JP4870507B2 - Return spring design method for belt type continuously variable transmission and return spring designed by the design method - Google Patents

Description

  The present invention relates to a return spring design method provided for obtaining a clamping pressure against a belt in a belt-type continuously variable transmission for automobiles and the like, and a return spring designed by the design method. In particular, the present invention relates to a measure for suppressing deformation of the return spring in the radially outward direction.

  Conventionally, as disclosed in, for example, Patent Document 1 below, a belt-type continuously variable transmission is known as a transmission mounted on the output side of an automobile engine. This belt-type continuously variable transmission has two shafts arranged in parallel to each other, and a primary pulley and a secondary pulley respectively provided on each shaft. Both the primary pulley and the secondary pulley have a structure in which a fixed sheave and a movable sheave are combined, and a V-shaped groove is formed between the sheaves. Further, the movable sheave is configured to be able to contact and separate from the fixed sheave. A V-belt is wound around the V-groove of the primary pulley and the V-groove of the secondary pulley, and hydraulic chambers for generating the clamping force in the axial direction on the movable sheave are separately provided for each pulley. Is provided. Thus, by individually controlling the hydraulic pressure of each hydraulic chamber, the groove width of each pulley is changed, the winding radius of the V-belt is changed, and the gear ratio is changed.

  By the way, when it is necessary to pull the vehicle body in the event of a failure of the vehicle (hereinafter referred to as towed), the wheel of the vehicle is towed in contact with the road surface. Input to the continuously variable transmission via a differential (so-called differential gear unit), final reduction gear (so-called final gear unit), etc., and the secondary pulley of the continuously variable transmission rotates in response to the rotational force of the wheels It becomes. That is, the continuously variable transmission is activated by the rotational force of the wheels.

  In such a towed state, the engine of the towed vehicle is not driven, the hydraulic pump is not operated, and no hydraulic pressure is applied to the hydraulic chamber for generating the clamping pressure. It is. That is, the continuously variable transmission is in a state where the clamping pressure by the hydraulic pressure is not obtained. In such a situation, due to insufficient clamping pressure due to hydraulic pressure, slip occurs between the pulley and the belt, and the friction coefficient changes due to wear on each contact surface of the pulley and the belt. Therefore, there is a possibility that the power transmission performance during the next normal operation of the continuously variable transmission (when the engine output is decelerated and transmitted to the wheels) is adversely affected.

In view of this point, for example, in Patent Document 2 below, a coil spring (hereinafter referred to as a coil spring) is applied to the secondary pulley so that the clamping pressure can be applied to the movable sheave even when the clamping pressure by the hydraulic pressure is not obtained. , Called a return spring). In other words, even if the urging force in the direction toward the fixed sheave is given to the movable sheave by the return spring, and the clamping force by the hydraulic pressure is not obtained at the time of the towing, the urging force of the return spring The pinching pressure is obtained, thereby preventing the slip.
Japanese Patent Laid-Open No. 9-217819 Japanese Utility Model Publication No. 63-152962

  By the way, in the belt type continuously variable transmission provided with the return spring as described above, in a situation where the movable sheave is moved backward from the fixed sheave so that the groove width of the pulley is increased to reduce the winding radius of the V belt. The return spring is in a compressed state. In this case, the outer diameter of the return spring increases with this compression.

  Thus, in the situation where the outer diameter of the return spring becomes large, the amount of deformation of the return spring toward the outer peripheral side (radially outward) is not necessarily uniform over the entire circumference, and the amount of deformation is partially. May be larger. Further, since the return spring rotates together with the pulley at a relatively high speed, a large centrifugal force acts. For this reason, in a situation where a difference occurs in the amount of deformation to the outer peripheral side and the position of the center of gravity of the return spring is deviated from the axial center of the spring, the centrifugal force in the direction of deviation acts particularly greatly. The amount of deformation toward the outer peripheral side in the shift direction is further increased.

  FIG. 5 shows a situation in which the amount of deformation toward the outer peripheral side increases in the lower part of the outer circumference of the return spring b provided in the secondary pulley a. In FIG. 5, c is a fixed sheave, d is a movable sheave, e is a secondary shaft, f is a secondary piston, and g is a V-belt.

