JP2525578B2 - Belt Tenshiona - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a belt tensioner for giving a predetermined tension to an endless belt, and more particularly to a tensioner pulley supported eccentrically. The present invention relates to a belt tensioner in which the tension of the belt is automatically adjusted by following the extension of the belt.

(Prior Art) For example, in an automobile engine, since it is necessary to rotate a cam shaft in conjunction with a crank shaft, a cam pulley and a crank pulley are attached to the cam shaft and the crank shaft, respectively, and a timing belt is endlessly attached to these pulleys. In many cases, the rotation is transmitted from the crankshaft to the camshaft in a line. In that case, since the length of the timing belt is considerably long in the overhead cam type engine,
The belt may be stretched due to changes in temperature or changes with time. If the timing belt extends in such a manner, the timing phase may be shifted or abnormal noise may be generated. Therefore, such a belt transmission mechanism is usually
A belt tensioner that can apply a constant tension to the belt is provided.

There are various types of belt tensioners, but as an engine compact one, a belt tensioner using an eccentric pulley is known. The eccentric pulley includes an outer cylinder that is pressed against the belt and an inner cylinder that rotatably supports the outer cylinder. Then, the inner cylinder is supported on a fixed wall surface of the engine body or the like by an eccentric shaft provided at a position eccentric from the rotation center of the outer cylinder in the projection plane.

In a belt tensioner using such an eccentric pulley, the tension of the belt is adjusted by swinging the pulley around the eccentric shaft. That is, the eccentric pulley becomes a tensioner pulley.

As a means for applying tension to the belt by the tensioner pulley which is eccentrically supported as described above, as shown in JP-B-58-7856 and JP-A-57-198306, the swing of the pulley is manually adjusted. In addition to those fixed at that position, as shown in Japanese Utility Model Laid-Open No. 56-144853 and Japanese Utility Model Laid-Open No. 58-151738, the pulley is always swung in the direction to tension the belt. It is also considered to be a forceful one. By biasing the tensioner pulley in this way, the tension of the belt is automatically adjusted in accordance with the extension of the belt.

In the case where the tensioner pulley is oscillated and urged in this way, conventionally, a spring has been generally used as the urging means as shown in the above publication.

(Problems to be solved by the invention) However, in such a structure in which the tensioner pulley is swung by the spring, the strength of the spring is limited, so that the pulley is firmly held. It is not possible. Moreover, since the eccentric shaft is provided in the projection plane of the pulley, the distance between the eccentric shaft and the point where the spring is locked to the pulley cannot be increased and a large swinging moment is applied to the pulley. I can't do it either. Therefore, in such a belt tensioner, there is a problem that when a large load is applied from the belt, the belt tensioner swings in the opposite direction.

By the way, for belt tensioners,
As shown in Japanese Patent Laid-Open Publication No. JP-A-2003-163, there is a system in which a shoe is brought into pressure contact with a belt by a hydraulic adjuster, thereby tensioning the belt. When such a hydraulic adjuster is used, the stroke of the tensioner can be automatically adjusted with a constant hydraulic pressure, and moreover, it can withstand a large load applied from the belt.

Therefore, it is conceivable to apply such a hydraulic adjuster to the tensioner pulley that is eccentrically supported as described above, and apply the swinging force by the hydraulic adjuster. However, the hydraulic adjuster has a slight response delay. Further, when the temperature of the hydraulic oil rises, the viscosity decreases, so that the leak amount increases and the pressure also decreases.

The present invention has been made in view of the above circumstances, and an object thereof is to be compact, yet capable of withstanding a large load, excellent in responsiveness, and less affected by temperature changes. To obtain an automatic tension adjustable belt tensioner.

Another object of the present invention is to obtain a belt tensioner in which the initial tension of the belt can be easily adjusted.

(Means for Solving the Problem) In order to achieve this object, in the present invention, a belt is provided on a tensioner pulley that is swingably supported about an eccentric shaft by both a hydraulic adjuster and a spring adjuster. I am trying to apply a swinging force in the direction of tension. The hydraulic adjuster and the spring adjuster are arranged substantially parallel to each other in a region surrounded by an endless belt, and are engaged with the tensioner pulleys on both sides of the eccentric shaft. The engaging portion and the eccentric shaft are both arranged in the projection plane of the tensioner pulley.

(Operation) With this configuration, the load applied from the belt is supported by the hydraulic adjuster and the spring adjuster. Since the hydraulic adjuster can exert a large force, the belt can be securely held in a tensioned state even if the distance between the position where the hydraulic adjuster engages the tensioner pulley and the eccentric shaft that is the swing center is small. To be done. Therefore, the belt tensioner can be compact and can withstand a large load.

