WO2003038307A1

WO2003038307A1 - Chain tensioner

Info

Publication number: WO2003038307A1
Application number: PCT/JP2002/011481
Authority: WO
Inventors: Tomoyoshi Izutsu; Seiji Sato; Shigeyoshi Ito; Hiroshi Munetoki
Original assignee: Ntn Corporation; Daihatsu Motor Co., Ltd.
Priority date: 2001-11-02
Filing date: 2002-11-01
Publication date: 2003-05-08
Also published as: JP2003202059A

Abstract

A plunger (4) and a spring (6) that presses outward the plunger (4) are assembled into a cylinder chamber (2) formed in a housing (1). The housing (1) is provided with an oil supply passage (8) communicating with a pressure chamber (7) that is formed behind the plunger (4). The outside diameter of the housing (1) has substantially the same diameter over the entire axial length thereof, and the housing (1) is inserted into an installation hole (20) that is formed in an object (B) to which a tensioner is mounted, so that a chain tensioner is in an assembled state. The assembly of the chain tensioner is thus facilitated.

Description

Light

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a chain transmission, and more particularly to a chain tensioner for maintaining a constant tension of a chain of a camshaft driving chain transmission. Conventional technology

As a chain tensioner that keeps the tension of the chain of the camshaft drive chain transmission constant, a plunger is installed in a threading chamber formed in the housing, and the plunger is mounted on the outer ring.

And a spring that presses in a direction is provided. The housing is provided with an oil supply passage communicating with a pressure chamber formed at the back of the plunger, and is provided to the plunger by hydraulic oil supplied from the oil supply passage into the pressure chamber. A device in which the pushing force is buffered is conventionally known.

The chain tensioner having the above configuration includes an exterior type and an interior type (see U.S. Pat. No. 5,658,212 and Japanese Patent No. 3,243,226).

As shown in Fig. 10, in the case of an exterior type chain tensioner, the engine cover

Insert the housing 71 of the above chain tensioner into the mounting hole 61 provided in 60, and tighten the flange 72 provided at the rear end of the housing 71 by tightening the port 75 to the engine cover 60. To fix it.

On the other hand, in the case of an interior type chain tensioner, as shown in Fig. 11, a plurality of mounting pieces 74 are formed on the outer periphery of the housing 73, and each mounting piece 74 is tightened with a port 75. Therefore, it is fixed to the engine block 61.

The plunger is used for both the exterior and interior chain tensioners.

The chain guide 64, which can swing about the shaft 63, is pressed by the tube 76 to tension the cam shaft drive chain 65. Problems to be solved by the invention

By the way, since both the external type and the internal type chain tensioners are fixed to the engine cover 60 or the engine block 61 by tightening the port 75, there is a disadvantage that the mounting is troublesome. Also, the housings 71 and 73 are Since it is necessary to provide the flanges 72 and the mounting pieces 74, it becomes heavy, and moreover, it is necessary to secure a mounting space for mounting the flanges 72 and the mounting pieces 74 on the engine cover 60. The layout is often constrained and there is also the disadvantage of low design flexibility.

An object of the present invention is to facilitate the assembling and weight reduction of a chain tensioner, and to increase the degree of freedom in design. Means for solving the problem

In order to solve the above-mentioned problems, according to the present invention, a movable plunger and a spring that presses the plunger outward are incorporated into a cylinder chamber formed in a housing. A chain tensioner that is provided with an oil supply passage communicating with a pressure chamber formed at the back of the plunger, and that buffers a pushing force applied to the plunger by hydraulic oil supplied from the oil supply passage into the pressure chamber. The outer diameter of the tensioner is made cylindrical with almost the same diameter over the entire length in the axial direction, and the housing is inserted into a mounting hole formed in the tensioner mounting target to be assembled.

According to the above configuration, the chain tensioner can be assembled by forming a mounting hole in the tensioner mounting target and inserting a housing into the mounting hole, so that the mounting is easy, and Since it is not necessary to form a mounting flange and mounting piece on the housing, it is possible to reduce the weight of the chain tensioner, and it is not necessary to secure a large space when assembling the chain tensioner. The degree of freedom in design around can be increased.

