JP2007100753A - Tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tensioner capable of preventing sticking between a rotating member and an impulsion member in a fully contracted state with a simple mechanism, and reducing the number of management manhours for assembly and securing operation during an abnormal operation. <P>SOLUTION: One shaft member 3 of a pair of shaft members 3 and 4 screwed together by screw parts 8 and 9 is rotatably urged by a spring 5, and the tensioner propels by transmission of a rotary force from the shaft member 3 of the shaft members 3 and 4 in a state of the other shaft member 4 with the rotation restrained. In the tensioner, an abutting part 20 mutually abutting the shaft members 3 and 4 by movement of the other shaft member 4 in the opposite direction from the propelling direction is provided at a part other than the screw parts 8 and 9 of the pair of shaft members 3 and 4. The contact part 20 is set to satisfy a formula R1/R2<-tan(μ2-α)/μ1 when a contact radius by abutment is R1, the effective diameter of the screw parts 8 and 9 is R2, the friction coefficient of the abutting part 20 is μ1, the friction coefficient of the screw parts 8 and 9 is μ2, and the lead angle of a screw face of the screw parts 8 and 9 is α. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a tensioner for adjusting the tension of an endless belt or chain so as to keep it constant.

  The tensioner, for example, pushes a timing chain or timing belt used in an engine of a motor vehicle such as a two-wheeled vehicle with a predetermined force, and acts to keep the tension constant when the tension or the slack occurs in these. .

  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 and 210 and a crank sprocket 220 are arranged inside the engine body 200, and a timing chain 230 is stretched between the sprockets 210, 210 and 220 in an endless manner. Yes. 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 bolts 270. 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, and FIG. 8 is an action model diagram for schematically explaining a state in which the propulsion shaft approaches and contacts the rotating shaft.
As shown in FIG. 7, the tensioner 100 includes a rotation 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 rotation shaft 120 to rotate in one direction. It is housed and restrains the rotation of the propulsion shaft 130 to convert the rotational biasing force of the torsion spring 150 into the propulsion force of the propulsion shaft 130. As shown in FIG. 6, the flange portion 112 of the case 110 is attached to the attachment surface 250 of the engine body 200 with bolts 270.

  In the tensioner 100 having the above-described structure, the propulsion shaft 130 penetrating the flat plate-shaped bearing 160 fixed in a state of being rotationally stopped at the tip portion of the case 110 is formed into a noncircular cross-sectional shape together with the through-hole 161 of the bearing 160. As a result, the rotation is constrained to the case 110, so that the rotating shaft 120 is rotated by the urging force of the torsion spring 150, and this rotating force is converted into the propulsive force of the propulsion shaft 130. 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 received load due to vibration from the engine body 200 is input to the propelling member 130. On the other hand, as 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 rotating shaft 120. When the static load is applied, the friction coefficient of the sliding surface is large, and the propelling member 130 does not come out or return. However, when the received load due to vibration from the engine body 200 is input to the propulsion member 130, the friction coefficient of the sliding surface is lowered by switching from static friction to dynamic friction, and the propulsion member 130 is retracted downward in the figure, and the rotating member 120 is rotated. For example, rightward rotation and compression of the torsion spring 150 are performed simultaneously and sequentially, so that 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 normally fluctuates due to engine vibration, and the allowance dimension A of the propulsion shaft 130 also varies.

  Here, the action of the tensioner 100 will be described with reference to the action model diagram of FIG. 8. The movable range of the propulsion member 130 is the position (A0) where the rear end 132 of the propulsion member 130 and the step 122 of the rotating member 120 contact. ) To a position (A3) where a rear end outer surface step (not shown) of the propelling member 130 (see reference numeral 133 in FIG. 9 described later) and the rear end surface of the bearing member 160 come into contact. The propelling member 130 always tries to advance in the propelling direction via the rotating member 120 by the rotational force of the torsion spring 150. Therefore, when the propelling member 130 is attached to the engine main body 200, the propelling member 130 receives a vibration load from the engine main body 200, performs an appropriate return operation, and operates at a position (A2) that keeps the tension of the timing chain 230 properly. . Here, A (FIG. 7) and A <b> 0 to A <b> 3 are the allowance dimensions from the mounting surface of the flange portion 112 of the case 110 to the tip of the cap 180.

