WO2010109786A1

WO2010109786A1 - Vehicle parking apparatus

Info

Publication number: WO2010109786A1
Application number: PCT/JP2010/001551
Authority: WO
Inventors: Eikichi Kidokoro; Naoki Itazu; Yoshinobu Nozaki
Original assignee: Aisin Aw Co., Ltd.; Toyota Jidosha Kabushiki Kaisha
Priority date: 2009-03-23
Filing date: 2010-03-05
Publication date: 2010-09-30

Abstract

A pivot lever connecting a parking rod and a hydraulic piston apparatus to each other is structured to be pivotable about a pivot shaft. The pivot shaft is fittingly inserted through a parking lock spring for biasing the parking rod to a parking pole side. The parking lock spring has a first end engaged with the pivot lever, and a second end fixed to a collar portion of a transmission case. A pivoting force of the pivot lever is applied to the first end of the parking lock spring, and a reaction force from the transmission case is applied to the second end thereof. Both ends of the parking lock spring are oriented so that the pivoting force of the pivot lever and the reaction force act in opposite directions to each other in a plane perpendicular to the pivot shaft.

Description

VEHICLE PARKING APPARATUS

The present invention relates to a vehicle parking apparatus that is mounted on, e.g., a vehicle having a shift-by-wire automatic transmission mounted thereon, and the like.

In multistage automatic transmissions that are mounted on vehicles such as automobiles, a transmission path in a speed change gear mechanism is typically determined by engagement and disengagement of clutches and brakes. The multistage automatic transmissions is provided with a hydraulic control apparatus for hydraulically controlling such engagement and disengagement of the clutches and the brakes by electronically controlled solenoid valves.

Such a hydraulic control apparatus is structured so that whether a range pressure is to be output or not is determined for each oil passage based on selection of a shift range such as a parking (P) range, a reverse (R) range, a neutral (N) range, or a drive (D) range by a shift lever provided near the driver's seat. When the shift lever is shifted to the P range, supply of a range pressure, which is a source pressure for each hydraulic servo, is stopped to bring the automatic transmission into a neutral state. Moreover, a parking pole, which operates together with the shift lever, is engaged with a parking gear fixed to an output shaft of the automatic transmission, thereby stopping rotation of the output shaft, and preventing rotation of wheels.

Hydraulic control apparatuses for setting a range pressure by a manual valve that mechanically operates together with a shift lever have been typically used in the related art. In recent years, hydraulic control apparatuses for setting a range pressure electrically (by a so-called shift-by-wire automatic transmission) by converting an operation of the shift lever into an electric command have been proposed in response to demands for increased flexibility in vehicle design, and the like.

Since the shift lever is not mechanically linked in such a shift-by-wire automatic transmission, a drive apparatus for controlling engagement and disengagement of a parking pole and a parking gear is required also for a parking apparatus. A parking apparatus that has been proposed includes a hydraulic actuator apparatus as a drive apparatus, and a compression spring, where the hydraulic actuator apparatus is provided at a rear end of a parking rod. The parking rod moves from an engaged position where a parking pole is engaged with a parking gear, to a disengaged position where the parking pole and the parking gear are disengaged from each other. The compression spring is provided between the back surface of a piston connected to the parking rod and a cylinder (see Japanese Patent Application Publication No. JP-A-2008-128444).

This parking apparatus is brought into a non-parking state by supplying an oil pressure into an oil chamber of the hydraulic actuator apparatus, and thus, moving the piston backward to move the parking rod to the disengaged position. The parking apparatus is brought into a parking state by discharging the oil pressure of the oil chamber, and thus, moving the cylinder forward by the biasing force of the compression spring to move the parking rod to the engaged position.

As shown in FIGS. 4A and 4B, the applicant has proposed a parking apparatus in which a drive apparatus that controls engagement and disengagement of a parking pole and a parking gear includes a torsion spring 19 that is used as a spring that biases the parking rod to the engaged position, a pivot lever 6 on which the torsion spring 19 is provided, and a hydraulic actuator apparatus. The hydraulic actuator apparatus and the parking rod are connected with each other via the pivot lever 6.

