Chain tensioner

Abstract

Provided is a chain tensioner that can always provide a suitable reaction force and damping force to various tension fluctuations of the chain, has a simple structure, is easy to produce, and also enables a reduction in the production cost. The chain tensioner 100 has a plunger 120 inserted in a plunger bore 111, and biasing means 140 for biasing the plunger in a protruding direction of the plunger. A plurality of biasing means 140 are accommodated so as to freely expand and contract inside a high pressure chamber 101 and arranged in series along the protruding direction of the plunger 120, with a separator plate 130 interposed therebetween. The separator plate 130 has one or more oil passages that adjust oil flow.

Claims

1. A chain tensioner comprising: a tensioner body having a cylindrical plunger bore with an open end; a cylindrical plunger with a bottom, slidably inserted in the plunger bore; and biasing means that biases the plunger in a protruding direction of the plunger and is accommodated so as to freely expand and contract inside a high pressure chamber formed to extend over interiors of the plunger bore and the plunger, the biasing means being provided in plurality in series along the protruding direction of the plunger, a separator plate being provided between the plurality of biasing means, and the separator plate partitioning the high pressure chamber into a plurality of compartments and including one or more oil passages that adjust flow of oil between the compartments of the high pressure chamber, wherein the outer periphery of the plunger slides on the inner wall of the cylindrical plunger bore, and wherein the separator plate is independently formed in a plate-like shape.

2. The chain tensioner according to claim 1, wherein the oil passage is formed by one or more through holes provided to the separator plate.

3. The chain tensioner according to claim 1, wherein the oil passage is formed by one or more grooves or cut-outs provided on an outer circumferential edge of the separator plate.

4. The chain tensioner according to claim 1, wherein at least one of the plurality of biasing means is formed by a coil spring, and the separator plate includes a protrusion that extends in the protruding direction of the plunger, and stops the coil spring from moving.

5. The chain tensioner according to claim 4, wherein the protrusion includes an inner circumferential protrusion located inside the coil spring.

6. The chain tensioner according to claim 4, wherein the protrusion includes an outer circumferential protrusion that is located outside the coil spring and forms an outer circumferential edge of the separator plate.

7. The chain tensioner according to claim 1, wherein three or more of the biasing means are provided in series along the protruding direction of the plunger, and the separator plate is provided between each pair of biasing means.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a cross-sectional view of a chain tensioner according to a first embodiment of the present invention;

(2) FIG. 2 is a perspective side view of the chain tensioner according to the first embodiment of the present invention;

(3) FIG. 3 is a perspective view of a separator plate of the chain tensioner according to the first embodiment of the present invention;

(4) FIG. 4 is a perspective view of a first variation example of the separator plate;

(5) FIG. 5 is a perspective view of a second variation example of the separator plate;

(6) FIG. 6 is a perspective view of a third variation example of the separator plate;

(7) FIG. 7 is a perspective view of a fourth variation example of the separator plate;

(8) FIG. 8 is a perspective view of a fifth variation example of the separator plate;

(9) FIG. 9 is a perspective view of a sixth variation example of the separator plate;

(10) FIG. 10 is a perspective view of a seventh variation example of the separator plate;

(11) FIG. 11 is a perspective view of an eighth variation example of the separator plate;

(12) FIG. 12 is a perspective side view of a chain tensioner according to a second embodiment of the present invention;

(13) FIG. 13 is an explanatory diagram of the chain tensioner used in the chain guide mechanism of an engine; and

(14) FIG. 14 is a schematic explanatory diagram of a conventional chain tensioner.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(15) The chain tensioner of the present invention includes a tensioner body having a cylindrical plunger bore with an open end, a cylindrical plunger with a bottom, slidably inserted in the plunger bore, and biasing means that biases the plunger in a protruding direction of the plunger and is accommodated so as to freely expand and contract inside a high pressure chamber formed to extend over interiors of the plunger bore and the plunger. The biasing means are provided in plurality in series along the protruding direction of the plunger. A separator plate is provided between the plurality of biasing means. The separator plate partitions the high pressure chamber into a plurality of compartments, and has one or more oil passage that adjust flow of oil between the compartments of the high pressure chamber. The chain tensioner may be embodied in any specific form as long as it includes these features and as long as it can always produce a suitable reaction force and damping force to various chain tension fluctuations, has a simple structure, is easy to produce, and also enables a reduction of production cost.

(16) For example, the separator plate may be made of any material as long as it does not break or deform by the pressure from the biasing means, such as resin, or metal such as iron or aluminum.

(17) The plurality of biasing means may be in any form such as coil springs, plate springs and the like, and made of any material such as metal, rubber, resin, and the like. The plurality of biasing means may differ from each other in material or shape.

Embodiment 1

(18) A chain tensioner 100 according to a first embodiment of the present invention will be described with reference to the drawings.

(19) The chain tensioner 100 according to a first embodiment of the present invention includes, as shown in FIG. 1 to FIG. 3, a tensioner body 110 having a cylindrical plunger bore 111 with an open end, a cylindrical plunger 120 with a bottom, slidably inserted in the plunger bore 111, a first coil spring 141 and a second coil spring 142 that bias the plunger 120 in a protruding direction of the plunger 120, and a separator plate 130.

