Abstract:
A hybrid construction machine includes an engine, a generator motor, and a hydraulic pump. They constitute a power unit, and are connected in series, with the generator motor being disposed between the engine and the hydraulic pump and with a center of gravity of the entire power unit being positioned closer to the generator motor than the center of gravity of the engine. A mount installation bracket is mounted at a side of each flange disposed at a corresponding side of the generator motor. A generator-motor-side mount device is mounted to the bracket.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a hybrid construction machine in which a power unit is formed by connecting three devices, that is, an engine, a generator motor, and a hydraulic pump in series with each other. 
     2. Description of the Related Art 
     As shown in  FIG. 5 , in an excavator, an upper rotating structure  2 , disposed on a crawler-type lower traveling structure  1 , is mounted so as to be rotatable around a vertical axis that is perpendicular to the ground, and a working attachment  3  is mounted to a front portion of the upper rotating structure  2 . 
     A cabin  5 , a counterweight  6 , and an engine room  7  are provided at the upper rotating structure  2 . The cabin  5  is provided at the left side of a front portion of an upper frame  4  serving as a base. The counterweight  6  is provided at a back end portion of the upper frame  4 . The engine room  7  is provided at a back portion (forwardly of the counterweight  6 ) of the upper rotating structure  2 . An engine  8  is set as a power source in a left-right direction in the engine room  7 . 
     In the specification, “front/back” and “left/right” are defined as viewed from an operator sitting in the cabin  5 . 
       FIG. 6  shows an arrangement of devices in an engine room  7  of a hydraulic excavator having only an engine  8  as a power source, as viewed from a back side of a machine. 
     In the hydraulic excavator, as in the illustration, a power unit U 1  is formed by connecting a hydraulic pump  9  in series with the engine  8 . Reference numeral  10  denotes a cooling fan directly connected to the engine  8 . 
     In the power unit U 1  of the hydraulic excavator, a center of gravity X 1  of the entire unit when viewed from the back side (or a front side) is slightly displaced towards the pump from an engine center of gravity X 2 . 
     As a mounting structure that supports the power unit U 1  on a body frame (upper frame  4 ) of the machine, mount devices  11  and  12  are provided on respective sides of the center of gravity X 1  of the power unit in an axial direction. 
     More specifically, the mount device at one side (hereunder referred to as the “left mount device” in accordance with directions defined in  FIG. 6 )  11  is provided at the engine  8 . The mount device at the other side (hereunder referred to as the “right mount device” in accordance with directions defined in  FIG. 6 )  12  is provided at a fly wheel housing  13  accommodating a fly wheel. 
     The mount devices  11  and  12  each include a vibration absorbing mechanism that attenuates vibration by a resilient member such as rubber or a spring. 
     In this mounting structure, the distance between the center of gravity X 1  of the power unit and one of supporting points and the distance between the center of gravity X 1  of the power unit and the other of the supporting points are substantially equal to each other. Accordingly, the overall weight of the power unit U 1  is substantially equally shared by the mount devices  11  and  12  at both sides. 
     The power unit mounting structure in the hydraulic excavator is discussed in Japanese Unexamined Patent Application Publication No. 2003-90387 (Patent Document 1). 
     In a hybrid excavator using both motive power and electric power, as shown in  FIG. 7 , a power unit U 2  is formed by providing a generator motor  14  between an engine  8  and a hydraulic pump  9 . The generator motor  14  operates as an electric generator and an electric motor. 
     An engine-side flange  15  and a pump-side flange  16  are provided on the left and right of the generator motor  14 , respectively, so as to project towards the outer periphery while they act as end covers. 
     The flanges  15  and  16  are formed of thick plates, respectively. The engine-side flange  15  is connected to a fly wheel housing  13  at the engine  8 , and the pump-side flange  16  is connected to the hydraulic pump  9 . 
     The entire structure of the hybrid excavator is discussed in Japanese Unexamined Patent Application Publication No. 2002-227241 (Patent Document 2). 
