Abstract:
An engine compartment cover for a work machine comprising left and right-hand side covers for covering the sides of an engine, and a hood for covering the top of the engine, which serves to enclose the engine and demarcate an engine compartment and which is capable of suppressing the noise at the operator&#39;s ear level caused by the engine operating noise passing through the engine compartment cover as far as possible, whereby the level of quietness in the operator cab can be improved. In the engine compartment cover for a work machine, the hood has a box-type structure comprising an exterior top plate, side plates surrounding the whole perimeter of the exterior top plate, and a bottom plate provided opposing the exterior top plate, and air inlet holes are provided in the side plates only, whilst an air outlet hole is provided in the bottom plate only, in such a manner that external air is drawn into the interior of the hood via the air inlet holes and air is introduced into the engine compartment via the air outlet hole.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to an engine compartment cover for a work machine which comprises left and right-hand side covers and an upper hood, and serves to demarcate an engine compartment, and more particularly, to an engine compartment cover provided with a ventilation opening for allowing air to circulate inside the engine compartment.  
           [0003]    2. Description of the Related Art  
           [0004]    For example, a tractor, bulldozer, or the like, which is one type of a work machine, comprises an engine and power train mounted on a main frame equipped with an undercarriage, and is also provided with an operator cab in which an operator (driver) can sit.  
           [0005]    Furthermore, the engine is covered by an engine compartment cover, and this engine compartment cover comprises a pair of left and right-hand side covers for covering the sides of the engine, and a hood for covering the top of the engine, and together with a front grille, and the like, this engine compartment cover serves to demarcate the engine compartment.  
           [0006]    Moreover, in the aforementioned engine compartment cover, a ventilation opening is provided in order to allow air to circulate inside the engine compartment, with the object of cooling the engine, and the like, a composition being adopted, for example, wherein external air is taken into the engine compartment via the front grille positioned on the front side thereof, and air is discharged from the engine compartment to the outside, via a ventilation opening provided in the hood of the engine compartment cover.  
           [0007]    In a composition in which a ventilation opening is provided in the hood of the engine compartment cover, as described above, the noise generated by the sound of the engine during operation travels from the inside of the engine compartment, through the aforementioned ventilation opening, and is radiated upwards from the engine compartment cover.  
           [0008]    On the other hand, in an earthmoving vehicle, such as a tractor, bulldozer, or the like, if the engine is mounted to the front side of the operator cab, then the hood of the engine compartment cover is laid out in such a manner that it only reaches to a position below the operator&#39;s line of sight, in order to ensure the field of vision of the operator sitting in the operator cab.  
           [0009]    Therefore, since the engine noise is radiated upwards from the ventilation opening provided in the hood of the engine compartment cover as described above, then the noise to which the operator sitting in the operator cab is exposed, in other words, the noise at the level of the operator&#39;s ears, is very loud, and therefore problems occur in that the working efficiency of the operator declines markedly due to the loss of quietness in the operator cab.  
           [0010]    The present invention was devised with the foregoing in view, an object thereof being to provide an engine compartment cover for a work machine whereby the noise reaching at the operator&#39;s ear level caused by engine noise passing through the engine compartment cover is suppressed as far as possible, thereby making it possible to enhance the level of quietness in the operator cab.  
         SUMMARY OF THE INVENTION  
         [0011]    The engine compartment cover for a work machine relating to one aspect of the present invention is an engine compartment cover for a work machine, comprising left and right-hand side covers covering sides of an engine, and a hood for covering a top of the engine, the engine compartment cover enclosing the engine and demarcating an engine compartment; wherein the hood has a box-type structure comprising an exterior top plate, side plates surrounding the whole perimeter of an exterior top plate, and a bottom plate opposing the exterior top plate, air inlet openings being provided only in the side plates, an air outlet opening being provided only in the bottom plate, and external air being drawn inside the hood via the air inlet openings and air being introduced into the engine compartment via the air outlet opening.  
           [0012]    According to the foregoing composition, since air inlet openings are provided only in the side plates of the hood, and since an air outlet opening is provided only in the bottom plate of the hood, in other words, since no opening for taking in or letting out air is provided in the exterior top plate of the hood, then although the engine noise inside the engine compartment is radiated in sideways directions via the air inlet openings in the hood, it is not radiated in an upward direction from the exterior top plate of the engine compartment cover.  
