JP2014149060A - Gear change control device of belt-type continuously variable transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress an increase of a power loss caused by the continuation of thrust which is increased for making a belt return favorable.SOLUTION: A gear change control device of a belt-type continuously variable transmission comprises: thrust auxiliary means for generating auxiliary thrust added to thrust which presses a variable sheave to an axial direction; lock means capable of locking the thrust auxiliary means so that the auxiliary thrust does not act on the variable sheave when a gear change ratio is smaller than a preset prescribed gear change ratio, and releasing the lock of the thrust auxiliary means so that the auxiliary thrust acts on the variable sheave when a preset prescribed condition is established; and gear change condition change means (step S3) for changing the gear change condition so as to facilitate the switch of the gear change ratio to the prescribed gear change ratio when the gear change ratio is larger than the prescribed gear change ratio after the lock of the thrust auxiliary means is released.

Description

  The present invention relates to an apparatus for controlling a gear ratio of a belt type continuously variable transmission, and in particular, by changing a groove width of a pulley around which a belt is wound, a belt winding radius, that is, a gear ratio is continuously changed. The present invention relates to an apparatus for controlling a gear ratio in a belt-type continuously variable transmission.

  In this type of belt-type continuously variable transmission, the pulley is fixed so that the belt winding radius changes according to the change in the width of the belt groove around which the belt is wound (hereinafter simply referred to as the groove width). The sheave is constituted by a movable sheave that approaches and moves away from the fixed sheave. Since the surfaces of these sheaves facing each other are formed in a taper shape, a radially outward load acts on the belt in accordance with the belt clamping pressure for clamping the belt between the sheaves. It is in tension. Therefore, if the thrust force that pushes the movable sheave in one pulley toward the fixed sheave side is increased, the belt is pushed outward in the radial direction to increase the winding radius, and the groove width is expanded in the other pulley. As a result, the belt winding radius decreases.

  In this way, the belt is sandwiched between pulleys, and a frictional force is generated at the contact portion between the two, and torque is transmitted by the frictional force. Since the frictional force is a large frictional force according to the torque to be transmitted, changing the groove width of one pulley while the pulley is rotating and the belt is running causes the belt to move outward in the radial direction of the pulley. Or it moves relatively inside and the winding radius changes. However, in the state where the rotation of the pulley is stopped, the frictional force between the pulley and the belt is large as described above, so the belt cannot be slid inside the belt groove and the gear ratio is changed. I can't.

  On the other hand, in a belt type continuously variable transmission mounted on a vehicle, it is necessary to set a small gear ratio during steady running and to set a large gear ratio during start-up and acceleration. Therefore, when a vehicle that is traveling steadily stops, the gear ratio is changed to a large gear ratio in preparation for re-starting after the vehicle stops. In that case, if the braking toward the stop is sudden braking, it is necessary to rapidly increase (downshift) the gear ratio. This is because it is difficult or impossible to change the gear ratio after the vehicle stops.

  The operation to increase the gear ratio of a belt type continuously variable transmission is to widen the groove width of the pulley on the driving side to reduce the belt winding radius and to narrow the groove width of the pulley on the driven side to wind the belt. This is done by increasing the multiplying radius. Since tension is applied to the belt, a load is applied to each pulley so as to widen the groove width. Therefore, by moving the movable sheave in the pulley on the driving side away from the fixed sheave, the groove width is increased. Becomes wider. On the other hand, the movable sheave in the driven pulley requires a large thrust because it is necessary to move the belt toward the fixed sheave so as to move the belt outward in the radial direction. In particular, when the gear ratio is rapidly increased with sudden braking, a large thrust is required.

  On the other hand, since the thrust for pressing the movable sheave toward the fixed sheave becomes the belt clamping pressure, the belt clamping pressure increases as the thrust increases. However, if the belt clamping pressure is constantly increased, the frictional force between the belt and the pulley becomes excessive with respect to the torque to be transmitted, so that the power loss is caused by excessive friction between the belt and the pulley. May increase. Since the belt type continuously variable transmission has the advantage of improving the fuel efficiency of the vehicle, if the power loss increases due to excessive friction, the original advantage of the belt type continuously variable transmission is diminished. Therefore, conventionally, the belt clamping pressure is generally set to a pressure corresponding to the torque to be transmitted, and means for rapidly increasing the gear ratio in preparation for re-start in the case of sudden braking is a normal method. It is provided separately from the mechanism that sets the thrust.

