Abstract:
A scissors gear may include a main gear and a sub-gear co-axially combined by a scissors spring therebetween to integrally rotate, a first oil supply hole formed in the main gear or the sub-gear to supply oil from the outside, an oil groove formed in the sub-gear or the main gear to receive the oil by being selectively communicated with the first oil supply hole, and a check valve that is disposed in the main gear or the sub-gear to open/close the oil groove.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority from, Korean Patent Application Number 10-2008-0123135, filed on Dec. 5, 2008, the entire contents of which are incorporated herein for all purposes by this reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a scissors gear, particularly a scissors gear that effectively reduces vibration and noise using a damping force of oil. 
     2. Description of Related Art 
     In general, a gear assembly is a device that smoothly transmits rotational power using two gears engaged with each other and has been widely used because of high durability and a property of smooth power transmission. However, backlash should be provided for smooth engagement of the teeth of the two gears and rattling is generated by collision of the teeth due to the backlash while the gears rotate. 
     Scissors gears have been used to reduce the rattling. The scissors gear is applied to a driving gear or a driven gear and one gear is connected with the other gear by a scissors spring. Accordingly, when the teeth of a counterpart gear are engaged with the scissors gear, the teeth of the scissor gear are engaged with the teeth of the counterpart gear like scissors, such that backlash is removed and operational noise of the gears is reduced. 
     However, since two separate gears are connected only by a spring in scissors gears in the related art, they have a limit in achieving stable and excellent dynamic properties and reducing operational noise of the gears correspondingly. 
     The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art. 
     BRIEF SUMMARY OF THE INVENTION 
     Various aspects of the present invention are directed to provide a scissor gear that can effectively reduce vibration and noise of the scissors gear by improving dynamic properties of the scissors gear to apply a damping force of oil to the scissors gear. 
     In an aspect of the present invention, a scissors gear may include a main gear and a sub-gear co-axially combined by a scissors spring therebetween to integrally rotate, a first oil supply hole formed in the main gear or the sub-gear to supply oil from the outside, an oil groove formed in the sub-gear or the main gear to receive the oil by being selectively communicated with the first oil supply hole, and a check valve that is disposed in the main gear or the sub-gear to open/close the oil groove. 
     The check valve may be disposed to be biased against the oil groove by an elastic member and the check valve has an upward slope portion that opens the oil groove while the check valve is pushed upward by an oil pressure supplied from the first oil supply hole and a downward slope portion that closes the oil groove while the check valve is pressed downward by an oil pressure in the oil groove 
     The upward slope portion may be formed to face the first oil supply hole and the downward slope portion is formed at the opposite side of the upward slope portion. 
     The upward slope portion may be formed to be slanted with a predetermined acute angle toward the first oil supply hole. 
     The downward slope portion may be formed to be slanted with a predetermined obtuse angle toward the first oil supply hole. 
     A gear shaft may be fitted in the main gear and the sub-gear, and a second oil supply hole through which the oil is supplied from the outside and an oil channel for supplying the oil in the second oil supply hole into the first oil supply hole of the main gear are formed in the gear shaft, wherein the gear shaft is supplied with the oil from a main oil gallery of a cylinder head. 
     In another aspect of the present invention, the scissors gear may include a main gear and a sub-gear that are co-axially combined by a scissors spring to integrally rotate, a first oil supply hole formed in the main gear or the sub-gear to supply oil from the outside, an oil groove formed in the sub-gear or the main gear to receive the oil by being selectively communicated with the first oil supply hole, and a check valve that is disposed in the main gear or the sub-gear to open/close the oil groove and to be biased against the oil groove via an elastic member. 
     According to the scissors gear of the present invention, the check valve disposed in the main gear restricts of flow of the oil in the oil groove formed in the sub-gear while moving along the oil groove, such that a damping force generated in the this operation quickly absorbs and reduces vibration of the scissors gear. Therefore, it is possible to improve dynamic properties of the scissors gear and effectively reduce operational noise of the scissors gear. 
     The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description of the Invention, which together serve to explain certain principles of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing a scissors gear according to an exemplary embodiment of the present invention. 
         FIG. 2  is a perspective view showing a portion of a main gear according to an exemplary embodiment of the present invention. 
         FIG. 3  is a perspective view showing a sub-gear according to an exemplary embodiment of the present invention. 
