Abstract:
An engine noise reduction device to reduce sound output from an engine compartment and supply cooling air to the engine compartment to increase cooling efficiency and prevent engine and component overheating. The device opposes a plurality of air inlets, to receive an air flow therefrom, and includes a split-type noise absorbing portion and a cell-type noise absorbing portion.

Description:
FIELD OF THE INVENTION 
     The present invention relates to an engine noise reduction device, and in particular, to an engine noise reduction device for a construction machine which further increases the quantity of air supplied to an engine compartment to prevent engine and equipment overheating. 
     BACKGROUND OF THE INVENTION 
     Conventionally, there have been various proposals regarding a noise absorbing device for reducing noise in an engine room. The following inventions are known as art close to the present invention: 
     (1) According to Japanese laid-open Patent No. 57-137616, cooling air discharged by a cooling fan of an engine passes through a sound deadening louver device of a radiator guard after cooling a radiator and is discharged into a space formed between the louver and a radiator silencer device. Part of the cooling air exhaust is discharged from an discharge port at the upper portion of the space, and the remaining portion of the exhaust is discharged to an engine air flow guiding passage of a dual structure connected to the lower portion of the space. A switch device is provided at the terminal end of the air flow guiding passage, and by operating an open-close plate, cooling air exhaust is returned to an engine room through an exit to enhance sound deadening effect, or cooling air exhaust is discharged to the outside to enhance cooling effect. 
     However, according to the above configuration, the sound deadening effect and the cooling effect are enhanced by operating the open-close plate in accordance with operational conditions; therefore, operation is troublesome. In addition, hot air is returned and circulated when the open-close plate is closed; thus, there is a disadvantage of reducing the cooling effect. 
     (2) According to Japanese Laid-open Patent No. 56-116520, each of a plurality of noise absorbing louvers is tilted so that the front edge thereof is higher than the rear edge thereof. As a result, a space between a pair of adjacent noise absorbing louvers form an air exhaust passage facing diagonally upward to the front of a vehicle. Thereby noisy air discharged from an engine room by a cooling fan is not discharged to the front of the vehicle but collides against the noise absorbing louvers once through a noise absorbing grille, and the noise and speed of the air is reduced. Thereafter, the noisy air is discharged along the passage to a portion above the vehicle. As a result, the noisy air discharged from the noise absorbing grille dose not scatter lightweight material such as fine coal, chips, or the like carried in the vehicle and placed in front of the noise absorbing grille. 
     However, according to the above configuration, each of the noise absorbing louvers is placed to face diagonally upward so that fine coal, chips, or the like are not scattered upward by the exhaust, but there is no particular advantage when it is applied to an air inlet portion. Especially it is difficult to apply this configuration to a vehicle with a structure which cannot secure a sufficient inlet area only with an air inlet portion in one direction and needs to provide air inlet portions in two different directions. 
     (3) According to Japanese Laid-open Utility Model No. 64-1150, both side portions of a plurality of noise absorbing louvers placed in parallel are respectively coupled with pins and the inclinations of the noise absorbing louvers are changed, thereby the space between adjacent louvers is adjustable. As a result, when a construction vehicle loses heat balance during operation, flow resistance of cooling air can be reduced by increasing the space between the noise absorbing louvers. When noises are to be reduced, the space can be reduced by tilting the noise absorbing louvers, and engine noises can be released upward. 
     However, according to the above configuration, it is necessary to operate the noise absorbing louvers respectively to reduce engine noise or to enhance engine cooling, thus the system is inconvenient. In addition, as in the previous invention, it is difficult to apply this configuration to air inlet portions in two different directions. 
     (4) Japanese Laid-open Patent No. 6-144022 provides a configuration of a traveling working vehicle in which exhaust from an opening portion of a radiator is discharged from an engine bonnet. A splitter sound deadening device is placed in close contact with the opening portion of the radiator and is attached at the engine bonnet side to prevent a cooling air flow from circulating in the engine bonnet. Moreover, the radiator is placed so that the axis of a cooling fan is at a position higher than the axis of a cooling pump so that the exhaust from the opening portion of the radiator is discharged lower than the splitter sound deadening device. 
