JP2017201189A - Tensioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit failure resulting from a thermal expansion difference between a cylinder head 2 and a cylinder block 1 when a tensioner 9 for applying a predetermined tensile force is disposed at a timing chain 7 for driving cam shafts 5, 6 of a valve train of an engine 100 so that the tensioner 9 is spanned between the cylinder head 2 and the cylinder block 1.SOLUTION: A tensioner includes: a plunger 91 which presses a movable guide 8b to a loose side span 7b of a timing chain 7; and a housing 90 which holds the plunger 91 so that the plunger 91 can move forward and rearward to the movable guide 8b. While the housing 90 is fastened to the cylinder head 2 in a first fastening portion (a first boss part 90b), a chain cover member (for example, an inner cover 11), which is attached spanned between the cylinder head 2 and the cylinder block 1, is fastened in a second fastening portion (a second boss part 90c).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a tensioner for applying tension to a timing chain of an engine, and more particularly to a structure for fastening a tensioner housing to a cylinder head or the like.

  2. Description of the Related Art Conventionally, for example, in an engine mounted on a vehicle, a valve-operated camshaft that drives an intake valve and an exhaust valve is disposed on a cylinder head and is driven by a timing chain. For example, in the engine described in Patent Document 1, a timing chain is wound between a drive sprocket of a crankshaft and a driven sprocket of a camshaft to transmit the rotational force of the crankshaft to the camshaft.

  In order to properly maintain the tension of the timing chain, a tensioner (referred to as a tensioner lifter in the same document) that presses the main arm (movable guide) so as to be in sliding contact with the loose side is provided. The tensioner includes a plunger that presses the movable guide against the loose side of the timing chain, and a housing that holds the plunger so as to be able to advance and retract toward the movable guide. The housing has two bolts on the front side wall surface of the cylinder head. It is concluded with.

JP 2009-250384 A

  By the way, in a multi-cylinder engine generally mounted on a vehicle, the crankshaft undergoes rotational fluctuations due to intermittent combustion of each cylinder, and this is caused by fluctuations in the tension of the timing chain that is driven. Thus, so-called string vibration (transverse vibration) occurs. Then, referring to FIG. 4 according to the embodiment of the present invention, as schematically shown in FIG. 4, the amplitude of the timing chain 7 is caused by resonance between the crank sprocket 4a and the cam sprockets 5a and 6a. An “abdomen” region that increases and a “node” region that decreases in amplitude appear.

  Therefore, if the tensioner 9 is disposed on the portion of the slack side 7b of the timing chain 7 where the amplitude is “belly” and the movable guide 8b is pressed, the lateral vibration of the timing chain 7 can be effectively suppressed. it can. In this way, since the tension applied to the timing chain may be small, the mechanical loss can be reduced, and the width of the timing chain can be increased to increase the strength of the timing chain, and the weight can be increased. Can be avoided.

  However, if the movable guide is pressed against the portion of the “belly” amplitude, the tensioner may have to be disposed so as to straddle between the cylinder head and the cylinder block. In this case, the housing of the tensioner is usually fastened to the cylinder head at the upper fastening portion and fastened to the cylinder block at the lower fastening portion.

  When the tensioner housing is fastened to the cylinder head and the cylinder block in this way, the following problems occur due to the difference in thermal expansion between the two. That is, since the amount of thermal expansion is generally larger in the cylinder head, the housing 90 becomes slanted as shown schematically and exaggeratedly in FIG. become. For this reason, the fastening bolts 13 and 14 are liable to be loosened, and the housing 90 may be cracked around the fastening portion.

  Although not shown, it is also conceivable that a fastened portion is provided so as to protrude downward from the lower portion of the cylinder head, and the second fastening portion of the housing is fastened to the fastened portion instead of the cylinder block. However, if there is a portion protruding below the cylinder head in this way, it may become a problem during manufacture, transportation, assembly, etc. of the cylinder head, which may cause a problem.

  In view of these points, an object of the present invention is to devise a mounting structure of a tensioner disposed so as to straddle the cylinder head and cylinder block of the engine, and to suppress problems caused by the difference in thermal expansion between the cylinder head and the cylinder block. There is.

