CONSTRUCTION MACHINE HYDRAULIC DRIVE SYSTEM HAVING EXHAUST GAS PURIFYING DEVICE

• US 20140165543A1
• Filed: 10/02/2012
• Published: 06/19/2014
• Est. Priority Date: 10/04/2011
• Status: Active Grant

• Current Assignee: Hitachi Construction Machinery Tierra Co.,Ltd. (Hitachi Construction Machinery (China) Co., Ltd.)
• Original Assignee: Hitachi Construction Machinery Company Limited (Hitachi, Ltd.)
• Inventors: Takebayashi, Yoshifumi, Takahashi, Kiwamu, Mori, Kazushige, Nakamura, Natsuki
• Granted Patent: US 9,080,481 B2
• Time in Patent Office: Days
• US Class Current: 60/311
• CPC Class Codes: E02F 3/325 Backhoes of the miniature type
• CPC Class Codes: E02F 9/2066 of the type combustion engines
• CPC Class Codes: E02F 9/2228 including an electronic controller
• CPC Class Codes: E02F 9/2235 including an electronic controller
• CPC Class Codes: E02F 9/2285 Pilot-operated systems
• CPC Class Codes: E02F 9/2296 Systems with a variable displacement pump
• CPC Class Codes: F01N 3/023 using means for regenerating the filters, e.g. by burning trapped particles by electrically controlling the supply of combustible mixture or its constituents only F02D41/0235
• CPC Class Codes: F01N 3/0253 adding fuel to exhaust gases
• CPC Class Codes: F01N 9/002 of filter regeneration, e.g. detection of clogging
• CPC Class Codes: F02D 2200/0812 Particle filter loading
• CPC Class Codes: F02D 29/04 peculiar to engines driving pumps
• CPC Class Codes: F02D 41/029 the exhaust gas treating apparatus being a particulate filter
• CPC Class Codes: F02D 41/406 Electrically controlling a diesel injection pump F02D41/401 takes precedence
• CPC Class Codes: F15B 15/18 Combined units comprising both motor and pump
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A construction machine hydraulic drive system that performs load sensing control is capable of efficiently burning and removing deposits on a filter in an exhaust gas purifying device through pump output increasing control and to be free from faults in the pump output increasing control even when an actuator is operated during the pump output increasing control. A solenoid switching valve is switched so that output pressure of an engine speed detecting valve is guided to a pressure receiving portion of an LS control valve and a pressure receiving portion of an unloading valve when a start of regeneration is not directed, and delivery pressure of a pilot pump is guided to the pressure receiving portion and the pressure receiving portion when the start of the regeneration is directed, to thereby disable load sensing control to increase capacity of a main pump and increase set pressure of the unloading valve.

Claims

1. A construction machine hydraulic drive system including:

an engine (1);

a variable displacement hydraulic pump (2) driven by the engine;

a plurality of actuators (3a, 3b, 3c . . . ) driven by hydraulic fluid delivered from the hydraulic pump;

a plurality of flow and directional control valves (6a, 6b, 6c . . . ) that control a flow rate of the hydraulic fluid supplied from the hydraulic pump to the actuators;

a pump control device (17) including;

a torque control section (17-1) that performs absorption torque maintaining control that prevents absorption torque of the hydraulic pump from exceeding predetermined maximum torque (Tmax) by reducing capacity of the hydraulic pump as delivery pressure of the hydraulic pump increases; and

a load sensing control section (17-2) that performs load sensing control that ensures that the delivery pressure of the hydraulic pump is higher than maximum load pressure of the actuators by target differential pressure;

an unloading valve (15) connected to a line (4a) to which a delivery fluid from the hydraulic pump is guided, the unloading valve opening when the delivery pressure of the hydraulic pump is higher than the sum of the maximum load pressure and an unloading set pressure, to thereby return the delivery fluid of the hydraulic pump to a tank (T), thus restricting an increase in the delivery pressure of the hydraulic pump; and

a pilot pump (30) driven by the engine, the hydraulic drive system comprising;

an exhaust gas purifying device (42) that purifies exhaust gases from the engine;

an instruction device (43, 44, S100) that directs a start of regeneration of the exhaust gas purifying device; and

a changeover control device (17d, 15d, 35, 70, S110) that selects to enable or disable the load sensing control performed by the load sensing control section by enabling the load sensing control of the load sensing control section when the instruction device does not direct the start of the regeneration of the exhaust gas purifying device and disabling the load sensing control of the load sensing control section when the instruction device directs the start of the regeneration of the exhaust gas purifying device to thereby increase the capacity of the hydraulic pump;

when disabling the load sensing control, by guiding predetermined pressure generated based on the delivery fluid of the pilot pump to the unloading valve to thereby increase the unloading set pressure.