  For example, in Patent Document 1, in order to reliably perform restart after sudden braking, the movable flange that constitutes the primary sheave is moved by a motor to change the groove width, and the secondary sheave is also constituted. A belt type continuously variable transmission is described in which a movable flange is pressed against a fixed flange by a spring and a torque cam. In the belt-type continuously variable transmission described in Patent Document 1, the sheave is idled even when the driving wheel is stopped, and in that state, the groove width of the primary sheave is widened by the motor to restart the sheave. Set the gear ratio for. Therefore, in the configuration described in Patent Document 1, the groove width of the primary sheave can be widened by the motor. However, in the secondary sheave, the movable sheave is pressed in the axial direction by a torque cam or a spring to narrow the groove width. The belt winding radius is increased.

JP 2007-232147 A

  The continuously variable transmission described in the above-mentioned Patent Document 1 does not execute control for rapidly narrowing the groove width of the secondary sheave when sudden braking is performed, and the pulley is idled after the vehicle stops and the gear ratio is reset. It is comprised so that it may change to the gear ratio prepared for the start. In that case, the groove width of the secondary sheave is narrowed by a thrust generated by an existing spring or torque cam. Therefore, the thrust for increasing the belt winding radius in the secondary sheave is not necessarily large enough, and it may take time for the belt winding radius to change so as to set the start gear ratio. There is sex. Further, since the belt-type continuously variable transmission described in Patent Document 1 is based on the premise that the sheave is idling, it is like a belt-type continuously variable transmission mounted on a four-wheeled vehicle such as a light vehicle or a normal vehicle. In addition, the technique described in Patent Document 1 cannot be applied to a belt-type continuously variable transmission configured such that the pulley does not rotate when the vehicle is stopped.

  In order to quickly narrow the groove width so as to set the gear ratio for starting, the thrust force that presses the movable sheave toward the fixed sheave may be increased. However, as described above, the movable sheave is moved toward the fixed sheave. If the thrust force to be pressed is large, the clamping pressure with which the pulley pinches the belt increases, and the frictional force between the belt and the pulley increases. If the frictional force is excessively larger than the torque to be transmitted, there is a disadvantage that the power transmission efficiency is lowered.

  The present invention has been made paying attention to the above technical problem, and when it is necessary to rapidly increase the belt wrapping radius, the thrust is increased, and the necessary state of the thrust increase is eliminated. An object of the present invention is to provide a speed change control device capable of quickly returning the increased thrust.

  To achieve the above object, the invention of claim 1 has at least a pair of pulleys around which a belt is wound, and each pulley approaches and separates from each other to increase or decrease the width of a groove around which the belt is wound. It is composed of a pair of sheaves that change the ratio, and the thrust in the direction in which the sheaves in the driven pulley approach each other acts on the sheaves in the driven pulley so as to narrow the width of the groove in the driven pulley. In a shift control device for a belt-type continuously variable transmission that includes a thrust mechanism and is configured to set a gear ratio according to a predetermined shift condition when a predetermined shift condition is established, an auxiliary that is added to the thrust Thrust assisting means for generating thrust, and when the gear ratio is smaller than a predetermined gear ratio, the auxiliary thrust is applied to the sheave in the driven pulley. The thrust assisting means can be locked so that the thrust assisting means is not locked, and the thrust assisting means is unlocked so that the assist thrust acts on the sheave in the driven pulley when a predetermined condition is satisfied. And the shift means so that the gear ratio is easily switched to the predetermined gear ratio when the gear ratio is larger than the predetermined gear ratio after the thrust assisting means is unlocked by the lock means. A shift condition changing means for changing the condition is provided.

  According to a second aspect of the invention, in the first aspect of the invention, the belt type continuously variable transmission is mounted on a vehicle having an internal combustion engine as a driving force source, and the speed change condition determines a target rotational speed of the internal combustion engine. The speed change condition changing means includes a means for changing a vehicle speed for determining a predetermined target rotational speed to a value smaller than a normal speed change control, and an accelerator opening for determining the predetermined target rotational speed as a normal speed. A shift control device for a belt-type continuously variable transmission, comprising at least one of means for changing to a value larger than the shift control.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the sheave is fitted to the rotary shaft so as to approach and separate from the fixed sheave integrated with the rotary shaft. And a movable sheave that moves back and forth in the axial direction of the rotating shaft, and the thrust assisting means includes a spring that presses the movable sheave toward the fixed sheave. A shift control device.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the predetermined condition includes a sudden deceleration state in which the number of rotations of the pulley rapidly decreases. A transmission control device for a continuously variable transmission.