           [0013]    Therefore, according to the engine compartment cover for a work machine relating to the present invention, the noise at the operator&#39;s ear level caused by the engine operating noise passing through the engine compartment cover is suppressed as far as possible, and consequently, the level of quietness in the operator cab can be improved markedly.  
           [0014]    The engine compartment cover for a work machine relating to a second aspect of the present invention is the engine compartment cover for a work machine relating to the first aspect of the invention, wherein a guide duct for guiding air from the air outlet opening to a prescribed location is provided on the bottom plate of the hood.  
           [0015]    According to the foregoing composition, since no opening for taking in or letting out air is provided in the top of the hood, the noise at the operator&#39;s ear level is suppressed as far as possible; and the level of quietness in the operator cab is improved, in addition to which, since a guide duct is provided in the bottom plate of the hood, the external air can be guided reliably to a prescribed location inside the engine compartment, for example, to the radiator, or the like.  
           [0016]    The engine compartment cover for a work machine relating to a third aspect of the present invention is the engine compartment cover for a work machine relating to the first aspect of the invention, wherein sound insulating members for attenuating a noise radiated externally from the engine compartment are provided on the surfaces of components in the hood forming the passage of air from the outside to the engine compartment.  
           [0017]    According to the foregoing composition, since no opening for taking in or letting out air is provided in the top of the hood, the noise at the operator&#39;s ear level is suppressed as far as possible, and the level of quietness in the operator cab is improved, in addition to which, since the level of noise radiated in sideways directions from the air inlet openings is reduced, the noise at the operator&#39;s ear level caused by this noise being reflected upwards from its sideways direction is also suppressed, and furthermore, the ambient noise can also be reduced significantly. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    [0018]FIG. 1 is a side view of the overall composition of a bulldozer showing one embodiment of a work machine to which the present invention is applied;  
         [0019]    [0019]FIG. 2 is a conceptual view showing the layout of the engine, and the like, mounted in the bulldozer shown in FIG. 1;  
         [0020]    [0020]FIG. 3 is an oblique external view showing an engine compartment cover in the bulldozer in FIG. 1;  
         [0021]    [0021]FIGS. 4A and 4B are a top view and a bottom view showing the hood of the engine compartment cover in FIG. 3;  
         [0022]    [0022]FIGS. 5A, 5B and  5 C are a side view, a front view and a rear view showing the hood of the engine compartment cover in FIG. 3;  
         [0023]    [0023]FIG. 6 is a cross-sectional view along line VI-VI in FIG. 5A;  
         [0024]    [0024]FIG. 7 is a cross-sectional view along line VII-VII in FIG. 4A;  
         [0025]    [0025]FIG. 8 is a cross-sectional view along line VIII-VIII in FIG. 4A;  
         [0026]    [0026]FIG. 9 is a conceptual diagram showing the flow of air passing through the hood of the engine compartment cover in FIG. 3;  
         [0027]    [0027]FIGS. 10A, 10B and  10 C are a side view, a top view and a front view showing a side cover of the engine compartment cover in FIG. 3;  
         [0028]    [0028]FIG. 11 is a cross-sectional view along line XI-XI in FIG. 10A;  
         [0029]    [0029]FIG. 12 is a cross-sectional view along line XII-XII in FIG. 10A; and  
         [0030]    [0030]FIG. 13 is a conceptual diagram showing the flow of air passing through the side cover of the engine compartment cover in FIG. 3. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]    Below, the present invention is described in detail on the basis of the drawings which illustrate an embodiment.  
         [0032]    [0032]FIG. 1 to FIG. 13 show one embodiment in which the present invention is applied to an engine compartment cover of an earthmoving vehicle, being one type of a work machine, and more specifically, the engine compartment cover of a bulldozer.  
         [0033]    As shown in FIG. 1 and FIG. 2, the bulldozer (work machine)  1  has a front work tool (blade device)  1 A and a rear work tool (ripper device)  1 B fitted to a tractor  2  which forms the main body of the vehicle, and an engine E, and the like, is mounted in the front region of the main frame of the tractor  2  which is equipped with an undercarriage, whilst an operator cab  3  in which an operator can ride is provided in the rear region thereof.  
         [0034]    The engine E comprises, in addition to an engine main body Ea, an intake pipe Ei, an air cleaner Ec, a muffler Em and an exhaust pipe Ee, and the like, and it is accommodated inside an engine compartment  2   e  which is demarcated by an engine compartment cover  4 , as described hereinafter.  
