JP7488463B2 - Tensioner - Google Patents

Description

The present invention relates to a tensioner that applies the appropriate tension to a moving chain, belt, etc.

Conventionally, tensioners have been used to properly maintain tension in chains and the like. For example, in a chain guide mechanism in which a tensioner lever guides a transmission chain that is endlessly wound between sprockets on the crankshaft and camshaft in the engine compartment, a tensioner lever is biased by the tensioner to properly maintain tension in the chain.

For example, as shown in FIG. 6, a timing chain CH is endlessly wound between a driving sprocket S1 attached to a crankshaft in the engine compartment and a pair of driven sprockets S2, S3 attached to a camshaft, and this timing chain CH is guided by a oscillating chain guide G1 and a fixed chain guide G2 to form a chain guide mechanism.
The fixed chain guide G2 is fixed in the engine room by two mounting shafts B1, B2, and the swingable chain guide G1 is mounted in the engine room so as to be swingable around the mounting shaft B0 within the plane in which the timing chain CH runs.
The tensioner 500 presses against the swingable chain guide G1 to properly maintain tension in the timing chain CH and suppress vibrations.

As a known tensioner used in such a chain guide mechanism, for example, a ratchet-type tensioner is known, as described in Japanese Patent Application Laid-Open No. 2003-233996.
The ratchet tensioner (A1) described in Patent Document 1 comprises a tensioner body (tensioner housing A7) having a cylindrical plunger accommodating hole (A12) that is open on one side, a cylindrical plunger (A8) that is slidably inserted into the plunger accommodating hole (A12) and biased toward the open side of the plunger accommodating hole (A12), and an oil pressure chamber (high pressure chamber H) formed by the plunger accommodating hole (A12) and the plunger (A8).
Furthermore, a ratchet A16 is supported in a freely swingable manner by a ratchet shaft (A15) in the ratchet tensioner (A1), and a ratchet mechanism is formed by the meshing of ratchet teeth (T) formed on the side of the plunger (A8) with ratchet pawls (A17, A18) formed on the ratchet (16), thereby preventing displacement of the plunger (A8) in the backward direction.
This prevents excessive tension from being applied to the chain from the plunger (A8) while it is running, and when the plunger (A8) protrudes a predetermined amount from the plunger accommodating hole (A12) as the chain stretches, the position of the ratchet teeth (T) that mesh with the ratchet pawls (A17, A18) shifts, and the oscillating chain guide G1 can oscillate and displace to follow the stretch of the chain.
Furthermore, the ratchet mechanism can prevent the plunger from protruding during assembly, maintenance, etc., by using a simple mechanism for fixing the ratchet pawl.

Japanese Patent Application Laid-Open No. 11-344086

This type of ratchet tensioner has the risk of being heavy due to the large number of components in the ratchet mechanism, and high-precision machining is required for the mating parts between the ratchet teeth and the ratchet pawl, which could result in higher costs than tensioners that do not use a ratchet mechanism.

Furthermore, when installed in a diesel engine, the ratchet pawl and ratchet teeth are easily worn down by soot, so it may be possible to use a tensioner without a ratchet mechanism.
However, if the ratchet mechanism is not provided, it is not possible to easily prevent the plunger from coming loose using the ratchet mechanism, and there is a risk that work efficiency will decrease, such as the plunger suddenly coming off the tensioner during installation on the engine.

The present invention aims to solve the above problems by providing a tensioner that has a simple structure, prevents costs from increasing, and can easily prevent the plunger from coming loose without the need for a ratchet mechanism.

The tensioner of the present invention is a chain tensioner comprising a tensioner body having a cylindrical plunger accommodating hole that is open on one side, a cylindrical plunger that is slidably inserted into the plunger accommodating hole and is urged towards the open side of the plunger accommodating hole, and an oil pressure chamber formed by the plunger accommodating hole and the plunger, wherein the plunger is provided with a flat portion in which part of the side of the plunger is formed into a flat shape, and the tensioner body has a ratchet attachment space, a fixing hole that is arranged in a position different from the ratchet attachment hole and that interferes with the inner circumferential surface of the plunger accommodating hole in a direction not parallel to the sliding direction axis of the plunger within the ratchet attachment space, and a plunger stopper that is arranged to be slidable on the flat portion , and the plunger stopper is arranged in a position where the outer circumferential surface of the plunger stopper can always be in contact with the flat portion , thereby solving the above-mentioned problems.

