JP2008267364A - Engine control device for hydraulic working machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine control device for a hydraulic working machine capable of quickening response of engine speed to load fluctuation, reducing fluctuation of engine speed and improving fuel consumption. <P>SOLUTION: This engine control device is provided with a controller outputting command signal to an engine controller of the hydraulic working machine, a pressure sensor driven by an engine controlled by the engine controller and detecting delivery pump pressure of a hydraulic pump, and a pressure sensor detecting negative control pressure of a circuit in which delivery oil of the hydraulic pump. The controller outputs command signal based on engine set speed corrected by engine load estimated from the delivery pump pressure and negative control pressure to the engine controller. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an engine control device for a hydraulic working machine such as a hydraulic excavator.

  Hydraulic excavators, such as hydraulic excavators, that perform work by operating actuators with the discharge oil of a hydraulic pump driven by the engine, have a large fluctuation in work load. An engine control device for so-called speed sensing control is provided that controls the engine speed, the maximum absorption torque of the hydraulic pump, and the like based on the deviation between the target speed and the actual speed (see, for example, Patent Document 1).

JP 2004-108155 A

  However, the conventional engine control device for a hydraulic working machine in the form as described above has the following problems to be solved.

  In other words, since the engine speed changes after a load is applied to the engine, a hydraulic excavator with particularly large fluctuations in work load is used in speed sensing control in which the engine speed is controlled by feeding back the actual engine speed to the control system. In such hydraulic working machines, the response of the engine speed control system to the fluctuation of the load becomes slow, resulting in a large change in the engine speed and poor fuel consumption.

  The present invention has been made in view of the above-described facts, and its technical problem is that it can accelerate the response to load fluctuations in the engine speed, reduce changes in the engine speed, and improve fuel consumption. An engine control device for a work machine is provided.

  According to the present invention, as an engine control device for a hydraulic working machine that solves the above technical problem, the engine is driven by a controller that outputs a command signal to the engine controller of the hydraulic working machine, and an engine controlled by the engine controller. An engine that includes a pressure sensor that detects a discharge pump pressure of a hydraulic pump and a pressure sensor that detects a negative control pressure of a circuit through which the discharge oil of the hydraulic pump flows, and the controller estimates from the discharge pump pressure and the negative control pressure An engine control device for a hydraulic working machine is provided that outputs a command signal based on an engine set speed corrected by a load to an engine controller.

  Preferably, switching means for switching the governor characteristic of the engine so as to be selectable is provided, and the controller further corrects the engine set speed based on the selected governor characteristic. Further, the hydraulic working machine includes a plurality of hydraulic pumps driven by the engine, and includes one pressure sensor for guiding the discharge pump pressure of the plurality of hydraulic pumps and one pressure sensor for guiding the negative control pressure. Each of these pressure sensors is provided with an orifice in each signal oil passage for guiding the discharge pump pressure or the negative control pressure.

  In the engine control device for a hydraulic working machine configured according to the present invention, the controller sets an engine set rotational speed corrected by an engine load estimated in advance from a discharge pump pressure and a negative control pressure of a hydraulic pump driven by the engine. The command signal based on is output.

  Therefore, compared to the conventional speed sensing control in which the actual engine speed is fed back to the control system to control the engine, the feedforward signal based on the engine set speed corrected by the engine load estimated in advance is transmitted to the engine controller. Therefore, it is possible to speed up the response to load fluctuations in the engine speed, reduce the change in engine speed, and improve fuel consumption.

  Hereinafter, an engine control device for a hydraulic working machine configured according to the present invention will be described in more detail with reference to the accompanying drawings illustrating preferred embodiments.

  A description will be given with reference to FIG. The engine control apparatus generally indicated by numeral 20 detects the controller 13 that controls the engine controller 1a of the engine 1 and the discharge pump pressure Pp of the pair of hydraulic pumps 3 and 4 that are driven by the engine 1. A pressure sensor 10 for input and a pressure sensor 12 for detecting a negative control pressure Pn of a circuit through which oil discharged from the hydraulic pumps 3 and 4 flows and inputting the detected pressure to the controller 13 are provided.

  The output shaft of the engine 1 is connected to the hydraulic pumps 3 and 4 via the pump drive 2. One hydraulic pump 3 is connected to a pilot pump 5 that discharges pilot hydraulic pressure mainly used for a control system such as steering. Between the engine 1 and the pump drive 2, there is provided a rotation sensor 14 that detects the actual rotational speed of the engine 1 and inputs it to the controller 13.

