JPH11210846A - Belt tensioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To refine the sliding surface of a cylinder case or a piston of a hydraulic damper in a belt tensioner while a change in dimensions is suppressed so that the coefficient of friction can be reduced, and thereby smooth the sliding surface and improve resistance to seizure and wear resistance. SOLUTION: In a state where the surface oxide is removed, a nitride layer 9 or a nitrosulfurizing layer is formed at least on one sliding surface of a cylinder case and a piston 41 provided in a hydraulic damper 4 of a belt tensioner, and thus the sliding surface is adapted to be refined to a dense, smooth, and hard surface property while thermal strain of a base materia in the process of forming the nitride layer is suppressed. Thus, the coefficient of friction of the sliding surface can be reduced, and thereby the surface polishing process required formerly can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a belt tensioner for adjusting the tension of a belt, such as a timing belt and an auxiliary device driving belt provided in an automobile engine.
Specifically, the configuration is such that the rotatable tension pulley can swing about a position eccentric from the rotation center as a fulcrum,
The present invention relates to a belt tensioner having a function of swinging a tension pulley so as to keep a belt tension constant and a function of attenuating vibration and impact transmitted from the belt.

[0002]

2. Description of the Related Art As a conventional belt tensioner of this type, the present applicant has proposed Japanese Patent Application No. 8-290041. The belt tensioner includes tension adjusting means for swinging a tension pulley so as to keep the belt tension constant, and a hydraulic damper for attenuating vibration and impact transmitted from the belt.

In the above-described hydraulic damper, when the cylinder case and the piston are relatively inclined, the sliding resistance is increased, and the piston is difficult to move smoothly, and is easily seized and easily worn.

[0004] For this reason, in order to smooth the sliding operation, and to improve the seizure resistance and wear resistance, the cylinder case and the piston are conventionally formed of stainless steel or the like. Then, their surfaces are subjected to induction hardening.

[0005]

In the above-described conventional belt tensioner, the induction hardening process is performed on the cylinder case and the piston of the hydraulic damper. It is pointed out that the change is likely to be large, which leads to an increase in manufacturing cost, such as a need to perform a polishing treatment after the treatment.

Accordingly, the present invention provides a belt tensioner in which a sliding surface of a cylinder case or a piston of a hydraulic damper is modified so that a coefficient of friction can be reduced while suppressing a dimensional change, thereby facilitating a sliding operation. It is intended to improve seizure resistance and wear resistance.

[0007]

According to a first aspect of the present invention, there is provided a belt tensioner in which a rotatable tension pulley is swingable about a position eccentric from a center of rotation of the tension pulley. Tension adjusting means for swinging the tension pulley so as to keep it constant, and a hydraulic damper for attenuating vibration and impact transmitted from the belt, the hydraulic damper includes a cylinder case and a piston,
At least one of the sliding surfaces of the cylinder case and the piston is provided with a nitrided layer or a oxynitrided layer with its surface oxide removed.

[0008] The belt tensioner according to claim 2 of the present invention,
The nitrided layer according to claim 1 is configured to include a nitride-containing hard nitride compound layer formed on the surface side of the sliding surface, and a diffusion layer in which nitrogen is diffused further below. I have.

A belt tensioner according to a third aspect of the present invention includes:
The sulfur-nitrided layer according to claim 1 is obtained by forming a sulfur-containing sulfur layer formed on the surface side of the sliding surface, a nitride compound layer formed therebelow, and nitrogen being further diffused thereunder. And a diffusion layer composed of

[0010] As described above, in the present invention, the nitride layer formed on the sliding surface of the cylinder case or the piston is formed in a state where oxides inevitably present on the surface of the base material have been removed. The forming process requires a lower temperature and a shorter time than the above-mentioned conventional curing process, and is dense, smooth and hard. In other words, since the formation process of the nitride layer can be performed at a lower temperature and in a shorter time as compared with the above-described conventional hardening process, the heat distortion of the base material hardly occurs in the process, and post-processing such as polishing conventionally required. Becomes unnecessary. Further, since the nitrided layer is formed dense, smooth and hard, the friction coefficient of the sliding surface can be made lower than in the above-mentioned conventional example.

