JP7495304B2 - Auxiliary belt tensioner unit - Google Patents

Description

This invention relates primarily to an accessory belt tensioner unit used to maintain tension in the belt that drives engine accessories such as an alternator or water pump.

Automobile accessories, such as alternators, car air conditioners, and water pumps, have their rotating shafts connected to the engine crankshaft by an accessory belt and are driven via the accessory belt. To keep the tension of this accessory belt within the appropriate range, an accessory belt tensioner unit is generally used.

A known accessory belt tensioner unit includes a swing arm supported to be swingable around a fulcrum shaft, a tension pulley supported by the swing arm so as to move integrally with the swing arm around the fulcrum shaft when the swing arm swings, a first pin and a second pin positioned so as not to move even when the swing arm swings, a spring attached to the swing arm and pressing the first pin so as to urge the swing arm in one swing direction by a reaction force received from the first pin, and a hydraulic damper attached to the swing arm so as to come into contact with the second pin and cushioning the swing of the swing arm in the opposite direction to the one swing direction, thereby placing emphasis on reducing the installation space of the accessory belt tensioner unit that applies tension to the accessory belt (Patent Document 1).

In the accessory belt tensioner unit of Patent Document 1, a hydraulic damper is used that has a cylinder provided on the swing arm so as to move integrally with the swing arm around the fulcrum axis when the swing arm swings, a piston slidably inserted into the cylinder and dividing the interior of the cylinder into a hydraulic chamber and a reservoir chamber, and a damper rod whose one end is connected to the piston and whose other end abuts against the second pin. The hydraulic damper and the spring are arranged on the same plane perpendicular to the fulcrum axis. Inside the swing arm, a sub-reservoir chamber is formed adjacent to the reservoir chamber in a direction perpendicular to the longitudinal direction of the cylinder, and a communication passage is formed that communicates between the sub-reservoir chamber and the reservoir chamber. The hydraulic damper is arranged at a position above the fulcrum axis. The sub-reservoir chamber is adjacent to the upper side of the hydraulic damper and protrudes upward. The communication passage penetrates in the vertical direction between the lower end of the sub-reservoir chamber and the reservoir chamber of the hydraulic damper. The hydraulic chamber and reservoir chamber are filled with hydraulic oil so that no air is present. The secondary reservoir chamber contains two layers of air and hydraulic oil, one above the other. Pressure changes in the cylinder caused by the movement of the piston are absorbed by the air layer in the secondary reservoir chamber.

JP 2019-44941 A

An accessory belt tensioner unit like that in Patent Document 1 must be positioned so that air in the secondary reservoir chamber does not reach the hydraulic chamber via the communication passage and the reservoir chamber of the hydraulic damper, even if the swing arm has an inclination angle relative to the horizontal due to the mounting angle of the swing arm or the inclination during swing.

However, since the secondary reservoir chamber in Patent Document 1 protrudes upward adjacent to the hydraulic damper located above the fulcrum shaft, it is difficult to deepen the secondary reservoir chamber and increase the height difference between the oil level of the hydraulic oil and the communication passage when considering compact installation space. For this reason, the accessory belt tensioner unit in Patent Document 1 has room for improvement in that there is little freedom in the tilt angle allowed for the swing arm in preventing air from entering the hydraulic chamber from the secondary reservoir chamber.

The problem that this invention aims to solve is to provide a tensioner unit for an accessory belt that can prevent air in a secondary reservoir chamber formed in the swing arm from entering the hydraulic chamber of a hydraulic damper attached to the swing arm, even if the inclination angle of the swing arm supporting the tension pulley is large.

