Abstract:
This diesel engine is provided with pistons which slide, moving to and from the cylinder head, and which converts the sliding motion of the pistons into rotational motion of a crankshaft. This diesel engine is further provided with a supply pump which is driven by rotation of the crankshaft, a rail which stores fuel pumped from the supply pump, and injectors which inject the fuel supplied from the rail into the combustion chambers formed in the pistons, wherein the rail and the injectors are fixed to the cylinder head.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Technical Field 
         [0002]    The present invention relates to an art of a diesel engine. 
         [0003]    2. Background Art 
         [0004]    Conventionally, a diesel engine, in which fuel is injected to a combustion chamber provided in an upper surface of a piston and the fuel is burnt in the combustion chamber, is known. Such a diesel engine has a pressure accumulating fuel injector whose injection pattern can be set freely (hereinafter, referred to as “common rail system”). The common rail system includes a supply pump pressingly feeding the fuel, a rail storing the fuel with high pressure, and an injector injecting the fuel (for example, see the Patent Literature 1). 
         [0005]    Such a diesel engine has a metal pipe for supplying the fuel stored in the rail with high pressure to the injector (hereinafter, referred to as “injection pipe”). Namely, the rail is connected to the injector by the injection pipe. However, the injection pipe must bear the fuel with high pressure, whereby the injection pipe has high hardness and poor flexibility. Accordingly, a structure which prevents breakage of the injection pipe and looseness of attachment nuts of the injection pipe resulting from vibration and the like has been required. 
         [0006]    In such a diesel engine, operation state is changed corresponding to temperature of the fuel supplied to the injector. That is because a calorific value per unit volume of the fuel is reduced when the fuel is heated and expands and the calorific value per unit volume of the fuel is increased when the fuel is cooled and contracts. Especially, at the time of starting the engine in the cold district, there is a problem in that it takes time for the temperature of the fuel to reach a suitable value because the rail and the injection pipe are cooled. Accordingly, a structure in which the fuel temperature can be set quickly to the suitable value at the time of starting the engine in the cold district has been required. 
       PRIOR ART REFERENCE PATENT LITERATURE 
       [0007]    Patent Literature 1: the Japanese Patent Laid Open Gazette 2011-12573 
       BRIEF SUMMARY OF THE INVENTION 
     Problems to Be Solved by the Invention 
       [0008]    The purpose of the present invention is to provide a diesel engine which prevents breakage of an injection pipe and looseness of attachment nuts of an injection pipe resulting from vibration and the like. Furthermore, the purpose of the present invention is to provide a diesel engine in which fuel temperature can be set quickly to a suitable value at the time of starting the engine in the cold district. 
       Means for Solving the Problems 
       [0009]    A diesel engine according to the first mode of the present invention, which has a piston slid toward or oppositely to a cylinder head and converts sliding motion of the piston into rotational motion of a crankshaft, comprises a supply pump driven by the rotation of the crankshaft, a rail storing fuel fed pressingly from the supply pump, and an injector injecting the fuel supplied from the rail to a combustion chamber formed in the piston. The rail and the injector are fixed to the cylinder head. 
         [0010]    A diesel engine according to the second mode of the present invention is the diesel engine according to the first mode of the present invention, wherein the cylinder head has a substantially rectangular parallelepiped shape, the rail is formed substantially cylindrically, and the rail is fixed while an axis of the rail is in parallel to a lengthwise direction of the cylinder head. 
         [0011]    A diesel engine according to the third mode of the present invention is the diesel engine according to the first or second mode of the present invention, wherein the rail is supported by a bracket provided at a low position in a height direction of the cylinder head. 
       Effect of the Invention 
       [0012]    The present invention configured as the above brings the following effects. 
         [0013]    According to the first mode, the rail and the injector are fixed to the cylinder head. 
         [0014]    Accordingly, a vibration source of the rail  4  and a vibration source of the injector are the cylinder head, whereby breakage of the injection pipe and looseness of attachment nuts of the injection pipe can be prevented. 
         [0015]    According to the second mode, the rail is fixed while the axis of the rail is in parallel to the lengthwise direction of the cylinder head. Accordingly, any bending stress is not generated on the rail even if the cylinder head is heat-expanded, whereby the breakage of the injection pipe and the looseness of the attachment nuts of the injection pipe can be prevented. 
         [0016]    According to the third mode, the rail is supported by the bracket provided at the low position in the height direction of the cylinder head. Accordingly, the heat is transmitted suitably from the cylinder head to the rail, whereby the fuel temperature can be set to the suitable value quickly at the time of starting the engine in the cold district. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    [ FIG. 1 ]  FIG. 1  is a front view of a diesel engine. 
