Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16H—GEARING
  • F16H7/00—Gearings for conveying rotary motion by endless flexible members
  • F16H7/08—Means for varying tension of belts, ropes, or chains
  • F16H7/0848—Means for varying tension of belts, ropes, or chains with means for impeding reverse motion
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16H—GEARING
  • F16H7/00—Gearings for conveying rotary motion by endless flexible members
  • F16H7/08—Means for varying tension of belts, ropes, or chains
  • F16H2007/0802—Actuators for final output members
  • F16H2007/0806—Compression coil springs
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16H—GEARING
  • F16H7/00—Gearings for conveying rotary motion by endless flexible members
  • F16H7/08—Means for varying tension of belts, ropes, or chains
  • F16H2007/0802—Actuators for final output members
  • F16H2007/081—Torsion springs
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16H—GEARING
  • F16H7/00—Gearings for conveying rotary motion by endless flexible members
  • F16H7/08—Means for varying tension of belts, ropes, or chains
  • F16H7/0848—Means for varying tension of belts, ropes, or chains with means for impeding reverse motion
  • F16H2007/0857—Screw mechanisms

Definitions

• the present invention relates to a tensioner that adjusts an endless belt or chain so as to keep the tension constant.
• a tensioner for example, pushes a timing chain or a timing belt used in an engine of a motor vehicle such as a two-wheeled vehicle with a predetermined force, and when the tension or elongation occurs in these, the tension is kept constant. Acts to keep.
• FIG. 6 is a layout diagram showing a state in which the tensioner 100 is mounted on the engine body 200 of the automobile.
• a pair of cam sprockets 210, 210 and a crank sprocket 220 are arranged, and the timing chain 230 is stretched between these sprockets 210, 210, 220 in an endless manner.
• a chain guide 240 is swingably disposed on the moving path of the timing chain 230, and the timing chain 230 slides on the chain guide 240! /.
• a mounting surface 250 is formed on the engine body 200, and the tensioner 100 is fixed to the mounting surface 250 by 270 bolts. Note that lubricating oil (not shown) is sealed inside the engine body 200.
• FIG. 7 is a longitudinal sectional view of a conventional general tensioner
• FIG. 8 is an action model diagram for schematically explaining a state in which the propulsion shaft in the action approaches and contacts the rotating shaft.
• the tensioner 100 includes a rotating shaft 120 and a propulsion shaft 130 that are screwed together by a female screw portion 121 and a male screw portion 131, and a torsion spring 150 that urges the rotating shaft 120 to rotate in one direction. And the rotation urging force of the torsion spring 150 is converted into the propulsion force of the propulsion shaft 130 by restricting the rotation of the propulsion shaft 130.
• the flange 110 of the case 110 is attached to the mounting surface 250 of the engine body 200 by the Bonole 270.
• the propulsion shaft 130 that penetrates the flat plate-shaped bearing 160 fixed in a state of being prevented from rotating at the tip of the case 110 has a non-circular cross section together with the through-hole 161 of the bearing 160 Since the rotation is constrained to the case 110 by being formed into a shape, the rotating shaft 120 is rotated by the biasing force of the torsion spring 150, and this rotational force is converted into the propulsive force of the propulsion shaft 130. The shaft 130 advances. Therefore, the propulsion shaft 130 can apply tension to the timing chain 230 by pressing the timing chain 230 via the cap 180 and the chain guide 240 as shown in FIG.
• a load received by vibration from engine body 200 is input to propulsion member 130.
• the reaction force a balance is established between the spring force of the torsion spring 150 and the sliding surface frictional resistance of the screw portions 121 and 131 and the lower end surface portion of the rotary shaft 120.
• the propulsion member 130 having a large friction coefficient on the sliding surface does not come out or return.
• the friction coefficient of the sliding surface decreases due to switching to the static frictional force dynamic friction, and the propulsion member 130 moves backward and rotates in the illustrated direction.
• the propulsion shaft 130 finally returns to a position where the forces are balanced.
• the load received by the tensioner 100 via the chain guide 240 shown in FIG. 6 is a vibration load that usually fluctuates due to the vibration of the engine, and the allowance dimension A of the propulsion shaft 130 also fluctuates.
