JP2013142441A - Auto-tensioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To satisfy both of stepless tension adjustment and an arbitrary backlash amount.SOLUTION: An auto-tensioner includes a bolt member 12 stored in a cylinder chamber 11a; a nut member 13 screw-engaged with the bolt member 12; a first spring 14 interposed between the bolt member 12 and the nut member 13; a ratchet member 15 with a serration 15a engaged with a serration 12f of the bolt member 12; and a second spring 16 urging the bolt member 12 and the nut member 13 in a direction to be pushed out of the cylinder chamber 11a through the ratchet member 15.

Description

  The present invention relates to an auto tensioner used for, for example, applying appropriate tension to a chain for driving an engine camshaft.

  A ratchet type auto tensioner having a backlash has been proposed for use in a chain transmission device for driving an engine camshaft (Patent Document 1).

  A conventional ratchet-type auto tensioner has a plunger with a rack slidably housed in a cylinder chamber that is open at one end, urges the plunger in a protruding direction via a spring in the cylinder chamber, and engages with the rack. Is provided outside the cylinder chamber. The plunger can move forward and backward through a spring to keep the chain tension constant within a certain backlash range determined by the rotation angle of the ratchet, and if the plunger advances beyond the backlash amount, The engagement position of the ratchet with respect to is changed, and the plunger moves back and forth within a predetermined backlash range with reference to the new engagement position. In order to adjust the chain tension as infinitely as possible by reducing the rack pitch, and at the same time to achieve a predetermined amount of backlash, it is also proposed to appropriately set the angle and height of the rack teeth. (Patent Document 2).

Japanese Patent Laid-Open No. 10-2386 JP 2001-214957 A

  According to such a conventional technique, the rack pitch and the backlash amount cannot be set independently of each other, and the degree of freedom in design is small, and the ratchet pawl is engaged with the rack teeth to retract the plunger. Since it prevents, there was a problem that it was not easy to realize sufficient durability.

  Therefore, in view of the problems of the prior art, an object of the present invention is to provide a stepless tension adjustment and an arbitrary backlash by combining a nut member and a bolt member with a screw and a ratchet member having a radial serration. It is an object of the present invention to provide an auto tensioner that can achieve both the amount and the required and sufficient durability.

  The configuration of the invention of claim 1 according to this application for achieving the above object includes: a bolt member that is housed in a cylinder chamber that is open at one end; and a nut member that is threadedly engaged with the bolt member from the open end side of the cylinder chamber; A first spring interposed between the bolt member and the nut member; a ratchet member facing the head of the bolt member; and a first biasing member that urges the bolt member and the nut member out of the cylinder chamber via the ratchet member. The nut member and the ratchet member are slidable and non-rotatable in the cylinder chamber, respectively, and the bolt member and the ratchet member form radial serrations that mesh with each other. The gist.

  According to a second aspect of the present invention, a nut member that is housed in a cylinder chamber that is open at one end, a bolt member that is screw-engaged with the nut member from the open end side of the cylinder chamber, and the nut member and the bolt member are interposed. A first spring; a ratchet member facing the bottom of the nut member; and a second spring that urges the nut member and the bolt member in a direction to push the bolt member out of the cylinder chamber via the ratchet member. The ratchet member is slidably accommodated in the cylinder chamber and non-rotatably accommodated, and the nut member and the ratchet member are formed with radial serrations that mesh with each other.

  In the first and second aspects of the invention, the male screw of the bolt member and the female screw of the nut member can be formed to have a lead angle larger than the friction angle of the thread surface, and the radial serration is the lead angle of the male screw and female screw. It can be formed in a mountain shape with an approximate inclination angle.

  Further, the second spring can have a constant load spring characteristic, and the bolt member and the nut member can be restrained at a fixed position of the cylinder chamber via a detachable restraining member.

  According to the configuration of the invention of claim 1, the first spring is a compression spring, and urges the nut member and the bolt member in the direction in which the entire lengths of the nut member and the bolt member are extended, thereby preventing the nut member from rotating. Thus, the bolt member can be relatively rotated to project the nut member from the cylinder chamber, and the chain tension can be increased steplessly through the nut member to correct the looseness of the chain. At this time, the bolt member is opposed to the non-rotatable ratchet member facing the head via radial serrations that mesh with each other, and the axial pressing force due to the chain tension is applied to the serrations. To stop. On the other hand, even if the tension of the chain increases, the bolt member rotates only in the opposite direction until both serrations are completely brought into contact with each other, and the nut member is not pushed back excessively beyond a certain backlash. In this case, the backlash is equivalent to ½ pitch of the radial serration as the rotation amount of the bolt member, and can be arbitrarily set.