  By the way, the propulsion member 130 attached to the engine main body 200 operates at the position A2 in normal use. However, when the load received from the engine becomes excessive, or the propulsion member 120 moves in the direction in which the propulsion member moves backward. In the case of artificial rotation, 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 are fixed, and the propelling member 130 comes out even when the load received from the engine decreases. There was a problem that a situation where it was impossible (progressed forward) occurred. This is because, when the degree of fixing of the contact portion of the rotating member 120 and the propelling member 130 other than the threaded portion is strong, the fixing cannot be released by the rotational torque of the torsion spring 150, and the propelling member 130 is at point A0. This is because a phenomenon occurs in which the propelling member 130 cannot be moved out due to the fixed state.

  On the other hand, at the time of setting to attach the tensioner 100 to the engine body 200, the rotating member 120 is rotated by a clasp member (winding jig) (not shown) or the like so that the position of the propelling member 130 is A1 (a position retracted from A2). It is fixed. At this time, if the propulsion member 130 is in contact with the rotation member 120 and the propulsion member 130 at a portion other than the threaded portion (hereinafter, simply referred to as “contact” unless otherwise specified), the stopper is attached. Even if the rear clasp member attached to the engine main body 200 is removed and the rotation member 120 is fixed, the torsion spring 150 is still applied if the contact portion of the portion other than the screw portion is strongly fixed. It is also conceivable that the sticking cannot be released with this rotational torque and the propelling member 130 cannot be operated. For this reason, when setting the tensioner to the engine body, it is necessary to consider that the position of the propelling member 130 does not become the position of A0 where the rotating member 120 abuts.

  Here, a description will be given of the results of examination by the inventor on the sticking phenomenon of the abutting portion (hereinafter simply referred to as “abutting portion”) other than the screw portion between the rotating member 120 and the propelling member 130. FIG. 9 is a mechanical model diagram of the contact portion fixing phenomenon between the rotating member step portion 122 and the propelling member rear end portion 132, and 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. It is a model figure.

  The phenomenon that the propelling member 130 and the rotating member 120 adhere at the point A0 occurs for the following reason. After the rotating member step portion 122 and the propelling member rear end portion 132 are in contact with each other, when the rotating member 120 is further rotated with the torque T in the direction in which the propelling member 130 is retracted, the propelling member 130 has an axial force F (downward direction in the drawing). ) To the rotating member step 122. At this time, a friction torque Tm is generated at the rear end 132 of the propelling member 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.

  On the other hand, in the screw parts 121 and 131, 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). At this time, if the lead angle α of the screw surface is larger than the friction coefficient μ2 of the screw contact portion, the rotational torque Tn is generated in the direction in which the propelling member 130 is actuated (promoted upward in the drawing). As shown in FIG. 10, when the rotating member 120 is opened with the propelling member 130 constrained, the rotating member 120 rotates and falls by its own weight. The friction coefficient μ2 is expressed as a friction angle θ2 in terms of angle, and is represented by a relationship of tan θ2 = μ2.

At this time, if the rotational torque Tn exceeds the friction torque Tm, it does not adhere. That is, when this relationship is expressed by a mathematical formula,
・ If not fixed;
Tm + Tn <0 Formula (101)
・ If sticking;
Tm + Tn> 0 Formula (102)
It becomes.

Here, it is as follows when the relationship of the force of the said part of the tensioner 100 is represented.
The contact radius of the contact portion between the propulsion member rear end 132 and the rotating member step portion 122 is R1, the screw contact radius (effective radius) is R2, and 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 μ1, and the lead angle (value on R2) of the screw (usually square screw) surface is α,
・ Axial force F is;
F = T / (R2 · tan (μ2 + α)) (103)
The friction torque (braking torque) Tm generated at the rear end of the propelling member is;
Tm = F · R1 · μ1 (104)
-The rotational torque Tn generated in the thread is:
Tn = F · R2 · tan (μ2−α) (105)
It is expressed. Note that the friction coefficient μ1 is expressed as a friction angle θ1 in terms of an angle, and is represented by a relationship of tan θ1 = μ1.

