JP2020148306A - Chain tensioner - Google Patents

Abstract

To reduce the number of components for a chain tensioner while forming the chain tension in which resistance in relative rotation between a spring sheet and a plunger can be reduced as much as possible by providing an oil path and a relief valve at a closed end part of the plunger.SOLUTION: A valve seat 25 is composed of one component that integrally has an inlet 25a that is opened in a plunger 20, a seat surface 25b that fits a valve body 24, and an end surface 25c that faces a spring seat 60 in an axial direction. Of the contact parts between the opposite end surfaces 25c and 60a of the valve seat 25 and the spring seat 60, one has a flat surface shape and the other has a spherical shape. The inlet 25a of the valve seat 25 is located off the contact part of the valve seat 25.SELECTED DRAWING: Figure 1

Description

The present invention relates to a chain tensioner used to maintain tension of a timing chain that drives a camshaft of an automobile engine.

In an automobile engine, the rotation of a crankshaft is generally transmitted to a camshaft via a timing chain (hereinafter referred to as "chain"), and the rotation of the camshaft opens and closes a valve in a combustion chamber. Here, in order to keep the tension of the chain within an appropriate range, a tension adjusting device including a chain guide provided so as to be swingable around a fulcrum axis and a chain tensioner that presses the chain via the chain guide is used. ing.

As this chain tensioner, there is a hydraulic type having a bottomed cylinder-shaped cylinder and a plunger inserted into the cylinder so as to be slidable in the axial direction. When the tension of the chain increases during engine operation, the chain tensioner moves in the direction in which the plunger is pushed into the cylinder by the tension of the chain, and absorbs the tension of the chain. On the other hand, when the tension of the chain becomes small during engine operation, the plunger moves in the direction of protruding from the cylinder to absorb the slack of the chain.

When the engine is stopped, the tension of the chain may increase depending on the stop position of the camshaft. At this time, if the plunger moves significantly in the pushing direction in response to the tension of the chain, the chain may loosen significantly when the engine is started, causing the chain to flutter or skip teeth.

To prevent this, a plunger having a female screw portion, a screw rod having a male screw portion screwed into the female screw portion, a return spring for urging the plunger in a direction protruding from the cylinder, and one end of the return spring in the axial direction. The spring seat that receives the cylinder is adopted. The other end of the return spring is axially supported by a screw rod. The male threaded portion and the female threaded portion are serrated threads. That is, the flank angle of the push-side flank, which receives pressure when a load in the direction of pushing the plunger into the cylinder is applied to the threads of the male and female threads, applies a load in the direction of projecting the plunger from the cylinder. It is larger than the flank angle of the protruding flank that sometimes receives pressure (for example, Patent Document 1).

In the chain tensioner of Patent Document 1, in order to prevent the chain from becoming over-tensioned, an oil passage for releasing pressure (hydraulic oil) to the outside when the hydraulic pressure in the plunger becomes excessively high, and this oil A relief valve that opens and closes the road is used. Since these oil passages and relief valves are disadvantageous in terms of processing cost and miniaturization if they are provided on the cylinder side, they are each provided as a part of the closed end portion of the plunger.

The relief valve has a valve body, a valve seat that receives the valve body, a valve spring that urges the valve body toward the valve seat, and a valve sleeve that is fitted to the valve seat. The relief valve is positioned by an annular retainer press-fitted into the inner circumference of the plunger so that it cannot move toward the tip of the plunger. A spacer is interposed between the retainer and the spring seat. The spacer has a flow path that introduces the pressure in the plunger to the through hole of the retainer. The flow path of the spacer is formed at a portion separated from the contact portion between the spacer and the spring seat in order to introduce pressure (hydraulic oil) from the upstream side in the plunger. The valve seat integrally has an inlet open to the through hole of the retainer and a seat surface that fits the valve body.

Of the contact portions between the opposing end faces of the spacer and the spring seat, one is formed in a flat surface shape and the other is formed in a spherical shape. Therefore, the contact portion between the spacer and the spring seat is formed in a substantially dot shape. This is to reduce the resistance when the spring seat rotates relative to the plunger together with the screw rod supporting the return spring as much as possible.

Japanese Unexamined Patent Publication No. 2008-247713

However, the chain tensioner of Patent Document 1 has room for improvement in that the number of parts increases due to the use of a retainer for positioning the relief valve and a spacer between the retainer and the spring seat, and labor is required for assembly.

Therefore, the problem to be solved by the present invention is to provide a chainer with an oil passage and a relief valve at the closed end of the plunger to reduce the resistance during relative rotation between the spring seat and the plunger as much as possible. It is to reduce the number of parts.

