Lift truck

Abstract

In a lift truck of a type that, using a brake controller 20, a traveling motor 3 can be braked by an electromagnetic brake 17, the brake controller 20, when it detects the brake operation of a brake operation device, not only actuates the electromagnetic brake 17 but also detects the truck body weight and traveling speed of the lift truck, thereby electrically braking the traveling motor 3 in such a manner that the electric brake force can be increased or decreased in correspondence to whether the thus-detected truck body weight is heavy or light as well as the electric brake force can be increased or decreased in correspondence to whether the thus-detected traveling speed is high or low.

What is claimed is:  
     
         1 . A lift truck comprising: 
 a truck body;    a traveling motor for traveling the truck body;    an electromagnetic brake for braking rotation of the traveling motor;    a brake operation device to be operated for actuation of the electromagnetic brake; and,    a brake controller for detecting the brake operation of the brake operation device to actuate the electromagnetic brake,    wherein the brake controller, when the brake controller detects the brake operation of the brake operation device, actuates the electromagnetic brake and detects the weight of the truck body; and    the brake controller electrically controls the traveling motor in such a manner that an electric brake force is increased or decreased in correspondence to the weight of the truck body.    
     
     
         2 . The lift truck as set forth in  claim 1 , wherein the brake controller comprises: 
 an operation sensor for detecting the brake operation of the brake operation device;    a weight sensor for detecting the weight of the truck body;    a controller, when the operation sensor detects the brake operation of the brake operation device, for deciding the value of the electric brake force in accordance with the detected value of the weight sensor; and    a motor drive part for inputting therein the value of the electric brake force to electrically brake the traveling motor.    
     
     
         3 . The lift truck as set forth in  claim 2 , wherein the controller includes: 
 a data table containing detection values of the weight sensor and electric brake force values respectively corresponding to the detection values; and    a read-out section for reading one of the electric brake force values from the data table based on the detected value of the weight sensor,    wherein the one of the electric brake force values is transferred to the motor drive part as a decided value.    
     
     
         4 . The lift truck as set forth in  claim 2 , wherein the controller further includes an operation part for calculating the electric brake force based on the detected value of the weight sensor; and 
 wherein the calculation result of the operation part is transferred to the motor drive part as a decided value.    
     
     
         5 . The lift truck as set forth in  claim 4 , wherein the brake controller comprises: 
 a speed sensor for detecting the traveling speed of the truck body;    wherein the operation part of the controller comprises: 
 a truck body weight operation portion for calculating the weight of the truck body based on the detected value of the weight sensor;  
 a traveling speed operation portion for calculating the traveling speed based on the detected value of the speed sensor;  
 a brake efficiency operation portion for calculating a brake efficiency based on the calculation result of the traveling speed operation portion; and  
 an electric brake force operation portion for calculating the electric brake force based on the calculation results of the truck body weight operation portion and the brake efficiency operation portion,  
   wherein the calculation result of the electric brake force operation portion is transferred to the motor drive part as a decided value.    
     
     
         6 . A lift truck as set forth in  claim 4 , wherein the operation part of the controller comprises: 
 a truck body weight operation portion for calculating the weight of the truck body based on the detected value of the weight sensor;    a traveling speed operation portion for calculating the traveling speed based on the detected value of the weight sensor,    a brake efficiency operation portion for calculating a brake efficiency based on the calculation result of the traveling speed operation portion; and    an electric brake force operation portion for calculating the electric brake force based on the calculation results of the truck body weight operation portion and the brake efficiency operation portion,    wherein the calculation result of the electric brake force operation portion is transferred to the motor drive part as a decided value.    
     
     
         7 . The lift truck as set forth in  claim 1 , wherein the electric brake is plugging or regenerative brake.  
     
     
         8 . A lift truck comprising: 
 a truck body;    a traveling motor for traveling the truck body;    an electromagnetic brake for braking rotation of the traveling motor;    a brake operation device to be operated for actuation of the electromagnetic brake; and,    a brake controller for detecting the brake operation of the brake operation device to actuate the electromagnetic brake,    wherein the brake controller, when the brake controller detects the brake operation of the brake operation device, actuates the electromagnetic brake and detects the traveling speed of the truck body, to electrically brake the traveling motor in such a manner that an electric brake force is increased or decreased in correspondence to the detected traveling speed.    
     
     
         9 . The lift truck as set forth in  claim 8 , wherein the brake controller comprises: 
 an operation sensor for detecting the brake operation of the brake operation device;    a speed sensor for detecting the traveling speed;    a controller, when the operation sensor detects the brake operation of the brake operation device, for deciding the value of the electric brake force in accordance with the detected value of the speed sensor; and    a motor drive part for inputting therein the value of the electric brake force to electrically brake the traveling motor.    
     
     
         10 . A lift truck as set forth in  claim 9 , wherein the controller includes: 
 a data table containing detection values of the speed sensor and electric brake force values respectively corresponding to the detection values; and    a read-out section for reading out one of the electric brake force values from the data table based on the detected value of the speed sensor,    wherein the one of the electric brake force values is transferred to the motor drive part as a decided value.    
     
     
         11 . Teh lift truck as set forth in  claim 9 , wherein the controller further comprises: 
 an operation part for calculating the electric brake force based on the detected value of the speed sensor,    wherein the calculation result of the operation part is transferred to the motor drive part as a decided value.    
     
     
         12 . The lift truck as set forth in  claim 11 , wherein the operation part comprises: 
 a traveling speed operation portion for calculating the traveling speed based on the detected value of the speed sensor,    a brake efficiency operation portion for calculating a brake efficiency based on the calculation result of the traveling speed operation portion; and    an electric brake force operation portion for calculating the electric brake force based on the calculation result of the brake efficiency operation portion,    wherein the calculation result of the electric brake force operation portion is transferred to the motor drive part as a decided value.    
     
     
         13 . A lift truck as set forth in  claim 8 , wherein the electric brake is plugging or regenerative brake.