In the present invention, the oxynitrided layer formed on the sliding surface of the cylinder case or the piston is obtained by gas oxynitriding, and the processing gas is inevitable on the surface of the metal base material. It has the function of removing oxides that are present temporarily, so that its forming process can be performed at a lower temperature and in a shorter time than the above-mentioned conventional hardening process, and it is dense, smooth, hard and lubricious. It has excellent sulfur content. That is, as in the case of the nitride layer, thermal distortion of the base material hardly occurs during the processing, and post-processing such as polishing, which has been conventionally required, becomes unnecessary. In addition, when the nitrosulphurized layer is formed, the friction coefficient of the sliding surface becomes even lower than that when the above-mentioned nitrided layer is formed.

If such a nitrided layer or a nitrosulphurized layer is formed, the sliding operation of the piston becomes smooth, which is advantageous in seizure resistance, wear resistance and the like. In addition, heat generation on the sliding surface between the cylinder case and the piston can be suppressed, and the temperature rise of the hydraulic oil inside the hydraulic damper can be suppressed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in FIGS.

FIGS. 1 to 7 relate to an embodiment of the present invention. FIG. 1 is a diagram schematically showing a use state of a belt tensioner, and FIG. 2 is a perspective view of the belt tensioner as viewed from the back. 3 is a plan view of a partial cross section of the belt tensioner as viewed from the back, and FIG. 4 is (4)-of FIG.
(4) Arrow view of the cross section of the line, FIG. 5 is (5)-(5) of FIG.
FIG. 6 is an enlarged view of a main part of FIG. 3, and FIG.
FIG. 7 is a schematic cross-sectional view of the nitride layer of FIG. 6.

In FIG. 1, reference numeral 80 denotes a belt, 81 denotes a pulley of a crankshaft, 82 denotes an idler pulley, 83 denotes an auxiliary pulley, and A denotes a belt tensioner.

The belt tensioner A is attached to a mounting object 85 such as a block of an automobile engine in order to apply a required tension to the belt 80. The belt tensioner A prevents the belt 80 from fluctuating in tension due to environmental temperature change and torque fluctuation. And a function of attenuating vibrations and shocks transmitted from the belt 80.

As shown in FIGS. 2 to 4, the belt tensioner A mainly includes a rotatable tension pulley 1 for applying tension to a belt 80 and a tension pulley 1 for an attachment target 85 as a base. A swing fulcrum shaft 2 that swingably supports a position eccentric from the rotation center, a tension adjusting unit 3 that swings the tension pulley 1 so as to keep the tension of the belt 80 constant, and a signal transmitted from the belt 80. Hydraulic damper 4 for damping vibration and shock
And a tension adjusting means 3 fixed to the pivot 2
And a single case 5 in which the hydraulic damper 4 is distributed and housed so as to be adjacent on the same plane.

The tension pulley 1 is formed integrally with a ball bearing, and includes an inner race 11, a wide outer race 12 serving as a pulley around which a belt 80 is wound, and inner and outer races 11, 1.
A plurality of balls 13 interposed between the two, a crown-shaped retainer 14 holding the balls 13, seals 15, 15 provided on both axial sides between the inner and outer rings 11, 12, and an inner periphery of the inner ring 11 And a boss 16 which is press-fitted into the boss. The boss 16 is provided with a through hole 17 at a position eccentric from the center thereof, and a pin 18 is implanted at a position spaced from the through hole 17 by a required distance L1. The pin-shaped convex portion 19 is protruded at the bent position.

The swing fulcrum shaft 2 is made of a bolt or the like which is inserted into the through hole 17 of the boss 16 via the collars 6 and 7 and is screwed to the mounting object 85. A case 5 containing the tension adjusting means 3 and the hydraulic damper 4 is fixedly attached to the free end side of the swing fulcrum shaft 2.

The case 5 has adjacent elongated holes 51, 5 adjacent to each other.
2 and a cylindrical mounting portion 53 on the opening side of the elongated holes 51 and 52.

The tension adjusting means 3 comprises a cylindrical coil spring 31 and a spring seat 32. The coil spring 31 is housed in a compressed state in one elongated hole 51 in the case 5, and the elastic restoring force of the coil spring 31 is applied to the pin-shaped convex portion 19 of the boss 16 located on the opening side of the elongated hole 51. To the tension pulley 1
Is resiliently urged around the swing fulcrum shaft 2 in one rotation direction. The spring force of this coil spring 31 is
As shown in FIGS. 1A and 1B, it is set appropriately according to the layout of the belt 80 and the like.