  That is, the serration of the bolt member, together with the serration of the ratchet member, realizes a ratchet structure that quickly follows the direction of correcting the looseness of the chain and does not return in the reverse direction. However, in the case of excessive tension of the chain exceeding the backlash, the second spring is compressed, and the bolt member and the nut member are pushed back together with the ratchet member to move backward. The second spring is, for example, a chain transmission device for driving a camshaft of an aluminum engine. The chain is loosened when the engine is cold and the nut member protrudes, and the engine frame is larger than the chain when the engine is warmed up after starting. This is particularly effective when the chain tension is excessive and the chain tension becomes excessive.

  According to the configuration of the invention of claim 2, the relative positional relationship between the nut member and the bolt member is changed with respect to the invention of claim 1. That is, according to the invention of claim 2, the chain tension is increased through the bolt member to correct the looseness of the chain, and the ratchet member facing the bottom of the nut member is engaged with the nut member side together. The bolt member and the ratchet member are slidably and non-rotatably accommodated in the cylinder chamber, respectively, and the operation mode as a whole is the nut member and the bolt member of the invention of claim 1. What is necessary is just to read as a bolt member and a nut member, respectively.

  In the first and second aspects of the present invention, the male screw of the bolt member and the female screw of the nut member are formed to have a lead angle larger than the friction angle of the thread surface, so that the nut is applied by the biasing force of the first spring or the tension of the chain. The member and the bolt member smoothly rotate relative to each other to expand and contract the entire length, and the chain tension fluctuation can be corrected quickly. Further, if the inclination angle of the radial serration is approximated to the lead angle of the male screw of the bolt member and the female screw of the nut member, the serration of the bolt member or the nut member is caused by the rotation of the bolt member or the nut member. Can be smoothly meshed.

  By making the second spring a non-linear spring having a constant load spring characteristic, the maximum tension of the chain can be suppressed and excessive tension can be avoided. Such non-linear characteristics include, for example, a disc spring having a ratio h / t = 1.4 to 1.6 of the plate thickness t and the maximum deflection h, or an elastic spring such as an elastic rubber having an appropriate shape. Can be realized.

  If a restraint member for restraining the bolt member and the nut member is provided, the nut member and the bolt member may be inadvertently protruded from the cylinder chamber even if the first spring is compressed by screwing the bolt member and the nut member. Assembling work can be made smooth without coming. As the restraining member, for example, a detachable pin or a small screw that engages a part of a nut member or a bolt member is preferable. In addition, in order to combine the bolt member and the nut member in the cylinder chamber by screw engagement, an engaging portion for engaging a tool such as a spanner is formed at the tip of the nut member or the bolt member protruding outside the cylinder chamber. It is preferable to prevent rotation by engaging a tool for preventing rotation with a bolt member or nut member in the cylinder chamber through a through hole formed in the closed end of the cylinder chamber.

Overall configuration longitudinal section Bolt member configuration explanatory diagram Configuration diagram of nut member Cap explanatory diagram Structure explanatory drawing of ratchet member Configuration diagram of holder Overall operation explanatory diagram equivalent to FIG. Usage diagram Main part operation explanatory drawing (1) Main part operation explanatory drawing (2) Whole structure explanatory drawing which shows other embodiment

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  The auto tensioner 10 includes a bolt member 12, a nut member 13, a first spring 14, a ratchet member 15, and a second spring 16 that are housed in a cylinder chamber 11a of the case 11 (FIG. 1).

  The case 11 has a cylinder chamber 11a that is open at one end. The cylinder chamber 11a has a circular cross section, and a through hole 11b is formed at the closed end of the cylinder chamber 11a. The case 11 is provided with oil supply holes 11c and 11c communicating with the cylinder chamber 11a, and bolt holes 11d and 11d for attachment are formed.

  The bolt member 12 is formed by attaching a circular head portion 12b to one end of a hollow shaft portion 12a (FIGS. 1 and 2). On the outer periphery of the shaft portion 12a, for example, a three-thread male screw 12c is formed. A square hole 12d is opened at the center of the head 12b, and a radial serration 12f is formed around a shallow circular counterbore 12e on the top surface of the head 12b. In the serration 12f, inclined surfaces 12f1, 12f1,... Alternately inclined in opposite directions are formed at an equal pitch, and angled inclined surfaces 12f1, 12f1,... Formed on every two adjacent surfaces are in the circumferential direction of the counterbore 12e. It is arranged. 2A and 2B are a central longitudinal sectional view of the bolt member 12 and a left side view of FIG. 2A, respectively.

