Abstract:
An object of the present invention is to provide a chain guide which has low noise and low vibration even when being brought into contact with a chain running at high speed, and to provide a chain tensioner device using the chain guide. A chain guide base provided along the running direction of a chain is integrally attached to a tensioner plunger that presses the chain guide base against the chain side so as to increase the weight of the chain guide itself to reduce vibration.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a chain guide which presses an endlessly connected chain and thereby gives tension to the chain so as to prevent the slacking of the chain, and also relates to a chain tensioner device. 
       BACKGROUND ART 
       [0002]    A chain tensioner device is provided with chain guides which are brought into contact with middle portions of a chain endlessly provided around drive and driven sprockets and running at high speed, and is configured to press at least one of the chain guides against the chain in the direction substantially perpendicular to the running direction of the chain, and to thereby apply tension to the chain so as to prevent the chain from being slacked. The chain tensioner device is used for a timing chain, or the like, of a valve driving device of an engine. 
         [0003]    The chain guide is configured to guide the chain while being in contact with the chain, and hence sliding resistance is generated due to friction between the chain guide and the chain, causing a problem of an increased noise and mechanical loss. 
         [0004]    Known techniques for suppressing the noise and mechanical loss of the chain guide include those described in Patent Literature 1 and Patent Literature 2. The chain guides described in Patent Literature 1 and Patent Literature 2 are formed in a curved shape along the running direction of the chain, in which rollers are arranged at a sliding-surface portion which is brought into contact with the chain, and the rollers are rolled by being pressed against the chain running at high speed, and thereby the sliding resistance is reduced. 
       CITATION LIST 
     Patent Literature 
       [0000]    
       
         Patent Literature 1: Japanese Patent Laid-Open No. H09-236157 A 
         Patent Literature 2: Japanese Patent Laid-Open No. 2010-180900 A 
       
     
       SUMMARY OF INVENTION 
     Technical Problem 
       [0007]    Meanwhile, the chain moves on the chain guide at high speed while vibrating, and hence the vibration is transmitted to an engine via the chain guide, which results in a problem that the sound level of the vibration becomes high. 
         [0008]    As a countermeasure to reduce vibration transmitted to the chain guide, it is conceivable to increase the weight of the chain guide so as to increase the inertia force. 
         [0009]    However, the increase in the weight of the chain guide itself results in an increase in the weight of the system as a whole, which is not desirable from a viewpoint of the improvement in fuel economy. 
         [0010]    Accordingly, in order to solve the above described problems, an object of the present invention is to obtain a chain guide having large inertia force and little vibration, without increasing the weight of a system as a whole, and to obtain a chain tensioner device using the chain guide. 
       Solution to Problem 
       [0011]    In order to solve the above-described problems, according to the present invention, a tensioner plunger is integrally attached to a chain guide base in such a manner that the inertia force of the chain guide is increased and vibration of a chain guide is reduced without increasing the weight of a system as a whole. 
         [0012]    A plurality of rollers, which are brought into contact with an endlessly connected chain, can be arranged on the chain guide base. 
         [0013]    The roller may be composed of a support shaft, opposite ends of which are supported by the chain guide base, and a roller bearing which includes an outer ring provided on the outer peripheral surface of the support shaft. Further, the roller may include an iron outer ring which covers the outer periphery of the outer ring and which is brought into contact with the chain. 
         [0014]    As the roller bearing, it is possible to use a roller bearing composed of a steel outer ring having inward-extending flange sections at opposite ends thereof, and a roller provided with a retainer and incorporated in the outer ring. 
         [0015]    The steel outer ring is formed by press-forming but may also be formed by cut-forming. 
         [0016]    As for the hardness of the iron outer ring, it is preferred that an outer ring having hardness higher than the hardness of the chain is used so as to make it difficult for the outer ring to wear even when the outer ring is brought into contact with the chain running at high speed. 
         [0017]    As the material of the iron outer ring, it is preferred to use a material, such as SUJ2 and SCM, which can be subjected to hardening treatment. 
         [0018]    It is preferred that the iron outer ring has a thickness of 1 mm or more in order to prevent the deformation thereof and to improve the mechanical strength thereof. 
         [0019]    It is desirable that the iron outer ring has a generating line shape of a barrel shape or a straight shape in order to reduce sliding resistance against the chain. 
         [0020]    It is preferred that minute depressions and projections are formed on the surface of the iron outer ring, in order to improve the retaining performance of lubricating oil. 
         [0021]    Further, as hardening treatment, nitriding treatment may be applied to the surface of the iron outer ring. 