In order to achieve the above object, the present invention provides a method for manufacturing a hydraulic actuator comprising: a swing arm supported so as to be swingable about a fulcrum axis; a tension pulley supported by the swing arm so as to swing integrally with the swing arm about the fulcrum axis; a first pin and a second pin arranged so as not to move relative to the swing arm swinging about the fulcrum axis; a spring attached to the swing arm and pressing the first pin so as to urge the swing arm in one swing direction by a reaction force received from the first pin; and a hydraulic damper attached to the swing arm so as to come into contact with the second pin and cushioning the swing of the swing arm in the opposite direction to the one swing direction, and the hydraulic damper is arranged to move the swing arm so as to move integrally with the swing arm about the fulcrum axis. A tensioner unit for an accessory belt has a cylinder provided on a swing arm, a piston that divides the inside of the cylinder into a hydraulic chamber and a reservoir chamber, and a rod connected to the piston so as to abut against the second pin. A secondary reservoir chamber and a communication passage that communicates between the secondary reservoir chamber and the reservoir chamber are formed inside the swing arm, the hydraulic chamber and the reservoir chamber are filled with hydraulic oil, and the secondary reservoir chamber contains air and hydraulic oil in two layers, one above the other. The secondary reservoir chamber extends upward from a position located below the fulcrum axis, passing around the fulcrum axis, and the communication passage opens to the secondary reservoir chamber at a position below the fulcrum axis.

According to the above configuration, the secondary reservoir chamber extends upward from a portion located below the fulcrum axis of the swing arm, around the fulcrum axis, so that the periphery of the fulcrum axis can be utilized to form the secondary reservoir chamber, expanding the secondary reservoir chamber upward and storing more hydraulic oil to raise the oil level. The communication passage that connects the secondary reservoir chamber to the reservoir chamber of the hydraulic damper opens into the secondary reservoir chamber at a position below the fulcrum axis, increasing the height difference between the oil level and the communication passage. As a result, even if the tilt angle of the swing arm is large, air can be trapped in the upper region of the secondary reservoir chamber that is higher than the open position of the communication passage, making it difficult for air to enter the communication passage. Thus, according to the above configuration, even if the tilt angle of the swing arm is large, it is possible to prevent air from entering the hydraulic chamber from the secondary reservoir chamber.

Specifically, the auxiliary reservoir chamber is preferably adjacent to the hydraulic damper in the axial direction, and the communication passage passes between the auxiliary reservoir chamber and the reservoir chamber in the axial direction. In this way, it is possible to avoid arranging the hydraulic damper and the auxiliary reservoir chamber on the same plane perpendicular to the fulcrum axis, and to arrange a large auxiliary reservoir chamber around the fulcrum axis.

It is more preferable that the spring and the hydraulic damper are arranged on the same plane perpendicular to the fulcrum axis. In this way, it is possible to avoid arranging the hydraulic damper, the spring, and the secondary reservoir chamber on the same plane perpendicular to the fulcrum axis, and it is possible to easily arrange a large secondary reservoir chamber around the fulcrum axis.

It is also preferable that the auxiliary reservoir chamber is formed as an elongated hole having a hole width in the radial direction perpendicular to the axis of the fulcrum shaft and extending circumferentially longer than the hole width. In this way, the auxiliary reservoir chamber can be expanded upward without having to particularly expand the swing arm in the radial direction around the fulcrum shaft.

It is also preferable that the auxiliary reservoir chamber extends upward on both circumferential sides of the communication passage. In this way, air is stored in the upper regions on both circumferential sides of the auxiliary reservoir chamber, ensuring the amount of air required to absorb pressure changes in the cylinder caused by the movement of the piston, while raising the oil level of the hydraulic oil, thereby increasing the height difference between the oil level and the communication passage.

More preferably, the communication passage is open at a position spaced apart from the upper inner wall surface of the auxiliary reservoir chamber. In this way, even if air floating in the hydraulic oil moves along the upper inner wall surface of the auxiliary reservoir chamber when the swing arm swings, it is less likely to enter the communication passage.

As described above, by adopting the above configuration, the present invention can provide a tensioner unit for an accessory belt that can prevent air in the secondary reservoir chamber formed in the swing arm from entering the hydraulic chamber of the hydraulic damper attached to the swing arm, even if the inclination angle of the swing arm supporting the tension pulley is large.

