JP2008082303A - Engine control device for construction machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To certainly prevent engine stalling caused by a sudden increase in load torque during idle operation at a low temperature. <P>SOLUTION: This control device for a construction machine driving a hydraulic pump 5 by an engine 1 and controlling the engine speed of the engine 1 by a controller 4, is provided with an oil temperature sensor 15 detecting a temperature of hydraulic fluid for the hydraulic pump 5, and an engine controller 2 increasing the idle engine speed of the engine by an engine speed increasing command signal from the controller 4. In a low temperature that a value detected by the oil temperature sensor 15 is lower than a predetermined temperature, the engine speed increasing command signal is output from the controller 4 to the engine controller 2, thereby increasing the idle engine speed of the engine 1 up to a desired value to increase the output torque of the engine 1. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an engine control device for a construction machine, and more particularly to an engine control device for a construction machine that prevents engine stall when the hydraulic oil temperature of a hydraulic pump is low.

  Conventionally, an engine control device of this kind of construction machine is equipped with a hydraulic pump driven by an engine, operates various hydraulic actuators for working and traveling by the hydraulic pressure of the hydraulic pump, and controls the rotational speed of the engine. It is configured to be controlled by a controller.

  In general, in the idling operation of the engine, the idling speed is reduced as much as possible from the viewpoint of energy saving, low noise, and low vibration. However, when the temperature of the hydraulic oil of the hydraulic pump is low, the viscosity of the hydraulic oil increases, and accordingly, the load torque of the hydraulic pump also increases. As a result, the engine output torque may be insufficient with respect to the load torque of the hydraulic pump, causing engine down (hereinafter referred to as engine stall).

In order to prevent the engine stall, means for driving the governor lever to an operating position where the engine can be started when the engine is started, and after the engine is started by the governor lever, the engine There is one provided with means for controlling the rotation speed via the governor lever (see, for example, Patent Document 1).
JP-A-9-88674.

  The prior art described above can prevent engine stall by driving the governor lever to an operating position where the engine can be started during idle operation. However, since the engine speed is controlled after starting operation without considering the temperature of the hydraulic oil of the hydraulic pump, there has been a problem that idle operation cannot be performed at an optimum engine speed corresponding to the temperature.

  Therefore, there is a technical problem to be solved in order to prevent engine stall due to an increase in load torque during low temperature operation and to perform idle operation at an optimal engine speed. It aims at solving this subject.

  The present invention has been proposed to achieve the above object, and the present invention relates to a construction machine configured to drive a hydraulic pump by an engine and to control the rotational speed of the engine by a controller. In the engine control device, an oil temperature sensor that detects a temperature of the hydraulic oil of the hydraulic pump, and an engine controller that increases the idle rotation speed of the engine by a rotation speed increase command signal of the controller are provided, and the oil temperature sensor A construction machine configured to increase idle speed to a required value and perform idle operation by outputting a speed increase command signal from the controller to the engine controller when a detected value is lower than a predetermined temperature. An engine control device is provided.

According to this configuration, in the idle operation, the temperature of the hydraulic oil of the hydraulic pump is detected by the oil temperature sensor, and the detected value is transmitted to the controller. When the detected value is lower than the predetermined temperature, the controller outputs an engine speed increase command signal to the engine controller to increase the idle engine speed to a required engine speed higher than the normal temperature. Idle operation.

  According to the first aspect of the present invention, the engine output torque increases to a required value or higher by operating the engine at a low temperature by raising the idle speed to a required value as compared with the normal temperature. It is possible to prevent an engine stall due to a sudden rise. Further, since the engine speed is increased in consideration of the temperature of the hydraulic oil of the hydraulic pump, stable idling operation is possible.

  The object of the present invention is to prevent engine stall due to an increase in load torque of the hydraulic pump during low temperature starting, and is configured to drive the hydraulic pump by the engine and to control the rotational speed of the engine by the controller. In the engine control device for a construction machine, an oil temperature sensor that detects a temperature of hydraulic oil of the hydraulic pump, and an engine controller that increases an idle rotation speed of the engine by a rotation speed increase command signal of the controller are provided. This is achieved by outputting an engine speed increase command signal from the controller to the engine controller when the detected value of the temperature sensor is lower than a predetermined temperature to increase the idle engine speed to a required value to perform idle operation. .

  A preferred embodiment of the present invention will be described below with reference to FIGS. In addition, although a present Example is applied to the hydraulic excavator which comprises an arm, a boom, a bucket, etc. as a construction machine, it should not be limited to a hydraulic excavator.

  FIG. 1 is a hydraulic circuit diagram illustrating an engine control device for a construction machine according to the present embodiment. In the figure, reference numeral 1 denotes an engine mounted on a hydraulic excavator, for example, a diesel engine. The engine 1 is provided with an engine controller 2 that arbitrarily adjusts the rotational speed operating position of the governor. The engine 1 is provided with a rotation speed sensor 3 for detecting the engine rotation speed. The rotation speed sensor 3 and the engine controller 2 are connected to an input section of a controller (microcomputer) 4 that controls the overall operation of the hydraulic excavator.