(20) The first coil spring 141, separator plate 130, and second coil spring 142 are accommodated in series in a high pressure chamber 101 formed to extend over interiors of the plunger bore 111 and the plunger 120, the separator plate 130 partitioning the high pressure chamber 101 into a first high pressure chamber 102 and a second high pressure chamber 103.

(21) The separator plate 130 has a through hole 131 that forms an oil passage, and is designed to provide damping characteristics when the plunger 120 reciprocates, with the flow resistance of the oil passing through the through hole 131 and moving to and from the first high pressure chamber 102 and the second high pressure chamber 103 as the separator plate 130 moves back and forth inside the plunger 120.

(22) The chain tensioner 100 according to this embodiment is securely fixed inside an engine having a chain guide mechanism. For this purpose, the tensioner body 110 has mounting holes 114 for bolts or the like to pass through, as shown in FIG. 1 and FIG. 2.

(23) A check valve 150 is disposed at the bottom of the plunger bore 111 in the tensioner body 110.

(24) The check valve 150 includes a ball seat 151, a check ball 152 that can make tight contact with the oil passage in the ball seat 151, and a retainer 153 that guides the check ball 152. Oil is constantly supplied through the check valve 150 from the side on which the tensioner is mounted to the engine.

(25) How the chain tensioner 100 according to the first embodiment of the present invention configured as described above operates will be explained.

(26) During the engine operation, oil is constantly supplied from oil supply means provided in a mounting wall portion (not shown) through the check valve 150 so that the first high pressure chamber 102 and second high pressure chamber 103 are kept always filled with oil.

(27) The chain tension fluctuates in various cycles and with various amplitudes depending on a variety of conditions such as changes in the engine rpm and loads during the engine operation.

(28) When the plunger 120 moves in a pressing direction due to such changes in the chain tension, the oil inside the first high pressure chamber 102 leaks out through a small gap between the plunger bore 111 and the plunger 120, whereby a certain braking force is generated in accordance with the moving speed of the plunger 120 owing to the damping characteristics provided by flow resistance of the oil.

(29) Also, a certain reaction force is produced by compression of the first coil spring 141 and second coil spring 142, by the amount determined by their respective spring constants.

(30) Furthermore, a certain braking force is generated in accordance with the compression speed of the second coil spring 142 owing to the damping characteristics provided by flow resistance of the oil passing through the through hole 131 from the second high pressure chamber 103 into the first high pressure chamber 102 when the separator plate 130 moves by the amount of compression of the second coil spring 142.

(31) On the other hand, when the plunger 120 moves in the protruding direction, oil is supplied into the first high pressure chamber 102 through the check valve 150. As there is no oil flow between the plunger bore 111 and the plunger 120, no braking force is produced there. However, as the separator plate 130 moves by the amount of expansion of the second coil spring 142, a certain braking force is generated in accordance with the expansion speed of the second coil spring 142 owing to the damping characteristics provided by flow resistance of the oil passing through the through hole 131 from the first high pressure chamber 102 into the second high pressure chamber 103.

(32) Also, as the first coil spring 141 and second coil spring 142 expand, the reaction force is reduced by the amount of expansion that is determined by their respective spring constants.

(33) This way, by providing the separator plate 130, the damping characteristics associated with compression and expansion are made different between the first coil spring 141 and the second coil spring 142. Therefore, by selecting and combining the spring constants of respective coil springs and the damping characteristics of the separator plate 130 as appropriate, the tensioner can be designed to operate suitably to various tension fluctuations of the chain and elongation of the chain due to heat or aging.

(34) For example, the second coil spring 142 may have a spring constant smaller than that of the first coil spring 141. For tension fluctuations in short cycles and with small amplitudes caused by vibration or the like during normal operation of the engine, the relative moving speed of the separator plate 130 is lower and it provides little damping effect. Therefore, such fluctuations can be absorbed by the second coil spring 142 having a smaller spring constant with good response. For tension fluctuations with large amplitudes caused by a sudden change in the load or engine rpm, the first coil spring 141 having a larger spring constant can act to a greater extent.

(35) Even when the plunger 120 advances in the protruding direction along with a long-term elongation of the chain due to heat or aging, there will be less change in the biasing force (reaction forces of the first coil spring 141 and second coil spring 142) in accordance with the position of the plunger 120, because the second coil spring 142 has a small spring constant.

(36) The damping characteristics provided by the separator plate 130 are adjustable through setting of the size of the through hole 131 as appropriate.

(37) The damping characteristics can be set variously by changing the shape and number of the through hole 131 thereby to adjust the flow rate of the oil.

(38) For example, as shown in FIG. 4, the through hole 131t in the separator plate 130a may be tapered so that the flow resistance of the oil will be different depending on the moving direction of the separator plate 130a (moving direction of the plunger 120), whereby the damping characteristics may be differed between when the springs are compressed and when they are expanded.