• the movable range of the propulsion member 130 is that the rear end 132 of the propulsion member 130 and the step portion 122 of the rotation member 120. Is from the position (AO) where the thrust member contacts the rear end surface step (not shown) of the propelling member 130 (see reference numeral 133 in FIG. 9 described later) and the position (A3) where the rear end surface of the bearing member 160 contacts.
• the propulsion member 130 always tries to advance in the propulsion direction through the rotating member 120 by the rotational force of the torsion spring 150.
• the propelling member 130 when the propelling member 130 is attached to the engine main body 200, the propelling member 130 receives the vibration load from the engine main body 200, and appropriately moves back and forth, and operates at a position (A2) where the tension of the timing chain 230 is properly maintained.
• a (Fig. 7) A0 ⁇ A3 is a projecting dimension from the flange 112 mounting surface of the case 110 to the tip of the cap 180, respectively.
• the propulsion member 130 attached to the engine body 200 operates at the position A2 in normal use.
• the load received by the engine force becomes excessive, or the propulsion member moves backward.
• the rotating member 120 is artificially rotated, the stepped portion 122 of the rotating member 120 and the rear end 132 of the propelling member 130 come into contact with each other, and the load received by the engine force decreases.
• the propulsion member 130 could not move out (progress forward). This is because, if the degree of adhesion of the abutting portion of the rotating member 120 and the propulsion member 130 other than the threaded portion is strong! /, The fixing torque cannot be released with the rotational torque of the torsion spring 150. This is because the propulsion member 130 is fixed at the AO point, and the propulsion member 130 becomes unable to operate.
• FIG. 9 is a mechanical model diagram of the contact portion fixing phenomenon between the rotating member step portion 122 and the propulsion member rear end portion 132.
• FIG. 10 is a diagram for explaining the self-weight falling phenomenon of the rotating member 120 from the propelling member 130 to be screwed together. This is a model diagram.
• the phenomenon that the propelling member 130 and the rotating member 120 adhere at the AO point is as follows. It occurs more. After the rotating member step 122 and the propulsion member rear end 132 contact each other, when the rotating member 120 is further rotated by the torque T in the direction in which the propelling member 130 is retracted, the propelling member 130 has an axial force F (downward in the figure). The force is pressed against the rotating member step 122. At this time, a friction torque Tm is generated at the propulsion member rear end 132 due to the axial force F, and when T is released, it acts as a counter-rotation (braking or resistance) torque that stops the rotation of the rotating member 120.
• the propelling member 130 is pressed against the screw back surface of the rotating member 120 by the axial force F (upward force in the drawing).
• F upward force in the drawing
• a rotational torque ⁇ is generated in the direction in which the propelling member 130 is actuated (promoted upward in the drawing).
• the contact radius of the contact portion between the propulsion member rear end 132 and the rotating member step 122 is Rl
• the screw contact radius (effective radius) is R2
• the friction of the contact portion between the propulsion member rear end 132 and the rotation member step portion is R2. If the coefficient is ⁇ 1, and the lead angle (value on R2) of the screw (usually square screw) surface is
• Friction torque (braking torque) Tm generated at the rear end of the propulsion member
• Tm F-Rl- ⁇ 1 ⁇ Formula (104)
• the contact radius R1 of the contact portion between the propulsion member rear end 132 and the rotating member step 122 is larger than the contact radius R2 of the screw. (R1> R2), and R1 / R2> 1> —tan (2-a) / ⁇ 1, so the formula (108) cannot be satisfied. It was easy to do.
• Patent Document 1 International Publication WO00Z61968
• the present invention has been made in order to meet such demands, and with a simple mechanism, the rotating member and the propelling member are prevented from sticking in the fully contracted state, thereby reducing the management man-hours during assembly.
• the purpose is to provide a tensioner that can ensure operation (fail safe) during abnormal operation (over-behavior) such as strength from the engine and input vibration load.
• one shaft member of the pair of shaft members screwed together by the screw portion is rotationally biased by the spring, and the other shaft member is rotationally restrained.
• the force in the pair of shaft members The contact portion is provided at a portion other than the screw portion, and the contact portion has a contact radius Rl by contact, an effective diameter of the screw portion R2, a friction coefficient of the contact portion by contact 1, and the screw portion.