Further, since the tensioner pulley is urged to swing by the spring adjuster, the tensioner pulley immediately follows when the belt is stretched. Therefore, the belt tensioner has the advantages of both the hydraulic adjuster and the spring adjuster.

The hydraulic adjuster and the spring adjuster are engaged with the tensioner pulley on both sides of the eccentric shaft in the projection plane of the tensioner pulley, and they are arranged substantially parallel to each other in the area surrounded by the endless belt. By doing so, it becomes possible to configure the entire belt tensioner compactly,
The initial tension adjustment work of the belt becomes easy.

(Examples) Examples of the present invention will be described below with reference to the drawings.

The figure shows an embodiment in which a belt tensioner according to the present invention is applied to a camshaft drive device of an engine,
FIG. 1 is a front view of the camshaft drive device, and FIG. 2 is an enlarged view of a main part thereof. Also, FIGS. 3 and 4
The figure is a cross-sectional view and bottom view of the belt tensioner,
FIG. 5 is a vertical sectional view of the hydraulic adjuster.

As is apparent from FIG. 1, this engine 1 is a double overhead cam type engine, and a camshaft drive device 5 for driving a pair of camshafts 3, 3 by a crankshaft 4 is provided on one end surface of an engine body 2. It is provided. The camshaft drive device 5 is a device in which a timing belt 8 is wound endlessly between a crank pulley 6 attached to a crankshaft 4 and cam pulleys 7, 7 attached to a camshaft 3,3. The timing belt 8 is rotated counterclockwise in the figure by the rotation of the crankshaft 4. On the tension side of the timing belt 8, that is, on the back surface of the portion between the cam pulley 7 and the crank pulley 6 on the left side in the figure, another driven pulley 9 is press-contacted, and the driven pulley 9 assists a water pump or the like. The machine is designed to be driven. The driven pulley 9 is supported by the cylinder block 2a of the engine body 2.

A belt tensioner 10 is provided on the loose side of the timing belt 8, that is, between the cam pulley 7 and the crank pulley 6 on the right side in the drawing. That belt tensioner 10
Has a tensioner pulley 11, a hydraulic adjuster 12, and a spring adjuster 13, which are supported by a cylinder head 2b of the engine body 2.

As is clear from FIGS. 1 to 3, the tensioner pulley 11
Is composed of an annular outer cylinder 14 that is pressed against the back surface of the timing belt 8 and an inner cylinder 16 that rotatably supports the outer cylinder 14 via bearings 15. Its inner cylinder 16
Eccentric shaft 18 via a bearing 17 at a position eccentric from the center of rotation of outer cylinder 14 in the projection plane of tensioner pulley 11.
Is inserted. The eccentric shaft 18 is fixed to the end surface of the cylinder head 2b, which is a fixed wall surface, by a screw 18a. In this manner, the inner cylinder 16 is rotatably supported with respect to the engine body 2, and the rotation causes the tensioner pulley 11 to swing in the left-right direction in FIG. 1 about the eccentric shaft 18. .

Between the tensioner pulley 11 and the cylinder head 21b, an oval drive plate 19 is attached through which an eccentric shaft 18 rotatably passes through a central portion. A plurality of bosses 20, 20 projecting toward the inner cylinder 16 side of the tensioner pulley 11 are integrally provided on the drive plate 19, and the bosses 20, 20 are bolts 21, 21 from the inner cylinder 16 side. Are tightened, whereby the inner cylinder 16 and the drive plate 19 are integrally connected.

Bearings 22 and 23 are attached to the cylinder head 2b side surface at both ends in the longitudinal direction of the drive plate 19 by bolts 24 and 24, respectively. The lower bearing 22 is an eccentric shaft
The tensioner pulley 11 is located on the opposite side of 18 from the center of rotation of the outer cylinder 14. Further, the upper bearing 23 is positioned on the rotation center side of the outer cylinder 14 with respect to the eccentric shaft 18. And the upper bearing 23
The distance between the eccentric shaft 18 and the eccentric shaft 18 is larger than the distance between the lower bearing 22 and the eccentric shaft 18.

