JP2007303532A - Automatic transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic transmission capable of canceling load of a return spring. <P>SOLUTION: This automatic transmission 1 is provided with: a first member 10 and a second member 20 which are mutually connected or are separated from each other, rotate by opposing to each other, and are provided in an ATF 100; a piston 40 to which first and second oil pressure is given and which can connect either of the first and second members 10, 20 with the other of them or separate them from each other by moving in first and second directions in accordance with balance between the first and second oil pressure; the return spring 22 for energizing the piston 40 in either of the first and second directions; and a shape memory spring 42 energizing the piston 40 in the opposite direction to the direction of the return spring 22, provided in the ATF 100, and including a shape memory material. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an automatic transmission, and more particularly to an automatic transmission using a friction engagement element.

Conventionally, the friction member is disclosed in Japanese Patent Laid-Open No. 2003-247564 (Patent Document 1).
JP 2003-247564 A

  In Patent Document 1, the clutch piston includes a return spring that urges the clutch piston in a first direction and a second direction opposite to the first direction, and at least a part of the folded portion in which a part of the clutch plate is folded back to the clutch piston side. A technique of forming a cushion spring from a shape memory alloy is disclosed.

  In the conventional automatic transmission, it is necessary to increase the load of the return spring in order to prevent dragging (piston return compensation) during cold (low oil temperature, that is, high viscosity of ATF (automatic transmission fluid)). there were. When the load of the return spring increases, the pressing force due to the hydraulic pressure of the piston is canceled by the return spring, and the torque capacity becomes insufficient. As a result, it is necessary to increase the number of friction materials. This causes an increase in cost, weight, and physique. In addition, there is a problem in that the required oil pressure needs to be increased, and the fuel consumption deteriorates.

  Accordingly, the present invention has been made to solve the above-described problems, and an object thereof is to provide an automatic transmission that can be reduced in size and that can operate at a low hydraulic pressure. .

  The automatic transmission according to the present invention is connected or disconnected from each other, rotates relative to each other, is provided with first and second members provided in oil, and first and second hydraulic pressures are provided. A pressing member capable of connecting or disconnecting one of the first and second members to the other by moving in the first and second directions according to the balance of the two hydraulic pressures; A first urging member that urges in one of the first and second directions; and a second urging member that urges the pressing member in a direction opposite to the first urging member and includes a shape memory substance. .

  In the automatic transmission configured as described above, since the second urging member includes the shape memory substance, the shape of the shape memory substance changes according to the oil temperature. Thereby, the second urging member can generate the urging force according to the oil temperature, the first member and the second member are separated at a low oil temperature, and the first member and the second member at a high oil temperature. Can be contacted. As a result, it is possible to generate a frictional force according to the oil temperature that can be reduced in size and can be operated at a low oil pressure.

Preferably, the plurality of second urging members press the pressing member.
Preferably, the second biasing member has a first natural length at the first temperature and a second natural length longer than the first natural length at a second temperature higher than the first temperature. .

  Preferably, the second biasing member has a first spring constant at a first temperature and a second spring constant greater than the first spring constant at a second temperature higher than the first temperature. .

  Preferably, the second urging member is provided in oil.

  According to this invention, it is possible to provide an automatic transmission that can be miniaturized and that can be operated at a low hydraulic pressure.

  Embodiments of the present invention will be described below with reference to the drawings. In the following embodiments, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

(Embodiment 1)
1 is a cross-sectional view of a part of an automatic transmission according to Embodiment 1 of the present invention. Referring to FIG. 1, in automatic transmission 1, first member 10 is located on the outer periphery of shaft 60, and first member 10 is held rotatably with respect to shaft 60. A disc-shaped engagement member 11 is provided on the outer periphery of the first member 10 and is disposed so as to be able to contact a friction member 21 as a counterpart material. The plurality of engaging members 11 are lubricated and cooled by the ATF 100. The first member 10 exists in the ATF 100.

  The second member 20 is attached to the shaft 60, and the second member 20 rotates together with the shaft 60. The second member 20 includes a plurality of friction members 21 as contact members, and each friction member 21 can contact and separate from the engagement member 11. Thereby, the rotation of the first member 10 is transmitted to the second member 20, and the rotation of the first member 10 is not transmitted to the second member 20. That is, when the engagement member 11 and the friction member 21 are in contact, the rotation of the first member 10 is transmitted to the second member 20. On the other hand, when the engagement member 11 and the friction member 21 are not in contact, the rotation of the first member 10 is not transmitted to the second member 20. The second member 20 is lubricated with ATF 100 and cooled.