     According to the above configuration, the splitter sound deadening device is in close contact with the opening portion of the radiator and is attached at the engine bonnet side to prevent a cooling air flow from circulating in the engine bonnet; therefore, it is difficult to apply this configuration to air inlet portions to take air in from two different directions. 
     Recently, ultra-small, revolving-type hydraulic shovels, which can revolve within the width of a crawler belt, are mainly used in operational sites. For these hydraulic shovels, the size of the upper revolving superstructure is reduced. Consequently, the volume of an engine room which houses an engine, a radiator, a fan, hydraulic instruments, and the like is decreased. In FIGS. 25 and 26, an upper revolving superstructure  151  is composed of a working machine  152 , a driver&#39;s cabin  153 , an engine room  111 , and the like, and can revolve within the width of a crawler belt  155 . In this downsized ultra-small, revolving-type hydraulic shovel  150 , a single intake port for supplying cooling air flow to cool a radiator (not illustrated) housed in the inner side of the engine room  111  and an engine (not illustrated) is too limited, and an insufficient quantity of cooling air flow would be supplied. Therefore, a device  110  for supplying air to an engine room having a plurality of air intake ports  122  and  127  supplies cooling air flow to the radiator to cool the engine. As a result, for a plurality of air intake ports  122  and  127 , air is mainly supplied through a counterweight  121  (composing the engine room  111 ) having the intake port  122 , and a shortage amount is supplied through the air intake port  127  extending through an engine hood  126  at the upper side of the engine room  111 . Alternatively, air is mainly supplied through the counterweight  121 , and a shortage amount is supplied from a space at an upper revolving superstructure frame  112  at the lower side of the engine room  111 . 
     However, in the hydraulic shovel  150  or the like, it is found that even if a plurality of intake ports  122  and  127  (which intersect at a right angle) are provided, the quantity of air supplied is not increased. Explaining, for example, with reference to FIG. 19, a change in the quantity of intake air is achieved by changing an opening area An of the auxiliary hood inlet port  127 , provided at an engine hood  126 , to take in the shortage air flow amount, while an opening area Ac at the major counterweight inlet port  122 , provided at the counterweight  121 , is fixed. As a result, as shown in FIG. 22, it is found that if auxiliary air quantity Va from the auxiliary hood inlet port  127  is increased, major air quantity Vm from the major counterweight inlet port  122  decreases following the increase, and total air quantity Vc as a whole increases only a little. On the other hand, if the opening area An of the auxiliary hood inlet port  127  is fixed and the opening area Ac of the major counterweight inlet port  122  is changed, the same result is obtained, specifically, the total air quantity Vc as a whole increases only a little. The reason for the above result is considered to be that the air from the major counterweight inlet port  122  and the air from the auxiliary hood inlet port  127  interfere with each other at a position where the respective air flows intersect. Consequently, such disturbance within the combined air flow prevents the total air quantity Vc of the two ports from increasing. 
     SUMMARY OF THE INVENTION 
     The present invention is made to eliminate the above disadvantages of the prior art, and its first object is to provide a noise absorbing device having greater sound deadening effect and greater cooling effect with smaller air flow resistance. A second object of the invention is to provide a device to supply air to an engine room of a construction machine which increases the quantity of air supplied from two air intake ports with a simple configuration and which effectively cools an engine room. 
     A first aspect of an air absorbing device of the present invention is a noise absorbing device which is placed at an air inlet portion of a wall surface of an engine room and reduces engine noise. The first aspect is characterized by being placed opposite a plurality of air inlet portions formed in the wall surfaces at least at two different locations (i.e., directions) of the engine room. This aspect further includes a split-type noise absorbing device provided to oppose the air inlet portion at the wall surface in one direction, where such device has a portion with an air passage of a longer length, and a cell-type noise absorbing device provided to oppose the air inlet portion at the wall surface in the other direction, where such device has a portion with an air passage of a shorter length. 