2. The construction machine hydraulic drive system according to claim 1, further comprising:

a pilot hydraulic source (38) connected to the pilot pump, the pilot hydraulic source generating pilot primary pressure based on the delivery fluid of the pilot pump; and

an engine speed detecting valve (13) disposed between the pilot pump and the pilot hydraulic source, the engine speed detecting valve generating a hydraulic signal dependent on a speed of the engine based on the delivery fluid of the pilot pump, wherein

the load sensing control section (17-2) of the pump control device (17) includes an LS control valve (17b) that includes a first pressure receiving portion (17d) to which the hydraulic signal of the engine speed detecting valve is guided, the first pressure receiving portion being operative in a direction in which pump capacity increases to thereby set target differential pressure of the load sensing control using the hydraulic signal,

the unloading valve (15) includes a spring (15a) operative in a closing direction and a pressure receiving portion (15d) operative in a closing direction to cooperate with the spring and set the unloading set pressure, and

the changeover control device (17d, 15d, 35, 70, S110) guides the hydraulic signal generated by the engine speed detecting valve to the pressure receiving portion of the unloading valve when the instruction device (43, 44, S100) does not direct the start of the regeneration of the exhaust gas purifying device (42), and guides the delivery pressure of the pilot pump to the pressure receiving portion of the unloading valve as the predetermined pressure when the instruction device directs the start of the regeneration of the exhaust gas purifying device.

3. The construction machine hydraulic drive system according to claim 2, further comprising:

a differential pressure reducing valve (11) that generates and outputs differential pressure between the delivery pressure of the hydraulic pump (2) and the maximum load pressure, with the hydraulic pressure of the pilot hydraulic source (38) as a primary pressure, as an absolute pressure to the pump control device (17), wherein

the LS control valve (17b) further includes a second pressure receiving portion (17e) operative in a direction in which the pump capacity decreases, the second pressure receiving portion receiving the absolute pressure output from the differential pressure reducing valve guided thereto, and

when the instruction device (43, 44, S100) directs the start of the regeneration of the exhaust gas purifying device (42), the changeover control device (17d, 15d, 35, 70, S110) guides the delivery pressure of the pilot pump (30) instead of the hydraulic signal of the engine speed detecting valve (13) to the first pressure receiving portion (17d) of the LS control valve to thereby disable the load sensing control, thus controlling to increase the capacity of the hydraulic pump.

4. The construction machine hydraulic drive system according to claim 3, wherein the changeover control device (17d, 15d, 35, 70, S110) includes a single switching valve (70) that changes a position thereof so that, when the instruction device (43, 44, S100) does not direct the start of the regeneration of the exhaust gas purifying device (42), the hydraulic signal of the engine speed detecting valve (13) is guided to the first pressure receiving portion (17d) of the LS control valve (17b) and the pressure receiving portion (15d) of the unloading valve (15) and, when the instruction device directs the start of the regeneration of the exhaust gas purifying device, the delivery pressure of the pilot pump is guided to the first pressure receiving portion of the LS control valve and the pressure receiving portion of the unloading valve.

5. The construction machine hydraulic drive system according to claim 1, further comprising:

a pressure detecting device (43) that detects exhaust resistance in the exhaust gas purifying device (42), wherein

the instruction device (43, 44, S100) directs the start of the regeneration of the exhaust gas purifying device when the exhaust resistance of the exhaust gas purifying device detected by the pressure detecting device exceeds a threshold value (Δ

Pb).

6. The construction machine hydraulic drive system according to claim 1, wherein

the torque control section (17-1) of the pump control device (17) is configured so as to control the capacity of the hydraulic pump so that, with characteristics set in advance, the characteristics indicating a relation between the delivery pressure and the capacity of the hydraulic pump (2) and comprising a maximum capacity maintaining characteristic and a maximum absorption torque maintaining characteristic, when the delivery pressure of the hydraulic pump is equal to, or lower than, a first value (P0) as pressure at a transition point from the maximum capacity maintaining characteristic to the maximum absorption torque maintaining characteristic, the maximum capacity of the hydraulic pump is made to remain constant even when the delivery pressure of the hydraulic pump increases, and when the delivery pressure of the hydraulic pump increases to exceed the first value, the maximum capacity of the hydraulic pump decreases according to the maximum absorption torque maintaining characteristic, and

the predetermined pressure is set so that a sum of the unloading set pressure of the unloading valve (15) increased by the predetermined pressure and pressure generated by an override characteristic of the unloading valve is a value equal to, or greater than, pressure near the transition point from the maximum capacity maintaining characteristic to the maximum absorption torque maintaining characteristic.

7. The construction machine hydraulic drive system according to claim 2, further comprising:

a pressure detecting device (43) that detects exhaust resistance in the exhaust gas purifying device (42), wherein

the instruction device (43, 44, S100) directs the start of the regeneration of the exhaust gas purifying device when the exhaust resistance of the exhaust gas purifying device detected by the pressure detecting device exceeds a threshold value (Δ

Pb).

8. The construction machine hydraulic drive system according to claim 3, further comprising:

a pressure detecting device (43) that detects exhaust resistance in the exhaust gas purifying device (42), wherein

the instruction device (43, 44, S100) directs the start of the regeneration of the exhaust gas purifying device when the exhaust resistance of the exhaust gas purifying device detected by the pressure detecting device exceeds a threshold value (Δ

Pb).

