JP2009257515A - Shift mechanism of automatic transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shift mechanism of an automatic transmission capable of smoothly operating. <P>SOLUTION: The shift mechanism of the automatic transmission includes a worm gear 13 rotated by an electric motor 12 and a worm wheel 14 engaged with the worm gear. Rotation of the worm wheel 14 axially moves a fork shaft via a wheel shaft 15 to switch engagement of a shift gear. The electric motor 12 and the worm gear 13 are mounted with support springs 17 to energize the worm gear 13 toward the worm wheel 14. The worm gear 13 is movable to a direction away from the worm wheel 14. When excessive load is applied on the worm gear 13 by driving force from the electric motor 12, the worm gear 13 slips on a tooth surface of the worm wheel 14 to release the engagement with the worm wheel 14 against the energizing force of the support springs 17. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a shift mechanism of an automatic transmission used for a vehicle.

  2. Description of the Related Art Conventionally, there are various shift mechanisms for moving a sleeve in order to switch the meshing of a transmission gear in an automatic transmission device for a vehicle. There has been a related art related to a shift mechanism that moves a working member through a speed reduction mechanism by a power source and moves a fork shaft engaged with the working member in an axial direction to operate a sleeve engaged with the fork (for example, , See Patent Document 1).

In the shift mechanism, downsizing of a power source such as an electric motor is desired from the viewpoint of installation space on a vehicle or cost. When the electric motor is miniaturized, the output torque thereof is reduced, so that it is necessary to increase the output of the speed reduction mechanism. Here, in order to increase the output torque in the speed reduction mechanism, it is conceivable to form a combination of a worm gear and a worm wheel (gear) capable of setting a large input / output gear ratio.
JP-A-2005-226687

In a shift mechanism using a worm gear and a worm wheel, when the shift operation is completed and the sleeve comes into contact with the stopper and the fork shaft stops, the worm wheel cannot rotate any further. Nevertheless, if the worm gear continues to be driven by the electric motor and excessive torque is applied from the worm gear to the worm wheel, the gear teeth are engaged at the meshing portion of the worm gear and the worm wheel. There was a risk of becoming locked. When the gear teeth of the worm gear and the worm wheel are in a locked state, it becomes difficult to disengage both even if the electric motor is rotated in both forward and reverse directions, and smooth operation of the shift mechanism is hindered.
The present invention has been made in view of the above circumstances, and an object thereof is to provide a shift mechanism of an automatic transmission that can operate smoothly.

The present invention relates to an electric motor, a worm gear rotated by the electric motor, a worm wheel meshed with the worm gear and rotated by the electric motor via the worm gear, a transmission member rotating together with the worm wheel, and an engagement with the transmission member And a shift mechanism of an automatic transmission comprising a shift shaft that is movable in the axial direction by rotation of the transmission member, and a sleeve that engages with the shift shaft and switches the meshing of the transmission gear by moving together with the shift shaft. A biasing means is provided between the base for rotatably supporting the worm wheel and the worm gear to urge the worm gear toward the worm wheel and to engage the worm gear with the worm wheel. The worm gear moves away from the worm wheel. It is movable and is driven by the driving force from the electric motor. When a predetermined load is applied to Mugiya, worm gear slides on the tooth face of the worm wheel, meshing with the worm wheel against the biasing force of the biasing means is releasably formed.
As a result, even if excessive torque is applied to the worm gear by the electric motor after the shift operation is completed and the worm wheel is stopped, it is possible to prevent both the meshes from being released and locked. The mechanism can operate smoothly.

Further, in the present invention, the base portion has a wall portion formed in the vicinity of the worm gear, a guide groove extending in the moving direction of the worm gear is formed in the wall portion, and the guide protrusion provided in the worm gear is formed in the guide groove. The parts are movably engaged.
As a result, the worm gear can move smoothly along the guide groove, and the meshing between the worm gear and the worm wheel is released smoothly.