Here, when the oil supply passage is formed of a through-hole penetrating the closed end wall of the cylinder chamber in the axial direction, an oil passage communicating with the oil supply passage is provided at the closed end of the mounting hole. At this time, the housing moves in the direction of coming out of the mounting hole due to the pressure of the hydraulic oil supplied to the oil passage due to the area difference between the outer surface and the inner surface of the closed end wall of the cylinder chamber, and conversely, the plunger moves to the bottom of the cylinder chamber. There is a risk of being pushed toward. Here, if the moving amount of the housing, that is, the pushing amount of the plunger is large, the housing falls off from the mounting hole.

In order to prevent such inconvenience from occurring, after preventing the plunger from retreating more than a predetermined amount toward the bottom surface of the cylinder chamber between the housing and the plunger, _{C A} female screw is provided on the inner periphery of the opening of the cylinder chamber as a retracting restricting device for the plunger, which can prevent the plunger from being pushed in by a predetermined amount or more by providing retraction restricting means. A male thread to be engaged is formed, and a thread flank of the female thread and the male thread is formed in a sawtooth shape in which a pressure-side flank receiving an axial pushing force applied to the plunger is larger than a flank angle of a play-side flank. It is also possible to employ a thread provided with a lead angle at which the plunger moves outward by the elasticity of the spring by the elasticity of the spring, and preventing the plunger from retreating by the engagement of the play-side flanks of the female screw and the male screw. In monkey.

As means for preventing the plunger from retreating, a clip receiving groove is formed in the inner periphery of the opening of the cylinder chamber, and a radially elastically deformable ring portion provided on the register clip is received in the clip receiving groove. A plurality of circumferential grooves which are fastened by the ring portion are provided on the outer circumference of the plunger at intervals in the axial direction, and a tapered surface on the inner circumference of each circumferential groove for expanding the diameter of the ring portion when the plunger advances. And an engagement surface that engages with the ring portion when the plunger retreats and prevents the plunger from retreating. In the chain tensioner provided with the retraction restriction means, by setting the retraction amount of the plunger regulated by the retraction restriction means smaller than the depth of the mounting hole, it is possible to prevent the chain tensioner from slipping out of the mounting hole. Can be prevented.

In a chain tensioner in which the reciprocation of the plunger is restricted by the threaded engagement of the internal thread and the external thread, when the housing rotates together with the plunger when the plunger moves in the axial direction while rotating, the function of the chain tensioner is exhibited. Will be unable to do so. In order to prevent such inconvenience, a detent mechanism is provided between the housing and the mounting hole to detent the housing.

Also, in the case of a chain tensioner provided with a retraction restricting means, the housing may be worn due to contact with the inner periphery of the mounting hole when the housing is moved. To suppress the wear, the outer peripheral surface of the housing is hardened.

As the hardening process, a carbonitriding process or a plating process can be employed.

In the chain tensioner according to the present invention, by providing a retaining means for retaining the housing between the housing and the mounting hole, the chain tensioner can be reliably prevented from falling off.

The retaining means comprises a structure in which a retaining ring is attached so as to straddle an engaging groove formed on the outer periphery of the housing and an engaging groove provided on the inner periphery of the mounting hole. It is possible to adopt a structure in which the elastic force of the spring is made larger than the pressing force by which the hydraulic pressure pushes the housing due to the area difference between the outer surface and the inner surface of the closed end wall of the cylinder chamber. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a longitudinal sectional front view showing a first embodiment of a chain tensioner according to the present invention. FIG. 2 is a cross-sectional view showing, in an enlarged manner, a thread engagement portion between a female screw and a male screw of the chain tensioner shown in FIG. It is. FIG. 3 is a longitudinal sectional front view showing a second embodiment of the chain tensioner according to the present invention. FIG. 4 is a longitudinal sectional front view showing a third embodiment of the chain tensioner according to the present invention. FIG. 5 (I) is a longitudinal sectional front view showing a fourth embodiment of a chain tensioner according to the present invention, and (II) is a right side view of (I). FIG. 6 (I) is a cross-sectional view showing an enlarged part of the backward movement restricting mechanism of FIG. 5 (I), and FIG. 6 (II) is a cross-sectional view showing the operation state of (I). FIG. 7 is a vertical sectional front view showing a fifth embodiment of a chain tensioner according to the present invention. FIG. 8 is a vertical sectional front view showing a sixth embodiment of the chain tensioner according to the present invention. FIG. 9 is a sectional view showing another example of assembling the chain tensioner. FIG. 10 is a partially cutaway front view showing an example of assembling a conventional chain tensioner. FIG. 11 is a partially cutaway front view showing another example of assembling a conventional chain tensioner. Embodiment of the Invention

Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a first embodiment of a chain tensioner A according to the present invention. As shown in the figure, a housing 1 is provided with a bottomed cylinder chamber 2 having a cylindrical surface 3 and an outer diameter which is the same throughout the entire axial direction.

A plunger 4 is incorporated in the cylinder chamber 2. The plunger 4 is provided with a spring storage hole 5 that opens at the rear end face, and a spring 6 incorporated between the closed end of the spring storage hole 5 and the bottom surface of the cylinder chamber 2 presses the plunger 4 outward. ing. An oil supply passage 8 communicating with a pressure chamber 7 formed at the back of the plunger 4 is formed in the closed end wall of the cylinder chamber 2, and the hydraulic oil in the pressure chamber 7 is supplied to the oil outlet side of the oil supply passage 8. A check valve 9 for preventing backflow to the passage 8 side is provided.

Between the housing 1 and the plunger 4, there is provided a backward movement restricting mechanism 10 for preventing the plunger 4 from moving backward more than a predetermined amount toward the bottom surface of the cylinder chamber 2. The retraction control mechanism 10 is composed of a female screw 11 provided on the inner periphery of the opening of the cylinder chamber 2 and a male screw 12 formed on the outer periphery of the plunger 4 and threadedly engaging with the female screw 11. .

As shown in Fig. 2, the threads of the internal thread 11 and the external thread 12 are such that the flank angle of the pressure side flank 14 receiving the axial pushing force applied to the plunger 4 is greater than the flank angle of the play side flank 13 It has a large serrated shape, and a screw clearance 15 is formed between the screw engaging portions of the serrated thread, so that the plunger 4 can retreat within the clearance amount δ of the screw clearance 15. . Further, the lead angle at which the plunger 4 rotates and moves in the axial direction by the elasticity of the spring 6 is formed in the serrated thread.

In forming the female screw 11, a nut member 16 having the female screw 11 on the inner circumference is fitted into a fitting hole 17 formed on the inner circumference of the opening of the cylinder chamber 2. Although the nut member 16 is fixed by caulking the open end of the nut inward, the female screw 11 may be formed directly on the inner periphery of the open end of the cylinder chamber 2. Good.

The chain tensioner 上記 having the above configuration is mounted on the tensioner mounting target Β. The engine cover shown in FIG. 10 is shown here as the tensioner mounting target B. When mounting the chain tensioner A, a mounting hole 20 having a closed end is formed in the tensioner mounting object B, and the housing 1 of the chain tensioner A is fitted into the mounting hole 20. An oil passage 21 communicating with the oil supply passage 8 of the chain tensioner A is formed in the shaft.

Now, hydraulic oil is supplied from the oil passage 21 to the oil supply passage 8, and the plunger 4, which is pressed outward by the elastic force of the spring 6, presses the chain guide 64 shown in FIG. In the adjusted state, the chain 65 vibrates due to a change in angular velocity during one revolution of the crankshaft or torque fluctuation of the camshaft, and if the chain 65 becomes slack, the plunger 4 is disengaged by the elasticity of the spring 6. Move in the direction to absorb the slack in the chain 65. On the other hand, when the chain 65 is tightened, a pushing force is applied to the plunger 4 via the chain guide 64, and the pushing force is buffered by the hydraulic oil in the pressure chamber 7. If the pushing force is stronger than the elasticity of the spring 6, the hydraulic oil in the pressure chamber 7 is formed between the sliding surfaces of the housing 1 and the plunger 4 and between the screw engaging portions of the female screw 11 and the male screw 12. The thread leaks from the female screw clearance 15 to the outside, and the plunger 4 retreats slowly until the elasticity of the spring 6 and the pushing force are balanced.