The invention according to the first means for solving the above-mentioned problems is a cylinder, a cylinder tip portion slidably inserted into the cylinder in the axial direction, a closed end portion protruding from the cylinder, and a female screw portion. A screw rod having a plunger having the above, one end housed in the plunger, the other end protruding from the cylinder tip portion, and a male screw portion screwed to the female screw portion, and the plunger from the cylinder. A return spring urging in a projecting direction and a spring seat that receives the return spring in the axial direction are provided, the return spring is axially supported by the cylinder, and the closed end portion of the plunger is In a chain tensioner having an oil passage for releasing the pressure in the plunger to the outside and a relief valve for opening and closing the oil passage, the relief valve has a valve body and a valve seat for receiving the valve body. The valve seat is composed of a component having an inlet opened in the plunger, a seat surface that fits the valve body, and an end surface that faces the spring seat in the axial direction. The valve seat and the spring seat. Of the contact portions between the opposing end faces of the above, one is flat and the other is spherical, and the inlet of the valve seat is formed at a portion separated from the contact portion of the valve seat. It was adopted.

According to the configuration according to the first means, the end faces of the valve seat and the spring seat are in contact with each other, one of the contact portions has a flat surface shape and the other has a spherical shape, and the valve seat inlet is from the contact portion. Since it is open to the inside of the plunger at the detached part, the rotational resistance at the contact portion between the spring seat and the valve seat can be reduced as much as possible without using a spacer.

Specifically, the valve seat may have a groove formed so as to allow air entering from the inlet to escape from the valve body in a state of being in contact with the seat surface to the outside. In this way, the air that has entered the plunger can be discharged to the outside via the relief valve even when the relief valve is closed.

It is preferable that the closed end portion of the plunger has a seat receiver that fits the valve seat and abuts in the axial direction, and the valve seat is fixed by press fitting or adhesion to the seat receiver. In this way, the retainer for positioning the relief valve can be omitted.

The invention according to the second means for solving the above-mentioned problems is a cylinder, a cylinder tip portion slidably inserted into the cylinder in the axial direction, a closed end portion protruding from the cylinder, and a female thread portion. A screw rod having a plunger having the above, one end housed in the plunger, the other end protruding from the tip of the cylinder, and a male screw portion screwed to the female screw portion, and the plunger from the cylinder. A return spring urging in a protruding direction and a spring seat that receives the return spring in the axial direction are provided, the return spring is axially supported by the screw rod, and the closed end portion of the plunger is In a chain tensioner having an oil passage for releasing the pressure in the plunger to the outside and a relief valve for opening and closing the oil passage, the relief valve has a valve body and a valve seat for receiving the valve body. A spacer is provided between the valve seat and the spring seat, and the spacer has a first end surface that faces the spring seat in the axial direction, a second end surface that aligns with the valve seat in the axial direction, and the plunger. It is composed of one component that integrally has a flow path that introduces the internal pressure to the valve seat, and the valve seat integrally has an inlet that opens into the flow path of the spacer and a seat surface that fits the valve body. It is composed of one component, and of the contact portions between the opposing end faces of the spacer and the spring seat, one has a flat surface shape and the other has a spherical shape, and the flow path of the spacer is from the contact portion of the spacer. It is formed at a detached portion, and the spacer is fixed by press fitting or adhesion to the plunger.

According to the configuration according to the second means, the first end surface of the spacer and the end surface of the spring seat are in contact with each other, one of the contact portions has a flat surface shape and the other has a spherical shape, and the flow path of the spacer is the said. Since the portion separated from the contact portion is opened in the plunger, the rotational resistance at the contact portion between the spring seat and the spacer can be reduced as much as possible. Since the spacer has a second end face that fits the valve seat in the axial direction and is fixed by press fitting or adhesion to the plunger, the valve seat cannot be moved to the cylinder tip side of the plunger by the spacer without using a retainer. Can be positioned.

Also in the second means, it is preferable that the valve seat has a groove formed so as to allow air entering from the inlet to escape from the valve body in a state of being in contact with the seat surface to the outside. The air that has entered the plunger can be discharged to the outside via the spacer flow path and the relief valve even when the relief valve is closed.

It is preferable that the spacer is fixed by press-fitting to the plunger, and the press-fitting portion of the spacer with the plunger is composed of a plurality of protrusions protruding in the radial direction. In this way, a plurality of protrusions of the spacer are press-fitted into the plunger, so that press-fitting can be facilitated.

As described above, in the present invention, by adopting the configuration according to the first means, an oil passage and a relief valve are provided at the closed end of the plunger, and resistance during relative rotation between the spring seat and the plunger is reduced. It is possible to reduce the number of parts by omitting the spacer as in Patent Document 1 while reducing the number of parts as much as possible.

Further, in the present invention, by adopting the configuration according to the second means, an oil passage and a relief valve are provided at the closed end of the plunger, and the resistance during relative rotation between the spring seat and the plunger is reduced as much as possible. It is possible to reduce the number of parts by omitting the retainer as in Patent Document 1 while using the chain tensioner.