     According to the above configuration, the split-type noise absorbing device has an air passage of a longer length; therefore, noise is sufficiently absorbed while passing therethrough, and air flow resistance is less. The cell-type noise absorbing device has an air passage of a shorter length, but it has larger noise absorbing blade surface area relative to the quantity of passing air flow; therefore, noise is sufficiently absorbed. Thus, the split-type noise absorbing device and the cell-type noise absorbing device have almost the same noise absorbing performance. Accordingly, sound deadening effect is achieved even when air is supplied from two different directions, and sufficient air flow is achieved while air flow resistance is smaller, whereby greater cooling is obtained. 
     The split-type noise absorbing device and the cell-type noise absorbing device may include noise absorbing blades integrally formed of a rigid noise absorbing material. According to the above configuration, the noise absorbing blade is integrally formed of rigid noise absorbing material (for example, rigid sponge or the like); therefore, excellent noise absorbing performance can be obtained. 
     Further, the split-type noise absorbing device and the cell-type noise absorbing device may include the noise absorbing blades which are formed by adhering the noise absorbing material on both surfaces of a core material having sound insulating properties or air permeability. According to the above configuration, bending strength is increased, and such noise absorbing blade is easily manufactured. 
     Furthermore, the split-type noise absorbing device and the cell-type noise absorbing device may include noise absorbing blades which are formed by covering the noise absorbing material with plate material having air permeability. According to this configuration, the noise absorbing material is covered with a plate material having air permeability; therefore, a selection range of the noise absorbing material is enlarged, and the strength of the noise absorbing blade is increased. 
     A second aspect of a noise absorbing device according to the present invention is a noise absorbing device which is placed at an air inlet portion provided at a wall surface of an engine room of a construction machine and reduces noise in an engine. The second aspect is characterized by being placed to oppose a plurality of the air inlet portions provided at the side surface and the top surface of the engine room. This aspect further includes a split-type noise absorbing device, provided at the lower portion side to oppose the side surface air inlet portion, having a plurality of vertically-oriented, parallel noise absorbing blades and a portion with an air passage of a longer length, and a cell-type noise absorbing device, provided at the upper portion side to oppose said top surface air inlet portion, having a plurality of noise absorbing blades placed in parallel and a portion with an air passage of a shorter length. In particular, a width of each noise absorbing blade of the cell-type noise absorbing device is less than a width of a noise absorbing blade of the split-type noise absorbing device. 
     The above configuration is appropriate where a counterweight is provided at an engine room (for example, as in an upper revolving superstructure of a hydraulic shovel) and sufficient inlet area cannot be achieved with a port in only one direction, and air may be supplied from two directions—from an upper surface and a side surface. In addition, the width of the noise absorbing blade of the cell-type noise absorbing device is smaller than the width of the noise absorbing blade of the split-type noise absorbing device but the device is a cell type; therefore, the surface area of the noise absorbing blade relative to the quantity of passing air flow of the cell-type noise absorbing device is increased so that greater sound deadening effect is obtained. Accordingly, excellent cooling performance and sound deadening performance can be obtained while necessary weight for the counterweight is secured. 
     Further, each of the widths of a plurality of noise absorbing blades of the split-type noise absorbing device is successively changed in accordance with a round shape of the external perimeter of the engine room with respect to a plan view. Moreover, each pitch between each pair of blades of the split-type noise absorbing device may be an irregular pitch, proportional to each of the changed widths. 
     According to the above configuration, the device is applicable to a vehicle body with an engine room in a round shape as in the upper revolving superstructure of a hydraulic shovel. By adopting irregular pitches, the pitches between the noise absorbing blades having a smaller width are made smaller; therefore, the surface area of the noise absorbing blade for these portions relative to the quantity of passing air flow is increased. As a result, the noise absorbing effect at the portions having a smaller width is increased, and the noise absorbing performance can be almost the same as the other portions; therefore, the sound deadening effect as a whole is increased. 
     Each of the aforesaid irregular pitches and each pitch of a vertical grid of an exterior grille of the engine room may be conformed to each other. According to this configuration, air flows smoothly, and air resistance is reduced to increase cooling efficiency. 
     Each width of a plurality of noise absorbing blades of the split-type noise absorbing device is successively changed in accordance with a round shape of the external perimeter of the engine room, whereby each pitch between a plurality of the noise absorbing blades of the split-type noise absorbing device is a constant pitch, and portions with smaller widths out of said changed widths may have an irregular cell configuration having cells the number of which increases in reverse proportion to each width. 
