JP6304188B2 - Belt tensioner - Google Patents

Description

  The present invention relates to a belt tensioner, and more particularly to a belt tensioner that presses a transmission belt wound around a pulley with two tension rollers from both the upstream side and the downstream side of the pulley.

  Generally, in an internal combustion engine having a plurality of cylinders, an accessory driving device is installed at the front end in the cylinder row direction. The auxiliary machine driving device is formed by winding a transmission belt between a crankshaft pulley mounted at the tip of a crankshaft of an internal combustion engine and driving pulleys of various engine auxiliary machines. Power is transmitted to various engine accessories by a transmission belt that is circulated by a crankshaft pulley. In such an auxiliary machine drive device, in order to maintain a constant set tension (tension generated in the belt when the engine is assembled) regardless of the length of the transmission belt due to elongation, wear, and manufacturing variations, the transmission belt is usually loosened. An auto tensioner (belt tensioner) is installed on the side span.

  An alternator (starter / generator), which is one of the engine auxiliary machines, operates as a generator when power is transmitted by a transmission belt during operation of the internal combustion engine. However, when the engine is started, the transmission belt is circulated to drive the internal combustion engine. Operates as a starter (motor) to start. Therefore, the slack side and the tension side of the transmission belt are switched between the upstream side and the downstream side of the driving pulley of the alternator. For this reason, in particular, the drive pulley of the alternator pressurizes the transmission belt by sandwiching the transmission belt from both the upstream side and the downstream side of the pulley with two tension rollers provided at both ends of the arc-shaped tension spring. A belt tensioner may be provided (for example, refer to Patent Document 1).

JP 2009-287776 A

  In the conventional belt tensioner of the type disclosed in Patent Document 1, the spring constant of the tension spring is set so that the transmission belt does not loosen even if the transmission belt length is slightly longer than the nominal value (design value). For this reason, on the basis of the transmission belt manufactured according to the nominal value, if the belt length is short, the transmission belt becomes tight and the tension spring is pushed and spread. As a result, the tension spring pressurizes the transmission belt with a large spring force, and the tension of the transmission belt increases. On the other hand, if the belt length is longer, the transmission belt becomes looser and the amount of tension spring spread decreases, so that the spring force of the tension spring weakens and the tension of the transmission belt decreases. Thus, in the conventional belt tensioner, the set tension varies depending on the belt length. In particular, when the set tension increases, there is a problem that the belt drive torque increases and the mechanical resistance of the engine increases.

  In view of the above problems, an object of the present invention is to provide a belt tensioner capable of keeping the set tension substantially constant regardless of the length of the transmission belt.

  A belt tensioner according to an aspect of the present invention is a belt tensioner that presses the outer peripheral surface of a transmission belt wound around a pulley with two tension rollers from both the upstream side and the downstream side of the pulley. A first arm pivotable about a rotation axis of the first arm, a second arm coupled to the first end of the first arm pivotably about an axis parallel to the pivot axis of the first arm, A first tension roller pivotally supported on the second end of the first arm so as to be rotatable about an axis parallel to the rotation axis of the first arm, and a rotation about an axis parallel to the rotation axis of the first arm. A second tension roller pivotally supported on the first end of the second arm on the side opposite to the first arm, and a second arm that is pivotable about an axis parallel to the pivot axis of the first arm. A compression bar connected to the third end of one arm and the second end of the second arm, respectively. It is obtained by a unit.

  According to this, as the transmission belt becomes shorter, the compression spring unit shrinks more and the compression spring force becomes stronger, but the angle at which the compression spring force acts on the second arm becomes shallower, and as the transmission belt becomes longer, the compression spring unit shrinks. Becomes smaller and the compression spring force becomes weaker, but the angle at which the compression spring force acts on the second arm becomes deeper. Therefore, regardless of the length of the transmission belt, the force with which the second tension roller presses the transmission belt is substantially constant, and the tension of the transmission belt is kept substantially constant.

  In the belt tensioner described above, the compression spring unit may have a helical spring as a compression spring.

  According to this, the spring constant can be set to a relatively large value, and the natural frequency of the accessory driving apparatus to which the transmission belt is assembled can be easily removed from the vibration frequency of the internal combustion engine, thereby suppressing resonance.

  In the belt tensioner described above, the pulley is, for example, a pulley that drives an auxiliary machine having the largest inertia in an auxiliary machine driving device that drives a plurality of auxiliary machines with a transmission belt.