  A shift mechanism of an automatic transmission according to an embodiment of the present invention will be described with reference to FIGS. A drive device 1 forming a shift mechanism includes a wheel shaft 15 (corresponding to a transmission member of the present invention) rotatably supported by an outer wall 111 of a housing 11 (corresponding to a base portion of the present invention). A pinion gear 15a is formed at one end of the wheel shaft 15 protruding from the outer wall 111 of the eleventh (shown in FIG. 1).

  A fork 21 is attached to the first fork shaft 2 that shifts between the first speed and the second speed of the automatic transmission (the configuration including the first fork shaft 2 and the fork 21 corresponds to the shift shaft of the present invention. The fork 21 is engaged with a sleeve 22 (corresponding to the sleeve of the present invention). The sleeve 22 moves on an output shaft (not shown) of the automatic transmission and selectively meshes with a transmission gear (not shown). By engaging the meshed transmission gear with the output shaft, the plurality of transmission gears are engaged. Is switched. Rack teeth 2 a are formed on the first fork shaft 2, and the rack teeth 2 a mesh with the pinion gear 15 a of the wheel shaft 15 described above. Thus, when the wheel shaft 15 rotates, the first fork shaft 2 can move in the axial direction together with the fork 21.

  The second fork shaft 3 shifts between the third speed and the fourth speed of the automatic transmission, and a fork 31 engaged with a sleeve 32 is attached in the same manner as the first fork shaft 2 (the second fork shaft 3 and the fork The configuration including 31 corresponds to the shift shaft of the present invention), and meshes with a wheel shaft (not shown) of a drive device different from the drive device 1 described above.

  Further, the third fork shaft 4 shifts between the fifth speed and the reverse of the automatic transmission, and a fork (not shown) engaged with a sleeve is attached similarly to the first fork shaft 2, and the above-described drive It meshes with a wheel shaft (not shown) of a drive device different from the device 1.

  An electric motor 12 (shown in FIG. 2 and corresponding to the electric motor of the present invention) is provided in the housing 11 of the driving device 1, and a driving circuit (not shown) in the controller 5 is provided in the electric motor 12. It is connected. The controller 5 is connected to a rotational position sensor 6, a lever position sensor 7, and a vehicle speed sensor 8. The rotational position sensor 6 is formed by, for example, a pulse encoder or the like, and detects the rotational position of the wheel shaft 15. The lever position sensor 7 is attached to the operation change lever 9 of the automatic transmission, and detects the operation position of the operation change lever 9. The vehicle speed sensor 8 is a rotational speed sensor attached to the output shaft of the automatic transmission, and detects the traveling speed of the vehicle. The controller 5 controls the operation of the electric motor 12 based on input signals from the rotational position sensor 6, lever position sensor 7 and vehicle speed sensor 8.

  As shown in FIGS. 2 to 4, a worm gear 13 (corresponding to the worm gear of the present invention) is provided in the housing 11 of the drive device 1. The worm gear 13 has a worm body 132 rotatably supported by a pair of bearings 131, and worm gear teeth 133 are formed on the outer peripheral surface of the worm body 132. The worm body 132 is connected to the output shaft 121 of the electric motor 12 and is rotatable by the electric motor 12.

  The worm wheel 14 (corresponding to the worm wheel of the present invention) has worm wheel gear teeth 141 on the outer peripheral surface, which mesh with the worm gear teeth 133 of the worm body 132. Thus, the worm wheel 14 is formed to be rotatable by the electric motor 12 via the worm gear 13.

  As shown in FIG. 4, a first wall portion 112 (corresponding to the wall portion of the present invention) extending in the vertical direction is integrally formed in the housing 11. As described above, the other end portion of the wheel shaft 15 whose one end portion protrudes from the outer wall 111 of the housing 11 passes through the first wall portion 112, and the wheel shaft 15 passes through the bearing 16 and the first wall portion 112. It is supported so that it can rotate. The wheel shaft 15 is fixed to the worm wheel 14 so as to pass through the center thereof. As a result, the worm wheel 14 is rotatably supported by the housing 11 together with the wheel shaft 15.

