JP2005273798A - Power transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power transmission, which has high reliability for a long period, capable of maintaining functions as a medium member for power transmitting of a spring by applying no shock load on the spring and preventing its damage. <P>SOLUTION: A pulley unit 1 has a plurality of housing spaces 14A to 14D between a circumferential direction of respective projected portions by alternately arranging projected portions 12A and 12B radially facing inward on an inner periphery of a pulley 2 (outer circular body) and projected portions 13A and 13B radially facing outward on an outer periphery of a rotor shaft 3 (inner circular body). Springs 4A, 4B, 4C, and 4D varying spring constants in response to their expansion and contraction are stored in the housing spaces. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a power transmission device such as a pulley unit. This type of power transmission device can be installed in, for example, an engine crankshaft or auxiliary machinery driven from the crankshaft via a transmission belt. Examples of the auxiliary machines include an automobile alternator, an air conditioner compressor, a water pump, and a cooling fan.

  When the rotational power of the engine is transmitted from the crankshaft (drive side) to the auxiliary machine (driven side) via the transmission belt, the transmission belt slips due to fluctuations in the rotational speed of the crankshaft, and noise is generated. Tend to occur. This will be described an alternator, which is one of the auxiliaries for example. When the engine is used as a driving source, the rotation speed of the crankshaft always varies during the rotation due to the operation process of the engine. On the other hand, since the rotor of the alternator has a large rotational inertia, inertia torque is applied to the rotor. For this reason, when the rotor of the alternator is driven by a crankshaft with fluctuations in rotational speed, the transmission belt loosens and changes tension, causing tension fluctuations. On the transmission belt, the rotor inertia torque is generated. As a result, slippage occurs in the transmission belt, and noise tends to occur or durability tends to decrease.

Therefore, as a conventional technique, convex portions are respectively provided at circumferential positions on the inner peripheral surface of the pulley around which the transmission belt is wound and the outer peripheral surface of the rotor shaft connected to the rotor of the alternator so as to be integrally rotatable, An elastic body such as a spring is arranged as a power transmission medium member in a space where both convex portions oppose each other in the circumferential direction, and the belt does not slip with respect to the pulley due to fluctuations in belt tension due to the elasticity of the elastic body. Thus, there has been proposed a power transmission device that can suppress or eliminate the occurrence of abnormal noise on the belt (see, for example, Patent Document 1). However, in the power transmission device according to the above proposal, even if a spring is provided, the rotation fluctuation absorbing function of the spring is lost in the usage mode such as when starting the engine or sudden acceleration, and the belt may slip or the like. In some cases, the spring was subjected to an impact load and was damaged.
JP 2002-303333 A

  The present invention provides a power transmission device that can maintain the function of a spring even in the above-described use mode, suppress the occurrence of slipping on the belt, and prevent the spring from being subjected to an impact load and effectively prevent the damage. It is to provide.

  A power transmission device according to the present invention is a power transmission device that transmits rotational power between both inner and outer rings arranged concentrically, and a radially inward convex portion on an inner peripheral surface of the outer ring, A plurality of storage spaces are formed between the circumferential directions of the respective convex portions by providing radially outward convex portions on the outer circumferential surface of the inner ring body so as to be alternately arranged in the circumferential direction. It is characterized in that a spring whose spring constant changes according to expansion and contraction is housed as a medium member for transmitting power between the bodies.

  Preferred examples of the spring include, for example, a taper coil spring, a barrel coil spring, an unequal pitch spring, a parent-child spring composed of at least two types of spring parts having different spring constants, a spring in which a part of the spring part is solidified with resin, and the like. Including. Further, not only a metal but also a resin spring is included. The shape of the spring is not limited as long as it has a function as a spring.

  When the power transmission device of the present invention is applied to a pulley unit, for example, when a pulley as an outer ring is driven via a belt from the crankshaft side of the engine, a rotor shaft as an inner ring via the spring is driven. Rotates. In a situation where the belt tension fluctuates and the rotor shaft cannot follow the tension fluctuation due to its inertia torque, the belt tension fluctuation is received by the compression and extension of the spring. There is no need to slip. This suppresses or eliminates the occurrence of abnormal noise on the belt.

  By the way, when a spring having a constant spring constant is used as a medium member for power transmission, there is a case where the spring is broken. Therefore, the present inventors diligently studied the cause of the spring breakage as follows. That is, the phenomenon that the breakage of the spring occurs particularly frequently in frequent repetitions such as engine starting and rapid acceleration was observed. The cause is that when the pulley is rapidly rotated through the belt at the time of engine start-up or sudden acceleration, the rotor shaft has a large inertia torque, so that an impact load is applied to the spring. In this case, since the spring constant of the spring is constant, each spring part comes into close contact with each other, and the elasticity of the whole spring is lost and the rigidity rapidly rises. As a result, it was clarified that the function of the spring was suddenly lost, the belt slipped, abnormal noise was generated, and the spring was damaged by the impact load. Therefore, in the present invention, a spring whose spring constant changes according to expansion and contraction is stored in the storage space. According to the present invention, when the engine is started or suddenly accelerated, the spring constant of the spring changes, and as a result, the spring portion of the entire spring does not abruptly adhere and the rigidity does not increase abruptly. The rigidity gradually increases, the function of the spring is maintained to prevent the belt from slipping, etc., and the impact load on the spring is not applied and the spring can be effectively prevented from being damaged. Became.