In the chain tensioner A shown in Fig. 1, the tensioner Since the rear end of the housing 1 is inserted into the mounting hole 20, the tension of the chain tensioner A is lower than that of a conventional chain tensioner in which the housing is fixed by tightening the port. Easy to assemble. In addition, since it is not necessary to form a mounting flange and mounting piece on the housing, it is possible to reduce the weight, and it is not necessary to secure a large space when assembling the chain tensioner A. The degree of freedom can be increased.

Here, the chain tensioner A is an assembly in which the rear end of the housing 1 is simply inserted into the mounting hole 20 formed in the tensioner mounting object B, and furthermore, the chain tensioner A is mounted on the closed end wall of the cylinder chamber 2 in the housing 1. Has an area difference between the outer surface a and the inner surface b, the pressure of the hydraulic oil supplied to the oil passage 21 pushes the housing 1 outward, and conversely, the plunger 4 is pushed into the housing 1. There is a risk.

At this time, the plunger 4 is pushed in within the range of the screw clearance 15 formed between the screw engagement portions of the female screw 11 and the male screw 12 shown in FIG. Stops when pressure side flank 14 at close contact.

Therefore, the plunger 4 is not pushed more than necessary.

Here, the size of the screw clearance 15 is smaller than the depth of the mounting hole 20. For this reason, even if the housing 1 moves outward due to the supply pressure of the hydraulic oil, the amount of movement is within the range of the screw clearance 15, so that the housing 1 does not fall out of the mounting hole 20.

FIG. 3 shows a second embodiment of the chain tensioner A according to the present invention. The chain tensioner A shown in the first embodiment is different from the chain tensioner A shown in the first embodiment in that a valve seat 9 a constituting a check valve 9 for preventing a backflow of hydraulic oil is formed integrally with the housing 1. Is different.

For this reason, the same components as those of the chain tensioner A shown in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

As described above, the manufacturing cost can be further reduced by integrally forming the valve seat 9a with the housing 1.

Here, in order to prevent the valve seat 9a from being worn due to the contact of the check valve 9 with the check ball 9b, the inner peripheral surface of the housing 1 including the valve sheet 9a may be subjected to a hardening treatment. .

FIG. 4 shows a third embodiment of the chain tensioner A according to the present invention. The chain tensioner A shown in this embodiment is located between the housing 1 and the mounting hole 20. This is different from the channel A shown in the first embodiment in that a detent mechanism 30 for detent is provided.

Therefore, the same components as those of the chain tensioner A shown in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 4, the detent mechanism 30 has a detent pin 31 protruding from the outer peripheral portion of the rear end face of the housing 1 and the detent pin 31 is formed at the closed end of the mounting hole 20. The housing 1 is prevented from rotating by inserting it into the pin hole 32.

As described above, the provision of the detent mechanism 30 for preventing the housing 1 from rotating prevents the housing 1 from rotating together with the plunger 4 when the plunger 4 moves in the axial direction while rotating. Thus, the function of the chain tensioner A can be reliably exhibited. Further, by preventing the housing 1 from rotating, rotation of the housing 1 with respect to the mounting hole 20 can be restricted, and wear on the contact surface between the housing 1 and the mounting hole 20 can be suppressed.

5 and 6 show a fourth embodiment of a chain tensioner A according to the present invention. The chain tensioner A shown in this embodiment is different from the chain tensioner A of the first embodiment described above with reference to FIG. 1 in the configuration of a backward movement restricting mechanism 10 that regulates the backward movement of the plunger 4.

For this reason, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. In the backward movement restricting mechanism 10 shown in FIGS. 5 and 6, a clip receiving groove 40 is formed on the inner periphery of the opening of the cylinder chamber 2, and the register clip 41 is provided in the clip receiving groove 40. The plunger 4 accommodates a ring portion 41 a that can be elastically deformed in the radial direction, and a plurality of circumferential grooves 42 tightened by the ring portion 41 a in the outer peripheral portion of the plunger 4. The tapered surface 42a with a smaller diameter toward the tip of the plunger 4 is provided on the inner periphery of each circumferential groove 42 at an interval, and the engagement surface 42b at the small diameter side end of the tapered surface 42a. Are provided.

