Tensioner

Abstract

An object of the present invention is to provide a tensioner that enables a sufficient amount of stroke for the plunger to be secured and allows for size and weight reductions without changing the size of the tensioner body. In the tensioner according to the invention, an oil supply path that supplies oil from outside to an oil reservoir chamber formed inside the plunger includes an oil supply space formed between an inner circumferential surface of the plunger bore and an outer circumferential surface of the plunger. The oil supply space is formed by a front-end communication groove formed on an inner circumferential surface of the plunger bore and communicating with a tensioner body oil supply hole, and a rear-end communication groove formed on an outer circumferential surface of the plunger and causing the front-end communication groove to communicate with a plunger oil supply hole.

Claims

1. A tensioner comprising: a tensioner body having a plunger bore that is open on a front side; a cylindrical plunger slidably accommodated in the plunger bore and having a plunger hole that is open on a rear side; a check valve partitioning a space between the tensioner body and the cylindrical plunger into an oil reservoir chamber on the front side and an oil pressure chamber on the rear side and allowing oil to flow into the oil pressure chamber while stopping the oil from flowing reversely into the oil reservoir chamber; a main biasing means accommodated in the oil pressure chamber such as to freely expand and contract and urging the cylindrical plunger in a protruding direction; and an oil supply path that supplies oil to the oil reservoir chamber from outside the tensioner body, the oil supply path including a tensioner body oil supply hole extending from outside the tensioner body through to an inner circumferential surface of the plunger bore, a plunger oil supply hole extending from an outer circumferential surface of the cylindrical plunger through to an inner circumferential surface of the plunger hole, and an oil supply space formed between the inner circumferential surface of the plunger bore and the outer circumferential surface of the cylindrical plunger and communicating the tensioner body oil supply hole with the plunger oil supply hole, the oil supply space being formed by a front-end communication groove formed on the inner circumferential surface of the plunger bore and communicating with the tensioner body oil supply hole, and a rear-end communication groove formed on the outer circumferential surface of the cylindrical plunger and causing the front-end communication groove to communicate with the plunger oil supply hole, wherein the tensioner satisfies relations La<Lb and La<Lc, where La represents a length along the protruding direction of the cylindrical plunger between a rear end of the front-end communication groove and a front end of the rear-end communication groove, Lb represents a length along the protruding direction of the cylindrical plunger between the rear end of the front-end communication groove and a rear end of an opening edge of the plunger oil supply hole, and Lc represents a length along the protruding direction of the cylindrical plunger between the front end of the rear-end communication groove and a front end of an opening edge of the tensioner body oil supply hole, in a state in which the cylindrical plunger is pushed to a rearmost position.

2. The tensioner according to claim 1, wherein the tensioner satisfies a relation H1=H2, where H1 represents a distance along the protruding direction of the cylindrical plunger between the front end of the rear-end communication groove and an open end of the plunger bore, and H2 represents a distance along the protruding direction of the cylindrical plunger between the rear end of the front-end communication groove and a rear end of the cylindrical plunger, in the state in which the cylindrical plunger is pushed to the rearmost position.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is an illustrative diagram illustrating one mode of use of a tensioner according to one embodiment of the present invention;

(2) FIG. 2 is a cross-sectional view illustrating a schematic configuration of the tensioner according to one embodiment of the present invention;

(3) FIG. 3 is a cross-sectional view illustrating a schematic configuration of a tensioner body of the tensioner shown in FIG. 1;

(4) FIG. A is a cross-sectional view illustrating a schematic configuration of a plunger of the tensioner shown in FIG. 1;

(5) FIG. 5 is an enlarged cross-sectional view illustrating a schematic configuration of relevant parts in the tensioner shown in FIG. 1;

(6) FIG. 6 is a schematic diagram illustrating the tensioner of FIG. 1 in a state in which the plunger is protruded at a maximum set stroke;

(7) FIGS. 7A and 7B are schematic diagrams illustrating a configuration of relevant parts in one example of an existing tensioner, FIG. 7A illustrating a state in which the plunger is pushed to a rearmost position, and FIG. 7B illustrating a state in which the plunger is protruded at a maximum set stroke; and

(8) FIGS. 8A and 8B are schematic diagrams illustrating a configuration of relevant parts in another example of an existing tensioner, FIG. 8A illustrating a state in which the plunger is pushed to a rearmost position, and FIG. 8B illustrating a state in which the plunger is protruded at a maximum set stroke.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(9) Hereinafter, a tensioner according to one embodiment of the present invention will be described with reference to the drawings.

(10) As illustrated in FIG. 1, the tensioner 100 of this embodiment is incorporated in a chain drive device used in a timing system or the like of a car engine to apply appropriate tension to the slack side of a drive chain CH passed over a plurality of sprockets S1 to S3 via a tensioner lever G to reduce vibration during the drive.