FIG. 1 is a front view showing an accessory belt tensioner unit according to an embodiment of the present invention; FIG. 2 is a front view showing a belt transmission device having the accessory belt tensioner unit of FIG. 1; 2 is a bottom view of the accessory belt tensioner unit of FIG. 1 . 4 is a cross-sectional view taken along line IV-IV in FIG. FIG. 2 is an exploded perspective view showing the periphery of a fulcrum shaft of the accessory belt tensioner unit of FIG. 1; 6 is a cross-sectional view taken along line VI-VI of FIG. 1. A cross-sectional view taken along line VII-VII in FIG.

An embodiment of the present invention will be described with reference to the attached drawings.

Figure 2 shows an example of a belt transmission device using an accessory belt tensioner unit 1 according to an embodiment of the present invention. This belt transmission device has a crank pulley 3 attached to a crankshaft 2, a belt 4 wound around the crank pulley 3, an alternator 5 and a water pump 6 connected to the crank pulley 3 via the belt 4, and an accessory belt tensioner unit 1 that pushes the belt 4 to apply tension to the belt 4. Here, the alternator 5 and the water pump 6 are automobile accessories, and the belt 4 is an accessory belt that transmits the rotation of the crankshaft 2 to the accessories (alternator 5 and water pump 6).

As shown in Figures 1, 3, and 4, the accessory belt tensioner unit 1 includes a bracket 10 attached to the engine block 7, a swing arm 20 supported so as to be swingable relative to the bracket 10, and a tension pulley 30 attached to the swing arm 20.

As shown in FIG. 5, the bracket 10 has a number of through holes 11 formed therein. The through holes 11 are for fastening the bracket 10 to the engine block 7 with bolts 8 as shown in FIG. 3.

As shown in Figs. 1 and 4, the swing arm 20 is supported so as to be swingable around the fulcrum shaft 40. The tension pulley 30 is supported by the swing arm 20 so as to move integrally with the swing arm 20 around the fulcrum shaft 40 when the swing arm 20 swings. A belt 4 is wound around the outer circumference of the tension pulley 30.

Here, the direction along the axis of the fulcrum shaft 40 is referred to as the axial direction. The circumferential direction around the axis of the fulcrum shaft 40 is referred to as the circumferential direction, and the direction perpendicular to the axis is referred to as the radial direction. In addition, the side farther from the engine block 7 is referred to as the axial front side, and the side closer to the engine block 7 is referred to as the axial rear side.

As shown in Figures 4 and 5, the bracket 10 has a flat plate portion 12 perpendicular to the axial direction. The flat plate portion 12 has an axial hole 13 penetrating the flat plate portion 12 in the axial direction. The swing arm 20 has an axial hole 21 axially opposed to the axial hole 13. Cylindrical plain bearings 51 and 52 are fitted between the plate surface of the axial hole 13 of the flat plate portion 12, the fulcrum shaft 40, and the swing arm 20. The fulcrum shaft 40 is fixed to the bracket 10 by passing the plain bearings 51 and 52 through its shaft portion and pressing the shaft portion through the axial hole 21 into the axial hole 13. The plain bearings 51 and 52 support the swing arm 20 rotatably in the circumferential direction relative to the outer periphery of the fulcrum shaft 40 and the bracket 10, and support the axial load acting between the head of the fulcrum shaft 40, the bracket 10, and the swing arm 20.

The tension pulley 30 is disposed axially opposite the swing arm 20. The swing arm 20 is provided with a pulley shaft 22 that protrudes toward the tension pulley 30 from the surface facing the tension pulley 30. The pulley shaft 22 is located radially opposite the fulcrum shaft 40. A predetermined radial distance is provided between the fulcrum shaft 40 and the pulley shaft 22. The fulcrum shaft 40 passes through one end of the swing arm 20 in the longitudinal direction, and the pulley shaft 22 is disposed on the other end of the swing arm 20 in the longitudinal direction. In order to realize this opposing arrangement, the protruding direction of the pulley shaft 22 is set in the opposite direction (axial rear side) to the protruding direction of the fulcrum shaft 40 relative to the bracket 10 (axial front side).