The hydraulic damper 4 is connected to the other slot 5 of the case 5.
A piston 41 having a push rod housed therein and forming two liquid chambers 46 and 47; a check valve 42 disposed on the piston 41 for controlling movement of hydraulic oil between the liquid chambers 46 and 47; A cylindrical coil spring 43 for urging the upper portion 41 upward; a seal ring 44 for preventing leakage of hydraulic oil in the liquid chambers 46 and 47;
And a closing ring 45 for closing the opening of the other long hole 52. Push rod 48 of piston 41
Is abutted against the pin 18 of the boss 16 located on the opening side of the elongated hole 52 so as to attenuate the vibration and impact transmitted from the belt 80 to the tension pulley 1.

Next, the operation of the belt tensioner A will be described. First, as the environmental temperature rises,
Expands, the tension of the belt 80 tends to increase.
Check valve 4 of hydraulic damper 4 while 1 is contracting
2 is closed, and while the oil gradually moves from the liquid chamber 47 to the liquid chamber 46 through a small gap between the piston 41 and the case 5, the tension pulley 1 rotates so as to retreat in the arrow Y direction in FIG. Then, the tension pulley 1 stops at a position where the excessive tension of the belt 80 is reduced and the tension of the belt 80 and the spring force of the coil spring 31 are balanced. In this way, the tension of the belt 80 is kept constant.

On the other hand, when the mounting object 85 contracts due to a decrease in the environmental temperature, the tension of the belt 80 tends to decrease. As a result, the coil spring 31 of the tension adjusting means 3 is extended and the hydraulic damper is expanded. When the check valve 42 is opened, the oil is moved from the liquid chamber 46 to the liquid chamber 47.
And the tension pulley 1 is rotated so as to advance in the direction of arrow X in FIG. 3, and the tension of the belt 80 and the coil spring 31 are adjusted so that the under tension of the belt 80 is maintained at an appropriate tension.
The tension pulley 1 stops at a position where the spring force is balanced. In this way, the tension of the belt 80 is kept constant.

Here, in any of the above states, the case 5 does not move and only the tension pulley 1 swings. When vibration / impact is applied to the tension pulley 1 from the belt 80, movement of the hydraulic oil in the liquid chambers 46 and 47 is prevented by the check valve 42 of the hydraulic damper 4. Damping suppresses instantaneous fluctuations in the tension of the belt 80 and prevents slippage of the belt 80.

Here, the features of the present invention will be described.
That is, as shown in FIG. 6, the sliding surfaces of the piston 41 of the hydraulic damper 4 and the other long hole 52 of the case 5
The nitride layer 9 is formed with the surface oxide removed. A method for forming the nitride layer 9 will be described.

That is, as a target product on which the nitrided layer 9 is to be formed, the case 5 and the piston 4 whose outer shapes are made of stainless steel such as JIS SUS440C are used.
Prepare 1 The target product is set in a chamber having an airtight structure, and two kinds of a fluorine gas and a nitriding gas are separately supplied in a vacuum with a time lag. NF ₃ , BF ₃ , CF ₄ , HF, SF ₆ , F ₂
And a mixture of a fluorine source component consisting of a single or a mixture of the above with an inert gas such as N _2.
A mixture of nitrogen fluoride (NF ₃ ) and nitrogen is preferably used. Incidentally, from the viewpoint of the effect, 0.05% to 20% of fluorine source components such as NF ₃ (by weight, hereinafter the same), it is preferably set in concentration in the range of 3% to 5%. As the nitriding gas, for example, a gas composed of NH ₃ alone or N 2
A mixed gas composed of H ₃ and a carbon source (for example, an RX gas) may be used.

Here, first, a fluoride gas is supplied into the chamber, and the temperature is set to 300 ° C. to 400 ° C., for example, 320 ° C., and is maintained for 10 minutes to 120 minutes, for example, 120 minutes. Thus, the oxides and the like on the surface of the target product are removed and purified, and at the same time, are replaced with the metal fluoride film.

Next, a nitriding gas is supplied into the chamber,
400 ° C. to 700 ° C., for example, 550 ° C., and 0.5
Hold for a period of time to 5 hours, for example, 120 minutes. Thus, a nitride layer 9 is formed. At this time, the metal fluoride film on the surface of the target product becomes the activation film, and the nitrogen easily penetrates and diffuses deeply into the metal during the nitriding treatment.

Thereafter, cooling is performed by oil cooling or air cooling over a required time. Since the target product is kept in the nitrogen gas until cooling is completed, no oxide is generated on the surface.