(39) Alternatively, a plurality of small through holes 131s may be provided as in the separator plate 130b shown in FIG. 5, or a combination of through holes 131s and 131b of different sizes may be provided as in the separator plate 130c shown in FIG. 6, or a plurality of tapered through holes 131t may be provided as in the separator plate 130d shown in FIG. 7. This way, selection of the type, arrangement, and number of the through holes 131s, 131b, and 131t allows a wide variety of damping characteristics to be set, and different appearances of separator plates having different damping characteristics will facilitate visual recognition when selecting one during design and production.

(40) To set flow resistance and damping characteristics of the separator plate 130, an oil passage may be formed to allow flow of oil between an outer circumferential portion of the separator plate 130 and an inner circumferential surface of the plunger 120, instead of or in addition to the through hole 131.

(41) For example, the separator plate 130e shown in FIG. 8 has two cut-outs 132, while the separator plate 130f shown in FIG. 9 has six grooves 133.

(42) The type, shape, arrangement, number, and combination of through holes, cut-outs, and grooves of the separator plates shown in FIG. 3 to FIG. 8 are illustrated only as examples, and any type or shape may be employed in any arrangement, number, and combination, as long as they provide desired flow resistance and damping characteristics.

(43) Since the separator plate 130 forms a seat for the coil springs on both sides, it may have protrusions that restrict relative movement between the separator plate and the coil springs so that the coil springs will stay on the seats more stably.

(44) For example, the separator plate 130g shown in FIG. 10 has an inner circumferential protrusion 134 at the center, and a through hole 131 is provided in this inner circumferential protrusion 134.

(45) As the inner circumferential protrusion 134 fits with the inner circumference of the coil spring, it restricts movement of the spring relative thereto.

(46) Also, because the through hole 131 is formed in the inner circumferential protrusion 134, the oil passage is long so that flow resistance is larger and the damping characteristics can be improved.

(47) The diameters and protruding amounts of inner circumferential protrusions 134 on both sides may be different from one another to match the respective coil springs.

(48) The length of the inner circumferential protrusion 134 may be made equal to or greater than the length of the coil spring when it is compressed most, so that the inner circumferential protrusion 134 makes contact with the plunger or tensioner body when the coil spring is largely compressed.

(49) This prevents the wires of the coil springs from contacting each other, whereby wear on the spring wires can be prevented.

(50) The separator plate 130h shown in FIG. 11 has an outer circumferential protrusion 135 that forms the outer circumferential edge.

(51) The outer circumferential protrusion 135 fits with the outer circumference of the coil spring and restricts movement of the spring relative thereto. The separator plate 130h can smoothly move in a stable orientation inside the plunger so that it can provide damping characteristics in a stable manner.

(52) The diameters and protruding amounts of outer circumferential protrusions 135 on both sides may be different from each other to match respective coil springs. The protrusion may not necessarily extend all around as shown but a plurality of protrusions may be intermittently provided along the outer periphery.

Embodiment 2

(53) The chain tensioner 100b according to a second embodiment of the present invention includes an additional separator plate 130 as well as a third coil spring 143 as compared to the chain tensioner 100 according to the previously described first embodiment, as shown in FIG. 12.

(54) The first coil spring 141, separator plate 130, second coil spring 142, separator plate 130, and third coil spring are accommodated in series in a high pressure chamber 101 formed to extend over interiors of the plunger bore 111 and the plunger 120. The two separator plates 130 partition the high pressure chamber 101 into three compartments, i.e., a first high pressure chamber 102, a second high pressure chamber 103, and a third high pressure chamber 104.

(55) The chain tensioner is configured the same in other respects as the chain tensioner 100 according to the first embodiment (same components and structures are given the same reference numerals as those of the first embodiment).

(56) In this embodiment, two separator plates 130 and three coil springs 141, 142, and 143 are provided. The damping characteristics associated with compression and expansion are different between the first coil spring 141, second coil spring 142, and third coil spring 143. Therefore, by selecting and combining the spring constants of respective coil springs and the damping characteristics of the respective separator plates 130 as appropriate, the tensioner can be designed to operate even more suitably to various tension fluctuations of the chain and elongation of the chain due to heat or aging.

(57) While specific examples of the chain tensioner according to the present invention have been described in the embodiments above, the chain tensioner according to the present invention is not limited to these examples, and the shapes, positions, sizes, and positional relationships with each other of various constituent parts may be changed in various manners.

(58) Other components commonly included in a chain tensioner, such as a ratchet mechanism, may of course be added to the configurations of the embodiments described above.

(59) The chain tensioner of the present invention may not necessarily be applied to a chain guide mechanism that uses a guide shoe for slidably guiding a transmission chain such as an endless roller chain passing over respective sprockets of a crankshaft and a cam shaft in an engine room, but may also be adopted in applications where the chain is slidably guided directly by the distal end of the plunger.

(60) The chain tensioner may not necessarily be applied to a chain transmission mechanism but also to similar transmission mechanisms that use belts, ropes and the like, and can be applied in a variety of industrial fields where it is necessary to deliver enough oil at restart after a long time after the oil supply was stopped.