Abstract:
Low pressure fuel led from a fuel tank to a fuel injection pump is pressurized and sent out to a common rail that accumulates the pressurized fuel therein. A one-way valve that allows the low pressure fuel led from the fuel tank to flow into the fuel injection pump and prevents a fuel flow in a reverse direction is installed in the fuel injection pump. A supporting member for supporting a spring that biases a valve member in a direction to close the one-way valve is coupled to the valve member without using a rigid mechanical connection. The biasing force of the spring is received by a wide contacting surface of the supporting member, thereby reducing abrasion wear of the contacting surface.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
         [0001]    This application is based upon and claims benefit of priority of Japanese Patent Application No. 2001-364152 filed on Nov. 29, 2001, the content of which is incorporated herein by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to a fuel injection pump having an one-way valve for supplying fuel into a pressurizing chamber and to a method of assembling the one-way valve.  
           [0004]    2. Description of Related Art  
           [0005]    A fuel injection system including a common rail and an injection pump for supplying pressurized fuel into an internal combustion engine is known hitherto. The fuel injection pump pressurizes fuel in a pressurizing chamber according to rotation of its driving shaft. Fuel pressurized to a predetermined level is sent out to the common rail from the pressurizing chamber. The injection pump includes a one-way valve that allows fuel to flow into the pressurizing chamber from a fuel tank while preventing fuel from flowing back into the fuel tank.  
           [0006]    An example of a conventional one-way valve used in the fuel injection pump is shown in FIGS. 7A and 7B. A spring  102  is disposed between a valve body  101  and a valve member  100 . The one-way valve is closed when the valve member  100  seats on a valve seat  103  formed on the valve body  101 . The spring  102  biases the valve member  100  in a direction to close the one-way valve. To support the biasing spring  102  between the valve body  101  and the valve member  100 , a ring-shaped washer  104  is provided at an upper end of the valve member  100 . The upward movement of the washer  104  is restricted by an E-shaped ring  105  which is fixed to the valve member  100 . Alternatively, the upward movement of the washer  104  is restricted by a stopper press-fitted to the valve member  100 .  
           [0007]    In a process of assembling the conventional one-way valve, the E-shaped ring  105  or the stopper has to be fixed to the valve member  100 . Accordingly, a certain time is required in the assembling process for fixing the E-shaped ring  105  or the stopper. A contacting area between the E-shaped ring  105  and the valve member  100  is small as shown in FIG. 7B, and the biasing force of the spring  102  has to be received by the small contacting area. Therefore, the contacting area between the E-shaped ring  105  and the valve member  100 , including portion where the washer  104  contacts the E-shaped ring  105 , tends to wear due to abrasion during a long time operation of the one-way valve.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an improved one-way valve in which the abrasion wear is suppressed. Another object of the present invention is to provide an improved process of assembling the one-way valve.  
           [0009]    A fuel injection pump driven by an automotive engine pressurizes low pressure fuel led from a fuel tank and sends out pressurized fuel to a common rail. The pressurized fuel accumulated in the common rail is injected form fuel injectors into the engine in a controlled manner. A one-way valve that allows fuel to flow only in one direction is installed in the fuel injection pump. The low pressure fuel led from the fuel tank flows into a pressurizing chamber in the fuel injection pump through the one-way valve. The pressurized fuel is prevented from flowing back by the one-way valve. The pressurized fuel is sent out to an outlet passage connected to the common rail.  
           [0010]    The one-way valve is composed of a valve body, a valve member slidably coupled with the valve body, a biasing member such as a coil spring biasing the valve body in a direction to close the one-way valve, and a supporting member coupled to the valve member for supporting the biasing member between the valve body and the supporting member. The valve member is substantially rod-shaped and includes a head portion and a neck portion connected to the head portion, both of which serve to couple the supporting member to one end of the valve member. The supporting member is substantially disc-shaped. A through-hole and a groove, crossing each other, are formed in the supporting member.  