  A second wall portion 113 (corresponding to the wall portion of the present invention) extending in the vertical direction so as to sandwich the electric motor 12 and the worm gear 13 from the side together with the first wall portion 112 is integrally formed in the housing 11. (Shown in FIGS. 3 and 4). In the vicinity of the worm gear 13, three guide grooves 112 a extending in the vertical direction (corresponding to the moving direction of the worm gear 13 as will be described later) are provided on both the first wall portion 112 and the second wall portion 113 facing each other. , 113a (corresponding to the guide groove of the present invention) is formed.

On the other hand, a pair of engaging convex portions 122 are formed on the outer peripheral surface of the rear end of the electric motor 12. The engagement convex portion 122 is formed at the 3 o'clock and 9 o'clock positions of the watch, which are positions closest to the first wall portion 112 and the second wall portion 113 in the outer peripheral surface of the electric motor 12 having a circular cross section. ing. Each engagement convex part 122 is engaged with the guide grooves 112a and 113a formed in the 1st wall part 112 and the 2nd wall part 113 so that a movement is possible.
In addition, a pair of protrusions 134 (corresponding to the guide protrusions of the present invention) are formed on both side surfaces of each bearing 131 of the worm gear 13, and these are the first wall portion 112 and the second wall portion 113, respectively. The guide grooves 112a and 113a formed in the slidably engage with each other.

  Furthermore, one end of a support spring 17 (corresponding to the biasing means of the present invention) formed by a helical spring is attached to the lower end of the electric motor 12, and the other end of the support spring 17 is the bottom surface of the housing 11. 114 is fixed. Similarly, one end of a similar support spring 17 (corresponding to the urging means of the present invention) is attached to the lower end of each of the pair of bearings 131 of the worm gear 13, and the other end of each support spring 17 is It is fixed to the bottom surface 114 of the housing 11.

  The support spring 17 attached to the electric motor 12 and the bearing 131 is compressed between the bottom surface 114 and urges the worm gear 13 toward the worm wheel 14 with a predetermined load. The worm gear 13 meshes with the worm wheel 14. I am letting. The worm gear 13 can move in the direction away from the worm wheel 14 on the guide grooves 112a and 113a, and can be released from meshing with the worm wheel 14 against the urging force of the support spring 17.

  Next, an operation method of the shift mechanism according to the present embodiment will be described. For example, when the vehicle is traveling with the automatic transmission at the first speed, the controller 5 determines that the automatic transmission is to be shifted to the second speed based on detection signals from the lever position sensor 7 and the vehicle speed sensor 8. Then, a drive current is supplied from the drive circuit of the controller 5 to the electric motor 12. The electric motor 12 supplied with the drive current rotates in one direction to rotate the worm body 132 of the worm gear 13.

  At this time, the worm wheel 14 meshed with the worm gear 13 by the urging force from the support spring 17 is also rotated in one direction to rotate the wheel shaft 15. As the wheel shaft 15 rotates, the fork shaft 2 formed with the rack teeth 2a meshing with the pinion gear 15a moves in the axial direction. The fork shaft 2 that has moved in the axial direction moves the sleeve 22 onto the output shaft via the fork 21 to switch the meshing of the transmission gear.

  The change of meshing of the transmission gear is completed, and the sleeve 22 abuts against a stopper (not shown) and stops, whereby the rotation of the worm wheel 14 via the fork shaft 2 is also stopped. Even if the rotation of the worm wheel 14 is stopped, if the drive of the electric motor 12 is continued, the load applied to the worm gear 13 gradually increases. When the load applied to the worm gear 13 becomes a predetermined load and the load for separating the worm gear 13 from the worm wheel 14 becomes larger than the resistance force due to the predetermined urging force or the like by the support spring 17, the worm gear teeth 133 are moved to the worm wheel gear. Slide out on the tooth surface of the tooth 141. As a result, the worm gear 13 moves away from the worm wheel 14 against the urging force of the support spring 17 and the like, and the meshing between the worm gear 13 and the worm wheel 14 is released. It is avoided that the vehicle is idling and locked with the worm wheel 14.

  Based on FIG. 5, the release of the mesh between the worm gear 13 and the worm wheel 14 described above will be described in detail. For convenience of explanation, it is assumed that a load generated between the worm gear teeth 133 and the worm wheel gear teeth 141 by the driving force of the electric motor 12 or the urging force of the support spring 17 is applied at one point on the tooth surface. Further, the influence of gravity acting on the electric motor 12 and the worm gear 13 is ignored.