  In order to achieve the above object, the present invention relates to a tensioner for applying a predetermined tension to a timing chain for driving a camshaft of an engine valve system, and on the loose side of the timing chain. When a plunger that presses the movable guide and a housing that holds the plunger so as to advance and retract toward the movable guide are provided, the housing is fastened to the cylinder head of the engine at the first fastening portion, In the fastening part of 2, it was set as the structure fastened to the chain cover member attached ranging over the cylinder block from the said cylinder head.

  According to the above mounting structure, the tensioner of the present invention has its housing fastened to the cylinder head at the first fastening portion, while being fastened to the chain cover member instead of the cylinder block at the second fastening portion. Therefore, even if the thermal expansion difference between the cylinder head and the cylinder block increases, the inclination of the housing due to this does not become so large.

  That is, the chain cover member that accommodates the timing chain is usually provided from the cylinder head to the lower end of the cylinder block, and is long in the vertical direction. Therefore, even if the thermal expansion difference between the cylinder head and the cylinder block is large, the chain cover member The slope does not become too large. For this reason, an unreasonable force applied to the first and second fastening portions of the housing is reduced, and loosening of the fastening bolts is suppressed, and there is less fear of causing cracks in the housing.

  Specifically, the chain cover member may be an inner cover of an inner cover and an outer cover that form a storage chamber for the timing chain. The inner cover is formed with, for example, a blow-by gas passage and an oil dropping passage, and is provided so as to cover the side walls of the cylinder head and the cylinder block. Therefore, in the first fastening portion of the housing fastened to the cylinder head, a fastening member such as a bolt penetrates the inner cover and is fastened to the cylinder head.

  As described above, the tensioner according to the present invention is fastened to the cylinder head at the first fastening portion when the housing is disposed so as to straddle the cylinder head and the cylinder block of the engine, while at the second fastening portion. Since it is fastened to the chain cover member, it is possible to reduce the unreasonable force applied to the fastening part due to the difference in thermal expansion between the cylinder head and the cylinder block, thereby suppressing the loosening of the fastening bolts and causing the housing to crack. Less.

It is a schematic block diagram of the drive train of the valve operating system of the engine which concerns on embodiment of this invention. It is explanatory drawing which shows typically the positional relationship of an engine cylinder head, a cylinder block, a chain cover member, and a tensioner. It is an enlarged view of the tensioner in FIG. It is explanatory drawing which shows typically the string vibration of a timing chain, and suitable arrangement | positioning of a tensioner. It is sectional drawing which shows the attachment structure of a tensioner. FIG. 3 is a view corresponding to FIG. 2 when a difference in thermal expansion occurs between the cylinder head and the cylinder block. FIG. 7 is a view corresponding to FIG. 6 when the housing of the tensioner is fastened to the cylinder head and the cylinder block.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present embodiment, a case where the present invention is applied to a gasoline engine mounted on a vehicle such as an automobile will be described. As schematically shown in FIGS. 1 and 2, the engine 100 according to the present embodiment includes, for example, a cylinder block 1 in which four cylinders 1a (shown by broken lines in FIG. 2) are arranged in a line, and the cylinder And a cylinder head 2 attached to the upper part of the block 1. An oil pan 3 is attached to the lower part of the cylinder block 1, and a head cover 10 is attached to the upper part of the cylinder head 2.

  Then, on one side (right side in FIG. 2) in which the four cylinders 1a are arranged (cylinder row direction), as shown in FIG. A drive train of a valve train that is transmitted to 6 is disposed. That is, the cylinder head 2 is provided with an intake port and an exhaust port (not shown) so as to communicate with the combustion chamber in each cylinder 1a, and the intake and exhaust valves that open and close these are driven by the camshafts 5 and 6, respectively. It has become so.

  Sprockets 4a, 5a, and 6a are attached to the crankshaft 4 and the camshafts 5 and 6, respectively, and a timing chain 7 is wound thereon. Then, the crankshaft 4 rotates clockwise in FIG. 1 during the operation of the engine 100, and the camshafts 5 and 6 are rotated in synchronism with this, so that the intake valve and the exhaust valve are respectively suitable for each cylinder 1a. It is designed to open and close.