     In the power unit U 2  of the hybrid excavator, as in the illustration, a center of gravity X 3  of the power unit is shifted considerably towards the hydraulic pump  9  from the center of gravity X 1  of the power unit U 1  for the hydraulic excavator in accordance with the addition of the generator motor  14 . 
     Therefore, if the mounting structure provided on the basis of the specification of the hydraulic excavator shown in  FIG. 6  is used as it is in the hybrid excavator, the distance between the center of gravity X 3  of the power unit and one of supporting points and the distance between the center of gravity X 3  of the power unit and the other of the supporting points differ greatly. Therefore, the stability of a supporting state becomes extremely poor. 
     More specifically, since an unbalanced load acts, for example, the left mount device may have insufficient strength due to an increase in load on the left mount device  11 , or vibration may tend to occur. 
     The generator motor  14  is not directly supported. Therefore, its own weight and the weight of the hydraulic pump act upon the generator motor  14 . Consequently, a force is forcefully generated at an internal structure through a rotary shaft, thereby adversely affecting the durability and performance of the generator motor  14 . 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a hybrid construction machine that can stably support a power unit at both sides thereof that are at substantially equal distances from the center of gravity of the power unit, and that can reduce a load exerted upon a generator motor. 
     According to an aspect of the present invention, there is provided a hybrid construction machine comprising an engine, a generator motor, a hydraulic pump, all of which constitute a power unit, and are connected in series, with the generator motor being disposed between the engine and the hydraulic pump and with a center of gravity of the entire power unit being positioned closer to the generator motor than a center of gravity of the engine. On this presupposition, mount devices are disposed at the engine and the generator motor, respectively, with the center of gravity of the entire power unit being disposed therebetween. In addition, the power unit is supported on a body frame of the machine by the mount devices. Therefore, it is possible to stably support the power unit with the distance between the center of gravity of the power unit and the mount device at one side and the distance between the center of gravity of the power unit and the mount device at the other side being substantially equal to each other. 
     This makes it possible to substantially equalize a load on the mount devices at both sides to overcome the possibility of insufficient strengths of the mount devices, and to reduce vibration. 
     Since the generator motor is directly supported by the mount device, it is possible to reduce a load applied to the generator motor, and to protect an internal structure, so that actual performance and durability can be ensured. 
     According to the present invention, in the above-described structure, it is desirable that an engine-side flange connected to the engine be provided at one side of the generator motor in an axial direction thereof, a pump-side flange connected to the hydraulic pump be provided at the opposite side, a mount installation bracket be provided at a side of each of the flanges, and the generator-motor-side mount device be mounted to the mount installation bracket. 
     According to the present invention, in the above-described structure, it is desirable that a plurality of the mount installation brackets and a plurality of the generator-motor-side mount devices be provided at respective sides of the power unit in a direction perpendicular to an axial direction of the power unit. 
     In this case, since the mount devices at the generator motor are provided at respective sides of the power unit in a direction perpendicular to the axial direction of the power unit (front-back direction in the excavator shown in  FIG. 5 ), it is possible to further stabilize a supporting state of the entire power unit and the generator motor. 
     According to the present invention, in the above-described structure, it is desirable that the hybrid construction machine further comprise an engine-side suspension part and a generator-motor-side suspension part for suspending the entire power unit, that the generator-motor-side suspension part be provided at the mount installation bracket. 
     In this case, since the entire power unit can be suspended with the suspension parts at the engine and the generator motor, it is possible to transport the power unit as one assembly and install it on a machine. Therefore, it is possible to enhance transportability and increase assembly work efficiency. 
     Further, in this case, since the suspension part at the generator motor is provided at a mount installation bracket, that is, since a suspension point at one side of the power unit in the axial direction is set at the generator motor, the power unit can be suspended in a well-balanced state at both sides thereof that are at substantially equal distances from the center of gravity of the power unit. 
     Still further, since the suspension parts are formed as parts of the mount installation brackets, costs are reduced and assembly is facilitated. 
