To provide a tensioner that enables, with a simple structure, reduction of installation space of the tensioner and reduction of production costs. The tensioner includes a plunger, a housing, a spring, and a locking mechanism that stops the plunger from projecting out to the front side. The locking mechanism includes a first locking member and a second locking member. The first locking member includes a first spring holder arranged on a first side of a first end of the spring, and a restrained part. The second locking member includes a second spring holder arranged on a second side of a second end of the spring, and a movement restricting part that restricts movement of the restrained part toward the first side. The restrained part and movement restricting part are configured to releasably engage with each other.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a tensioner that applies appropriate tension to a running chain, belt, or the like.

2. Description of the Related Art

It has been common practice to use a tensioner for maintaining appropriate tension in a chain or the like. For example, a known chain guide mechanism uses a tensioner to bias a tensioner lever for slidably guiding a drive chain, such as an endless roller chain passing over respective sprockets of a crankshaft and a cam shaft inside an engine room, to maintain appropriate tension of the chain or the like.

One known tensioner510used in such a chain guide mechanism includes, as shown inFIG. 10, a plunger520having a plunger hole that is open on the rear side, a housing530having a plunger accommodating hole that is open on the front side for accommodating the plunger520, and a spring accommodated in an oil pressure chamber formed between the plunger520and the housing530so as to be able to expand and contract and to urge the plunger520toward the front side (see, for example, Japanese Patent Application Laid-open No. 2004-44749).

Since it is necessary to prevent the plunger520from coining out frontward before it is set to a chain or the like, such tensioner510requires a locking mechanism that stops the plunger520from coming out frontward.

A locking mechanism that is pivotably attached to the housing530via a ratchet pin561supported on the housing530, as shown inFIG. 10, has been widely used. The locking mechanism includes a ratchet562that can engage with the plunger520, a stopper lever563fixed to one end of the ratchet pin561, and a stopper pin564extending through the stopper lever563and housing530for stopping rotation of the stopper lever563thereby to stop rotation of the ratchet562.

Another example of a locking mechanism has a plunger stopper hook566pivotably supported on a pivot pin565that is fixed to the housing530, and engaged with a locking pin567fixed to the plunger520, as shown inFIG. 11for stopping the plunger520from coming out frontward (see, for example, Japanese Patent Application Laid-open No. 2003-35343).

SUMMARY OF THE INVENTION

One problem with the tensioners shown inFIG. 10andFIG. 11is that these tensioners510need a sufficient installation space for avoiding interference with surrounding components of the engine block or front case, since the constituent elements of the locking mechanisms are disposed outside the housing.

Another problem with the tensioners shown inFIG. 10andFIG. 11is that the plunger and housing require processing such as fixing additional parts and the like, which leads to an increase in the production cost of the tensioner.

The present invention solves these problems and it is an object of the invention to provide a tensioner that enables, with a simple structure, reduction of the installation space for the tensioner and reduction of production costs.

The present invention solves the problems above by providing a tensioner including: a plunger having a plunger hole that is open on a rear side; a housing having a plunger accommodating hole that is open on a front side and accommodates the plunger; a spring accommodated inside an oil pressure chamber formed between the plunger and the plunger accommodating hole so as to be able to expand and contract and to urge the plunger toward the front side; and a locking mechanism stopping the plunger from projecting out toward the front side. The spring includes a first end arranged on a first side in a front-to-back direction and a second end arranged on a second side in the front-to-back direction. The locking mechanism includes a first locking member and a second locking member. The first locking member includes a first spring holder arranged on the first side of the first end of the spring, and a restrained part. The second locking member includes a second, spring holder arranged on the second side of the second end of the spring, and a movement restricting part that restricts movement of the restrained part toward the first side. The restrained part and the movement restricting part are configured to releasably engage with each other.

According to one aspect of the present invention, the first locking member includes a first spring holder arranged on the first side of the first end of the spring, and a restrained part. The second locking member includes a second spring holder arranged on the second side of the second end of the spring, and a movement restricting part that restricts movement of the restrained part toward the first side. The restrained part and the movement restricting part are configured to releasably engage with each other, hence the first locking member and second locking member are set inside the oil pressure chamber and need not foe provided outside the tensioner, therefore interference between surrounding components of the engine block or the like and the locking members can be avoided, so that the installation space for the tensioner can be reduced.

Since the first locking member and second locking member are set inside the oil pressure chamber, no processing is required for the plunger and housing, so that an increase in the production cost of the tensioner can be avoided.