         [0035]    Moreover, a radiator R and cooling fan F are provided to the front side of the engine E, and this radiator R and cooling fan F are accommodated inside a front grille  5  provided in front of the engine compartment cover  4 .  
         [0036]    Here, the engine compartment  2   e  of the tractor  2  is demarcated by the engine compartment cover  4 , together with the operator cab  3  which is positioned to the rear side of the engine compartment cover  4 , and the front grille  5  which is positioned to the front side thereof, the engine E being accommodated inside this engine compartment  2   e  without being exposed externally.  
         [0037]    As shown in FIG. 3, the engine compartment cover  4  is equipped with a hood  10  covering the top of the engine E (see FIG. 2), a side cover  20 R covering the right-hand side of the engine E and a side cover  20 L covering the left-hand side of the engine E.  
         [0038]    As shown in FIG. 3 to FIG. 8, the hood  10  comprises a top plate (outer top plate)  11  which forms the upper exterior of the engine compartment cover  4 , and the whole perimeter of this top plate  11  is surrounded by a left-hand side plate (side plate)  12 L, a right-hand side plate (side plate)  12 R, a front side plate (side plate)  12 F and a rear side plate ( 12 B).  
         [0039]    Moreover, the hood  10  comprises a bottom plate  13  which opposes the top plate  11 , and by assembling the top plate  11 , the left-hand side plate  12 L, the right-hand side plate  12 R, the front side plate  12 F, the rear side plate  12 B and the bottom plate  13  in the form of a box, the hood  10  is formed with an empty box-shaped structure.  
         [0040]    Intake holes  11   i  and exhaust holes  11   e  are formed in the top plate  11 , and intake holes  13   i  and exhaust holes  13   e  are formed in the bottom plate  13 , but when the engine compartment cover  4  is installed in the prescribed position (see FIG. 1), these intake holes  11   i,    13   i  and exhaust holes  11   e,    13   e  are closed off by the intake pipe Ei and the exhaust pipe Ee of the engine E (see FIG. 2).  
         [0041]    Air inlet openings  12 Li,  12 Li are formed in the left-hand side plate  12 L of the hood  10 , and air inlet openings  12 Ri,  12 Ri are formed in the right-hand side plate  12 R of the hood  10 . Punched metal  12   f  forming a filter for preventing infiltration of foreign material is installed respectively on the air inlet openings  12 Li and the air inlet openings  12 Ri.  
         [0042]    Moreover, an air outlet opening  13   o  is formed in the bottom plate  13  of the hood  10 , towards the front side thereof (towards the left-hand side in FIG. 6), and furthermore, a guide duct  14  is installed on the lower face of the bottom plate  13 , in such a manner that it surrounds the air exhaust outlet  13   o.    
         [0043]    The guide duct  14  serves to guide air from the air outlet opening  13   o  towards a prescribed location, which in the case of this embodiment, is the radiator R, and as shown in FIG. 9, it is provided in a position whereby, when the engine compartment cover  4  is installed in a prescribed position (see FIG. 1), it faces the vicinity of the radiator R, to the rear side thereof.  
         [0044]    Moreover, as shown in FIG. 6 to FIG. 9, sound absorbing sheets (sound insulating members)  15 ,  15 , . . . for attenuating the noise radiated externally from the engine compartment  2   e  (see FIG. 2) are attached to the lower face of the top plate  11  of the hood  10 , the upper face of the bottom plate  13 , and a portion of the inner face of the guide duct  14 , in other words, the surfaces of the components that form the air passage.  
         [0045]    The sound absorbing sheets  15  are made from a suitable material having desired sound insulating properties (sound absorbing properties and vibration damping properties), such as sheets of urethane foam, polyethylene foam, rubber sponge material, or non-woven fabric made of PET (polyethylene terephthalte), or the like.  
         [0046]    On the other hand, as shown in FIG. 3 and FIG. 10 to FIG. 13, the side cover  20 L in the engine compartment cover  4  has a side panel  21 L covering the left-hand side of the engine E, and this side panel  21 L is supported swingably with respect to the hood  10 .  
         [0047]    Moreover, an air inlet opening  21 Li is formed towards the front side of this side panel  21 L, and punched metal  21   f  forming a filter for preventing infiltration of foreign material is attached to this air inlet opening  21 Li.  