     In the above-described desirable cases, the mount installation brackets are installed on both the engine-side flange and the pump-side flange originally provided at the generator motor, and the mount device at the generator motor side is provided at the bracket, it is possible to increase the strength of the mount devices themselves for stabilizing a supporting state of the power unit, and to use the flanges at both sides as mount device installation members to reduce costs, facilitate assembly, and increase space efficiency. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a supporting state of a power unit according to an embodiment of the present invention, as viewed from a back side of a machine; 
         FIG. 2  is an enlarged view of a portion of  FIG. 1 ; 
         FIG. 3  is a side view of  FIG. 2  as viewed from a pump; 
         FIG. 4  is a perspective view of a portion of the power unit and a portion of a mounting structure; 
         FIG. 5  is a schematic side view of an excavator serving as an example to which the present invention is applied; 
         FIG. 6  corresponds to  FIG. 1  and shows a supporting state of a power unit for a hydraulic excavator; and 
         FIG. 7  corresponds to  FIG. 6  and shows a case in which a supporting structure of the power unit for the hydraulic excavator is applied to a hybrid excavator. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An embodiment of the present invention will be described with reference to  FIGS. 1 to 4 . 
     In the embodiment, the present invention is applied to a hybrid excavator. 
     Similarly to  FIG. 7 ,  FIG. 1  shows a power unit in an engine room and a supporting structure thereof, as viewed from a back side of a machine. 
       FIG. 1  shows that (I) a power unit U 2  is formed by providing a generator motor  14  between an engine  8  and a hydraulic pump  9 , (II) an engine-side flange  15  and a pump-side flange  16 , which have the form of thick plates, are provided on the left and right of the generator motor  14 , respectively, so as to project towards the outer periphery while they act as end covers; and the engine-side flange  15  is connected to a fly wheel housing  13  at the engine  8 , and the pump-side flange  16  is connected to the hydraulic pump  9 , and (III) a center of gravity X 3  of the power unit is shifted considerably towards the hydraulic pump from the center of gravity X 1  of the hydraulic excavator power unit U 1  (shown in  FIG. 6 ). The features of (I) to (III) are the same as those of the related art shown in  FIG. 7  (when a supporting structure of the hydraulic shovel power unit U 1  shown in  FIG. 6  is applied to the hybrid excavator power unit U 2 ). 
     As a mounting structure of the power unit U 2 , mount devices  17  and  18 , each including a vibrating absorbing structure, are provided on respective sides of the center of gravity X 3  of the power unit in an axial direction. Hereunder, the mount devices  17  and  18  will be referred to as the “left mount devices  17 ” and the “right mount devices  18  as viewed from the back side of the machine. By the mount devices  17  and  18 , the entire power unit  2  is supported on an upper frame  4 . 
     As with the left mount device  11  in the related art shown in  FIG. 7 , of the mount devices  17  and  18 , the left mount devices  17  are provided at an end portion of the engine  8  opposite to the pump (that is, on the left of a center of gravity X 2  of the engine). 
     The right mount devices  18  are mounted to a generator motor  14  through mount installation brackets  19 . 
     In detail, as shown in  FIGS. 2 to 4 , the mount installation brackets  19  each include a vertical plate portion  19   a  and a horizontal plate portion  19   b . The vertical plate portions  19   a  are mounted on respective sides of each of the flanges  15  and  16  at both sides of the generator motor  14 . The right mount devices  18  are mounted to substantially the center of the horizontal plate portions  19   b  (that is, at substantially the center in an axial direction of the generator motor  14 ). 
     It is desirable that the positions where the right mount devices are mounted substantially match the center of gravity of the generator motor  14 . 
     As shown in  FIGS. 3 and 4 , the mount installation brackets  19  are mounted to front and back side surfaces of each of the flanges  15  and  16 . The right mount devices  18  are mounted to the brackets  19 . 
     That is, the right mount devices  18  are provided at respective sides of the power unit U 2  in a direction perpendicular to an axial direction thereof (that is, in a front-back direction) so as to be symmetrical or substantially symmetrical with respect to the center of the generator motor. 