The relationship in which the contact portion between the propelling member rear end 132 and the rotating member step portion 122 does not adhere is established in the following case.
Since Tm + Tn <0,
F · R1 · μ1 + F · R2 · tan (μ2−α) <0 Formula (106)
It can be seen that the magnitude of the axial force F becomes irrelevant when both terms of the equation (106) are divided by F.
That is,
R1 · μ1 + R2 · tan (μ2−α) <0 Formula (107)
Therefore,
R1 / R2 <−tan (μ2−α) / μ1 Formula (108)
It becomes.

  -Tan (μ2−α) / μ1 on the right side of the equation (108) is a fixed boundary line, that is, in the range of “R1 / R2 value <fixed limit line”, the propulsion member rear end 132 and the rotating member stepped portion 122. The abutting part is not fixed. That is, Expression (108) is a condition that prevents the contact portion from being fixed.

On the other hand, in the conventional tensioner, as shown in FIGS. 7 to 9, the contact radius R1 of the abutting portion between the propulsion member rear end 132 and the rotating member step 122 is larger than the screw contact radius R2 (R1> R2). R1 / R2>1> −tan (μ2−α) / μ1 and therefore the expression (108) cannot be satisfied, and therefore the abutting portion is easily fixed. It was.
International Publication WO00 / 61968

  In view of this situation, in recent years, there has been a strong demand for the appearance of a tensioner having a structure that does not stick when the rotating member 120 and the propelling member 130 come into contact with each other, from the viewpoint of reducing the man-hours required for assembling and failsafe.

  The present invention has been made to meet such demands, and prevents the rotation member and the propelling member from sticking to each other in a fully contracted state with a simple mechanism, thereby reducing the number of management man-hours during assembly and strengthening the engine. It is an object of the present invention to provide a tensioner capable of ensuring operation (fail safe) during abnormal operation (over-behavior) such as input vibration load.

In order to achieve the above object, the tensioner according to the first aspect of the present invention is a state in which one shaft member of the pair of shaft members screwed together by the threaded portion is rotationally biased by the spring and the other shaft member is rotationally restrained. In a tensioner that is propelled by transmission of rotational force from one shaft member, a contact portion that abuts each other by movement of the other shaft member in the anti-propulsion direction is a portion other than the screw portion in the pair of shaft members. The contact portion has a contact radius R1 by contact, an effective diameter of the screw portion R2, a friction coefficient of the contact portion by contact μ1, a friction coefficient of the screw portion μ2, When the lead angle of the thread surface of the thread portion is α, it is set so as to satisfy the following formula (1).
R1 / R2 <-tan (μ2-α) / μ1 (1)

  A second aspect of the invention is the tensioner according to the first aspect, wherein the contact portion has a pointed shape or a curved shape toward the shaft member of the contact partner.

  The invention according to 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 abutting portion is a tip member or / And provided in the opposing surface of one shaft member.

  A fourth aspect of the invention is the tensioner according to the first aspect, wherein the contact portion is a bearing member arranged between the pair of shaft members and having a small apparent friction coefficient.

  According to the first aspect of the present invention, since the contact portions of the pair of shaft members are set so as to satisfy the expression (1), the friction torque Tm = F · R1 · μ1 generated at the contact portion ( Since the expression (104)) can be made smaller than the rotational torque Tn = F · R2 · tan (μ2−α) (expression (105)) generated in the threaded portion, the contact of the pair of shaft members in the fully contracted state It is possible to ensure the prevention of sticking of the part. In addition, there is an excellent effect that the operation can be ensured (fail safe) without causing the contact portion fixing phenomenon of the pair of shaft members even during abnormal operation (over-behavior) such as strong input vibration load from the engine.

  According to the invention of claim 2, in addition to having the same effect as that of the invention of claim 1, the contact portions of the pair of shaft members are pointed or curved toward the shaft member of the contact partner. Therefore, 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.

  According to the invention of claim 3, in addition to having the same effect as that of the invention of claim 1 or 2, the tip-shaped contact portion that can be formed minutely is a tip member and / or one shaft. Since it is provided on the opposing surface of the member, it is possible to form a tensioner with a simple and compact structure that reliably satisfies the formula (1), which is a condition for preventing the contact portion from being fixed.

  According to the invention of claim 4, in addition to having the same effect as that of the invention of claim 1, the abutment portion is a bearing member having a small apparent friction coefficient disposed between a pair of shaft members. Therefore, the tensioner can be improved in reliability so as to surely satisfy the expression (1) which is a condition for preventing the contact portion from being fixed.

  Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments. In addition, in each embodiment, the member which has the same function is attached | subjected and matched with the same code | symbol. In this embodiment, in order to prevent the abutting portions of the pair of shaft members from sticking, the arrangement of the tensioners is configured so as not to cause a problem by adding the minimum number of parts.

(Embodiment 1)
FIG. 1 is a longitudinal sectional view showing a tensioner according to Embodiment 1 of the present invention, and FIG. 2 is a longitudinal sectional view in the fully contracted state. The tensioner according to this embodiment is roughly constituted by 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 have substantially the same configuration as the conventional tensioner shown in FIG.

  The case 2 is generally formed 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 distal end portion. 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. At the time of attachment to the engine body, the front end surface of the flange portion 2b abuts on the attachment surface 250 of the engine body 200, as in FIG.

  A tip member 10 made of a cap 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. When the second shaft member 4 moves backward, the back surface of the tip member 10 comes into contact with the contact portion 20 at the tip of the first shaft member 3. The first shaft member 3 is rotated by being biased by a later-described torsion spring 5, and the second shaft member is restricted in rotation by a later-described bearing 6 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 drawing) that are integrally formed in the axial direction, and an outer periphery of the screw shaft portion 3b on the distal end side. Is formed with a male screw 8. Further, the base end portion of the shaft portion 3a on the base end side comes into contact with a receiving seat 19 provided in the case 2 so that its rotation is supported. Further, a slit 3e into which a distal end of a winding 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 a jig hole 2e formed in the base end surface of the body 2a of the case 2, and the distal end of the winding jig is inserted into the slit 3e from the jig hole 2e, and the first through the slit 3e. By rotating the shaft member 3, a later-described torsion spring 5 can be wound.

  The second shaft member 4 is formed with a cylindrical portion 4b that opens at the tip in the axial direction (upward in the drawing), and the internal thread of the first shaft member 3 is screwed into the inner surface of the base end portion 4a. 9 is formed. The shaft members 3 and 4 are inserted into the housing hole 2c of the case 2 in a state where the male screw 8 and the female screw 9 are screwed together. A tip member 10 made of a cap is attached to the tip of the cylindrical portion 4 b of the second shaft member 4. 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 a tubular portion in a state of being fitted on the tip portion of the tubular portion 4b of the second shaft member 4. It is fixed in a 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. A hook portion 5a on one end side (tip side) of the torsion spring 5 is inserted and locked in a hook groove 2f formed on the case 2, while a hook portion 5b on the other end side (base end side) is the first. The shaft member 3 is inserted and locked into the slit 3e on the base end surface (bottom). Therefore, the first shaft member 3 can be rotated by winding 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. As shown in FIG. 1B, 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 shape, a D cut, a parallel cut, or any other non-circular shape. Thus, the rotation of the second shaft member 4 is restricted.

  The bearing 6 is formed into a flat plate shape with a predetermined thickness. For example, a plurality of fixed pieces 6b are radially formed on the outer peripheral side as in the conventional case. The fixed piece 6b is fitted into a notch groove 2g formed at the tip of the case 2, so that 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 to the second shaft member 4 via male and female screws 9 and 8, and the rotational force of the first shaft member 3 that rotates by the rotational biasing force of the torsion spring 5 is provided. Is transmitted to the second shaft member 4, but since the second shaft member 4 is rotationally restrained by the bearing 6, the second shaft member 4 obtains a propulsive force and moves forward and backward in the axial direction with respect to the case 2. To do.

  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. In this case, a flange-shaped stepped portion 3c having a large diameter is formed at the boundary portion between the shaft portion 3a and the screw shaft portion 3b in the first shaft member 3, and the base end portion 7a of the spacer 7 has a base end portion 7a. It contacts the step 3c. The tip 7b of the spacer 7 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. Yes.

  In addition to the above, in this embodiment, a contact portion 20 having a pointed shape such as a conical shape is formed at the center of the distal end surface of the second shaft member 3, as shown in FIG. Furthermore, 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 (A0 position). At this time, the rear end 4f of the second shaft member 4 is not in contact with the step portion 3c of the first shaft member 3 and has a slight gap, and the second shaft member 4 is structurally a case 2. It does not retreat from the allowance dimension A0 from the flange 2b mounting surface to the tip of the tip member 10. The contact radius R1 such as point contact is extremely small between the back surface 10c of the tip member 10 and the pointed contact portion 20, and the contact portion 20 does not adhere to the tip member back surface 10c.