  A part of the second member 20 is pressed in the axial direction by the disk member 23. By receiving the pressing force, the second member 20 slides and moves in the axial direction, and the friction member 21 constituting the second member 20 comes into contact with the engaging member 11. The disk member 23 has a disk shape, and one end thereof is pressed by a return spring 22. For this reason, in the state shown in FIG. 1, the disk member 23 is pushed back by the return spring 22, and the friction member 21 and the engagement member 11 are not in contact with each other. Therefore, in the state shown in FIG. 1, the rotation of the first member 10 is not transmitted to the second member 20.

  The load (spring constant) of the return spring 22 is sufficient to push the disk member 23 back. The larger the load (spring constant) of the return spring 22 is, the more reliably the friction member 21 can be separated from the engagement member 11, and the friction member when the so-called friction member 21 and the engagement member 11 are not in contact with each other. It is possible to prevent so-called dragging, in which 21 and the engaging member 11 come into contact.

  The contact between the friction member 21 and the engagement member 11 and the power transmission between them depend not only on the contact area and the contact pressure but also on the oil temperature of the ATF 100. The viscosity of ATF 100 decreases with increasing oil temperature and increases with decreasing oil temperature. If the viscosity is large, even if there is a slight gap between the friction member 21 and the engagement member 11, the high-viscosity ATF 100 exists in the gap, so the friction member 21 and the engagement member 11 are connected via the ATF 100. Rotate in conjunction with each other. This can also cause so-called dragging.

  The piston 40 is annular and is accommodated in the cylinder 30. The piston 40 is provided so as to be able to slide and move in a first direction indicated by an arrow 101 and a second direction indicated by an arrow 102. A seal member 41 is provided on the outer periphery of the piston 40 in a ring shape, and the seal member 41 can prevent ATF from leaking.

  A first hydraulic chamber 110 and a second hydraulic chamber 120 are provided on opposite sides of the piston 40, respectively. When there is a difference between the hydraulic pressures of the first hydraulic chamber 110 and the second hydraulic chamber 120, the piston 40 moves. Since this movement is transmitted to the friction member 21 through the disk member 23, the friction member 21 also moves in the axial direction as the piston 40 moves. Thereby, the friction member 21 and the engagement member 11 can be contacted and disconnected. The first hydraulic chamber 110 and the second hydraulic chamber 120 are performed by an oil control valve that constitutes a part of the automatic transmission. That is, the first hydraulic chamber 110 and the second hydraulic chamber 120 are each connected to an oil control valve, and by adjusting the hydraulic pressure of the first hydraulic chamber 110 and the second hydraulic chamber 120 with the oil control valve, the piston 40 is moved. It is possible to move in the direction indicated by the arrow 101 or the direction indicated by the arrow 102.

In order to prevent the flow of hydraulic pressure between the first hydraulic chamber 110 and the second hydraulic chamber 120, a seal member 41 is provided. As a result, the hydraulic pressure in the first hydraulic chamber 110 and the second hydraulic chamber 120 can be controlled independently. A shape memory spring 42 made of a shape memory alloy is provided in the first hydraulic chamber 110. The shape memory spring 42 can be made of not only an alloy but also a shape memory material capable of storing a shape. Specifically, in the case of using an alloy, it is possible to use an alloy that undergoes reversible martensitic transformation and that exhibits superelasticity and shape memory effect with martensitic transformation and its reverse transformation. . As the alloy having such a behavior, (CuNI) ₃ Al, AuCd, In—Ti, CuAuZn, CuZn, TiNiAl, Ag, Cd, Fe ₃ Pt, or the like can be used.

  Further, a shape memory resin can be used instead of the shape memory alloy. It is also possible to replace the shape memory alloy with a shape memory fiber.

  The shape memory spring 42 presses the piston 40 in the direction indicated by the arrow 102. In contrast, the return spring 22 biases the piston 40 in the direction indicated by the arrow 101. That is, the urging directions of the return spring 22 and the shape memory spring 42 are opposite. The shape memory spring 42 changes its natural length or spring constant according to the temperature (oil temperature) of the ATF 100. That is, when the temperature is low, the natural length is short or the spring constant is small. On the other hand, if the oil temperature rises, the temperature of the shape memory spring 42 also rises, thereby increasing the spring constant or increasing the natural length. Therefore, the higher the temperature, the stronger the force that urges the piston 40 in the direction indicated by the arrow 102.

