Chain tension adjustment device

Abstract

Reduce the tension in the chain. [Solution] The chain tension adjustment device 4 comprises a chain (third chain 33) stretched between a drive sprocket (crank sprocket 26) and a driven sprocket (balance sprocket 32), a first tensioner (first hydraulic tensioner 41) having a damping function that presses the slack side of the chain, and a second tensioner (second hydraulic tensioner 42) having a damping function that presses the tension side of the chain. The position where the first tensioner presses the slack side of the chain is closer to the driven sprocket than the center position C of the imaginary line connecting the centers of the drive sprocket and the driven sprocket, and the position where the second tensioner presses the tension side of the chain is closer to the drive sprocket than the center position of the imaginary line.

Description

Technical Field

[0005] , ,

[0001] The technology disclosed herein relates to a chain tension adjusting device.

Background Art

[0002] Patent Document 1 describes a conventional power transmission mechanism. This power transmission mechanism transmits power from the crankshaft of an internal combustion engine to a camshaft using a chain. In the power transmission mechanism, a chain tensioner is provided on the slack side of the chain hung between the sprocket of the camshaft and the sprocket of the crankshaft, and a chain guide is provided on the tension side. The chain tensioner applies tension to the slack side of the chain. The chain guide is movable, and by moving the chain guide during regular inspections, the timing deviation due to the elongation of the chain is corrected.

[0003] Patent Document 2 describes a conventional auxiliary machine drive device for an engine. This auxiliary machine drive device transmits the power of the crankshaft of the engine to an oil pump drive shaft. The auxiliary machine drive device has a first hydraulic tensioner disposed on the slack side of the chain and a second hydraulic tensioner disposed on the tension side. Both the first hydraulic tensioner and the second hydraulic tensioner are tensioners having a damping mechanism. The location where the first hydraulic tensioner presses the slack side of the chain and the location where the second hydraulic tensioner presses the tension side of the chain face each other in a substantially horizontal direction.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the conventional auxiliary drive system described in Patent Document 2, both the slack and tension sides of the chain are pressed by a hydraulic tensioner having a damping mechanism. This structure reduces the tension of the chain and thus the driving resistance of the chain in the conventional auxiliary drive system described in Patent Document 2. Reducing the driving resistance of the chain improves the fuel efficiency of the engine.

[0006] However, there is a need to further improve the fuel efficiency of the engine. Similarly, the power transmission system requires further reduction in the drive resistance of the chain.

[0007] The technology disclosed herein reduces chain tension. [Means for solving the problem]

[0008] The technology disclosed herein relates to a chain tension adjustment device. This chain tension adjustment device is A drive sprocket fixed to the drive shaft, A driven sprocket fixed to the driven shaft, An endless chain is stretched between the drive sprocket and the driven sprocket to transmit power from the drive sprocket to the driven sprocket, A first tensioner having a damping function is located on the slack side of the chain and presses against the slack side of the chain, The system includes a second tensioner having a damping function, which is located on the tension side of the chain and presses against the tension side of the chain, The position at which the first tensioner presses the slack side of the chain is closer to the driven sprocket than the center of the imaginary line connecting the centers of the drive sprocket and the driven sprocket. The position where the second tensioner presses against the tensioned side of the chain is closer to the drive sprocket than the center position of the imaginary line.

[0009] The chain tension adjustment device comprises a first tensioner and a second tensioner. The first tensioner is located on the slack side of the chain, which is stretched between the drive sprocket and the driven sprocket, and presses against the slack side. The second tensioner is located on the tension side of the chain and presses against the tension side. Since both the slack side and the tension side of the chain are pressed by tensioners with damping functions, the chain tension adjustment device can reduce the tension of the chain.

[0010] In the chain tension adjustment device described above, the position where the first tensioner presses the slack side of the chain is closer to the driven sprocket than the center of the imaginary line connecting the centers of the drive sprocket and the driven sprocket. This position is close to the position where the chain engages with the driven sprocket on the slack side. At the position where the chain engages with the sprocket, the flapping of the chain due to torque fluctuations of the drive shaft is large. The first tensioner, which has a damping function, can effectively suppress the large chain flapping on the slack side.