This torsion spring 19 is loosely fitted on a pivot shaft 17 of the pivot lever 6. One end 19a of the torsion spring 19 is attached to the pivot lever 6, and the other end 19b thereof is fixed to a groove 11a of a transmission case. As shown in FIG. 4B, one end 19a is attached to the pivot lever 6 so as to be twisted from a free position C in a no-load state to an attached position D.

Thus, one end 19a of the torsion spring 19 is subjected to a pivoting force i of the pivot lever 6 in the direction shown by arrows in FIGS. 4A and 4B. The other end 19b thereof is subjected to a reaction force ii corresponding to the pivoting force of the pivot lever 6, from a transmission case 11.

In the case where the forces respectively applied to both

ends

19a, 19b (the pivoting force of the lever and the reaction force) are decomposed in a plane perpendicular to the pivot shaft 17, and the respective components of the forces (the components perpendicular to the longitudinal direction of the spring) act in the same direction, bending moments do not cancel each other, deforming the torsion spring 19.

For example, as shown in FIG. 4A, when the respective vertical components of the forces that are respectively applied to both

ends

19a, 19b of the torsion spring 19 act downward, a moment A of the pivot lever 6 to tilt the spring, and a moment B to retain the spring are applied to the torsion spring 19, both inward toward the center of the torsion spring 19. As a result, the lower side of the spring is subjected to a compressive force, and the upper side thereof is subjected to a tensile force, whereby the spring is curved upward. Thus, the gap between the wires is increased in the upper side of the spring, and is reduced in the lower side of the spring. Due to the reduced gap between the wires, the wires contact each other in the lower side of the spring, thereby generating friction.

If the friction is generated between the wires, the frictional force causes so-called hysteresis h, as shown in FIG. 3. That is, the spring load is different between a twist side t and a return side r. Moreover, in order to obtain the spring load that is high enough to move the parking rod to the engaged position at the attached position D, the power that is required by the drive apparatus for pivoting the pivot lever 6 against the biasing force of the torsion spring 19 needs to be designed to be larger than that in the case where no such hysteresis is exhibited, by an amount corresponding to the hysteresis h.

Similarly, at a maximum use position E as well, where the twist angle of the torsion spring 19 becomes the largest, the power that is required by the drive apparatus needs to be increased by an amount corresponding to the difference m between a torsion spring t exhibiting hysteresis and a torsion spring n exhibiting no hysteresis. This reduces the power efficiency, and increases the size of the drive apparatus itself.

It is an object of the present invention to provide a parking apparatus in which both ends of a torsion spring are oriented so that the torsion spring exhibits no hysteresis.

A vehicle parking apparatus according to a first aspect of the present invention includes: a parking rod that moves in an axial direction from an engaged position where a parking gear and a parking pole are engaged with each other, to a disengaged position where the parking gear and the parking pole are disengaged from each other; a pivot lever coupled to the parking rod, for pivoting to set an axial position of the parking rod; a drive apparatus coupled to the pivot lever, for driving the pivot lever so that the pivot lever pivots based on a shift operation input; and a torsion spring that is disposed around a pivot shaft of the pivot lever, and has a first end engaged with the pivot lever, and a second end in contact with a fixed member, and biases the pivot lever toward a direction in which the parking rod moves to the engaged position by elastic deformation in a winding direction of the torsion spring, wherein both ends of the torsion spring are oriented so that a direction in which a force that is applied to the first end by driving of the drive apparatus, and a direction in which a reaction force is applied to the second end are opposite to each other in a plane direction perpendicular to the pivot shaft.

In the above structure, the drive apparatus may be formed by a hydraulic actuator.

A smallest inner diameter of the torsion spring when compressed by driving of the drive apparatus may be larger than an outer diameter of the pivot shaft.