           [0018]    [ FIG. 2 ]  FIG. 2  is a right side view of the diesel engine. 
           [0019]    [ FIG. 3 ]  FIG. 3  is a schematic drawing of an operation mode of the diesel engine. 
           [0020]    [ FIG. 4 ]  FIG. 4  is a perspective view of the state in which a rail and an injector are attached to a cylinder head. 
           [0021]    [ FIG. 5 ]  FIG. 5  is a drawing viewed from a direction of an arrow X in  FIG. 4 . 
           [0022]    [ FIG. 6 ]  FIG. 6  is a drawing viewed from a direction of an arrow Y in  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    Next, an explanation will be given on a mode for carrying out the invention. 
         [0024]    Firstly, an explanation will be given on a diesel engine  100  briefly. 
         [0025]      FIG. 1  is a front view of the diesel engine  100 , and  FIG. 2  is a right side view thereof.  FIG. 3  is a schematic drawing of an operation mode of the diesel engine  100 . Arrows Fa in the drawing show flow direction of sucked air, and arrows Fe in the drawing show flow direction of exhaust gas. Arrows S in the drawing show sliding direction of a piston  13 , and arrows R in the drawing show rotation direction of a crankshaft  14 . 
         [0026]    The diesel engine  100  mainly includes an engine main part  1 , an intake path  2 , an exhaust path  3  and a common rail system  4 . 
         [0027]    The engine main part  1  generates rotation power by using expansion energy of combustion of fuel. The engine main part  1  mainly includes a cylinder block  11 , a cylinder head  12 , the piston  13  and the crankshaft  14 . 
         [0028]    In the engine main part  1 , a cylinder  11   c  provided in the cylinder block  11 , the piston  13  provided slidably inside the cylinder  11   c , and the cylinder head  12  arranged oppositely to the piston  13  constitute an operation chamber W. Namely, the operation chamber W means an inner space of the cylinder  11  c whose capacity is changed by sliding movement of the piston  13 . The piston  13  is connected via a connecting rod  15  to a pin part of the crankshaft  14  so that the crankshaft  14  is rotated by the slide of the piston  13 . A concrete operation mode of the engine main part  1  is discussed later. 
         [0029]    The intake path  2  guides air sucked from the outside into the cylinder  11   c.    
         [0030]    Namely, the intake path  2  guides the air sucked from the outside into the operation chamber W. The intake path  2  mainly includes an air cleaner (not shown) and an intake manifold  22  along a flow direction of the air. 
         [0031]    The air cleaner filters the sucked air with a filter paper, sponge or the like. The air cleaner filters the air so as to prevent foreign matters such as dust from entering the operation chamber W. 
         [0032]    The intake manifold  22  distributes the air filtered by the air cleaner to the operation chambers W. Since the diesel engine  100  is a multiple cylinder engine in which the plurality of the operation chambers W are provided, the intake manifold  22  is provided so as to cover an inlet port of an intake port  12 Ip provided in each of the operation chambers W. In the diesel engine  100 , since the inlet port of the intake port  12 Ip is provided in an upper surface of the cylinder head  12 , the intake manifold  22  is attached to the upper surface of the cylinder head  12 . 
         [0033]    The exhaust path  3  guides exhaust gas discharged from an inside of the cylinder  11  c to an exhaust port. Namely, the exhaust path  3  guides the exhaust gas discharged from the operation chambers W to the exhaust port. The exhaust path  3  mainly includes an exhaust manifold  31  and an exhaust purification device  32  along a flow direction of the exhaust gas. 
         [0034]    The exhaust manifold  31  gathers exhaust gas discharged respectively from the operation chambers W. Since the diesel engine  100  is the multiple cylinder engine in which the plurality of the operation chambers W are provided, the exhaust manifold  31  is communicated with an outlet hole of an exhaust port  12 Ep provided in each of the operation chambers W. In the diesel engine  100 , since an outlet hole of the exhaust port  12 Ep is provided in a side surface of the cylinder head  12 , the exhaust manifold  31  is attached to the side surface of the cylinder head  12 . 
         [0035]    The exhaust purification device  32  removes environmental load substances contained in the exhaust gas. A diesel oxidation catalyst (hereinafter, referred to as “DOC”) is provided in the exhaust purification device  32 . The DOC oxidizes and detoxifies CO (carbon monoxide) and HC (hydrocarbon), and oxidizes and removes SOFs (soluble organic fractions) which are particle matters. 
