CPC E02F 9/2253 (2013.01) [E02F 9/2246 (2013.01); E02F 9/225 (2013.01); E02F 9/2292 (2013.01)] | 13 Claims |
1. A working machine comprising:
a machine body;
a prime mover provided on the machine body;
a left traveling device provided on a left portion of the machine body;
a right traveling device provided on a right portion of the machine body;
a left traveling motor configured to output power to the left traveling device and to be rotated at a speed stage shiftable between a first speed and a second speed higher than the first speed;
a right traveling motor configured to output power to the right traveling device and to be rotated at a speed stage shiftable between the first speed and the second speed higher than the first speed;
a left traveling pump to supply operation fluid to the left traveling motor, the left traveling pump having a first port to output the operation fluid for forward rotation of the left traveling motor and a second port to output the operation fluid for reverse rotation of the left traveling motor;
a right traveling pump to supply the operation fluid to the right traveling motor, the right traveling pump having a third port to output the operation fluid for forward rotation of the right traveling motor and a fourth port to output the operation fluid for reverse rotation of the right traveling motor;
a first circulation fluid line fluidly connecting the left traveling pump to the left traveling motor, the first circulation fluid line including a first passage connecting the first port of the left traveling pump to a first port of the left traveling motor, and a second passage connecting the second port of the left traveling pump to a second port of the left traveling motor;
a second circulation fluid line fluidly connecting the right traveling pump to the right traveling motor, the second circulation fluid line including a third passage connecting the third port of the right traveling pump to a third port of the right traveling motor, and a fourth passage connecting the fourth port of the right traveling pump to a fourth port of the right traveling motor;
a first pressure detector provided on the first passage and configured to detect a first traveling pressure that is a pressure of the operation fluid applied to the first passage when the left traveling motor rotates;
a second pressure detector provided on the second passage and configured to detect a second traveling pressure that is a pressure of the operation fluid applied to the second passage when the left traveling motor rotates;
a third pressure detector provided on the third passage and configured to detect a third traveling pressure that is a pressure of the operation fluid applied to the third passage when the right traveling motor rotates;
a fourth pressure detector provided on the fourth passage and configured to detect a fourth traveling pressure that is a pressure of the operation fluid applied to the fourth passage when the right traveling motor rotates;
a controller configured to judge a traveling state of the machine body including whether the machine body is turning or not based on the first traveling pressure, the second traveling pressure, the third traveling pressure, the fourth traveling pressure, and a first threshold, and to change the first threshold;
a first relief valve connected to the first passage;
a second relief valve connected to the second passage;
a third relief valve connected to the third passage; and
a fourth relief valve connected to the fourth passage, wherein
the controller acquires a first traveling relief pressure of the first relief valve, a second traveling relief pressure of the second relief valve, a third traveling relief pressure of the third relief valve, and a fourth traveling relief pressure of the fourth relief valve, the first, second, third and fourth traveling relief pressures being determined in correspondence to a rotation speed of the prime mover, and
the controller determines the first threshold based on a first differential pressure, a second differential pressure, a third differential pressure, and a fourth differential pressure, the first differential pressure being calculated by subtracting the third traveling relief pressure from the first traveling relief pressure, the second differential pressure being calculated by subtracting the first traveling relief pressure from the third traveling relief pressure, the third differential pressure being calculated by subtracting the fourth traveling relief pressure from the second traveling relief pressure, and the fourth differential pressure being calculated by subtracting the second traveling relief pressure from the fourth traveling relief pressure.
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