According to the first aspect, the direction in which the force that is applied from the pivot lever to one end of the torsion spring, and the direction in which the reaction force is applied to the other end thereof are opposite to each other in the plane direction perpendicular to the pivot shaft. Thus, bending moments acting on the torsion spring cancel each other, whereby deformation of the torsion spring can be prevented. This prevents contact between the wires due to deformation of the torsion spring. Therefore, no frictional force is generated between the wires, whereby generation of hysteresis can be prevented. Therefore, the power for twisting the torsion spring by a predetermined torsion angle can be reduced by an amount corresponding to the hysteresis. As a result, the power for pivoting the pivot lever against the biasing force of the torsion spring can be reduced, whereby a compact, highly efficient drive apparatus can be implemented.

Since the drive apparatus is formed by the hydraulic actuator, the diameter of the hydraulic piston can be reduced.

Since the smallest inner diameter of the torsion spring when compressed is made larger than the outer diameter of the pivot shaft, excessive contact between the pivot shaft and the wires can be prevented, thereby preventing generation of a large amount of friction therebetween.

The features, advantages, and technical and industrial significance of this invention will be described in the following detailed description of example embodiments of the invention with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:
FIG. 1 is a side view of a parking apparatus according to an embodiment of the present invention; FIG. 2A is a front view of a potion where a torsion spring is attached according to the embodiment of the present invention, and FIG. 2B is a side view of FIG. 2A; FIG. 3 is a graph showing the relations between the spring load and the twist angle of the torsion spring in the case where the present invention is applied to the torsion spring and the present invention is not applied to the torsion spring; and FIG. 4A is a front view showing a portion where a torsion spring is attached, in which forces respectively applied to both ends of the torsion spring act in the same direction, in the case where the present invention is applied to the torsion spring, and FIG. 4B is a side view of FIG. 4A.

An embodiment of the present invention will be described below with reference to the accompanying drawings.

Overview of Parking Apparatus
As shown in FIG. 1, a parking apparatus 1 of a shift-by-wire automatic transmission is structured so that a parking pole 2 is engaged with a parking gear 23 attached to an output shaft of the automatic transmission, whereby the output shaft connected to driving wheels is fixed, thereby reliably stopping the vehicle. The parking apparatus 1 includes: the parking pole 2; a cam 3 for pivoting the parking pole 2 when contacting the back side of the parking pole 2, which is located on the side opposite to a pawl-shaped engaging portion 2a; a parking rod 5 having the cam 3 fitted on its tip end; and a hydraulic piston apparatus (a drive apparatus, a hydraulic actuator) 10 formed by a hydraulic piston 7 for moving the parking rod 5 via a pivot lever 6 to control engagement and disengagement of the parking pole 2 with and from the parking gear, a cylinder 9 of the hydraulic piston 7, and the like.

The parking pole 2 is structured so as to be pivotable vertically about a fulcrum shaft 12 attached to a transmission case 11. The parking pole 2 is always biased toward its back side by the biasing force of a spring 13 provided on the fulcrum shaft 12. A guide member 15 for supporting the tip end (the right side in FIG. 1) of the parking rod 5 is attached to the transmission case 11 by a bolt (not shown). The parking rod 5 is movable in a direction substantially parallel to the fulcrum shaft 12. The tip end of the parking rod 5 is slidably inserted into the tapered cam 3. Moreover, the parking rod 5 has a stopper 5a for a spring 16 in an intermediate portion thereof. The spring 16 is fittingly inserted between the stopper 5a and the cam 3. The cam 3 is biased toward the parking pole 2 by the biasing force of the spring 16, and is slidable up to a predetermined position on the parking rod 5.

On the other hand, the other end (the left end in FIG. 1) of the parking rod 5 is connected to the pivot lever 6, and the pivot lever 6 is supported by the transmission case 11 so as to be pivotable about a pivot shaft 17. The parking rod 5 is connected to an end of the pivot lever 6, and the opposite end of the pivot lever 6 is connected to the hydraulic piston 7. The pivot lever 6 is always biased toward the parking pole 2 by a parking lock spring 19 provided on the pivot shaft 17.