  In this way, in a situation where the amount of deformation of the return spring b toward the outer peripheral side is partially extremely large, the outer peripheral surface of the return spring b rotating at high speed is the same as that of the secondary piston f disposed on the outer peripheral side. It will contact | abut to an internal peripheral surface, and there exists a possibility of causing the malfunction that the outer peripheral surface of the return spring b and the internal peripheral surface of the secondary piston f wear.

  As a means for solving such a problem, it is conceivable that the power transmission path between the wheel and the continuously variable transmission is interrupted during the towing, thereby eliminating the return spring. For example, there is a technique such as releasing the meshing state of the gear in the power transmission path.

  However, this requires a work for cutting off the power transmission path in the previous stage of the towed work (work for releasing the meshing of the gears), the work is complicated, and the time until the vehicle is moved by towing Will take a long time.

  Further, Patent Document 2 discloses that a plurality of return springs are provided in the axial direction to suppress the amount of deformation of each spring in the radial direction.

  However, the configuration of Patent Document 2 is not preferable because the number of parts and the assembly work increase as the number of return springs increases.

  The present invention has been made in view of such a point, and the object of the present invention is to use a single spring as a return spring provided in a belt-type continuously variable transmission even in the radial direction thereof. A return spring design method capable of suppressing outward deformation and a return spring designed by the design method.

-Principle of solving the problem-
The solution principle of the present invention devised in order to achieve the above object is to set the effective number of windings of the return spring appropriately to obtain a sufficient clamping force against the belt, but to the outside of the return spring in the radial direction. The amount of deformation can be suppressed within a range that does not contact the outer peripheral member.

-Solution-
Specifically, in the present invention, a belt is stretched between a driving pulley and a driven pulley each having a fixed sheave and a movable sheave that can move forward and backward toward the fixed sheave, and the rotational force of the driving pulley is Can be transmitted to the driven pulley via the belt, and the movable sheave moves forward and backward toward the fixed sheave to change the belt winding position in the radial direction of each pulley to change the speed. A return spring for a belt-type continuously variable transmission that has a return spring for securing a sheave clamping force with respect to the belt in at least one of the driving pulley and the driven pulley while the ratio is variable The design method is assumed. When the return spring rotates together with the pulley by mounting both ends in the axial direction immovably and the pitch of the effective winding number portion is constant, the effective winding number of the return spring is Is an effective number of windings for obtaining a necessary clamping pressure or more that does not cause slip between the pulley and the belt as a clamping pressure of the sheave to the belt, and the following formula (1)
N = (a + 0.5) ± 0.15 (1)
(N is the number of effective turns of the return spring, a is an integer of 1 or more)
The minimum number of windings among the effective number of windings satisfying the above condition is set.

A return spring designed by this design method is also within the scope of the technical idea of the present invention. That is, a belt is stretched between a driving pulley and a driven pulley each having a fixed sheave and a movable sheave capable of moving forward and backward toward the fixed sheave, and the rotational force of the driving pulley is transmitted via the belt. The transmission can be transmitted to the driven pulley, and the movable sheave can be moved back and forth toward the fixed sheave to change the belt winding position in the radial direction of each pulley to change the gear ratio. The belt-type continuously variable transmission is assumed to have a return spring provided to secure the sheave clamping pressure with respect to the belt in at least one of the driving pulley and the driven pulley. With respect to this return spring, both ends in the spring axial direction are mounted immovably so that the pulley rotates and the pitch of the effective winding number portion is constant, and the sheave clamping pressure with respect to the belt An effective number of windings that provides a necessary clamping pressure or more that does not cause slip between the pulley and the belt, and the following formula (1)
N = (a + 0.5) ± 0.15 (1)
(N is the number of effective turns of the return spring, a is an integer of 1 or more)
It is formed with the minimum number of windings among the effective number of windings satisfying the above.