According to the tensioner of claim 1, the plunger is provided with a flat portion formed by forming a part of the side of the plunger into a flat shape, and the tensioner body has a space for attaching a ratchet and a plunger stopper arranged so as to be able to slide along the flat portion. Therefore, for example, by forming a flat portion leaving the end of the plunger, when the plunger is slid along the flat portion by the plunger stopper, the plunger stopper catches on the end of the plunger, and the plunger can be easily and reliably prevented from coming loose.
In addition, since the plunger is prevented from coming loose by simply sliding the plunger stopper against the flat surface , the frictional force on the plunger can be reduced compared to when a ratchet mechanism is used, and the plunger's ability to follow chain vibrations can be improved.
In addition, since the fixing hole interferes with the inner surface of the plunger accommodating hole in a direction that is not parallel to the sliding direction axis, the plunger stopper can be easily positioned and fixed by, for example, passing a pin through the fixing hole and holding the plunger stopper between the tensioner body and the pin, and the plunger stopper can also be easily attached and detached by attaching and detaching the pin.
Furthermore, if a pin is passed through the fixing hole, even if the plunger stopper is accidentally removed, the pin can prevent the plunger from coming off.
Furthermore, since the same tensioner body is used as that used in tensioners having a ratchet mechanism, there is no need to prepare multiple types of tensioner bodies depending on whether or not the tensioner has a ratchet mechanism, thereby improving manufacturing efficiency.
Furthermore, compared to tensioners with ratchet mechanisms, the number of parts can be reduced, weight increase can be suppressed, and fuel economy can be improved through weight reduction.
Furthermore, since the plunger stopper is always in contact with the flat surface , the plunger does not rotate within the plunger receiving hole, suppressing wear caused by relative rotation between the spring and the plunger top surface as the plunger rotates .

According to the configuration described in claim 2, the end of the flat portion that is inserted into the plunger accommodating hole is composed of an inclined surface formed at a predetermined angle to the outer peripheral surface of the plunger, so that when the plunger attempts to jump out of the plunger accommodating hole, the impact load between the pin and the inclined surface of the plunger can be suppressed, and wear and damage to the pin and plunger can be prevented.
According to the configuration described in claim 3 , the plunger stopper is formed in a rod shape that can be inserted into the fixing hole and fixed in position, thereby further reducing the number of parts, suppressing cost increases, and further improving fuel efficiency through weight reduction.
According to the configuration described in claim 4 , the plunger stopper is configured to be rotatable around the central axis of the fixing hole as the center of rotation, thereby reducing the frictional force generated when the plunger stopper slides against the flat portion , and suppressing wear on the plunger stopper and the flat portion .

According to the configuration recited in claim 5 , the plunger is provided with a communication groove that connects from the end of the flat portion to the open end of the oil pressure chamber of the plunger. Therefore, by installing the tensioner so that the plunger stopper is located above the plunger, the communication groove can be located on the upper surface of the plunger hole, and therefore air in the oil pressure chamber when the engine is started can be quickly released through the communication groove.

1 is a perspective view of a tensioner 100 according to an embodiment of the present invention. FIG. 2 is a perspective view of a plunger 120 according to an embodiment of the present invention. 1 is a cross-sectional view of a tensioner 100 according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing an initial state of use of the tensioner 100 according to one embodiment of the present invention. FIG. 2 is a cross-sectional view showing a state in which the plunger 120 of the tensioner 100 according to one embodiment of the present invention is protruded. FIG. 5 is an explanatory diagram of a tensioner 500 used in a chain guide mechanism of an engine.

A tensioner 100 according to one embodiment of the present invention will now be described with reference to the drawings.
For the sake of explanation, the tensioner 100 is illustrated so that the protruding direction of the plunger 120 is vertically upward, and the configuration of the chain guide mechanism other than the tensioner 100, the engine, etc. are not illustrated.

As shown in Figures 1 to 3, the tensioner 100 has a tensioner body 110 with a cylindrical plunger accommodating hole 111 that is open on one side, a cylindrical plunger 120 that is biased toward the open side of the plunger accommodating hole 111, an oil pressure chamber 121 formed by the plunger accommodating hole 111 and the plunger 120, and a round rod-shaped plunger stopper 130 that prevents the plunger 120 from coming out.