  According to the present invention, when a predetermined condition such as a sudden deceleration state is established, the thrust assisting means is unlocked, and the assisting thrust is added to the thrust acting to narrow the width of the driven pulley groove. It is done. As a result, the total thrust for narrowing the groove width of the pulley on the driven side is increased, so that the groove width of the pulley is rapidly narrowed and the belt winding radius is increased. That is, the gear ratio can be increased rapidly. Therefore, in the vehicle, a so-called belt return when the vehicle is suddenly decelerated and stopped can be generated satisfactorily or reliably, and a situation where the driving force is insufficient at the time of restart can be avoided.

  After the total thrust is increased in this way, when the gear ratio is large, that is, when the distance between the sheaves of the driven pulley (groove width) is smaller than the interval for setting the predetermined gear ratio, the gear ratio becomes small. The speed change condition is changed so that it is easy. That is, the speed change condition is changed so that a state where the auxiliary thrust means can be locked by the lock means is likely to occur. As a result, the state in which the total thrust is increased due to the addition of auxiliary thrust is eliminated early, so the period during which the frictional force between the belt and pulley is excessive is shortened, and power loss is prevented or suppressed. can do.

It is a flowchart for demonstrating an example of the control performed with the transmission control apparatus which concerns on this invention. It is a figure which shows the shift map used by normal shift control, and the shift map which made it easy to set a predetermined reference gear ratio. It is a schematic diagram which shows an example of the belt-type continuously variable transmission made into object by this invention. It is a fragmentary sectional view showing an example of the thrust mechanism, thrust auxiliary means, and a lock mechanism.

  Next, the present invention will be specifically described based on the embodiment shown in the drawings. The belt type continuously variable transmission targeted by the present invention is a continuously variable transmission configured to continuously change the belt wrapping radius around the pulley by changing the groove width of the pulley. In combination with changing the ratio, each pulley is composed of a fixed sheave and a movable sheave in order to set a so-called clamping pressure for clamping the belt to a value as necessary. In the present invention, it is possible to configure the movable sheave by applying axial thrust to the movable sheave by the spring and the torque cam so as to set the predetermined clamping pressure and transmission torque capacity. The transmission is preferably a so-called dry belt-type continuously variable transmission that does not need to supply lubricating oil between the belt and the pulley.

  FIG. 3 schematically shows an example, in which the driving pulley 1 and the driven pulley 2 are arranged with their respective central axes parallel to each other. The driving pulley 1 is a pulley to which torque is input from a driving force source Eng, and is constituted by a fixed sheave 3 and a movable sheave 4. The driving force source Eng may be an internal combustion engine such as a gasoline engine, a motor, or a hybrid drive device combining these. Further, an appropriate transmission mechanism (not shown) such as a torque converter or a starting clutch may be disposed between the driving force source Eng and the driving pulley 1.

  The fixed sheave 3 is integrated with a drive shaft (input shaft) 5, while the movable sheave 4 moves back and forth in the axial direction of the drive shaft 5 in a state of facing the fixed sheave 3 and the drive shaft 5. Are fitted together so as to rotate together. The mutually facing surfaces of these sheaves 3 and 4 are formed in a taper shape, and a belt groove around which the belt 6 is wound is formed between these facing surfaces. Accordingly, the drive pulley 1 moves the movable sheave 4 back and forth in the axial direction to change the width of the belt groove (hereinafter simply referred to as the groove width), and accordingly, the winding radius of the belt 6 is increased or decreased. It is configured to change.

  The mechanism for moving the movable sheave 4 back and forth in the axial direction may be an appropriate mechanism known in the art. In the example shown in FIG. 3, the mechanism is configured by a mechanical actuator that does not require hydraulic pressure. The mechanical actuator is constituted by a feed screw mechanism, a screw shaft 7 is arranged in parallel with the drive shaft 5 described above, and a screw groove that meshes with the screw shaft 7 is formed on the outer peripheral portion. A vehicle 8 is attached to the movable sheave 4 so as to be rotatable and integrated in the axial direction. Further, the screw shaft 7 is connected to a speed change motor 10 via a reduction gear mechanism 9. That is, when the screw shaft 7 is rotated forward or reverse by the speed change motor 10, the movable sheave 4 approaches the fixed sheave 3 to narrow the groove width, and conversely moves away from the fixed sheave 3. Thus, the groove width is increased.

  The driven pulley 2 has a fixed sheave 11 and a movable sheave 12 in the same manner as the drive pulley 1 described above, and the opposing surfaces of these sheaves 11 and 12 are formed in a taper shape. The groove width, which is the distance between the sheaves 11, 12 changes according to the distance between the sheaves 11 and 12, and the winding radius of the belt 6 changes depending on the change in the groove width. The fixed sheave 11 is integrated with a driven shaft (output shaft) 13, while the movable sheave 12 can move back and forth in the axial direction of the driven shaft 13 and is integrated with the driven shaft 13 in the rotational direction. It is made to fit. A thrust mechanism 14 for generating a pressing force (thrust) for pushing the movable sheave 12 toward the fixed sheave 11 is provided on the back side of the movable sheave 12 (opposite to the fixed sheave 11). It is configured to output torque. That is, the thrust mechanism 14 is connected to an output rotary member (output gear in the example of FIG. 3) 15 and is configured to output torque from the output gear 15 to the differential gear 16.