A vertical cross-sectional view showing a chain tensioner according to the first embodiment of the present invention as a cut surface along the line I-I of FIG. Enlarged view of the vicinity of the relief valve in FIG. Bottom view of the valve seat of FIG. Side view of the valve seat of FIG. Perspective view of the valve seat of FIG. Top view of the valve seat of FIG. Partial perspective view showing the valve seat according to the second embodiment of the present invention. Sectional drawing which shows the closed state of the valve seat of FIG. Partial longitudinal sectional view of the chain tensioner according to the third embodiment of the present invention. Top view of the valve seat of FIG. Bottom view of the valve seat of FIG. Partial longitudinal sectional view of the chain tensioner according to the fourth embodiment of the present invention. Perspective view of the valve seat of FIG. Partial longitudinal sectional view of the chain tensioner according to the fifth embodiment of the present invention. Perspective view of the valve seat of FIG. Top view of the valve seat according to the sixth embodiment of the present invention. Side view of the valve seat of FIG. Front view schematically showing an example of a belt transmission device including a chain tensioner according to the present invention.

A first embodiment as an example of the invention according to the first means described above will be described with reference to FIGS. 1 to 6 of the accompanying drawings.

The chain tensioner shown in FIG. 1 includes a bottomed cylindrical cylinder 10, a plunger 20 slidably inserted into the cylinder 10 in the axial direction, a screw rod 30 screwed with the plunger 20, and a screw rod 30. A check valve 40 arranged between the cylinder 10 and the cylinder 10, a return spring 50 that urges the plunger 20 to protrude from the cylinder 10, and a spring seat 60 that receives the return spring 50 in the axial direction are provided.

Here, the axial direction refers to a direction along the axis of the cylindrical inner peripheral portion of the cylinder 10 that guides the plunger 20. Hereinafter, the circumferential direction refers to the circumferential direction around the axis, and the radial direction refers to the direction perpendicular to the axis.

The cylinder 10 has a cylinder main body 11 including a cylindrical inner peripheral portion, and a plurality of flange portions 11a integrally formed on the outer periphery of the cylinder main body 11. The flange portion 11a is used to fasten the chain tensioner to the side surface of the engine block (not shown) with bolts.

The plunger 20 is composed of a tubular body 21 opened at both ends in the axial direction, a cap 22 fixed to one end of the tubular body 21, and a relief valve 23 attached to the cap 22. The cylinder body 21 has a cylinder tip portion 21a slidably inserted into the cylinder 10 in the axial direction, and a female screw portion 21b formed on the inner peripheral side. The closed end portion of the plunger 20 protruding from the cylinder 10 is composed of a cap 22 and a relief valve 23. The cap 22 is fixed by press fitting to one end of the tubular body 21. The cap 22 may be fixed to one end of the tubular body 21 by press-fitting projection joining. Further, the portion corresponding to the cap 22 and the tubular body 21 may be formed by one component.

A refueling passage 11b that communicates with a space (pressure chamber) surrounded by the cylinder 10 and the plunger 20 is formed at the closed end of the cylinder body 11. The oil supply passage 11b is connected to an oil pump (not shown) via an oil hole (not shown) formed in the engine block, and is for introducing the hydraulic oil delivered from the oil pump into the pressure chamber. Is. A check valve 40 is provided at the end of the oil supply passage 11b on the pressure chamber side.

The check valve 40 has a rod seat 41 that also serves as a valve seat, a valve body 42, and a retainer 43 that holds the valve body 42 in a valve chamber formed in the rod seat 41. The valve hole 41a formed in the rod seat 41 is opened and closed by the valve body 42. The check valve 40 allows only the flow of hydraulic oil from the oil supply passage 11b side to the pressure chamber side.

A minute leak gap is formed between the sliding surface of the plunger 20 and the cylinder 10. The hydraulic oil in the pressure chamber leaks to the outside of the cylinder 10 through the leak gap.

When the oil pump stops when the engine is stopped, the oil level in the refueling passage 11b drops, and a large amount of air accumulates in the refueling passage 11b. When the engine is restarted, air enters the pressure chamber from the refueling passage 11b. Inflows. At the end of the cylinder 10 on the closed side, an air bleeding passage that communicates with the inside and outside of the cylinder 10 is provided in order to let the air in the pressure chamber escape to the outside. The air bleeding passage is configured as a small spiral screw gap formed between a screw hole 11c penetrating from the outer side of the cylinder body 11 to the pressure chamber and a male screw member 12 screwed into the screw hole 11c. ing.

The screw rod 30 has one end portion 31 housed in the plunger 20, the other end portion 32 protruding from the cylinder tip portion 21a, and a male screw portion 33 screwed to the female screw portion 21b. The other end 32 of the screw rod 30 is in contact with the rod sheet 41 supported axially and radially at the closed end of the cylinder 10. The rod sheet 41 is interposed between the screw rod 30 and the cylinder 10, and supports the screw rod 30 in the axial direction so that the screw rod 30 can rotate relative to the cylinder 10 in the circumferential direction.

