This invention relates to a chain tensioner for keeping constant the tension of a chain of a chain transmission device, particularly a chain transmission device for driving a camshaft.
As such a chain tensioner, there is known one in which a plunger and a spring for biasing the plunger outwardly are mounted in a cylinder chamber formed in a housing, and an oil supply passage is formed in the housing to communicate with a pressure chamber formed in the back of the plunger, thereby damping the push-in force imparted to the plunger by hydraulic oil supplied to the pressure chamber through the oil supply passage.
Among chain tensioners having such a structure, there are an exterior type and an interior type (U.S. Pat. No. 5,658,212 and JP Patent No. 3243226).
In a chain tensioner of the former type, as shown in
On the other hand, in a chain tensioner of the latter type, as shown in
In both types of chain tensioners, a camshaft-driving chain 65 is tensioned by biasing a chain guide 64 pivotable about a shaft 63 by means of a plunger 76.
In both types of chain tensioners, since it is fixed to the engine cover 60 or engine block 66 by tightening the bolts 75, it is necessary to provide the flange 72 or the mounting pieces 74 on the housing 71 or 73. Thus, the shape of the outer periphery of the housing 71 or 73 becomes complicated. This makes it impossible to employ pressing for mass-production of the housings 71, 73. Thus, the method is limited to diecasting or forging, so that the manufacturing cost increases. An object of this invention is to lower the cost of a chain tensioner.
According to this invention, there is provided a chain tensioner comprising a housing formed with a cylinder chamber, a plunger slidably mounted in the cylinder chamber, a spring mounted in the cylinder chamber for biasing the plunger outwardly, the housing having an oil supply passage communicating with a pressure chamber formed at the back of the plunger, whereby damping a push-in force imparted to the plunger by hydraulic oil supplied to the pressure chamber through the oil supply passage, characterized in that the housing is cylindrical and has an outer diameter substantially uniform over the entire axial length thereof, and the housing is mounted by inserting it in a mounting hole formed in a member to which the chain tensioner is to be mounted.
By making the outer diameter of the housing substantially uniform over its entire axial length, such housings can be mass-produced by pressing. This reduces the cost of the housing. By forming a valve seat of the check valve for preventing reverse flow of hydraulic oil, integrally with the housing by pressing, it is possible to further reduce the cost.
In press-forming the housing, a blank is formed by punching a metal plate and the blank is deep-drawn. If the thickness of the blank is less than 1.7 mm, the strength of the housing would be insufficient. If it exceeds 2.5 mm, deep drawing would be difficult and the number of steps of drawing increase. This increases the manufacturing cost. Thus, the thickness of the blank is preferably 1.7-2.5 mm.
If the surface roughness Ra of the inner periphery of a cylinder chamber of the housing formed by pressing exceeds 3.2 μm, it tends to be worn due to contact with the plunger. Thus, the surface roughness Ra of the inner periphery is preferably not more than 3.2 μm.
In the chain tensioner according to this invention, by providing a check valve having a valve seat and a check ball provided so as to come into and out of contact with the valve seat and adapted to close the oil supply passage at the oil outlet of the oil supply passage, when push-in force is imparted to the plunger, the check valve will close the oil supply passage, thereby preventing hydraulic oil in the pressure chamber from flowing toward the oil supply passage. Thus the push-in force is damped by the hydraulic fluid in the pressure chamber. Thus, it is possible to provide a chain tensioner that is superior in the damper effect.
By integrally forming the valve seat with the housing, no seat member is necessary, so that it is possible to further reduce the manufacturing cost of a chain tensioner with a check valve, and to achieve compactness of the chain tensioner.
If the oil supply passage is a through hole axially extending through the end wall of the housing, an oil passage communicating with the oil supply passage is provided at the closed end of the mounting hole. In this case, under pressure of hydraulic oil supplied to the oil passage and due to a difference in area between the outer surface and the inner surface of the end wall of the cylinder chamber, the housing may move in such a direction as to come out of the mounting hole and conversely the plunger may be pushed too much toward the bottom of the cylinder chamber. If the moving amount of the housing, i.e. the push-in amount of the plunger is large, the housing may fall out of the mounting hole.
In order to prevent such trouble, according to this invention, a retraction restricting means is provided to prevent the plunger form being pushed in over a predetermined amount.
