The upper turntable of Hitachi excavator consists of main frame engine, fuel tank, hydraulic oil tank, hydraulic components (hydraulic pump, control valve, etc.), cab and counterweight. The counterweight is bolted to the rear end of the main frame to balance the machine. The front end τ is installed on the main frame.
One, hydraulic pump set
1. The engine power is transmitted to the gearbox through coupling 2, and then to the front 5, rear pump 6 and pilot spring 1. The gear ratio of the 3 pumps is 1:1:1. The gearbox is lubricated with gear oil. The main pump is a variable displacement inclined axis plunger pump. The main pump includes a front pump 5 and a rear pump 6, and is covered by a casing: the pilot pump 1 is a gear pump. The assembly of the front pump and the rear pump is called the main pump.
The shaft of each elephant is connected to 7 columns inserted into the cylinder. Thirdly, when the pump shaft rotates, the cylinder body also rotates. The rotation of the cylinder makes the plunger reciprocate in the cylinder, so that the hydraulic pump can absorb and press oil. The shaft 3 and the plunger 6 drive the cylinder 4. The plunger 6 moves in the cylinder barrel of the cylinder 4 and delivers hydraulic oil.
2. Main pump control oil circuit
Various signals 12 from the pressure sensor (P sensor) 4, the pump displacement angle sensor (A sensor) 3, and the engine speed sensor (N sensor) 9 are input to the controller 11, and the controller 11 determines according to the received signal The existing delivery flow of the pump is determined whether to increase or decrease, and appropriate control signals 10 are sent to the pump displacement solenoid valves 6 and 5. The pump displacement solenoid valves 6 and 5 are opened or closed to adjust the position of the servo piston 7 (pump displacement angle), thereby adjusting the output flow of the oil pump. The relationship is shown in Table 5-1.
3. Pilot pump and N sensor, P sensor, A sensor
(1) Pilot pump
The engine rotates the driving gear through the gear transfer case of the main pump. The driving gear drives the driven gear to rotate and drives the pilot
(2) Engine speed sensor (N sensor)
N sensor monitors the engine speed, which is important information for various operation control. The correct installation position of the N sensor is that its end is close to the top of the drive gear (the arrangement of the N sensor is shown in Figure 5-4). When a tooth top passes the top of the N sensor, the N sensor converts this information into a pulse electric signal, and the engine speed can be measured according to the pulse electric signal.
(3) Pressure sensor (P sensor)
P sensor is used to detect oil pressure. Oil pressure is important information for various operation controls. When the diaphragm of the sensor is deformed by the pressure of the oil, the P sensor can convert the degree of deformation of the diaphragm into an electrical signal
(4) Pump displacement angle sensor (A sensor)
The A sensor detects the displacement angle by detecting the movement of the shaft 2 and converts it into an electrical signal. The shaft 2 is connected to the cylinder of the main pump through a pin 5 and a lever 1.