  According to this, a greater driving loss reduction effect can be obtained by disposing the belt tensioner at a portion where the inertia is large, that is, the angular velocity fluctuation is large.

  According to the present invention, the set tension can be kept substantially constant regardless of the length of the transmission belt.

The top view of the accessory drive device which assembled | attached the belt tensioner which concerns on one Embodiment of this invention. Top view of belt tensioner Cross-sectional view of belt tensioner Exploded view of belt tensioner VV sectional view of FIG. Diagram explaining the operating principle of the belt tensioner Graph showing the relationship between belt length and belt tension

  Hereinafter, embodiments will be described in detail with reference to the drawings as appropriate. However, more detailed explanation than necessary may be omitted. For example, detailed descriptions of already well-known matters and repeated descriptions for substantially the same configuration may be omitted. This is to avoid the following description from becoming unnecessarily redundant and to facilitate understanding by those skilled in the art.

  In addition, the inventors provide the accompanying drawings and the following description in order for those skilled in the art to fully understand the present invention, and these are intended to limit the subject matter described in the claims. is not. In addition, the dimensions, thicknesses, detailed shapes of details, and the like of each member depicted in the drawings may be different from actual ones.

  FIG. 1 is a plan view of an auxiliary machine driving apparatus in which a belt tensioner according to an embodiment of the present invention is assembled. In the accessory driving apparatus 100, an alternator driving pulley 101 is a pulley attached to the tip of a rotating shaft of an alternator (not shown). The crankshaft pulley 102 is a pulley attached to the tip of the crankshaft of an internal combustion engine (not shown), and its diameter is sufficiently larger than the diameter of the alternator driving pulley 101. The air conditioner drive pulley 103 is a pulley attached to the tip of the rotating shaft of an air conditioner compressor (not shown), and its diameter is sufficiently larger than the diameter of the alternator drive pulley 101. The accessory drive device 100 is configured by winding a transmission belt 104 around these pulleys 101 to 103.

  The transmission belt 104 is a V belt or a cogged belt formed by covering a core wire using an aramid fiber or the like with a waterproof rubber such as a canvas and hydrogenated nitrile rubber. Such a transmission belt 104 is light in weight, has little bending deformation, wear and elongation, and has a feature that it can be used for a relatively small-diameter pulley such as the alternator driving pulley 101 because the allowable pulley diameter is small.

  When an internal combustion engine (not shown) is operating, the crankshaft pulley 102 serves as a driving pulley, and the power transmission belt 104 is circulated in a predetermined direction to transmit power to the alternator driving pulley 101 and the air conditioner driving pulley 103 as driven pulleys. . Thereby, an alternator (not shown) operates as a generator to generate power. On the other hand, when the engine is started, an alternator (not shown) operates as a starter (motor), and the alternator driving pulley 101 serves as a driving pulley to circulate the transmission belt 104 in a predetermined direction, thereby supplying power to the crankshaft pulley 102 as a driven pulley. introduce. As a result, the internal combustion engine (not shown) is started.

  In the accessory driving apparatus 100, a belt tensioner 10 is attached to an alternator driving pulley 101. More specifically, the belt tensioner 10 is attached to an unillustrated alternator body or a mounting plate 20 fixed to the engine. The belt tensioner 10 is a belt tensioner that presses the outer peripheral surface of the transmission belt 104 wound around the alternator driving pulley 101 with two tension rollers from both the upstream side and the downstream side of the alternator driving pulley 101. By providing the belt tensioner 10, the set tension is kept substantially constant.

  As described above, the alternator driving pulley 101 is switched as a driven pulley or a driving pulley depending on the situation. When the alternator drive pulley 101 operates as a driven pulley, the transmission belt 104 becomes loose on the upstream side of the rotation of the alternator drive pulley 101, and the transmission belt 104 becomes tight on the downstream side of the rotation. On the other hand, when the alternator driving pulley 101 operates as a driving pulley, the transmission belt 104 becomes tight on the upstream side of the rotation of the alternator driving pulley 101, and the transmission belt 104 becomes loose on the downstream side of the rotation. Thus, the tension side and the slack side of the transmission belt 104 are switched on the upstream side and the downstream side of the alternator drive pulley 101. Further, the alternator driving pulley 101 has a larger inertia than the other pulleys 102 and 103 due to its smaller diameter. The belt tensioner 10 is attached to such a pulley (alternator driving pulley 101). As described above, by disposing the belt tensioner 10 in a portion where the inertia is large, that is, the angular velocity fluctuation is large, a greater driving loss reduction effect can be obtained.