The retraction restricting means may comprise a clip-receiving groove in the inner periphery of the cylinder chamber near its opening, a register clip having a diametrically deformable ring portion received in the clip-receiving groove, the plunger being formed with a plurality of circumferential grooves in the outer periphery thereof at axial intervals, the each circumferential groove having a tapered surface which expands the ring portion when the plunger is advancing and an engaging surface which engages the ring portion to prevent retraction of the plunger.
Also, as the means for restricting the retraction of the plunger, one may be employed in which female threads formed on the inner periphery of the cylinder chamber at its opening end, and male threads formed on the outer periphery of the plunger and in threaded engagement with the female threads, the female threads and male threads having is serration-shaped such that pressure flanks thereof, which receive axial push-in force imparted to the plunger, have a greater flank angle than clearance flanks thereof, the serration-shaped threads having such a lead angle that the plunger moves outwardly under the elastic force of the spring.
In the chain tensioner provided with such a retraction restricting means, by making the retracting amount of the plunger restricted by the retraction restricting means smaller than the depth of the mounting hole, it is possible to prevent the chain tensioner from coming out of the mounting hole.
With a chain tensioner in which retraction of the plunger is restricted by the thread engagement of female threads with male threads, when the plunger axially moves while rotating, if the housing turns together with the plunger, the chain tensioner cannot exhibit its function. In order to prevent such trouble, a turn-preventive mechanism for preventing the housing from turning in the mounting hole may be provided.
Also, in the chain tensioner provided with a retraction restricting means, during movement of the housing, the housing is subject to wear due to contact with the inner periphery of the mounting hole. The inner periphery of the housing, too, is subject to wear due to the sliding of the plunger. In order to suppress such wear, the outer peripheral surface of the housing may be subjected to hardening.
For hardening, carburizing/nitriding or plating can be employed.
Hereinbelow, the embodiments of this invention will be described with reference to
In pressing the housing 1, a blank is formed by blanking a metallic plate, and the blank is deep-drawn. The thickness of the blank is preferably about 1.7-2.5 mm. If it is less than 1.7 mm, it is impossible to obtain a housing 1 which is high in strength. If it exceeds 2.5 mm, steps of deep-drawing will increase, thus increasing the manufacturing cost. The housing 1 after pressing has the inner periphery of the cylinder chamber 2 ground to finish the surface roughness Ra of the inner diameter surface to 3.2 micrometers or under.
In the cylinder chamber 2, a plunger 4 is mounted. A spring-receiving hole 5 opening at the rear end is formed in the plunger 4. A spring 6 mounted between the closed end of the spring-receiving hole 5 and the bottom face of the cylinder chamber 2 biases the plunger 4 outwardly.
An oil supply passage 8 communicating with a pressure chamber 7 formed in the back of the plunger 4 is formed in the end wall of the cylinder chamber 2. At the oil outlet of the oil supply passage 8, a check valve 9 is provided to prevent reverse flow of hydraulic oil in the pressure chamber 7 toward the oil supply passage 8.
The check valve 9 comprises a seat member 9a mounted on the closed end wall of the cylinder chamber 2, a check ball 9d movable into and out of contact with a valve seat 9c of valve hole 9b formed in the seat member 9a for closing the valve hole 9b when brought into contact, and a retainer 9e for restricting the degree of opening of the check ball 9d.
Between the housing 1 and the plunger 4, there is provided a retracting movement restricting mechanism 10 for preventing the plunger 4 from retracting over a predetermined amount toward the bottom face of the cylinder chamber 2.
As shown in
In the retraction restricting mechanism 10 having such a structure, due to the action of the tapered surfaces 13a increasing the diameter of the ring portion 12a, the plunger 4 is allowed to advance, and retraction of the plunger 4 is restricted by the engagement of the engaging surface 13b with the ring portion 12a of the register clip 12, which stops by abutting a rear end wall 11a of the clip-receiving groove 11.
In the chain tensioner shown in the first embodiment, as the register clip 12, a register clip was shown in which a pair of knobs 12b (see
In a tension adjusting state in which hydraulic oil is supplied through the oil passage 21 into the oil supply passage 8 and the plunger 4 biased outwardly by the spring 6 biases the chain guide 64 shown in
At this time, the tapered surfaces 13a expand the diameter of the ring portion 12a of the register clip 12, thereby allowing advancement of the plunger 4 (see
On the other hand, when the chain 65 is stretched, push-in force is imparted to the plunger 4 through the chain guide 64. The push-in force is damped by the hydraulic oil in the pressure chamber 7. If the push-in force is larger than the resilience of the spring 6, as shown in
In the chain tensioner A shown in
Also, since the chain tensioner A is mounted by inserting the rear end of the housing 1 in the mounting hole formed in the object B, compared with conventional chain tensioners in which the housing is fixed by tightening bolts, mounting of the chain tensioner A is easier. Further, there is no need to provide a large space to mount the chain tensioner A, so it is possible to increase the freedom of design.