The female threaded portion 21b of the plunger 20 applies pressure when a load in the direction of pushing the plunger 20 into the cylinder 10 is applied and a pressure is applied to the flank on the pushing side, and when a load in the direction of projecting the plunger 20 from the cylinder 10 is applied. It has a protruding flank to receive and a thread top surface formed between the pushing flank and the protruding flank. The flank angle of the push-in side flank of the female screw portion 21b is formed in a serrated shape larger than the flank angle of the protruding side flank.

Similarly, the male threaded portion 33 of the screw rod 30 is also formed in a serrated shape. The flank angle of the push-side flank of the male screw portion 33 receives pressure when a load in the direction of pushing the plunger 20 into the cylinder 10 is applied, and receives pressure when a load in the direction of projecting the plunger 20 from the cylinder 10 is applied. It is larger than the flank angle of the protruding flank of the male screw portion 33.

The flank angle of the push-in side flank of the male screw portion 33 is the same as the flank angle of the push-in side flank of the female screw portion 21b. The flank angle of the protruding side flank of the male threaded portion 33 is the same as the flank angle of the protruding side flank of the female threaded portion 21b. The flank angle of the push-in side flank is generally set in the range of 64 ° to 76 ° with respect to the axial direction. By setting the flank angle of the flank on the pushing side to 64 ° or more, when an axial load in the direction of pushing the screw rod 30 into the plunger 20 is statically applied between the screw rod 30 and the plunger 20, the female thread portion It is possible to reliably prevent slippage between the push-in side flank of 21b and the push-in side flank of the male screw portion 33. Further, by setting the flank angle of the push-in side flank to 76 ° or less, when the above-mentioned axial load is applied between the screw rod 30 and the plunger 20, the male screw portion 33 and the female screw portion 21b are formed like a wedge. It is possible to prevent the situation of biting and locking.

The flank angle of the protruding side flank of the female thread portion 21b is generally set in the range of 6 ° to 16 ° with respect to the axial direction. By setting the flank angle of the protruding side flank to 16 ° or less, when the above-mentioned axial load is statically applied between the screw rod 30 and the plunger 20, the protruding side flank and the male screw portion 33 of the female screw portion 21b The screw rod 30 and the plunger 20 can be smoothly moved relative to each other in the direction in which the plunger 20 is projected from the cylinder 10 by causing slippage between the flank and the protruding side flank.

The return spring 50 is made of a coil spring. One end of the return spring 50 presses the closed end portion of the plunger 20 via the spring seat 60. By the pressing, the plunger 20 is urged in a direction protruding from the cylinder 10. The other end of the return spring 50 is axially supported by the screw rod 30. A cylindrical surface 34 that supports the outer circumference of the return spring 50 in the radial direction is formed on the inner circumference of the screw rod 30. The stepped portion on the other end 32 side of the cylindrical surface receives the other end of the return spring 50 in the axial direction.

The spring seat 60 has a flat end face 60a along the radial direction and a body portion 60b having a diameter smaller than that of the end face 60a. The body portion 60b is inserted inside the return spring 50. The spring seat 60 transmits the urging force of the return spring 50 from the end surface 60a to the closed end portion of the plunger 20.

As shown in FIGS. 1 and 2, the cap 22 of the plunger 20 has an oil passage 22a for releasing the pressure in the plunger 20 to the outside. A relief valve 23 is provided at the end of the oil passage 22a on the pressure chamber side.

The relief valve 23 has a valve body 24, a valve seat 25 that receives the valve body 24, and a valve spring 26 that urges the valve body 24 toward the valve seat 25.

The valve body 24 is made of a steel ball. The valve spring 26 is composed of a coil spring. The valve seat 25 is composed of a single component in which the entire valve seat 25 is integrally formed of metal or resin.

As shown in FIGS. 2 to 6, the valve seat 25 has an inlet 25a opened in the plunger 20, a seat surface 25b that fits the valve body 24, an end surface 25c that faces the spring seat 60 in the axial direction, and an outer diameter. It integrally has an outer stepped portion 25d having a difference.

The cap 22 has a seat receiver 22b that is radially fitted and axially abutted with the outer stepped portion 25d of the valve seat 25. The valve seat 25 is fixed by press fitting or adhesion to the seat receiver 22b.

As shown in FIGS. 2, 5, and 6, the seat surface 25b of the valve seat 25 is a surface portion that defines the outlet of the valve seat 25, and can come into contact with the valve body 24 without a gap over the entire inner circumference. It has a conical surface shape that includes various parts.

As shown in FIGS. 2 to 4, the end surface 25c of the valve seat 25 has a spherical shape that is convex toward the end surface 60a of the spring seat 60. The center that defines the spherical shape of the end face 25c and the center line that defines the disk shape of the end face 60a are set coaxially with the axis that defines the axial direction. Of the contact portions between the opposing end faces 25c and 60a of the valve seat 25 and the spring seat 60, one has a flat surface shape and the other has a spherical shape, so that the contact portions are formed in a substantially dot shape.