     According to the power unit supporting structure, it is possible to stably support the power unit U 2  by setting a distance L 1  between the power-unit center of gravity X 3  and the mount devices  17  and a distance L 2  between the power-unit center of gravity X 3  and the mount devices  18  substantially equal to each other. 
     This makes it possible to substantially equalize a load on the mount devices  17  and  18  at both sides. For this reason, it is possible to eliminate an unbalanced load to overcome the possibility of insufficient strengths of the mount devices  17  and  18 , and to reduce vibration. 
     Since the generator motor  14  is directly supported by the mount devices  18 , it is possible to reduce a load applied to the generator motor  14 , and to protect an internal structure, so that actual performance and durability can be ensured. 
     In this case, since the mount installation brackets  19  are mounted to each of the engine-side flange  15  and the pump-side flange  16  originally provided at the generator motor  14 , and the mount devices  18  at the generator motor are provided at the respective brackets  19 , it is possible to increase the strengths of the mount devices  18  themselves to further stabilize a supporting state of the entire power unit. 
     More specifically, it is possible to increase the strengths of the mount devices  18  by (a) firmly mounting the brackets  19  to the generator motor  14  in a doubly supported state, (b) using the flanges  15  and  16  as strength members constituting parts of the mount devices  18 , and (c) forming the flanges  15  and  16  in the form of thick plates originally having sufficient strength so that the flanges  15  and  16  can be firmly connected to the engine  8  and the hydraulic pump  9 . This makes it possible to stabilize a supporting state of the power unit U 2 . 
     Moreover, since the already existing flanges  15  and  16  are used as mount installation members, costs are reduced, assembly is facilitated, and space efficiency is increased. 
     As suspension parts for suspending the power unit U 2 , an engine-side suspension part  20  is provided at an upper surface of an end portion opposite to the pump of the engine  8 , and generator-motor-side suspension parts  21  and  21  are provided at the horizontal plate portions  19   a  and  19   b  of the respective mount installation brackets  19  and  19 . 
     As shown in  FIG. 1 , the suspension parts  20 ,  21 , and  21  make it possible to suspend the entire power unit U 2  at three suspension points with, for example, a crane  22  (only its hook is shown). For this reason, it is possible to transport the power unit U 2  as one assembly and install it on a machine. Therefore, it is possible to enhance transportability and increase assembly work efficiency. 
     In this case, since the suspension parts  21  and  21  at the generator motor are provided at the mount installation brackets  19  and  19 , that is, since a suspension point at one side (right side) of the power unit U 2  in the axial direction is set at the generator motor  14 , the power unit U 2  can be suspended in a well-balanced state with the distance between the center of gravity X 3  and one side of the power unit U 2  and the distance between the center of gravity X 3  and the other side of the power unit U 2  being substantially the same. 
     Since the suspension parts  21  are formed as parts of the mount installation brackets  19 , costs are reduced and assembly is facilitated. 
     Other Embodiments 
     (1) Although, in the embodiment, the generator-motor-side mount devices  18  are provided at the front and back sides of the generator motor  14 , one mount device  18  may be provided at a lower surface of the generator motor  14 . 
     In this case, the mount installation brackets  19  are mounted to respective sides of a lower surface of each of the flanges  15  and  16 . 
     In addition, when the mount devices  18  (the mount installation brackets  19 ) are provided on the front and back sides, or when the mount device  18  is provided at only one location of the lower surface, the mount devices  18  or the mount device  18  may be mounted to a housing of the generator motor  14  instead of on both sides of each of the flanges  15  and  16 . 
     (2) The generator-motor-side suspension parts  21  may be provided at the housing of the generator motor  14  or at one of the flanges  15  and  16  (desirably, at the pump-side flange  15 ). 
     (3) The present invention is not limited in its application to a hybrid excavator. The present invention may be widely applied to hybrid construction machines such as crushing machines and separating machines that are formed by converting excavators. 
     Although the invention has been described with reference to the preferred embodiments in the attached figures, it is noted that equivalents may be employed and substitutions made herein without departing from the scope of the invention as recited in the claims.