     According to the above configuration, the number of cells is increased in reverse proportion to the width of the noise absorbing blade of the split-type noise absorbing device; therefore, the surface area of the noise absorbing blades with a smaller width is increased relative to the quantity of passing air flow. Thereby, the sound deadening effect for the portions with a smaller width is enhanced, and such portions exhibit almost the same noise absorbing performance of the other portions. 
     A first aspect of a device for taking air into an engine room of a construction machine according to the present invention includes a fan placed in an engine room, at least two air intake ports provided at the engine room or in the vicinity of said engine room and intersecting at a right angle, and a passage, which is provided in front of a radiator, and through which air attracted by the fan from the air intake ports flows toward the radiator. The passage is provided with an air flow stopping plate. The air flow stopping plate divides the passage into a passage through which air attracted from one of the air intake ports flows and a passage through which air attracted from the other of the air intake ports flows. The air flow stopping plate further prevents a collision between the air flowing from the two air intake ports. 
     According to the above configuration, the air flow stopping plate is provided in the passage and divides the passage into two passages, thereby air respectively supplied from the two air intake ports intersect at a right angle; however, the air flows do not interfere with each other. Consequently, the quantity of air supplied from the two air intake ports respectively increases, and the interior of the engine room is better cooled by a larger quantity of air and is cooled more efficiently. Accordingly, the quantity of air can be increased; therefore, despite an engine room of a construction machine being smaller, overheating can be effectively avoided, whether in regard to an engine, hydraulic devices, or the like which are provided within the engine room. In addition, for such a simple configuration, the engine room can be made smaller at a lower cost. 
     A second aspect of a device for taking air into an engine room of a construction machine includes a fan placed in an engine room, two opposing air intake ports provided at the engine room or in the vicinity of the engine room, and a passage, which is provided in front of a radiator, and through which air attracted by the fan from the air intake ports flows toward the radiator. The passage is provided with a air flow stopping plate. Similar to the first aspect, the air flow stopping plate divides the passage into a passage through which air attracted from one of the air intake ports flows and a passage through which air attracted from the other of the air intake ports flows, where the air flow stopping plate prevents a collision between the air flows originating from the opposing air intake ports. 
     According to the above configuration, the air flow stopping plate is provided in the passage and divides the passage into two passages, thereby each respective air flow supplied from the two opposing air intake ports flow to the radiator from the separate passages without interference, and the same effects as earlier explained for the first configuration are obtained. 
     Furthermore, the air flow stopping plate may be a current plate for rectifying air attracted from two air intake ports. According to the above configuration, the quantity of air supplied from the two air intake ports is further increased, and the interior of the engine room can be cooled with a larger quantity of air; therefore, engine room cooling can be performed efficiently. Accordingly, the quantity of air can be increased; therefore, despite an engine room of a construction machine being smaller, overheating can be effective avoided, whether in regard to an engine, hydraulic devices, or the like which are provided within the engine room. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a conventional cell-type noise absorbing device; 
     FIG. 2 is a perspective view of a conventional split-type noise absorbing device; 
     FIG. 3 is a sectional side elevation view of an engine room according to a first embodiment of the present invention; 
     FIG. 4 is a perspective view of the noise absorbing device of FIG. 3; 
     FIG. 5 is a perspective view of a second example of a noise absorbing blade of the first embodiment; 
     FIG. 6 is a perspective view of a third example of a noise absorbing blade of the first embodiment; 
     FIG. 7 is a perspective view of a fourth example of a noise absorbing blade of the first embodiment; 