After the first locking member and second locking member are attached to the spring, they can be handled as one unit. This enables the structure of the assembling facility of the tensioner to be simplified, and reduces the costs associated with the assembling of the tensioner.

Since the first locking member and second locking member are set inside the oil pressure chamber, the volume inside the oil pressure chamber is reduced, which makes it possible to maintain the high pressure state in the oil pressure chamber with less amount of oil.

According to another aspect of the present invention, the second locking member includes a release cam formed on the second side opposite the movement restricting part. This release cam is formed to guide the restrained part in the circumferential direction to an open position where the restrained part is not locked by the movement restricting part, when the first locking member and second locking member are moved closer to each other. By moving the plunger rearward, the first locking member and second locking member can foe moved closer to each other so as to disengage the restrained part from the movement restricting part. The plunger is therefore released from the lock simply by using the fact that the plunger is pushed rearward by the tensioner lever or the like when the tensioner is installed. Also, the failure to unlock the plunger can be prevented.

According to another aspect of the present invention, the movement restricting part has a cam profile for guiding the restrained part to a restriction where movement of the restrained part, is restricted by the movement restricting part, when the first locking member and second locking member are moved away from each other. When the first locking member and second locking member are attached to the spring, the first locking member and second locking member are moved closer to each other to cause the restrained part to engage with the movement restricting part, with the spring being sandwiched between the first spring holder and second spring holder. The compressed spring is released from the load later so that the first locking member and second locking member are moved away from each other by the force of the spring. Thus the restrained part can be reliably set to the restriction position with a simple operation.

According to another aspect of the present invention, the restrained part and movement restricting part are disposed radially inside the spring. The first locking member and second locking member can thus be disposed by utilizing the space inside the spring. This way, an increase in the size of the oil pressure chamber can be avoided while a large diameter of the spring is ensured.

According to another aspect of the present invention, the first locking member includes a pin portion having the restrained part formed thereon. The second locking member includes a tubular part having the movement restricting part formed thereto. The pin portion is inserted in the tubular part. This simple structure can maintain the orientation of the first locking member and second locking member relative to each other favorably.

According to another aspect of the present invention, the movement restricting part and release cam are formed by a slit in the tubular part of the second locking member. The movement of the restrained part and of the first locking member can thus be controlled favorably and reliably with a simple structure.

According to another aspect of the present invention, at least a part of a check valve unit is accommodated in the tubular part on the second side thereof, so that the check valve unit can also be handled with the spring, first locking member, and second locking member as one unit. The costs associated with the assembling of the tensioner can thereby be reduced.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A tensioner10according to a first embodiment of the present invention will be described below with reference to the drawings.

First, the tensioner10is incorporated in a chain transmission used in a timing system or the like of a car engine. As shown inFIG. 1, the tensioner is attached to an engine block (not shown) to apply appropriate tension to the slack side of a drive chain CH passing over a plurality of sprockets S1to S3via a tensioner lever G to reduce vibration during the drive.

The tensioner10includes, as shown inFIG. 2, a plunger20having a plunger hole21that is open on a rear side, a housing30having a plunger accommodating hole31that is open on a front side and accommodates the plunger20, a check valve unit40disposed on a bottom part32side of the housing30, a spring50in the form of a coil spring accommodated inside an oil pressure chamber11that is formed between the plunger20and the plunger accommodating hole31so as to be able to expand and contract and to urge the plunger20toward the front side, and a locking mechanism60that temporarily stops the plunger20from projecting out toward the front side.

Hereinafter, various constituent elements of the tensioner10will be described with reference to the drawings.

The plunger20is made of metal such as iron or the like in the form of a cylinder with a bottom and inserted in the plunger accommodating hole31so as to be able to move back and forth in the front-to-back direction, as shown inFIG. 2.

The housing30is made of aluminum alloy or synthetic resin and the like, and includes, as shown inFIG. 2, the cylindrical plunger accommodating hole31that is open on the front side, a bottom part32formed on the rear side, and an oil supply hole33formed in the bottom part32to extend through an outer wall, of the housing30all the way into the plunger accommodating hole31.

The check valve unit40allows the oil to flow into the oil pressure chamber11from the outside through the oil supply hole33, and prevents the oil from flowing out from the oil supply hole33.