In the backward movement restricting mechanism 10 having the above-described configuration, the taper surface 42 a allows the plunger 4 to move forward by the action of expanding the diameter of the ring portion 41 a of the register clip 41. As shown in II), the plunger is engaged by the engagement of the engagement surface 42b with the ring portion 41a of the register clip 41, which stops by contacting the rear wall 40a of the clip receiving groove 40. 4 to control the retreat.

In the chain tensioner A shown in the third embodiment and the fourth embodiment, similar to the chain tensioner A shown in the first embodiment, the hydraulic oil supplied to the oil passage 21 is similar to the chain tensioner A shown in the first embodiment. The pressure may cause the housing 1 to move in the direction of coming out of the mounting hole 20. At that time, the outer circumference of the housing 1 is easily worn by contact with the inner circumference of the mounting hole 20.

Therefore, in the chain tensioners shown in the first to fourth embodiments, the outer periphery of the housing 1 is subjected to a hardening treatment to increase the hardness. As the hardening treatment, quenching treatment such as carbonitriding treatment or plating treatment can be adopted. By increasing the hardness of the outer peripheral surface of the housing 1 by performing such a hardening treatment, it is possible to prevent the housing 1 from being worn due to contact with the inner periphery of the mounting hole 20 and to have excellent durability. Housing 1 can be obtained.

FIG. 7 shows a fifth embodiment of a chain tensioner A according to the present invention. The chain tensioner A of this embodiment and the chain tensioner A of the first embodiment shown in FIG. 1 are provided with a retaining mechanism 50 for preventing the housing 1 from coming out of the mounting hole 20. Only differ.

The retaining ring 50 is attached to the retaining mechanism 50 so as to straddle the engaging groove 51 formed on the outer periphery of the housing 1 and the engaging groove 52 provided on the inner periphery of the mounting hole 20. ing.

The above-described retaining mechanism 50 may be provided also in the chain tensioner A shown in FIGS.

As described above, by preventing the housing 1 from being removed by the retaining mechanism 50, the attachment of the chain tensioner A can be stabilized, and the hardening process for the housing 1 can be omitted. The cost can be reduced as compared with the chain tensioner A provided.

Here, the retaining mechanism 50 is not limited to the above configuration. For example, due to the difference in area between the outer surface a and the inner surface b of the closed end wall of the cylinder chamber 1 due to the difference in area between the elastic force of the spring 6 of the chain tensioner A shown in FIGS. Yes, it may be made larger than the pressing force.

FIG. 8 shows a sixth embodiment of the chain tensioner A according to the present invention. The chain tensioner A of this embodiment differs from the chain tensioner A of the fourth embodiment shown in FIG. 5 only in the outer diameter of the eight housing 1, the configuration of the oil supply passage 8, and the configuration of the mounting hole 20. You. Therefore, the same components as those of the chain tensioner A shown in the fourth embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the chain tensioner A shown in the sixth embodiment, the outside of the rear end of the housing 1 The diameter is slightly larger than the outer diameter of the front end, and an annular groove 22 a at the outer periphery of the rear end at a position corresponding to the oil passage 21 formed in the tensioner mounting object B, and the rear end side A ring groove 22b is provided on the bottom surface of the annular groove 22a. An oil supply passage 8 communicating with the pressure chamber 7 is formed on the bottom surface of the annular groove 22a to prevent leakage of hydraulic oil into the ring groove 22b. Is provided.

Also, the mounting hole 20 formed in the tensioner mounting object B is used as a through hole, and a retaining ring 23 is mounted on the inner periphery of the mounting hole 20, and the housing 1 is mounted on the mounting hole 20 with the retaining ring 23. The insertion amount is regulated.

As shown in the sixth embodiment, an oil supply passage 8 is opened on the bottom surface of an annular groove 22 a formed in the outer periphery of the rear end of the housing 1, and the oil passage 21 formed in the tensioner mounting object B is moved from the oil passage 21. By supplying the hydraulic oil to the oil supply passage 8, it is possible to prevent the housing 1 from moving in the direction of coming out of the mounting hole 20 by the supply pressure of the hydraulic oil, and to stabilize the mounting of the housing 1. it can.

In addition, the inner diameter of the mounting hole 20, which is a through hole, is made larger than the maximum diameter of the chain tensioner, so that the chain tensioner can be inserted from the outside of the installation target B (for example, the outside of the engine cover). By doing so, installation can be facilitated.

