Construction Machine

Abstract

In a NOx selective catalytic reduction device that purifies NOx in exhaust gas exhausted from an engine, a urea water supply system is constructed of a urea water injection valve, a urea water tank, urea water supply piping and a urea water supply device, a connection frame member is provided on a revolving superstructure to extend in a longitudinal direction in a center in a width direction to reinforce the revolving superstructure and to be located between a pair of main frame members that connects a working device so that a rear side faces the engine, the urea water tank is placed on the revolving superstructure on a front side from a center of revolution of the revolving superstructure, the engine is placed on the revolving superstructure on a rear side from the center of revolution of the revolving superstructure, and the urea water supply device is installed on the connection frame member to face the engine.

What is claimed is: 
     
         1 . A construction machine, comprising:
 a revolving superstructure;   an operator's cab provided at a front part on the revolving superstructure;   a working device mounting section provided at the front part on the revolving superstructure in a side part of the operator's cab;   a counterweight provided at a rear part of the revolving superstructure;   an engine as a drive source placed on the revolving superstructure between the counterweight and the operator's cab;   a NOx selective catalytic reduction device installed on a side of the engine and interposed in an exhaust passage of the engine;   a urea water injection valve that injects urea water to exhaust upstream of the NOx selective catalytic reduction device;   a urea water tank that stores the urea water;   urea water supply piping with one end connected to the urea water injection valve, and the other end connected to the urea water tank; and   a urea water supply device that is interposed in the urea water supply piping, and feeds the urea water under pressure to the urea water injection valve,   wherein the urea water tank is placed on the revolving superstructure on a front side from a center of revolution of the revolving superstructure,   the engine is placed on the revolving superstructure on a rear side from the center of revolution of the revolving superstructure,   the revolving superstructure has a pair of main frame members that extend in a longitudinal direction near a center in a width direction to reinforce the revolving superstructure and construct the working device mounting section, and a connection frame member that connects the pair of main frame members between the center of revolution of the revolving superstructure and the engine, and   the urea water supply device is installed on the connection frame member to face the engine.   
     
     
         2 . The construction machine according to  claim 1 ,
 wherein an opening portion is provided at a portion of the revolving superstructure under the engine to enable maintenance of at least the engine.   
     
     
         3 . The construction machine according to  claim 1 ,
 wherein the connection frame member is a plate member that is laid between the pair of main frame members to be perpendicular to the revolving superstructure, and   the urea water supply device is mounted on a surface of the plate member, which faces the engine.   
     
     
         4 . The construction machine according to  claim 2 ,
 wherein the connection frame member is a plate member that is laid between the pair of main frame members to be perpendicular to the revolving superstructure, and   the urea water supply device is mounted on a surface of the plate member, which faces the engine.   
     
     
         5 . The construction machine according to  claim 3 ,
 wherein at the urea water supply piping, cooling water piping which allows cooling water for the engine to flow through extends along the urea water supply piping,   the urea water supply piping and the cooling water piping are respectively connected to an outer surface of the urea water supply device that is perpendicular to the surface of the plate member, so that urea water and the cooling water flow in the urea water supply device, and   the construction machine further comprising a thermal insulating cover that covers the outer surface of the urea water supply device including connection portions of the urea water supply piping and the cooling water piping and a part of the surface of the plate member, and keeps the connection portions warm.   
     
     
         6 . The construction machine according to  claim 4 ,
 wherein at the urea water supply piping, cooling water piping which allows cooling water for the engine to flow through extends along the urea water supply piping,   the urea water supply piping and the cooling water piping are respectively connected to an outer surface of the urea water supply device that is perpendicular to the surface of the plate member, so that urea water and the cooling water flow in the urea water supply device, and   the construction machine further comprising a thermal insulating cover that covers the outer surface of the urea water supply device including connection portions of the urea water supply piping and the cooling water piping and a part of the surface of the plate member, and keeps the connection portions warm.   
     
     
         7 . The construction machine according to  claim 5 ,
 wherein a thermal insulating member is provided on a part of the surface of the plate member and a surface of the thermal insulating cover on the urea water supply device side.   
     
     
         8 . The construction machine according to  claim 6 ,
 wherein a thermal insulating member is provided on a part of the surface of the plate member and a surface of the thermal insulating cover on the urea water supply device side.