JPH04143428A - Controller for construction machinery - Google Patents

Abstract

PURPOSE:To abate any overspeed in various apparatus including an engine overrun or the like by resetting the desired rotational frequency of an engine at a time when a running control lever is operated and pressure in a hydraulic pump has become less than the setting value. CONSTITUTION:Discharge pressure oil in a hydraulic pump 1 being driven by an engine 2 is fed to a running hydraulic motor 4 according to operation of a running control lever 5a, driving this motor. In addition, a fuel injection quantity of the engine 2 is controlled so as to make speed of the engine 2 come to the desired engine speed set by a throttle value setter 15. Here a controller 7 resets the desired speed of the engine 2 to be lower than the desired engine speed set by the throttle value setter 15 according to a drop of detected pressure when a fact that the running control lever 5a is operated is detected by a pressure switch 6 as well as when detecting pressure of a hydraulic sensor 10 has become less than the setting pressure. With this constitution, any possible overspeed in various apparatuses including an overrun of the engine 2 and so on is thus obviable.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a control device for construction machinery such as a power shovel, and in particular, to prevent engine overrun and associated over-speed of hydraulic pumps, travel actuators, etc. Concerning a control device that can prevent.

[Conventional technology]

In construction machines such as power shovels, the target engine speed is set by a speed setting device such as a throttle dial. The predetermined controller drives and controls the fuel control lever of the governor using an actuator such as a motor so that the engine speed reaches the set target speed.

In addition, construction machinery is equipped with a power mode selection switch that selects the target engine speed and target output torque depending on the work mode. The target rotation speed can be set.

Furthermore, in a construction machine, a hydraulic pump is driven by an engine, and pressure oil discharged from the hydraulic pump is supplied to a travel actuator, that is, a travel motor, for example, in response to operation of a travel control lever. This drives the travel motor and causes the construction machine to travel.

[Problem to be solved by the invention]

The rotation speed setting device is normally set at the maximum position so that the engine is operated at maximum output. Also, the power mode selection switch is often operated to select the engine or operate at maximum output. At this time, the engine will be operated on the maximum regulation line on the engine performance curve. When the construction machine runs down a slope in such a state, the load on the travel motor, hydraulic pump, and engine is reduced, and the engine is operated at a lower position on the maximum regulation line, that is, with less torque. This causes the engine to rotate above its rated speed, resulting in an overrun (
(engine overspeed). Accordingly, the hydraulic pump, travel motor, etc. are also operated at a speed exceeding their allowable rotation speed. This leads to a decrease in the durability, etc. of the hydraulic equipment, that is, a decrease in reliability. Furthermore, due to overrun, the traveling speed at the time of dismounting becomes higher than the rated traveling speed of the construction machine, resulting in a dangerous situation.

The present invention was made in view of these circumstances, and prevents over-speeding of various equipment such as engine overrun when the load on the hydraulic pump is small, such as when construction machinery is dismounting. The purpose is to provide a control device for construction machinery that is highly reliable and can be operated safely.

[Means to solve the problem]

Therefore, the present invention supplies pressure oil discharged from a hydraulic pump driven by an engine to a travel actuator in accordance with the operation of a travel control lever, thereby driving the travel actuator and increasing the rotational speed of the engine. In a control device for a construction machine that controls a fuel injection amount of the engine so as to reach a target rotation speed set by a rotation speed setting device, operation detection detects that the travel operation lever is operated. means, a pressure detection means for detecting the pressure of discharge pressure oil of the hydraulic pump, and the operation detection means detects that the travel operation lever is operated, and the detection pressure of the pressure detection means is set. The target rotation speed of the engine is set lower than the target rotation speed set by the rotation speed setting device in response to the decrease in the detected pressure so that the rotation speed of the engine becomes the rated rotation speed when the pressure becomes lower than the pressure. and means for controlling the fuel injection amount of the engine so as to achieve the reset target rotation speed.

[Effect]

According to this configuration, the operation detection means detects that the driving operation lever is being operated, that is, that the construction machine is currently in a traveling state.

On the other hand, the pressure of the discharge pressure oil of the hydraulic pump is detected by the pressure detection means.
In other words, the magnitude of the load applied to the hydraulic pump is detected.