           [0011]    In assembling the one-way valve, the valve member is slidably coupled to the valve body, and then a cylindrical portion of the valve member is inserted into the biasing member. Then, the head portion of the valve member is inserted into the through-hole of the supporting member, and the supporting member is further pushed down against the biasing member, so that the head portion is separated from the through-hole and the neck portion is positioned in the through-hole. Then, the supporting member is rotated relative to the valve member so that the groove formed on the supporting member is aligned to the head portion of the valve member. Because the neck portion is made smaller than the through-hole, the neck portion is freely rotatable in the through-hole. Then, the force pushing down the supporting member against the biasing member is released thereby to engage the head portion with the groove. The head portion is retained in the groove, while the biasing force being applied between the valve member and the valve body. Thus, the process of assembling the one-way valve is completed.  
           [0012]    According to the present invention, abrasion wear in the one-way valve is suppressed because the biasing force of the spring is received by the supporting member having a wide surface. The assembling process of the one-way valve is simplified because the supporting member and the valve member are coupled to each other without using a mechanical connection such as staking.  
           [0013]    Other objects and features of the present invention will become more readily apparent from a better understanding of the preferred embodiment described below with reference to the following drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    [0014]FIG. 1A is a cross-sectional view showing a one-way valve according to the present invention;  
         [0015]    [0015]FIG. 1B is a plan view showing the one-way valve, viewed in a direction IB shown in FIG. 1A;  
         [0016]    [0016]FIG. 2 is a cross-sectional view showing an entire structure of a fuel injection pump in which the one-way valve is used;  
         [0017]    [0017]FIG. 3 is a cross-sectional view showing the fuel injection pump, taken along a line III-III shown in FIG. 2;  
         [0018]    [0018]FIG. 4A is a top view showing a valve member used in the one-way valve;  
         [0019]    [0019]FIG. 4B is a side view showing the valve member, viewed in a direction IVB shown in FIG. 4A;  
         [0020]    [0020]FIG. 4C is another side view showing the valve member, viewed in a direction IVC shown in FIG. 4A;  
         [0021]    [0021]FIG. 5A is a top view showing a supporting member to be coupled with the valve member;  
         [0022]    [0022]FIG. 5B is a cross-sectional view showing the supporting member, taken along a line VB-VB shown in FIG. 5A;  
         [0023]    FIGS.  6 A- 6 C show a process of assembling the one-way valve according to the present invention; and  
         [0024]    [0024]FIG. 7A is a cross-sectional view showing a conventional one-way valve; and  
         [0025]    [0025]FIG. 7B is a top view showing a washer and an E-shaped ring used in the conventional one-way valve, viewed in a direction VIIB shown in FIG. 7A. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0026]    A preferred embodiment of the present invention will be described with reference to the accompanying drawings. First, referring to FIGS. 2 and 3, an entire structure of a fuel injection pump  1  will be described. The fuel injection pump  1  is used in a fuel injection system having a common rail accumulating pressurized fuel therein.  
         [0027]    A housing  10  of the fuel injection pump  1  is composed of a housing body  11  and a pair of cylinder heads  12 ,  13 . The housing body  11  is made of aluminum, and the cylinder heads  12 ,  13  are made of iron. A cylinder  12   a , in which a plunger  20  is slidably disposed, is formed in the cylinder head  12 . Similarly, a cylinder  13   a , in which a plunger  20  is slidably disposed, is formed in the cylinder head  13 . A one-way valve  5  is installed at an outside portion of each cylinder  12   a ,  13   a . A pressurizing chamber  30  is formed in each cylinder  12   a ,  13   a  between the plunger  20  and the one-way valve  5 . In this embodiment, both cylinder heads  12 ,  13  are formed in a similar shape, but positions of fuel passages and screw holes formed therein are little different from each other. Both cylinder heads  12 ,  13 , however, may be formed in an exactly same shape.  