  Now, it is assumed that an upward load F 1 in FIG. 5 is applied to the worm gear teeth 133 by the support spring 17 that biases the electric motor 12 and the worm gear 13. Further, it is assumed that a leftward load F4 in FIG. 5 is applied to the worm gear teeth 133 by the driving force of the electric motor 12.

  Here, if the inclination of the tooth surface of the worm gear tooth 133 and the tooth surface of the worm wheel gear tooth 141 are both θ, the load F1 by the support spring 17 is a component force F2 perpendicular to the tooth surface of the worm wheel gear tooth 141 and the tooth. It can be broken down into component force F3 parallel to the surface. Then, the component force F3 parallel to the tooth surface of the worm wheel gear tooth 141 acts as a load for meshing the worm gear 13 with the worm wheel 14. Further, if the coefficient of friction between the tooth surface of the worm gear tooth 133 and the tooth surface of the worm wheel gear tooth 141 is μ, the component force F2 perpendicular to the tooth surface of the worm wheel gear tooth 141 is such that the worm gear 13 is the worm wheel. 14 acts as a frictional force μF2 that becomes resistance when sliding in the direction in which the mesh is released.

  On the other hand, the load F4 generated by driving the electric motor 12 can be decomposed into a component force F5 perpendicular to the tooth surface of the worm wheel gear tooth 141 and a component force F6 parallel to the tooth surface. Then, the component force F6 parallel to the tooth surface of the worm wheel gear tooth 141 causes the worm gear tooth 133 to slide downward with respect to the worm wheel gear tooth 141 in FIG. Works as a load to move. Further, the component force F5 perpendicular to the tooth surface of the worm wheel gear tooth 141 acts as a frictional force μF5 that becomes a resistance when the worm gear 13 slides on the worm wheel 14 in a direction in which the meshing is released.

Therefore, when the worm gear 13 moves in a direction parallel to the tooth surface of the worm wheel gear tooth 141 and away from the worm wheel 14, the relationship between the loads is as follows:
F6> F3 + μF2 + μF5 (1)
It becomes.
Here, since F2 = F1 × sin θ, F3 = F1 × cos θ, F5 = F4 × cos θ, and F6 = F4 × sin θ, the above equation (1) is
F4 × sin θ> F1 × cos θ + μF1 × sin θ + μF4 × cos θ (2)
If the above equation (2) is modified,
F4> (cos θ + μ sin θ) F1 / | sin θ−μ cos θ | (3) However, | sin θ−μcos θ | represents the absolute value of sin θ−μcos θ.

  That is, if the load F4 applied by driving the electric motor 12 increases and the expression (3) is established before the worm gear 13 and the worm wheel 14 are locked, the urging force of the worm gear 13 by the support spring 17 is satisfied. It can move in the direction away from the worm wheel 14 against such as.

  Therefore, for example, by experiment, the load F4 (0) applied to the worm gear 13 by the electric motor 12 at the moment when the space between the worm gear 13 and the worm wheel 14 is in a locked state is obtained. When the load F4 (1) is smaller by a predetermined amount than the load F4 (0) in consideration of various variations in member dimensions, etc., the load F1 (support) by the support spring 17 so that equation (3) is satisfied. It can be seen that it is only necessary to set the free length of the spring 17, the set length, and the spring constant. Here, the load F4 (1) is smaller than the load F4 (0) and drives the worm wheel 14 in order to reliably complete the shift operation against the load received by the worm gear 13 from the worm wheel 14. It is better to set it to a sufficient value.