  The nut member 13 is formed in a cylindrical shape with one end open (FIGS. 1 and 3), and a female screw 13 a that fits the male screw 12 c of the bolt member 12 is formed in about half of the inner peripheral open end side. 3A to 3C are an overall outline view of the nut member 13, a right side view of FIG. 3A, and a central longitudinal sectional view, respectively.

  The closed end of the nut member 13 is bulged into a loose dome shape. A shallow annular groove 13b is formed on the outer periphery of the nut member 13 slightly closer to the open end than the center, and two large and small flat cutouts 13c, 13c, 13d, and 13d are formed from the center to the closed end, respectively. Axisymmetrically formed. Therefore, a radial band-shaped protrusion 13e is formed between the notches 13d and 13d on the front end surface on the closed end side, and a small-diameter cavity 13f is formed inside the protrusion 13e. . The nut member 13 is screw-engaged with the bolt member 12 from the open end side of the cylinder chamber 11a via the female screw 13a and the male screw 12c of the bolt member 12 (FIG. 1).

  The nut member 13 is accompanied by a cap 17 for preventing rotation (FIGS. 1 and 4). 4A to 4C are a front view, a bottom view, and a central longitudinal sectional view of the cap 17, respectively.

  The cap 17 is formed in a very shallow circular dish shape. The cap 17 is formed with a large deformation hole 17a formed by a pair of symmetrical arcs and parallel straight lines, and the notches 13c and 13c of the nut member 13 can be inserted into the deformation hole 17a. In addition, a pair of axial claws 17 b and 17 b are formed on the outer edge of the cap 17 so as to be axially symmetrical. Therefore, the cap 17 is fixed by covering the open end of the cylinder chamber 11a by caulking the claws 17b, 17b, and the nut member 13 passes through the deformation hole 17a of the cap 17 and thereby is fixed to the cylinder chamber 11a. It is slidable in the axial direction and stored so that it cannot rotate relative to it.

  The first spring 14 is a compressible coil spring built in the hollow shaft portion 12 a of the bolt member 12. One end of the first spring 14 protrudes from the tip of the shaft portion 12 a and is inserted into the cavity 13 f of the nut member 13. The first spring 14 is interposed between the bolt member 12 and the nut member 13, extends the entire length of the nut member 13 and the bolt member 12, and biases the nut member 13 in a direction to push out the nut member 13 from the cylinder chamber 11 a. doing.

  The ratchet member 15 is disposed in the cylinder chamber 11a so as to face the head 12b of the bolt member 12, and has a radial serration 15a that meshes with the serration 12f on the head 12b (FIGS. 1 and 5). ). 5A to 5C are a front view, a central longitudinal sectional view, and an enlarged sectional view corresponding to the line XX in FIG. 5A, respectively, of the ratchet member 15. These are the model fragmentary enlarged views of serrations 12f and 15a on the bolt member 12 side and the ratchet member 15 side facing each other.

  The ratchet member 15 is formed in a disk shape having a pair of symmetrical short projections 15b, 15b in the radial direction. On one side of the ratchet member 15, a radial serration 15a is formed around a shallow circular counterbore 15c, and a circular hole 15d is opened at the center of the counterbore 15c. The serration 15 a of the ratchet member 15 is formed in the same shape as the serration 12 f of the bolt member 12. That is, the serration 15a is formed with inclined surfaces 15a1, 15a1,... Alternately inclined in opposite directions at an equal pitch, and the same number of sets of chevron-shaped inclined surfaces 15a1, 15a1,. ing. In the serration 15a, the inner and outer heights h1 and h2 can be set such that h2 ≧ h1 (FIG. 5C). The same applies to the serration 12f on the bolt member 12 side.

  The serrations 15a and 12f on the ratchet member 15 side and the bolt member 12 side mesh with each other when the distance d is 0 ≦ d <h2 (FIG. 5D), and do not mesh when d> h2. Therefore, the ratchet member 15 realizes a backlash corresponding to the height h2 of the serrations 15a and 12f as the axial stroke of the bolt member 12 via the serrations 15a and 12f, and the rotation amount of the bolt member 12 includes the serrations 15a and 12f. A backlash δ corresponding to ½ pitch can be realized (FIGS. 2B and 5A). Further, the inclination angles θ of the serrations 15a and 12f are approximate to the lead angles of the male screw 12c of the bolt member 12 and the female screw 13a of the nut member 13 (FIG. 5D). However, each inclination angle θ is an inclination of the inclined surfaces 15a1 and 12f1 with respect to a plane perpendicular to the common axis C of the ratchet member 15 and the bolt member 12.