  The tension is relatively increased on the tight side (right side in FIG. 1) of the timing chain 7 pulled by the sprocket 4a of the rotating crankshaft 4, and on the other loose side (left side in FIG. 1), the timing is increased. The tension of the chain 7 becomes relatively small. Accordingly, the fixed guide 8a is pressed against the tension side span 7a of the timing chain 7, while the movable guide 8b is pressed against the loose side span 7b to apply a predetermined tension.

  That is, the movable guide 8b has a base end portion (lower end portion in FIG. 1) supported so as to be rotatable around the support shaft 8c of the cylinder block 1, and a distal end side (upper side in FIG. 1) swings. It has become. And the tip of the plunger 91 of the tensioner 9 is pivotally connected to this tip side portion, and by this is pressed toward the slack side span 7b of the timing chain 7, an appropriate tension is applied. Can do.

  A chain housing chamber C for housing such a timing chain 7 is formed at one end of the engine 100 in the cylinder row direction as shown in FIGS. In the present embodiment, a chain housing chamber C is formed between an inner cover 11 attached over the cylinder block 1 from the cylinder head 2 and an outer cover 12 (shown only in FIG. 2) assembled thereto. ing. These inner cover 11 and outer cover 12 are chain cover members.

  The inner cover 11 is made of an alloy of iron or aluminum, and is disposed from the vicinity of the upper end of the cylinder head 2 to the vicinity of the lower end of the cylinder block 1, and is fastened at a plurality of locations (not shown). For example, a blow-by gas passage and an oil dropping passage are formed in the inner cover 11. The outer cover 12 is also made of an alloy of iron or aluminum, and is disposed so as to cover the inner cover 11 and fastened at a plurality of locations on the outer peripheral portion thereof.

  The tensioner 9 of the present embodiment is a well-known one, and a detailed description thereof is omitted. However, as shown in FIG. 3, the tensioner 9 is provided with a housing 90 that accommodates a plunger 91 and holds the plunger 91 so as to advance and retract. ing. The housing 90 is formed with a cylindrical cylinder portion 90a, and receives the hydraulic pressure supplied from the lubrication system of the engine 100 (not shown) to advance the plunger 91. In FIG. 3, the inner cover 11 is omitted, and the positional relationship among the cylinder block 1, the cylinder head 2, and the tensioner 9 is shown.

  By the way, in the engine 100 of the present embodiment, the crankshaft 4 undergoes rotational fluctuations due to intermittent combustion in the plurality of cylinders 1a, and this is caused by fluctuations in the tension of the timing chain 7 driven thereby. Thus, so-called string vibration (transverse vibration) occurs. That is, as schematically shown in FIG. 4, an “antinode” portion where the amplitude of the timing chain 7 is increased by resonance between the sprockets 4 a, 5 a, and 6 a and a “node” portion where the amplitude is reduced appear. .

  In the present embodiment, the lateral vibration is effectively suppressed by pressing the “belly” portion of the amplitude in the slack side span 7 b of the timing chain 7. In this way, the tension applied to the timing chain 7 may be small, and the mechanical loss can be reduced. In addition, the width of the timing chain 7 is increased to increase the strength of the timing chain 7, and the weight is increased. You can also avoid harmful effects.

-Chain tensioner mounting structure-
In order to press the “belly” portion of the amplitude of the timing chain 7 as described above, the tensioner 9 connected to the distal end side of the movable guide 8b is connected to the cylinder head 2 and the cylinder as shown in FIGS. It must be placed so as to straddle block 1. That is, in the housing 90 of the tensioner 9, the cylinder portion 90a is arranged so that the plunger 91 presses the distal end side of the movable guide 8b in the swinging direction, and the boss portions 90b and 90c are provided on the upper and lower sides, respectively. Yes.

  Specifically, as shown also in FIG. 5, a first boss portion 90 b (first fastening portion) is provided above the cylinder portion 90 a in the housing 90, and the fastening bolt 13 inserted into the through hole is The inner cover 11 is inserted into the through hole 11 a and fastened to the fastened portion 2 a of the cylinder head 2. That is, the male screw formed on the outer peripheral surface of the shaft portion of the fastening bolt 13 is screwed with the female screw formed on the inner peripheral surface of the bolt hole of the fastened portion 2a.