[0011] Furthermore, in the aforementioned chain tension adjustment device, the position where the second tensioner presses the tensioned side of the chain is closer to the drive sprocket than the center position of the dashed line. This position is close to the position where the chain engages with the drive sprocket on the tensioned side, and is a position where the chain flapping is large. The second tensioner, which has a damping function, can effectively suppress the large chain flapping on the tensioned side.

[0012] In the chain tension adjustment device described above, the pressing positions of the first tensioner and the second tensioner are optimized. Even if the pressing force on the chain by the first tensioner and the second tensioner is reduced, chain tension loss is suppressed. The chain tension adjustment device can further reduce the tension of the chain. The chain tension adjustment device can further reduce the driving resistance of the chain.

[0013] The first tensioner has a base end that is pivotably supported around a first pivot and has a first lever that is pressed against the slack side of the chain, and a first plunger that presses the tip of the first lever toward the slack side of the chain. The second tensioner has a base end that is pivotably supported about a second pivot and has a second lever that is pressed against the tension side of the chain, and a second plunger that presses the tip of the second lever toward the tension side of the chain. The first lever and the second lever may have the same shape, and the first pivot and the second pivot may be positioned on the slack side and the tension side of the chain, respectively, such that they are point-symmetrical with respect to the center of the imaginary line.

[0014] By reversing the orientation of two levers of the same shape and positioning them on the slack and tension sides of the chain, respectively, the first lever of the first tensioner and the second lever of the second tensioner are formed. The first tensioner and the second tensioner can share at least some of their components.

[0015] Furthermore, by positioning the first lever and the second lever so that the first and second pivots are point-symmetric with respect to the center of the imaginary line, the pressing positions of the first tensioner and the second tensioner are optimized, respectively.

[0016] The drive shaft may be the engine's crankshaft, and the driven shaft may be the balancer shaft.

[0017] Power transmission systems, including those involving a chain wrapped around the engine's crankshaft, are prone to torque fluctuations. The aforementioned chain tension adjustment device can reduce the driving resistance of the chain in the engine's power transmission system, thereby improving the engine's fuel efficiency.

[0018] The cylinder block of the engine comprises an upper block located above the crankshaft and a lower block located below the crankshaft. The first tensioner and the second tensioner may be fixed to the lower block.

[0019] Since both the first tensioner and the second tensioner are fixed to the lower block, the attachment structure of the chain tensioning device to the engine is simple.

[0020] The balancer shaft is located below the lower end of the lower block. The first lever is in a direction in which the first pivot is located upward and the pressing position of the first plunger is located downward, and at least a part of the first plunger is located below the lower end of the lower block. The second lever may be in a direction in which the second pivot is located downward and the pressing position of the second plunger is located upward, and the second plunger is located above the lower end of the lower block.

[0021] The driven sprocket fixed to the balancer shaft is located below the lower end of the lower block. Since at least a part of the first plunger is located below the lower end of the lower block, the first plunger can press an optimal position near the meshing position of the driven sprocket on the slack side of the chain. The fact that at least a part of the first plunger is located below the lower end of the lower block is advantageous for reducing the tension of the chain by optimizing the pressing position of the first plunger.

[0022] The lower block has an oil passage for supplying hydraulic oil to the first plunger. The first tensioner may have a communication passage that extends obliquely downward from the oil passage toward the pressure chamber of the first plunger and communicates the oil passage with the pressure chamber.

[0023] Since at least a part of the first plunger is located below the lower end of the lower block, it is difficult to directly connect the oil passage formed in the lower block to the pressure chamber of the first plunger. A communication passage for hydraulic oil that connects the oil passage and the pressure chamber is required.

[0024] The first tensioner has a connecting passage. The connecting passage extends diagonally downward from the oil passage toward the pressure chamber of the first plunger. Even if at least a portion of the first plunger is located below the lower end of the lower block, hydraulic fluid is supplied from the oil passage to the pressure chamber of the first plunger through the diagonally downward connecting passage.

[0025] The first and second fixing portions for fixing the first tensioner to the lower block may be located above the first plunger, on the first and second sides, with the oil passage in between.

[0026] Since at least a portion of the first plunger is located below the lower end of the lower block, the first or second fixing part cannot be located below the first plunger. The first and second fixing parts are located above the first plunger and fix the first tensioner to the lower block.

[0027] Furthermore, the first and second fixed parts are located on the first and second sides of the oil passage. The oil passage can supply hydraulic fluid to the pressure chamber of the first plunger without interfering with the first and second fixed parts.