The tension pulley 30 has a pulley 31 and a rolling bearing 32. The inner ring of the rolling bearing 32 is fitted onto the outer periphery of the pulley shaft 22. The outer ring of the rolling bearing 32 is integrated onto the inner periphery of the pulley 31. The inner ring of the rolling bearing 32 is fixed to the pulley shaft 22 with a bolt 33. The bolt 33 is screwed into a threaded hole formed in the pulley shaft 22. As a result, the rolling bearing 32 is in a state where it rotatably supports the tension pulley 30 with respect to the pulley shaft 22, and the tension pulley 30 is attached to the swing arm 20.

As shown in FIG. 6, a spring 60 and a hydraulic damper 70 are attached inside the swing arm 20.

A compression coil spring is used as the spring 60. A plurality of springs 60 are provided around the fulcrum shaft 40. A first recess 23 that accommodates the spring 60 is formed around the fulcrum shaft 40 of the swing arm 20. A plurality of first recesses 23 are formed at intervals in the circumferential direction. One end of the spring 60 accommodated in the first recess 23 is supported by the inner surface of the first recess 23, and the other end of the spring 60 presses the first pin 80 via a cylindrical cap 61.

The first pin 80 is positioned so as not to move even when the swing arm 20 swings. The cylindrical cap 61 is slidably supported by a guide sleeve 62 provided in the first recess 23. The first pin 80 is fixed to the bracket 10 by being pressed into a pin hole 14 formed in the bracket 10 as shown in FIG. 5. As shown in FIG. 6, the first pin 80 is provided in a state in which it protrudes axially forward from the axial front surface of the flat plate portion 12 of the bracket 10, and the protruding portion is inserted into the first recess 23.

A plurality of first pins 80 are provided corresponding to the plurality of springs 60. That is, the same number of first pins 80 are provided as the number of springs 60, and the first pins 80 are arranged at intervals in the circumferential direction around the fulcrum shaft 40. Here, the springs 60 urge the swing arm 20 in one swing direction by the reaction force received from the first pins 80. The circumferential direction on the side of the spring 60 as viewed from the first pin 80 (the left rotation direction in the figure) is the urging direction of the swing arm 20 by the spring 60, and the urging force of the spring 60 causes the tension pulley 30 in FIG. 2 to press the belt 4.

As shown in FIG. 6, the hydraulic damper 70 and the spring 60 are incorporated in the swing arm 20 so as to be positioned on the same plane perpendicular to the fulcrum shaft 40. The hydraulic damper 70 has a cylindrical cylinder 71 provided in the swing arm 20 so as to move integrally with the swing arm 20 around the fulcrum shaft 40 when the swing arm 20 swings, a piston 74 slidably inserted into the cylinder 71 and dividing the interior of the cylinder 71 into a hydraulic chamber 72 and a reservoir chamber 73, and a rod 75 one end of which is connected to the piston 74 and the other end of which abuts against a second pin 90. The second pin 90 is positioned so as not to move even when the swing arm 20 swings.

As shown in Figures 6 and 7, the swing arm 20 is formed with a second recess 24 that houses a hydraulic damper 70. Most of the second recess 24 is located on the same circumference as the first recess 23. The second recess 24 is formed like a hole that is closed at one end in a direction along a string that does not pass through the center of the circumference (string direction) and open at the other end. The closed end of the second recess 24 protrudes from the same circumference in the string direction. The hydraulic damper 70 is positioned below the fulcrum shaft 40. Here, the downward direction corresponds to the direction of gravity, and corresponds to the downward direction in Figures 1 and 2.

The cylinder 71 is formed in a cylindrical shape with one end open and the other end closed at its bottom. The cylinder 71 is fitted into the second recess 24 and fixed in the second recess 24 by a wear ring 76 that is press-fitted into the inner periphery of the second recess 24. The inner periphery of the wear ring 76 slidably supports the outer periphery of the rod 75. In addition, an oil seal 77 is incorporated in the second recess 24, through which the rod 75 slidably passes.