  According to the present invention, in the power transmission device that transmits rotational power between the inner and outer rings, the spring whose spring constant changes according to the expansion and contraction is stored in the storage space. Even if the relative rotational speed difference increases rapidly, the spring does not need to be subjected to an impact load, which makes it possible to effectively prevent the spring from being damaged. Also, when the outer ring is a driving ring, the inner ring is a driven ring, and a pulley unit configuration in which a belt is wound around the outer ring, the function of the spring is maintained, the belt slips, Or it becomes possible to prevent the generation of abnormal noise.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the accompanying drawings. In this embodiment, the power transmission device is applied to a pulley unit used for an auxiliary machine of a vehicle. 1 is a side sectional view showing the overall configuration of the pulley unit, and FIGS. 2 to 4 are front sectional views from the same position in FIG. 1, and FIG. 2 is when the spring is not loaded (no load). 3 is a cross-sectional view of the spring when a light load is applied, and FIG. 4 is a cross-sectional view of the spring when a heavy load is applied. FIG. 5 is a diagram in which the horizontal axis represents the twist angle of the pulley (the relative rotational speed difference between the pulley and the rotor shaft), and the vertical axis represents the load (torque) applied to the spring.

  The pulley unit 1 of the embodiment shown in these figures is a pulley 2 as an outer ring and an inner ring that is arranged on the inner peripheral side of the pulley 2 and transmits rotational power between the pulley 2. The spring 4A, 4B, 4C, 4D as a medium member for transmitting power from the pulley 2 to the rotor shaft 3 disposed in the middle in the axial direction between the rotor shaft 3 and the pulley 2 and the rotor shaft 3 Rolling bearings 5 and 6 comprising lubricant-sealed deep groove ball bearings disposed between both axial ends of the pulley 2 and the rotor shaft 3 are provided. The rolling bearings 5 and 6 are interposed one by one on both sides in the axial direction in the annular space between the pulley 2 and the rotor shaft 3, respectively, an outer ring 7, an inner ring 8, a plurality of balls 9, respectively. This is a general deep groove ball bearing composed of a crown-shaped cage 10 to be held and a seal ring 11.

  Convex portions 12A and 12B (drive-side convex portions) projecting inward in the radial direction are provided at several circumferential positions in the middle in the axial direction of the inner peripheral surface of the pulley 2, preferably at two locations facing each other at 180 degrees. . On the outer peripheral surface of the pulley 2, a wavy groove for winding the transmission belt 6 is formed.

  The drive-side convex portions 12A and 12B are formed on the inner peripheral surface of the pulley 2 so as to protrude radially inwardly at intervals of 180 ° in the circumferential direction, and the inner peripheral surfaces of the drive-side convex portions 12A and 12B are rotors. The outer periphery of the shaft 3 can be slidably contacted.

  The rotor shaft 3 is connected to, for example, a rotating shaft of an auxiliary machine provided in an automobile and an engine crankshaft 15 so as to be integrally rotatable. Convex portions (driven-side convex portions) 13A and 13B projecting radially outward are provided at several circumferential positions in the middle of the outer peripheral surface of the rotor shaft 3, preferably at two positions facing each other at 180 degrees. Yes. The driven-side convex portions 13A and 13B are formed to protrude every 180 ° on the outer peripheral surface of the rotor shaft 3 so as to be disposed between the driving-side convex portions 12A and 12B.

  In the opposed annular space between the pulley 2 and the rotor shaft 3, between the respective opposed portions in the circumferential direction of the respective convex portions 12A, 12B on the pulley 2 side and the respective convex portions 13A, 13B on the rotor shaft 3 side (four locations in the figure) Storage spaces 14A, 14B, 14C, and 14D are formed between the two. In each of the storage spaces 14A, 14B, 14C, and 14D, springs 4A, 4B, 4C, and 4D that are power transmission mediating members are stored. Each of the springs 4A, 4B, 4C, and 4D has an elliptical cross section stored in a compressed state.

  The springs 4A, 4B, 4C, and 4D are spring constant variable springs that are tapered at equal intervals and tapered, and the spring constants are variable according to the amount of expansion and contraction. The circumferentially wound end portions of the springs 4A, 4B, 4C, and 4D are in contact with the inner wall surfaces of the convex portions 12A, 12B, 13A, and 13B that are spring seats.

  In the pulley unit 1 having the above configuration, when the belt 8 rotates with the rotation of a crankshaft (not shown), the pulley 2 is rotated by the rotation. Then, the rotor shaft 3 rotates by receiving rotational power from the pulley 2 via the springs 4A, 4B, 4C, and 4D. In this case, as the pulley 2 rotates clockwise in the figure, the drive-side convex portions 12A and 12B of the pulley 2 approach the driven-side convex portions 13A and 13B, respectively, and are stored in the storage spaces 14A and 14C. The rotor shaft 3 rotates while the springs 4B and 4D stored in the storage spaces 14B and 14D extend while the 4A and 4C are compressed. When the crankshaft rotates and the rotation speed of the pulley 2 fluctuates, the springs 4A, 4B, 4C and 4D are compressed and expanded according to the fluctuation, and the fluctuation is transmitted to the rotor shaft 3. Can be suppressed.