  A second boss portion 90c (second fastening portion) is provided below the cylinder portion 90a, and the fastening bolt 14 inserted into the through hole is fastened to the fastened portion 11b of the inner cover 11. It is like that. That is, as shown in FIG. 5, the fastened portion 11b of the inner cover 11 has a bolt hole formed in the bulged portion on the back side thereof, and a fastening bolt is formed on the female screw formed on the inner peripheral surface of the bolt hole. A male screw formed on the outer peripheral surface of the shaft portion 14 is screwed.

  Thus, the housing 90 of the tensioner 9 is fastened to the cylinder head 2 at the first boss portion 90b, while the second boss portion 90c is not the cylinder block 1 but the inner cover 11 (of the chain housing chamber C). As described below with reference to FIG. 6, even if the difference in thermal expansion between the cylinder head 2 and the cylinder block 1 is large, an excessive force is not easily applied to the housing 90 straddling both. ing.

  In other words, the cylinder head of an engine is generally provided with an exhaust manifold that has a high temperature, so that the amount of thermal expansion is larger than that of the cylinder block. Therefore, if the housing 90 of the tensioner 9 is fastened to the cylinder head 2 and the cylinder block 1 in the present embodiment, the housing 90 is caused by a difference in thermal expansion as schematically and exaggerated in FIG. Since it becomes slanting and an excessive force is applied to the boss portions 90b and 90c, the fastening bolts 13 and 14 are liable to be loosened, and the housing 90 may be cracked.

  On the other hand, in the present embodiment, the second boss portion 90c of the housing 90 is fastened to the inner cover 11 instead of the cylinder block 1, so that it is schematically and exaggerated in FIG. In addition, the inclination of the housing 90 due to the difference in thermal expansion with the cylinder head 2 is reduced, and the above-described problems are suppressed. This is because the inner cover 11 is disposed from the vicinity of the upper end of the cylinder head 2 to the vicinity of the lower end of the cylinder block 1 and is long in the vertical direction.

  As described above, the tensioner 9 according to the present embodiment is arranged on the cylinder head 2 at the first boss portion 90b when the housing 90 is disposed so as to straddle the cylinder head 2 and the cylinder block 1 of the engine 100. On the other hand, since the second boss portion 90c is fastened to the inner cover 11 constituting the chain housing chamber C, the first boss portion 90c is not affected even if the thermal expansion difference between the cylinder head 2 and the cylinder block 1 increases. And the unreasonable force concerning the 2nd boss | hub parts 90b and 90c becomes small. Therefore, loosening of the fastening bolts 13 and 14 can be suppressed, and there is less fear of causing a crack in the housing 90.

-Other embodiments-
The present invention is not limited to the description of the embodiment described above. For example, in the above-described embodiment, the tensioner 9 of the automobile engine 100 has been described. However, the present invention is not limited to this. The present invention is also applicable to the tensioner to be used.

  In addition, the fastening bolt 13 of the first boss portion 90b of the tensioner 9 does not need to be fastened to the cylinder head 2 through the inner cover 11 as in the above-described embodiment, and the inner cover 11 is avoided and the cylinder is avoided. It may be fastened to the head 2.

  Even if the tensioner is disposed so as to straddle the cylinder head and the cylinder block of the engine, the present invention can suppress a problem due to a difference in thermal expansion, and is useful when applied to, for example, an automobile engine. is there.

DESCRIPTION OF SYMBOLS 1 Cylinder block 2 Cylinder head 5,6 Valve shaft camshaft 7 Timing chain 8b Movable guide 9 Tensioner 90 Housing 90b 1st boss | hub part (1st fastening site)
90c 2nd boss | hub part (2nd fastening site | part)
91 Plunger 11 Inner cover (chain cover member)
100 engine

Claims (1)

A tensioner for applying a predetermined tension to a timing chain that drives a camshaft of an engine valve system,
A plunger that presses the movable guide against the loose side of the timing chain, and a housing that holds the plunger movably toward the movable guide;
The housing is fastened to the cylinder head of the engine at the first fastening portion, and is fastened to a chain cover member attached across the cylinder block from the cylinder head at the second fastening portion. Tensioner characterized by.

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