The piston 74 is housed in the cylinder 71 so that it can slide in the longitudinal direction of the cylinder 71. The piston 74 is provided with a check valve 78 that opens and closes the oil passage that connects the hydraulic chamber 72 and the reservoir chamber 73. The check valve 78 only allows the flow of hydraulic oil from the reservoir chamber 73 to the hydraulic chamber 72. A small leakage gap is formed between the sliding surfaces of the piston 74 and the cylinder 71. The hydraulic chamber 72 is fitted with a damper spring 79 that pushes the piston 74 in the direction that expands the volume of the hydraulic chamber 72.

The second pin 90 is fixed to the bracket 10. The bracket 10 has a pin hole 15 for pressing and fixing the second pin 90. The second recess 24 of the swing arm 20 has a through hole for inserting the second pin 90 into the second recess 24. The second pin 90 is provided in a state where it protrudes axially forward from the axial front surface of the flat plate portion 12 of the bracket 10, and the tip of the rod 75 abuts against the protruding portion.

As shown in FIG. 6, the hydraulic damper 70 and the second pin 90 are arranged so that the circumferential direction of the hydraulic damper 70 (left rotation direction in the figure) as viewed from the second pin 90 is the same as the circumferential direction of the spring 60 (left rotation direction in the figure) as viewed from the second pin 90. This allows the hydraulic damper 70 to cushion the swing of the swing arm 20 in the swing direction opposite the direction in which the spring 60 biases the swing arm 20 (the right rotation direction in FIG. 2 in which the tension pulley 30 moves away from the belt 4).

As shown in FIG. 1, the inclination angle θ of the swing arm 20 is the angle between a plane connecting the axis _O1 of the fulcrum shaft 40 and the rotation center _O2 of the tension pulley 30 and a horizontal plane. The plane corresponds to the cross section of line IV-IV in FIG. 1, the horizontal plane corresponds to the oil level of the hydraulic oil (Oil) in FIG. 1, and the inclination angle θ corresponds to the depression angle or elevation angle when looking at the rotation center _O2 from the axis _O1 . The inclination angle θ is determined by the combination of the mounting angle of the swing arm 20 and the angle at which the swing arm 20 rotates around the fulcrum shaft 40 during operation of the belt transmission device. The mounting angle of the swing arm 20 corresponds to the inclination angle θ when the swing arm 20 naturally settles when no tension is applied from the belt 4. The inclination angle θ of the swing arm 20 depicted in FIG. 1 corresponds to the mounting angle of the swing arm 20 in the belt transmission device shown in FIG. 2.

When the belt transmission device is in operation, if the tension in the belt 4 decreases, the urging force of the spring 60 (see Figure 6) causes the swing arm 20 to swing in the counterclockwise direction, absorbing the slack in the belt 4. At this time, the urging force of the damper spring 79 causes the piston 74 shown in Figures 6 and 7 to move in a direction that expands the volume of the hydraulic chamber 72. Also, the check valve 78 opens, allowing hydraulic oil to flow from the reservoir chamber 73 to the hydraulic chamber 72.

On the other hand, when the tension of the belt 4 shown in Figure 2 increases, the tension of the belt 4 causes the swing arm 20 to swing in the clockwise direction, absorbing the tension of the belt 4. At this time, the piston 74 shown in Figures 6 and 7 moves in a direction that reduces the volume of the hydraulic chamber 72, so the check valve 78 closes and hydraulic oil flows from the hydraulic chamber 72 to the reservoir chamber 73 through the aforementioned leak gap, and the viscous resistance of the hydraulic oil creates a damping effect.

As shown in Figures 1, 4, and 7, inside the swing arm 20, there is formed a sub-reservoir chamber 25 located adjacent to the reservoir chamber 73 in a direction perpendicular to the longitudinal direction of the cylinder 71, and a communication passage 26 that connects the sub-reservoir chamber 25 and the reservoir chamber 73.

As shown in FIG. 1, the hydraulic chamber 72 and the reservoir chamber 73 are filled with hydraulic oil so that no air is present. The secondary reservoir chamber 25 contains air and hydraulic oil in two layers, one above the other.

