JP2020153429A - Hydraulic chain tensioner - Google Patents

Abstract

To properly maintain hydraulic pressure without forming, in particular, a complex constitution, and to properly maintain the tension of a timing chain while reducing weight and cost.SOLUTION: When the tension of a timing change is abruptly increased, and a plunger 22 is abruptly pushed in, one vertical groove 40a of a second bypass passage 40 formed at an internal peripheral face of the plunger 22 and an annular groove 35a of an external periphery of a valve main body 31 forming a first bypass passage 35 of a valve assembly 24 communicate with each other. As a result, oil in a high-pressure chamber is quickly discharged into a sleeve 26 while passing a penetration hole 35b and an oil passage 31a via the annular groove 35a of the valve assembly 24 from the vertical groove 40a of the internal peripheral face of the plunger 22, and the pressure of the high-pressure chamber is not excessively raised.SELECTED DRAWING: Figure 4

Description

The present invention relates to a hydraulic chain tensioner that applies appropriate tension to a timing chain.

Generally, in a vehicle such as an automobile, the timing chain that transmits power from the crankshaft of the engine to the camshaft is provided with a hydraulic chain tensioner that presses the timing chain to apply appropriate tension. The basic configuration of such a hydraulic chain tensioner is illustrated, for example, in FIG. 8 of Patent Document 1.

The hydraulic chain tensioner shown in FIG. 8 of Patent Document 1 is slidably inserted into the plunger accommodating hole of the tensioner body, and one of the cylindrical plungers is open, and the plunger is projected from the plunger accommodating hole in the projecting direction. It is equipped with an urging compression coil spring.

An oil supply hole is provided in the plunger accommodating hole, and by supplying oil from this oil supply hole, the pressure oil chamber formed between the plunger accommodating hole and the plunger is filled with oil, and the urging force of the coil spring is applied. The pressure in the oil pressure chamber urges the plunger in the protruding direction, and the check valve prevents the oil from flowing out from the oil supply hole. Further, as the reciprocating movement of the plunger causes oil to flow through a slight gap between the plunger and the plunger accommodating hole, the oil damping effect of dampening the reciprocating movement of the plunger is obtained by the flow path resistance.

In this case, tension fluctuations occur in the timing chain according to changes in engine speed and load, and the cycle and fluctuation range of these tension fluctuations are not uniform depending on the operating conditions, so the plunger also has various cycles and speeds. It is necessary to make a reciprocating movement with. However, since the reaction force of the coil spring is determined according to the position of the plunger according to a constant spring constant, and the oil damping effect is also determined according to the speed of the plunger, the conventional basic hydraulic chain tensioner always responds to various tension fluctuations. It is difficult to exhibit appropriate reaction force and damping characteristics, and there is a risk of resonance or amplification of tension fluctuation under specific operating conditions.

Therefore, in Patent Document 1, between a tensioner body having a cylindrical plunger accommodating hole opened on one side, a cylindrical plunger slidably inserted into the plunger accommodating hole, and the plunger accommodating hole and the plunger. A chain tensioner equipped with a coil spring that is elastically stored in a formed pressure oil chamber and urges the plunger in the protruding direction. The plunger has a tip accommodating hole that opens to the tip side and accommodates the tip. It is elastically stored in a cylindrical tip plunger that is slidably inserted into the hole and a second oil pressure chamber formed between the tip accommodating hole and the tip plunger to urge the tip plunger in the protruding direction. A check valve unit equipped with a coil spring to suppress the backflow of oil flowing from the pressure oil chamber into the second pressure oil chamber, and a relief that releases oil to the pressure oil chamber side at a pressure higher than a predetermined value in the second pressure oil chamber. By equipping it with a valve unit, we are proposing a chain tensioner that can be set to exhibit appropriate reaction force and damping characteristics for both the reciprocating movement of the entire plunger and the reciprocating movement of the tip plunger.