         FIG. 4  is a perspective view of the scissors gear assembled, according to an exemplary embodiment of the present invention. 
         FIG. 5  is a cross-sectional view showing when a check valve according to an exemplary embodiment of the present invention opens an oil groove. 
         FIG. 6  is a cross-sectional view showing when the check valve according to an exemplary embodiment of the present invention closes the oil groove. 
         FIGS. 7 and 8  are views illustrating the operation of the check valve according to an exemplary embodiment of the present invention. 
         FIG. 9  is a cross-sectional view showing when a gear shaft is fitted in the scissors gear according to an exemplary embodiment of the present invention. 
     
    
    
     It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment. 
     In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims. 
     Referring to  FIG. 1 , a main gear  1  and a sub-gear  2 , which are separated into two parts, are combined by an arc-shaped scissor spring  3 . Both ends of a cut portion of scissors spring  3  have protrusions  3   a ,  3   b , respectively, in which one protrusion  3   a  is fitted in an assembly hole of main gear  1  and the other protrusion  3   b  is fitted in an assembly hole of sub-gear  2 , such that main gear  1  and sub-gear  2  are combined by scissors spring  3 . 
     As shown in  FIG. 2 , an oil supply hole  1   a  is formed in main gear  1  to supply oil from the outside. Oil supply hole  1   a  is grooved radially outward from the outer end of the inner circumference around which a gear shaft is fitted and a check valve mounting hole  1   b  is axially grooved adjacent to oil supply hole  1   a.    
     As shown in  FIG. 3 , an arc-shaped oil groove  2   a  is formed to be recessed in the axial direction on the boss of sub-gear  2  where the gear shaft is fitted. 
     Oil supply hole  1   a  of main gear  1  is positioned adjacent to a side of oil groove  2   a  of sub-gear  2  as shown in  FIG. 4 . 
     Alternatively, it may be possible to form an oil groove in main gear  1  and an oil supply hole in the sub-gear. 
     A spring  4   a  is inserted in check valve mounting hole  1   b  of main gear  1  and check valve  4  is elastically supported by spring  4   a  as shown in  FIG. 5 . Further, check valve  4  is inserted in oil groove  2   a  of sub-gear  2  to move along oil groove  2   a.    
     In the position shown in  FIG. 5 , oil supply hole  1   a  of main gear  1  is positioned to be communicated with oil groove  2   a  of sub-gear  2  and oil groove  2   a  is open by check valve  4  to supply oil. 
       FIG. 6  shows when oil supply hole  1   a  of main gear  1  is positioned not to be connected with oil groove  2   a  of sub-gear  2  and oil groove  2   a  is closed by check valve  4 . 
       FIGS. 7 and 8  are views showing in detail the operation of the check valve, in which oil supply hole  1   a  is positioned to be communicated with oil groove  2   a  to supply oil, and the check valve is pushed upward while compressing spring  4   a  by pressure of the oil that is applied to an upward slope portion  4   b  of check valve  4  in a first chamber  20  while the first chamber  20  is compressed when sub-gear  2  moves in the direction of an arrow, such that oil groove  2   a  is opened and oil is supplied into oil groove  2   a.    
     However, as shown in  FIG. 8 , when sub-gear  2  rotates in the direction of an arrow while oil is not supplied, with oil supply hole  1   a  positioned not to be connected with oil groove  2   a , the oil at the left of check valve  4  moves toward check valve  4 , such that the pressure of the oil is applied to a downward slope portion  4   c  of check valve  4  to press downward check valve  4  in a second chamber  30  while the second chamber  30  is compressed and oil groove  2   a  is correspondingly closed by the check valve. 
     Therefore, the oil at the left from the check valve in oil groove  2   a  cannot move and is pressurized, and on the contrary, the pressure applied as a damping force to the rotation of the sub-gear, such that it absorbs and attenuates vibration of the sub-gear. 
     Referring to  FIG. 9 , an oil supply hole  5   a  is radially formed through gear shaft  5  that is fitted in the scissors gear, oil supply hole  5   a  is communicated with an oil channel  5   b  axially formed in the gear shaft, and oil channel  5   b  is formed to be communicated with oil supply hole  1   a  of main gear  1 , such that oil can be supplied through an oil main gallery formed at a cylinder head. 
     The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.