  The hydraulic pumps 3 and 4 are swash plate type variable displacement pumps. The hydraulic pump 3 includes a swash plate controller 3a, and the hydraulic pump 4 includes a swash plate controller 4a. The swash plate controllers 3a and 4a are connected to pilot control oil from an electromagnetic proportional control valve 8 which is controlled by the output from the controller 13 and controls the swash plate angle of the pump.

  A known discharge flow rate of the hydraulic pump is controlled at the outlet side of the center bypass passage of the multiple control valve 6 for controlling the operation of the hydraulic actuator provided in the circuit through which the discharge oil of each of the hydraulic pumps 3 and 4 flows. Relief valves 7a and 7b for generating negative control pressure for negative control are provided. The negative control pressure defined by the pressure upstream of the relief valve 7a is connected to the swash plate controller 3a by the signal oil passage 7c, and the negative control pressure upstream of the relief valve 7b is connected to the swash plate controller 4a by the signal oil passage 7d. ing.

  One pressure sensor 12 for detecting the negative control pressure Pn and inputting the negative control pressure Pn to the controller 13 is provided, and the negative control pressure Pn of the circuit through which the oil discharged from the hydraulic pumps 3 and 4 flows is connected to the pressure sensor 12 as signal oil paths 7c and 7d, respectively. Are routed through signal oil passages 7e and 7f. The signal oil passage 7e is provided with an orifice 11a, and the signal oil passage 7f is provided with an orifice 11b.

  One pressure sensor 10 that detects the discharge pump pressure Pp and inputs it to the controller 13 is provided, and the discharge pump pressure Pp of the hydraulic pumps 3 and 4 is guided to the pressure sensor 10 via signal oil passages 3b and 3c, respectively. It has been. The signal oil passage 3b is provided with an orifice 9a, and the signal oil passage 3c is provided with an orifice 9b.

  The controller 13 is also connected to an accelerator dial 15 and a mode setter 16 that constitutes switching means for switching the governor characteristics of the engine 1 so as to be selectable.

  With respect to the controller 13, the arithmetic circuit will be described first with reference to FIG. FIG. 2 shows a calculation circuit for a command signal to the engine controller 1a, and a calculation circuit for a signal to the electromagnetic proportional valve 8 that controls the swash plate controllers 3a and 4a is omitted.

  The controller 13 outputs a pump capacity table S1 that outputs a pump capacity based on a negative control pressure signal from the pressure sensor 12, a maximum torque setting table S2 that sets a maximum torque based on a signal from the accelerator dial 15, and an output from the pump capacity table S1. And a multiplier S3 for obtaining a pump torque estimated value by multiplying the signal of the discharge pump pressure of the pressure sensor 10, and a minimum value selector S4 for selecting the minimum value of the output of the multiplier S3 and the output of the maximum torque setting table S2. I have.

  The controller 13 also outputs an engine speed correction value table S5 that outputs a correction value of the engine speed setting according to a signal from the pressure sensor 12, and the mode setting device 16 described above as a switching means for selectively switching the governor characteristics of the engine 1. And a switch S6 for switching the coefficients S7a (+1), S7b (0), S7c (-1) according to the signal, and a multiplier S8 for multiplying the output of the switch S6 and the output of the engine speed correction value table S5. ing.

  The controller 13 further outputs an engine speed setting device S9 that outputs the engine speed setting based on the accelerator dial 15, and adds the engine speed correction value output from the multiplier S8 to the output of the engine speed setting device S9. The control calculation such as PID is performed based on the output of the subtractor S11 and the subtractor S11 for obtaining the rotational speed deviation between the engine set speed set by the adder S10 and the adder S10 and the engine speed detected by the engine speed sensor 14. The controller S12 to perform, the gain setter S13 of the output of the minimum value selector S4, and the adder S14 that adds the output of the controller S12 and the output of the gain setter S13 and outputs a command signal to the engine controller 1a. It has.

  Next, the operation of the controller 13 will be described with reference to FIG. 3 together with FIG.

(1) Based on the signal from the pressure sensor 12 of the negative control pressure, the pump capacity is estimated by the pump capacity table S1.
(2) The maximum torque is set in the maximum torque setting table S2 by the signal from the accelerator dial 15.
(3) The multiplier S3 multiplies the discharge pump pressure of the pressure sensor 10 and the pump capacity output from the pump capacity table S1 to obtain an estimated pump torque value.
(4) The minimum value selector S4 selects the minimum value of the output of the multiplier S3 and the output of the maximum torque setting table S2.