  Next, the configuration of the belt tensioner 10 will be described in detail with reference to the drawings. FIG. 2 is a plan view of the belt tensioner 10. FIG. 3 is a plan sectional view of the belt tensioner 10. FIG. 4 is an exploded view of the belt tensioner 10. 5 is a cross-sectional view taken along the line VV in FIG.

  The belt tensioner 10 includes a first arm 11, a second arm 12, a first tension roller 13, a second tension roller 14, and a compression spring unit 15.

  The first arm 11 is a generally flat, substantially triangular member having a large circular opening at the central portion 111. The mounting plate 20 is also a generally flat and substantially triangular member having a large circular opening at the center. As shown in FIG. 5, a flange 110 having a circular shape in plan view is formed around a circular opening in the central portion 111 of the first arm 11. A circular flange 200 in plan view is also formed around the circular opening at the center of the mounting plate 20 so as to surround the rotating shaft 106 of the alternator 105. The diameter of the flange 110 is slightly larger than the diameter of the flange 200, and the flange 110 and the flange 200 are fitted. A bearing 30 is provided between the outer peripheral surface of the flange 200 and the inner peripheral surface of the flange 110. As the bearing 30, for example, a sleeve bearing or a resin bush can be used. That is, the first arm 11 is pivotally supported by the mounting plate 20 and is rotatable about the rotation shaft 106 of the alternator driving pulley 101.

  Note that the rotation axis of the first arm 11 and the rotation axis 106 of the alternator driving pulley 101 do not have to be exactly matched. The first arm 11 only needs to be rotatable about an axis parallel to the rotation shaft 106 of the alternator driving pulley 101.

  The second arm 12 is a substantially rod-shaped member. The second arm 12 is connected to the first end 112 of the first arm 11 so as to be rotatable about an axis parallel to the rotation axis of the first arm 11, that is, the rotation axis 106 (see FIG. 5) of the alternator 105. Has been.

  Specifically, the first end 111 of the first arm 11 is formed as a protruding shaft and the central portion 121 of the second arm 12 is formed as a bearing hole, or the first end 111 of the first arm 11 is formed. The first arm 11 is formed as a bearing hole and the central portion 121 of the second arm 12 is formed as a protruding shaft so that the second arm 12 can be rotated about an axis parallel to the rotational axis of the first arm 11. To the first end 112 of the first end 112. Alternatively, the first end portion 111 of the first arm 11 and the central portion 121 of the second arm 12 are both formed as bearing holes, and a screw (not shown) is inserted into both the bearing holes, so that the second arm 12 is The first arm 11 can be connected to the first end 112 so as to be rotatable about an axis parallel to the rotation axis of the first arm 11.

  The first arm 11, the second arm 12, and the mounting plate 20 can be formed by, for example, aluminum die casting.

  At the second end 113 of the first arm 11, the first tension roller 13 is rotatable about an axis parallel to the rotation axis of the first arm 11, that is, the rotation axis 106 (see FIG. 5) of the alternator 105. Is pivotally supported. Further, at the first end portion 122 of the second arm 12 on the side opposite to the first arm 11, the second tension roller 14 rotates the rotation shaft 106 of the first arm 11, that is, the rotation shaft 106 of the alternator 105 (see FIG. 5). Is pivotally supported around an axis parallel to the axis.

  Specifically, both the second end 113 of the first arm 11 and the first end 122 of the second arm 12 are formed as projecting shafts, and these projecting shafts are used as the first tension roller 13 and the second tension roller. By inserting the first tension roller 13 and the second tension roller 14 around the axis parallel to the rotation axis of the first arm 11, the second end 113 of the first arm 11 can be rotated. And can be pivotally supported at the first end 122 of the second arm 12.

  The main bodies of the first tension roller 13 and the second tension roller 14 are made of metal (for example, ball bearings), and the outer periphery is covered with resin. The first tension roller 13 and the second tension roller 14 are in contact with the surface of the transmission belt 104 so as to press the transmission belt 104 at the outer periphery on both the upstream side and the downstream side of the alternator driving pulley 101 and circulate. The tension of the driven transmission belt 104 is kept substantially constant.