         [0022]    In order to reduce vibration and to achieve silence, it is desirable that the roundness of the iron outer ring is 20 μm or less. 
         [0023]    The chain guide according to the present invention may be a chain tensioner device that is arranged at a middle portion of the endlessly connected chain to give tension to the chain by using a tensioner plunger integrally attached to the chain guide base. 
       Advantageous Effects of Invention 
       [0024]    In the chain guide according to the present invention, the tensioner plunger is integrally attached to the chain guide base, and hence the weight of the chain guide is increased by the weight of the tensioner plunger. Therefore, the inertia force of the chain guide is increased in correspondence with the increase in the weight, and thereby the vibration of the chain guide is reduced. 
         [0025]    Even when the weight of the chain guide as a whole is increased, the weight of the vehicle as a whole is not changed as compared with the case where the tensioner plunger is arranged on the engine side, and hence the fuel economy is not deteriorated. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0026]      FIG. 1  is a perspective view showing an embodiment of a chain guide according to the present invention. 
           [0027]      FIG. 2  is a plan view of the chain guide of  FIG. 1  viewed from the chain side. 
           [0028]      FIG. 3  is a front view of the chain guide of  FIG. 1 . 
           [0029]      FIG. 4  is a plan view showing a state where rollers are removed from the chain guide of  FIG. 1 . 
           [0030]      FIG. 5  is a sectional view taken in line A-A in  FIG. 4 . 
           [0031]      FIG. 6  is a partially enlarged view of  FIG. 5 . 
           [0032]      FIG. 7  is a transverse sectional view showing an embodiment of a chain guide according to the present invention. 
           [0033]      FIG. 8  is a transverse sectional view showing an embodiment of the chain guide according to the present invention. 
           [0034]      FIG. 9  is a transverse sectional view showing another embodiment of the chain guide according to the present invention. 
           [0035]      FIG. 10  is a front view showing an example of a chain tensioner device using the chain guide according to the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0036]    Embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Note that components, which are the same or equivalent to each other, are denoted by the same reference numeral or character in the drawings, and the description thereof is not repeated to avoid duplication of description. 
         [0037]    A chain guide according to an embodiment of the present invention is used, for example, for giving tension to a timing chain of an engine valve drive system. 
         [0038]    As shown in  FIG. 10 , a timing chain  1  is endlessly wound around a crank sprocket  2  attached to a crankshaft, a first cam sprocket  3  attached to a first cam shaft of a valve train, and a second cam sprocket  4  attached to a second cam shaft. 
         [0039]    A first chain guide  5   a  and a second chain guide  5   b  are respectively arranged on the timing chain  1  between the crank sprocket  2  and the first cam sprocket  3 , and on the timing chain  1  between the crank sprocket  2  and the second cam sprocket  4  so as to prevent the timing chain  1  from being slackened. 
         [0040]    The first chain guide  5   a  is configured such that one longitudinal end side thereof is supported by a rotary shaft  6  so as to be rotatable with respect to an engine, and such that the other longitudinal end side thereof is rocked by a tensioner plunger  7  so as to give tension to the timing chain  1 . 
         [0041]    The second chain guide  5   b , whose opposite longitudinal ends are fixed by mounting shafts  8  with respect to the engine, guides the tensioned timing chain  1  so that the timing chain  1  is not slackened. 
         [0042]    The first chain guide  5   a  and the second chain guide  5   b  are different from each other only in that, while the first chain guide  5   a  is rocked by the tensioner plunger  7  with respect to the engine, the second chain guide  5   b  is not rocked and fixed with respect to the engine, and hence have the same basic structure for guiding the timing chain  1 . Note that the chain guides  5   a  and  5   b  are also referred to as a chain lever. 
         [0043]    The chain guide  5   a  is configured such that a tensioner plunger  7  is integrally attached to a guide base  9  formed in a curved shape along the timing chain  1 . 
         [0044]    As shown in  FIG. 5 , the tensioner plunger  7  includes a cylinder chamber  7   a , a piston  7   b  which is provided slidably in the cylinder chamber  7   a , and a return spring  7   c  which is inserted into the piston  7   b  and which presses the piston  7   b  in the outer direction. 
         [0045]    The cylinder chamber  7   a  is provided therein with a pressure chamber  7   d  which is located on the depth side of the piston  7   b , an oil supply passage  7   e  which supplies a hydraulic fluid to the pressure chamber  7   d , and a check valve  7   f  which prevents reverse flow of the hydraulic fluid. 