• the coefficient of friction is ⁇ 2 and the lead angle of the thread surface of the thread is ⁇ , so that the following equation (1) is satisfied.
• the invention of claim 2 is the tensioner according to claim 1, wherein the abutting portion has a pointed shape or a curved shape directed toward the shaft member of the abutting partner.
• the invention of claim 3 is the tensioner according to claim 1 or 2, wherein a tip member is provided at a tip portion in the propulsion direction of the other shaft member, and the contact portion is The tip member or Z and one shaft member are provided on opposing surfaces.
• the invention of claim 4 is the tensioner according to claim 1, wherein the contact portion is a bearing member having a small apparent friction coefficient disposed between the pair of shaft members. It is characterized by.
• the contact portions of the pair of shaft members are pointed or pointed toward the shaft member of the contact partner. Because of the curved shape, the tensioner can be formed so as to surely satisfy the expression (1), which is a condition for preventing the contact portion from being fixed.
• the tip-shaped contact portion that can be formed minutely is provided with a tip member or Z and Since it is provided on the opposite surface of one of the shaft members, a tensioner that reliably satisfies equation (1), which is a condition for preventing this contact portion from sticking, should be formed with a simple and compact structure. Can do.
• the abutting portion is disposed between the pair of shaft members and has a small apparent friction coefficient. Therefore, the tensioner can be improved in reliability so as to satisfy the expression (1) which is a condition for preventing the contact portion from being fixed.
• FIG. 1 (a) is a longitudinal sectional view showing a tensioner according to Embodiment 1 of the present invention, and (b) is a plan view of (a).
• FIG. 2 is a longitudinal sectional view of the tensioner 1 of Embodiment 1 in a fully contracted state.
• FIG. 3 is a longitudinal sectional view showing a tensioner according to a second embodiment of the present invention.
• FIG. 4 is a longitudinal sectional view showing a tensioner according to Embodiment 3 of the present invention.
• FIG. 5 is a longitudinal sectional view showing a tensioner according to a fourth embodiment of the present invention.
• FIG. 6 is a layout diagram showing a state in which the tensioner 1 is mounted on the engine body.
• FIG. 7 is a longitudinal sectional view showing a conventional tensioner.
• FIG. 8 is an action model diagram for schematically explaining a state in which the propulsion shaft of the tensioner shown in FIG. 7 comes close to and abuts the rotating shaft.
• FIG. 9 is a mechanical model diagram of a contact portion fixing phenomenon between a rotating member step portion and a propulsion member rear end portion of the tensioner of FIG. [10]
• FIG. 7 is a model diagram for explaining the self-weight falling phenomenon of the rotating member of the tensioner screwed in the tensioner of FIG.
• FIG. 11 is an example of a fixed boundary diagram of a contact portion between a rotating member and a propelling member of a tensioner. ⁇ 12] This is the fixed boundary line when the friction coefficient of the contact part between the rotating member and propulsion member of the tensioner changes.
• FIG. 13 is another example of a fixed boundary diagram of the contact portion between the rotating member and the propelling member of the tensioner.
• FIG. 1 is a longitudinal sectional view showing a tensioner according to Embodiment 1 of the present invention
• FIG. 2 is a longitudinal sectional view in the fully contracted state.
• the tensioner 1 of this embodiment is roughly composed of a case 2, a first shaft member 3 that is a rotating member, a second shaft member 4 that is a propelling member, a torsion spring (elastic member) 5, a bearing 6, and a spacer 7. These are the conventional tensioner shown in Fig. 7.
• the configuration is substantially the same.
• the case 2 is roughly molded into a bottomed cylindrical shape having a flange portion 2b in the middle portion of the body portion 2a.
• a housing hole 2c extending in the axial direction (propulsion direction) is formed in the body portion 2a toward the tip.
• the front end portion of the storage hole 2c is open, and the assembly of the first and second shaft members 3, 4, the torsion spring 5, and the spacer 7 is stored in the storage hole 2c.
• the flange portion 2b of the case 2 is to be attached to the applied engine body, and is formed with an attachment hole 2d through which a bolt (not shown) screwed into the engine body passes.
• a bolt not shown
• the front end surface of the flange portion 2b comes into contact with the mounting surface 250 of the engine body 200, as in FIG.