         [0036]    The common rail system  4  is a fuel injection device whose injection pattern can be set freely. The common rail system  4  mainly includes a supply pump  41 , a rail  42  and injectors  43 . 
         [0037]    The supply pump  41  feeds pressingly fuel discharged from a fuel tank to the rail  42 . The supply pump  41  is driven by rotation power of the crankshaft  14  transmitted via a plurality of gears. In detail, the supply pump  41  is driven by the rotation power of the crankshaft  14  transmitted via a crank gear  14 G, an idle gear  17 G, a cam gear  18 G and a pump gear  41 G. The supply pump  41  has a plunger slid by rotation of a driving shaft  41 S, and the fuel pressurized by the plunger is sent to the rail  42 . 
         [0038]    The rail  42  stores the fuel, which is fed pressingly from the supply pump  41 , at high pressure. The rail  42  is a metal pipe shaped substantially cylindrically. The rail  42  has a limiter valve and is designed so as to prevent pressure of the fuel from exceeding a predetermined value. A plurality of injection pipes  44  are attached to the rail  42  so as to guide the fuel to the injectors  43 . 
         [0039]    The injectors  43  inject suitably the fuel supplied from the rail  42 . Each of the injectors  43  is attached to the corresponding cylinder head  12  so that a tip of the injector  43  having an injection port is projected into the operation chamber W. The injector  43  has an armature driven by a piezo element or a solenoid for example, and can realize various injection patterns by controlling timing and term of the driving. 
         [0040]    Next, an explanation will be given on an operation mode of the diesel engine  100  in brief referring to  FIG. 3 . The diesel engine  100  is a 4-cycle engine in which an intake stroke, a compression stroke, an expansion stroke and an exhaust stroke are completed while the crankshaft  14  is rotated two times. 
         [0041]    In the intake stroke, an intake valve  12 Iv is opened and the piston  13  is slid downward (oppositely to the cylinder head  12 ) so as to suck air into the operation chamber W. As the above, in the diesel engine  100 , since the inlet port of the intake port  12 Ip is provided in the upper surface of the cylinder head  12 , the air flows from an upper side to a lower side of the cylinder head  12 . 
         [0042]    In the compression stroke, the intake valve  12 Iv is closed and the piston  13  is slid upward (toward the cylinder head  12 ) so as to compress the air in the operation chamber W. Since the intake port  12 Ip is closed by the intake valve  12 Iv, the air in the operation chamber W does not flow reversely. 
         [0043]    Subsequently, the fuel is injected from the injector  43  to the air whose temperature and pressure are increased by the compression. Then, the fuel is dispersed and evaporated in a combustion chamber C provided in an upper surface of the piston  13 , and mixed with the air and burnt. Accordingly, the diesel engine  100  shifts to the expansion stroke in which the piston  13  is slid downward again. 
         [0044]    In the expansion stroke, the piston  13  is pushed downward (oppositely to the cylinder head  12 ) with expansion energy generated by combustion of fuel. Flame formed in the combustion chamber C and the operation chamber W expands air so as to push down the piston  13 . In the expansion stroke, rotation torque is applied from the piston  13  via the connecting rod  15  to the crankshaft  14 . At this time, since kinetic energy is conserved by a flywheel  16  attached to the crankshaft  14 , the rotation of the crankshaft  14  is maintained (see  FIG. 2 ). Accordingly, the diesel engine  100  shifts to the exhaust stroke. 
         [0045]    In the exhaust stroke, an exhaust valve  12 Ev is opened and the piston  13  is slid upward (toward the cylinder head  12 ) so as to push out the burnt gas in the operation chamber W as the exhaust gas. As the above, in the diesel engine  100 , since the outlet hole of the exhaust port  12 Ep is provided in the side surface of the cylinder head  12 , the exhaust gas flows sideways from the lower side of the cylinder head  12 . 
         [0046]    Accordingly, the diesel engine  100  completes the intake stroke, the compression stroke, the expansion stroke and the exhaust stroke while the crankshaft  14  is rotated two times. By continuing the strokes in all the operation chambers W, the diesel engine  100  can be driven continuously. 
         [0047]    An explanation will be given on a structure of the diesel engine  100  in detail, and effect of the structure will be described. 
         [0048]      FIG. 4  is a perspective view of the state in which the rail  42  and the injector  43  are attached to the cylinder head  12 .  FIG. 5  is a drawing viewed from a direction of an arrow X in  FIG. 4 , and  FIG. 6  is a drawing viewed from a direction of an arrow Y in  FIG. 4 . 