As is apparent from FIG. 2, the tip end of the hydraulic adjuster 12 contacts the outer peripheral surface of the lower bearing 22. Further, the tip end portion of the spring adjuster 13 is engaged with the outer circumference of the upper bearing 23. That is, the hydraulic adjuster 12 engages with the tensioner pulley 11 on the side opposite to the rotation center of the outer cylinder 14 of the tensioner pulley 11 with respect to the eccentric shaft 18, and the spring adjuster 13
Are engaged with the tensioner pulley 11 on the rotation center side of the outer cylinder 14 with respect to the eccentric shaft 18. All of these engaging portions are designed to fit within the projection surface of the tensioner pulley 11. The hydraulic adjuster 12 and the spring adjuster 13 are arranged substantially in parallel within the area surrounded by the timing belt 8. Also, the third,
As shown in FIG. 4, the hydraulic adjuster 12 and the spring adjuster 13 are arranged between the plane including the tensioner pulley 11, that is, the plane around which the timing belt 8 is stretched, and the end surface of the cylinder head 2b. ing.

The hydraulic adjuster 12 has a hollow cylindrical housing 27 having an open end fixed to a boss 26 of the cylinder head 2b by a bolt 25. As shown in FIG. 5, a hollow cylindrical cylinder body 28 having an open end is fitted in the housing 27. The amount of protrusion of the cylinder body 28 from the housing 27 is adjusted by an adjustment body 30 that is screwed into the base end surface of the housing 27 and locked by the lock night 29.

A plunger 31 having a small tip is slidably fitted in the cylinder body 28.
The pressure chamber 32 is defined by 31. In the pressure chamber 32, a spring 33 that biases the plunger 31 in a protruding direction is housed in a compressed state. Further, an oil passage 34 that penetrates in the axial direction is provided in the plunger 31. The tip end side of the oil passage 34 is oil-tightly sealed by a plunger cap 31a fixed to the tip end of the plunger 31. On the other hand, the base end opening 34a of the oil passage 34 is
It is adapted to be opened and closed by a check valve 35 attached to the base end surface of 1. The check valve 35 closes the base end opening 34a when the hydraulic pressure in the pressure chamber 32 is higher than the hydraulic pressure in the oil passage 34.

The tip end of the cylinder body 28 and the tip end of the plunger 31 are oil-tightly sealed by a diaphragm 36 made of a flexible material such as rubber. Thus, the plunger
A reservoir chamber 37 is formed on the outer periphery of the small diameter portion of the tip end 31. The reservoir chamber 37 communicates with the oil passage 34 in the plunger 31 via the oil supply hole 38. Further, in the plunger 31, there is provided an oil drain hole 39 that opens to the outer peripheral surface of the large diameter portion thereof, that is, a surface that slides on the cylinder body 28 and communicates with the oil passage 34.

The pressure chamber 32 of the hydraulic adjuster 12 configured as above,
In the reservoir chamber 37, the oil passage 34, the oil supply hole 38 and the oil discharge hole 39,
By removing the plunger cap 31a and filling the working oil from the oil passage 34, the working oil is filled. The cap 31a of the plunger 31 is held in contact with the outer peripheral surface of the bearing 22 attached to the drive plate 19. Also the plunger
The maximum protruding amount of 31 is limited by the stopper ring 40 attached to the inner peripheral surface of the tip portion of the cylinder body 28.

On the other hand, the spring adjuster 13 is composed of an eyebolt 41 and a coil spring 42, as shown in FIG. The eyebolt 41 has its tip
It is fitted on the outer periphery of a bearing 23 attached to the drive plate 19. The eyebolt 41 is inserted into the bracket 43 provided on the cylinder head 2b with sufficient play. A spring retainer 44 is attached to the base end side of the eyebolt 41, and a coil spring 42 is attached between the retainer 44 and the bracket 43 in a compressed state. The position of retainer 44 is adjusted by adjusting nut 45.
Is adjusted by.

Thus, the tensioner pulley 11 is biased by the spring adjuster 13 so as to swing in the left direction in FIG. 1, that is, in the direction in which the timing belt 8 is tensioned.

Next, the operation of the belt tensioner 10 thus configured will be described.

When the engine 1 is operating, the crank pulley 6 is rotated by the rotation of the crank shaft 4, and the rotation is transmitted to the cam pulleys 7, 7 via the timing belt 8, so that the cam shafts 3, 3 are rotationally driven. In the meantime, since the driven pulley 9 and the tensioner pulley 11 are pressed against the timing belt 8 from the back side thereof, the timing belt 8 is held in a tensioned state. The initial tension of the timing belt 8 is adjusted by the adjusting bolt 30 of the hydraulic adjuster 12 of the belt tensioner 10 and the spring adjuster.
It is set optimally by adjusting the adjusting nut 45 of 13. In that case, since the hydraulic adjuster 12 and the spring adjuster 13 are arranged substantially parallel to each other at positions close to each other, the adjusting bolt 30 and the adjusting nut 45 can be adjusted from the same direction. Therefore, it becomes easy to use the work tool during the adjustment,
The workability becomes good.