  The ratchet member 15 is accompanied by a holder 18 for preventing rotation (FIGS. 1 and 6). 6A and 6B are a front view and a side view of the holder 18, respectively.

  The holder 18 is formed in a cylindrical shape. The holder 18 has a thin outer periphery on one end side, and a pair of axial engagement grooves 18a and 18a are formed in axial symmetry in the approximately half including the thin portion. The holder 18 is fixed by being press-fitted into a predetermined position of the cylinder chamber 11a with the engaging grooves 18a, 18a facing the closed end of the cylinder chamber 11a. On the other hand, the head portion 12 b of the bolt member 12 is slidably and rotatably inserted into the holder 18, and the radial protrusions 15 b and 15 b of the ratchet member 15 are inserted into the engaging grooves 18 a and 18 a of the holder 18. Is engaged. Therefore, the ratchet member 15 is accommodated so as to be slidable in the axial direction with respect to the cylinder chamber 11a via the holder 18 and not relatively rotatable.

  The second spring 16 is a disc spring having a constant load spring characteristic. The second spring 16 is interposed between the closed end of the cylinder chamber 11 a and the ratchet member 15. The second spring 16 biases the nut member 13 in the direction of pushing out the nut member 13 from the cylinder chamber 11a via the ratchet member 15 and the bolt member 12.

  The case 11 is provided with a detachable pin 19. The pin 19 engages with the annular groove 13b of the nut member 13 and acts as a restraining member that restrains the nut member 13 and the bolt member 12 at fixed positions in the cylinder chamber 11a. The pin 19 can be attached to and detached from the outside of the case 11 with respect to the pin hole 11 e formed in the case 11.

  The auto tensioner 10 accommodates the second spring 16 and the ratchet member 15 in the cylinder chamber 11a of the case 11 and press-fits the holder 18 for the ratchet member 15 (FIG. 7), followed by the bolt member 12 and the first spring. 14, the nut member 13 is assembled and the cap 17 for the nut member 13 is fixed, and the bolt member 12 is screwed into the nut member 13 while being compressed while the first spring 14 is compressed. At this time, the bolt member 12 engages a tool with the square hole 12d of the head 12b through the through hole 11b at the closed end of the cylinder chamber 11a and the circular hole 15d of the ratchet member 15 to prevent the nut member 13 from rotating. , A tool is engaged with the belt-like protrusion 13e on the tip surface and rotated, and the male screw 12c of the bolt member 12 and the female screw 13a of the nut member 13 are screw-engaged. When the bolt member 12 is fully screwed into the nut member 13, the pin 19 is engaged with the annular groove 13b of the nut member 13 through the pin hole 11e of the case 11 (FIG. 1), and the bolt member 12 and the nut member 13 are fixed. Restrain to position.

  The auto tensioner 10 can be used in a chain transmission device for driving a camshaft of an engine that drives camshafts 2 and 2 via a chain 1 (FIG. 8).

  The endless chain 1 is stretched over the sprockets 3a, 2a and 2a on the crankshaft 3, camshaft 2 and 2, and the chain 1 has a fixed type and a swing type chain on the tension side and the loose side, respectively. Guides 4 and 5 are provided. The swing type chain guide 5 is swingable about the support shaft 5 a, and the nut member 13 of the auto tensioner 10 presses the protrusion 5 b on the back surface of the chain guide 5, thereby applying tension to the chain 1. Can be granted. The auto tensioner 10 is fixed to an engine frame (not shown) via mounting bolts 10a and 10a. The auto tensioner 10 is assembled to the engine frame in a state where the bolt member 12 and the nut member 13 are restrained by the pin 19, and then the pin 19 is removed to release the restraint of the bolt member 12 and the nut member 13.

  When the restraint is released, the bolt member 12 and the nut member 13 are pushed by the first spring 14, so that the bolt member 12 is rotated relative to the nut member 13 to extend the entire length (see FIG. 9 (in the directions of arrows K1, K1), the tip of the nut member 13 pushes the projection 5b of the chain guide 5, and the serrations 12f, 15a of the bolt member 12 and the ratchet member 15 come into contact with each other in the axial direction to the serrations 12f, 15a. When the pressing force is applied (FIG. 10), the rotation of the bolt member 12 is stopped and a predetermined tension can be applied to the chain 1. This is because the male screw 12c of the bolt member 12 and the female screw 13a of the nut member 13 are formed to have a lead angle larger than the friction angle, and neither the ratchet member 15 nor the nut member 13 can rotate.