  This is to satisfy the above formula (108), which is a condition that the contact portion does not adhere, and will be specifically described below.

  In FIG. 11, the horizontal axis represents the screw lead angle α, and the vertical axis represents the ratio (contact radius R1 of the contact portion) / (contact radius R2 of the screw). The friction coefficient μ1 of the contact portion and the friction coefficient μ2 of the screw portion = An example of a fixed boundary diagram in which the value of −tan (μ2−α) / μ1 at 0.15 is indicated by a solid line (= fixed boundary line), FIG. 12 shows a change in the friction coefficient μ (= μ1 = μ2). It is the fixation boundary line figure which showed the fixation boundary line in the case. Here, the thread portion refers to the female screw portion 8 and the male screw portion 9. 11 and 12 indicate that the contact portion is fixed if the R1 / R2 value is above the fixing boundary, and the contact portion is not fixed if the R1 / R2 value is lower. In addition, it cannot be overemphasized that the negative value of a vertical axis | shaft (R1 / R2) does not actually exist in FIG. 11, FIG. This is clear from R1 being 0 or more.

Tensioner model examples 1 to 3 plotted in FIG. 11 are set as follows. The friction coefficient μ1 between the back surface 10c of the tip member 10 and the contact part 20 and the friction coefficient μ2 of the contact part in the screw parts 8 and 9 are both 0.15, the contact radius R1 of the contact part 20, the screw parts 8 and 9 The contact radius R2 and the lead angle α of the threaded portions 8 and 9 are
Model Example 1: R1 = 6.0 mm, R2 = 5.0 mm, α = 12 °,
Model Example 2: R1 = 0 mm, R2 = 3.5 mm, α = 10 °,
Model example 3: R1 = 1.0 mm, R2 = 3.5 mm, α = 14 °
It is.
It can be seen that Model Example 1 is in the range above the fixed boundary line and is fixed, and Model Examples 2 and 3 are in the range below the fixed boundary line and are not fixed. That is, when the value of R1 is small, the R1 / R2 value is small, and it is understood that the possibility of being located in the lower region of the fixed boundary line is increased.

  Thus, in the fully contracted state (A0 in FIG. 2), by setting the contact radius R1 of the contact portion 20 of the second shaft member 3 and the first shaft member 3 to be small, that is, FIGS. By setting like the pointed contact portion 20, it is possible to provide a tensioner in which the contact portion 20 does not stick. Furthermore, the curvature radius R1 of the contact part 20 can be made smaller by using the curved surface shape including the tip shape and the spherical surface shown in FIGS.

Note that the formula (108) in the above formula is a formula for a square screw. On the other hand, for screws such as trapezoidal screws and metric screws, the following component force calculation is required.
In the case of a metric screw, the tan μ2 portion of the equation (108) changes. That is, tan μ2 for a square screw, but tan μ2 ′ for a metric screw, and tan μ2 ′ = μ2 / cos β. Here, β is a flank angle in a cross section perpendicular to the thread, and in the case of a metric thread, β is calculated as 30 ° (half of the thread angle of 60 °). When the flank angle is small, such as a 30 ° trapezoidal screw (β = 15 °) or a metric screw (β = 30 °), the value in the right term of the formula (108) is not significantly different from the square screw. Even if it is calculated as equation (108), there is no significant difference in the results.

(Embodiment 2)
FIG. 3 is a longitudinal sectional view of the tensioner according to the second embodiment of the present invention.
In this embodiment, 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. However, 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 tip portion of the cylindrical portion 4b of the second shaft member 4, and the leg portion 10b ′ is the tip of the cylindrical portion 4b. In a state of being fitted in the parts, the spring pins 11 are press-fitted into these parts to be prevented from being detached and fixed to the cylindrical part 4b. A pointed 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 the second shaft member 4 is fully contracted (A0 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 is not in contact with the step portion 3c of the first shaft member 3, and has a slight gap, and the second shaft member 4 has an allowance dimension A0. No further retreat from.

  Also in the second embodiment, the tip surface of the first shaft member 3 and the pointed contact portion 20 ′ have a very small contact radius R1 such as a point contact, and the condition (108 that prevents the contact portion from being fixed). ) Does not adhere to the distal end surface of the first shaft member 3.