(5) A correction value for the engine speed setting is obtained from the negative control pressure of the pressure sensor 12 in the engine speed correction value table S5.
(6) The coefficient S7a (+1), S7b (0) or S7c (-1) is selected by the mode setter 16 and the switch S6, the output of the switch S6 and the engine speed correction value table S5 in the multiplier S8. Multiply the output. As shown in FIG. 3, when the coefficient is S7b (0), the engine speed is constant and the isochronous control is indicated (indicated by a one-dot chain line), and when the coefficient is S7a (+1), plus-loop control is performed. When the coefficient is S7c (-1), minus droop control (shown by a dotted line) is performed.

(7) Based on the signal from the accelerator dial 15, the engine speed setter S9 outputs the engine set speed, and the adder S10 outputs the engine speed setter S9 to the output from the multiplier S8. Add the values.
(8) The subtractor S11 obtains a rotational speed deviation between the engine speed set by the adder S10 and the engine speed detected by the engine speed sensor 14.
(9) The controller S12 performs a control operation such as PID based on the output of the subtracter S11.
(10) On the other hand, the gain setter S13 multiplies the estimated pump torque value output from the minimum value selector S4 by the gain and adds the gain to the output of the controller S12 by the adder S14, and sends a command signal to the engine controller 1a. Output as.

  The effect of the engine control apparatus 20 of the hydraulic working machine as described above will be described.

  The engine controller 20 controls the engine 13 to output a command signal based on the engine set speed corrected by the engine load estimated in advance from the discharge pump pressure Pp and the negative control pressure Pn by the controller 13 that outputs a command signal to the engine controller 1a. To the device 1a.

  Therefore, compared to the conventional speed sensing control that feeds back the actual engine speed to the control system and controls the engine, a feedforward signal based on the engine speed is output to the engine controller based on the estimated engine load. Therefore, the response to the load fluctuation of the engine speed can be accelerated, the change in the engine speed can be reduced, and the fuel consumption can be improved.

  In addition, a mode setting unit 16 and a switching unit S6 are provided as switching means for switching the governor characteristics of the engine 1 so as to be selectable. The controller 13 further corrects the engine set speed based on the selected governor characteristics. Therefore, an operation mode corresponding to the work can be selected, and fuel consumption can be improved.

  Further, the hydraulic working machine includes a plurality of hydraulic pumps 3 and 4 driven by the engine 1, and one pressure sensor 10 and a negative control pressure Pn to which discharge pump pressures Pp of the plurality of hydraulic pumps 3 and 4 are guided. One pressure sensor 12 is provided, and each of the pressure sensors 10 and 12 is provided with orifices 9a, 9b, 11a, and 11b in signal oil passages 3b, 3c, 7e, and 7f that respectively lead the discharge pump pressure Pp or the negative control pressure Pn. ing.

  Therefore, since the discharge pump pressure Pp and the negative control pressure Pn are detected via the orifices 9a, 9b, 11a, and 11b provided in the signal oil passages 3b, 3c, 7e, and 7f, the average of hydraulic working machines with large load fluctuations is averaged. The pressure can be detected. In addition, the number of pressure sensors can be reduced, and the system can be simplified.

The control circuit diagram of the engine control apparatus of the hydraulic working machine comprised according to this invention. FIG. 2 is an arithmetic circuit diagram of the controller shown in FIG. 1. The engine governor characteristic diagram selected by the mode setting device.

Explanation of symbols

1: Engine 1a: Engine controller 3, 4: Hydraulic pump 3b, 3c: Signal oil path 6: Switch (switching means)
7e, 7f: Signal oil passages 9a, 9b: Orifice 10: Pressure sensor 11a for detecting discharge pump pressure, 11b: Orifice 12: Pressure sensor 16 for detecting negative control pressure 16: Mode setting device (switching means)
20: Engine control device

Claims (3)

A controller that outputs a command signal to the engine controller of the hydraulic working machine;
A pressure sensor for detecting a discharge pump pressure of a hydraulic pump driven by an engine controlled by the engine controller;
A pressure sensor for detecting the negative control pressure of the circuit through which the discharge oil of the hydraulic pump flows,
The controller
An engine control device for a hydraulic working machine, wherein a command signal based on an engine set speed corrected by an engine load estimated from the discharge pump pressure and the negative control pressure is output to an engine controller. Switching means for switching the governor characteristics of the engine so as to be selectable;
The controller further includes:
The engine control device for a hydraulic working machine according to claim 1, wherein the engine set rotational speed is corrected based on the selected governor characteristic. A hydraulic working machine comprising a plurality of hydraulic pumps driven by the engine;
One pressure sensor from which the discharge pump pressure of a plurality of hydraulic pumps is led and one pressure sensor from which the negative control pressure is led,
The engine control device for a hydraulic working machine according to claim 1 or 2, wherein each of the pressure sensors is provided with an orifice in each of the signal oil passages for guiding the discharge pump pressure or the negative control pressure.

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