     FIG. 8 is a perspective view of a noise absorbing device according to a second embodiment of the present invention; 
     FIG. 9 is a sectional side elevation view of an engine room of a construction machine according to a third embodiment of the present invention; 
     FIG. 10 is a sectional plan view of the engine room of FIG. 9; 
     FIG. 11 is a perspective view of a split-type noise absorbing device of according to a third embodiment of the present invention; 
     FIG. 12 is a front view of the split-type noise absorbing device of the third embodiment; 
     FIG. 13 is a front view of the engine room of FIG. 9; 
     FIG. 14 is a detailed explanatory view of the noise absorbing blade of FIG. 10; 
     FIG. 15 is an explanatory view of attaching the noise absorbing blade of FIG. 9; 
     FIG. 16 is an explanatory view of the way to replace the noise absorbing blade of FIG. 9; 
     FIG. 17 is a perspective view of another example of the split-type noise absorbing device of the third embodiment; 
     FIG. 18 is a front view of the split-type noise absorbing device of FIG. 17; 
     FIG. 19 is a sectional side elevation view of a device for taking air into an engine room according to a fourth embodiment of the present invention and is a sectional view taken along the  19 — 19  line in FIG. 20; 
     FIG. 20 is a plan view of the device for taking air into an engine room of the fourth embodiment; 
     FIG. 21 is a front view of the device for taking air into an engine room of the fourth embodiment; 
     FIG. 22 is a graph explaining the relationship between the opening areas of inlet ports and the quantity of air in the fourth embodiment; 
     FIG. 23 illustrates a current plate which is another example of a air flow stopping plate according to the fourth embodiment; 
     FIG. 24 is an explanatory view of another example of the placement of the inlet ports according to the fourth embodiment; 
     FIG. 25 is a plan view of a conventional, ultra-small, revolving-type hydraulic shovel; and 
     FIG. 26 is a side elevation view of the hydraulic shovel of FIG.  25 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiments of the present invention will now be described in detail below with reference to the drawings. 
     Generally, there are two kinds of configurations of a noise absorbing device, that is, a cell-type noise absorbing device  11  in which noise absorbing plates  14  are combined to be a box shape (see FIG. 1) and a split-type noise absorbing device  12  in which noise absorbing blades  13  are placed in parallel (see FIG.  2 ). The cell-type noise absorbing device  11  has a ridge line of a longer length relative to an air passage area. Accordingly, even if a length L of the cell-type noise absorbing device  11  is shorter, the surface area of the noise absorbing plate  14  is greater relative to the quantity of air passing therethrough; therefore, the cell-type noise absorbing device  11  has excellent noise absorbing performance. The split-type noise absorbing device  12  has less air passage resistance due to fewer obstacles. In order to improve noise absorbing performance, a width W of the noise absorbing blade  13  is increased, or the surface area of the noise absorbing blade  13  is increased by reducing a pitch P relative to the quantity of air flow. 
     FIG. 3 is a sectional side elevation view of an engine room  1  according to a first embodiment of the present invention. In the engine room  1 , a multi-way noise absorbing device  10 , a radiator  2 , and an engine  3  are placed in this order from the front. A side air inlet portion  4  and a top air inlet portion  5  are provided at the front surface and the forward portion of the top surface of the engine room  1 , respectively. An air passage length L adjacent to the top air inlet portion  5  is shorter than an air passage length (i.e., the width of the noise absorbing blade  13 ) W of the side air intake portion  4 . 
     As shown in FIG. 4, for the noise absorbing device  10 , a plurality of noise absorbing blades  13  are vertically oriented and disposed in parallel. In the noise absorbing device  10 , the split-type noise absorbing device  12  is formed at the lower portion thereof, and the cell-type noise absorbing device  11  is formed by respectively placing a front noise absorbing blade  14   a  and a rear noise absorbing plate  14   b  at the forward and the rearward portions of the upper portion thereof. In such a configuration, the air passage length L of the cell-type noise absorbing device  11  portion is shorter than the width W of the noise absorbing blade  13 . The noise absorbing blade  13  is integrally formed of a rigid noise absorbing material  20  (for example, rigid sponge or the like). 
