively. Can be obtained.

  Note that the pressure angle of the tooth surfaces 24a_1 and 24a_2 of the pinion teeth 24a at the inner end 24i of the pinion 24 that meshes with the tooth surface 23in_p used when the inner ring of the face gear 23 is increased and the tooth surface 23in_r used when the inner ring is turned back is the first embodiment. Since the teeth 24a of the pinion 24 are formed to have the same size as the example, the operation and effect of the first embodiment can be achieved as they are.

<Other examples>
In any of the first to third embodiments, the case where the cross shaft gear transmission mechanism of the present invention is used as the steering mechanism 21 of the in-wheel motor drive wheel 1 has been described. However, the cross shaft gear transmission mechanism of the present invention is also described. The application is not limited to this, and the present invention can be applied to any application as long as the transmission torque differs depending on the rotation direction and the cross-axis transmission is required.

1 In-wheel motor drive wheel
2 In-wheel motor drive unit
2a Electric motor
2b reducer
3 Unit case
4 Wheel hub
5 Brake disc
6 Upper arm
7 Lower arm
8 Third link
9 Shock absorber
10 Insulator
13 Brake caliper
Kp Kingpin axis
21 Steering mechanism
22 Enclosure
23 Constant speed face gear
23in_p Tooth surface used when the inner ring is increased
23in_r Tooth surface used when inner ring is cut back
23out_p Tooth surface used when adding outer ring
23out_r Tooth surface used when outer ring is cut back
24 pinion
24a pinion teeth
24a_1,24a_2 Pinion tooth surface
25 Steering shaft
26 keys
27 Input shaft
28 Coil spring
29 Thrust bearing

Claims (5)

In the cross shaft gear transmission mechanism that is configured by meshing a pinion and a face gear arranged so as to have an axis crossing angle with respect to the pinion, and that is practically used in places where the magnitude of the transmission torque differs depending on the rotation direction,
When the tooth of the pinion that meshes with the face gear is rotated in the direction in which the pressure angle of the tooth surface, which bears power transmission when rotating in the direction in which the transmission torque is large, of the tooth thickness forming tooth surface, the transmission torque is small. A cross-shaft gear transmission mechanism characterized in that it is formed to be smaller than the pressure angle of the tooth surface sometimes responsible for power transmission. In the cross shaft gear transmission mechanism according to claim 1,
The face gear is an inconstant speed face gear, and the pinion teeth are formed such that the difference in pressure angle between the tooth thickness forming tooth surfaces of the pinion teeth is large on the inner peripheral side of the face gear and smaller on the outer peripheral side. Characteristic cross-shaft gear transmission. In the cross shaft gear transmission mechanism according to claim 1,
The face gear is an inconstant speed face gear, and the pinion teeth are formed so that the pressure angle at the tooth thickness forming tooth surface of the pinion teeth is larger toward the outer peripheral side of the face gear than at the inner peripheral side of the face gear. Cross shaft gear transmission mechanism characterized by In the cross shaft gear transmission mechanism according to claim 3,
By increasing the dislocation coefficient of the pinion teeth toward the outer peripheral side of the face gear, the pressure angle at the tooth thickness forming tooth surface of the pinion teeth is increased toward the outer peripheral side of the face gear compared to the inner peripheral side of the face gear. A cross shaft gear transmission mechanism characterized in that pinion teeth are formed. The cross shaft gear transmission mechanism described in any one of claims 1 to 4 is used as an individual steering mechanism of left and right steering wheels to be steered by an Ackermann type steering mechanism,
The cross-shaft gear transmission mechanisms related to these left and right steering wheels are turned so that the rotation of the steering wheel is input to the pinion and the left and right steering wheels are steered by the face gear, and the left and right steering wheels are turned into inner wheels. A wheel steering apparatus characterized in that the cross-shaft gear transmission mechanism is disposed and mounted on a vehicle so that the tooth surface having a small pressure angle bears transmission of a low striking force when increased.

Images