  Since the springs 4A, 4B, 4C, and 4D exhibiting the above behavior are tapered, the large-diameter side spring portion is softer than the small-diameter side spring portion. Therefore, when a load in the compression direction is applied, the large-diameter side spring portion The spring constant changes as it is compressed and closely adhered. Therefore, in such springs 4A, 4B, 4C, 4D, as shown in FIG. 2, the relative rotational speed difference between the pulley 2 and the rotor shaft is zero, and the springs 4A, 4B, 4C, 4D are compressed in the compression direction. As shown in FIG. 3, the pulley 2 rotates in the clockwise direction from the no-load state where no load is applied, and the relative rotational speed difference between the rotor shaft 3 and the springs 4A and 4C is loaded in the compression direction. As shown in FIG. 4, a light load is applied lightly, and the relative rotational speed difference becomes excessive, resulting in a heavy load applied to the springs 4A, 4C with a heavy load in the compression direction. In the no-load state, none of the springs 4A, 4B, 4C, 4D is subjected to compression or expansion from the natural expansion / contraction state. In the light load state, the springs 4A and 4C are compressed from the natural expansion and contraction state, and the large-diameter soft spring portion that contacts the inner wall surface of the convex portions 12A and 12B comes into close contact with the windings and loses elasticity. It becomes a state. The springs 4B and 4D are extended from a naturally stretched state. In the heavy load state, the springs 4A and 4C are further compressed from the naturally stretched state, and the spring portion on the end winding side that comes into contact with the inner wall surface of the convex portions 12A and 12B is in close contact with several more turns and loses elasticity. Become. The springs 4B and 4D are further extended from the naturally stretched state. When the pulley 2 rotates in the counterclockwise direction relative to the rotor shaft 3 and the relative rotational speed difference between the pulley 2 and the rotor shaft 3 increases, the illustrated explanation is omitted. This is the opposite relationship.

  The behavior of the springs 4A, 4B, 4C, and 4D will be further described with reference to FIG. 5. FIG. 5A shows a case where a conventional spring having a constant spring constant is used as a power transmission medium member. (B) has shown the case where the spring with a variable spring constant of this invention is used as an intermediate member of power transmission. 5 (a) and 5 (b), the horizontal axis indicates the twist angle of the pulley 2 (the relative rotational speed difference between the pulley 2 and the rotor shaft 3), and the vertical axis indicates the load (torque) applied to the spring. . When a conventional spring having a constant spring constant is used, as shown by a characteristic line C2 in FIG. 5A, when the torsion angle of the pulley 2 reaches a constant value α, an excessively large load (impact load) is applied to the spring. ). As a result, the function of the spring is temporarily lost, causing the belt to slip or generate abnormal noise, and the spring is more likely to break. On the other hand, when a spring having a variable spring constant is used as in the present invention, the spring is applied even if the twist angle of the pulley 2 is large, as indicated by the characteristic line C in FIG. The load increases with a gentle curve, and no impact load is applied to the spring. Therefore, in the present invention, even if the twist angle of the pulley 2 is rapidly increased, the loss of the function of the spring is not prevented, and the slipping of the belt and the generation of abnormal noise can be suppressed, and the spring is damaged. The fear is reduced, and the reliability as a power transmission medium member in the power transmission device is increased. Note that, as indicated by characteristic lines C0 and C1 in FIG. 5B, by appropriately setting the rate at which the spring constant of the spring changes according to expansion and contraction, it can be applied to various load modes on the spring. .

Side surface sectional drawing which shows the whole structure of the pulley unit which concerns on the best form of this invention Front sectional view of the pulley unit shown in FIG. Front sectional view of the pulley unit shown in FIG. Front sectional view of the pulley unit shown in FIG. (A) The figure which shows the spring load characteristic with respect to the twist angle of the pulley at the time of using the conventional spring, (b) The figure which shows the spring load characteristic with respect to the twist angle of the pulley at the time of using the spring of this invention

Explanation of symbols

2 Pulley (outer ring)
3 Rotor shaft (inner ring)
4A-4D Spring 12A, 12B Drive side convex part 13A, 13B Driven side convex part 14A-14D Storage space

Claims (1)

  A power transmission device that transmits rotational power between both inner and outer rings arranged concentrically, with a radially inward convex portion on the inner peripheral surface of the outer ring and a diameter on the outer peripheral surface of the inner ring. Protrusions facing outward in the circumferential direction are arranged alternately in the circumferential direction to form a plurality of storage spaces between the circumferential directions of the respective projections, and mediating power transmission between the two rings in the storage space A power transmission device comprising a member that houses a spring whose spring constant changes according to expansion and contraction.

Images