  If the effective number of turns of the return spring is set in this way, the amount of deformation to the outer peripheral side when the return spring is compressed (in the situation where the amount of deformation to the outer peripheral side partially increases as described above) The amount of deformation of the portion; the amount of deformation in the maximum deformation region) can be reduced. This is because there is a correlation between the effective number of turns of the return spring and the amount of deformation of the return spring toward the outer periphery (the amount of deformation in the maximum deformation region). In other words, as the effective number of turns of the return spring is increased, even if the compression amount is the same, the amount of deformation of the return spring radially outward (the amount of deformation in the maximum deformation region) increases and decreases periodically. Repeatedly (see FIG. 3), when the condition of the above formula (1) is satisfied, the inflection point portion which is the minimum value of the increase / decrease period of the deformation amount (the “effective winding number design value of the present invention” in FIG. 3) ).

  For this reason, the position of the center of gravity of the return spring is not greatly deviated from the center of the spring, and even if this return spring rotates with the pulley and a large centrifugal force acts, the amount of deformation of the return spring toward the outer peripheral side There will be no situation where is partially extremely large. As a result, the outer peripheral surface of the return spring does not come into contact with the inner peripheral surface of a member (for example, a piston member) disposed on the outer peripheral side, and is disposed on the outer peripheral surface of the return spring or on the outer peripheral side thereof. It is possible to avoid wear on the inner peripheral surface of the member that is being used.

  More specifically, the effective number of turns of the return spring is set as follows. In other words, the effective number of windings is set to an effective number of windings that does not reach the contact limit even when the belt winding position is located on the innermost side and the return spring is compressed by the movable sheave. ing. The “adhesion limit” herein refers to a compressed state in which return springs formed of coil springs are compressed, and spring wire rods adjacent to each other in the axial direction come into contact with each other, and further compression cannot be performed.

  As a result, when the belt winding position is moved toward the inner circumferential side, the return spring reaches the contact limit in the middle, and the belt winding position can be moved further to the inner circumferential side. It is possible to avoid such a situation that it becomes impossible, and it is possible to obtain a desired gear ratio in the belt type continuously variable transmission.

  Further, as an application form of the return spring designed by each of the above solution means, it can be applied to obtain a clamping pressure that does not cause a slip between the driven pulley and the belt. The return spring exhibits a function when the automobile is towed as described above, and at this time, the rotational force of the wheels is input to the continuously variable transmission. That is, in the continuously variable transmission, the rotational force of the wheels is first input to the driven pulley. By applying the return spring designed as described above to the driven pulley, slipping at the driven pulley is prevented, and as a result, slipping is also prevented at the driving pulley.

  In the present invention, by appropriately setting the effective number of windings of the return spring, it is possible to suppress the amount of deformation of the return spring toward the outer peripheral side while sufficiently obtaining the clamping pressure on the belt. For this reason, it is possible to avoid wear on the outer peripheral surface of the return spring and the inner peripheral surface of the member disposed on the outer peripheral side, and it is possible to improve the durability of the belt type continuously variable transmission.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. This embodiment demonstrates the case where this invention is applied to the return spring with which the belt-type continuously variable transmission (what is called CVT: Continuously Variable Transmission) for motor vehicles was equipped. In the following embodiments, a belt type continuously variable transmission mounted on an FF (front engine / front drive) vehicle will be described.

(Overall structure of transaxle)
First, the overall configuration of a transaxle equipped with a belt type continuously variable transmission will be described.

  FIG. 1 is a skeleton diagram of a transaxle in the present embodiment. As shown in FIG. 1, the rotational power of the crankshaft 1 a of the engine 1 is transmitted to the wheels 3 via the power transmission system 2. The engine 1 and the power transmission system 2 are controlled by an engine control unit (ECU) 4.

  The power transmission system 2 includes a torque converter 10 as a clutch, a forward / reverse switching mechanism 20, a belt-type continuously variable transmission 30, a final reduction gear 40, and a differential device 50. For example, since it is the same as the structure shown by Unexamined-Japanese-Patent No. 2004-360736, it demonstrates easily below.

  The torque converter 10 functions as a torque amplifier when the rotational speed difference between the pump impeller 13a and the turbine runner 13b is large, and functions as a fluid coupling when the rotational speed difference between the two becomes small.