When the screw rod 30 shown in FIG. 1 rotates relative to the plunger 20, the screw rod 30 that supports the other end of the return spring 50 and the spring seat 60 that receives one end of the return spring 50 rotate integrally. At this time, the spring seat 60 rotates relative to the plunger 20. At this time, the resistance during relative rotation between the spring seat 60 and the plunger 20 is reduced as much as possible by making these contact portions point-shaped.

As shown in FIG. 2, the inlet 25a of the valve seat 25 is formed at a portion of the end face 25c that faces the end face 60a of the spring seat 60 in the axial direction and is separated from the above-mentioned point contact portion of the valve seat 25. There is. As shown in FIGS. 3 and 6, the entrance 25a is open at three locations evenly distributed in the circumferential direction. These three inlets 25a communicate with the central oil passage extending axially from the seat surface 25b. The number of entrances 25a is not particularly limited.

When the pressure inside the plunger 20 is equal to or lower than the set pressure, the pressure introduced from the inlet 25a pushes the valve body 24 seated on the seat surface 25b, but the urging force of the valve spring 26 is superior. Therefore, the relief valve 23 keeps the oil passage 22a in a closed state (closed state). On the other hand, when the pressure inside the plunger 20 exceeds the set pressure, the valve spring 26 loses to the pressure introduced from the inlet 25a, and the valve body 24 separates from the seat surface 25b. Therefore, the relief valve 23 is in a state where the oil passage 22a is open (valve open state). In this valve open state, the hydraulic oil in the plunger 20 flows into the valve seat 25 from the inlet 25a, flows out from the gap between the seat surface 25b and the valve body 24 to the outside with respect to the valve seat 25, and further. It flows through the oil passage 22a and finally flows out to the outside.

The chain tensioner shown in FIG. 1 is as described above, and the end faces 25c and 60a of the valve seat 25 and the spring seat 60 are in contact with each other, and the contact portion of the end face 60a, which is one of the contact portions, has a flat surface shape. The other end surface 25c of the contact portion is spherical, and the inlet 25a of the valve seat 25 is opened in the plunger 20 at a portion of the end surface 25c that is separated from the contact portion, as in Patent Document 1. The rotational resistance at the contact portion between the spring seat 60 and the valve seat 25 can be reduced as much as possible without using a proper spacer, and therefore the resistance during relative rotation between the spring seat 60 and the plunger 20 can be reduced as much as possible. Can be done.

Further, the chain tensioner shown in FIG. 1 can reduce the number of parts by omitting the spacer.

Further, the chain tensioner shown in FIGS. 1 and 2 has a seat receiver 22b in which the closed end portion of the plunger 20 fits with the valve seat 25 and abuts in the axial direction, and the valve seat 25 is press-fitted or adhered to the seat receiver 22b. Since it is fixed by the valve seat 25, the valve seat 25 can be positioned so as not to move to the cylinder tip portion 21a side of the plunger 20 without using a retainer as in Patent Document 1, and the number of parts can be further reduced. ..

In the first embodiment, when the relief valve 23 is in the closed state, the oil passage 22a is completely closed by the full-circle contact between the seat surface 25b and the valve body 24, but the damper performance as a chain tensioner is not hindered. It is also possible to allow leakage from the seat surface and the valve body within the range. A second embodiment as an example thereof is shown in FIGS. 7 and 8. In the following, only the differences from the first embodiment will be described, and the same reference numerals will be used for the corresponding components.

As shown in FIGS. 7 and 8, the valve seat 25 according to the second embodiment has a groove 25e that divides the seat surface 25b in the circumferential direction. The groove 25e extends from the conical seat surface 25b with a depth along the seat surface 25b. As shown in FIG. 8, the groove 25e forms a gap between the groove 25e and the valve body 24 in a state of being fitted to the seat surface 25b. When the relief valve 23 shown in FIG. 2 is in the closed state, the air entering from the inlet 25a reaches the valve body 24 shown in FIG. The air cannot escape to the outside from the region where the valve body 24 and the seat surface 25b meet, but can escape to the outside from between the groove 25e and the valve body 24.

As described above, in the chain tensioner according to the second embodiment, the groove formed so that the valve seat 25 allows the air entering from the inlet 25a to escape from between the valve body 24 in the state of being combined with the seat surface 25b to the outside. Since it has 25e, the air can be discharged to the outside via the relief valve 23 even when the relief valve 23 is closed.

In the first and second embodiments described above, an example in which the contact portion of the valve seat is spherical and the contact portion of the spring seat is flat surface is shown, but this may be reversed. In addition, although the relief valve is used as both a cap and a valve case, it is also possible to use a valve case that is separate from the cap. As an example of these, the third embodiment is shown in FIGS. 9 to 11.

The end surface 25c of the valve seat 25 according to the third embodiment is formed in a flat surface shape along the radial direction. On the other hand, the end surface 60a of the spring seat 60 is formed in a spherical shape that is convex toward the valve seat 25 side.