  As described above, in the first and second embodiments, a simple tip-shaped contact portion 20 or 20 ′ is simply and compactly provided only at the center portion of the opposing surface of the first shaft member 3 or the tip member 10 ′. With such a structure, the tensioner can surely satisfy the conditional expression (108) for preventing the contact portion from being fixed.

(Embodiment 3)
FIG. 4 is a longitudinal sectional view showing a tensioner according to Embodiment 3 of the present invention. In this embodiment, 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 3c of the first shaft member 3 are removed. A bearing member 30 such as a thrust bearing is provided between them, and the other configuration is basically the same as that of the second embodiment.

  Therefore, 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 (A0 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 further extends from the allowance dimension A0. There is no retreat.

  In the third embodiment, a bearing member 30 is a contact portion instead of the pointed contact portions 20 and 20 ′ in the first and second embodiments. When the bearing member 30 is a thrust bearing, for example, the rolling resistance (apparent coefficient of friction μ1) is usually about 0.001, so that the friction torque (braking torque) Tm generated in the bearing member 30 is as described above. Since the rotational torque Tn generated in the screws 8 and 9 can be made sufficiently smaller, the conditional expression (108) in which the contact portion is not fixed is sufficiently satisfied, and the bearing member 30 as the contact portion is not fixed.

  In FIG. 13, the horizontal axis represents the screw lead angle α, and the vertical axis represents the ratio (ball bearing radius R1) / (screw contact radius R2), and −tan when μ1 = 0.001 and μ2 = 0.15. The fixed boundary diagram which showed the value of ((mu) 2- (alpha)) / (micro | micron | mu) 1 with the continuous line (= fixed boundary line) is shown.

  The tensioner model example 4 plotted in FIG. 13 is set as follows. That is, R1 = 6 mm, R2 = 4.5 mm, μ1 = 0.001, μ2 = 0.15, and α = 12 °. This model example 4 is in a range considerably below the fixing boundary line, and it can be seen that it does not fix at all.

  Thus, it can be seen that by using the bearing member 30 having a small apparent friction coefficient μ1, the bearing contact (spherical array, etc.) radius R1 value does not stick even if it is considerably large. That is, the tensioner can be configured so as to surely satisfy the condition (108) for preventing the contact portion from sticking. The radius of the bearing (such as the sphere arrangement radius) can be arbitrarily changed, but the space that can be installed is limited, and therefore, in general settings, about 1 to 3 times slightly larger than the screw radius is appropriate.

(Embodiment 4)
FIG. 5 is a longitudinal sectional view showing a tensioner according to Embodiment 4 of the present invention. In this embodiment, 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 second embodiment shown in FIG. And basically the same.

  The compression spring 40 is disposed between the upper portion of the step portion 3 c of the first shaft member 3 and the rear end 4 f of the base end portion 4 a of the second shaft member 4. As the compression spring 40, a coil spring having hook portions at both ends as free ends is used. The compression spring 40 made of a coil spring has a distal end portion 40 a in contact with the second shaft member 4, and a proximal end portion 40 b in contact with the first shaft member 3. In this case, 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. Such a compression spring 40 is incorporated 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.

  As described above, by adding the compression spring 40, the second shaft member 4 is pressed in the axial direction of the distal end side of the screw shaft portion 3 b in the first shaft member 3. As a result, a resistance torque due to the compression force of the compression spring 40 is applied to the first shaft member 3.

  Therefore, when an external input load that pushes in the second shaft member 4 is input, the second shaft member 4 is pushed into the step 3c side of the first shaft member 3 as the first shaft member 3 rotates. In rare cases, the compression spring 40 is compressed by the compression force acting directly on the compression spring 40 in which the distal end portion 40 a is in contact with the second shaft member 4. Since the compression spring 40 is in contact with the first shaft member 3 at the other end 40b, the compression spring 40 compresses the resistance torque caused by friction between the compression spring 40 and the first shaft member 3. To be added. As a result, a strong braking force acts on the first shaft member 3 and the rotation of the first shaft member 3 is strongly braked, 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 3 e serves as a support seat that supports the base end portion 40 b of the compression spring 40. Further, 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. In addition, since the 1st shaft member 3 rotates relatively with respect to the compression spring 40 between the base end part 40b of the compression spring 40, and the upper surface 3f of the small diameter part 3d of the 1st shaft member 3, It is desirable to sandwich a metal washer as a buffer plate or a friction plate (not shown).