  FIG. 4 shows an example of the thrust mechanism 14, and the movable sheave 12 has a boss portion (cylindrical portion) 17 protruding to the back side, and bushes 18, 19 at both end portions in the axial direction of the inner peripheral surface thereof. The movable sheave 12 is fitted to the outer peripheral surface of the driven shaft 13 through these bushes 18 and 19 so as to move back and forth in the axial direction.

  A key 21 is attached between the bushes 18 and 19 on the inner peripheral portion of the boss portion 17. The key 21 is for integrating the movable sheave 12 and the driven shaft 13 in the rotational direction, and protrudes from the inner peripheral surface of the boss portion 17 to the inner peripheral side. A key groove 22 is formed on the inner peripheral surface of the boss portion 17 so that the protruding portion of the key 21 is fitted and guided in the axial direction.

  Further, the cam member 23 is fitted to the driven shaft 13 so as to be relatively rotatable. The cam member 23 is a member formed in a cylindrical shape, and is positioned and supported by a fixed portion 24 integral with a transmission case (not shown) so as to be rotatable through a bearing 25 and not to move in the axial direction. ing. Further, the driven shaft 13 is inserted on the inner peripheral side, and a bush 26 is disposed between the two. The aforementioned output gear 15 is attached to the cam member 23.

  The cam member 23 is integrally formed with a cylindrical cam portion 27 extending from the outer peripheral side of the boss portion 17 of the movable sheave 12 to the back surface of the movable sheave 12. The front end surface in the axial direction of the cylindrical cam portion 27 is an uneven surface that protrudes in the axial direction and continues in the circumferential direction, and this uneven surface is the cam surface. On the other hand, a cam portion (cam tip) 28 that is slidably brought into contact with the cam surface is provided on the back surface of the movable sheave 12. A torque cam 29 is constituted by the cam surface and the cam tip 28 which are in contact with each other. That is, the cam surface is an inclined surface that is inclined with respect to the axial direction and the circumferential direction of the driven shaft 13 or the cylindrical cam portion 27, whereas the cam tip 28 is axially directed to the so-called inclined surface. Therefore, when a torque acts between the two, a component in the axial direction corresponding to the torque, that is, a thrust is generated. The configuration of the torque cam may be the same as a conventionally known torque cam.

  Further, the cam member 23 is formed with a flange portion 23A protruding outward in the radial direction at the rear end portion (right end portion in FIG. 4) of the cylindrical cam portion 27. The flange portion 23A and the movable sheave A spring 30 that presses the movable sheave 12 toward the fixed sheave 11 is disposed between the movable sheave 12 and the fixed sheave 11. Therefore, the thrust mechanism 14 in the example shown in FIG. 4 applies a so-called preload to the movable sheave 12 by the spring 30, and also applies a thrust according to the torque transmitted between the movable sheave 12 and the cam member 23 to the movable sheave 12. Is configured to give.

  A thrust assisting means for generating an auxiliary thrust in addition to the thrust by the thrust mechanism 14 is further provided. This thrust assisting means is for increasing the thrust as a whole that presses the movable sheave 12 toward the fixed sheave 11 when a predetermined condition is established, and comprises an auxiliary spring 31 and its auxiliary spring. A lock mechanism 32 that selectively locks the movable sheave 12 so as not to press the movable sheave 12 is provided. More specifically, a cylindrical portion 33 extending from the outer peripheral end of the flange portion 23 </ b> A described above toward the movable sheave 12 side is provided, and is provided on the inner peripheral side of the cylindrical portion 33 and on the outer periphery of the spring 30. On the side, an auxiliary spring 31 such as a coil spring that generates an elastic force toward the movable sheave 12 is provided. The auxiliary spring 31 is brought into contact with the side surface of the flange portion 23A, and a spring seat 34 is attached to the tip end portion (left end portion in FIG. 4) of the auxiliary spring 31. The spring seat 34 is formed in a cylindrical shape so as to be in sliding contact with the inner peripheral surface of the cylindrical portion 33, and the outer peripheral corner portion of the front end portion against which the front end of the auxiliary spring 31 is abutted is a tapered surface that recedes obliquely backward. 35. A receiving seat 36 against which the spring seat 34 is abutted is formed on the back surface of the movable sheave 12 so as to protrude in the axial direction.