[0028] The first fixing portion and the second fixing portion that fix the first tensioner to the lower block are located above the first plunger, The third fixing portion for fixing the second tensioner to the lower block may be located above the second plunger, and the fourth fixing portion for fixing the second tensioner to the lower block may be located below the second plunger.

[0029] As mentioned above, since at least a portion of the first plunger is located below the lower end of the lower block, the first or second fixing part cannot be located below the first plunger. The first and second fixing parts fix the first tensioner to the lower block above the first plunger.

[0030] The second plunger is positioned above the lower end of the lower block. The third and fourth fixing parts secure the second tensioner to the lower block above and below the second plunger. The third and fourth fixing parts can stably secure the second tensioner. [Effects of the Invention]

[0031] The aforementioned chain tension adjustment device can reduce the tension of the chain. [Brief explanation of the drawing]

[0032] [Figure 1] Figure 1 shows an engine to which a chain tension adjustment device has been applied. [Figure 2] Figure 2 shows a magnified view of the chain tension adjustment device. [Figure 3] Figure 3 shows the structure for supplying hydraulic fluid to the first hydraulic tensioner. [Figure 4] Figure 4 is a diagram comparing the chain tension of a conventional chain tension adjustment device and the chain tension adjustment device disclosed herein. [Modes for carrying out the invention]

[0033] The following describes an embodiment of the chain tension adjustment device with reference to the drawings. The chain tension adjustment device described here is illustrative.

[0034] (Overall engine configuration) Figure 1 shows an engine 1 equipped with a chain tension adjustment device 4. Engine 1 is mounted in an automobile.

[0035] In Figure 1, the engine 1 comprises a cylinder head 11 and a cylinder block 12. A cylinder head cover is mounted on top of the cylinder head 11, and an oil pan 13 is mounted below the cylinder block 12 (see Figure 3). The cylinder block 12 includes an upper block 121 and a lower block 122. The upper block 121 is located above the crankshaft 21, and the lower block 122 is located below the crankshaft 21. The cylinder block 12 rotatably supports the crankshaft 21. The cylinder head 11 rotatably supports the intake camshaft 22 and the exhaust camshaft 23. The intake camshaft 22 and the exhaust camshaft 23 are spaced apart from each other in the width direction of the engine 1 (i.e., the left-right direction in Figure 1).

[0036] An intake cam sprocket 24 is mounted coaxially with the intake camshaft 22. An exhaust cam sprocket 25 is mounted coaxially with the exhaust camshaft 23. A crank sprocket 26 is mounted coaxially with the crankshaft 21. The crank sprocket 26 is located between the intake camshaft 22 and the exhaust camshaft 23 in the width direction of the engine 1.

[0037] The upper block 121 rotatably supports the pump sprocket 27 that drives the fuel pump. The pump sprocket 27 is located vertically between the intake cam sprocket 24 and the exhaust cam sprocket 25 and the crank sprocket 26, and horizontally on the intake camshaft 22 side of the engine 1.

[0038] A first chain 28 is stretched between the intake cam sprocket 24, the exhaust cam sprocket 25, and the pump sprocket 27. A second chain 29 is stretched between the pump sprocket 27 and the crank sprocket 26. The first chain 28 and the second chain 29 are both well-known endless chains having multiple rollers that mesh with the teeth of the sprockets.

[0039] When engine 1 is running and the crankshaft 21 rotates, its driving force is transmitted to the pump sprocket 27 via the crank sprocket 26 and the second chain 29. From the pump sprocket 27, the driving force of the crankshaft 21 is transmitted to the intake camshaft sprocket 24 and the exhaust camshaft sprocket 25 via the first chain 28. As the fuel pump is driven, the intake camshaft 22 and the exhaust camshaft 23 rotate in sync with the rotation of the crankshaft 21 (see arrows in Figure 1).

[0040] On the tensioned side of the first chain 28, that is, on the left side of the paper in Figure 1, guides 210 and 211 are positioned vertically. Guide 210 is fixed to the cylinder head 11, and guide 211 is fixed to the upper block 121. Guides 210 and 211 guide the first chain 28 and suppress the flapping of the first chain 28.