When the timing belt 8 is stretched, the tensioner pulley 11 to which a tension force is applied by the spring adjuster 13 swings leftward in FIG. 1 about the eccentric shaft 18. As a result, the timing belt 8 becomes more curved, its elongation is compensated, and the tension belt 8 is held in a tensioned state.

Then, when the tensioner pulley 11 swings to remove the pressing force applied to the plunger 31 of the hydraulic adjuster 12, the plunger 31 springs in the pressure chamber 32.
It is pushed out by 33 and further projects from the cylinder bolt 28. Therefore, the cap on the tip of the plunger 31
31a is held in contact with a bearing 22 attached to the drive plate 19 of the tensioner pulley 11. During this time, the pressure chamber 32 in the cylinder body 28 expands, so that the hydraulic pressure in the pressure chamber 32 decreases. As a result, the check valve 35 is opened, and the hydraulic oil in the reservoir chamber 37 is supplied to the pressure chamber 32 through the oil supply hole 38 and the oil passage 34. Therefore, the pressure chamber 32 is always kept filled with hydraulic oil.

In this way, when the timing belt 8 is loosened, the tensioner pulley 11 is immediately swung by the spring adjuster 13 and the looseness is removed.
Therefore, the response is excellent.

When a large pulling force is applied to the loose side of the timing belt 8 due to the fluctuation of the torque acting on the camshaft 3 or the crankshaft 4 during the operation of the timing belt 8, the tensioner pulley 11 swings to the right in FIG. The force to move it acts. The force is also countered by the coil spring 42 of the spring adjuster 13, but when the force is large, the coil spring 42 is deformed by compression. In such a case, from the tensioner pulley 11 via the bearing 22 of the drive plate 19,
A pressing force is applied to the plunger 31 of the hydraulic adjuster 12. As a result, the hydraulic pressure in the pressure chamber 32 rises and the check valve 35
Is closed. Therefore, the hydraulic oil is confined in the pressure chamber 32, and the hydraulic pressure prevents the tensioner pulley 11 from swinging to the right.

In this way, the hydraulic adjuster 12 reliably prevents the tensioner pulley 11 from swinging in the opposite direction even when a large load is applied from the timing belt 8. That is, it can withstand a large load.

When the plunger 31 is pressed by the load applied from the timing belt 8, the pressure chamber 32 is actually
The hydraulic oil therein leaks to some extent through the sliding portion between the cylinder body 28 and the plunger 31. Then, as a result, the plunger 31 is gradually retracted to prevent the tension of the timing belt 8 from becoming excessive. The leaked hydraulic oil is
It is returned to the reservoir chamber 37 through the oil drain hole 39.

When the tensile force applied to the loose side of the timing belt 8 is removed, the tension adjuster pulley 11 is given a force to swing leftward in FIG. Tension is applied. Then, the plunger 31 of the hydraulic adjuster 12 is pushed out again and kept in contact with the bearing 22 of the drive plate 19.

As described above, by using both the hydraulic adjuster 12 and the spring adjuster 13, the belt tensioner 10 has both advantages. Then, by disposing the bearings 22 engaging with the hydraulic adjuster 12 and the bearings 23 engaging with the spring adjuster 13 on both sides of the eccentric shaft 18, even when both the hydraulic adjuster 12 and the spring adjuster 13 are used, Of the tensioner pulley 11 together.
Can be placed within the projection plane of. Therefore, the belt tensioner 10 can be made compact.
In addition, the hydraulic adjuster 12 capable of withstanding a large load is attached to the eccentric shaft 18
The bearing 22 on the side closer to the
Can be arranged at a position farthest from the eccentric shaft 18 in the projection plane of the tensioner pulley 11, and the swinging moment of the tensioner pulley 11 by the spring adjuster 13 can be made sufficiently large.

In addition, the hydraulic adjuster 12 and the spring adjuster 13
The cylinder head 2b and the plane including the tensioner pulley 11.
The space between the timing belt 8 and the engine body 2 which is provided to allow the vibration of the timing belt 8 in the width direction and the like is effectively used by disposing the space between the engine belt 2 and the end surface of the engine. And thereby engine 1
It is possible to prevent an increase in the total length of the. Furthermore, since the hydraulic adjuster 12 and the spring adjuster 13 can be arranged in the area surrounded by the endless timing belt 8 between the timing belt 8 and the cylinder head 2b, they can be arranged. It is also prevented from protruding laterally. Therefore, the entire engine 1 can be compactly assembled.