Instead of using the retaining ring 23 and the O-ring 28 shown in this embodiment, a female screw is formed on the inner peripheral surface of the mounting hole, and a housing screw that is screwed into the female screw is inserted to make the housing 1. In addition to restricting the amount of oil introduced, leakage of hydraulic oil may be prevented.

FIG. 9 shows another example of the attachment of the chain tensioner according to the present invention. In this example, the chain guide 64 that presses the chain 65 shown in FIG. 10 is targeted for mounting the tensioner, and the chain guide 64 is provided with the mounting hole 24, the reservoir chamber 25, and the reservoir chamber 25. And an oil passage 26 for communicating the mounting hole 24 with the mounting hole 24.The housing 1 of the chain tensioner A is inserted into the mounting hole 24, and the tip of the plunger 4 of the chain tensioner A is attached to an engine cover (not shown). The chain guide 64 is pressed against the provided contact portion 60 a in a direction in which the chain is tensioned by the elasticity of the spring 6. The invention's effect

As described above, in the present invention, the mounting of the chain tensioner can be performed by forming the mounting hole in the tensioner mounting object and inserting the housing into the mounting hole. Assembly can be facilitated as compared to a chain tensioner that is fixed. In addition, the mounting Since it is not necessary to form the flange and the mounting piece, the weight can be reduced, the mounting space can be reduced, and the design flexibility can be increased.

Claims

The scope of the claims

1. A slidable plunger and a spring that presses the plunger outward are incorporated into a cylinder chamber formed in the housing, and the housing communicates with a pressure chamber formed on the back of the plunger. In a chain tensioner for buffering a pushing force applied to a plunger by hydraulic oil supplied from the oil supply passage into the pressure chamber, the outer diameter of the housing is substantially the same as the entire diameter in the axial direction. A chain tensioner, which has a cylindrical shape and is assembled by inserting its housing into a mounting hole formed in a tensioner mounting target.

2. The chain tensioner according to claim 1, further comprising a retraction restricting means provided between the housing and the plunger to prevent the plunger from retreating more than a predetermined amount toward the bottom surface of the cylinder chamber.

3. The retraction control means comprises: a female screw provided on the inner circumference of the opening of the cylinder chamber; and a male screw provided on the outer circumference of the plunger and engaged with the female screw. The pressure flank receiving the axial pushing force applied to the plunger has a serrated shape larger than the flank angle of the play flank, and the plunger moves outward due to the spring resilience of the serrated thread. The chain tensioner according to claim 2, which is configured to have a lead angle.

4. The retraction control means forms a clip receiving groove on the inner periphery of the opening of the cylinder chamber, and accommodates a radially elastically deformable ring portion provided on the register clip in the clip receiving groove, A plurality of circumferential grooves fastened by the ring portion are provided on the outer circumference of the plunger at intervals in the axial direction, and a tapered surface on the inner circumference of each circumferential groove for expanding the diameter of the ring portion when the plunger advances. 3. The chain tensioner according to claim 2, further comprising an engagement surface that engages with the ring portion when the plunger retreats and prevents the plunger from retreating.

5. The chain tensioner according to any one of claims 2 to 4, wherein a retreat amount of the plunger until the plunger is brought into a stopped state by the retreating restricting means is smaller than a depth of a mounting hole.

6. The chain tensioner according to any one of claims 3 to 5, further comprising a detent mechanism for preventing the housing from rotating between the housing and the mounting hole.

7. The chain tensioner according to claim 1, wherein a hardening treatment is performed on an outer peripheral surface of the housing.

8. The chain tensioner according to any one of claims 1 to 6, further comprising a retaining means for preventing the housing from falling out of the mounting hole.

9. The retaining ring is mounted so that the retaining means straddles an engaging groove formed on the outer periphery of the housing and an engaging groove provided on the inner periphery of the mounting hole. The chain tensioner described in 8

10. The retaining means has a structure in which the elastic force of the spring is greater than the pressing force by which the hydraulic pressure pushes the housing due to the area difference between the outer surface and the inner surface of the closed end wall of the cylinder chamber. The chain tensioner according to claim 8.