9. The construction machine hydraulic drive system according to claim 4, further comprising:

a pressure detecting device (43) that detects exhaust resistance in the exhaust gas purifying device (42), wherein

the instruction device (43, 44, S100) directs the start of the regeneration of the exhaust gas purifying device when the exhaust resistance of the exhaust gas purifying device detected by the pressure detecting device exceeds a threshold value (Δ

Pb).

10. The construction machine hydraulic drive system according to claim 2, wherein

the torque control section (17-1) of the pump control device (17) is configured so as to control the capacity of the hydraulic pump so that, with characteristics set in advance, the characteristics indicating a relation between the delivery pressure and the capacity of the hydraulic pump (2) and comprising a maximum capacity maintaining characteristic and a maximum absorption torque maintaining characteristic, when the delivery pressure of the hydraulic pump is equal to, or lower than, a first value (P0) as pressure at a transition point from the maximum capacity maintaining characteristic to the maximum absorption torque maintaining characteristic, the maximum capacity of the hydraulic pump is made to remain constant even when the delivery pressure of the hydraulic pump increases, and when the delivery pressure of the hydraulic pump increases to exceed the first value, the maximum capacity of the hydraulic pump decreases according to the maximum absorption torque maintaining characteristic, and

the predetermined pressure is set so that a sum of the unloading set pressure of the unloading valve (15) increased by the predetermined pressure and pressure generated by an override characteristic of the unloading valve is a value equal to, or greater than, pressure near the transition point from the maximum capacity maintaining characteristic to the maximum absorption torque maintaining characteristic.

11. The construction machine hydraulic drive system according to claim 3, wherein

the torque control section (17-1) of the pump control device (17) is configured so as to control the capacity of the hydraulic pump so that, with characteristics set in advance, the characteristics indicating a relation between the delivery pressure and the capacity of the hydraulic pump (2) and comprising a maximum capacity maintaining characteristic and a maximum absorption torque maintaining characteristic, when the delivery pressure of the hydraulic pump is equal to, or lower than, a first value (P0) as pressure at a transition point from the maximum capacity maintaining characteristic to the maximum absorption torque maintaining characteristic, the maximum capacity of the hydraulic pump is made to remain constant even when the delivery pressure of the hydraulic pump increases, and when the delivery pressure of the hydraulic pump increases to exceed the first value, the maximum capacity of the hydraulic pump decreases according to the maximum absorption torque maintaining characteristic, and

the predetermined pressure is set so that a sum of the unloading set pressure of the unloading valve (15) increased by the predetermined pressure and pressure generated by an override characteristic of the unloading valve is a value equal to, or greater than, pressure near the transition point from the maximum capacity maintaining characteristic to the maximum absorption torque maintaining characteristic.

12. The construction machine hydraulic drive system according to claim 4, wherein

the torque control section (17-1) of the pump control device (17) is configured so as to control the capacity of the hydraulic pump so that, with characteristics set in advance, the characteristics indicating a relation between the delivery pressure and the capacity of the hydraulic pump (2) and comprising a maximum capacity maintaining characteristic and a maximum absorption torque maintaining characteristic, when the delivery pressure of the hydraulic pump is equal to, or lower than, a first value (P0) as pressure at a transition point from the maximum capacity maintaining characteristic to the maximum absorption torque maintaining characteristic, the maximum capacity of the hydraulic pump is made to remain constant even when the delivery pressure of the hydraulic pump increases, and when the delivery pressure of the hydraulic pump increases to exceed the first value, the maximum capacity of the hydraulic pump decreases according to the maximum absorption torque maintaining characteristic, and

the predetermined pressure is set so that a sum of the unloading set pressure of the unloading valve (15) increased by the predetermined pressure and pressure generated by an override characteristic of the unloading valve is a value equal to, or greater than, pressure near the transition point from the maximum capacity maintaining characteristic to the maximum absorption torque maintaining characteristic.

13. The construction machine hydraulic drive system according to claim 5, wherein

the torque control section (17-1) of the pump control device (17) is configured so as to control the capacity of the hydraulic pump so that, with characteristics set in advance, the characteristics indicating a relation between the delivery pressure and the capacity of the hydraulic pump (2) and comprising a maximum capacity maintaining characteristic and a maximum absorption torque maintaining characteristic, when the delivery pressure of the hydraulic pump is equal to, or lower than, a first value (P0) as pressure at a transition point from the maximum capacity maintaining characteristic to the maximum absorption torque maintaining characteristic, the maximum capacity of the hydraulic pump is made to remain constant even when the delivery pressure of the hydraulic pump increases, and when the delivery pressure of the hydraulic pump increases to exceed the first value, the maximum capacity of the hydraulic pump decreases according to the maximum absorption torque maintaining characteristic, and

the predetermined pressure is set so that a sum of the unloading set pressure of the unloading valve (15) increased by the predetermined pressure and pressure generated by an override characteristic of the unloading valve is a value equal to, or greater than, pressure near the transition point from the maximum capacity maintaining characteristic to the maximum absorption torque maintaining characteristic.