The nitride layer 9 formed as described above has the structure shown in FIG.
As shown in the figure, CrN, Fe ₂ N, Fe ₃ N, and Fe ₄ move inward from the surface of the metal base material 90 (41, 52).
An ultra-hard compound layer 91 containing a nitride such as N is provided, followed by a diffusion layer 92 of N atoms inside. The depth of the nitride layer 9 can be controlled by appropriately setting the processing temperature and the holding time.

The surface roughness of the nitride layer 9 is determined by the surface roughness of the target product before it is formed (center line average roughness Ra = 0.7).
μm to 1.0 μm, ten-point average roughness Rz = 4.0 μm
7.0 μm, maximum height Rmax = 4.5 μm to 7.5 μ
m) is kept almost the same. As described above, it is possible to suppress a dimensional change due to thermal strain during the process of forming the nitride layer 9.

The hardness on the surface side of the nitrided layer 9 is 800 to 1000 (Vickers hardness [Hv]) (test load 50 g).
f), which is equivalent to or higher than the conventional cured product. The friction coefficients of the above-described nitrided layer 9 and the hardened layer obtained by the conventional hardening process are 0.24 and 0.54, respectively, in a non-lubricated state. And become excellent. This coefficient of friction is determined by using a HRIDON abrasion tester on a test piece (SPCC material having a nitrided layer 9 formed on the surface) and a ball (SUJ2 material).
Load 200gf, speed 100mm / sec, distance 20mm
10 reciprocations, and the dynamic friction coefficient at that time is measured, and the maximum value of the measured values is determined. Thus, the nitride layer 9
Since it is formed densely and smoothly, and is formed as hard as or more than the case by the conventional curing treatment,
The coefficient of friction on the sliding surface of the target product can be reduced, and the sliding operation of the piston 41 becomes smooth, which is advantageous in seizure resistance, wear resistance, and the like. In addition, since the heat generation on the sliding surface between the other long hole 52 of the case 5 and the piston 41 can be suppressed and the temperature rise of the hydraulic oil inside the hydraulic damper 4 can be suppressed, air bubbles are generated in the hydraulic oil. It is possible to prevent the occurrence of undesired phenomena such as occurrence of pressure drop.

It should be noted that the present invention is not limited to only the above-described embodiment, and various applications and modifications are conceivable.

(1) Instead of the nitride layer 9 described in the above embodiment, a nitrosulphurized layer can be used. A method for forming this oxynitrided layer will be described. First, JIS standard S
A single unit of the target product whose outer shape is made of stainless steel such as US440C is prepared. The target product is set in a chamber having an airtight structure, and a required reaction gas is supplied in a vacuum state. As the reaction gas, a mixture of a carburizing gas, a nitriding gas, and a sulfurizing gas, that is, CO ₂ + (NH ₃ + N ₂ ) + H ₂ S is used. Here, the inside of the chamber is maintained at 400 ° C. to 700 ° C., for example, 550 ° C., and is maintained for 0.5 hour to 5 hours, for example, for 120 minutes. Thereafter, cooling is performed by oil cooling or air cooling over a required time. As a result, first, the reaction gas, particularly H ₂ S, removes impurity factors such as oxides inevitably present on the surface of the target product, and the N ₂ is removed while exposing the pure surface of the metal base material. Quickly and deeply penetrates and diffuses into the metal base material to form the oxynitrided layer 10 as shown in FIG. As shown in FIG. 8, the oxynitrided layer 10
In order from the surface side of (41, 52) to the inside, FeS
Soft sulfur layer 101 containing Fe as the main component, Fe _2-3 N
Hard and dense nitrided compound layer 10 mainly composed of
2. It has a hierarchical structure including an ultra-hard nitrided diffusion layer 103 in which N atoms are diffused into the metal base material 90 (41, 52).

In the process of forming the oxynitrided layer 10 here,
Since the processing temperature is lower than that of the conventional thermosetting treatment and the processing time is shorter than that of the conventional curing treatment due to the action of removing the surface oxide, similar to the case of forming the nitride layer 9,
The occurrence of thermal distortion of the metal base material is suppressed, and the surface polishing treatment after this treatment can be omitted. And, similarly to the nitrided layer 9, the nitrosulphurized layer 10 is formed densely and smoothly, is formed not only harder than or equal to the case of the conventional hardening treatment, and also has a sulfur component. Since the sulfur layer 101 having excellent lubricity is included, the coefficient of friction on the sliding surface of the target product can be further reduced as compared with the case of the nitride layer 9 described above.