         [0048]    Furthermore, a guide duct  22 L is installed on the inner face of the side panel  21 L in such a manner that it surrounds the air inlet opening  21 Li, and this guide duct  22 L is provided in a position whereby, when the engine compartment cover  4  is installed in a prescribed position (see FIG. 1), it faces the vicinity of the radiator R, to the rear side thereof, as illustrated in FIG. 13.  
         [0049]    Sound absorbing sheet  23  made from a urethane foam sheet material, for example, is attached to a portion of the inner face of the guide duct  22 L, in other words, the surfaces of the component that form the air passage.  
         [0050]    On the other hand, as shown in FIG. 3 and FIG. 13, the side cover  20 R in the engine compartment cover  4  has a side panel  21 R covering the right-hand side of the engine E, and this side panel  21 R is supported swingably with respect to the hood  10 .  
         [0051]    Moreover, an air inlet opening  21 Ri is formed towards the front side of this side panel  21 R, and punched metal  21 f forming a filter for preventing infiltration of foreign material is attached to this air inlet opening  21 Ri.  
         [0052]    Furthermore, a guide duct  22 R is installed on the inner face of the side panel  21 R in such a manner that it surrounds the air inlet opening  21 Ri, and this guide duct  22 R is provided in a position whereby, when the engine compartment cover  4  is installed in a prescribed position (see FIG. 1), it faces the vicinity of the radiator R, to the rear side thereof, as illustrated in FIG. 13.  
         [0053]    Sound absorbing sheet  23  made from a urethane foam sheet material, for example, is attached to a portion of the inner face of the guide duct  22 R, in other words, the surfaces of the component that form the air passage.  
         [0054]    When the bulldozer  1  provided with the engine compartment cover  4  described above starts operation, along with the driving of the cooling fan F, outside air is drawn inside the hood  10  of the engine compartment cover  4  via the air inlet openings  12 Li and the air inlet openings  12 Ri, as indicated by the arrows, a, in FIG. 7 and FIG. 9, and the air subsequently discharged via the air outlet opening  13   o  is guided by the guide duct  14  towards the radiator R, as indicated by arrow b.  
         [0055]    Here, temperature rise in the cooling air is prevented, as far as possible, by guiding the external air to the radiator R via the interior of the hood  10  and the guide duct  14 , without exposing the air to the heat sources of the engine main body Ea and the muffler Em, and the like, and therefore, it is possible significantly to improve the cooling efficiency of the radiator R.  
         [0056]    Furthermore, in the side covers  20 L,  20 R of the engine compartment cover  4 , along with the driving of the cooling fan F, external air passes through the air inlet openings  21 Li,  21 Ri, as indicated by the arrows c in FIG. 13, and is guided to the radiator R by the guide ducts  22 L,  22 R.  
         [0057]    Here, temperature rise in the cooling air is prevented, as far as possible, by guiding the external air to the radiator R via the guide ducts  22 L,  22 R in the side covers  20 L,  20 R, without exposing the air to the heat sources of the engine main body Ea and the muffler Em, and the like, and therefore, it is possible significantly to improve the cooling efficiency of the radiator R.  
         [0058]    On the other hand, if noise is generated in association with the running of the engine E, whilst the bulldozer  1  is in an operating state, then noise that has infiltrated from the guide duct  14  and into the hood  10  of the engine compartment cover  4 , via the air outlet opening  13   o , will be radiated externally via the respective air inlet openings  12 Li and the air inlet openings  12 Ri.  
         [0059]    Here, in the hood  10  described above, since the air inlet openings  12 Li and the air inlet openings  12 Ri are provided respectively in the left-hand side plate  12 L and the right-hand side plate  12 R, then although the engine operating noise inside the engine compartment  2   e  is radiated in sideways directions via the air inlet openings  12 Li,  12 Ri, the engine operating noise inside the engine compartment  2   e  will not be radiated in an upward direction from the top plate  11  of the engine compartment cover  4 , because no openings for taking in or letting out air are provided in the top plate of the hood  10 .  
         [0060]    Therefore, the noise to which the operator, who is sitting in the operator cab  3  and has a line of sight positioned above the engine compartment cover  4 , is exposed, in other words, the noise at the operator&#39;s ear level is reduced as far as possible, and consequently, the level of quietness inside the operator cab  3  is markedly improved.  
