JPH0329559Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a power device that is installed in a construction machine such as a hydraulic excavator and has a prime mover that drives a variable displacement hydraulic pump.

[Background of the idea]

FIG. 4 is a circuit diagram showing an example of a conventional power device, which is installed in, for example, a hydraulic excavator. In this figure, 1 is the prime mover or engine, 5
3, 53' are variable displacement hydraulic pumps driven by this engine 1, 50, 51 are regulators that control the discharge amount of the variable displacement hydraulic pumps 53, 53', and 52 are actuators of these regulators 50, 51. This is a controller that outputs signals.
This controller 52 is a variable displacement hydraulic pump 5
Signal S for setting the maximum tilt angle of 3,53' to a large value
1 or a signal S2 which is set to a small value. 13 is a selection switch connected to the controller 52. Also,
7 and 7' are pipes that lead the oil discharged from the variable displacement hydraulic pumps 53 and 53' to the travel circuit, work machine circuit, etc.;
is a tank.

In a hydraulic excavator or the like equipped with this conventional power device, during so-called heavy excavation where a large amount of work is required, the above-mentioned signal is sent from the controller 52 by operating the selection switch 13. S1 is output to regulators 50 and 51,
As a result, the variable displacement hydraulic pumps 53, 53' are controlled so that the maximum tilt angle becomes large, and a large flow rate is discharged to the pipes 7, 7'. By switching the selection switch 13, the above signal S2 is outputted from the controller 52 to the regulators 50 and 51.
As a result, the variable displacement hydraulic pumps 53, 53' are controlled to have a small maximum tilt angle, and discharge a small flow rate to the pipes 7, 7'.

FIG. 5 is an explanatory diagram showing the relationship between the discharge flow rate and the discharge pressure of the variable displacement hydraulic pump shown in FIG. 4, where 10 is the characteristic line during heavy excavation etc. mentioned above, and 11 is the characteristic line during light excavation etc. mentioned above. , 12 indicate engine horsepower characteristic lines. In this way, the discharge flow rate is varied in accordance with the discharge pressure so that the hydraulic horsepower, which is proportional to the product of the discharge flow rate and the discharge pressure, does not exceed the engine horsepower characteristic line 12.

FIG. 6 is an explanatory diagram showing the relationship between engine speed, engine torque, and fuel consumption rate (g/psh) in the conventional power plant described above. In the figure,
23 and 24 indicate engine torque characteristic lines, 33 indicates a pump torque characteristic line during heavy excavation, etc., 34 indicates a pump torque characteristic line during light excavation, etc., and 26 and 27 indicate fuel consumption. It shows the rate characteristic line.

As shown in FIG. 6, in the conventional power unit, when changing the work mode from heavy excavation etc. to light excavation etc., the maximum rotation speed of the engine 1 is maintained as it is, and the hydraulic pump 53, 53' is changed from large to small, that is, the pump torque characteristic line 33 is changed to the pump torque characteristic line 34, thereby changing the engine torque characteristic line 23, 2.
4 and the matching point 20 of the pump torque characteristic line 33
From the matching point 30 on the fuel consumption rate characteristic lines 26, 27 corresponding to the engine torque characteristic lines 23,
Matching point 2 between 24 and pump torque characteristic line 34
There is a problem in that the fuel consumption rate (g/psh) deteriorates and energy saving cannot be achieved.

In addition, when changing the work mode mentioned above, the maximum rotation speed of the engine 1 is kept constant, so even during light excavation, etc., large noise is generated.
There is also a problem in terms of the durability of the engine 1 and the hydraulic pumps 2, 2'.

[Purpose of invention]

The present invention was developed in view of the above-mentioned actual situation in the prior art, and its purpose is to provide a power unit that can maintain the same amount of work as before when changing work modes even when the maximum engine speed is lowered. It is about providing.