  The lock mechanism 32 is a mechanism for fixing the spring seat 34 so as not to advance toward the movable sheave 12, and the movable sheave 12 is set so as to set a gear ratio of about the minimum gear ratio (highest speed side gear ratio). At a position separated (retreated) from the fixed sheave 11, it is configured to engage with the spring seat 34 that is in contact with the receiving seat 36 of the movable sheave 12 at that position and stop its advancement. In the example shown in FIG. 4, a lock piece (stopper) 37 that engages with the tapered surface 35 of the spring seat 34 is attached to the distal end portion of the cylindrical portion 33 that is integral with the cam member 23. The stopper 37 is attached to the cylindrical portion 33 so as to move outward in the radial direction of the spring seat 34 by receiving an outward force generated in the taper surface 35 in the radial direction. For example, a pin 38 attached to the tip of the cylindrical portion 33 in the axial direction is rotated about the pin 38 and retracted outward in the radial direction of the spring seat 34, or a pin (not shown) directed in the tangential direction of the cylindrical portion 33. 4), and rotates in the clockwise direction in FIG. 4 so as to retract outward in the radial direction of the spring seat 34.

  As described above, the locking cover 39 is provided to prevent the stopper 37 from retracting outward in the radial direction of the cylindrical portion 33 and coming off the spring seat 34. The lock cover 39 is a cylindrical member that covers the outer peripheral side of the cylindrical portion 33 and is rotatable with respect to the cylindrical portion 33, and has an inner diameter at a location located on the outer peripheral side of the stopper 37. The inner diameter is set so as to abut against the outer peripheral portion of the stopper 37 protruding toward the inner peripheral side of the cylindrical portion 33 so as to engage with the spring seat 34. An opening 40 that allows the stopper 37 to be retracted outward in the radial direction of the cylindrical portion 33 is formed at the distal end portion of the lock cover 39. Further, the lock cover 39 is held by bearings 41 and 42 so as to be rotatable with respect to the cylindrical portion 33 or the cam member 23.

  A spring 43 is provided between the cam member 23 and the lock cover 39 to hold the lock cover 39 with respect to the cam member 23 in the circumferential direction. The spring 43 is disposed in the circumferential direction between the bracket 44 provided on the cam member 23 and the locking cover 39, and the locking cover 39 is moved in a free length state where no compression or tension occurs. The opening 40 is configured to be held in a state where it is detached from the outer peripheral side of the stopper 37. Further, the elastic force is such that the opening 40 is moved to the outer peripheral side of the stopper 37 when the inertial force acting on the lock cover 39 becomes a predetermined value or more as the rotational speed of the driven pulley 2 decreases. It is set to an elastic force that allows rotation to a matching position. When the lock cover 39 returns to the position where the stopper 37 is locked, it is necessary to generate a force to push the stopper 37 inward in the radial direction of the cylindrical portion 33 by the lock cover 39. Is formed as a surface curved in the circumferential direction, and when the edge of the opening 40 comes into contact with the curved surface, a torque generated by the elastic force of the spring 43 generates an inward acting force in the radial direction. It is supposed to let you. The locking cover 39 can be configured to be moved in the axial direction by an actuator (not shown) such as a motor. In this case, a curved surface in the axial direction may be formed on the outer surface of the stopper 37.

  Next, a transmission control apparatus according to the present invention for the belt type continuously variable transmission will be described. According to the belt type continuously variable transmission, the rotational speed of the driving force source Eng can be appropriately set by continuously changing the speed ratio when the vehicle is running. The speed change control is performed based on the target engine speed (target engine speed when an internal combustion engine is used as a driving force source) obtained based on the vehicle running state such as the vehicle speed and the accelerator opening, and the actual engine speed (actual engine speed). The gear ratio of the belt type continuously variable transmission is controlled so that the number) matches or follows. Therefore, this control is rotation number tracking control.

  If the vehicle is in a steady traveling state without sudden acceleration or sudden deceleration, the thrust assisting means is locked so that the above-described lock mechanism 32 is operating and the auxiliary spring 31 does not press the movable sheave 12 in the driven pulley 2. Yes. That is, when the minimum gear ratio or a gear ratio close thereto is obtained in steady running, the aforementioned auxiliary spring 31 is pushed and compressed by the movable sheave 12, and as a result, the spring seat 34 is positioned at the position of the stopper 37. Retreat until. Since the stopper 37 is pushed inward in the radial direction by the lock cover 39 as described above, when the spring seat 34 is sufficiently retracted, the stopper 37 that has been in contact with the cylindrical surface of the spring seat 34 protrudes to the inner peripheral side. Then, it engages with the tapered surface 35 of the spring seat 34. At the same time, the locking cover 39 is rotated by the elastic force of the spring 43 and the opening 40 is removed from the position facing the outer surface of the stopper 37. That is, the stopper 37 is prevented from retracting to the outer peripheral side of the cylindrical portion 33, that is, unlocking.