         [0061]    Furthermore, in the hood  10  described above, since sound absorbing sheets  15 ,  15 , for attenuating noise are attached to the lower face of the top plate  11 , the upper face of the bottom plate  13 , and a portion of the inner faces of the guide duct  14 , in other words, the surfaces of the components that form the air passage, then the level of noise radiated in a sideways direction from the air inlet openings  12 Li,  12 Ri is decreased, and consequently, the noise at the operator&#39;s ear level caused by this noise being reflected upwards from its sideways direction is suppressed, in addition to which, the ambient noise level can also be reduced significantly.  
         [0062]    Here, in the hood  10  described above, since the sound absorbing sheet  15  can also be attached to the whole area of the inner faces of the left-hand side plate  12 L and the right-hand side plate  12 R, and the inner faces of the front side plate  12 F and the rear side plate  12 B, as well as the inner faces of the guide duct  14 , and thus the sound absorbing sheet  15  can be attached over a wide range to the surfaces of the components forming the air passage, in other words, since the sound absorbing sheet  15  can be attached over a wide range, then the noise suppression effects can be enhanced dramatically.  
         [0063]    Furthermore, it is also possible to attach sound insulating sheets  16 ,  16 , . . . made from a suitable sound insulating material, to the surfaces of the bottom plate  13  of the hood  10  and the guide duct  14  that face the engine compartment  2   e , as illustrated by the alternate long and two short dashes lines in FIG. 7 and FIG. 8, for example, in addition to the surfaces of the components that form the air passage.  
         [0064]    According to the composition described above, since the noise propagated to the hood  10 , and the like, from the interior of the engine compartment  2   e  is attenuated by the sound insulating sheets  16 ,  16 , . . . , then it is possible further to reduce the level of noise which escapes externally, via the hood  10 .  
         [0065]    Here, since the sound insulating sheets  16 ,  16  . . . are exposed directly to the heat of the engine E, desirably, they are made from a non-woven fabric of PET, or the like, which has excellent thermal resistance, and moreover, since the sound absorbing sheets  15 ,  15 , . . . attached to the surfaces of the components forming the air passage are not exposed directly to the heat of the engine E, then desirably, they are made from urethane foam, which has inferior thermal resistance but is less expensive.  
         [0066]    Furthermore, when the bulldozer  1  is operating, the noise generated by the operation of the engine E is radiated externally in sideways directions, from the respective guide ducts  22 L,  22 R in the side cover  20 L and the side cover  20 R of the engine compartment cover  4 , via the respective air inlet openings  21 Li,  21 Ri.  
         [0067]    Here, in the side covers  20 L,  20 R, since sound absorbing sheet  23  is attached to a portion of the inner faces of the guide ducts  22 L,  22 R, in other words, the surfaces of the components that form the air passage, then the level of noise radiated in a sideways direction from the air inlet openings  21 Li,  21 Ri is decreased, and consequently, the noise at the operator&#39;s ear level caused by this noise being reflected upwards from its sideways direction is suppressed, in addition to which, the ambient noise level can also be reduced significantly.  
         [0068]    Furthermore, in the side covers  20 L,  20 R, it is also possible to attach sound absorbing sheet  23  to the whole region of the inner faces of the guide ducts  22 L,  22 R, and by attaching sound absorbing sheet  23  over a wide range in this way, it is possible further to enhance the noise suppression effects.  
         [0069]    Furthermore, it is also possible to attach sound insulating sheets  24 ,  24 , . . . made from a suitable sound insulating material, to the surfaces of the side panels  21 L ( 21 R) and the guide ducts  22 L ( 22 R) in the side cover  20 L ( 20 R) that face the engine compartment  2   e , as illustrated by the alternate long and two short dashes lines in FIG. 11, for example, in addition to the surfaces of the components that form the air passage.  
         [0070]    According to the composition described above, since the noise propagated to the side covers  20 L,  20 R from the interior of the engine compartment  2   e  is attenuated by the sound insulating sheets  24 ,  24 , . . . , then it is possible further to reduce the level of noise which escapes externally, via these side covers  20 L,  20 R.  
         [0071]    The embodiment described above related to an example wherein the present invention is applied to a bulldozer, which is one type of an earthmoving vehicle, but the present invention may of course also be applied effectively to various types of construction vehicles other than a bulldozer, such as a hydraulic shovel, or the like, for example.  
         [0072]    Furthermore, the present invention may of course be applied effectively to various types of work machine, other than construction vehicles such as bulldozers, hydraulic shovels, or the like, which have an engine enclosed by an engine compartment cover, such as various types of agricultural vehicles, such as tractors, or the like, for example.