The check valve unit40is made up of a ball seat41, a spherical check ball42that can be seated on the ball seat41in tight contact therewith, a retainer43arranged on the front side of the check ball42to restrict the movement of the check ball42, and a ball spring44that urges the check ball42toward the ball seat41, as shown inFIG. 2. The ball spring44may not necessarily be provided.

The spring50has one end arranged on the rear side of the bottom of the plunger hole21(a front-side part of the plunger20) and the other end arranged on the front side of the check valve unit40(retainer43) as shown inFIG. 2. The spring50has a first end51arranged on a first side in the front-to-back direction (front side in this embodiment) and a second end52arranged on a second side in the front-to-back direction (rear side in this embodiment).

The locking mechanism60is configured to temporarily stop the plunger20from protruding to the front side by keeping the spring50compressed in the front-to-back direction. As shown inFIG. 2toFIG. 4, the locking mechanism is composed of a first locking member70and a second locking member80made of synthetic resin or metal and the like.

The first locking member70integrally includes, as shown inFIG. 2toFIG. 4, a disc-like first spring holder71disposed on the first side (front side in this embodiment) of the first end51of the spring50, a columnar pin portion72extending from the first spring holder71toward the second side, and a columnar restrained part73formed as a boss on an outer circumferential surface of the pin portion72.

The first spring holder71is disposed in contact with the bottom of the plunger hole21.

The second locking member80integrally includes, as shown inFIG. 2toFIG. 4, an annular second spring holder81disposed on the second side (rear side in this embodiment) of the second end52of the spring50, and a cylindrical tubular part82extending from the second spring holder81toward the first side.

The second spring holder81is disposed in contact with the check valve unit40(retainer43). The second spring holder81extends radially more outward than the outer circumferential surface of the tubular part82.

A hole extending through in the front-to-back direction (not shown) is formed in the center of the second spring holder81, so that oil supplied from outside of the housing30via the oil supply hole33and check valve unit40is supplied into the oil pressure chamber11through this hole and a hollow part of the tabular part82.

The tubular part82is formed with a passage slit83extending from an edge on the first side of the tubular part82toward the second side along the front-to-back direction, and a movement restricting slit84formed continuously with the passage slit83, as shown inFIG. 4.

The passage slit83extends through between the outer circumferential surface and the inner circumferential surface of the tubular part82, with a predetermined width for allowing the restrained part73to pass, as shown inFIG. 4. A portion on the first side of the passage slit83has a tapered shape such that the width is increased toward the first side.

The movement restricting slit84extends from the end on the second side (rear side) of the passage slit83diagonally relative to the circumferential and front-to-back directions toward the first side (front side) and away from the passage slit83, as shown inFIG. 4.

The movement restricting slit84extends through between the outer circumferential surface and the inner circumferential surface of the tubular part82, with a predetermined width for allowing the restrained part73to pass and be received.

An inner edge on the first side of the movement restricting slit84functions as a movement restricting part85that restricts the movement of the restrained part73of the first locking member70toward the first side, as shown inFIG. 4.

This movement restricting part85has a cam profile for guiding the restrained part73to a restriction position where the movement of the restrained part is restricted by the movement restricting part85, when the first locking member70and second locking member80are moved away from each other.

More specifically, the movement restricting part85, which extends diagonally relative to the circumferential and front-to-back directions toward the first side (front side) and away from the passage slit83as shown inFIG. 4, is configured to guide the restrained part73to the restriction position at the end of the movement restricting slit84, when the first locking member70and second locking member80are moved away from each other by the force of the spring50.

The restrained part73and movement restricting part85are thus configured to releasably engage with each other.

An inner edge on the second side of the movement restricting slit84opposite the movement restricting part85in the front-to-back direction functions as a release cam86.

This release cam86is formed to guide the restrained part73in the circumferential direction to an open position where the restrained part is not locked by the movement restricting part85, when the first locking member70and second locking member SO are moved closer to each other.

More specifically, the release cam86, which extends diagonally relative, to the circumferential and front-to-back directions toward the first side (front side) and away from the passage slit83, is configured to guide the restrained part73to the open position that is an end position on the second side of the passage slit83, when the first locking member70and second locking member80are moved closer to each other.

Next, the process of attaching the first locking member70and second locking member80to the spring50will be described below.

First, as shown inFIG. 5C, the tubular part82of the second locking member80is inserted into the spring50from the second end52side, and the pin portion72of the first locking member70is inserted into the spring50from the first end51side.