[0041] A tensioner 212 is located on the slack side of the first chain 28, that is, on the right side of the paper in Figure 1. The tensioner 212 applies tension to the first chain 28. The tensioner 212 is a hydraulic tensioner with a damping function. The tensioner 212 presses against the first chain 28 via a first tension arm 213. The first tension arm 213 is curved to follow the slack side of the first chain 28. The lower end of the first tension arm 213 is pivotally supported on the upper block 121. The plunger of the tensioner 212 pushes the upper end of the first tension arm 213 toward the slack side of the first chain 28.

[0042] A guide 214 is located on the tensioned side of the second chain 29, that is, on the lower left side of the page in Figure 1. The guide 214 is fixed to the upper block 121. The guide 214 guides the second chain 29 and suppresses the flapping of the second chain 29.

[0043] A tensioner 215 is located on the slack side of the second chain 29, that is, on the upper right side of the paper in Figure 1. The tensioner 215 applies tension to the second chain 29. The tensioner 215 is a hydraulic tensioner with a damping function. The tensioner 215 presses against the second chain 29 via the second tension arm 216. The second tension arm 216 is curved to follow the slack side of the second chain 29. The upper end of the second tension arm 216 is pivotally supported by the upper block 121. Note that the pivot of the first tension arm 213 and the pivot of the second tension arm 216 are common. The plunger of the tensioner 215 pushes the lower end of the second tension arm 216 toward the slack side of the second chain 29.

[0044] A balancer shaft 31 is positioned below the crankshaft 21. The balancer shaft 31 is positioned below the lower end of the lower block 122 and parallel to the crankshaft 21.

[0045] A balancer sprocket 32 ​​is mounted coaxially with the balancer shaft 31. The balancer sprocket 32 ​​has the same number of teeth as the crank sprocket 26.

[0046] A third chain 33 is stretched between the crank sprocket 26 and the balancer sprocket 32. The third chain 33, like the first chain 28 and the second chain 29, is a well-known endless chain having multiple rollers that mesh with the teeth of the sprocket. The third chain 33 transmits power from the crank sprocket 26 to the balancer sprocket 32. When the crankshaft 21 rotates, the balancer shaft 31 rotates in the same direction as the crankshaft 21 and at the same speed as the crankshaft 21. The rotation of the balancer shaft 31 suppresses vibrations of the engine 1. The crankshaft 21 is an example of a drive shaft, and the balancer shaft 31 is an example of a driven shaft. Also, the crank sprocket 26 is an example of a drive sprocket, and the balancer sprocket 32 ​​is an example of a driven sprocket.

[0047] (Configuration of the chain tension adjustment device) Figure 2 shows a magnified view of the chain tension adjustment device 4. The chain tension adjustment device 4 adjusts the tension of the third chain 33, which is stretched between the crank sprocket 26 and the balancer sprocket 32. The chain tension adjustment device 4 comprises a first hydraulic tensioner 41 and a second hydraulic tensioner 42.

[0048] The first hydraulic tensioner 41 is located on the slack side of the third chain 33. The slack side of the third chain 33 is the left side of the paper in Figure 2. The first hydraulic tensioner 41 has a curved first lever 411. The first lever 411 contacts the slack side of the third chain 33 and presses against it. The base end of the first lever 411 is pivotally supported by a support portion 412 of the first hydraulic tensioner 41. The support portion 412 supports the base end of the first lever 411 so that it can swing around a first pivot 4112. The first lever 411 is positioned so that the base end pivotally supported by the support portion 412 is facing upwards, and the tip that is pressed by the first plunger 413 (described later) is facing downwards.

[0049] The first hydraulic tensioner 41 has a first plunger 413. The first plunger 413 protrudes from the end of the case 414. The first plunger 413 pushes the tip of the first lever 411 toward the slack side of the third chain 33, as shown by the white arrow in Figure 2. The first plunger 413 is located below the support 412. A portion of the first plunger 413 is located below the lower end of the lower block 122, which is shown by the dashed line in Figure 2. The tip of the first lever 411 is also located below the lower end of the lower block 122. The base end of the first lever 411 is located above the lower end of the lower block 122.

[0050] The first hydraulic tensioner 41 has a bracket 415. The bracket 415 connects the support portion 412 and the case 414 of the first plunger 413 to each other. The first fixing portion 416 and the second fixing portion 417 fix the bracket 415 to the lower block 122. Both the first fixing portion 416 and the second fixing portion 417 are located above the first plunger 413. Both the first fixing portion 416 and the second fixing portion 417 are located above the lower end of the lower block 122. The detailed structure of the first hydraulic tensioner 41 will be described later.