The inlet 25a of the valve seat 25 has a shape that is open only in the axial direction. This is to secure the press-fitting strength of the outer stepped portion 25d while avoiding an increase in the axial thickness of the valve seat 25. The inlet 25a is narrower than that of the first embodiment, but by increasing the number of inlets 25a, the inflow of hydraulic oil when the valve is open can be sufficiently ensured. Therefore, the inlets 25a are formed at four locations evenly distributed in the circumferential direction.

The valve body 24 and the valve spring 26 are housed in the valve case 27. The valve case 27 has a bottomed tubular shape and is fitted in the cap 22. The valve case 27 has a seat receiver 27a and an opening 27b communicating with the oil passage 22a formed in the cap 22. The valve seat 25 is fixed by press fitting or adhesion to the seat receiver 27a of the valve case 27.

In the first to third embodiments described above, the case where the inlet of the valve seat is opened at least in the axial direction is illustrated, but it is also possible to adopt the inlet opened only on the outer periphery of the valve seat. A fourth embodiment as an example of this is shown in FIGS. 12 and 13. Since the fourth embodiment is further modified from the third embodiment, the differences from the third embodiment will be described here.

The inlet 25a of the valve seat 25 is formed at two locations penetrating the outer circumference of the valve seat 25 of the cap 22 in the radial direction. The cap 22 has an inner peripheral surface portion 22c that faces the inlet 25a in the radial direction. In the fourth embodiment, the shaft of the valve seat 25 is compared with the example in the first to third embodiments in which the inlet is formed only within the range of the portion facing the end surface 60a of the spring seat 60 in the axial direction. Although the directional thickness is increased, there is an advantage that the cross section of the oil passage from the inlet 25a to the seat surface 25b can be widened.

A fifth embodiment as an example of the present invention according to the above-mentioned second means will be described with reference to FIGS. 14 and 15. Hereinafter, the differences from the first embodiment will be described, and the same reference numerals will be used for the corresponding components (see FIG. 1 as appropriate).

The chain tensioner according to the fifth embodiment includes a spacer 70 interposed between the valve seat 25 and the spring seat 60. The spacer 70 is composed of a component in which the entire spacer 70 is integrally formed of metal or resin.

The spacer 70 applies the first end surface 70a that faces the spring seat 60 in the axial direction, the second end surface 70b that aligns with the valve seat 25 in the axial direction, the outer surface portion 70c that is press-fitted into the plunger 20, and the pressure inside the plunger 20. It has an integral flow path (70d, 70e) for introducing up to the valve seat 25.

The spacer 70 is fixed by press fitting or adhesion to the plunger 20. The press-fitting or bonding portion is between the arc-shaped outer surface portion 70c extending in the circumferential direction and the cylindrical inner peripheral surface portion 22c of the cap 22 in the spacer 70.

The first end surface 70a and the second end surface 70b of the spacer 70 each have a flat surface shape along the radial direction.

The end surface 60a of the spring seat 60 has a spherical shape that is convex toward the spacer 70. The center that defines the spherical shape of the end surface 60a and the center line that defines the disk shape of the first end surface 70a are set coaxially with the axis that defines the axial direction. Of the contact portions between the opposing end faces 70a and 60a of the spacer 70 and the spring seat 60, one has a flat surface shape and the other has a spherical shape, so that the contact portions are formed in dots. Therefore, also in the fifth embodiment, when the spring seat 60 and the plunger 20 rotate relative to each other, the rotation resistance at the contact portion between the spacer 70 and the spring seat 60 can be reduced as much as possible.

The flow path of the spacer 70 is composed of a vertical flow path 70d extending in the axial direction and a horizontal flow path 70e extending in the radial direction, and is formed at a portion of the spacer 70 that is separated from the above-mentioned contact portion. The vertical flow path 70d extends in a groove shape that divides the outer surface portion 70c of the spacer 70 in the circumferential direction. The vertical flow paths 70d are formed at four locations evenly distributed in the circumferential direction, but the number thereof is not particularly limited. The lateral flow path 70e has a groove shape extending in the radial direction with a depth in the axial direction from the second end surface 70b of the spacer 70, and intersects the vertical flow path 70d at both ends thereof.

The inlet 25a of the valve seat 25 is open toward the lateral flow path 70e of the spacer 70. There is only one inlet 25a, which is directly connected to the central oil passage extending axially from the seat surface 25b. The inlet 25a may be arranged at a plurality of locations as long as it is arranged so as to be open to the flow path of the spacer 70.

The chain tensioner according to the fifth embodiment is as described above, and the first end surface 70a of the spacer 70 and the end surface 60a of the spring seat 60 are in contact with each other, one of the contact portions has a flat surface shape, and the other has a spherical surface. Since the flow path (70d, 70e) of the spacer 70 is open to the inside of the plunger 20 at a portion separated from the contact portion of the spacer 70, the rotational resistance at the contact portion between the spring seat 60 and the spacer 70 is increased. It can be reduced as much as possible, and therefore the resistance during relative rotation between the spring seat 60 and the plunger 20 can be reduced as much as possible.

