Working machine
First Claim
Patent Images
1. A working machine comprising:
- an engine;
a travelling device;
a hydro static transmission (HST) pump composed of a tilted-plate type variable capacity pump driven by the engine;
an HST motor connected to the HST pump and a pair of gear-changing oil passages to form a closed circuit with the HST pump and the pair of gear-changing oil passages, the HST motor being configured to be driven by a discharge oil from the HST pump to drive the travelling device;
a pilot pump driven by the engine;
a travel operation device configured to control a tilted plate of the HST pump due to a pilot oil discharged by the pilot pump;
a pressure control valve configured to control a travel primary side pressure, the travel primary side pressure being a pressure of a primary side of the travel operation device;
an acceleration operating member for increasing and decreasing an engine speed of the engine to determine a target engine speed; and
a control unit configured to control the pressure control valve, the control unit including;
a no-load characteristic line showing a relationship, under a condition where the engine is unloaded, between the travel primary side pressure and a real engine speed that is an actual speed of the engine; and
a drop characteristic line provided for each of the target engine speeds determined by the acceleration operating member, the drop characteristic line showing a relationship, under a condition where a predefined load or more is applied to the engine, between the travel primary side pressure and the real engine speed, and the drop characteristic line including;
a first characteristic line portion used for decreasing the travel primary side pressure on a basis of a difference between the real engine speed and the target engine speed, the target engine speed being a speed of the engine determined by the acceleration operating member; and
a second characteristic line portion used for decreasing the travel primary side pressure on a basis of a difference between the real engine speed and the target engine speed and at a rate smaller than a rate for decreasing the travel primary side pressure in the first characteristic line portion,wherein the control unit is configured to control the pressure control valve on a basis of the no-load characteristic line when the engine is unloaded and to control the pressure control valve on a basis of the first characteristic line portion and the second characteristic line portion when a predetermined load or more is applied to the engine.
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Accused Products
Abstract
A pressure control valve for controlling a travel primary side pressure that is a pressure of a primary side of a travel operation device is controlled by a control unit, thus the travel primary side pressure is controlled, and thereby a traveling speed is intended to be increased, preventing an engine stall.
35 Citations
4 Claims
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1. A working machine comprising:
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an engine; a travelling device; a hydro static transmission (HST) pump composed of a tilted-plate type variable capacity pump driven by the engine; an HST motor connected to the HST pump and a pair of gear-changing oil passages to form a closed circuit with the HST pump and the pair of gear-changing oil passages, the HST motor being configured to be driven by a discharge oil from the HST pump to drive the travelling device; a pilot pump driven by the engine; a travel operation device configured to control a tilted plate of the HST pump due to a pilot oil discharged by the pilot pump; a pressure control valve configured to control a travel primary side pressure, the travel primary side pressure being a pressure of a primary side of the travel operation device; an acceleration operating member for increasing and decreasing an engine speed of the engine to determine a target engine speed; and a control unit configured to control the pressure control valve, the control unit including; a no-load characteristic line showing a relationship, under a condition where the engine is unloaded, between the travel primary side pressure and a real engine speed that is an actual speed of the engine; and a drop characteristic line provided for each of the target engine speeds determined by the acceleration operating member, the drop characteristic line showing a relationship, under a condition where a predefined load or more is applied to the engine, between the travel primary side pressure and the real engine speed, and the drop characteristic line including; a first characteristic line portion used for decreasing the travel primary side pressure on a basis of a difference between the real engine speed and the target engine speed, the target engine speed being a speed of the engine determined by the acceleration operating member; and a second characteristic line portion used for decreasing the travel primary side pressure on a basis of a difference between the real engine speed and the target engine speed and at a rate smaller than a rate for decreasing the travel primary side pressure in the first characteristic line portion, wherein the control unit is configured to control the pressure control valve on a basis of the no-load characteristic line when the engine is unloaded and to control the pressure control valve on a basis of the first characteristic line portion and the second characteristic line portion when a predetermined load or more is applied to the engine. - View Dependent Claims (2, 3, 4)
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Specification