[Summary of the idea]

To achieve this objective, the present invention provides a power plant comprising a prime mover and a variable displacement hydraulic pump driven by the prime mover, in which multiple maximum revolutions of the prime mover are set based on the type of work. A first maximum rotational speed that is a combination of a first maximum rotational speed predetermined based on heavy work among the numbers and a maximum tilting angle of the variable displacement hydraulic pump within a range that does not exceed the output torque of the first maximum rotational speed. In addition to setting the mode,
A second maximum rotation speed that is predetermined based on light work among the plurality of maximum rotation speeds and is smaller than the first maximum rotation speed, and a variable range that does not exceed the output torque of the second maximum rotation speed. a setting means for setting a second mode in combination with a second maximum tilting angle larger than the first maximum tilting angle predetermined among the plurality of maximum tilting angles of the capacity hydraulic pump;
The configuration is such that the prime mover is selectively driven in accordance with the set value set by the setting means to control the discharge amount of the variable displacement hydraulic pump.

[Example of idea]

Hereinafter, the power plant of the present invention will be explained based on the drawings. FIG. 1 is a circuit diagram showing an embodiment of the present invention. Components equivalent to those shown in FIG. 4 described above are designated by the same reference numerals.

In this figure, 4 is a fuel lever that sets the maximum rotation speed of the engine 1, 5 is a maximum rotation speed selection device that prevents the fuel lever 4 from moving beyond a predetermined maximum rotation speed, and 3 and 3' are A regulator 6 is a controller to which the regulators 3, 3' and the maximum rotational speed selection device 5 are connected. This controller 6 sets a large value as the maximum rotational speed of the engine 1 in a memory area corresponding to a work mode such as heavy excavation, and sets a large value as the maximum rotational speed of the hydraulic pumps 2, 2' as shown in FIG. As exemplified by the characteristic line 41 in the explanatory diagram showing the relationship between the pump tilt angle and the discharge pressure, a small value is set and these are combined as one, and a memory area corresponding to the work mode such as during light excavation is set. , the maximum rotational speed of the engine 1 is set to a small value, and the maximum tilting angle of the hydraulic pumps 2, 2' is set to a large value as exemplified by the characteristic line 40 in FIG. It is provided with a setting means for the combination, and an output means for selectively outputting the value set by the setting means to the regulators 3, 3' and the maximum rotation speed selection device 5. Note that 13 is a selection switch similar to the above-mentioned one for selecting a work mode, and is connected to the controller 6.

In the embodiment configured in this way, when the switch 13 is operated during heavy excavation, etc.
The controller 6 outputs a signal to the regulators 3, 3' to reduce the maximum tilt angle of the variable displacement hydraulic pumps 2, 2' as shown in the characteristic line 41 in FIG. A signal for increasing the maximum rotational speed of the engine 1 is output to the device 5. Assuming that the maximum rotational speed of the engine 1 and the maximum tilting angle of the hydraulic pumps 2, 2' at this time are the same as those in the device shown in FIG. 4 described above, the relationship between the pump discharge flow rate and the discharge pressure is
As shown by the characteristic line 42 in the figure, it coincides with the characteristic line 10 shown in FIG. 5 described above. Furthermore, when the switch 13 is operated during light excavation, etc., the maximum tilt angle of the variable displacement hydraulic pumps 2, 2' is transmitted from the controller 6 to the regulators 3, 3' according to the characteristic line 40 in FIG.
A signal to increase the maximum rotational speed of the engine 1 is outputted as shown in FIG. A characteristic line 43 shown by a broken line in FIG. 3 shows the relationship between the pump discharge flow rate and the discharge pressure at this time, and can be made almost the same as the characteristic line 11 shown in FIG. 5 described above.