JP-A-2017-89842

The chain tensioner disclosed in Patent Document 1 described above is provided with two plungers, a plunger and a tip plunger, as movable parts, and allows the backflow of oil flowing from the oil pressure chamber on the plunger side to the second oil pressure chamber on the tip plunger side. A check valve unit that suppresses the oil and a relief valve unit that releases oil to the oil pressure chamber side at a pressure equal to or higher than a predetermined value in the second oil pressure chamber are provided. For this reason, the structure becomes complicated in a narrow space of small parts, and not only the weight of the moving part and the tensioner as a whole increases, but also the cost increases.

The present invention has been made in view of the above circumstances, and is a hydraulic chain tensioner capable of appropriately maintaining hydraulic pressure without particularly complicated configuration, and appropriately maintaining tension of timing chains while reducing weight and cost. Is intended to provide.

The hydraulic chain tensioner according to one aspect of the present invention is a hydraulic chain tensioner that applies a predetermined tension to a timing chain, and has a cap-like shape in which the tip end side pushes the chain freely and protrudes from the housing and the base end portion is opened. A check provided in the plunger with a gap for generating a predetermined oil damping between the plunger and the inner surface of the plunger, and allowing only the flow of oil from the base end side to the tip end side of the plunger. A valve assembly having a valve, a return spring that urges the valve assembly and the tip of the plunger to separate from each other, and the plunger are slidably exteriorized, and one end surface on the base end side abuts on the housing. A first bypass is provided with a cylindrical sleeve whose tip end side end surface is in contact with the valve assembly, and the valve assembly bypasses the check valve and communicates the gap with the inside of the sleeve. A second bypass passage that communicates the inside of the tip of the plunger with the first bypass passage when the plunger moves by a predetermined amount in a direction approaching the valve assembly on the inner peripheral surface of the plunger while providing a passage. Is provided.

According to the present invention, the hydraulic pressure can be appropriately maintained without a particularly complicated configuration, and the tension of the timing chain can be appropriately maintained while reducing the weight and cost.

Schematic explanatory view showing the cam chain chamber on the left bank side of the horizontally opposed engine Sectional view of the main part of the hydraulic chain tensioner Explanatory drawing showing a valve assembly Explanatory drawing showing the state where the plunger is pushed by the high tension of the chain Explanatory drawing showing a state in which the plunger is further pushed by the high tension of the chain.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an example in which the present invention is applied to a timing chain of a horizontally opposed engine, and reference numeral 1 in FIG. 1 indicates a cam chain chamber on the left bank side of the horizontally opposed engine. Since the cam chain chamber on the right bank side of the engine is configured in substantially the same manner, the description thereof will be omitted.

A crank sprocket 3 is attached to the crankshaft 2 of the engine. A timing chain 8 is wound between the crank sprocket 3 and the cam sprocket 6L and 7L attached to the intake camshaft 4L and the exhaust camshaft 5L of the left bank, respectively. Then, the rotation of the crankshaft 2 is transmitted to the intake camshaft 4L and the exhaust camshaft 5L of the left bank by the timing chain 8.

Further, on both the left and right sides of the crank sprocket 3, chain tensioner levers 10 that are pressed by the hydraulic chain tensioner 9 and come into contact with the timing chain 8 are interposed. The chain tensioner lever 10 applies tension to the timing chain 8 and also guides the track of the chain and prevents fluttering, and one end side thereof is swingably supported by the cylinder block of the engine.

In the present embodiment, the chain tensioner lever 10 is provided between the intake side cam sprocket 6L and the crank sprocket 3. Further, between the exhaust side cam sprocket 7L and the crank sprocket 3, a fixed guide 11 that comes into contact with the timing chain 8 is arranged along a predetermined chain trajectory.

The chain tensioner lever 10 is provided with a boss portion 10b into which a bolt or the like for axially supporting the cylinder block is inserted on one end side in the longitudinal direction of an elongated curved plate-shaped lever body 10a. On the other end side of the lever body 10a separated from the boss portion 10b, a plunger contact portion 10c to which the plunger 22 of the hydraulic chain tensioner 9 is in contact is provided.