  In this way, in the steady running state, the auxiliary spring 31 does not act on the movable sheave 12, and therefore the thrust force that presses the movable sheave 12 toward the fixed sheave 11 side is between the back surface of the movable sheave 12 and the cam member 23. This is the sum of the elastic force generated by the provided spring 30 and the axial force generated by the torque cam 26 in accordance with the transmitted torque. The spring so that the elastic force and the axial force generated by the torque cam 26 do not become excessive with respect to the belt clamping pressure (load for clamping the belt by the sheaves 11, 12) required for steady running. 31 and the torque cam 26 are designed. Therefore, the frictional force and power loss between the belt 6 and the pulleys 1 and 2 generated in a steady running state are not excessive, and are within the range assumed in design.

  On the other hand, when a vehicle equipped with the belt type continuously variable transmission decelerates rapidly, the gear ratio is rapidly increased to prepare for a restart after the vehicle stops. Specifically, the drive pulley 1 is adjusted so that the actual engine speed decreases in accordance with the target engine speed determined based on the data representing the vehicle running state such as the vehicle speed and the accelerator opening and the shift diagram. The groove width is increased, and accordingly, the groove width of the driven pulley 2 is decreased. In this case, in the thrust assisting means shown in FIG. 4 described above, a large inertia force acts on the lock cover 39 due to the large deceleration, and as a result, the lock cover 39 compresses or extends the spring 43. Let it rotate. When the locking cover 39 rotates until the opening 40 coincides with the outer peripheral side of the stopper 37, the stopper 37 that is pushed outward in the radial direction by the elastic force of the auxiliary spring 31 is unlocked, and the stopper 37 is The spring seat 34 is pushed outward in the radial direction. As a result, the restriction on the extension of the auxiliary spring 31 is removed, so that the auxiliary spring 31 extends toward the back surface of the movable sheave 12, and the spring seat 34 comes into contact with the receiving seat 36 of the movable sheave 12, thereby elastically supporting the auxiliary spring 31. A force acts on the movable sheave 12. Thus, since the elastic force of the auxiliary spring 31 is added to the thrust force that presses the movable sheave 12 toward the fixed sheave 11, the movable sheave 12 is rapidly pressed toward the fixed sheave 11, and accordingly the winding radius of the belt 6 is increased. Increase. That is, the gear ratio is rapidly increased.

  When the inertial force for rotating the lock cover 39 is reduced, the lock cover 39 tries to rotate to the original position by the torque based on the elastic force of the spring 43, but the stopper 37 contacts the outer peripheral surface of the spring seat 34. Further, it cannot move to the inner circumference side. Therefore, the unlocked state of the auxiliary thrust mechanism is maintained.

  When the vehicle speed gradually increases and the accelerator pedal is returned to bring the vehicle into a cruising state, for example, the gear ratio becomes close to the minimum gear ratio (the gear ratio on the highest speed side). When the transmission gear ratio becomes equal to or less than the reference transmission gear ratio γ0, the movable sheave 12 in the driven pulley 2 presses and retracts the spring 30 and the auxiliary spring 31 and moves backward in the right direction in FIG. Pushed back. As described above, since the stopper 37 is pushed inward in the radial direction by the locking cover 39, when the tapered surface 35 of the spring seat 34 is retracted to the position of the stopper 37, the stopper 37 protrudes inward in the radial direction. Engages with the tapered surface 35. That is, the lock mechanism 32 locks the auxiliary thrust means, and the elastic force of the auxiliary spring 31 is received by the stopper 37 so that it does not act on the movable sheave 2.

  By the way, in the state where the lock mechanism 32 is unlocked, the thrust applied to the movable sheave 12 is large, and if the vehicle travels in this state, the belt clamping pressure becomes excessive, which causes power loss. Therefore, the speed change control device according to the present invention is configured to execute the control shown in FIG. FIG. 1 is a flowchart for explaining the contents of the control, and the routine shown here is repeatedly executed in a short cycle time in an electronic control unit mainly composed of a microcomputer. First, it is determined whether or not the thrust assisting unit described above has been activated (step S1). In the belt-type continuously variable transmission having the configuration shown in FIG. 4 described above, the lock assisting means is unlocked by the lock cover 39 rotating relative to the cam member 23 by the inertial force, and thrust assisting is performed. Since the means is activated, it may be determined in step S1 whether or not a deceleration that causes the inertia force to rotate the lock cover 39 has occurred. The deceleration may be obtained by calculating a time change rate of the vehicle speed or may be obtained as a detection value of the acceleration sensor. Further, if the auxiliary spring 31 presses the movable sheave 12, the position of the spring seat 34 changes to the movable sheave 12 side as shown in FIG. The determination of S1 may be performed, or the total of the thrust acting on the movable sheave 12 may be detected by a sensor such as a load cell and the determination of step S1 may be performed.