[0051] The second hydraulic tensioner 42 is located on the tensioned side of the third chain 33. The tensioned side of the third chain 33 is the right side of the paper in Figure 2. The second hydraulic tensioner 42 has a curved second lever 421. The second lever 421 strikes the tensioned side of the third chain 33 and presses against it. The base end of the second lever 421 is pivotally supported by a support portion 422 of the second hydraulic tensioner 42. The support portion 422 supports the base end of the second lever 421 so that it can swing around a second pivot 429. The second lever 421 is positioned such that the base end pivotally supported by the support portion 422 is downward, and the tip that is pressed by the second plunger 423 (described later) is upward. The base end of the second lever 421 is located below the lower end of the lower block 122. The tip of the second lever 421 is located above the lower end of the lower block 122.

[0052] The second hydraulic tensioner 42 has a second plunger 423. The second plunger 423 protrudes from the end of the case 424. The second plunger 423 pushes the tip of the second lever 421 toward the tension side of the third chain 33, as shown by the white arrow in Figure 2. The second plunger 423 is located above the support portion 422. The second plunger 423 is located above the lower end of the lower block.

[0053] The second hydraulic tensioner 42 has a bracket 425. The bracket 425 connects the support portion 422 and the case 424 of the second plunger 423 to each other. The third fixing portion 426 and the fourth fixing portion 427 fix the bracket 425 to the lower block 122. The third fixing portion 426 is located above the second plunger 423, and the fourth fixing portion 427 is located below the second plunger 423.

[0054] Figure 3 shows a simplified internal structure of the first hydraulic tensioner 41. A pressure chamber 418 is formed inside the case 414. The pressure chamber 418 extends in a direction along the axis of the first plunger 413. The first plunger 413 is reciprocally fitted into the pressure chamber 418. A compression coil spring 419 housed in the case 414 pushes the first plunger 413 in a direction protruding from the tip of the case 414, that is, to the right in Figure 3. The biasing force of the compression coil spring 419 pushes the tip of the first lever 411 toward the slack side of the third chain 33.

[0055] Case 414 has a connecting passage. The connecting passage supplies hydraulic fluid into the pressure chamber 418. The pressure chamber 418 is filled with hydraulic fluid. When the first plunger 413 is pushed by the third chain 33 via the first lever 411, the hydraulic fluid in the pressure chamber 418 is discharged from the pressure chamber 418 through a groove (not shown). The discharge of hydraulic fluid generates a damping force on the first plunger 413.

[0056] The connecting passage includes a first connecting passage 4110 and a second connecting passage 4111. The first connecting passage 4110 is coaxial with the pressure chamber 418 and communicates with the rear end of the pressure chamber 418. Parts of the pressure chamber 418 and the first connecting passage 4110 are located below the lower block 122. The pressure chamber 418 and the first connecting passage 4110 cannot be directly connected to the oil passage 123 formed in the lower block 122. The second connecting passage 4111 connects the oil passage 123 and the first connecting passage 4110. As shown in the cross-sectional view AA of Figure 3, the second connecting passage 4111 extends diagonally downward from the oil passage 123 toward the first connecting passage 4110. That is, the upper end of the second connecting passage 4111 is located above the lower end of the lower block 122, and the lower end of the second connecting passage 4111 is located below the lower end of the lower block 122. Note that the bolts of the first fixing part 416 are not shown in the AA cross-sectional view.

[0057] The oil passage 123 formed in the lower block 122 opens to the mounting surface 124 and recesses from the mounting surface 124, as shown in the cross-sectional view AA of Figure 3. The mounting surface 124 is the surface to which the bracket 415 of the first hydraulic tensioner 41 is fixed. When the first hydraulic tensioner 41 is fixed to the mounting surface 124, the oil passage 123 is blocked.

[0058] The oil passage 123 extends along the mounting surface 124. The oil passage 123 is inclined with respect to the vertical and passes between the horizontally aligned first fixing part 416 and second fixing part 417 to the vicinity of the rear end of the case 414. When the first hydraulic tensioner 41 is fixed to the mounting surface 124, the second communication passage 4111 of the first hydraulic tensioner 41 communicates with the rear end of the oil passage 123. As shown by dashed or solid arrows in Figure 3, hydraulic fluid is supplied from the oil passage 123 to the pressure chamber 418 through the second communication passage 4111 and the first communication passage 4110.