Thus, when the parking rod 5 is moved to the right in FIG. 1 to an engaged position where the parking gear and the parking pole 2 are engaged with each other, by the biasing force of the parking lock spring 19, the cam 3 is brought into contact with the back side of the parking pole 2. Thus, the parking pole 2 is pivoted against the biasing force of the spring 13, engaging the parking gear and the engaging portion 2a of the parking pole 2 with each other (a parking state). At this time, if the engaging portion 2a of the parking pole 2 contacts a tooth portion of the parking gear, and cannot be engaged with the parking gear, the spring 16 is compressed, and the parking apparatus waits for the parking state to be reached. When the vehicle moves slightly, and the parking gear is pivoted, the cam 3 is moved by the biasing force of the compressed spring 16 to contact the back side of the parking pole 2, whereby the parking pole 2 and the parking gear are engaged with each other.

With the parking pole 2 being engaged with the parking gear as described above, an oil pressure is supplied into

oil chambers

20, 21 to move the hydraulic piston 7 to the right in FIG. 1. Thus, the pivot lever 6 is rotated against the biasing force of the parking lock spring 19, and the parking rod 5 is moved to the left in FIG. 1 up to a disengaged position where the parking gear and the parking pole 2 are disengaged from each other, whereby the cam 3 is separated from the parking pole 2. As a result, the parking pole 2 is pivoted toward its back side by the biasing force of the spring 13, whereby the parking pole 2 is disengaged from the parking gear (a non-parking state).

Hydraulic Piston Apparatus
The hydraulic piston apparatus 10 as a hydraulic actuator will be described below. The hydraulic piston 7 has a shaft portion 7c, a first land portion 7a that radially extends from the shaft portion 7c so as to form a pressure-receiving area, and a second land portion 7b. A diameter of the first land portion 7a is smaller than a diameter of the second land portion 7b. The hydraulic piston 7 is fittingly inserted in the cylinder 9 that is formed by a hole formed in a valve body (or by a dedicated cylinder). The shaft portion 7c, located on the first land portion 7a side of the hydraulic piston 7, protrudes from the cylinder 9, and is connected to the pivot lever 6 described above. The two

oil chambers

20, 21 for operating the hydraulic piston 7 are formed by the inner peripheral surface of the cylinder 9 and the

land portions

7a, 7b of the hydraulic piston 7, respectively. An oil pressure is supplied into the

oil chambers

20, 21 via supply oil passages a1, a2, respectively.

When the cam 3 is in contact with the parking pole 2, and the parking apparatus is in the parking state, the hydraulic piston 7 is biased toward the left end of the cylinder 9 by the spring 16. When an oil pressure is supplied to the

oil chambers

20, 21 via the supply oil passages a1, a2, respectively, the hydraulic piston 7 is moved to the right in FIG. 1 by supply pressures respectively acting on the respective pressure-receiving areas of the two

land portions

7a, 7b.

When the hydraulic piston 7 is moved to the right in FIG. 1, and the cam 3 is separated from the parking pole 2, the oil chamber 21 for the second land portion 7b communicates with a drain hole a3, and the supply oil passage a2 is blocked by the first land portion 7a. Thus, the oil pressure in the oil chamber 21 is drained to an oil pan 22, and the position of the hydraulic piston 7 is retained by the supply pressure of the oil chamber 20 which is applied to the first land portion 7a.

Thus, in the parking state where a large moving force is required to separate the cam 3, pressed by the parking pole 2, from the parking pole 2, the sum of the oil pressure to the second land portion 7b and the oil pressure to the first land portion 7a is applied to the hydraulic piston 7. When the cam 3 is separated from the parking pole 2, and only a moving force (a small moving force) which is large enough to act against the biasing force of the parking lock spring 19 is required, the oil pressure is applied only to the first land portion 7a to retain the position of the hydraulic piston 7.

Note that the first land portion 7a described above is formed so that its pressure-receiving area on the oil chamber 20 side is larger than that on the oil chamber 21 side. Thus, a force in the right direction in FIG. 1 is always applied to the first land portion 7a. even if the oil pressure is supplied to both

oil chambers

20, 21.