  When the temperature of the ATF 100 is low, the viscosity of the ATF 100 is high. Therefore, it is necessary to reliably separate the friction member 21 and the engagement member 11. For this reason, the spring constant of the shape memory spring 42 is reduced or the natural length of the shape memory spring 42 is shortened so that the urging force by the return spring 22 is larger than the urging force by the shape memory spring 42. As a result, the piston 40 is pushed in the direction indicated by the arrow 101. Therefore, it is possible to prevent the disk member 23 from pressing the friction member 21 and to reliably separate the friction member 21 from the engagement member 11. As a result, drag can be prevented.

  On the other hand, when the temperature of the ATF 100 increases, the spring constant of the shape memory spring 42 increases or the natural length of the shape memory spring 42 increases. As a result, the force by which the shape memory spring 42 urges the piston 40 in the direction indicated by the arrow 102 increases. Therefore, the friction member 21 is reliably pressed against the engagement member 11, and power can be reliably transmitted between the friction member 21 and the engagement member 11.

  FIG. 2 is a front view of the automatic transmission as viewed from the direction indicated by arrow II in FIG. Referring to FIG. 2, three shape memory springs 42 are provided for one piston 40. The three shape memory springs 42 are arranged at equal intervals on the same circumference with respect to the center. Although three shape memory springs 42 are shown in FIG. 2, the present invention is not limited to this, and more or fewer shape memory springs 42 may be arranged.

  In addition, a plurality of shape memory springs 42 are arranged at positions where the distance from the center of the disk is equal, but also in this respect, a plurality of shape memory springs 42 are provided at positions where the distance from the center is unequal. May be. In addition, the distance between the shape memory springs 42 may or may not be constant.

  Since a plurality of shape memory springs 42 are arranged, even if the characteristics of the shape memory springs 42 vary, they are averaged.

  An automatic transmission according to the present invention is provided between a power source and wheels, and is used as a device for converting the rotational speed and rotational torque. The input and output shafts of the automatic transmission may extend parallel to the traveling direction of the vehicle, or may extend so as to be orthogonal to the traveling direction of the vehicle.

  The shift stage of the automatic transmission can be set as various stages of two stages or more. Moreover, an engine or a motor can be employed as a power source connected to the automatic transmission. Further, in the case of an engine, it may be either a gasoline engine or a diesel engine, or a reciprocating type engine or a rotary type engine. Further, in the case of an engine having a plurality of cylinders, the automatic transmission can be connected to engines of various shapes such as a series type, a parallel type, a horizontally opposed type, a V type and a W type.

  FIG. 3 is a graph showing the relationship between the temperature of the shape memory alloy and the spring constant. FIG. 4 is a graph showing the relationship between the temperature and the natural length of the shape memory alloy. Referring to FIG. 3, a shape memory alloy constituting the shape memory spring according to the present invention may be one whose spring constant increases as the temperature rises. That is, while the spring constant is k1 at the low temperature T1, the spring constant is k2 larger than k1 at the high temperature T2. That is, if the displacement of the spring is the same, the force (biasing force) exerted by the spring increases as the temperature increases.

  Referring to FIG. 4, the shape memory alloy constituting the shape memory spring according to the present invention has a natural length L1 at a low temperature T1 and may have a long natural length L2 at a high temperature T2. . L2 is greater than L1. Note that the shape memory alloy used in the shape memory spring according to the present invention does not have to have both of the characteristics shown in FIGS. 3 and 4, and has at least one of the characteristics shown in FIGS. Just do it.

  Since the shape memory spring 42 exists in the first hydraulic chamber 110, it is immersed in the ATF 100 as oil. Therefore, the temperature of the ATF 100 becomes the temperature of the shape memory spring 42, and the temperature of the shape memory spring 42 also changes according to the temperature of the ATF 100 interposed between the friction member 21 and the engagement member 11.

  FIG. 5 is a partial cross-sectional view of the automatic transmission shown to explain the friction member and the engagement member that are in contact with each other. Referring to FIG. 5, when the hydraulic pressure in the first hydraulic chamber 110 becomes larger than the hydraulic pressure in the second hydraulic chamber 120 and the difference between the hydraulic pressures becomes larger than the urging force by the return spring 22, the piston 40 moves to the arrow 102. Move in the direction indicated by. At this time, the disk member 23 that comes into contact with the piston 40 also moves in the direction indicated by the arrow 102, contacts the friction member 21, and presses the friction member 21 in the direction indicated by the arrow 102. Accordingly, each of the friction members 21 comes into contact with the engagement member 11, and the rotation of the friction member 21 is transmitted to the engagement member 11. Thereby, both the 1st member 10 and the 2nd member 20 come to rotate.