The tensioner body 110 is provided with a mounting hole 116 used when mounting the tensioner body 110 to an engine, and a fixing hole 115 through which a plunger stopper 130 can be inserted.
The fixing hole 115 penetrates the tensioner body 110 in a direction that interferes with the inner peripheral surface of the plunger accommodating hole 111 and in a direction perpendicular to the sliding axis of the plunger 120 .
The plunger stopper 130 is connected to the tensioner body 110 so as to be rotatable about the central axis of the plunger stopper 130 .

A temporary fixing hole 117 is provided at the open end of the plunger accommodating hole 111, through which a temporary fixing pin 131 can be inserted.
An oil reservoir chamber 113 connected to an oil supply passage 114 is provided at the bottom of the plunger accommodating hole 111, and a check valve unit 112 is provided between the oil reservoir chamber 113 and the oil pressure chamber 121 to prevent oil flowing into the oil pressure chamber 121 from flowing back into the oil reservoir chamber 113.
The oil pressure chamber 121 is filled with oil supplied from the oil supply passage 114 , and a coil spring 124 is provided in the oil pressure chamber 121 to bias the plunger 120 in a direction protruding from the plunger receiving hole 111 .

A reduced diameter portion 127 through which a temporary fixing pin 131 can pass is formed near the open end of the plunger 120 in the plunger receiving hole 111 .
A chamfered flat surface 123 is provided on part of the outer circumferential surface of the plunger 120 , and a communication groove 122 that connects the flat surface 123 to the oil pressure chamber 121 is provided below the flat surface 123 .

Next, how the tensioner 100 according to one embodiment of the present invention prevents the plunger 120 from coming off will be described with reference to FIGS.
First, as shown in FIG. 4, the tensioner 100 is attached to a predetermined position on the engine via a screw or the like in the mounting hole 116, and then the temporary fixing pin 131 inserted in the temporary fixing hole 117 is removed. The plunger 120 moves to the open side of the plunger accommodating hole 111 due to the biasing force of the coil spring 124, and presses the chain via the oscillating chain guide.
At this time, the plunger stopper 130 slides against the flat surface portion 123 of the plunger 120, which may apply a frictional force to the plunger 120. However, since the plunger stopper 130 is connected so as to be rotatable around the central axis of the plunger stopper 130 as the center of rotation, the frictional force applied to the plunger 120 can be reduced, and wear of the flat surface portion 123 and the plunger stopper 130 can also be suppressed.

After the plunger 120 exerts a pressing force on the chain, the engine is started and the chain begins to rotate.
At this time, it may be the case that the oil pressure chamber 121 is not fully filled with oil and air remains, but because the oil pressure chamber 121 and the flat surface portion 123 are in communication with each other via the communication groove 122, the air within the oil pressure chamber 121 can be quickly discharged to the outside of the tensioner 100 through the communication groove 122.

Furthermore, by installing the tensioner 100 so that the plunger stopper 130 side is positioned higher than the plunger 120, air that has accumulated in the upper part of the oil pressure chamber 121 can be more quickly discharged to the outside of the tensioner 100 through the communicating groove 122.
Furthermore, because the plunger stopper 130 slides against the flat portion 123, the plunger 120 will not rotate about the central axis of the plunger accommodation hole 111 due to vibration or the like, and the orientation of the communicating groove 122 can be fixed in a position where the air in the oil pressure chamber 121 can always be quickly discharged.

The plunger 120 pressing the chain applies force to the oil to leak out of the plunger 120 through the communicating groove 122 by damping the vibration generated when the chain slides and transmits to the oscillating chain guide after the chain starts.
At this time, the flow passage of the communication groove 122 is sufficiently narrowed so that the plunger 120 can maintain an appropriate damping characteristic.
When the oil in the oil pressure chamber 121 leaks out of the plunger 120 and the pressure in the oil pressure chamber 121 drops, the check valve unit 112 is opened and oil is replenished from the oil supply passage 114 through the oil reservoir chamber 113 to the oil pressure chamber 121, so that the plunger 120 can reliably maintain appropriate damping characteristics.

As the chain stretches, the plunger 120 protrudes further from the plunger receiving hole 111 due to the biasing force of the coil spring 124, and the volume of the oil pressure chamber 121 increases.
At this time, the pressure in the oil pressure chamber 121 drops, so the check valve unit 112 is opened and oil is replenished from the oil reservoir chamber 113 to the oil pressure chamber 121, allowing the plunger 120 to maintain appropriate damping characteristics.