Further, the chain tensioner according to the fifth embodiment has a second end surface 70b whose spacer 70 is axially aligned with the valve seat 25, and is fixed by press fitting or adhesion to the plunger 20 as in Patent Document 1. The valve seat 25 can be positioned by the spacer 70 so as not to move toward the cylinder tip 21a side of the plunger 20, and the number of parts can be reduced by omitting the retainer without using a retainer.

In the fifth embodiment, the spacer 70 is fixed to the plunger 20 between the arcuate outer surface 70c of the spacer 70 and the inner peripheral surface 22c of the plunger 20, but when the spacer is fixed by press fitting to the plunger, it is easier to press fit. It is also possible to change to a fixed structure. A sixth embodiment as an example thereof is shown in FIGS. 16 and 17. Since the sixth embodiment is further modified from the fifth embodiment, the differences from the fifth embodiment will be described here.

The spacer 70 according to the sixth embodiment is fixed by press fitting into the inner peripheral surface portion 22c of the plunger 20. The spacer 70 has a protrusion 70f protruding in the radial direction from the outer surface portion 70c having an arcuate surface at a portion that faces the inner peripheral surface portion 22c of the plunger 20 in the radial direction. The protrusion 70f has a wedge shape that becomes lower toward the valve seat 25 side in the axial direction. The height of the protrusion 70f is exaggerated. The diameter of the outer side surface portion 70c is smaller than that of the fifth embodiment, and the diameter of the outer surface portion 70c is smaller than that of the inner peripheral surface portion 22c. The protrusions 70f are formed at a plurality of locations evenly distributed in the circumferential direction. The radial tightening allowance between the plunger 20 and the spacer 70 is defined between the inner peripheral surface portion 22c and the protrusion 70f.

In the chain tensioner according to the sixth embodiment, the spacer 70 is fixed by press-fitting to the plunger 20, and the press-fitting portion of the spacer 70 with the plunger 20 is composed of a plurality of protrusions 70f protruding in the radial direction. Compared to the case where most of the outer circumference of the spacer 70 (outer surface portion other than the vertical flow path 70d) is press-fitted into the inner peripheral surface portion 22c of the plunger 20 as in the embodiment, only the plurality of protrusions 70f of the spacer 70 are made into the plunger 20. Since the press-fitting is performed, the press-fitting can be facilitated.

Also in the fifth and sixth embodiments, it is possible to make the end surface 60a of the spring seat 60 flat and the first end surface 70a of the spacer 70 spherical.

Further, also in the fifth and sixth embodiments, by adopting the groove 25e shown in FIGS. 7 and 8, the air that has entered the plunger 20 can be passed through the spacer 70 even when the relief valve 23 is closed (70d to 70d). 70e), it can be discharged to the outside via the relief valve 23.

As described above, the above-mentioned first to sixth embodiments can be adopted in appropriate combinations. For example, the second embodiment can be combined with any of the third to fourth embodiments.

FIG. 18 shows a chain transmission device including a chain tensioner as in each of the above embodiments. The chain transmission device shown in FIG. 18 includes a chain tensioner 1, a sprocket 3 fixed to a crankshaft 2 of an engine, and a chain 6 bridged to a sprocket 5 fixed to a camshaft 4. The chain 6 transmits the rotation of the crankshaft 2 to the camshaft 4. The rotation of the camshaft 4 opens and closes a valve (not shown) in the combustion chamber.

A chain guide 8 that is swingably supported around a fulcrum shaft 7 is in contact with the chain 6. The chain tensioner 1 may correspond to any of the above-described first to sixth embodiments. The chain tensioner 1 is bolted to the outer surface of the engine cover at the flange portion 11a of FIG. The closed end portion (cap 22) of the plunger 20 presses the chain 6 via the chain guide 8 of FIG. 18 (see FIGS. 1 and 18 as appropriate below).

When the tension of the chain 6 increases during engine operation, the push-in side flank of the female screw portion 21b of the plunger 20 pushes the male screw portion 33 on the outer circumference of the screw rod 30 due to the axial load in the direction of pushing the plunger 20 into the cylinder 10. Contact the side flank. After that, the screw rod 30 is gradually pushed into the plunger 20 by accumulating the slip between the female screw portion 21b and the male screw portion 33 due to the vibration of the chain 6, and the plunger 20 is pushed into the cylinder 10 accordingly. It gradually moves in the direction of the cylinder and absorbs the tension of the chain 6. At this time, since the slip between the female screw portion 21b and the male screw portion 33 due to the vibration of the chain 6 is very small, the moving speed of the plunger 20 is limited and a damper action occurs.