Further, on the outside of the curved shape of the lever body 10a, a chain guide surface 10d that contacts and slides on the timing chain 8 is formed along the longitudinal direction of the lever. Side wall portions 10e for sandwiching the timing chain 8 in the width direction and preventing the chain from coming off are erected on both side portions of the chain guide surface 10d near the boss portion 10b.

As shown in FIG. 2, the hydraulic chain tensioner 9 mainly includes a housing 21 fixed to the engine and a plunger 22 capable of pressing the timing chain 8 via the chain tensioner lever 10. The housing 21 is formed with a cylinder 21a that communicates with the oil gallery 15 of the engine. The plunger 22 is formed in a cap shape in which the tip portion 22a side is freely retractable from the cylinder 21a and the base end portion 22b is open.

Further, in the cylinder 21a, a cylindrical sleeve 26 for slidably exteriorizing the plunger 22 is provided. In the sleeve 26, one end surface 26a on the base end side is in contact with the housing 21, and the other end surface 26b on the tip end side is in contact with the valve assembly 24 provided in the plunger 22. The valve assembly 24 has a gap 23 for generating a predetermined oil damping with the inner surface of the plunger 22, and is slidably installed in the plunger 22.

A return spring 25 is provided between the valve assembly 24 and the inner surface of the tip portion 22a of the plunger 22 so as to constantly urge the valve assembly 24 and the tip portion 22a of the plunger 22 to separate from each other. Further, the housing 21 is provided with a ratchet mechanism 27 that regulates the recessed length of the plunger 22 from the housing 21 within a predetermined range.

In detail, as shown in FIG. 3, the valve assembly 24 has an oil passage 31a opened in the sleeve 26 at a substantially central portion, and a valve body 31 arranged with a gap 23 in the plunger 22. A check ball 32 that can block one end of the oil passage 31a of the valve body 31, a retainer 33 provided on one end side of the valve body 31, and a check ball 32 between the retainer 33 and the check ball 32. It has a check valve 30 including a valve spring 34 provided at one end of the valve spring 34 so as to be constantly urged. The check valve 30 forms a check valve that allows oil to flow from the base end 22b side of the plunger 22 to the tip 22a side.

Further, the valve assembly 24 has a first bypass passage 35 that bypasses the check valve 30 and communicates between the gap 23 between the inner surface of the plunger 22 and the inside of the sleeve 26. Specifically, the first bypass passage 35 communicates between the gap 23 with the inner surface of the plunger 22 and the inside of the sleeve 26 via the oil passage 31a. In the present embodiment, the first bypass passage 35 is formed by an annular groove 35a having a predetermined depth provided on the outer peripheral surface of the valve body 31 and a through hole 35b penetrating from the inside of the annular groove 35a into the oil passage 31a. It is formed. At least one through hole 35b may be provided.

Further, when the plunger 22 is pushed to a predetermined depth in the direction in which the tip portion 22a of the plunger 22 approaches the valve assembly 24 on the inner peripheral surface of the plunger 22 corresponding to the first bypass passage 35 of the valve body 31. A second bypass passage 40 is provided for communicating the pressure chamber on the inner surface of the tip portion 22a of the plunger 22 and the annular groove 35a.

That is, when the plunger 22 is pushed into the cylinder 21a and moved by a predetermined amount by the first bypass passage 35 of the valve body 31 and the second bypass passage 40 on the inner peripheral surface of the plunger 22, the first bypass passage 35 and the second bypass passage 35 and the second. A function as a relief valve is realized in which the bypass passage 40 communicates with the plunger 22 so that the pressure on the tip end side of the plunger 22 does not become excessively high.

In the present embodiment, the second bypass passage 40 is formed as two longitudinal grooves 40a and 40b provided on the inner peripheral surface of the plunger 22. In the vertical grooves 40a and 40b, the groove start position on the tip 22a side of the plunger 22 and the groove end position on the valve assembly 24 side are different from each other, and the groove start position and the groove end position of the plunger 22 are determined by the engine specifications. It is set according to the stroke range.