[0059] Furthermore, the oil passage 125 that supplies hydraulic fluid to the pressure chamber of the second hydraulic tensioner 42 is formed in the lower block 122, as shown in Figure 2. The second plunger 423 and case 424 of the second hydraulic tensioner 42 are located above the lower end of the lower block 122. The oil passage 125 formed in the lower block 122 is connected directly to the pressure chamber of the second hydraulic tensioner 42 or the first communication passage without going through the diagonally extending second communication passage 4111 mentioned above.

[0060] (Effects and effects of the chain tension adjustment device) The first hydraulic tensioner 41 of the chain tension adjustment device 4 is located on the slack side of the third chain 33, which is stretched between the crank sprocket 26 (a drive sprocket) and the balance sprocket 32 ​​(a driven sprocket), and presses against the slack side. The second hydraulic tensioner 42 is located on the tension side of the third chain 33 and presses against the tension side. Since the tensioners, which have a damping function, press against both the slack side and the tension side of the third chain 33, the chain tension adjustment device 4 can reduce the tension of the third chain 33.

[0061] The first lever 411 of the first hydraulic tensioner 41 and the second lever 421 of the second hydraulic tensioner 42 have the same shape. The curve radius of the first lever 411 and the second lever 421 are set to be as large as possible. A larger curve radius reduces the driving resistance of the third chain 33. Reducing driving resistance is advantageous for improving the fuel efficiency of the engine 1.

[0062] Furthermore, in a power transmission system including a crank sprocket 26, a balance sprocket 32, and a third chain 33, the number of teeth on the sprocket and the free span of the chain are set from the viewpoint of system reliability, reduction of driving resistance, and reduction of NVH. The free span is the area shown by shading in Figure 2, where the chain does not engage with the sprocket and does not come into contact with the tensioner lever.

[0063] In the chain tension adjustment device 4, the radius of the lever curvature, the number of teeth on the sprocket, and the free span of the chain are set as described above, and the position where the first hydraulic tensioner 41 presses the slack side of the third chain 33, and the position where the second hydraulic tensioner 42 presses the tension side of the third chain are optimized. Specifically, the position where the first hydraulic tensioner 41 presses the slack side of the third chain 33 is closer to the balancer sprocket 32 ​​than the center position C of the imaginary line connecting the centers of the crank sprocket 26 and the balancer sprocket 32 ​​(see the dashed line in Figure 2). This position is close to the position where the third chain 33 engages with the balancer sprocket 32 ​​on the slack side. At the position where the chain engages with the sprocket, there is significant chain flapping due to torque fluctuations of the crankshaft 21. The first hydraulic tensioner 41, which has a damping function, can effectively suppress the flapping of the third chain 33 at a position where the flapping of the slack side of the third chain 33 becomes large.

[0064] Furthermore, the position where the second hydraulic tensioner 42 presses the tensioned side of the third chain 33 is closer to the crank sprocket 26 than the center position C of the imaginary line. This position is close to the position where the third chain 33 engages with the crank sprocket 26 on the tensioned side, and is a position where the flapping of the third chain 33 is large. The second hydraulic tensioner 42, which has a damping function, can effectively suppress the flapping of the third chain 33 at the position where the flapping of the tensioned side of the third chain 33 is large.

[0065] The chain tension adjustment device 4 optimizes the pressing positions of the first hydraulic tensioner 41 and the second hydraulic tensioner 42, respectively. Because the pressing positions of the first hydraulic tensioner 41 and the second hydraulic tensioner 42 are optimized, even if the pressing force of the first hydraulic tensioner 41 and the second hydraulic tensioner 42 is reduced, tension loss in the third chain 33 is suppressed. The chain tension adjustment device 4 can reduce the tension of the third chain 33.

[0066] Figure 4 compares the chain tension in a power transmission system to which the chain tension adjustment device 4 is applied (see solid line) with the chain tension in a power transmission system to which a conventional chain tension adjustment device is applied (see dashed line). The conventional chain tension adjustment device is, for example, the chain tension adjustment device described in Patent Document 2. In a power transmission system to which the chain tension adjustment device 4 is applied, the chain tension is reduced by about 15% compared to a power transmission system to which a conventional chain tension adjustment device is applied. By reducing the tension of the third chain 33, the driving resistance of the third chain 33 is reduced. By reducing the driving resistance of the third chain 33, the chain tension adjustment device 4 can improve the fuel efficiency of the engine 1.