Next, with the spring50being sandwiched between the first spring holder71of the first locking member70and the second spring holder81of the second locking member80, the first locking member70and second locking member80are moved closer to each other in the front-to-back direction to compress the spring50, and the pin portion72is inserted into the tubular part82from the first side, with the restrained part73being positioned inside the passage slit83.

Next, as shown inFIG. 5B, after the first spring holder71and second spring holder81have been moved closer to each other until the restrained part73comes near the end on the second side, of the passage slit83, the first locking member70and second locking member80are rotated relative to each other so that the restrained part73is positioned inside the movement restricting slit84.

When the load on the compressed spring50is removed, the spring50resiliently restores and expands to cause the first locking member70and second locking member80to move away from each other, and the restrained part73is guided by the movement restricting part85to the restriction position at the end of the movement restricting slit84as shown inFIG. 5A. At this time, the first locking member70and second locking member80rotate relative to each other.

After that, the engagement between the restrained part73and the movement restricting part85retains the first locking member70and second locking member80at their positions relative to each other in the front-to-hack direction so that the spring50is kept compressed, and thus the spring50, first locking member70, and second locking member80can be handled as one unit.

Next, how to unlock the locking mechanism60that stops the plunger20from protruding out will be described below.

First, as shown inFIG. 5A, with the compressed spring50, first locking member70, and second locking member80assembled together as one unit being disposed inside the oil pressure chamber11, the tensioner10is installed to a predetermined position as shown inFIG. 1.

When installed, the plunger20is pushed rearward by the tensioner lever G, which causes the first locking member70and second locking member80to approach each other, so that the restrained part73is guided by the release cam86to the open position that is the end position on the second side of the passage slit33. In other words, the restrained part73and movement restricting part85are disengaged from each other by themselves. At this time, the first locking member70and second locking member80rotate relative to each other.

Next, when the plunger20is stopped from being pressed rearward, the spring50resiliently restores and expands, and the plunger20is pushed by the plunger20to protrude forward.

When the spring50expands, the first spring holder71(first locking member70) may be subjected to a rotational force from the first end51of the spring50(which acts clockwise when viewed from above, when the spring50is left-handed as in this embodiment). The movement restricting slit84is positioned relative to the passage slit83such that the restrained part73will not enter the movement restricting slit84again by this rotational force applied to the first locking member70(the movement restricting slit84is behind the passage slit83in the clockwise direction when viewed from above, in this embodiment).

Next, a tensioner10according to a second embodiment of the present invention will be described with reference toFIG. 6toFIG. 9. The second embodiment is, in part, exactly the same as the previously described first embodiment, and therefore the description of its configurations other than the differences will be omitted.

In the second embodiment, as shown inFIG. 8, at least a part of the check valve unit40(in this embodiment, the entire check valve unit40) is accommodated in the tubular part82on the second side (rear side in this embodiment) of the second locking member80, and in the hole (not shown) formed in the center of the second spring holder81.

This way, the check valve unit40can also be handled with the spring50, first stopper70, and second stopper80as one unit.

The check valve unit40may be fixed to the second locking member80. Alternatively, the check valve unit40may only be received in the second locking member80and not fixed to the second locking member80.

While embodiments of the present invention have been described above in detail, the present invention is not limited to these embodiments and may be carried out with various design changes without departing from the scope of the present invention set forth in the claims. Various configurations of several embodiments and variations thereof described above may be freely combined to form other tensioners.

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

Also, while the tensioner was described as a component that applies tension to a drive chain with a tensioner lever in the embodiments above, the plunger can directly guide the drive chain slidably with a distal end thereof to apply tension to the drive chain.

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 required to apply tension to an elongated component.

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 embodiments 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.

While the first locking member and second locking member are described as being disposed on the front side and rear side, respectively, in the embodiments described above, the first locking member and second locking member may be disposed on the rear side and front side, respectively.

While the method of releasably engaging the first locking member and second locking member in the embodiments described above uses the restrained part of the first locking member and the movement restricting part and release cam of the second locking member, the method of releasably engaging the first locking member and second locking member is not limited to the one described above and any other methods can be employed.

While the first locking member is described as having a pin portion in the embodiments described above, the first locking member is not limited to the specific form described above. For example, the first locking member may have a tubular part extending from the first spring holder toward the second side, and this tubular part may be disposed radially inside or outside the tubular part of the second locking member.

While the restrained part of the first locking member and the movement restricting part (and release cam) of the second locking member are described as being disposed radially inside the spring in the embodiments described above, these restrained part and movement restricting part (and release cam) may be disposed radially outside the spring.