         [0028]    A driving shaft  14  is rotatably supported by the housing body  11  via a journal bearing  15 . A clearance between the driving shaft  14  and the housing body  11  is sealed by an oil seal  16 . As shown in FIG. 3, a cam  17  having a cylindrical outer periphery is formed on the driving shaft  14  in an eccentric relation to a rotational axis of the driving shaft  14 . The pair of plungers  20  are disposed in the respective cylinders  12   a ,  13   a  at positions, 180-degree opposing to each other. A cam ring  18  having a square outer periphery is rotatably coupled to the cam  17 , and a bushing  19  is interposed as a bearing between the cam  17  and the cam ring  18 . A plunger head  22  formed at one end of the plunger  20  slidably contacts one plane of the square outer periphery of the cam ring  18 . An inner space  11   a  of the housing body  11  is filled with fuel such as light oil, and the contacting surface between the plunger head  22  and the cam ring  18  is lubricated by the fuel.  
         [0029]    The pair of plungers  20  are reciprocally driven in the respective cylinders  12   a ,  13   a  according to rotation of the eccentric cam  17 . Fuel is sucked into the pressuring chamber  30  through the one-way valve  5  and pressurized therein. A spring  21  biases the plunger  20  toward the cam ring  18 . The cam ring  18  orbits around the eccentric cam  17  without rotating by itself according to the rotation of the driving shaft  14 , and thereby the plunger head  22  slidably moves on the plane surface of the cam ring  18 . Thus, the plunger  20  is reciprocally driven by the cam ring  18 . An outlet passage  32  extending in a direction perpendicular to each cylinder  12   a ,  13   a  is formed, so that it connects an outlet port  32   a  of the pressurizing chamber  30  to respective fuel passages  41   a ,  42   a  formed in connecting members  41 ,  42 .  
         [0030]    A fuel chamber  33  is formed in each cylinder head  12 ,  13  and is connected to the outlet port  32   a  through the outlet passage  32 . The fuel changer  33  is formed in a cylinder-shape having a diameter larger than that of the outlet passage  32 . An outlet one-way valve  44  is disposed in the fuel chamber  33 . Connecting members  41 ,  42  are screwed in respective mounting holes  34  formed in each cylinder head  12 ,  13  at a downstream end of the fuel chamber  33 . Fuel passages  41   a ,  42   a  each communicating with the fuel chamber  33  are formed in the respective connecting members  41 ,  42 . The respective fuel passages  41   a ,  42   a  extend substantially in line with the outlet passage  32 .  
         [0031]    The outlet one-way valve  44  disposed in the fuel chamber  33  is composed of a ball-shaped valve member  45 , a valve body  46  and a spring  47 . The spring  47  biases the valve member  45  toward the valve body  46 . The outlet one-way valve  44  allows the pressurized fuel to flow out of the pressurizing chamber  30  and prevents the fuel from flowing back into the pressurizing chamber  30 . The connecting members  41 ,  42  are connected to the common rail (not shown) through fuel pipes (not shown). Thus, the fuel pressurized in the pressurizing chamber  30  is supplied to the common rail.  
         [0032]    Now, referring to FIGS.  1 A- 1 B,  4 A- 4 C and  5 A- 5 B, a structure of the one-way valve  5  will be described in detail. As described above, the one-way valve  5  is disposed outside the pressurizing chamber  30  in each cylinder head  12 ,  13 . The one-way valve  5  is composed of a valve body  60 , a valve member  50 , a supporting member  80 , and a spring  70 . The valve member  50  is substantially rod-shaped and includes a head portion  51 , a neck portion  52 , a cylindrical portion  53 , and a flange portion  54 , all integrally formed in this order from its top side.  