(11) As illustrated in FIG. 2, the tensioner 100 includes a tensioner body 110 having a plunger bore 111 that is open on a front side, a cylindrical plunger 120 slidably accommodated in the plunger bore 111 and having a plunger hole 121 that is open on a rear side, a check valve 130 partitioning a space between the tensioner body 110 and the plunger 120 into an oil reservoir chamber 101 on the front side and an oil pressure chamber 102 on the rear side and allowing oil to flow into the oil pressure chamber 102 while stopping the oil from flowing reversely into the oil reservoir chamber 101, a main biasing means 140 accommodated in the oil pressure chamber 102 such as to freely expand and contract and urging the plunger 120 in a protruding direction, and an oil supply path 105 that supplies oil to the oil reservoir chamber 101 from outside the tensioner body 110.

(12) The tensioner body 110 is made of metal such as aluminum alloy, for example, or synthetic resin and the like, and includes, as illustrated in FIG. 3, a columnar main body 112 having the plunger bore 111, and an attachment part. 113 integrally formed with the main body 112 to be used for securely attaching the tensioner to an engine block or the like. The attachment part. 113 has attachment holes 113a for bolts or the like to pass through.

(13) The tensioner body 110 is formed with a tensioner body oil supply hole 114 that extends from outside the tensioner body 110 through to an inner circumferential surface of the plunger bore 111.

(14) The plunger 120 is made of metal such as iron and formed as a cylindrical dead end hole.

(15) The plunger hole 121 of the plunger 120 includes a large-diameter hole 121a formed on the rear side and a small-diameter hole 121b on the front side continuously formed on the front side of the large-diameter hole 121a via a step 121c as illustrated in FIG. 4. The large-diameter hole 121a and small-diameter hole 121b are formed to be concentric with each other.

(16) The plunger 120 is formed with a plunger oil supply hole 122 extending from an outer circumferential surface thereof through to an inner circumferential surface of the small-diameter hole 121b that defines the oil reservoir chamber 101.

(17) The check valve 130 is made up of a ball seat 131 disposed in tight contact with an end face of the step 121c inside the large-diameter hole 121a of the plunger hole 121, a check ball 132 that can be seated on the ball seat 131 in tight contact therewith, and a retainer 133 arranged on the front side of the check ball 132 to restrict the movement of the check ball 132.

(18) The components making up the check valve 130 are each made of metal or synthetic resin and the like.

(19) The check valve 130 may have any specific configuration as long as it allows the oil to flow into the oil pressure chamber 102 but stops the oil from flowing reversely into the oil reservoir chamber 101. For example, a spring that urges the check ball 132 toward the ball seat 131 may be disposed between the check ball 132 and the retainer 133.

(20) The main biasing means 140 is a coil spring made of a round wire coiled into a helical shape, for example.

(21) The main biasing means 140 is set inside the oil pressure chamber 102, with its front end abutted on a flange part of the retainer 133 and its rear end abutted on a bottom part of the plunger bore 111 such that the coil axis extends along the center axis of the plunger 120. This way, the main biasing means 140 urges the plunger 120 to the front side, as well as presses the retainer 133 and ball seat 131 of the check valve 130 against the step 121c to retain the check valve 130 inside the large-diameter hole 121a.

(22) The oil supply path 105 is made up of the tensioner body oil supply hole 114, the plunger oil supply hole 122, and an oil supply space 106 formed between an inner circumferential surface of the plunger bore 111 and an outer circumferential surface of the plunger 120 to cause the tensioner body oil supply hole 114 to communicate with the plunger oil supply hole 122, as also illustrated in FIG. 5.

(23) In the tensioner 100 of this embodiment, a front-end communication groove 115 that communicates with the tensioner body oil supply hole 114 is formed on the inner circumferential surface of the plunger bore 111 of the tensioner body 110, and a rear-end communication groove 125 that communicates with the plunger oil supply hole 122 is formed on the outer circumferential surface of the plunger 120. That is, the oil supply space 106 is formed by the front-end communication groove 115 and the rear-end communication groove 125 that are set back from each other in the radial direction of the plunger 120.

(24) The front-end communication groove 115 extends from a point spaced from the open end face of the plunger bore 111 rearward in the protruding direction of the plunger all around the inner circumferential surface of the plunger bore 111.

(25) The rear-end communication groove 125 extends forward in the protruding direction of the plunger in a rear end portion of the circumferential wall that defines the small-diameter hole 121b all around the outer circumferential surface of the plunger 120.

(26) In the tensioner 100 of this embodiment, it is preferable to form the front-end communication groove 115 and the rear-end communication groove 125 such as to satisfy relations La<Lb and La<Lc, where La represents a length along the protruding direction of the plunger between the rear end of the front-end communication groove 115 and the front end of the rear-end communication groove 125, Lb represents a length along the protruding direction of the plunger between the rear end of the front-end communication groove 115 and the rear end of the opening edge of the plunger oil supply hole 122, and Lc represents a length along the protruding direction of the plunger between the front end of the rear-end communication groove 125 and the front end of the opening edge of the tensioner body oil supply hole 114, in a state in which the plunger 120 is pushed to a rearmost position as illustrated in FIG. 5.