Further, by providing the annular groove 35a on the valve assembly 24 side with respect to the vertical grooves 40a and 40b of the plunger 22, even if the valve assembly 24 rotates, the pressure chamber on the inner surface of the tip portion 22a of the plunger 22 of the plunger 22 can be formed. It is formed so as to reliably communicate with the inside of the sleeve 26.

The second bypass passage 40 on the plunger 22 side may be a single vertical groove by combining the two vertical grooves 40a and 40b, and is not limited to the vertical groove, but with respect to the axial direction of the plunger 22. It may be a spiral groove in the diagonal direction.

Further, in the present embodiment, the vertical grooves 40a and 40b as the second bypass passage 40 on the plunger 22 side are provided with the annular groove 35a and the through hole 35b as the first bypass passage 35 on the valve assembly 24 side. However, it is not limited to this.

For example, the annular groove 35a on the valve assembly 24 side is omitted, and the plurality of through holes 35b are used as the first bypass passage 35, and at least two of the plurality of through holes 35b are straddled on the inner peripheral surface of the plunger 22. The second bypass passage 40 may be formed by combining the lateral groove in the circumferential direction and the vertical groove communicating with the lateral groove.

Next, the operation of the present embodiment to which the above-mentioned hydraulic chain tensioner 9 is applied will be described.

When the engine rotates and oil is supplied from the oil gallery 15, the supplied oil passes through the inside of the sleeve 26, passes through the check valve 30, and is sent into the plunger 22 on the tip side of the valve assembly 24. As a result, the inside of the plunger 22 on the tip side of the valve assembly 24 receives the tension of the timing chain 8 and becomes a high pressure chamber. The inside of the sleeve 26 on the base end side of the valve assembly 24 is a low pressure chamber lower than the high pressure chamber.

When the tension of the timing chain 8 is small when the engine is operating with a low load, when the plunger 22 is projected from the housing 21 by the urging force of the return spring 25, the oil shortage due to the protrusion of the plunger is checked from the inside of the sleeve 26. It is supplied via the valve 30 and the high pressure state of the high pressure chamber is maintained.

On the contrary, when the tension of the timing chain 8 becomes large and the plunger 22 is pushed in, the oil in the high pressure chamber flows to the outside of the sleeve 26 through the gap 23 between the inner surface of the plunger 22 and the valve body 31 of the check valve 30. Be guided. At this time, the movement of the plunger 22 is regulated by a predetermined damping characteristic due to the flow path resistance when the oil flows through the gap 23, and the timing chain 8 is prevented from fluttering.

Next, when the engine is in a high load operation state and the tension of the timing chain 8 is further increased, a situation occurs in which the plunger 22 is suddenly pushed toward the valve assembly 24 side. When the plunger 22 moves to the valve assembly 24 side by a preset stroke amount, as shown in FIG. 4, one vertical groove 40a of the second bypass passage 40 provided on the inner peripheral surface of the plunger 22 and the valve assembly The annular groove 35a on the outer periphery of the valve body 31 forming the first bypass passage 35 of 24 communicates with the groove 35a. As a result, the oil in the high pressure chamber is discharged from the vertical groove 40a on the inner peripheral surface of the plunger 22 through the annular groove 35a of the valve assembly 24, through the through hole 35b and the oil passage 31a, and into the sleeve 26.

As a result, even if the tension of the timing chain 8 suddenly increases and the plunger 22 moves rapidly, the oil in the high pressure chamber can be quickly discharged through the second bypass passage 40 and the first bypass passage 35. That is, it is possible to prevent the pressure in the high pressure chamber from rising excessively because the amount of oil discharged from the gap 23 between the inner surface of the plunger 22 and the valve body 31 of the check valve 30 is not in time for the sudden movement of the plunger 22. can do.

Further, when the operating load of the engine increases and the tension of the timing chain 8 becomes larger, the plunger 22 is further pushed in and the entire vertical groove 40a overlaps with the length of the valve body 31 as shown in FIG. , The discharge of oil from the vertical groove 40a may be hindered. In preparation for such a case, the inner peripheral surface of the plunger 22 is provided with another vertical groove 40b whose groove start position and groove end position are different from those of the vertical groove 40a.