  Also in this embodiment, the contact radius R1 such as a point contact is extremely small between the tip surface of the first shaft member 3 and the pointed contact part 20 ′, and the contact part is fixed by the conditional expression (108). Satisfied. For this reason, the contact portion 20 ′ does not adhere to the distal end surface of the first shaft member 3.

  The tensioner of the above embodiment has a feature different from the conventional product in which the contact portion is in contact (contact) without being fixed only when the allowance dimension in the fully compressed state is A0. Yes. And in the allowance dimension (equivalent to A2-A3 of FIG. 4) of A0 or more, it is the same function as the conventional tensioner.

  In the present invention, combinations other than those shown in FIGS. 1 to 5 can be freely set, and the case 2, the first and second shaft members 3, 4 and other components are arbitrarily shaped. A new effect of preventing sticking of the abutting portion with a simple structure can be obtained by changing the combination or changing the combination. In addition, with regard to the torsion spring 5 and the compression spring 40 as well, the size and shape of the spring member including the diameter can be arbitrarily changed, whereby the spring torque or the resistance torque due to the compression force can be arbitrarily adjusted. it can. Further, the compression spring 40 can be optionally applied as a coil spring, a disc spring, a rubber molded body, a resin molded body, or the like, or the torsion spring 5 can be applied as a coil spring, a plate spring, or the like.

(A) is a longitudinal cross-sectional view which shows the tensioner of Embodiment 1 of this invention, (b) is a top view of (a). It is a longitudinal cross-sectional view in the fully contracted state of the tensioner of Embodiment 1. It is a longitudinal cross-sectional view which shows the tensioner of Embodiment 2 of this invention. It is a longitudinal cross-sectional view which shows the tensioner of Embodiment 3 of this invention. It is a longitudinal cross-sectional view which shows the tensioner of Embodiment 4 of this invention. It is a layout figure of the state which mounted | wore the engine main body with the tensioner. It is a longitudinal cross-sectional view which shows the conventional tensioner. FIG. 8 is an action model diagram for schematically explaining a state in which the propulsion shaft of the tensioner in FIG. 7 approaches and contacts the rotating shaft. It is a dynamic model figure of the contact part adhering phenomenon of the rotation member step part and propulsion member rear end part of the tensioner of FIG. It is a model figure for demonstrating the dead weight fall phenomenon of a rotating member from the propulsion member which the tensioner of FIG. 7 screws. It is an example of the fixed boundary diagram of the contact part of the rotation member of a tensioner, and a propulsion member. It is a fixed boundary line when the friction coefficient of the contact portion between the rotating member of the tensioner and the propelling member changes. It is another example of the fixed boundary diagram of the contact part of the rotation member of a tensioner, and a propulsion member.

Explanation of symbols

2 Case 3 First shaft member (one shaft member)
4 Second shaft member (the other shaft member)
4a Base end portion 5 Torsion spring 10, 10 'Tip member (cap)
20 (pointed tip) contact portion 30 bearing member 40 compression spring

Claims (4)

In a tensioner that is propelled by transmission of rotational force from one shaft member in a state in which one shaft member in a pair of shaft members screwed by a threaded portion is rotationally biased by a spring and the other shaft member is rotationally restrained,
Contact portions that contact each other by movement of the other shaft member in the anti-propulsion direction are provided in a portion other than the screw portion in the pair of shaft members,
The contact portion has a contact radius R1 by contact, an effective diameter of the screw portion R2, a friction coefficient of the contact portion by contact μ1, a friction coefficient of the screw portion μ2, and a screw surface of the screw portion. A tensioner that is set to satisfy the following formula (1) when the lead angle is α.
R1 / R2 <-tan (μ2-α) / μ1 (1)   2. The tensioner according to claim 1, wherein the contact portion has a tip shape or a curved surface shape toward the shaft member of the contact partner. A tip member is provided at a tip portion in the propulsion direction of the other shaft member,
3. The tensioner according to claim 1, wherein the contact portion is provided on a facing surface of the tip member and / or one of the shaft members.   2. 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.

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