• a tip member 10 having a cap force is attached to the tip of the second shaft member 4.
• a conical pointed contact portion 20 is formed at the center of the distal end surface of the first shaft member 3.
• the first shaft member 3 is rotated by being urged by a torsion spring 5 described later, and the second shaft member is restricted in rotation by a bearing 6 described later provided in the case 2 and is movable in the axial direction. 4 is propelled from the case 2 by the rotation of the first shaft member 3.
• the first shaft member 3 includes a shaft portion 3a on the proximal end side and a screw shaft portion 3b on the distal end side (upper side in the figure) which are integrally formed in the axial direction.
• a male screw 8 is formed on the outer periphery of the portion 3b.
• the rotation of the base end portion of the shaft portion 3a on the base end side is supported by abutting against a receiving seat 19 provided in the case 2.
• a slit 3e into which a distal end of a tightening jig (not shown) for rotating the first shaft 3 is inserted is formed on the base end surface of the shaft portion 3a.
• the slit 3e communicates with the jig hole 2e opened on the base end surface of the body 2a of the case 2.
• the tip of the clamping jig is inserted into the slit 3e from the jig hole 2e, and the slit 3e passes through the slit 3e.
• the torsion spring 5 described later can be tightened.
• the second shaft member 4 is formed with a cylindrical portion 4b that opens at the tip in the axial direction (upward in the figure).
• the male screw 8 of the first shaft member 3 is threaded on the inner surface of the base end 4a.
• a mating female screw 9 is formed.
• the tip member 10 is composed of a head portion 10a and a leg portion 10b by press molding or the like, and the lower end portion of the leg portion 10b is connected to the tip end portion of the tubular portion 4b of the second shaft member 4 while the tubular portion It is fixed in the groove 4e formed at the tip of 4b by a method such as caulking.
• the torsion spring 5 is externally inserted into the proximal end side shaft portion 3 a of the first shaft member 3.
• the hook portion 5a on one end side (tip side) of the torsion spring 5 is inserted and locked in the hook groove 2f formed on the case 2, while the hook portion 5b on the other end side (base end side)
• the first shaft member 3 is inserted and locked in the slit 3e on the base end surface (bottom). Therefore, the first shaft member 3 can be rotated by tightening the torsion spring 5 and applying torque.
• the bearing 6 is attached to the tip portion of the case 2 and is fixed by a retaining ring 13.
• the bearing 6 has a sliding hole 6a, and the second shaft member 4 passes through the sliding hole 6a.
• the inner surface of the sliding hole 6a of the bearing 6 and the outer surface of the second shaft member 4 are formed in a substantially oval cross section, D-cut or parallel cut, or any other non-circular shape.
• the rotation of the second shaft member 4 is restricted.
• the bearing 6 is formed in a flat plate shape having a predetermined thickness, and a plurality of fixed pieces 6b are formed radially on the outer peripheral side, for example, as in the prior art.
• a fixed piece 6b By fitting this fixed piece 6b into a notch groove 2g formed at the tip of the case 2, the entire bearing 6 is prevented from rotating.
• the bearing 6 is thus prevented from rotating with respect to the case 2, whereby the second shaft member 4 penetrating the bearing 6 is rotationally restrained by the case 2 via the bearing 6.
• the first shaft member 3 is screwed into the second shaft member 4 via male and female screws 9 and 8, and the first shaft member 3 is rotated by the rotational biasing force of the torsion spring 5. Is transmitted to the second shaft member 4. Since the second shaft member 4 is rotationally restrained by the bearing 6, the second shaft member 4 obtains a propulsive force and axially acts on the case 2. Move forward and backward.
• the spacer 7 has a cylindrical shape, and the screwed portions of the first shaft member 3 and the second shaft member 4 are inserted therein.
• a flange-shaped step portion 3c having a large diameter is formed at a boundary portion between the shaft portion 3a and the screw shaft portion 3b in the first shaft member 3, and the spacer 7 has a base end thereof.
• the part 7a is in contact with the step part 3c.
• Spacer 7 The front end portion 7b faces the lower surface of the bearing 6 and prevents the first and second shaft members 3 and 4 from coming out of the case 2 by contact with the bearing 6.