(27) This configuration allows for larger stroke settings for the plunger 120 as compared to tensioners in which the oil supply space 106 is provided only by a communication groove on the inner circumferential surface of the plunger bore 111, or tensioners in which the oil supply space 106 is provided only by a communication groove on the outer circumferential surface of the plunger 120.

(28) It is also preferable to form the front-end communication groove 115 and the rear-end communication groove 125 such as to satisfy a relation H1=H2, where H1 represents a distance along the protruding direction of the plunger between the front end of the rear-end communication groove 125 and the open end of the plunger bore 111, and H2 represents a distance along the protruding direction of the plunger between the rear end of the front-end communication groove 115 and the rear end of the plunger 120 in the state in which the plunger 120 is pushed to the rearmost position. This configuration enables the stroke of the plunger 120 to be as large as possible.

(29) According to the tensioner 100 of this embodiment, since the oil supply space 106 that communicates the tensioner body oil supply hole 114 with the plunger oil supply hole 122 is formed by the front-end communication groove 115 and the rear-end communication groove 125 that are set back from each other in the radial direction of the plunger 120, the seal limits of the seal provided by the wall surface of the tensioner body 110 for preventing the oil from leaking out are alleviated.

(30) For a tensioner 200 in which the oil supply space 106 is formed only by a communication groove 226 provided on the outer circumferential surface of the plunger 120 as illustrated in FIG. 7A, it is required to form the communication groove 226 such as to communicate the tensioner body oil supply hole 114 with the plunger oil supply hole 122 in a state in which the plunger 220 is pushed to the rearmost position.

(31) In contrast, the rear-end communication groove 125 on the outer circumferential surface of the plunger 120 of the tensioner 100 of this embodiment only needs to cause the front-end communication groove 115 that communicates with the tensioner body oil supply hole 114 to communicate with the plunger oil supply hole 122. This allows the sealing properties provided by the wall surface of the tensioner body 110 to be secured as illustrated in FIG. 6 and prevents oil leakage to the outside. Accordingly, the distance H1 along the protruding direction of the plunger between the open end of the plunger bore 111 and the front end of the rear-end communication groove 125 can be set larger as compared to the tensioner 200 having the oil supply space 106 formed only by the communication groove 226 on the outer circumferential surface of the plunger 120, as a result of which the maximum set stroke Smax of the plunger 120 can be increased.

(32) For a tensioner 300 in which the oil supply space 106 is formed only by a communication groove 316 provided on the inner circumferential surface of the plunger bore 111 as illustrated in FIG. 8A, it is required to form the communication groove 316 such as to communicate the tensioner body oil supply hole 114 with the plunger oil supply hole 122 in a state in which the plunger 320 is pushed to the rearmost position.

(33) In contrast, the front-end communication groove 115 on the inner circumferential surface of the plunger bore 111 of the tensioner 100 of this embodiment only needs to cause the rear-end communication groove 125 that communicates with the plunger oil supply hole 122 to communicate with the tensioner body oil supply hole 114. This allows the sealing properties provided by the wall surface of the tensioner body 110 to be secured as illustrated in FIG. 6 and prevents oil leakage to the outside. Accordingly, the distance H2 along the protruding direction of the plunger between the rear end of the plunger 120 and the rear end of the front-end communication groove 115 can be set larger as compared to the tensioner 300 having the oil supply space 106 formed only by the communication groove 316 on the inner circumferential surface of the plunger bore 111, as a result of which the maximum set stroke Smax of the plunger 120 can be increased.

(34) Accordingly, the tensioner 100 of this embodiment enables a sufficient amount of stroke for the plunger 120 to be secured without changing the size of the tensioner body 110. Thus tension fluctuations of the chain can be reliably compensated, and size and weight reductions of the tensioner 100 are made possible, which improves the space efficiency and contributes to better fuel economy.

(35) While one embodiment of the present invention has been described in detail, the present invention is not limited to the above-described embodiment and may be carried out with various design changes without departing from the scope of the present invention set forth in the claims.

(36) For example, while the tensioner is described as a component, to be incorporated in a timing system of a car engine in the embodiment above, the purpose of use of the tensioner is not limited to this specific application.

(37) While the tensioner is described as a component that applies tension to a drive chain via a tensioner lever in the embodiment above, the plunger can directly guide the drive chain slidably with a distal end thereof to apply tension to the drive chain.

(38) The tensioner may not necessarily be applied to a transmission mechanism with a drive chain but can also be used for similar transmission mechanisms that use belts, ropes and the like, and can be applied in a variety of industrial fields where it is desired to apply tension to an elongated component.

(39) While the housing accommodating the plunger is described as the component known as a tensioner body that is attached to an engine block or the like in the embodiment described above, the housing is not limited to the specific form described above and may be a cylindrical component known as a sleeve inserted into a body hole formed in the tensioner body.