JP5644465B2 - Gear support structure - Google Patents

Description

  The present invention includes a gear having a shaft insertion hole at the center, a gear shaft inserted into the shaft insertion hole of the gear and a bolt hole at the tip, and screwed into the bolt hole of the gear shaft. And a gear support structure having a gear fixing bolt for fixing the gear to the gear shaft.

  Noise (hereinafter referred to as engine noise) radiated from an engine (internal combustion engine) is a phenomenon that occurs for various reasons. In an engine that employs a gear (hereinafter referred to as a timing gear) for driving a valve train or an auxiliary machine, the movement of the gear is one of the causes of generating engine noise, and a component generated by the movement of the gear is called a gear sound. . There are mainly the following two types of mechanisms (1) and (2) for generating an excitation input that excites engine vibration that causes engine noise by the movement of the gear.

  (1) An excitation input is generated by the impact between the teeth of the gear pair due to the meshing.

  (2) When there is a difference in angular velocity (hereinafter referred to as relative angular velocity) between the meshing gear pairs, the teeth and teeth of the gear pair are moved by the teeth of one gear moving through a gap (backlash) with the teeth of the other gear. An excitation input is generated by a collision (rattle).

  In both cases (1) and (2), engine noise is radiated from the engine itself to which the vibration is transmitted through the gear itself or the gear shaft by the excited vibration.

  In commercial vehicle and industrial diesel engines, timing gears are often used from the viewpoint of durability and reliability. Diesel engines have excellent output torque characteristics, but they have a large variation in time (hereinafter referred to as torque variation) in the output torque cycle and a large driving torque of the valve system and auxiliary machinery. A relatively large relative angular velocity occurs. A gear sound due to rattle (gear rattle sound) is generated due to this relative angular velocity, and this gear rattle sound is subject to noise improvement as a major component of engine noise during high load operation with large torque fluctuations and idling. .

  When reducing gear rattle noise, as a measure based on the generation mechanism of the excitation input described above, backlash is reduced to reduce the collision energy of the gear teeth when relative angular velocity occurs, and the relative movement of the gear pair There is a scissors gear (for example, refer to Patent Document 1) for the purpose of suppressing itself.

Japanese Patent No. 3273720

  For the purpose of reducing gear rattle noise, it is desirable to reduce the backlash as much as possible. However, the reduction in backlash reduces the state of supply of lubricating oil to the gear tooth surface, resulting in friction loss (hereinafter referred to as engine friction). May get worse.

  The scissor gear is composed of a main gear and a sub gear. The teeth of the gear to be engaged are sandwiched between the teeth of the main gear and the sub gear using the elastic force of the spring applied to the sub gear. The relative movement of the pair is suppressed. Therefore, as in the case of the reduction of the backlash described above, the gear teeth are pressed by the deterioration of the supply state of the lubricating oil to the gear tooth surface, the increase of the contact area of the gear teeth, and the elastic force of the spring. As a result, the load on the tooth surface of the gear increases, which may increase engine friction.

  Therefore, the reduction of the gear rattle noise by the improvement measure (hereinafter referred to as the excitation source measure) that suppresses the phenomenon that excites the engine vibration as described above contributes to an increase in engine friction.

  Accordingly, an object of the present invention is to provide a gear support structure that can reduce noise emission from the engine body via a gear shaft bearing by reducing vibration transmission from the gear side to the gear shaft side. It is in.

  In order to achieve the above object, the present invention provides a gear having a shaft insertion hole at the center, a gear shaft inserted into the shaft insertion hole of the gear and having a bolt hole at the tip, and the gear. In a gear support structure having a gear fixing bolt that is screwed into a bolt hole of a shaft and fixes the gear to the gear shaft, in order to reduce vibration transmission from the gear side to the gear shaft side, A damping sleeve made of a material having a vibration damping rate higher than that of the gear and the gear shaft is sandwiched between the inner peripheral surface of the shaft insertion hole and the outer peripheral surface of the tip of the gear shaft. This is a gear support structure.

  The vibration damping sleeve may be made of a Mn—Cu—Ni—Fe based vibration damping alloy.

  ADVANTAGE OF THE INVENTION According to this invention, the gear support structure which can reduce the noise radiation from an engine main body via a gear shaft bearing can be provided by reducing the vibration transmission from the gear side to the gear shaft side. There is an excellent effect.

It is the schematic of the gear support structure which concerns on one Embodiment of this invention. It is explanatory drawing which shows the outline | summary of the measuring method of a vibration transfer characteristic. It is explanatory drawing which shows the improvement result of the vibration transmission characteristic by this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  In this embodiment, the present invention is applied to a camshaft drive gear of a diesel engine.

  A gear support structure 10 according to this embodiment is shown in FIG. As shown in FIG. 1, a shaft insertion hole for inserting (fitting) a camshaft (gear shaft) 13 into the central portion 12 of the camshaft drive gear (gear) 11 from the back surface 14 side of the camshaft drive gear 11. 15 is provided, and a bolt hole 17 for fixing the camshaft drive gear 11 is provided at the distal end portion 16 of the camshaft 13 inserted into the shaft insertion hole 15 of the camshaft drive gear 11. The camshaft drive gear 11 is fixed to the camshaft 13 from the axial direction by a gear fixing bolt 20 through a washer 19 in a state in which the camshaft drive gear 11 is non-rotatably engaged by the key 18. The camshaft 13 is rotatably supported by a camshaft bearing (see FIG. 2) provided on the engine body side. The gear fixing bolt 20 is screwed into the bolt hole 17 of the front end portion 16 of the camshaft 13 from the front surface 21 side of the camshaft drive gear 11. The camshaft drive gear 11, the camshaft 13, the key 18, the washer 19, and the gear fixing bolt 20 are made of, for example, an iron-based material.