  As the operation of the torque converter 10, the pump impeller 13 a rotates through the drive plate 11 and the front cover 12 as the crankshaft 1 a of the engine 1 rotates, and the turbine is driven by the flow of hydraulic fluid supplied from the oil pump 14. The runner 13b starts to rotate so as to be dragged. When the rotational speed difference between the pump impeller 13a and the turbine runner 13b is large, the stator 13c converts the flow of hydraulic fluid into a direction that assists the rotation of the pump impeller 13a.

  When the vehicle speed reaches a predetermined speed after the vehicle starts, the lockup clutch 15 is operated, and the power transmitted from the engine 1 to the front cover 12 is mechanically and directly transmitted to the input shaft 16. . In addition, fluctuations in torque transmitted from the front cover 12 to the input shaft 16 are absorbed by the damper mechanism 17.

  The forward / reverse switching mechanism 20 includes a double pinion planetary gear mechanism 21, a forward clutch 22, and a reverse brake 23.

  The sun gear 21 a of the planetary gear mechanism 21 is connected to the input shaft 16, and the carrier 21 b of the planetary gear mechanism 21 is connected to the primary shaft 31 of the belt type continuously variable transmission 30, and the forward clutch 22 and the reverse brake 23 are connected. By controlling, the power transmission path is changed to switch to forward rotation power (forward rotation direction) or reverse rotation power (reverse rotation direction).

  The belt-type continuously variable transmission 30 is configured such that a belt 33 is wound around a primary pulley (drive pulley) 34 of a primary shaft 31 and a secondary pulley (driven pulley) 35 of a secondary shaft 32, and the primary pulley 34 and the secondary pulley 35. By adjusting the V groove width with hydraulic actuators (drive means) 36, 37, the winding diameter of the belt 33 is changed to control the gear ratio by the continuously variable transmission 30. The belt 33 includes a large number of metal pieces and a plurality of steel rings.

  The primary shaft 31 is supported by the front case 5 and the rear case 6 via rolling bearings 61 and 62 so as to be substantially coaxial with the input shaft 16 of the torque converter 10. One secondary shaft 32 is supported by the front case 5 and the rear case 6 via rolling bearings 63 and 64 so as to be parallel to the primary shaft 31.

  The primary pulley 34 includes a fixed sheave 34 a that is integrally formed on the outer periphery of the primary shaft 31 and a movable sheave 34 b that is mounted on the outer periphery of the primary shaft 31 so as to be axially displaceable. The movable sheave 34 b is formed by a hydraulic actuator 36. By driving, the V groove width between the sheaves 34a and 34b is changed.

  One secondary pulley 35 includes a fixed sheave 35a integrally formed on the outer periphery of the secondary shaft 32 and a movable sheave 35b mounted on the outer periphery of the secondary shaft 32 so as to be axially displaceable. The movable sheave 35b is a hydraulic actuator. By driving at 37, the V groove width between the sheaves 35a, 35b is changed.

  A parking gear 38 is provided on the side of the secondary pulley 35.

  The final reduction gear 40 has two counter driven gears 41 and 42 that mesh with each other and a final drive gear 43.

  The first counter driven gear 41 is fixed to a shaft 44 connected to the secondary shaft 32 of the belt type continuously variable transmission 30.

  The second counter driven gear 42 and the final drive gear 43 are respectively fixed to an intermediate shaft 45 disposed substantially parallel to the secondary shaft 32 so as to be separated from each other in the axial direction.

  The shaft 44 is supported via rolling bearings 65 and 66, and the intermediate shaft 45 is supported via rolling bearings 67 and 68, respectively.

  The differential device 50 distributes and transmits the rotational power received from the final reduction gear 40 to the wheels 3 connected to the pair of left and right axle shafts 51 and 52 at an appropriate ratio, and is disposed in the differential case 53. Yes.

(Configuration of secondary pulley 35)
Next, the configuration of the secondary pulley 35 to which a return spring, which is a characteristic feature of this embodiment, is mounted will be described.

  FIG. 2 is a cross-sectional view showing the configuration of the secondary pulley 35 and the peripheral portion. As shown in FIG. 2, the secondary pulley 35 is disposed between the rolling bearing 63 and the rolling bearing 64 on the outer periphery of the secondary shaft 32. Further, the secondary shaft 32 is rotatable about the axis B1, and two oil passages 71 and 72 extending in the axial direction are formed therein. These oil passages 71 and 72 are communicated with a hydraulic circuit of a hydraulic control device (not shown). Two oil passages 73 and 74 that extend in the radial direction of the secondary shaft 32 and open to the outer peripheral surface of the secondary shaft 32 are communicated with the one oil passage 71.