According to the present embodiment, the electric motor 12, the worm gear 13 rotated by the electric motor 12, the worm wheel 14 meshed with the worm gear 13 and rotated by the electric motor 12 via the worm gear 13, and the worm wheel 14 The rotating wheel shaft 15, the fork shaft 2 engaged with the wheel shaft 15 and movable in the axial direction by the rotation of the wheel shaft 15, and the engagement of the transmission gear by engaging with the fork shaft 2 and moving together with the fork shaft 2 The worm gear 13 is urged toward the worm wheel 14 between the housing 11 that rotatably supports the worm wheel 14 and the worm gear 13, and the worm gear 13 is engaged with the worm wheel 14. Support A ring 17 is provided, and the worm gear 13 is movable in a direction away from the worm wheel 14. When a predetermined load is applied to the worm gear 13 by the driving force from the electric motor 12, the worm gear 13 is moved to the worm wheel 14. It is formed so that the meshing with the worm wheel 14 can be released against the urging force of the support spring 17.
As a result, even if an excessive torque is applied to the worm gear 13 by the electric motor 12 after the shift operation is completed and the worm wheel 14 is stopped, it is possible to avoid the meshing of both and the locked state. Therefore, the shift mechanism can operate smoothly.

Further, according to this embodiment, the housing 11 has the first wall portion 112 and the second wall portion 113 formed in the vicinity of the worm gear 13, and both the wall portions 112, 113 are arranged in the moving direction of the worm gear 13. Extending guide grooves 112a and 113a are formed, and engaging protrusions 122 provided on the electric motor 12 and protrusions 134 provided on the worm gear 13 are movably engaged with the guide grooves 112a and 113a. .
Thereby, the electric motor 12 and the worm gear 13 can move smoothly along the guide grooves 112a and 113a, and the meshing between the worm gear 13 and the worm wheel 14 is smoothly released.
<Other embodiments>

The present invention is not limited to the above-described embodiments, and can be modified or expanded as follows.
A selection mechanism may be provided so that the single drive device 1 is selectively engaged with the plurality of fork shafts 2 in accordance with the shift speed.
The support spring 17 does not necessarily have to be attached to the electric motor 12 and may be attached only to the worm gear 13 at least.
The means for urging the worm gear 13 to engage with the worm wheel 14 is not limited to the helical spring, but may be a conical spring, a leaf spring, or elastic rubber.
The load F4 (0) applied to the worm gear 13 by the electric motor 12 at the moment when the worm gear 13 and the worm wheel 14 are locked may be obtained by theoretical calculation.

1 is an overall view of a shift mechanism of an automatic transmission according to an embodiment of the present invention. 1 is an internal side view of the driving device shown in FIG. Bottom view of FIG. Side view of FIG. Detailed view of part A in FIG.

Explanation of symbols

  In the drawings, 2, 3 and 4 are fork shafts (shift shafts), 11 is a housing (base), 12 is an electric motor, 13 is a worm gear, 14 is a worm wheel, 15 is a wheel shaft (transmission member), and 17 is a support spring. (Biasing means) 21 and 31 are forks, 22 and 32 are sleeves, 112 is a first wall (wall), 113 is a second wall (wall), 112a and 113a are guide grooves, and 133 is a worm gear. Teeth 134 are protrusions (guide protrusions), and 141 is a worm wheel gear tooth.

Claims (2)

An electric motor;
A worm gear rotated by the electric motor;
A worm wheel meshed with the worm gear and rotated by the electric motor through the worm gear;
A transmission member that rotates with the worm wheel;
A shift shaft that engages with the transmission member and is movable in the axial direction by rotation of the transmission member;
In a shift mechanism of an automatic transmission comprising a sleeve that engages with the shift shaft and switches the meshing of the transmission gear by moving together with the shift shaft,
A biasing means for biasing the worm gear toward the worm wheel and meshing the worm gear with the worm wheel is provided between the worm gear and the base portion that rotatably supports the worm wheel,
The worm gear is movable in a direction away from the worm wheel, and when a predetermined load is applied to the worm gear by a driving force from the electric motor, the worm gear slides on a tooth surface of the worm wheel. A shift mechanism for an automatic transmission, wherein the engagement with the worm wheel can be released against the urging force of the urging means.   The base portion has a wall portion formed in the vicinity of the worm gear, and a guide groove extending in a moving direction of the worm gear is formed in the wall portion, and a guide protrusion provided in the worm gear is formed in the guide groove. The shift mechanism for an automatic transmission according to claim 1, wherein the portions are movably engaged.

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