  In the gear support structure 10 according to the present embodiment, the shaft insertion hole of the camshaft drive gear 11 is disposed between the inner peripheral surface of the shaft insertion hole 15 of the camshaft drive gear 11 and the outer peripheral surface of the tip portion 16 of the camshaft 13. 15 is a metal material (hereinafter referred to as a damping alloy: for example, a vibration damping factor) having a relatively high vibration damping rate such as Mn—Cu—Ni—Fe based so as to be in contact with the inner peripheral surface of 15 and the outer peripheral surface of the tip portion 16 of the camshaft 13 In this embodiment, a cylindrical (in this embodiment, cylindrical) sleeve (damping sleeve) 22 is sandwiched and vibrations are damped by this coupling surface (damping sleeve 22). The vibration transmission from the camshaft drive gear 11 side to the camshaft 13 side is reduced. That is, in the gear support structure 10 according to the present embodiment, the damping sleeve 22 is a metal material having a vibration damping rate higher than that of the camshaft drive gear 11, camshaft 13, key 18, washer 19, and gear fixing bolt 20. Consists of.

  Further, in the gear support structure 10 according to the present embodiment, a recess is formed in the inner peripheral surface of the shaft insertion hole 15 of the camshaft drive gear 11 along the circumferential direction, and the damping sleeve 22 is accommodated in the recess. The Further, in the gear support structure 10 according to the present embodiment, the slit 23 along the longitudinal direction of the damping sleeve 22 is used to fit the damping sleeve 22 to the tip portion 16 of the camshaft 13 to which the key 18 is attached. Is formed, and the damping sleeve 22 is C-shaped when viewed from the front.

  In short, in the gear support structure 10 according to the present embodiment, the camshaft 13 and the cam are not subjected to vibration source countermeasures that suppress the phenomenon of exciting engine vibration, but the vibration of the camshaft drive gear 11 that is excited by meshing or rattle. Improvement measures (transmission system countermeasures) in the transmission system aiming at reducing the vibration transmitted to the engine main body side through the shaft bearing and reducing noise emission from the engine main body side are taken.

  The vibration transmission characteristics between the camshaft drive gear 11 and the camshaft bearing (engine body side) were measured, and the improvement results of the vibration transmission characteristics according to the present invention were confirmed.

  An outline of a method for measuring vibration transfer characteristics is shown in FIG. In this measurement method, the measurement was performed with the camshaft 13 attached to the camshaft bearing of the cylinder head. However, in FIG. 2, only the camshaft bearing of the cylinder head is shown, and other cylinder head portions are not shown. doing.

  As shown in FIG. 2, the camshaft drive gear 11 is hit with an impact hammer with a force sensor, and the excitation force F [N] applied to the camshaft drive gear 11 is measured with the force sensor. At the same time, the vibration speed: v [m / s] is measured by a vibration sensor attached to the camshaft bearing. The output of each sensor (force sensor, vibration sensor) at this time was input as a voltage signal to a fast Fourier transform machine (FFT analyzer), and the frequency response function: v / F [(m / s) / N] was measured.

  FIG. 3 shows a comparison between the frequency response function in the state where the present invention is applied (after the countermeasure; with the damping sleeve 22) and the frequency response function in the state where the present invention is not applied (before the countermeasure; without the damping sleeve 22). Show. This frequency response function represents the vibration speed per unit input, and the level of the frequency response function becomes lower as the vibration is hardly transmitted. As shown in FIG. 3, by applying the present invention, the level of the frequency response function is lowered in a frequency region of 2 kHz (2000 Hz) or more, and the camshaft bearing (engine) from the camshaft drive gear 11 through the camshaft 13 is used. The effect of reducing vibration transmission to the main body side) can be confirmed.

  In short, according to the gear support structure 10 according to the present embodiment, vibration transmitted from the camshaft drive gear 11 to the engine body via the camshaft 13 and the camshaft bearing can be suppressed by improving the vibration transmission characteristics, Engine noise can be improved.

  Further, in the gear support structure 10 according to the present embodiment, the contact state of the tooth surfaces of the meshing gear pair does not change, so that it is possible to prevent the deterioration of the engine friction that is seen as a countermeasure against the excitation source due to the scissors gear mounting or the like.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, and various other embodiments can be adopted.

  For example, the present invention can be applied to apparatuses and devices that generate noise by applying vibration input to a gear by meshing or rattle, and generating vibrations through a gear shaft, even if it is not a diesel engine. For example, the present invention can be applied to a gasoline engine, a transmission, and the like.

10 Gear support structure 11 Camshaft drive gear (gear)
12 Gear center 13 Camshaft (Gear shaft)
15 Shaft insertion hole 16 Gear shaft tip 17 Bolt hole 20 Gear fixing bolt 22 Sleeve (damping sleeve)

Claims (2)

A gear with a shaft insertion hole in the center,
A gear shaft that is inserted into the shaft insertion hole of the gear and has a bolt hole at the tip;
A gear fixing bolt that is screwed into a bolt hole of the gear shaft and fixes the gear to the gear shaft;
A key that is inserted between the inner peripheral surface of the shaft insertion hole of the gear and the outer peripheral surface of the distal end portion of the gear shaft, and engages the gear with the gear shaft in a non-rotatable manner;
In order to reduce vibration transmission from the gear side to the gear shaft side, the gear and the gear are sandwiched between an inner peripheral surface of a shaft insertion hole of the gear and an outer peripheral surface of a front end portion of the gear shaft. A damping sleeve having a C-shaped front view made of a material having a higher vibration damping rate than the material of the shaft ;
Gearing support structure with.   The gear support structure according to claim 1, wherein the damping sleeve is made of a Mn—Cu—Ni—Fe based damping alloy.

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