The vertical groove 40b is arranged so that the groove end position of the vertical groove 40b coincides with the annular groove 35a when the entire vertical groove 40a overlaps with the valve main body 31. Therefore, even if one of the flutes 40a of the plunger 22 exceeds the effective functioning range due to excessive tension from the timing chain 8, the other flute 40b and the annular groove 35a communicate with each other, resulting in high pressure. It is possible to prevent the chamber pressure from becoming excessive.

As described above, in the present embodiment, the pressure of the high pressure chamber in the plunger 22 is provided on the inner peripheral surface of the plunger 22 in response to the rapid movement of the plunger 22 due to the rapid increase in the tension of the timing chain 8. The two bypass passages 40 and the first bypass passage 35 provided in the valve assembly 24 have a simple structure of relief to the inside of the sleeve 26. As a result, the weight of the entire hydraulic chain tensioner including the moving parts can be reduced to reduce costs, while the timing chain tension fluctuations that occur in response to changes in engine speed and load can be reliably absorbed. It is possible to maintain the tension of the engine properly.

Further, in the present embodiment, the second bypass passage 40 on the plunger 22 side is the vertical groove 40a and 40b, and the first bypass passage 35 on the valve assembly 24 side is inside the annular groove 35a and the annular groove 35a on the outer peripheral surface of the valve body 31. Since it is formed by a through hole 35b penetrating through the oil passage 31a, it is possible to assemble the plunger 22 and the valve assembly 24 without worrying about the directionality, improving the assembleability and reducing the manufacturing cost. Can contribute to.

1 Camchain room 2 Crankshaft 3 Crank sprocket 4L Intake camshaft 5L Exhaust camshaft 6L Intake side cam sprocket 7L Exhaust side cam sprocket 8 Timing chain 9 Hydraulic chain tensioner 10 Chain tensioner lever 10c Plunger contact part 15 Oil gallery 21 Cylinder 22 Plunger 22a Tip 22b Base end 23 Gap 24 Valve assembly 25 Return spring 26 Sleeve 26a One end surface 26b Other end surface 27 Ratchet mechanism 30 Check valve 31 Valve body 31a Oil passage 32 Check ball 33 Retainer 34 Valve spring 35 1st bypass Passage 35a Circular groove 35b Through hole 40 Second bypass passage 40a, 40b Vertical groove

Claims (4)

In a hydraulic chain tensioner that applies a predetermined tension to a timing chain,
A cap-shaped plunger with the tip side protruding from the housing so that the chain can be pressed freely and the base end being opened.
It has a check valve provided in the plunger with a gap for generating a predetermined oil damping from the inner surface of the plunger and allowing only oil flow from the base end side to the tip end side of the plunger. With valve assembly,
A return spring that urges the valve assembly and the tip of the plunger to separate from each other.
A cylindrical sleeve in which the plunger is slidably mounted, one end surface on the base end side is in contact with the housing, and the other end surface on the tip end side is in contact with the valve assembly.
With
The valve assembly is provided with a first bypass passage that bypasses the check valve and communicates between the gap and the inside of the sleeve.
A second bypass passage is provided on the inner peripheral surface of the plunger to communicate the inside of the tip end portion of the plunger and the first bypass passage when the plunger moves by a predetermined amount in a direction approaching the valve assembly. Characterized hydraulic chain tensioner. The first bypass passage is formed by an annular groove provided on the outer peripheral surface of the check valve and a through hole communicating the inside of the annular groove and the inside of the sleeve.
The hydraulic chain tensioner according to claim 1, wherein the second bypass passage is formed by a vertical groove provided in the longitudinal direction of the plunger on the inner peripheral surface of the plunger. The hydraulic chain tensioner according to claim 2, wherein the flutes are two flutes having different groove start positions and groove end positions. Claims 1 to 1, wherein the plunger forms a high-pressure chamber of oil on the distal end side of the valve assembly and a low-pressure chamber of oil having a pressure lower than that of the high-pressure chamber on the proximal end side of the valve assembly. The hydraulic chain tensioner according to any one of 3.

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