  Further, a step 32 a is formed between the opening portion of one oil passage 74 on the outer periphery of the secondary shaft 32 and the rolling bearing 63.

  The movable sheave 35b of the secondary pulley 35 has a thick cylindrical portion 35c and a radial portion that is continuously formed at the end of the cylindrical portion 35c on the fixed sheave 35a side to form a V groove with the fixed sheave 35a. 35d.

  An annular piston member 75 is mounted between the step 32a and the rolling bearing 63. The piston member 75 is fitted into the step portion 32a and extends radially outward, and from the outer peripheral end of the first radial direction portion 75a toward the radial direction portion 35d of the movable sheave 35b. It has a cylindrical portion 75b that extends and a second radial direction portion 75c that extends while curving from the end of the cylindrical portion 75b toward the outer periphery. A spring seat 75d for supporting one end of a return spring 8 described later is formed at the boundary between the cylindrical portion 75b and the second radial direction portion 75c.

  A groove 35e extending in the axial direction is formed on the inner peripheral surface of the cylindrical portion 35c of the movable sheave 35b, while a groove 32b extending in the axial direction is formed on the outer peripheral surface of the secondary shaft 32. A plurality of the grooves 35e and the grooves 32b are formed at predetermined intervals in the circumferential direction. Then, the secondary shaft 32 and the movable sheave 35b are positioned so that the groove 35e on the movable sheave 35b side and the groove 32b on the secondary shaft 32 side have the same phase in the circumferential direction, and straddle both the grooves 35e and 32b. A plurality of balls (not shown) are arranged. In other words, the secondary shaft 32 and the movable sheave 35b can be smoothly moved relative to each other in the axial direction by the grooves 35e and 32b and the ball, but cannot be relatively moved in the circumferential direction.

  On the other hand, the movable sheave 35b is integrally formed with a cylindrical guide member 35f extending toward the outer peripheral portion of the piston member 75 from the position near the outer peripheral end of the radial direction portion 35d. The inner peripheral surface of the guide member 35f is in contact with the tip of the second radial direction portion 75c that is the outer peripheral side end portion of the piston member 75. A resin seal ring 75e is attached to the tip of the second radial direction portion 75c. Thus, a space surrounded by the radial portion 35d of the movable sheave 35b, the guide member 35f, and the piston member 75 is formed as the hydraulic chamber 9. The oil passage 74 communicates with the hydraulic chamber 9, and when hydraulic pressure is applied to the hydraulic chamber 9 through the oil passages 71 and 74, as shown in the lower half of FIG. The sheave 35b moves on the secondary shaft 32 toward the fixed sheave 35a, narrowing the groove width of the V groove and increasing the winding diameter of the belt 33. The upper half of FIG. 2 shows a state in which the movable sheave 35b is retracted (separated) from the fixed sheave 35a and the groove width of the belt 33 is reduced by increasing the groove width of the V groove.

  A return spring 8 is interposed between the movable sheave 35b and the piston member 75 in a compressed state. Specifically, as described above, the spring seat 75d is formed between the cylindrical portion 75b and the second radial direction portion 75c of the piston member 75. Further, a spring fixing ring 81 is attached to the surface of the movable sheave 35b on the back side (the side facing the hydraulic chamber 9) and facing the spring seat 75d. A return spring 8 is mounted between the spring seat 75d and the spring fixing ring 81 to apply a biasing force toward the fixed sheave 35a to the movable sheave 35b. When the return spring 8 is mounted, both ends of the return spring 8 are fixed so as not to move. Further, in the return spring 8, the pitch of the wire is set to be constant (equal pitch) in the effective winding number portion.

  By providing such a return spring 8, when the vehicle is towed, that is, no hydraulic pressure is applied to the hydraulic chamber 9, and the continuously variable transmission 30 is operated by the rotational force of the wheels 3. Even in such a state, the urging force of the return spring 8 can sufficiently obtain the clamping force of the sheaves 35 a and 35 b against the belt 33, so that no slip occurs between the secondary pulley 35 and the belt 33.