As shown in FIG. 7, the secondary reservoir chamber 25 is formed as a hole that opens axially forward at a location adjacent to the hydraulic damper 70 on the axial front side. As shown in FIGS. 1, 4, and 7, the secondary reservoir chamber 25 is sealed by a bore cap 100 that is pressed into the inner circumference of the secondary reservoir chamber 25. The bore cap 100 is prevented from coming off the swing arm 20 by crimping the axial front end face of the swing arm 20 at multiple points around the bore cap 100.

The communication passage 26, as shown in FIG. 1, is located below the fulcrum shaft 40, and as shown in FIG. 7, passes axially between the sub-reservoir chamber 25 and the reservoir chamber 73.

As shown in FIG. 1, the auxiliary reservoir chamber 25 is formed as an elongated hole that has a radial hole width and extends circumferentially longer than the hole width. The inner wall surfaces on both the upper and lower sides of the inner circumference of the auxiliary reservoir chamber 25 that connect both circumferential ends are each arc-shaped. As shown in FIG. 7, the bottom surface of the hole in the auxiliary reservoir chamber 25 has a constant depth. Note that the hydraulic oil is not shown in FIG. 7.

1, the auxiliary reservoir chamber 25 extends upward from a portion located below the fulcrum shaft 40 around the fulcrum shaft 40. A portion of the auxiliary reservoir chamber 25 on one circumferential side with respect to the communication passage 26 extends circumferentially upward, while a portion of the auxiliary reservoir chamber 25 on the other circumferential side with respect to the communication passage 26 also extends circumferentially upward. Considering the angle around the axis _O1 of the fulcrum shaft 40, the auxiliary reservoir chamber 25 spans a range of 180°. The communication passage 26 opens at a central position that divides the entire circumferential length of the auxiliary reservoir chamber 25 in half.

The amount of hydraulic oil contained in the secondary reservoir chamber 25 is set so that a height difference remains between the hydraulic oil level and the communication passage 26 within the possible swing range of the swing arm 20. This height difference is intended to ensure that the air contained in the secondary reservoir chamber 25 remains in an upper region that is higher than the open position of the communication passage 26, even if the swing arm 20 swings when the tension of the belt 4 fluctuates. The air is contained in the upper regions on both circumferential sides of the secondary reservoir chamber 25.

The communication passage 26 opens at a position that is a distance d from the upper inner wall surface of the secondary reservoir chamber 25. When the swing arm 20 rotates left or right about the fulcrum shaft 40, even if the air floating in the hydraulic oil in the secondary reservoir chamber 25 moves along the upper inner wall surface of the secondary reservoir chamber 25 from the right side to the left side in FIG. 1 or from the left side to the right side in FIG. 1, the moving air does not reach the communication passage 26 because the aforementioned distance d is provided.

Even if the tilt angle θ of the swing arm 20 becomes a large elevation or depression angle and all of the air contained in the secondary reservoir chamber 25 moves to one side in the circumferential direction of the secondary reservoir chamber 25, the air will remain in the upper region that is higher than the open position of the communication passage 26 and will not reach the communication passage 26.

In this way, in the auxiliary belt tensioner unit 1, the secondary reservoir chamber 25 extends upward from a position located below the fulcrum shaft 40, around the fulcrum shaft 40, and the communicating passage 26 opens to the secondary reservoir chamber 25 at a position below the fulcrum shaft 40. This allows the area around the fulcrum shaft 40 to be utilized to form the secondary reservoir chamber 25, expanding the secondary reservoir chamber 25 upward, storing more hydraulic oil and raising the oil level, and increasing the height difference between the oil level and the communicating passage 26. As a result, even if the inclination angle θ of the oscillating arm 20 is large, air is retained in the upper region of the secondary reservoir chamber 25, which is higher than the open position of the communicating passage 26, making it difficult for the air to enter the communicating passage 26. In other words, even if the tilt angle θ of the swing arm 20 supporting the tension pulley 30 is large, the accessory belt tensioner unit 1 can prevent air in the secondary reservoir chamber 25 formed in the swing arm 20 from entering the hydraulic chamber 72 (see FIG. 7) of the hydraulic damper 70 attached to the swing arm 20.