         [0046]    As a method for fixing the tensioner plunger  7  to the chain guide base  9 , it is possible to adopt a bonding method, a screw connection method, and the like, in addition to a method in which an annular fixing step section  10  configured to be fitted to the cylinder chamber  7   a  is provided on the bottom surface of the guide base  9 , and in which the cylinder chamber  7   a  is press-fitted into the fixing step section  10 . 
         [0047]    When the guide base  9  is formed, the cylinder chamber  7   a  may be attached to the guide base  9  by insertion molding. 
         [0048]    The chain guide base  9  is composed of a pair of side plate members  9   a , and pillar members  9   b  connecting the side plate members  9   a.    
         [0049]    Through holes  11  are respectively provided at opposite longitudinal ends of each of the side plate members  9   a . A shaft (not shown) is inserted into the through hole  11 , so as to be fixed to, for example, an inner wall of an engine cover. 
         [0050]    One longitudinal end side of the first chain guide  5   a  is supported by the rotary shaft  6  so as to be rotatable with respect to the engine, and the other longitudinal end side thereof is rocked by the tensioner plunger  7  to adjust tension of the timing chain  1 . 
         [0051]    The pair of side plate members  9   a  have a predetermined interval therebetween in the width direction, and the plurality of rollers  12  which are brought into contact with the timing chain  1  are arrayed between the side plate members  9   a . The rollers  12  may be arrayed at a uniform pitch along the side plate member  9   a  having a curved shape, or the pitches between the rollers  12  may be changed so that more of the rollers  12  are arranged on the entrance side in the running direction of the timing chain  1 . 
         [0052]    Support recesses  14 , which support opposite ends of a support shaft  13  of the roller  12 , are respectively provided in the mutually facing wall surfaces of the side plate members  9   a.    
         [0053]    As shown in  FIG. 4 ,  FIG. 5  and  FIG. 6 , each of the support recesses  14  is composed of an insertion recess  14   a  having an opening in the side-plate-member end surface on the side of the timing chain  1 , and a fixing recess  14   b  connected to the insertion recess  14   a  and having a circular arc shape into which the end portion of the support shaft  13  is fitted. Each of opposite ends of the support shaft  13  of the roller  12  is inserted from the insertion recess  14   a  into the fixing recess  14   b , so as to be supported by each of the side plate members  9   a.    
         [0054]    As shown in  FIG. 5 , a plurality of the support recesses  14  are arrayed along the curved shape of the side plate member  9   a , and the pillar member  9   b  is arranged between the support recesses  14 . 
         [0055]    As shown in the enlarged view of  FIG. 6 , the insertion recess  14   a  has a wide opening section a and is formed in a tapered shape, the width of which is gradually reduced from the opening section a to the position of the fixing recess  14   b . Further, the width dimension of an insertion port b, located at the position at which the insertion recess  14   a  is connected to the fixing recess  14   b , is smaller than the diameter φ of the fixing recess  14   b  having the circular arc shape. 
         [0056]    The fixing recess  14   b  having the circular arc shape is formed to have the diameter φ smaller than the diameter of the support shaft  13  so that the support shaft  13  is press-fitted into the fixing recess  14   b.    
         [0057]    Further, as shown in  FIG. 1  and  FIG. 2 , the support recess  14  is formed in the side plate member  9   a  in a non-penetrating state. Thereby, the shaft direction movement of the support shaft  13  inserted into the support recess  14  is regulated. 
         [0058]    In the present embodiment, the side plate member  9   a  and the pillar member  9   b  are formed integrally by resin molding using, for example, polyamide (PA) 46 or polyamide (PA) 66 which are polymers obtained by polycondensation of diaminobutane and adipic acid. Further, it is possible to use a material obtained by combining glass fiber or carbon fiber with PA46 or PA66 in order to increase the mechanical strength. 
         [0059]    When the side plate member  9   a  and the pillar member  9   b  are formed of resin, the weight of the guide base  9  can be reduced. Further, as the resin which forms the side plate member  9   a  and the pillar member  9   b , resin having high heat conductivity can also be used for dissipating the frictional heat. 
         [0060]    Note that, other than resin, the side plate member  9   a  and the pillar member  9   b  can also be formed, for example, by casting using a light metal, such as aluminum and magnesium. In this case, it is desirable that the side plate member  9   a  and the pillar member  9   b  are integrated with a tensioner plan jack. 