The above is clear from Fig. 6, and in this example, the engine torque characteristics were as indicated by numerals 23 and 24 during heavy excavation, but during light excavation, etc. The engine torque characteristic line moves to those indicated by symbols 23 and 25, the pump torque characteristic line remains constant at 33, and these characteristic lines 2
The matching point, which is the intersection of No. 3 and 25 with the characteristic line 33, shifts from the one indicated by the reference numeral 20 to the one indicated by the reference numeral 22, and the matching point 22 is on the constant horsepower curve 29. And in this example,
During light excavation, etc., as the maximum rotation speed of engine 1 is limited to a small value, the fuel consumption rate characteristic line changes to sign 2.
The matching points on the fuel consumption rate characteristic lines 26 and 28 shift from those indicated by numerals 6 and 27 to those indicated by numerals 26 and 28, and corresponding to the above-mentioned matching point 22, the matching points on the fuel consumption rate characteristic lines 26 and 28 change from those indicated by numerals 30 to those indicated by numerals 32. move on to things. Therefore, since the matching point 21 in the conventional power plant shown in FIG. 4 and the matching point 22 in this embodiment are on the same constant horsepower curve 29, the fuel difference between the conventional power plant and this embodiment is The difference in consumption (/h) is determined by fuel consumption rate characteristic line 2.
The difference between the value of the matching point 31 on the fuel consumption rate characteristic lines 26 and 27 and the value of the matching point 32 on the fuel consumption rate characteristic lines 26 and 28 is multiplied by horsepower, and energy can be saved by this amount.

In addition, in this embodiment, as mentioned above, the maximum rotational speed of the engine 1 can be limited to a small value during light excavation, etc., so that the generation of noise at this time can be suppressed, and the engine 1 Also, the durability of the variable displacement hydraulic pumps 2, 2' can be improved.

[Effect of idea]

Since the power unit of the present invention is configured as described above, it is possible to maintain the same amount of work as before when changing the work mode even if the maximum engine speed is lowered, thus realizing energy savings compared to the conventional method. This has the effect of suppressing noise and improving the durability of the engine and variable displacement hydraulic pump.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing one embodiment of the power device of the present invention, Fig. 2 is an explanatory diagram showing the relationship between the pump tilt angle and discharge pressure set in the embodiment shown in Fig. 1, and Fig. 3. is an explanatory diagram showing the relationship between pump discharge flow rate and discharge pressure obtained in the embodiment shown in FIG. 1, FIG. 4 is a circuit diagram showing an example of a conventional power plant, and FIG. 5 is a diagram showing the relationship between the pump discharge flow rate and discharge pressure obtained in the embodiment shown in FIG. FIG. 6 is an explanatory diagram showing the relationship between the pump discharge flow rate and discharge pressure obtained in the example shown in FIG. 1 and the conventional power plant shown in FIG. 4. FIG. 1... Prime mover (engine), 2, 2'... Variable displacement hydraulic pump, 3, 3'... Regulator, 4...
...Fuel lever, 5...Maximum rotation speed selection device, 6...
...Controller, 13...Selection switch, 20,
22, 30, 32...Matching point, 23, 25
... Engine torque characteristic line, 26, 28 ... Fuel consumption rate characteristic line, 29 ... Horsepower constant curve, 40 ...
Characteristic line.

Claims (1)

[Scope of utility model registration request] In a power device equipped with a prime mover and a variable displacement hydraulic pump driven by the prime mover, a predetermined number of rotations is selected based on heavy work among a plurality of maximum rotational speeds of the prime mover set based on the type of work. A first mode that combines a maximum rotational speed of 1 and a maximum tilting angle of the variable displacement hydraulic pump within a range that does not exceed the output torque of the first maximum rotational speed is set, and a first mode that combines the maximum rotational speed of the plurality of maximum rotational speeds A plurality of variable displacement hydraulic pumps having a second maximum rotation speed that is predetermined based on light work and is smaller than the first maximum rotation speed, and an output torque within a range that does not exceed the output torque of the second maximum rotation speed. A setting means for setting a second mode in combination with a second maximum tilt angle larger than the first maximum tilt angle predetermined among the maximum tilt angles; A power unit that selectively drives the prime mover according to a set value to control a discharge amount of the variable displacement hydraulic pump.