In addition, in the auxiliary belt tensioner unit 1, the secondary reservoir chamber 25 is axially adjacent to the hydraulic damper 70, and the communication passage 26 passes axially between the secondary reservoir chamber 25 and the reservoir chamber 73 (see FIG. 7), which avoids placing the hydraulic damper 70 and the secondary reservoir chamber 25 on the same plane perpendicular to the fulcrum shaft 40 (see FIGS. 6 and 7), and allows the large secondary reservoir chamber 25 to be placed around the fulcrum shaft 40 (see FIGS. 1 and 7).

Furthermore, in the accessory belt tensioner unit 1, the spring 60 and hydraulic damper 70 are arranged on the same plane perpendicular to the fulcrum shaft 40 (see Figure 6), which avoids arranging the spring 60, hydraulic damper 70, and secondary reservoir chamber 25 on the same plane (see Figures 4, 6, and 7), and makes it easy to arrange a large secondary reservoir chamber 25 around the fulcrum shaft 40 (see Figures 1 and 7).

In addition, in the auxiliary belt tensioner unit 1, the secondary reservoir chamber 25 is formed as an elongated hole having a hole width in the radial direction perpendicular to the axis of the fulcrum shaft 40 and extending circumferentially longer than the hole width, so that the secondary reservoir chamber 25 can be expanded upward (see Figure 1) without having to particularly expand the swing arm 20 in the radial direction around the fulcrum shaft 40 (see Figures 3 to 7).

In addition, in the auxiliary belt tensioner unit 1, the secondary reservoir chamber 25 extends upward on both circumferential sides of the communication passage 26, so that air can be accommodated in the upper regions on both circumferential sides of the secondary reservoir chamber 25, ensuring the amount of air accommodated necessary to absorb pressure changes in the cylinder 71 caused by the movement of the piston 74 (see Figures 1 and 7), while raising the oil level of the hydraulic oil and creating a height difference between the oil level and the communication passage 26.

In addition, in the auxiliary belt tensioner unit 1, the communication passage 26 is open at a position that is a distance d from the upper inner wall surface of the secondary reservoir chamber 25, so that when the swing arm 20 swings, even if the air floating in the hydraulic oil moves along the upper inner wall surface of the secondary reservoir chamber 25, it is difficult for the air to enter the communication passage 26.

In this embodiment, the auxiliary reservoir chamber 25 extends halfway around the fulcrum shaft 40, but the shape and volume of the auxiliary reservoir chamber 25 and the positional relationship with the communication passage 26 can be set so that the air in the auxiliary reservoir chamber 25 shown in FIG. 1 can be kept in an upper region higher than the open position of the communication passage 26 within the allowable swing range of the swing arm 20 centered on the fulcrum shaft 40 during operation of the belt transmission device shown in FIG. 2. For example, it is also possible to form the auxiliary reservoir chamber as a circular hole that continues around the entire circumference, and to store a larger amount of hydraulic oil to raise the oil level.

In addition, an example has been shown in which the tension pulley 30 is positioned radially opposite the fulcrum shaft 40, hydraulic damper 70, and spring 60 (see Figures 3 to 5), but it is also possible to position the pulley shaft in the remaining angular region around the fulcrum shaft 40 that does not form the secondary reservoir chamber 25, and have the tension pulley axially opposite the spring, etc.

In addition, the fulcrum shaft 40 is passed through the swing arm 20 and fixed to the bracket 10, but the fulcrum shaft may be formed integrally with the swing arm or the bracket. It is also possible to use rolling bearings instead of the sliding bearings 51 and 52 that provide support between the fulcrum shaft 40, swing arm 20, and bracket 10.

It is also possible to omit the bracket 10 and provide the fulcrum shaft, first pin, and second pin directly on the engine block 7.