The chain tensioner A as shown in
At this time, as shown in
Thus, to the same parts as in the chain tensioner A of the first embodiment, the same numerals are attached and their description is omitted.
As described above, by forming the valve seat 9c integral with the housing 1, it is possible to omit the seat member 9a shown in
Here, in order to prevent wear of the valve seat 9c due to contact with the check ball 9d of the check valve 9, hardening treatment may be provided on the inner peripheral surface of the housing 1 including the valve seat 9c.
Thus, to the same parts as those in the first embodiment, the same numerals are attached and their description is omitted.
In the retraction restricting mechanism 10 shown in
In forming the female threads 31, here, a nut member 36 having female threads 31 on the inner periphery thereof is received in a recess 37 formed in the inner periphery of the opening of the cylinder chamber 2, and the opening end of the housing 1 is caulked inwardly to fix the nut member 36. But the female threads 31 may be formed directly on the inner periphery of the opening end of the cylinder chamber 2.
In the retraction restricting mechanism 10 having such a structure, retraction of the plunger 4 is allowed in the amount δ of the thread gaps 35 formed between the female threads 31 and the male threads 32, and the retraction of the plunger 4 is restricted by the abutment of the pressure flanks 33 of the female threads 31 and male threads 32 so that the plunger 4 will not be pushed in any further.
In the chain tensioner shown in
Here, in the chain tensioner A shown in
Here, in the mounting example shown in
As described above, by providing the turn-preventive mechanism 40 for preventing the housing 1 from turning, when the plunger 4 moves axially while turning, it is possible to prevent the housing 1 from turning together with the plunger 4, so that the chain tensioner A exhibits its functions reliably. Also, by preventing the housing 1 from turning, it is possible to suppress wear on the contact surfaces of the housing 1 and the mounting hole 20.
As shown in
Therefore, in the chain tensioners of the first to third embodiments, the outer periphery of the housing 1 and the inner wall of the cylinder chamber 2 are subjected to hardening to increase hardness to about Hv 400-700. For hardening, treatment such as carburizing/nitriding or plating may be employed. By increasing the hardness of the outer peripheral surface of the housing 1 by such hardening treatment, it is possible to prevent the housing from getting worn by contact with the inner periphery of the mounting hole 20. Thus it is possible to provide a housing 1 that is superior in durability.
The fall-preventive mechanism 50 has a snap ring 53 mounted in a groove 51 formed in the outer periphery of the housing 1 and a groove 52 formed in the inner periphery of the mounting hole 20.
As described above, by preventing the housing 1 from coming out by the fall-preventive mechanism 50, it is possible to stabilize the mounting of the chain tensioner A, and to omit hardening applied to the housing. Thus, compared with chain tensioners A which are subjected to hardening, it is possible to reduce the cost.
In order to mount the chain tensioner A having this structure to e.g. a tensioner mounting object B comprising an engine cover, a mounting hole 20 comprising a through hole is formed in the tensioner mounting object B, the chain tensioner A is inserted in the mounting hole 20 to press the O-ring 47 against the inner peripheral surface of the mounting hole 20, the amount of insertion of the chain tensioner A is restricted by a snap ring 23 mounted on the inner periphery of the mounting hole 20, and an oil passage 21 communicating with the annular groove 45 is formed in the tensioner mounting object B.
In
Also, since the outer diameter of the housing is substantially uniform over the entire axial length, the housing 1 can be formed by pressing.
Further, by making the inner diameter of the mounting hole 20, which is a through hole, greater than the maximum diameter of the chain tensioner so that the latter can be inserted from the outer side of the object B (e.g. from the outer side of an engine cover), it is possible to make the mounting easy.