         [0033]    The head portion  51  is formed substantially in a rectangular rod shape, as shown in FIGS.  4 A- 4 C. The head portion  51  is connected to the cylindrical portion  53  by the neck portion  52  extending in an axial direction of the cylindrical portion  53 . A top surface of the head portion  51  is a substantially rectangular shape, as shown in FIG. 4A, having a pair of straight long sides parallel to each other and a pair of circular short sides. The head portion  51  is connected to the cylindrical portion  53  by the neck portion  52 . As shown in FIG. 4A, a cross-sectional shape of the neck portion  52  on a plane perpendicular to the longitudinal axis of the valve member  50  has a pair of straight long sides and a pair of circular short sides. As shown in FIG. 4B, a width between the long sides of the neck portion  52  is the same as that of the head portion  51 . As shown in FIG. 4C, a dimension between the circular sides of the neck portion  52  is shorter than that of the head portion  51 .  
         [0034]    As shown in FIG. 1A, the flange portion  54  having a diameter larger than a diameter of the cylindrical portion  53  is formed at the bottom end of the valve member  50 . The flange portion  54  is disc-shaped and has a valve surface  55  that contacts a valve seat  61  formed on the valve body  60 . The cylindrical portion  53  slidably inserted in an inner bore  64  of the valve body  60 .  
         [0035]    The valve body  60  includes a fuel passage  62  that communicates with a fuel supply pump through a fuel supply passage (not shown) formed in each cylinder head  12 ,  13 . A bottom surface  63  of the valve body  60  faces the pressurizing chamber  30  thereby forming one end surface of the pressurizing chamber  30 . The inner bore  64  into which the valve member  50  is slidably inserted is formed in the valve body  60  in a direction perpendicular to the fuel passage  62 . The valve seat  61  is formed at a corner of a bottom opening of the valve body  60 . When the valve member  50  is reciprocally driven in the inner bore  64  of the valve body  60 , the valve surface  55  contacts the valve seat  61  or separated therefrom. As shown in FIG. 1A, the supporting member  80  is coupled to the upper end of the valve member  50  in a manner described later. The coil spring  70  is disposed between the supporting member  80  and a the valve body  60  in a compressed manner, so that a biasing force of the spring  70  is applied to the valve member  50  in a direction to establish contact between the valve surface  55  and the valve seat  61 .  
         [0036]    As shown in FIGS. 5A and 5B, the supporting member  80  is substantially disc-shaped. A through-hole  81  is formed through the supporting member  80  from its upper surface  83  to its bottom surface  84 , and a groove  82  is formed on the supporting member  80 . The shape of the through-hole  81  corresponds to the shape of the head portion  51  of the valve member  50 , and is made a little larger than that of the head portion  51  so that the head portion  51  is freely inserted into the through-hole  81 . The groove  82  is formed on the supporting member  80  crossing the through-hole  81 . The depth of the groove  82  is substantially the same as the thickness (a longitudinal dimension) of the head portion  51 , and its plane shape is the same as that of the through-hole  81 , so that the head portion  51  is retained in the groove  82 . The width of the through-hole  81  is made larger than the outermost diameter of the neck portion  52 , so that the neck portion is freely rotatable in the through-hole  81  when the neck portion  52  is inserted into the through-hole  81  in a manner described below.  
         [0037]    Now, referring to FIGS.  6 A- 6 C, a method of assembling the one-way valve  5  will be described. First, the valve member  50  is slidably inserted into the inner bore  64  of the valve body  60 . Then, as shown in FIG. 6A, an upper portion of the cylindrical portion  53  of the valve member  50  is inserted into the coil spring  70 . The head portion  51  of the valve member  50  is inserted through the through-hole  81  of the supporting member  80 . Then, the supporting member  80  is pushed down against the spring force of the coil spring  70 . Thus, the supporting member  80  is positioned at the neck portion  52  of the valve member  50 .  
         [0038]    Then, as shown in FIG. 6B, the valve member  50  is rotated relative to the supporting member  80  (the supporting member  80  may be rotated) to an angular position where the head portion  52  aligns with the groove  82 . Since the size of the neck portion  52  is smaller than that of the through-hole  81 , the neck portion can be freely rotated in the through-hole  81 . Then, as shown in FIG. 6C, the force pushing down the supporting member  80  against the spring  70  is released, thereby making the head portion  52  engage with the groove  82 . Thus, the relative rotation between the supporting member  80  and the valve member  50  is restricted. Since the supporting member  80  is pushed up by the spring  70 , a downward movement of the supporting member  80  is restricted. In this manner, the supporting member  80  is coupled to the upper end of the valve member  50 , and the assembling process of the one-way valve  5  is completed.  