  If the determination in step S1 is affirmative, that is, if the thrust assisting means is unlocked and the elastic force of the auxiliary spring 31 is acting on the movable sheave 12, the gear ratio is changed after the thrust assisting means is unlocked. It is determined whether or not γ is less than or equal to the minimum speed ratio or a predetermined reference speed ratio γ0 close to the minimum speed ratio (step S2). This reference speed ratio γ0 is a speed ratio set when the movable sheave 12 is retracted to a position where the spring seat 34 engages with the stopper 37. Therefore, in step S2, the thrust by the auxiliary spring 31 is substantially reduced. It is determined whether or not the movable sheave 12 remains active.

  If a positive determination is made in step S2 because the gear ratio γ is not less than or equal to the reference gear ratio γ0, a gear line in which the gear ratio γ is likely to become the reference gear ratio γ0 is selected ( Step S3). On the other hand, when a negative determination is made in step S1 because the auxiliary thrust means is not operating, and when a negative determination is made in step S2 because the transmission gear ratio γ is equal to or less than the reference transmission gear ratio γ0. Normal shift control is executed (step S4).

  Here, the control of the speed ratio will be described. The speed ratio of a vehicle equipped with a continuously variable transmission is controlled so that the engine speed becomes a speed with good fuel efficiency. For example, the target driving force is obtained based on the vehicle speed and the accelerator opening, and the target output of the engine is obtained based on the target driving force and the vehicle speed. A target engine speed that outputs the target output in a state with good fuel efficiency is obtained, and the continuously variable transmission is controlled so that the actual engine speed becomes the target speed. In the case of a belt type continuously variable transmission, the belt winding radius or the position of the movable sheave 2 in the drive pulley 1 is controlled. The target engine torque is obtained from the target output and the target engine speed, and the throttle opening is controlled so that the engine torque becomes the target engine torque.

  In this way, the target engine speed during traveling can be determined by parameters determined from the traveling state such as the vehicle speed and the accelerator opening, and this is represented by a shift diagram. An example is shown in FIG. FIG. 2A is a shift diagram used in normal shift control, and FIG. 2B is a temporary shift diagram used in step S3. In these figures, γmax represents the maximum gear ratio that can be set by the mechanism of the belt-type continuously variable transmission, and γmin represents the minimum gear ratio that can be set by the mechanism of the belt-type continuously variable transmission. Between these maximum speed ratio γmax and minimum speed ratio γmin, the engine speed (that is, the speed ratio) at which fuel efficiency is improved is determined for each vehicle speed and accelerator opening θ. According to the shift diagram used in the normal shift control shown in FIG. 2 (a), for example, when the accelerator opening θ is “50%”, the vehicle speed and the engine speed increase with the maximum gear ratio γmax. Then, when the driving state indicated by the symbol “A” in FIG. 2A is reached, the vehicle speed is gradually increased while maintaining the engine speed. That is, the speed ratio γ is gradually reduced. Then, when the driving state indicated by the symbol “B” at which the speed ratio γ becomes the minimum transmission γmin is reached, the vehicle speed and the engine speed increase because no further upshifting is possible.

  The shift diagram shown in FIG. 2B is a diagram in which the target engine rotational speed is changed to a rotational speed lower than the rotational speed determined in the shift diagram used in normal shift control. In other words, the vehicle speed at which the predetermined target engine speed is set is changed to a small value, and the accelerator opening is changed to a large value. That is, the engine speed is controlled so as to reach the target speed at a relatively low vehicle speed as compared with the shift control at the normal time. Therefore, for example, as in the above example, when the vehicle starts with the accelerator opening θ being “50%”, the vehicle speed and the engine speed increase with the maximum gear ratio γmax, and the symbol “A ′” in FIG. When the driving state indicated by is reached, the vehicle speed is gradually increased while maintaining the engine speed. That is, the speed ratio γ is gradually reduced. The driving state indicated by the symbol “A ′” is set so that the line with the accelerator opening θ of “50%” has a relatively low engine speed, and therefore a shift diagram used in normal shift control. Is the operating state at a lower engine speed. When the driving state indicated by the symbol “B ′” is reached, the speed ratio γ becomes the minimum transmission γmin. The driving state indicated by the symbol “B ′” is an operating state at a lower engine speed and vehicle speed than that according to a shift diagram used in normal shift control. Therefore, by changing the gear map in step S3 as described above, the gear ratio is likely to become the minimum gear ratio γmin, and naturally, the reference gear ratio γ0 at which the lock mechanism 32 described above is switched to the locked state is likely to be obtained. .