(Design of return spring 8)
Next, a method for designing the return spring 8 which is a feature of the present embodiment will be described. The return spring 8 is made of a coil spring made of a metal such as spring steel, and has a wire diameter of, for example, 5 mm and a spring outer diameter of, for example, 50 mm. These materials and dimensions are not limited to this, and for example, the wire diameter may be 3 mm and the spring outer diameter may be 40 mm.

  The feature of this embodiment is the setting of the effective winding number of the return spring 8. This will be specifically described below.

  In setting the effective number of turns in the design stage of the return spring 8, it is designed to satisfy the following conditions.

That is, as a clamping pressure of the sheave to the belt 33 (a clamping pressure to the belt 33 obtained between the fixed sheave 35a and the movable sheave 35b), slip is caused between the sheaves 35a and 35b and the belt 33 at the time of towing. The effective number of windings that can achieve a necessary clamping pressure (for example, a force of about 10 N) that is not generated, and the following formula (1)
N = (a + 0.5) ± 0.15 (1)
(N is the number of effective turns of the return spring, a is an integer of 1 or more)
The effective number of turns satisfying

  In general, the return spring 8 needs to increase the effective number of turns to increase the holding pressure of the sheave without increasing the stress generated in the compressed state during use. Winding that is the minimum required value among a plurality of values of winding number (about 1.5, about 2.5, about 3.5, about 4.5, ... each including a manufacturing variation of ± 0.15) Of the number of turns, that is, the number of turns greater than or equal to the effective number of turns at which the clamping pressure equal to or greater than the necessary clamping pressure is obtained, the minimum value satisfying the above formula (1) is set as the effective number of turns of the return spring 8.

  For example, when the effective number of windings for obtaining the necessary clamping pressure or more is “3.2”, the effective number of windings of the return spring 8 is set to “about 3.5”. Further, when the effective number of turns for obtaining the necessary clamping pressure or more is “3.8”, the effective number of turns of the return spring 8 is set to “about 4.5”.

  FIG. 3 is a diagram showing the relationship between the effective number of turns of the return spring 8 and the amount of deformation outward in the radial direction (the amount of deformation in the maximum deformation region). As described above, when the effective number of turns of the return spring 8 is changed, the amount of deformation of the return spring 8 outward in the radial direction (the amount of deformation in the maximum deformation region) is periodically repeated.

  Conventionally, the return spring has been formed with an effective number of turns that can provide the necessary clamping pressure. That is, the return spring was formed based on the technical idea that the necessary clamping pressure or more was obtained and the minimum effective number of turns was obtained (the number of turns indicated by the broken line A in FIG. 3).

  On the other hand, in the present invention, as described above, paying attention to the amount of deformation of the return spring 8 in the radially outward direction in which the increase and decrease are repeated periodically as the effective number of turns of the return spring 8 is changed, the return spring 8 When the effective winding number of 8 is increased, the minimum value (inflection point) of the amount of deformation of the return spring 8 to the outside in the radial direction is first exceeded after exceeding the effective winding number to obtain the necessary clamping pressure. The value of the effective number of windings (the number of windings indicated by the broken line B in FIG. 3) is set as the effective number of windings of the return spring 8.

  Note that the broken line C in FIG. 3 indicates that the return spring 8 is compressed and the spring wires adjacent to each other in the axial direction come into contact with each other to reach the “adhesion limit”, which is a compression state in which further compression cannot be performed. The number of turns. In other words, if the effective winding number is set larger than this value, the “contact limit” is reached before the movable sheave 35b reaches the most retracted position (before the winding diameter of the belt 33 is minimized). Will end up.