  Accordingly, when the rotational speed command signal is output from the controller 4 to the engine controller 2, the rotational speed of the engine 1 increases to a predetermined required value. Further, the controller 4 includes a storage unit 4a, and the storage unit 4a stores detection values of the rotation speed sensor 3 and an oil temperature sensor (described later) 15.

  A (main) hydraulic pump 5 is drivably connected to the output shaft of the engine 1, and the discharge amount of the hydraulic pump 5 is adjusted by a regulator (not shown). Further, control valves 7, 8, 9 for hydraulic actuators are disposed in the oil passage 6 on the downstream side of the hydraulic pump 5. These control valves 7, 8, and 9 are connected in series in this order. Further, various hydraulic actuators (not shown) such as boom cylinders, arm cylinders and bucket cylinders are connected to the control valves 7, 8 and 9, respectively. Reference numeral 10 denotes an oil tank connected to the downstream side of the control valve 9 via a throttle 11.

  A branch oil passage 12 is connected to the oil passage 6 between the hydraulic pump 5 and the control valve 7, and a relief valve 13 for setting the discharge pressure of the hydraulic pump 5 to a high pressure or a low pressure is connected to the branch oil passage 12. Has been. Further, an electromagnetic switching valve 14 is connected to the relief valve 13, and the electromagnetic switching valve 14 is connected to the output portion of the controller 4. The electromagnetic switching valve 14 switches and controls the set pressure of the relief valve 13 to a high pressure based on a boost command signal from the controller 4 at room temperature.

  An oil temperature sensor 15 for detecting the temperature of hydraulic oil discharged from the hydraulic pump 5 is installed in the oil passage 6 on the discharge side of the hydraulic pump 5, and the oil temperature sensor 15 is connected to an input portion of the controller 4. ing. The controller 4 switches and controls the operation of the engine controller 2 based on the detection result of the oil temperature sensor 15.

  That is, when the detected value of the oil temperature sensor 15 is equal to or less than a certain value, a rotation speed increase command signal is output to the engine controller 2 in order to increase the idle rotation speed of the engine 1 to a predetermined value (R + ΔR) set in advance. Conversely, when the detection value of the oil temperature sensor 15 exceeds a certain value, the engine speed increase command signal is not output to the engine controller 2.

  Next, the operation of the engine control device will be described with reference to FIG. When performing an idle operation of the engine 1 (step S1), first, the temperature of the hydraulic oil of the hydraulic pump 5 is detected by the oil temperature sensor 15, and the detected value is transmitted to the controller 5. Then, it is determined by the controller 5 whether or not the detected value of the oil temperature sensor 15 is higher than a predetermined temperature (step S2). As a result, when the detected value is in a normal temperature state exceeding a predetermined temperature, the controller 5 does not output the engine speed increase command signal to the engine controller 2, and therefore the idle speed of the engine 1 does not increase (steps S3 and S4). .

  On the other hand, when the detected value of the oil temperature sensor 15 is in a low temperature state lower than the predetermined temperature, the controller 4 outputs a rotation speed increase command signal to the engine controller 2 (step S5). Therefore, the idle speed of the engine 1 is increased by a set value ΔR (for example, about 100 rpm) as compared with the normal temperature, and the output torque of the engine 1 is increased to a required value (step S6).

  Therefore, in the idling operation at low temperature, even when the viscosity of the hydraulic oil is high, the output torque of the engine 1 is always larger than the load torque of the hydraulic pump 5, so that the output torque of the engine 1 as in the conventional case is insufficient. The occurrence of engine stall is reliably prevented.

  In addition, the present invention increases the engine speed in relation to the temperature of the hydraulic oil of the hydraulic pump, so that the idle operation can be operated at the optimum engine speed corresponding to the temperature, and the stable idle operation can always be performed. Become.

  The present invention can be variously modified without departing from the spirit of the present invention, and the present invention naturally extends to the modified one.

The hydraulic circuit diagram of the engine control apparatus of a construction machine which shows one Example of this invention. The flowchart explaining operation | movement of the engine control apparatus of the construction machine which concerns on one Example.

Explanation of symbols

1 Engine 2 Engine controller 3 Speed sensor 4 Controller (control means)
4a Storage unit 5 Hydraulic pump 13 Relief valve 14 Electromagnetic switching valve 15 Oil temperature sensor

Claims (1)

In an engine control device for a construction machine configured to drive a hydraulic pump by an engine and to control the rotational speed of the engine by a controller,
An oil temperature sensor that detects the temperature of the hydraulic oil of the hydraulic pump, and an engine controller that increases the idle rotation speed of the engine by a rotation speed increase command signal of the controller,
When the detected value of the oil temperature sensor is lower than a predetermined temperature, the controller outputs an engine speed increase command signal to the engine controller to increase the engine speed to a set value and perform idle operation. An engine control device for a construction machine.

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