  In this embodiment, the shape memory spring 42 urges the piston 40 in a direction in which the friction member 21 and the engagement member 11 are brought into contact with each other, but conversely, the shape memory spring is used by using the shape memory spring on the return spring side. However, the friction member 21 and the engagement member 11 may be urged in a direction separating them.

  That is, the shape memory spring 42 may be used to connect the friction member 21 and the engagement member 11, and the shape memory spring 42 may be used to separate the friction member 21 and the engagement member 11.

  Components such as the piston 40 are accommodated in the casing 51, and the piston 40, the first member 10, and the second member 20 are disposed in the liquid-tight space.

  FIG. 6 is a partial cross-sectional view of an automatic transmission according to a comparative example. Referring to FIG. 6, automatic transmission 1 according to the comparative example differs from automatic transmission 1 according to the first embodiment in that shape memory spring 42 that presses piston 40 is not provided. As described above, when the shape memory spring is not provided, it is necessary to increase the load of the return spring 22 in order to prevent dragging in the cold state. When the load of the return spring 22 increases, the pressing force due to the hydraulic pressure of the piston 40 is canceled by the return spring 22 and the torque capacity becomes insufficient, increasing the number of friction materials or increasing the hydraulic pressure. As a result, the cost weight and the physique increase, and the deterioration of fuel consumption becomes a problem. In the present invention, the shape memory spring 42 is set in the chamber chamber of the clutch or brake piston, and when the temperature rises above a predetermined temperature, the shape is restored and a desired spring load is generated. That is, by generating a load opposite to the return spring 22 at the normal temperature (above a predetermined temperature) by the shape memory spring 42, a part of the load of the return spring 22 is canceled, the number of friction materials is increased, and the hydraulic pressure is increased. The torque capacity can be secured without achieving the above.

  When there is a problem due to a small piston pressing force during cold, torque down control is used together.

  The automatic transmission 1 according to the present invention is connected or disconnected from each other, rotates relative to each other, is provided with a first member 10 and a second member 20 provided in the ATF 100, and first and second hydraulic pressures. One of the first member 10 and the second member 20 is connected to the other by moving in the first direction indicated by the arrow 101 and the second direction indicated by the arrow 102 in accordance with the balance between the first and second hydraulic pressures. Or a piston 40 as a pressing member that can be separated, a return spring 22 as a first biasing member that biases the piston 40 in either the first or second direction, and a return spring 22. The piston 40 is urged in the opposite direction, and is provided in the ATF 100 and includes a shape memory spring 42 as a second urging member containing a shape memory substance. A plurality of shape memory springs 42 press the piston 40. The shape memory spring 42 has a first natural length at a first temperature and a second natural length that is longer than the first natural length at a second temperature higher than the first temperature. The shape memory spring 42 has a first spring constant at the first temperature, and a second spring constant larger than the first spring constant at a second temperature higher than the first temperature.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 is a cross-sectional view of a part of an automatic transmission according to Embodiment 1 of the present invention. It is a front view of the automatic transmission seen from the direction shown by the arrow II in FIG. It is a graph which shows the relationship between the temperature of a shape memory alloy, and a spring constant. It is a graph which shows the relationship between the temperature of a shape memory alloy, and natural length. It is a partial cross section figure of an automatic transmission shown in order to demonstrate the friction member and engagement member which mutually contact. It is a partial cross section figure of the automatic transmission according to a comparative example.

Explanation of symbols

  1 automatic transmission, 10 first member, 11 engaging member, 20 second member, 21 friction member, 22 return spring, 23 disk member, 30 cylinder, 40 piston, 41 seal member, 42 shape memory spring, 60 shaft, 100 ATF, 110 first hydraulic chamber, 120 second hydraulic chamber.

Claims (5)

First and second members connected or disconnected from each other, rotating relative to each other and provided in oil;
First and second hydraulic pressures are applied, and one of the first and second members is connected to the other by moving in the first and second directions according to the balance between the first and second hydraulic pressures. Or a pressing member that can be separated;
A first biasing member that biases the pressing member in either one of the first and second directions;
An automatic transmission comprising: a second biasing member that biases the pressing member in a direction opposite to the first biasing member and includes a shape memory substance.   The automatic transmission according to claim 1, wherein a plurality of the second urging members press the pressing member.   The second biasing member has a first natural length at a first temperature, and has a second natural length that is longer than the first natural length at a second temperature higher than the first temperature. The automatic transmission according to claim 1 or 2.   The second biasing member has a first spring constant at the first temperature and a second spring constant greater than the first spring constant at a second temperature higher than the first temperature. The automatic transmission according to claim 1 or 2.   The automatic transmission according to claim 1, wherein the second urging member is provided in oil.

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