Further, by making the hydraulic adjuster 12 of the sealed type as shown in FIG. 5, even when the hydraulic adjuster 12 is provided inside the timing belt 8, the hydraulic oil falls on the timing belt 8. There is no fear of being hung up. Therefore, the frictional force between the timing belt 8 and the pulleys 6, 7 and the like is secured, and the rotation transmission is surely performed.

In the above embodiment, the hydraulic adjuster 12 and the spring adjuster 13 are supposed to be engaged with the inner cylinder 16 of the tensioner pulley 11 via the drive plate 19, but they may be directly engaged with the inner cylinder 16. You can also Further, although the plunger 31 of the hydraulic adjuster 12 is supposed to contact the outer peripheral surface of the bearing 22, the hydraulic adjuster 12
It is also possible to lock the plunger 31 and the bearing 22 by swingably attaching to the cylinder head 2b.

Further, in the above embodiment, the spring adjuster
It is assumed that 13 is constituted by the coil spring 42 mounted in a compressed state, but it may be constituted by a tension spring.

Although the embodiment of the belt tensioner 10 applied to the camshaft drive device 5 of the engine 1 has been described above, the present invention is not limited to this, and is also applicable to other belt transmission mechanisms such as a belt drive device of an auxiliary machine. It will be clear that it can be applied.

(Effect of the Invention) As is apparent from the above description, according to the present invention, the eccentrically supported tensioner pulley is swung in the direction in which the belt is tensioned by the hydraulic adjuster and the spring adjuster. A belt tensioner that exhibits the advantages of both the hydraulic adjuster and the spring adjuster, can withstand a large load, has good responsiveness, and is less affected by temperature changes. Further, the hydraulic adjuster and the spring adjuster are engaged with the tensioner pulleys on both sides of the eccentric shaft in the projection plane of the tensioner pulley, and the adjusters are arranged in the area surrounded by the endless belt. Therefore, the entire belt tensioner can be made compact. Furthermore, since the hydraulic adjuster and the spring adjuster are arranged substantially parallel to each other,
The adjustment work of the initial tension of the belt by those adjusters can be facilitated.

[Brief description of drawings]

FIG. 1 is a front view showing an embodiment in which a belt tensioner according to the present invention is applied to a camshaft drive device of an engine, and FIG. 2 is an enlarged view showing the belt tensioner with a tensioner pulley removed. Fig. 3 shows the belt tensioner of III-III of Fig. 1.
4 is a bottom view of the belt tensioner taken along the line IV-IV in FIG. 1, and FIG. 5 is a vertical cross section of the hydraulic adjuster used in the belt tensioner. It is a figure. 1 ... Engine, 2 ... Engine main body 2a ... Cylinder block, 2b ... Cylinder head (fixed wall surface) 8 ... Timing belt (belt), 10 ... Belt tensioner 11 ... Tensioner pulley, 12 ... Hydraulic adjuster 13 ... Spring adjuster, 14 ... Outside Cylinder, 16 ... Inner cylinder 18 ... Eccentric shaft, 22 ... Bearing (engagement part with hydraulic adjuster) 23 ... Bearing (engagement part with spring adjuster) 28 ... Cylinder body, 31 ... Plunger, 32 ... Pressure chamber 35 ... Check valve, 42 ... Coil spring

Claims (3)

(57) [Claims] 1. An outer cylinder press-contacted to an endless belt, and an inner cylinder rotatably supporting the outer cylinder,
A tensioner pulley swingably supported by a fixed wall surface around an eccentric shaft provided at a position eccentric from the rotation center of the outer cylinder, and the tensioner pulley is engaged with the tensioner pulley on both sides of the eccentric shaft, A hydraulic adjuster and a spring adjuster for swinging the tensioner pulley in a direction in which the belt is tensioned, the eccentric shaft, an engaging portion between the hydraulic adjuster and the tensioner pulley, and the spring adjuster and the tensioner pulley. And the hydraulic adjuster and the spring adjuster are arranged substantially parallel to each other in a region surrounded by the endless belt. A belt tensioner characterized by. 2. The hydraulic adjuster engages with a tensioner pulley on the side opposite to the rotation center of the outer cylinder with respect to the eccentric shaft, and the spring adjuster rotates the outer cylinder with respect to the eccentric shaft. The belt tensioner according to claim 1, which is adapted to engage with the tensioner pulley on the center side. 3. The belt tensioner according to claim 1, wherein the hydraulic adjuster and the spring adjuster are arranged between a plane including the tensioner pulley and the fixed wall surface.