         [0049]    The rail  42  is fixed to a bracket  12   b,  provided in a side surface of the cylinder head  12 , with a bolt B 1 . The bracket  12   b  is provided in not the side surface to which the exhaust manifold  31  is attached but the side surface opposite thereto. As the above, in the diesel engine  100 , since the intake manifold  22  is attached to the upper surface of the cylinder head  12  (see  FIGS. 1 and 2 ), the bracket  12   b  can be provided in the side surface to which the exhaust manifold  31  is not attached. 
         [0050]    The injector  43  is fixed by a holder  45  while being inserted into an injector hole of the cylinder head  12 . The holder  45  is fixed with a bolt B 2  while a hanging part of the holder  45  pinches a body of the injector  43  and a fulcrum part of the holder  45  contacts a head bolt Bh. Since the bolt B 2  is attached via a spherical washer, an attachment posture of the injector  43  is stable. 
         [0051]    Accordingly, the rail  42  and the injector  43  are fixed to the cylinder head  12 . 
         [0052]    Then, vibration generated by operation of the diesel engine  100  is transmitted to the rail  42  and the injector  43  substantially equally. The injection pipe  44  connecting the rail  42  to the injector  43  is vibrated integrally with them. 
         [0053]    For these reasons, in the diesel engine  100 , since a vibration source of the rail  42  and a vibration source of the injector  43  are the cylinder head  12 , breakage of the injection pipe  44  and looseness of attachment nuts  44 N of the injection pipe  44  can be prevented. 
         [0054]    In the configuration in which the intake manifold  22  is attached to the upper surface of the cylinder head  12  like the diesel engine  100 , it is important to fix the rail  42  to not the side surface to which the exhaust manifold  31  is attached but the side surface opposite thereto. That is because any part is not heated so that safety is improved and the structure supporting the rail  42  is simplified. This space which is easy to become a dead space can be used effectively. 
         [0055]    Next, an attachment posture of the rail  42  is limited. 
         [0056]    Generally, the cylinder head  12  has a substantially rectangular parallelepiped shape. Then, when the cylinder head  12  is heated by the operation of the diesel engine  100 , the cylinder head  12  is expanded greatly along a lengthwise direction L. On the other hand, the rail  42  is shaped substantially cylindrically. In the diesel engine  100 , the bracket  12   b  is provided so as to make an axis Ac of the rail  42  and the lengthwise direction L of the cylinder head  12  in parallel to each other. 
         [0057]    Accordingly, the rail  42  is fixed while the axis Ac thereof is in parallel to the lengthwise direction L of the cylinder head  12 . Then, load applied to the rail  42  by thermal expansion of the cylinder head  12  acts along the axis Ac of the rail  42 . 
         [0058]    For these reasons, in the diesel engine  100 , since any bending stress is not generated on the rail  42  even if the cylinder head  12  is heat-expanded, the breakage of the injection pipe  44  and the looseness of the attachment nuts  44 N of the injection pipe  44  can be prevented. 
         [0059]    In the diesel engine  100 , the bracket  12   b  is provided at a low position in a height direction H of the cylinder head  12 . That is because of the consideration for enabling fuel temperature to be set to a suitable value quickly at the time of starting the engine in the cold district. 
         [0060]    Accordingly, the rail  42  is supported by the bracket  12   b  provided at the low position in the height direction H of the cylinder head  12 . Then, heat generated in the operation chamber W can be transmitted quickly to the rail  42  and fuel in the rail  42  can be heated. 
         [0061]    For these reasons, in the diesel engine  100 , since the heat is transmitted suitably from the cylinder head  12  to the rail  42 , the fuel temperature can be set to the suitable value quickly at the time of starting the engine in the cold district. 
       INDUSTRIAL APPLICABILITY 
       [0062]    The present invention can be used for an art of a diesel engine. 
       Description of Notations 
       [0000]    
       
           100  diesel engine 
           1  engine main part 
           11  cylinder block 
           12  cylinder head 
           13  piston 
           14  crankshaft 
           2  intake path 
           3  exhaust path 
           31  exhaust manifold 
           4  common rail system 
           41  supply pump 
           42  rail 
           43  injector 
           44  injection pipe 
           44 N attachment nut 
           45  holder 
         Ac axis 
         Bh head bolt 
         B 1  bolt 
         B 2  bolt 
         L lengthwise direction 
         H height direction