     The other examples of the noise absorbing blade  13  will be explained. A noise absorbing blade  13   a  shown in the second example in FIG. 5 is formed by adhering, the noise absorbing material  20  on both sides of a core material  21  having sound insulating properties or air permeability. Accordingly, this second example has greater bending strength and is easy to manufacture. A third example for a noise absorbing blade  13   b,  shown in FIG. 6, is made by covering the noise absorbing material  20  with an air permeable plate material  22  (for example, a metal plate having a number of perforations). Consequently, the blade  13   b  has greater strength, thereby a wide selection range of noise absorbing material  20  may be provided. A fourth embodiment of a noise absorbing blade  13   c  is illustrated in FIG.  7 . The blade  13   c  is made by adhering noise absorbing material  20  on both sides of a core piece material  23  having air permeability (for example, a metal plate having a number of perforations, a wire netting with a number of punched holes being formed therein, or the like) to exhibit excellent noise absorbing qualities. These noise absorbing blades  13 ,  13   a,    13   b,  and  13   c  are also applicable to the front noise absorbing plate  14   a  and the rear noise absorbing plate  14   b.    
     The operation of the first embodiment will be explained with reference to FIG.  3 . The side air inlet portion  4  and the top air inlet portion  5  are provided in the engine room  1 ; therefore, sufficient fresh air is readily available. Due to the width W of the noise absorbing blade  13  being relatively long, noise passing through the side air inlet portion  4  to the outside is sufficiently reduced. In addition, this portion is the split-type noise absorbing device  12 ; therefore, the air passage resistance is less and the cooling performance is greater. As for the noise going outside from the top air inlet portion  5 , the air passage length L is shorter, but the cell-type noise absorbing device  11  is formed, and the noise absorbing performance is improved. Thus, it is possible to provide almost equal noise absorbing performance with the cell-type noise absorbing device  11  portion and the split-type noise absorbing device  12  portion of the absorbing device  10 ; therefore, higher noise absorbing performance can be obtained. 
     FIG. 8 is a perspective view of a noise absorbing device  10   a  of a second embodiment. The air passage length L associated with the top air inlet portion  5  is longer than the air passage length W associated with the side air absorbing portion  4 . In the noise absorbing device  10   a,  the upper portion forms the split-type noise absorbing device  12 , and the lower portion forms the cell-type noise absorbing device  11 . The operation and the effects are the same as in the first embodiment, and the air flow from the upper portion (the downward arrow in FIG. 8) is prevented from interfering with the air flow from the lower portion (the horizontal arrow in FIG. 8) by a lateral plate  11   a  composing the lower part of the cell-type noise absorbing device  11 ; therefore, air flow is obtained with higher efficiency. 
     FIGS. 9 and 10 relate to a third embodiment of the present invention and show the engine room  1  of a construction machine, for example, a hydraulic shovel. In the engine room  1 , a multi-way noise absorbing device  10   b,  a radiator  2 , and an engine  3  are provided in this order from the side surface. In the case of a hydraulic shovel, the engine room  1  is generally placed at the rear portion of an upper revolving superstructure, and at the same time, a counterweight  6  is also placed at the rear portion. For this reason, it is difficult to form the side air inlet portion  4  to be large; therefore, utilization of the top air inlet portion  5  is commonly necessary. The air passage length L associated with the top air inlet portion  5  is shorter than the air passage length W associated with the side air absorbing portion  4  for purposes of air flow with respect to the radiator  2 . From the point of the external shape of the construction machine, the air inlet width B at the upper portion of the noise absorbing device  10   b  is shorter than the width W at the lower portion. The noise absorbing device  10   b  has a plurality of noise absorbing blades  13  vertically-oriented and placed in parallel. In the noise absorbing device  10   b,  the split-type noise absorbing device  12  is formed at the lower portion, while the cell-type noise absorbing device  11  is formed by respectively placing the front noise absorbing plate  14   a  and the rear noise absorbing plate  14   a  at the forward and rearward portions of the upper portion thereof. 
     The external perimeter of the engine room  1  has a rounded portion, as shown in FIG. 10, in accordance with the round shape of the rear portion of the upper revolving superstructure of the hydraulic shovel. Consequently, the width W of the noise absorbing blade  13  of the split-type noise absorbing device  12  is gradually changed from a width WA to a width WX in accordance with the round shape. The numeral  7  is an exterior grille which is freely opened and closed. 