  When the chain 1 is loosened and the tension is insufficient, the bolt member 12 further rotates and advances the nut member 13 to rectify the tension of the chain 1 steplessly. When the tension of the chain 1 becomes excessive, the bolt member 12 rotates backward within the range of the backlash δ until the serrations 12f and 15a are completely in close contact with each other, compressing the first spring 14 and nut member 13 is retracted to eliminate excessive tension (in the direction of arrow K2 in FIG. 10), and when excessive tension exists, it retracts with the ratchet member 15 and nut member 13 against the second spring 16 ( The direction of the arrows K2 and K3 in FIG.

  In the above description, the internal thread 13a and the external thread 12c may be multi-threads other than 3-threads. Further, the pin 19 that restrains the nut member 13 may be replaced with another restraining member such as a machine screw. Furthermore, the second spring 16 can be an elastic spring other than a disc spring as long as a predetermined nonlinear characteristic can be realized.

  In FIG. 8, the chain 1 may be a toothed belt, and the cylinder chamber 11a of the case 11 may be directly formed on an engine frame (not shown) with the case 11 omitted.

Other embodiments

  In the auto tensioner 10, the bolt member 12 and the nut member 13 can change the shapes of the bolt member 12 and the nut member 13 to change the relative positional relationship (FIG. 11). However, FIGS. 11A and 11B are diagrams corresponding to FIGS. 1 and 7, respectively.

  In FIG. 11, the bolt member 12 and the ratchet member 15 are accommodated in the cylinder chamber 11 a of the case 11 so as to be slidable and non-rotatable. A serration 12f that meshes with the serration 15a of the ratchet member 15 is formed at the bottom 13g of the nut member 13, and corrects the looseness of the chain 1 via the bolt member 12 protruding from the cylinder chamber 11a. The bottom 13g of the nut member 13 forms a square hole 12d and is slidably and rotatably inserted into the holder 18 so as to face the ratchet member 15. Further, in addition to the annular groove 13b for the pin 19, notches 13c, 13c, 13d, and 13d (not shown) similar to FIG. 3 are formed on the head portion 12b of the bolt member 12. Therefore, the bolt member 12 is prevented from rotating through the cap 17, and a belt-like protrusion 13 e for engaging the tool is formed at the tip of the bolt member 12. A plurality of disc springs are interposed as second springs 16 between the ratchet member 15 and the closed end of the cylinder chamber 11a.

  The present invention can be widely and suitably applied to tension adjustments for chains, belts, and the like other than a transmission device for driving an engine camshaft.

θ ... Inclination angle 11a ... Cylinder chamber 12 ... Bolt member 12b ... Head 12c ... Male screw 12f ... Serration 13 ... Nut member 13a ... Female screw 13g ... Bottom 14 ... First spring 15 ... Ratchet member 15a ... Serration 16 ... Second Spring

Patent Applicant Enuma Chain Manufacturing Co., Ltd.

Claims (6)

  A bolt member that is housed in a cylinder chamber that is open at one end; a nut member that is screw-engaged with the bolt member from the open end side of the cylinder chamber; a first spring that is interposed between the bolt member and the nut member; A ratchet member that opposes the head of the bolt member; and a second spring that urges the bolt member and the nut member in a direction to push the nut member out of the cylinder chamber via the ratchet member. The ratchet member is housed in the cylinder chamber so as to be slidable and non-rotatable, and the bolt member and the ratchet member are formed with radial serrations that mesh with each other.   A nut member that is housed in a cylinder chamber that is open at one end; a bolt member that is screw-engaged with the nut member from the open end side of the cylinder chamber; and a first spring that is interposed between the nut member and the bolt member; A ratchet member opposed to the bottom of the nut member; and a second spring for biasing the nut member and the bolt member through the ratchet member in a direction to push the cylinder member out of the cylinder chamber. The member is housed in the cylinder chamber so as to be slidable and non-rotatable, and the nut member and the ratchet member are formed with radial serrations that mesh with each other.   3. The auto tensioner according to claim 1, wherein the male screw of the bolt member and the female screw of the nut member are formed at a lead angle larger than a friction angle of the thread surface.   4. The auto tensioner according to claim 3, wherein the radial serration is formed in a mountain shape having an inclination angle approximate to a lead angle of the male screw and the female screw.   The auto tensioner according to any one of claims 1 to 4, wherein the second spring has a constant load spring characteristic.   The auto tensioner according to any one of claims 1 to 5, wherein the bolt member and the nut member are restrained at a fixed position of the cylinder chamber via a detachable restraining member.

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