Structure of Parking Lock Spring
The structure of the parking lock spring 19, which is a main part of the present invention, will be described in detail below. As shown in FIGS. 2A and 2B, the parking lock spring 19 is a torsion spring having a plurality of windings formed at a predetermined pitch s so that the wires do not contact each other. The pivot shaft 17 of the pivot lever 6 described above is inserted through the parking lock spring 19. The inner diameter f of the parking lock spring 19 is determined as appropriate such that the smallest inner diameter of the parking lock spring 19 is larger than the outer diameter e of the pivot shaft 17, and that the parking lock spring 19 is not tilted too much when compressed. The smallest inner diameter of the parking lock spring 19 mentioned above is the inner diameter of the parking lock spring 19 which is obtained when the hydraulic piston 7 is moved until the pivot lever 6 is pivoted to a maximum use position E as shown in FIG. 2B, and the parking lock spring 19 is compressed.

One end 19a of the parking lock spring 19 is engaged with a hole formed in an attachment portion 6a of the pivot lever 6, and the other end 19b thereof is fixed to a collar portion (a fixed member) 11b of the transmission case 11. One end 19a of the parking lock spring 19 is attached so as to be elastically deformed in a winding direction (toward the twist side) from a free position C in a no-load state to an attached position D. The pivot lever 6 is biased toward the parking pole 2 (clockwise in FIG. 1) with a spring load g (see FIG. 3) that is high enough for the cam 3 to push the parking pole 2 up.

Since one end 19a of the parking lock spring 19 is elastically deformed from the free position C to the attached position D, one end 19a of the parking lock spring 19 is subjected to a pivoting force i from the pivot lever 6 in the direction shown by arrow A in FIG. 2A, and the other end 19b thereof is subjected to a reaction force ii corresponding to the pivoting force i of the pivot lever 6, from the collar portion 11b of the transmission case 11.

Both ends of the parking lock spring 19 are oriented so that the direction in which the pivoting force i of the pivot lever 6 is applied to one end 19a, and the direction in which the reaction force ii is applied to the other end 19b (the reaction force direction) are opposite to each other (such directions that the pivoting force i and the reaction force ii cancel each other) in a plane perpendicular to the pivot shaft 17 (in a plane direction). Both ends of the parking lock spring 19 are attached so that bending moments A, B, which are generated in the parking lock spring 19, act in such directions that the bending moments A, B cancel each other.

That is, as shown in FIG. 2B, in the case where the pivoting force i of the pivot lever 6, and the reactive force ii are decomposed in the plane perpendicular to the pivot shaft 17, the vertical and lateral components of the pivoting force i and the vertical and lateral components of the reactive force ii in the figure act in such directions (opposite directions) that the respective vertical components and the respective lateral components cancel each other.

Thus, unlike the parking lock spring of FIGS. 4A and 4B described above, a moment A of the vertical component of the pivoting force i of the pivot lever 6 to tilt the parking lock spring 19, and a moment B of the vertical component of the reaction force ii to retain the parking lock spring 19 cancel each other, as shown in FIG. 2A. Thus, the parking lock spring 19 is hardly deformed by the bending moments, and the pitch s between the wires is maintained, whereby no friction is generated between the wires.

FIG. 3 is a diagram showing the relation between the spring load and the twist angle, and "n," which indicates the spring load of the parking lock spring 19, follows the same path both on the twist side and the return side. It can be seen from FIG. 3 that the parking lock spring 19 exhibits no hysteresis h, as compared to the torsion spring of FIG. 4 in which friction is generated between the wires.

Functions
Functions of the parking apparatus 1 according to the present invention described above will be described below. When the shift range is shifted from the P range to a non-P range, an oil pressure is supplied to the

oil chambers

20, 21 of the hydraulic piston apparatus 10, and the hydraulic piston 7 is moved to the right in FIG. 1. Thus, the parking rod 5 is moved from the engaged position (a right position in FIG. 1) to the disengaged position (a left position in FIG. 1) via the pivot lever 6, and the cam 3 is separated from the parking pole 2, whereby the parking state is released.