  The effective number of turns of the return spring 8 is set as described above, and the return spring 8 formed with this effective number of turns is applied to the belt type continuously variable transmission 30. According to this, as shown in FIG. 4, even when the return spring 8 is compressed between the movable sheave 35b and the piston member 75, the amount of deformation toward the outer peripheral side can be reduced. For this reason, the position of the center of gravity of the return spring 8 is not greatly deviated from the axis of the spring 8, and even if the return spring 8 rotates with the secondary pulley 35 and a large centrifugal force acts, There is no situation in which the amount of deformation toward the outer periphery becomes extremely large partially. As a result, the outer peripheral surface of the return spring 8 does not come into contact with the inner peripheral surface of the piston member 75 disposed on the outer peripheral side, and the outer peripheral surface of the return spring 8 or the inner peripheral surface of the piston member 75. Wear can be avoided.

-Other embodiments-
In the embodiment described above, the case where the present invention is applied to the design of the return spring 8 attached to the secondary pulley 35 has been described. The present invention is not limited to this, and when a return spring is also attached to the primary pulley 34, the present invention can be applied to the design of the return spring on the primary pulley 34 side.

It is a skeleton figure which shows the whole structure of the transaxle in embodiment. It is sectional drawing which shows the structure of the secondary pulley and peripheral part in embodiment. It is a figure which shows the relationship between the effective winding number of a return spring, and the deformation amount in a maximum deformation area | region. It is sectional drawing which shows the state of the return spring at the time of the high speed rotation of the secondary pulley in embodiment. It is sectional drawing which shows the state of the return spring at the time of the high speed rotation of the secondary pulley in a prior art example.

Explanation of symbols

30 Belt type continuously variable transmission 33 Belt 34 Primary pulley (drive pulley)
35 Secondary pulley (driven pulley)
35a Fixed sheave 35b Movable sheave 8 Return spring

Claims (4)

A belt is stretched between a driving pulley and a driven pulley, each having a fixed sheave and a movable sheave capable of moving forward and backward toward the fixed sheave, and the rotational force of the driving pulley is transferred to the driven side via the belt. In addition to being configured to transmit to the pulley, the movable sheave is moved forward and backward toward the fixed sheave to change the belt winding position in the radial direction of each pulley so that the gear ratio can be changed. On the other hand, a return spring design method for a belt-type continuously variable transmission provided with a return spring for securing the sheave clamping force against the belt in at least one of the driving pulley and the driven pulley,
When the return spring rotates together with the pulley by being mounted so that both ends in the axial direction are immovable and the pitch of the effective winding portion is constant, the effective winding number of the return spring is The effective number of windings for obtaining the required clamping pressure or more that does not cause slip between the pulley and the belt as the clamping pressure of the sheave to the belt, and the following formula (1)
N = (a + 0.5) ± 0.15 (1)
(N is the number of effective turns of the return spring, a is an integer of 1 or more)
A return spring design method for a belt-type continuously variable transmission, characterized in that the minimum number of windings among the effective number of windings satisfying the above is set. A belt is stretched between a driving pulley and a driven pulley, each having a fixed sheave and a movable sheave capable of moving forward and backward toward the fixed sheave, and the rotational force of the driving pulley is transferred to the driven side via the belt. In addition to being configured to transmit to the pulley, the movable sheave is moved forward and backward toward the fixed sheave to change the belt winding position in the radial direction of each pulley so that the gear ratio can be changed. With respect to the belt type continuously variable transmission, in the return spring provided to ensure the clamping pressure of the sheave against the belt in at least one of the driving side pulley and the driven side pulley,
Both ends in the spring axial direction are mounted immovably so that they rotate together with the pulley, the pitch of the effective winding number portion is constant, and the sheave clamping force against the belt is between the pulley and the belt. The effective number of turns at which the necessary clamping pressure or more that does not cause slippage can be obtained, and the following formula (1)
N = (a + 0.5) ± 0.15 (1)
(N is the number of effective turns of the return spring, a is an integer of 1 or more)
A return spring for a belt-type continuously variable transmission, which is formed with a minimum number of effective windings satisfying the above. In the return spring of the belt type continuously variable transmission according to claim 2,
The effective number of windings is set to an effective number of windings that does not yet reach the contact limit even when the belt winding position is located on the innermost side and the return spring is compressed by the movable sheave. A return spring for a belt-type continuously variable transmission. In the return spring of the belt type continuously variable transmission according to claim 2 or 3,
A return spring for a belt-type continuously variable transmission, which is applied to obtain a clamping pressure that does not cause a slip between a driven pulley and a belt.

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