         [0039]    Operation of the fuel injection pump  1  will be briefly described. According to rotation of the driving shaft  14 , the eccentric cam  17  is rotated. The cam ring  18  coupled to the cam  17  is driven eccentrically with respect to the axis of the driving shaft  14 . The plunger  20  in each cylinder  12   a ,  13   a  is reciprocally driven. As the plunger  20  is driven from a top dead center toward a bottom dead center, the inner space of the pressurizing chamber  30  is enlarged, and the pressure therein is decreased. The one-way valve  5  is opened against the basing force of the spring  70  by the negative pressure in the pressuring chamber  30  and a fuel pressure led from the fuel tank. Thus, the fuel is sucked into the pressuring chamber  30  according to the stroke of the plunger  20  toward the bottom dead center.  
         [0040]    Then, the plunger  20  is driven from the bottom dead center toward the top dead center, and thereby the pressuring chamber  30  is pressurized and the one-way valve  5  is closed by the pressure in the pressurizing chamber  30 . When the fuel pressure in the pressurizing chamber  30  becomes higher than a pressure in the fuel chamber  33  connected to the pressurizing chamber  30  through the outlet passage  32 , the outlet one-way valve  44  is opened. The pressurized fuel is supplied from the pressurizing chamber  30  to the common rail (not shown). The fuel pressurized in both cylinders  12   a ,  13   a  is supplied to the common rail together.  
         [0041]    The pressurized fuel supplied from the fuel injection pump  1  in a pulsating manner is accumulated in the common rail as fuel having a constant pressure. The fuel accumulated in the common rail is supplied to fuel injectors (not shown) which inject the fuel into the engine in a controlled manner.  
         [0042]    Advantages of the present invention described above will be summarized. The supporting member  80  is simply coupled to the upper portion of the valve member  50  by engaging the head portion  51  with the groove  82 . The spring  70  is supported and held between the valve body  60  and the supporting member  80 . In other words, the supporting member  80  is coupled to the valve member  50  without performing a staking process or the like. Therefore, the washer and the E-shaped ring or other fixing parts used in the conventional one-way valve can be eliminated, and the process of assembling the one-way valve  5  is simplified.  
         [0043]    The biasing force of the spring  70  is received by the bottom surface  84  of the supporting member  80 . Since the area of the bottom surface  84  is sufficiently large, abrasion wear of the supporting member  80  is prevented or suppressed. Therefore, the one-way valve  5  and the fuel injection pump  1  having such one-way valve can be used for a long time. Further, since the supporting member  80  is coupled to the valve member  50  by engaging the head portion  51  of the valve member with the groove  82  of the supporting member, the biasing force of the spring  70  applied to the supporting member  80  is received by the head portion  51  having a sufficiently large area. Therefore, abrasion wear occurring on the contacting surfaces of the head portion  51  of the valve member  5  and the groove  82  of the supporting member  80  can be reduced.  
         [0044]    Further, since the head portion  51  is retained in the groove  82  so that the upper surface of the head portion  51  becomes substantially equal level to the upper surface  83  of the supporting member  80 , as shown in FIG. 6C, the head portion  51  is prevented from being damaged.  
         [0045]    The present invention is not limited to the embodiment described above, but it may be variously modified. For example, the head portion  51  may be formed in other shapes such as a rectangular or half-circle shape. Though the groove  82  is formed to cross the through-hole  81  with a right angle in the foregoing embodiment, the groove  82  may be formed to cross the through-hole  81  with an appropriate angle.  
         [0046]    While the present invention has been shown and described with reference to the foregoing preferred embodiment, it will be apparent to those skilled in the art that changes in form and detail may be made therein without departing from the scope of the invention as defined in the appended claims.