At this time, since the pivot lever 6 is pivoted, the parking lock spring 19 is elastically deformed in the winding direction from the attached position D to the maximum use position E. Thus, one end 19a of the parking lock spring 19 is subjected to the pivoting force i from the pivot lever 6, and the other end 19b thereof is subjected to a reaction force ii corresponding to the pivoting force i.

The pivoting force i and the reaction force ii, which are respectively applied to both

ends

19a, 19b of the parking lock spring 19, act in such directions that both forces cancel each other in a plane perpendicular to the pivot shaft 17. Moreover, bending moments A, B, which are respectively caused by the pivoting force i and the reaction force ii, cancel each other. Thus, the parking lock spring 19 is reduced in diameter with no deformation (no curving), while substantially maintaining the predetermined pitch s between the wires.

Thus, the parking lock spring 19 can be structured so as to exhibit no hysteresis h as shown by "n" in FIG. 3. As compared with the spring exhibiting the hysteresis h, the highest spring load (in a non-parking state) can be reduced while ensuring the load for moving the parking rod 5 to the engaged position (see "m" in FIG. 3).

Since the highest spring load of the parking lock spring 19 is reduced, the cylinder (hydraulic piston) diameter of the hydraulic piston apparatus 10 can be reduced. This enables the entire apparatus to be formed in a compact form, and also reduces a required oil pressure, whereby the power efficiency is improved.

Moreover, since the parking lock spring 19 has the predetermined pitch s between the wires, and the smallest inner diameter f of the parking lock spring 19 when compressed is larger than the outer diameter e of the pivot shaft 17, the friction, which is generated between the wires and between the wires and the pivot shaft, can be minimized.

Furthermore, one end of the pivot lever 6 is connected with the parking rod 5 and the other end of the pivot lever 6 is connected with the hydraulic piston 7. Since a distance between a center of the pivot shaft 17 and one end of the pivot lever 6 is smaller than a distance between the center of the pivot shaft 17 and the other end of the pivot lever 6, the power that is required by the hydraulic piston 7 for moving the parking rod 5 can be reduced.

Claims

A vehicle parking apparatus, characterized by comprising:
a parking rod that moves in an axial direction from an engaged position where a parking gear and a parking pole are engaged with each other, to a disengaged position where the parking gear and the parking pole are disengaged from each other;
a pivot lever coupled to the parking rod, for pivoting to set an axial position of the parking rod;
a drive apparatus coupled to the pivot lever, for driving the pivot lever so that the pivot lever pivots based on a shift operation input; and
a torsion spring that is disposed around a pivot shaft of the pivot lever, and has a first end engaged with the pivot lever, and a second end in contact with a fixed member, and biases the pivot lever toward a direction in which the parking rod moves to the engaged position by elastic deformation in a winding direction of the torsion spring, wherein
both ends of the torsion spring are oriented so that a direction in which a force that is applied to the first end by driving of the drive apparatus, and a direction in which a reaction force is applied to the second end are opposite to each other in a plane direction perpendicular to the pivot shaft.
The vehicle parking apparatus according to claim 1, wherein
the both ends of the torsion spring are oriented so that, in the case where the force applied to the first end and the reaction force applied to the second end are decomposed in the plane perpendicular to the pivot shaft, the vertical and lateral components of the force applied to the first end and the vertical and lateral components of the reaction force act in such directions that the respective vertical components and the respective lateral components cancel each other.
The vehicle parking apparatus according to claim 1 or 2, wherein
the drive apparatus is formed by a hydraulic actuator.
The vehicle parking apparatus according to any one of claims 1 to 3, wherein
a smallest inner diameter of the torsion spring when compressed by driving of the drive apparatus is larger than an outer diameter of the pivot shaft.
The vehicle parking apparatus according to any one of claims 1 to 4, wherein
the torsion spring has a predetermined pitch between the wires.
The vehicle parking apparatus according to any one of claims 1 to 5, wherein:
a first end of the pivot lever is connected with the parking rod;
a second end of the pivot lever is connected the drive apparatus; and
a distance between a center of the pivot shaft of the pivot lever and the first end of the pivot lever is smaller than a distance between the center of the pivot shaft and the second end of the pivot lever.