On the other hand, when the tension of the chain 6 becomes small during engine operation, the plunger 20 protrudes from the cylinder 10 and absorbs the slack of the chain 6. At this time, due to the urging force of the return spring 50, the protruding side flank of the female screw portion 21b of the plunger 20 comes into contact with the protruding side flank of the male screw portion 33 of the screw rod 30, and between the female screw portion 21b and the protruding side flank of the male screw 33. The screw rod 30 rotates due to the sliding of the screw rod 30, and the plunger 20 moves in the direction of protruding from the cylinder 10.

Further, when the engine is stopped, the tension of the chain 6 may increase depending on the stop position of the camshaft 4. In this case, since the chain 6 does not vibrate, slip does not occur between the push-in flank of the female screw portion 21b of the plunger 20 and the push-in flank of the male screw portion 33 of the screw rod 30, and the position of the screw rod 30 is fixed. .. Therefore, when the engine is restarted, the chain 6 is less likely to loosen, and the engine can be started smoothly.

In this belt transmission device, an internal chain tensioner 1 fixed to the side surface of the engine block (inside the engine cover) has been described as an example, but the present invention has an exterior attached to a hole penetrating the inside and outside of the engine cover. The same can be applied to the chain tensioner of the formula.

It should be considered that each embodiment disclosed this time is exemplary in all respects and not restrictive. Therefore, the scope of the present invention is shown not by the above description but by the scope of claims, and it is intended that all modifications within the meaning and scope equivalent to the scope of claims are included.

1 Chain tensioner 10 Cylinder 20 Plunger 21a Cylinder tip 21b Female thread 22 Cap 22a Oil passage 22b, 27a Seat receiver 23 Relief valve 24 Valve body 25 Valve seat 25a Inlet 25b Seat surface 25c End surface 25e Groove 30 Screw rod 31 One end 32 Other end Part 33 Male thread part 50 Return spring 60 Spring seat 60a End face 70 Spacer 70a First end face 70b Second end face 70d Vertical flow path 70e Horizontal flow path 70f Protrusion

Claims (6)

Cylinder and
A plunger having a cylinder tip portion slidably inserted into the cylinder in the axial direction, a closed end portion protruding from the cylinder, and a female thread portion.
A screw rod having one end housed in the plunger, the other end protruding from the tip of the cylinder, and a male screw portion screwed to the female screw portion.
A return spring that urges the plunger to protrude from the cylinder,
A spring seat that receives the return spring in the axial direction and
With
The return spring is axially supported by the screw rod.
The closed end portion of the plunger has an oil passage for releasing the pressure in the plunger to the outside and a relief valve for opening and closing the oil passage.
In a chain tensioner in which the relief valve has a valve body and a valve seat that receives the valve body.
The valve seat is composed of a component having an inlet opened in the plunger, a seat surface that fits the valve body, and an end surface that faces the spring seat in the axial direction.
Of the contact portions between the opposing end faces of the valve seat and the spring seat, one has a flat surface shape and the other has a spherical shape.
A chain tensioner characterized in that the inlet of the valve seat is formed at a portion separated from the contact portion of the valve seat. The chain tensioner according to claim 1, wherein the valve seat has a groove formed so as to allow air entering from the inlet to escape from the valve body in a state of being matched with the seat surface to the outside. The first or second claim, wherein the closed end portion of the plunger has a seat receiver that is fitted to the valve seat and abuts in the axial direction, and the valve seat is fixed by press fitting or adhesion to the seat receiver. Chain tensioner. Cylinder and
A plunger having a cylinder tip portion slidably inserted into the cylinder in the axial direction, a closed end portion protruding from the cylinder, and a female thread portion.
A screw rod having one end housed in the plunger, the other end protruding from the tip of the cylinder, and a male screw portion screwed to the female screw portion.
A return spring that urges the plunger to protrude from the cylinder,
A spring seat that receives the return spring in the axial direction and
With
The return spring is axially supported by the screw rod.
The closed end portion of the plunger has an oil passage for releasing the pressure in the plunger to the outside and a relief valve for opening and closing the oil passage.
In a chain tensioner in which the relief valve has a valve body and a valve seat that receives the valve body.
A spacer interposed between the valve seat and the spring seat is provided.
The spacer integrally has a first end surface that faces the spring seat in the axial direction, a second end surface that aligns with the valve seat in the axial direction, and a flow path that introduces pressure in the plunger to the valve seat. Consists of one part
The valve seat is composed of a component having an inlet open to the flow path of the spacer and a seat surface that fits the valve body integrally.
Of the contact portions between the facing ends of the spacer and the spring seat, one has a flat surface shape and the other has a spherical shape.
The flow path of the spacer is formed at a portion separated from the contact portion of the spacer.
A chain tensioner characterized in that the spacer is fixed by press fitting or adhesion to the plunger. The chain tensioner according to claim 4, wherein the valve seat has a groove formed so as to allow air entering from the inlet to escape from the valve body in a state of being matched with the seat surface to the outside. The chain tensioner according to claim 4 or 5, wherein the spacer is fixed by press fitting into the plunger, and the press-fitting portion of the spacer with the plunger is composed of a plurality of protrusions protruding in the radial direction.

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