• a contact portion 20 having a pointed shape such as a conical shape is formed in the center portion of the distal end surface of the second shaft member 3, As shown in FIG. 2, the contact portion 20 comes into contact with the back surface of the tip member 10 when the second shaft member 4 is retracted until it is fully contracted (AO position). At this time, the rear end 4f of the second shaft member 4 has a slight gap that does not contact the step 3c of the first shaft member 3, and the second shaft member 4 is structurally Neither the flange part 2b mounting surface force nor the protruding allowance AO force to the tip of the tip member 10 will be retracted.
• the abutting portion 20 having a very small contact radius R1 such as a point contact between the back surface 10c of the tip member 10 and the pointed contact portion 20 does not adhere to the tip member back surface 10c.
• the horizontal axis represents the screw lead angle ⁇
• the vertical axis represents the ratio (contact radius R1 of the contact portion) Z (contact radius R2 of the screw).
• the threaded portion refers to the female threaded portion 8 and the male threaded portion 9.
• Tensioner model examples 1 to 3 plotted in FIG. 11 are set as follows.
• the friction coefficient 1 between the back surface 10c of the tip member 10 and the contact part 20 and the friction coefficient 2 of the contact part in the screw parts 8 and 9 are both equal to 0.15, the contact radius Rl of the contact part 20, the screw part 8 and The contact radius R2 at 9 and the lead angle of thread 8 and 9 are
• model example 1 is in the range above the fixing boundary and is fixed, and model examples 2 and 3 are in the range below the fixing boundary and are not fixed.
• R1 when the value of R1 is small, the R1 / R2 value is small, and the possibility of being located in the lower region of the fixed boundary line increases.
• Formula (108) in the above formula is a formula for a square screw.
• the following component force calculations are required for screws such as trapezoidal screws and metric screws.
• FIG. 3 is a longitudinal sectional view of the tensioner 1 according to the second embodiment of the present invention.
• the pointed contact part 20 ′ is removed from the tip surface of the first shaft member 3 in the first embodiment, and the pointed contact part 20 ′ is provided on the tip member 10 ′ side.
• the other configuration is the same as that of the first embodiment except that the shape of the tip member 10 ′ is different.
• the tip member 10 ' includes a head portion 10a' and a leg portion 10b '.
• the head portion 10a' covers the tubular portion 4b tip portion of the second shaft member 4, and the leg portion 10b 'is tubular.
• the spring pin 11 is press-fitted into the tip portion of the shape portion 4b so as to be prevented from coming off and fixed to the tubular portion 4b.
• a tip contact portion 20 ′ is provided at the center of the lower end surface of the leg portion 10b ′ of the tip member 10 ′. Therefore, when the second shaft member 4 is retracted until it is fully contracted (AO position), the contact portion 20 ′ comes into contact with the front end surface of the first shaft member 3. At this time, the rear end 4f of the second shaft member 4 has a slight gap that does not contact the step portion 3c of the first shaft member 3, and the second shaft member 4 also has an output allowance AO force. There will be no further retreat.
• the tip surface of the first shaft member 3 and the pointed contact portion 20 ' are in a condition that the contact portion with a very small contact radius R1 such as point contact is not fixed.
• the contact portion 20 ′ is not fixed to the front end surface of the first shaft member 3.
• the minute tip-pointed contact portion 20 or 20 ′ is simply provided at the center of the opposing surface of the first shaft member 3 or the tip member 10 ′.
• the tensioner can surely satisfy the conditional expression (108) for preventing the contact portion from being fixed.
• FIG. 4 is a longitudinal sectional view showing a tensioner according to Embodiment 3 of the present invention.
• the pointed contact portion 20 ′ in the tip member 10 ′ is removed from the second embodiment, and the rear end 4f of the second shaft member 4 and the step portion of the first shaft member 3 are removed.
• a bearing member 30 such as a thrust bearing is provided between 3c and other configurations are basically the same as those of the second embodiment.
• the rear end 4f of the second shaft member 4 comes into contact with the bearing member 30 when the second shaft member 4 is retracted until it is fully contracted (AO position). At this time, the back surface of the leg portion 10b 'of the tip member 10' has a slight gap without coming into contact with the tip surface of the first shaft member 3, and the second shaft member 4 has a protrusion allowance AO. There is no further retreat.