The chain tensioner mounting object B is formed with a mounting hole 24, a reservoir chamber 25 and an oil passage 26 through which the reservoir chamber 25 and the mounting hole 24 communicate. The housing 1 of the chain tensioner A is inserted in the mounting hole 24, and the tip of the plunger 4 of the chain tensioner A is brought into abutment with an abutment 60a provided on an engine cover (not shown) to bias the chain guide 64 in such a direction that the chain is stretched by the resilience of the spring 6.
As shown in
While it is necessary to change the size of the holder B according to the kind of engine, since its shape is simple and no precision is required, it can be manufactured at a low cost by forging such as die casting.
The retraction restricting mechanism is not limited to the ones of the embodiments, but may be of the ratchet type or any other type.
As described above, according to this invention, since the outer diameter of the housing, in which is received the plunger and the spring, is substantially constant over the entire axial length, such housings can be mass-produced by pressing. Thus, it is possible to lower the cost of the chain tensioner.
Number | Date | Country | Kind |
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2001-337332 | Nov 2001 | JP | national |
2002-311035 | Oct 2002 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/JP02/11480 | 11/1/2002 | WO | 00 | 4/29/2004 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO03/038306 | 5/8/2003 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
3812733 | Yoshida | May 1974 | A |
4070895 | Yamada et al. | Jan 1978 | A |
4366995 | Kocian | Jan 1983 | A |
4466802 | Ojima et al. | Aug 1984 | A |
4472162 | Hitchcock | Sep 1984 | A |
4539001 | Okabe | Sep 1985 | A |
4632269 | Rose | Dec 1986 | A |
4950207 | Henderson | Aug 1990 | A |
5213126 | Ono et al. | May 1993 | A |
5266067 | Gapco | Nov 1993 | A |
5310385 | Suzuki | May 1994 | A |
5480358 | Sakai et al. | Jan 1996 | A |
5547429 | Hirabayashi et al. | Aug 1996 | A |
5571061 | Tsai et al. | Nov 1996 | A |
5632474 | Hayakawa et al. | May 1997 | A |
5632698 | Suzuki | May 1997 | A |
5649878 | Noguchi et al. | Jul 1997 | A |
5658212 | Meurer et al. | Aug 1997 | A |
5700213 | Simpson et al. | Dec 1997 | A |
5704860 | Stief | Jan 1998 | A |
5707309 | Simpson | Jan 1998 | A |
5713809 | Yamamoto et al. | Feb 1998 | A |
5833220 | Nakakubo et al. | Nov 1998 | A |
5879255 | Yamamoto et al. | Mar 1999 | A |
5913742 | Nakamura et al. | Jun 1999 | A |
5924188 | Tokunou et al. | Jul 1999 | A |
5931754 | Stief et al. | Aug 1999 | A |
5989139 | Dusinberre et al. | Nov 1999 | A |
6086497 | Fukuda et al. | Jul 2000 | A |
6139454 | Simpson | Oct 2000 | A |
6193623 | Koch et al. | Feb 2001 | B1 |
6322468 | Wing et al. | Nov 2001 | B1 |
6361458 | Smith | Mar 2002 | B1 |
6412464 | Schneider et al. | Jul 2002 | B1 |
6435992 | Wakabayashi et al. | Aug 2002 | B2 |
6447415 | Hashimoto et al. | Sep 2002 | B1 |
6666784 | Iwamoto et al. | Dec 2003 | B1 |
6685587 | Rossato et al. | Feb 2004 | B2 |
6817958 | Kaido et al. | Nov 2004 | B2 |
6849012 | Poiret et al. | Feb 2005 | B2 |
20010044352 | Korenjak et al. | Nov 2001 | A1 |
20030008738 | Rossato et al. | Jan 2003 | A1 |
Number | Date | Country |
---|---|---|
1164729 | Nov 1997 | CN |
1650620 | Jan 1970 | DE |
0989332 | Mar 2000 | EP |
1101975 | May 2001 | EP |
2262582 | Jun 1993 | GB |
54-115467 | Sep 1979 | JP |
06-205994 | Jul 1994 | JP |
7-27191 | Jan 1995 | JP |
8-4860 | Jan 1996 | JP |
9-280330 | Oct 1997 | JP |
10009309 | Jan 1998 | JP |
10-30695 | Feb 1998 | JP |
2003-337461 | Dec 2000 | JP |
2001-124159 | May 2001 | JP |
2001-146946 | May 2001 | JP |
3243226 | Oct 2001 | JP |
Number | Date | Country | |
---|---|---|---|
20040266571 A1 | Dec 2004 | US |