  The compression spring unit 15 is a substantially rod-like member that can be expanded and contracted. The first end 151 of the compression spring unit 15 is rotatable about the axis of rotation of the first arm 11, that is, about the axis parallel to the rotation axis 106 (see FIG. 5) of the alternator 105. It is connected to the three end portions 114. The second end 152 of the compression spring unit 15 is rotatable about the axis of rotation of the first arm 11, that is, about the axis parallel to the rotation axis 106 (see FIG. 5) of the alternator 105. Is connected to the second end 123.

  Specifically, the third end 114 of the first arm 11 is formed as a protruding shaft and the first end 151 of the compression spring unit 15 is formed as a bearing hole, or the third end of the first arm 11 is formed. 114 is formed as a bearing hole, and the first end 151 of the compression spring unit 15 is formed as a protruding shaft, so that the first end 151 of the compression spring unit 15 is an axis parallel to the rotation axis of the first arm 11. It can be connected to the third end 114 of the first arm 11 so as to be rotatable around. Alternatively, both the third end 114 of the first arm 11 and the first end 151 of the compression spring unit 15 are formed as bearing holes, and screws (not shown) are inserted into the both bearing holes, so that the compression spring unit 15 The first end 151 of the first arm 11 can be connected to the third end 114 of the first arm 11 so as to be rotatable about an axis parallel to the rotation axis of the first arm 11.

  Similarly, the second end 123 of the second arm 12 is formed as a protruding shaft and the second end 152 of the compression spring unit 15 is formed as a bearing hole, or the second end 123 of the second arm 12 is formed. By forming as a bearing hole and forming the second end 152 of the compression spring unit 15 as a protruding shaft, the second end 152 of the compression spring unit 15 is rotated around an axis parallel to the rotation axis of the second arm 11. It can be connected to the second end 123 of the second arm 12 in a rotatable manner. Alternatively, both the second end 123 of the second arm 12 and the second end 152 of the compression spring unit 15 are formed as bearing holes, and screws (not shown) are inserted into the both bearing holes, so that the compression spring unit 15 The second end 152 can be connected to the second end 123 of the second arm 12 so as to be rotatable about an axis parallel to the rotation axis of the first arm 11.

  As shown in FIG. 3, the compression spring unit 15 has a helical spring 150 as a compression spring. That is, when the compression spring unit 15 is compressed in the full length direction, a spring force that pushes back the compression spring unit 15 works. Both ends of the compression spring unit 15 are connected to the third end 114 of the first arm 11 and the second end 123 of the second arm 12, and the second arm 12 is connected to the first end of the first arm 11. Since the first tension roller 13 and the second tension roller 14 are pivotally connected to the section 112, the first tension roller 13 and the second tension roller 14 have the first end 112 of the first arm 11 as an axis and the upstream side of the alternator driving pulley 101. The transmission belt 104 is biased from both sides of the downstream side of the rotation.

  Although a leaf spring can be used as the compression spring, a helical spring is preferable in that a large spring constant can be set. If the spring constant can be set large, the natural frequency of the auxiliary drive unit 100 can be easily removed from the vibration frequency caused by the explosive force generated in the normal range of the internal combustion engine (not shown), and resonance can be suppressed. .

  Next, the operation principle of the belt tensioner 10 will be described with reference to FIG. For convenience of explanation, each member of the belt tensioner 10 is simplified in FIG. 6 (for example, the second arm 12 is drawn as a line segment).

  The second arm 12 operates as a “first type lever” having the central portion 121 as a fulcrum, the second end portion 123 as a power point, and the first end portion 122 as an action point. A compression spring force by the compression spring unit 15 acts on the second end 123 as a force point. Then, the force acting on the first end portion 122 as an action point becomes a force pressing the second tension roller 14 against the transmission belt 104.

  When the length of the transmission belt 104 is longer than the nominal value, the transmission belt 104 is pushed deeply by the second tension roller 14. On the other hand, when the length of the transmission belt 104 is shorter than the nominal value, the pushing of the transmission belt 104 by the second tension roller 14 becomes shallow.