[0067] Furthermore, as mentioned above, the first lever 411 of the first hydraulic tensioner 41 and the second lever 421 of the second hydraulic tensioner 42 have the same shape. The two levers, having the same shape, can be reversed so that they are positioned on the slack side and the tension side of the third chain 33, respectively. The commonality of the first lever 411 of the first hydraulic tensioner 41 and the second lever 421 of the second hydraulic tensioner 42 reduces the manufacturing cost of the chain tension adjustment device 4.

[0068] Furthermore, since the first lever 411 of the first hydraulic tensioner 41 and the second lever 421 of the second hydraulic tensioner 42 have the same shape, as shown in Figure 2, the first pivot 4112 of the first lever 411 and the second pivot 429 of the second lever 421 are located on the slack side and tension side of the third chain 33, respectively, so as to the center position C of the imaginary line (see the dotted line in Figure 2). The point-symmetrical arrangement of the first lever 411 and the second lever 421 optimizes the pressing positions of the first hydraulic tensioner 41 and the second hydraulic tensioner 42, respectively.

[0069] The first hydraulic tensioner 41 and the second hydraulic tensioner 42, which are arranged so as to be point-symmetrical with respect to the first lever 411 and the second lever 421, are both fixed to the lower block 122. The mounting structure of the chain tension adjustment device 4 to the engine 1 is simple.

[0070] More specifically, the second lever 421 is oriented such that the second pivot 429 is at the bottom and the pressing position of the second plunger 423 is at the top, and the second plunger 423 is positioned above the lower end of the lower block 122.

[0071] The third fixing part 426, which secures the second hydraulic tensioner 42 to the lower block 122, is located above the second plunger 423, and the fourth fixing part 427, which secures the second hydraulic tensioner 42 to the lower block 122, is located below the second plunger 423. The third fixing part 426 and the fourth fixing part 427 can stably secure the second hydraulic tensioner 42.

[0072] In contrast, the first lever 411 is oriented such that the first pivot 4112 is positioned above and the pressing position of the first plunger 413 is positioned below, and at least a portion of the first plunger 413 is positioned below the lower end of the lower block 122.

[0073] By positioning at least a portion of the first plunger 413 below the lower end of the lower block 122, the first plunger 413 can press an optimal position near the engagement point of the balancer sprocket 32 ​​on the slack side of the third chain 33.

[0074] On the other hand, even if we were to invert the second hydraulic tensioner 42 and use it as the first hydraulic tensioner 41, the third fixing portion 426 of the second hydraulic tensioner 42 would be located below the lower end of the lower block 122, as shown by the dashed line in Figure 2. The third fixing portion 426 cannot be fixed to the lower block 122.

[0075] Therefore, the first fixing portion 416 and the second fixing portion 417 of the first hydraulic tensioner 41 are both located above the first plunger 413. The first fixing portion 416 and the second fixing portion 417 can stably fix the first hydraulic tensioner 41 to the lower block 122.

[0076] Furthermore, since the first fixing part 416 and the second fixing part 417, located above the first plunger 413, fix the first hydraulic tensioner 41 to the lower block 122, it is not necessary to increase the height H of the lower block 122 in order to mount the first hydraulic tensioner 41. The overall height of the engine 1 can be kept low.

[0077] Furthermore, in the first hydraulic tensioner 41, since a portion of the first plunger 413 is located below the lower end of the lower block 122, the oil passage 123 formed in the lower block 122 cannot be directly connected to the pressure chamber 418 of the first plunger 413.

[0078] As shown in Figure 3, the second communication passage 4111 of the first hydraulic tensioner 41 extends diagonally downward from the oil passage 123 toward the pressure chamber 418. The first communication passage 4110 and the second communication passage 4111 of the first hydraulic tensioner 41 can supply hydraulic fluid from the oil passage 123 of the lower block 122 to the pressure chamber 418 of the first plunger 413.