         [0061]    The roller  12  may be composed of the support shaft  13  and a roller bearing having a steel outer ring  12   a  as shown in  FIG. 7 , or may also be configured such that, as shown in  FIG. 8 , an iron outer ring  12   d  which is brought into contact with the timing chain  1  is arranged to cover the outer peripheral surface of the steel outer ring  12   a.    
         [0062]    The roller bearing is a radial roller bearing composed of the steel outer ring  12   a  having inward-extending flange sections at opposite ends thereof, and a roller  12   c  provided with a retainer  12   b  and incorporated in the steel outer ring  12   a.    
         [0063]    The outer ring  12   a  can be formed by press-forming or cut-forming. 
         [0064]    When the outer ring  12   a  is formed by press forming, it is preferred that, after the retainer  12   b  and the roller  12   c  are incorporated into the outer ring  12   a , the inward-extending flange sections are respectively formed at opposite ends of the outer ring  12   a  by edge bending processing, and that the outer ring  12   a  is then heat treated after the assembly. 
         [0065]    Further, when the hardness of the outer ring  12   a  or the iron outer ring  12   d  is set higher than the hardness of the timing chain  1 , the wear of the outer ring  12   a  or the iron outer ring  12   d  can be prevented. 
         [0066]    As a material of the outer ring  12   a  or the iron outer ring  12   d , a material, such as SUJ2 and SCM, which can be subjected to hardening treatment by heat treatment, is used. 
         [0067]    In order to improve the retaining performance of lubricating oil, minute depressions and projections may be formed on the surface of the outer ring  12   a  or the iron outer ring  12   d.    
         [0068]    Further, the surface of the outer ring  12   a  or the iron outer ring  12   d  may be subjected to nitriding treatment. 
         [0069]    In order to reduce contact resistance with the timing chain  1 , it is desirable that the surface of the outer ring  12   a  or the iron outer ring  12   d  has a generating line shape of a barrel shape or a straight shape. 
         [0070]    In order to reduce vibration and to achieve silence, it is desirable that the roundness of the outer ring  12   a  or the iron outer ring  12   d  is 20 μm or less. 
         [0071]    Further, from a viewpoint of mechanical strength, it is preferred that the thickness of the outer ring  12   a  or the iron outer ring  12   d  is 1 mm or more. 
         [0072]    The rollers  12   c  are held by the retainers  12   b  in the circumferential direction at predetermined intervals therebetween. As the retainer  12   b , a V-shaped retainer having a V-shaped pillar section is used. When the retainer  12   b  is used, it is possible to prevent the skewing of the roller  12   c  and to prevent the end surface of the roller  12   c  from being brought into direct contact with the flange section of the outer ring  12   a . Further, it is possible to prevent the wear of the side plate member  9   a . Note that the roller bearing having a roller structure without using the retainer  12   b  may also be adopted. 
         [0073]    Next, in order to attach the roller  12  to the side plate members  9   a  facing each other, the roller  12  into which the support shaft  13  is fitted is first prepared as shown in  FIG. 5 . Further, each of opposite ends of the support shaft  13  of the roller  12  is arranged to face the insertion recess  14   a  of the support recess formed in each of the mutually facing wall surfaces of the side plate members  9   a , and is then dropped into the insertion recess  14   a , so as to be inserted into the fixing recess  14   b  from the insertion recess  14   a . In the present embodiment, the opening section a is formed to be wide, and the insertion recess  14   a  is formed to have a tapered shape. Therefore, when the support shaft  13  is inserted, the support shaft  13  can be easily guided from the opening section a to the circular arc-shaped fixing recess  14   b  through the insertion port b. 
         [0074]    In the above-described embodiment, the diameter φ of the circular arc-shaped fixing recess  14   b  is formed to be smaller than the diameter of the support shaft  13 , and hence the support shaft  13  is press-fitted and attached to the fixing recess  14   b . As a result, it is possible to suppress the rotation of the support shaft  13 . In addition, the width of the insertion port b connected to the fixing recess  14   b  is formed to be smaller than the diameter φ of the circular arc-shaped fixing recess  14   b , and hence the insertion port b performs a function of preventing the coming-off of the support shaft  13 . Further, the support recess  14  is formed so as not to penetrate the side plate member  9   a , and hence the support shaft  13  inserted into the support recess  14  can be prevented from moving in the shaft direction. 