  On the other hand, the intermediate portion 121 of the second arm 12 and the first end portion 151 of the compression spring unit 15 are connected to the second end portion 112 and the third end portion 114 of the first arm 11 at both ends in the expansion / contraction direction, respectively. Therefore, the relative positional relationship between the intermediate portion 121 of the second arm 12 and the first end portion 151 of the compression spring unit 15 does not change. Therefore, when the length of the transmission belt 104 is longer than the nominal value, the distance between the second end 123 of the second arm 12 and the first end 151 of the compression spring unit 15, that is, the total length of the compression spring unit 15. Becomes longer and the compression spring force becomes weaker. On the other hand, when the length of the transmission belt 104 is shorter than the nominal value, the total length of the compression spring unit 15 is shortened, that is, the compression spring unit 15 is compressed and the compression spring force is increased.

Here, F is a force acting on the second end 123 of the second arm 12 in the extending direction of the compression spring unit 15, and θ is an angle at which the compression spring force acts on the second end 123 of the second arm 12. A distance from the intermediate part 121 to the second end part 123 is set to a unit length “1”. At this time, the moment M generated in the second arm 12 is
M = F · sinθ
It is represented by

  Comparing the case where the transmission belt 104 is longer than the nominal value and the case where the transmission belt 104 is shorter, the force F is smaller when the transmission belt 104 is longer and larger when the transmission belt 104 is shorter. On the other hand, the sine of the angle θ (sin θ), contrary to the force F, is larger when the transmission belt 104 is longer and smaller when the transmission belt 104 is shorter. Therefore, the moment M represented by the product of F and sin θ is kept substantially constant regardless of the length of the transmission belt 104.

  FIG. 7 is a graph showing the relationship between belt length and belt tension. In the conventional belt tensioner, the tension of the transmission belt 104 increases when the transmission belt 104 is shorter than the nominal value, and decreases when the transmission belt 104 is longer than the nominal value. On the other hand, according to the belt tensioner 10 according to the present embodiment, even if the transmission belt 104 is slightly shorter or longer than the nominal value, the tension of the transmission belt 104 is kept substantially constant.

  As described above, according to the present embodiment, the set tension can be maintained at the initial value even when the transmission belt 104 manufactured longer than the nominal value is extended over a long period of time and the length of the transmission belt 104 changes. . Furthermore, since the energy absorbed from the tension side of the transmission belt 104 can be used as the biasing force on the loose side of the transmission belt 104 via the compression spring unit 15, the driving loss of the timing belt system can be reduced.

  As described above, the embodiments have been described as examples of the technology in the present invention. For this purpose, the accompanying drawings and detailed description are provided.

  Accordingly, among the components described in the accompanying drawings and the detailed description, not only the components essential for solving the problem, but also the components not essential for solving the problem in order to illustrate the above technique. May also be included. Therefore, it should not be immediately recognized that these non-essential components are essential as those non-essential components are described in the accompanying drawings and detailed description.

  Moreover, since the above-mentioned embodiment is for demonstrating the technique in this invention, a various change, replacement, addition, abbreviation, etc. can be performed in a claim or its equivalent range.

10 Belt tensioner 11 First arm 112 First end (first end of first arm)
113 Second end (second end of first arm)
114 3rd end part 12 2nd arm 122 1st end part (1st end part of 2nd arm)
123 Second end (second end of the second arm)
13 First tension roller 14 Second tension roller 15 Compression spring unit 150 Helical spring 100 Auxiliary machine drive 101 Alternator drive pulley (pulley)
104 Transmission belt

Claims (3)

A belt tensioner that pressurizes the outer peripheral surface of a transmission belt wound around a pulley with two tension rollers from both the upstream side and the downstream side of the pulley;
A first arm that is rotatable about a rotation axis of the pulley;
A second arm connected to the first end of the first arm so as to be rotatable about an axis parallel to the rotation axis of the first arm;
A first tension roller pivotally supported on the second end of the first arm so as to be rotatable about an axis parallel to the rotation axis of the first arm;
A second tension roller pivotally supported on a first end of the second arm on the side opposite to the first arm so as to be rotatable about an axis parallel to the rotation axis of the first arm;
A compression spring unit having both ends connected to a third end of the first arm and a second end of the second arm so as to be rotatable around an axis parallel to the rotation axis of the first arm; Belt tensioner.   The belt tensioner according to claim 1, wherein the compression spring unit has a helical spring as a compression spring.   3. The belt tensioner according to claim 1, wherein the pulley is a pulley that drives an auxiliary machine having the largest inertia in an auxiliary machine driving apparatus that drives a plurality of auxiliary machines with the transmission belt. 4.

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