When the chain becomes fully stretched or when replacing the tensioner 100, the plunger 120 will attempt to come out of the plunger accommodating hole 111 due to the biasing force of the coil spring 124. However, as shown in FIG. 5, the plunger stopper 130 catches on the lower end of the flat portion 123, i.e., the outer peripheral surface of the plunger 120 that is not chamfered, so that the plunger 120 is prevented from coming out of the plunger accommodating hole 111 with a simple structure, and the tensioner 100 can be replaced safely.

The tensioner 100, which is one embodiment of the present invention, can be constructed by adding fixing holes 115 to a tensioner body of the same shape as a ratchet tensioner that has not been machined to attach a ratchet mechanism, eliminating the need to prepare multiple types of tensioner bodies before additional machining depending on whether or not they have a ratchet mechanism, improving design and manufacturing efficiency.

Although the embodiments of the present invention have been described above in detail, the present invention is not limited to the above embodiments, and various design changes can be made without departing from the invention described in the claims.

In the above-described embodiment, the plunger stopper is described as being formed in a round bar shape, but the shape of the plunger stopper is not limited to this, and may be formed in, for example, a polygonal prism shape, and the surface that slides against the planar portion may be a flat surface.
In addition, in the above-described embodiment, the plunger stopper has been described as being rotatably connected with the central axis of the plunger stopper as the center of rotation, but the configuration of the plunger stopper is not limited to this, and for example, the plunger stopper does not have to rotate.

Furthermore, in the above-described embodiment, the oil within the oil pressure chamber is described as leaking out through the communicating groove, but the configuration of the plunger is not limited to this. For example, an oil drain hole may be provided which connects the reduced diameter portion with the oil pressure chamber, or an oil drain hole may be provided so as to pass through the plunger from the lower end of the flat portion .
In addition, in the above-described embodiment, the fixing hole is described as penetrating the tensioner body in a direction that interferes with the inner surface of the plunger accommodating hole and in a direction perpendicular to the sliding direction axis of the plunger, but the configuration of the fixing hole is not limited to this, and for example, as long as it reaches a position where it interferes with the plunger, both ends do not have to penetrate all the way to the outer surface side of the tensioner body.
Furthermore, the direction of the fixing hole does not have to be perpendicular to the sliding direction axis of the plunger, so long as the fixing hole is formed so as to be able to fix the plunger (not parallel to the sliding direction axis of the plunger).

REFERENCE SIGNS LIST 100, 500: tensioner 110: tensioner body 111: plunger receiving hole 112: check valve unit 113: oil storage chamber 114: oil supply passage 115: fixing hole 116: mounting hole 117: temporary fastening hole 120: plunger 121: oil pressure chamber 122: communication groove 123: flat surface
Reference Signs List 124 Coil spring 125 Oil leak passage 126 Oil discharge hole 127 Reduced diameter portion 130 Plunger stopper 131 Temporary fixing pin S1 Drive sprocket S2 Driven sprocket S3 Driven sprocket CH Timing chain G1 Swinging chain guide G2 Fixed chain guide B0, B1, B2 Mounting shaft

Claims (5)

A tensioner comprising: a tensioner body having a cylindrical plunger accommodating hole open on one side; a cylindrical plunger slidably inserted into said plunger accommodating hole and biased toward the open side of said plunger accommodating hole; and an oil pressure chamber formed by said plunger accommodating hole and said plunger,
The plunger is provided with a flat surface portion in which a part of a side surface of the plunger is formed into a flat surface ,
The tensioner body has a ratchet mounting space, a fixing hole arranged in the ratchet mounting space at a position different from the ratchet mounting hole, the fixing hole interfering with the inner peripheral surface of the plunger accommodating hole in a direction not parallel to the sliding direction axis of the plunger, and a plunger stopper arranged slidably with respect to the flat portion ,
The tensioner is characterized in that the plunger stopper is disposed at a position where an outer circumferential surface of the plunger stopper can always come into contact with the flat portion . 2. The tensioner according to claim 1, wherein an end of said flat portion that is inserted into said plunger receiving hole is configured as an inclined surface formed at a predetermined angle to an outer peripheral surface of said plunger. The tensioner according to claim 1, characterized in that the plunger stopper is formed in a rod shape that can be inserted into the fixing hole and fixed in position. 4. The tensioner according to claim 3 , wherein the plunger stopper is configured to be rotatable about a central axis of the fixing hole. 5. A tensioner according to claim 1, wherein the plunger is provided with a communication groove extending from an end of the flat portion to an end of the plunger on an open side of the oil pressure chamber.

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