         [0075]    In the state where the support shafts  13  of the roller  12  are respectively fitted into the support recesses  14  of the mutually facing side plate members  9   a , the outer periphery surface of the roller  12  is lower than the end surface of the side plate member  9   a  as shown in  FIG. 1 ,  FIG. 3 ,  FIG. 4 ,  FIG. 7  and  FIG. 8 . Thereby, the timing chain  1  is guided between the mutually facing wall surfaces of the side plate members  9   a  while being brought into contact with the iron outer ring  12   d , so that the running timing chain  1  is prevented from coming off from the mutually facing wall surfaces of the side plate members  9   a.    
         [0076]    Further, it is desirable that each height of the end surface of the side plate member  9   a  and the roller  12  is lower than the position of a connection pin  1   b  mutually connecting plates  1   a  constituting the timing chain  1  as shown in  FIG. 7  or  FIG. 8 . When each height of the end surface of the side plate member  9   a  and the roller  12  is higher than the position of the connection pin  1   b  mutually connecting the plates  1   a  constituting the timing chain  1 , the connection pin  1   b  is brought into contact with the mutually facing wall surfaces of the side plate members  9   a , and hence such configuration is not preferred. 
         [0077]    Next,  FIG. 9  is a transverse sectional view showing a chain guide  5   a  according to another embodiment of the present invention. In this embodiment, components common to those of the above-described embodiments are denoted by the same reference numerals and reference characters, and the description thereof is omitted, and only different portions are described. In this embodiment, as shown in  FIG. 9 , an oil hole  15  is provided at the center portion of the support shaft  13 , and a discharge hole  15   a  for discharging oil is provided at a position opposite to the timing chain  1 . Further, a hole  16  connected to the oil hole  15  is provided in the side plate member  9   a . When the oil hole  15  is provided in this way, it is possible to supply oil to the inside of the bearing. Further, it is also possible to dissipate heat. It is preferred that the discharge hole  15   a  of the oil hole  15  is formed in the direction opposite to the timing chain  1  as described above. Thereby, oil is smoothly supplied to the inside of the bearing. Further, when the oil hole  15  is provided, the support shaft  13  is formed in a hollow shape, so that the weight of the chain guide  5  is reduced. 
         [0078]    Further, in addition to the engine timing chain, the chain guide  5   a  according to each of the embodiments of the present invention can give tension to various driving chains, and can also reduce mechanical loss. 
         [0079]    Further, as shown in  FIG. 10 , a chain tensioner device using the chain guide  5   a  according to the present invention is composed of the first chain guide  5   a  having one end provided with the through hole  11  into which the rotary shaft  6  is inserted, and having the other end side which is rocked by the tensioner plunger  7 , and the second chain guide  5   b  having opposite ends which are respectively fixed by the mounting shafts  8  with respect to the engine. With the chain tensioner device, the mechanical loss and weight of the engine timing chain are reduced, so that the fuel consumption rate can be improved. 
         [0080]    Note that the timing chain  1  can be used for any of a roller chain and a silent chain. 
         [0081]    Further, in the above embodiments, an example is shown in which the side plate member  9   a  and the pillar member  9   b  are formed integrally with each other, but each of the side plate member  9   a  and the pillar member  9   b  may be formed as a separated body. 
         [0082]    Further, in the above embodiments, an example is shown, in which a chain guide composed of arraying a plurality of rollers is used, but a chain guide, in which no roller is used, may be integrally attached to a tensioner plunger as described in the prior art of Patent Literature 1. 
         [0083]    Further, in the above embodiments, a hydraulic tensioner plunger is described, but a mechanical tensioner plunger using a screw or a spring may also be integrally attached to the chain guide. 
       INDUSTRIAL APPLICABILITY 
       [0084]    The chain guide according to the present invention is effectively used in a mechanism which gives tension to a driving chain of an engine, and the like. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           1  Timing chain 
           2  Crank sprocket 
           3  First cam sprocket 
           4  Second cam sprocket 
           5   a  First chain guide 
           5   b  Second chain guide 
           6  Rotary shaft 
           7  Tensioner plunger 
           7   a  Cylinder chamber 
           7   b  Piston 
           7   c  Return spring 
           7   d  Pressure chamber 
           7   e  Oil supply passage 
           7   f  Check valve 
           8  Mounting shaft 
           9  Chain guide base 
           9   a  Side plate member 
           9   b  Pillar member 
           10  Fixing step section 
           11  Through hole 
           12  Roller 
           12   a  Outer ring 
           12   b  Retainer 
           12   c  Roller 
           12   d  Iron outer ring 
           13  Support shaft 
           14  Support recess 
           14   a  Insertion recess 
           14   b  Fixing recess 
           15  Oil hole 
           15   a  Discharge hole 
           16  Hole