• the bearing member 30 is a contact portion instead of the pointed contact portions 20, 20 'in the first and second embodiments.
• the rolling resistance apparent coefficient of friction 1
• the friction torque braking torque generated in the bearing member 30 is as described above.
• Force Rotation torque generated at the screw 8 and 9 parts can be made sufficiently smaller than the torque Tn, so that the contact part does not stick. Since the expression (108) is sufficiently satisfied, the bearing member 30 as the contact portion does not adhere.
• This Model Example 4 is in a range considerably below the fixing boundary line, and it can be seen that it does not stick at all.
• the bearing member 30 having a small apparent friction coefficient 1 the bearing does not adhere even if the radius (R1) of the contact (spherical arrangement, etc.) is considerably large. That is, the tensioner can be configured to surely satisfy the condition (108) for preventing the contact portion from being fixed.
• the radius of the bearing (such as the sphere array radius) can be changed arbitrarily, but the space that can be installed is limited, so it is appropriate to set it to 1 to 3 times slightly larger than the screw radius.
• FIG. 5 is a longitudinal sectional view showing a tensioner according to Embodiment 4 of the present invention.
• a compression spring 40 is provided between the first shaft member 3 and the second shaft member 4 in addition to the configuration of the embodiment 2 in FIG. And basically the same
• the compression spring 40 is disposed between the upper part of the step 3c of the first shaft member 3 and the base end 4a rear end 4f of the second shaft member 4.
• a coil spring having hook portions at both ends as free ends is used.
• the front end portion 40 a abuts on the second shaft member 4, while the base end portion 40 b abuts on the first shaft member 3.
• the base end portion 40b comes into contact with the upper surface 3f of the small diameter portion 3d formed on the upper portion of the step portion 3c of the first shaft member 3.
• the compression spring 40 is assembled in a state where both end portions 40a and 40b are in contact with both shaft members 4 and 3 and are compressed to some extent.
• the second shaft member 4 becomes the first shaft member 3 Is pressed in the axial direction on the distal end side of the screw shaft portion 3b.
• a resistance torque due to the compression force of the compression spring 40 is applied to the first shaft member 3.
• the second shaft member 4 becomes the step 3c of the first shaft member 3 as the first shaft member 3 rotates.
• the compression spring 40 is compressed by the compression force acting directly on the compression spring 40 that is pushed to the side and the tip end portion 40a is in contact with the second shaft member 4. Since the other end 40b of the compression spring 40 is in contact with the first shaft member 3, resistance torque due to friction is added between the compression spring 40 and the first shaft member 3 due to compression of the compression spring 40. Added.
• a strong braking force acts on the first shaft member 3 and the rotation of the first shaft member 3 is strongly controlled, so that a strong and stable vibration damping function can be secured. .
• a small-diameter step portion 3e having an outer diameter corresponding to the inner diameter of the compression spring 40 is formed between the small-diameter portion 3d at the upper stage of the step portion 3c in the first shaft member 3 and the screw shaft portion 3b. .
• the small diameter step portion 3e serves as a support seat that supports the base end portion 40b of the compression spring 40. Then, by inserting the small diameter step portion 3e into the base end portion 40b of the compression spring 40, a more stable support state is achieved.
• the first shaft member 3 rotates relative to the compression spring 40 between the base end portion 40b of the compression spring 40 and the upper surface 3f of the small diameter portion 3d of the first shaft member 3. Not shown! It is desirable to sandwich a metal washer as a buffer plate or a friction plate.
• the contact portion where the contact radius R1 such as point contact is extremely small is between the tip surface of the first shaft member 3 and the pointed contact portion 20 '. Satisfies (108). For this reason, the contact portion 20 ′ does not adhere to the distal end surface of the first shaft member 3.
• the tensioner 1 of the above-described embodiment is different from the conventional product in which the contact portion as described above is in contact (contact) without being fixed only when the allowance dimension in the fully compressed state is AO. have. And, it has the same function as that of the conventional tensioner in the allowance dimension larger than AO (equivalent to A2 to A3 in Fig. 4).

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• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Devices For Conveying Motion By Means Of Endless Flexible Members (AREA)

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