     FIGS. 11 and 12 show the split-type noise absorbing device  12  at the lower portion of the noise absorbing device  10   b.  As described above, the width W of the noise absorbing blade  13  is successively changed from WA to WX, and WA&gt;WX. Accordingly, the noise absorbing performance is reduced towards the width WX side. Therefore, the pitch P between the noise absorbing blades  13  may be changed in proportion to the width W of an adjacent noise absorbing blade  13 . Specifically, in reference to FIG. 12, the respective pitches P are orderly changed from a pitch PA to a pitch PX, and PA&gt;PX. In other words, the width of the air passage is successively changed. Thereby the surface area of the noise absorbing blade  13 , relative to the quantity of air flow, is almost equal; therefore, the noise absorbing performance of the noise absorbing blade  13  for each portion is almost the same so that the noise absorbing performance of the entire split-type noise absorbing device  12  is improved. It should be noted that the split-type noise absorbing device  12  is applicable to the inlet side as well as to the outlet side as shown by the arrows in FIG.  11 . As further shown in FIG. 13, the pitches PA to PX of the noise absorbing blade  13  may conform to the pitch CA to CX of a vertical grid  8  of the exterior grille  7 . 
     In FIG. 14, the noise absorbing blade  13  has a thickness T 1  at a front end portion thereof, which is thinner than thickness T at a rear portion thereof, and a tapering portion  24  formed therebetween and at a forward portion of the noise absorbing blade  13 . The thickness T 1  is almost the same as the width D of the vertical grid  8 , and as described above, the pitches PA to PX of the noise absorbing blade  13  and the pitches CA to CX of the vertical grid  8  conform; therefore, air smoothly flows (as shown by the arrows), and air passage resistance is reduced. 
     In FIGS. 15 and 16, the noise absorbing blade  13  is supported in such a way as the lower end portion thereof is inserted into a lower holder  31  provided on a floor surface of the engine room  1  and the upper portion thereof at the rear edge is inserted into an upper holder  32  attached on the front surface of the radiator  2 . As a result, after the exterior grille  7  (see FIG. 10) is opened, the noise absorbing blade  13  can be inserted from the side air inlet portion  4 , as shown in FIG. 16, and turned around to be attached at the position shown by the alternate long and two short dashes line. Accordingly, a replacement operation of the noise absorbing blade  13  is extremely easy. 
     FIGS. 17 and 18 show other examples of the split-type noise absorbing device  12  according to a third embodiment. The width W of the noise absorbing blade  13  is successively changed from WA to WX (WA&gt;WX), but the pitch P is not changed. Rather, lateral noise absorbing plates  16  span between selected noise absorbing blades  13  having portions of a smaller width W to form a cell-type noise absorbing device  11 . Pitches Q of the lateral noise absorbing plate  16  are successively changed from QA to QX (QA&gt;QX) in proportion to the widths W of the noise absorbing blades  13 . Specifically, the number of cells  11   b  increases in reverse proportion to the widths W of the noise absorbing blades  13 . The operational effects are the same as the noise absorbing device  12  of FIGS. 11 and 12. 
     Next, a device for taking air into an engine room of a construction machine according to a fourth embodiment of the present invention will be described in detail. 
     In FIG. 19 to FIG. 21, an engine  113  in an engine room  111  is attached to an upper revolving superstructure frame  112 . A fan  114  which attracts air by being rotationally driven by the engine  113 , is placed in front of the engine  113  (in a left direction of FIG.  19 ). A radiator  115  is placed in front of the fan  114 , and water for cooling the engine  113  is cooled with the air attracted by the fan  114 . A shroud  116  is placed at the rear portion of the radiator  115 . A cooler for air conditioning (not illustrated) is additionally provided at the front of the radiator  115 . A counterweight  121  is provided at the front side of the radiator  115 , separated from the radiator  115  by a predetermined space, and a counterweight inlet port  122 , from which air attracted by the fan  114  flows, extends through the counterweight  121 . A counterweight passage  123  is provided at a portion from the counterweight inlet port  122  to the radiator  115 . 
     An engine hood  126  is provided above the radiator  115 , separated by a predetermined space, and a hood inlet port  127  extends through the engine hood  126 . A hood passage  128  is provided at a portion from the hood inlet port  127  to the radiator  115 . 