  If the content of the speed change control is changed in this way and the speed change ratio is set earlier than the reference speed change ratio γ0, the elastic force of the auxiliary spring 31 is received by the stopper 37 as described above so that it does not act on the movable sheave 2. Become. That is, the state in which the belt clamping pressure is excessively large is eliminated at an early stage, and power loss and accompanying fuel consumption reduction are prevented or suppressed.

  In the above example, the shift diagram is changed to control the gear ratio to easily become the reference gear ratio γ0. However, in that case, it is not necessary to change the gearshift line for all accelerator openings. The shift line of “θ = 0%” and the shift line of “θ = 100%” may be the same as those in the normal shift map. Further, instead of changing the shift line, the target engine speed or the target gear ratio may be obtained by performing correction such as multiplying the vehicle speed and the accelerator opening as parameters used in the shift control by a coefficient. In short, it is only necessary to change the condition for determining the gear ratio. Therefore, the functional means for executing the control in step S3 corresponds to the speed change condition changing means of the present invention.

  The locking means in the present invention is not limited to the configuration shown in the above-described specific example, and is configured to directly drive a member corresponding to the stopper 37 by an electromagnetic force or a rotational force of a motor. It may be a thing. Further, the thrust assisting means in the present invention is not limited to a configuration that generates a thrust by a spring, and may be configured to use an electromagnetic force or a link mechanism.

  Eng: driving force source, 3 ... fixed sheave, 4 ... movable sheave, 5 ... drive shaft (input shaft), 6 ... belt, 11 ... fixed sheave, 12 ... movable sheave, 13 ... driven shaft (output shaft), 14 ... Thrust mechanism, 15 ... output gear, 23 ... cam member, 27 ... cylindrical cam part, 28 ... cam part (cam tip), 29 ... torque cam, 30 ... spring, 31 ... auxiliary spring, 32 ... lock mechanism, 33 ... cylindrical part, 34 ... Spring seat, 35 ... Tapered surface, 37 ... Lock piece (stopper), 39 ... Cover for locking, 40 ... Opening.

Claims (4)

The pulley has at least a pair of pulleys around which the belt is wound, and each pulley approaches and separates from each other to increase / decrease the width of the groove around which the belt is wound, thereby changing the transmission ratio. A thrust mechanism that causes the sheaves in the driven pulley to act on the sheaves in the driven pulley so that the sheaves in the driven pulley approach each other so as to reduce the width of the groove; In a transmission control device for a belt-type continuously variable transmission configured to set a transmission ratio according to a transmission condition,
Thrust auxiliary means for generating auxiliary thrust added to the thrust;
The thrust assisting means can be locked so that the auxiliary thrust does not act on the sheave in the driven pulley when the speed ratio is smaller than a predetermined speed ratio, and a predetermined condition is satisfied. Locking means for unlocking the thrust assisting means so that the auxiliary thrust acts on the sheave in the driven pulley when the
After the unlocking of the thrust assisting means by the locking means, a speed change for changing the speed change condition so that the speed change ratio is easily switched to the predetermined speed change ratio when the speed change ratio is larger than the predetermined speed change ratio. A speed change control device for a belt type continuously variable transmission, comprising: a condition change means. The belt type continuously variable transmission is mounted on a vehicle having an internal combustion engine as a driving force source,
The speed change condition includes a vehicle speed and an accelerator opening that determine a target rotational speed of the internal combustion engine,
The shift condition changing means changes the vehicle speed for determining the predetermined target rotational speed to a value smaller than the normal shift control, and changes the accelerator opening for determining the predetermined target rotational speed to a value larger than the normal shift control. The shift control device for a belt-type continuously variable transmission according to claim 1, further comprising at least one of means. The sheave includes a fixed sheave integrated with a rotating shaft, and a movable sheave that is fitted to the rotating shaft so as to approach and separate from the fixed sheave and moves back and forth in the axial direction of the rotating shaft. Including
The shift control device for a belt-type continuously variable transmission according to claim 1, wherein the thrust assisting unit includes a spring that presses the movable sheave toward the fixed sheave.   The shift control device for a belt-type continuously variable transmission according to any one of claims 1 to 3, wherein the predetermined condition includes a sudden deceleration state in which the number of rotations of the pulley rapidly decreases. .