[0079] Furthermore, the oil passage 123 formed in the lower block 122 is located between the first fixed part 416 and the second fixed part 417 of the first hydraulic tensioner 41. The oil passage 123 can supply hydraulic fluid to the pressure chamber 418 of the first plunger 413 without interfering with the first fixed part 416 and the second fixed part 417.

[0080] (modified version) Furthermore, the chain tension adjustment device 4 is not limited to application to a power transmission system including a crank sprocket 26, a balancer sprocket 32, and a third chain 33. The chain tension adjustment device 4 may also be applied to a power transmission system including, for example, a crank sprocket 26, a pump sprocket 27, and a second chain 29. [Explanation of symbols]

[0081] 1 Engine 12 Cylinder Block 121 Upper Block 122 Lower Block 123 Oil road 21 Crankshaft (drive shaft) 26 Crank Sprocket (Drive Sprocket) 31. Balancer shaft (driven shaft) 32 Balanced sprocket (driven sprocket) 33 Third Chain 4. Chain tension adjustment device 41. First hydraulic tensioner 411 First Lever 413 First Plunger 416 1st fixed part 417 Second fixed part 418 Pressure Chamber 4110 1st communication passage 4111 2nd communication passage 4112 First Axis 42. Second hydraulic tensioner 421 Second Lever 423 Second Plunger 426 3rd fixed part 427 4th fixed part 429 Second Axis C center position

Claims

1. A drive sprocket fixed to the drive shaft, A driven sprocket fixed to the driven shaft, An endless chain is stretched between the drive sprocket and the driven sprocket to transmit power from the drive sprocket to the driven sprocket, A first tensioner having a damping function is located on the slack side of the chain and presses against the slack side of the chain, The system includes a second tensioner having a damping function, which is located on the tension side of the chain and presses against the tension side of the chain, The position at which the first tensioner presses the slack side of the chain is closer to the driven sprocket than the center of the imaginary line connecting the centers of the drive sprocket and the driven sprocket. The position where the second tensioner presses against the tension side of the chain is closer to the drive sprocket than the center position of the imaginary line. Chain tension adjustment device.

2. In the chain tension adjustment device according to claim 1, The first tensioner has a base end that is pivotably supported about a first pivot and has a first lever that is pressed against the slack side of the chain, and a first plunger that presses the tip of the first lever toward the slack side of the chain. The second tensioner has a base end that is pivotably supported around a second pivot and a second lever that is pressed against the tension side of the chain, and a second plunger that presses the tip of the second lever toward the tension side of the chain. The first lever and the second lever are of the same shape, and the first pivot and the second pivot are positioned on the slack side and the tension side of the chain, respectively, such that they are point-symmetrical with respect to the center of the imaginary line. Chain tension adjustment device.

3. In the chain tension adjustment device according to claim 2, The drive shaft is the engine's crankshaft, and the driven shaft is the balancer shaft. Chain tension adjustment device.

4. In the chain tension adjustment device according to claim 3, The cylinder block of the engine comprises an upper block located above the crankshaft and a lower block located below the crankshaft. The first tensioner and the second tensioner are fixed to the lower block. Chain tension adjustment device.

5. In the chain tension adjustment device according to claim 4, The balancer shaft is located below the lower end of the lower block. The first lever is oriented such that the first pivot is positioned upward and the pressing position of the first plunger is positioned downward, and at least a portion of the first plunger is positioned below the lower end of the lower block. The second lever is oriented such that the second pivot is positioned downwards and the pressing position of the second plunger is positioned upwards, and the second plunger is positioned above the lower end of the lower block. Chain tension adjustment device.

6. In the chain tension adjustment device according to claim 5, The lower block has an oil passage for supplying hydraulic fluid to the first plunger, The first tensioner extends diagonally downward from the oil passage toward the pressure chamber of the first plunger and has a communication passage that connects the oil passage and the pressure chamber. Chain tension adjustment device.

7. In the chain tension adjustment device according to claim 6, The first fixing portion and the second fixing portion that fix the first tensioner to the lower block are located above the first plunger, on the first and second sides with the oil passage in between, Chain tension adjustment device.

8. In the chain tension adjustment device according to claim 5, The first fixing portion and the second fixing portion that fix the first tensioner to the lower block are located above the first plunger, The third fixing portion for fixing the second tensioner to the lower block is located above the second plunger, and the fourth fixing portion for fixing the second tensioner to the lower block is located below the second plunger. Chain tension adjustment device.

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