     The counterweight passage  123  and the hood passage  128  intersect at a right angle. An air flow stopping plate  130  is provided at a position MA where both the passages intersect. The counterweight passage  123  and the hood passage  128  are separated by the air flow stopping plate  130 . The counterweight passage  123  and the hood passage  128  form the respective passages at the front of the radiator  115 . 
     FIG. 19 shows the situation in which the counterweight inlet port  122  and the hood inlet port  127  respectively have openings at one position, but if necessary in order to make excellent external appearance or the like, it may be suitable to provide a plurality of parallel openings, for example, in a slit form, as shown by the numerals  127   a,    127   b,  etc. in FIG.  20 . In this case, if a plurality of inlet ports  127   a,    127   b,  etc. are composed of a noise absorber, the noise from the inlet ports  127   a,    127   b,  etc. can be prevented. 
     The operation of the aforesaid configuration will be explained hereafter. 
     Returning to FIG. 19, when the engine  113  is operated and the fan  114  is rotationally driven, the fan  114  attracts air from the outside of the engine room  111  and passes the air toward the engine  113  side of the engine room  111 . At this time, air Aic from the counterweight inlet port  122  and air Aif from the hood inlet port  127 , as attracted by the fan  114 , flow in the engine room  111  toward the radiator  115 . The air Aic from the counterweight inlet port  122 , which passes through the counterweight passage  123 , is attracted by the fan  114  by way of the lower side surface of the radiator  115  and flows toward the engine  113 , while the air Aif from the hood inlet port  127 , which passes through the hood passage  128 , is attracted by the fan  114  by way of the upper side surface of the radiator  115  and also flows toward the engine  113 . As described above, the counterweight passage  123  and the hood passage  128  are separated by the air flow stopping plate  130 ; therefore, the air Aic from the counterweight inlet port  122  and the air Aif from the hood inlet port  127  separately pass through the radiator  115  without interfering with the other. 
     In the above configuration, as described above, changes in the quantity of inlet air is performed by changing an opening area of the auxiliary hood inlet port  127 , which supplies a shortage air amount, while an opening area Ac of the main counterweight inlet port  122  is fixed. As a result, as shown in FIG. 22, as the opening, area An increases, a quantity of auxiliary air Via from the auxiliary hood inlet port  127  increases. At this time, the quantity of main air Vim from the counterweight inlet port  122  is substantially fixed, i.e., is provided largely without change. Accordingly, as for the total quantity of air Vic, the quantity of air, which is a result of adding up both of the quantity of air Vim and Via, is obtained. 
     Next, as shown in FIG. 23, the air flow stopping plate  130  is formed to be a current plate  130   a  by providing a curved surface Qa on the hood passage  128  side. As a result, as shown in FIG. 22, the total quantity of air using the current plate Vid increases more than the total quantity of air Vic. This is because the quantity of auxiliary air Via flowing through the hood passage  128  from the hood inlet port  127  increases. In this way, by eliminating stagnation and disturbance of the quantity of auxiliary air Via, the total quantity of air can be increased. 
     The aforesaid fourth embodiment shows an example of the placement in which the counterweight passage  123  is orthogonal to the hood passage  128  by providing the face of the counterweight inlet port  122  in parallel with the face of the radiator  115  and providing the face of the hood inlet port  125  perpendicular to the face of the counterweight inlet port  122 . However, the vertical placement is not limited to the example shown in FIG.  19 . 
     For example, as shown in FIG. 24, the same effects can be obtained even when the face of a first counterweight inlet port  122 A and the face of a second counterweight inlet port  122 B are provided in a direction perpendicular to the face of the radiator  115 , where a first counterweight passage  123 A and a second counterweight passage  123 B are placed to face each other. Explaining with reference to FIG. 19, when inlet ports are provided at the engine hood  126  and the revolving superstructure frame  112 , and the inlets ports are placed to face each other, the same effects are also obtained. 
     It should be further noted that regarding the orthogonal placement or the placement in a perpendicular direction, such angle is not limited to 90 degrees, and the same effects are also obtained if the angle is not less than 60 degrees. The placement facing to each other is not limited to the situation in which the faces of two inlet ports are parallel to each other, but the angle may be adjusted as necessary.