(2) In the above embodiment, the piston 41
Although the nitriding layer or the oxynitriding layer is formed on both the case 5 and the cylinder 5, it may be formed on only one of the piston 41 and the case 5. Also, piston 4
These layers may be formed only on the sliding surface of the case 1 and the case 5, or may be formed on the entire surface of the piston 41 and the case 5. In the latter case, the strength of the piston 41 and the case 5 itself can be improved by the formed nitrided layer or oxynitrided layer.

(3) The belt tensioner A of the above embodiment has a configuration in which the tension pulley 1 is integrated with a ball bearing, but the present invention is also applied to a configuration in which the tension pulley 1 is separated from a rolling bearing. it can.

(4) The belt tensioner A of the above embodiment has a configuration in which the tension adjusting means 3 and the hydraulic damper 4 are housed in a single case 5, but the present invention is also applicable to a configuration in which these are separately provided. Can be applied.

(5) The belt tensioner A of the above-described embodiment has a configuration in which a cylindrical coil spring is used for the tension adjusting means 3, but this is replaced with an elastic biasing member such as a disc spring. The present invention can also be applied.

[0041]

According to the belt tensioner of the present invention, the nitriding layer or the oxynitriding layer is formed on the sliding surface of the cylinder case or the piston with the surface oxide removed. The surface is modified into a dense, smooth, and hard surface while suppressing the thermal distortion of the base material.

Therefore, the coefficient of friction of the sliding surface of the cylinder case and the piston becomes lower than or equal to that of the conventional hardening treatment, so that the sliding operation of the piston becomes smooth and the seizure resistance, abrasion resistance and the like are improved. It will be advantageous. Further, since the heat generated on the sliding surface between the cylinder case and the piston can be suppressed to suppress the temperature rise of the hydraulic oil inside the hydraulic damper, bubbles are generated in the hydraulic oil to cause pressure loss. The occurrence of the phenomenon can be prevented, and the reliability can be improved.

Further, after the formation of the nitrided layer and the sulfur-nitrided layer, the post-treatment such as polishing conventionally required can be omitted, so that the manufacturing cost can be reduced.

As described above, according to the present invention, it is possible to provide a belt tensioner equipped with an excellent hydraulic damper which is inexpensive but has high functionality and reliability.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a use state of a belt tensioner according to an embodiment of the present invention.

FIG. 2 is a perspective view of the belt tensioner of FIG. 1 as viewed from the back.

FIG. 3 is a plan view of a partial cross section of the belt tensioner of FIG. 1 when viewed from the back.

4 is a sectional view taken along line (4)-(4) of FIG.

FIG. 5 is a sectional view taken along line (5)-(5) of FIG.

FIG. 6 is an enlarged view of a main part of FIG. 3;

FIG. 7 is a schematic cross-sectional view of the nitride layer of FIG.

FIG. 8 is a cross-sectional photograph and a schematic cross-sectional view of a oxynitrided layer according to another embodiment of the present invention.

[Explanation of symbols]

Reference Signs List A belt tensioner 1 tension pulley 16 boss of tension pulley 17 boss through-hole 18 boss pin 19 boss pin-shaped protrusion 2 swing fulcrum shaft 3 tension adjusting means 31 coil spring of tension adjusting means 4 hydraulic damper 41 piston 42 check Valve 46, 47 Liquid chamber 5 Case 51 One long hole of case (case of tension adjusting means) 52 The other long hole of case (cylinder case of hydraulic damper) 80 Belt 85 Attachment object 9 Nitride layer

Claims (3)

[Claims] 1. A belt tensioner having a structure in which a rotatable tension pulley can swing about a position eccentric from its rotation center as a fulcrum, wherein the tension pulley swings to maintain a constant belt tension. Tension adjusting means, and a hydraulic damper for attenuating vibration and impact transmitted from the belt, wherein the hydraulic damper includes a cylinder case and a piston, and at least one of the sliding surfaces of the cylinder case and the piston has a surface thereof. A belt tensioner, wherein a nitrided layer or a sulfided nitrided layer is formed in a state where an oxide is removed. 2. The belt tensioner according to claim 1, wherein the nitride layer includes a hard nitride compound layer containing a nitride formed on the surface side of a sliding surface, and a nitrogen layer below the hard nitride compound layer. A belt tensioner comprising: a diffusion layer formed by diffusion. 3. The belt tensioner according to claim 1, wherein the sulfur-nitrided layer includes a sulfur-containing sulfur layer formed on the surface side of the sliding surface and a nitride compound layer formed below the sulfur-containing layer. And a diffusion layer in which nitrogen is diffused further below the belt tensioner.