The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. Therefore, the scope of the present invention is indicated by the claims rather than the above description, and it is intended to include all modifications within the meaning and scope of the claims.

Reference Signs List 1: accessory belt tensioner unit 20: swing arm 25: secondary reservoir chamber 26: communication passage 30: tension pulley 40: fulcrum shaft 60: spring 70: hydraulic damper 71: cylinder 72: hydraulic chamber 73: reservoir chamber 74: piston 75: rod 80: first pin 90: second pin

Claims (5)

A swing arm supported so as to be swingable about a fulcrum shaft;
a tension pulley supported by the swing arm so as to swing integrally with the swing arm around the fulcrum shaft;
a first pin and a second pin arranged so as not to move with respect to the swing arm which swings around the fulcrum shaft;
a spring attached to the swing arm and pressing the first pin so as to urge the swing arm in one swing direction by a reaction force received from the first pin;
a hydraulic damper attached to the swing arm so as to contact the second pin and configured to damp swing of the swing arm in a direction opposite to the one swing direction,
the hydraulic damper includes a cylinder provided on the swing arm so as to move integrally with the swing arm around the fulcrum shaft, a piston that divides the inside of the cylinder into a hydraulic chamber and a reservoir chamber, and a rod connected to the piston so as to abut against the second pin,
An auxiliary reservoir chamber is formed inside the swing arm, and a communication passage is formed between the auxiliary reservoir chamber and the reservoir chamber, the hydraulic chamber and the reservoir chamber are filled with hydraulic oil, and the auxiliary reservoir chamber contains air and hydraulic oil in two layers, one above the other, in a tensioner unit for an accessory belt,
the auxiliary reservoir chamber extends upward from a portion located below the fulcrum shaft, around the fulcrum shaft, and the communication passage opens into the auxiliary reservoir chamber at a position below the fulcrum shaft,
the auxiliary reservoir chamber is adjacent to the hydraulic damper in the axial direction, and the communication passage passes between the auxiliary reservoir chamber and the reservoir chamber in the axial direction,
a secondary reservoir chamber formed in a slot having a hole width in a radial direction perpendicular to the axis of the fulcrum shaft and extending circumferentially longer than the hole width; 2. The accessory belt tensioner unit according to claim 1 , wherein the spring and the hydraulic damper are disposed on the same plane perpendicular to the fulcrum shaft. 3. The accessory belt tensioner unit according to claim 1 , wherein the sub-reservoir chamber extends upward on both circumferential sides of the communication passage. A swing arm supported so as to be swingable about a fulcrum shaft;
a tension pulley supported by the swing arm so as to swing integrally with the swing arm around the fulcrum shaft;
a first pin and a second pin arranged so as not to move with respect to the swing arm which swings around the fulcrum shaft;
a spring attached to the swing arm and pressing the first pin so as to urge the swing arm in one swing direction by a reaction force received from the first pin;
a hydraulic damper attached to the swing arm so as to contact the second pin and configured to damp swing of the swing arm in a direction opposite to the one swing direction,
the hydraulic damper includes a cylinder provided on the swing arm so as to move integrally with the swing arm around the fulcrum shaft, a piston that divides the inside of the cylinder into a hydraulic chamber and a reservoir chamber, and a rod connected to the piston so as to abut against the second pin,
An auxiliary reservoir chamber and a communication passageway communicating between the auxiliary reservoir chamber and the reservoir chamber are formed inside the swing arm, the hydraulic chamber and the reservoir chamber are filled with hydraulic oil, and the auxiliary reservoir chamber contains air and hydraulic oil in two layers, one above the other, in a tensioner unit for an accessory belt,
the auxiliary reservoir chamber extends upward from a portion located below the fulcrum shaft, around the fulcrum shaft, and the communication passage opens into the auxiliary reservoir chamber at a position below the fulcrum shaft,
The auxiliary reservoir chamber extends upward on both circumferential sides of the communication passage . 5. An accessory belt tensioner unit according to claim 3 , wherein the communication passage opens at a position spaced apart from an upper inner wall surface of the auxiliary reservoir chamber.

Images