When it is detected by each of these detection means that the construction machine is running and the load on the hydraulic pump is below a predetermined value, the engine rotation speed may be set to There is a possibility that this will happen. Here, the overrun amount of the engine rotation speed changes depending on the detected pressure of the discharge pressure oil of the hydraulic pump, that is, the magnitude of the load applied to the hydraulic pump (the smaller the load, the larger the overrun amount). Therefore, control is performed to lower the engine speed by the amount of overrun to bring it to the rated speed.

That is, the target rotation speed of the engine is reset to be lower than the target rotation speed set by the rotation speed setting device in accordance with a decrease in the detected pressure of the discharge pressure oil of the hydraulic pump. Then, when the fuel injection amount of the engine is controlled to reach the reset target rotation speed, the engine is operated at the rated rotation speed and overrun is prevented.

〔Example〕

Embodiments of a control device for construction machinery according to the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the device applied to a power shovel.

In the figure, a variable displacement hydraulic pump 1 is driven by an engine 2, and the discharge flow rate per rotation is changed by changing the tilt angle of a swash plate 1a. Pressure oil discharged from the hydraulic pump 1 is supplied to a traveling hydraulic motor 4 via a traveling operation valve 3, and drives the hydraulic motor 4. The PPC valve 5 supplies pilot pressure oil to the pilot ports 3a, 3 of the operating valve 3 in accordance with the operation of the travel operating lever 5a.
b. In other words, the driving operation lever 5
When a is operated from a neutral state in a predetermined direction, pilot pressure oil with a pressure corresponding to the amount of operation is applied to the pilot port 3a or 3b depending on the direction of operation, and the operation valve 3 is moved in accordance with the direction of operation. the direction and by the amount of movement corresponding to the above-mentioned operation amount. As a result, the operating valve 3 supplies pressure oil from the hydraulic pump 1 to the traveling motor 4 at a flow rate corresponding to the pressure of the applied pilot pressure oil, thereby driving the hydraulic motor 4 in forward and reverse rotation. The PPC valve 5 is provided with a pressure switch 6 that detects the amount of operation of the operating lever 5a by detecting the pilot pressure of the PPC valve 5. This pressure switch 6 is turned on when the amount of operation of the operating lever 5a exceeds a predetermined value. Here, this predetermined value is set as a threshold value for determining whether the hydraulic motor 4 is being driven and the excavator is running. Note that a limit switch may be used instead of the pressure switch 6. The ON signal generated by pressure switch 6 is applied to controller 7. In addition, in a power excavator, each working machine such as a boom also uses a hydraulic pump 1 in the same way as a traveling hydraulic motor 4.
Although it is driven by a hydraulic cylinder driven by a hydraulic cylinder, illustration thereof is omitted for convenience of explanation.

The TVC valve 8 is provided to keep the absorption torque of the hydraulic pump 1 constant. That is, the valve 8 is connected to the hydraulic pump 1
The tilting angle of the swash plate 1a is controlled via the servo actuator 9 so that the product of this pressure P and the discharge flow rate Q of the hydraulic pump 1, that is, the absorption torque of the hydraulic pump 1, is constant. . A signal indicating the magnitude of absorption torque is applied to the TVC valve 9 from the controller 7, and the swash plate tilt angle is controlled so that this magnitude is obtained. A hydraulic sensor 10 is provided on the discharge side of the hydraulic pump 1 to detect the discharge pressure P of the pump 1, and a detection signal is applied to the controller 7.

The engine 2 is provided with a fuel injection pump 11 and a governor (fuel injection control) 12. A fuel control lever 13 of the governor 12 is driven by a motor 14. The amount of fuel injection by the pump 11 is controlled by the controller 7 controlling the rotation angle θ of the rotation shaft of the motor 14. The throttle amount setter 15 is a fuel dial that sets a target rotation speed of the engine 2, and a signal indicating this set target rotation speed is applied to the controller 7.

The processing performed by the controller 7 will be explained below. In the following, it is assumed that the throttle amount setting device 15 is set at the maximum position.

The controller 7 sets the target rotation speed of the engine 2 in different ways depending on the detection signal of the pressure switch 6 and the detection signal P of the oil pressure sensor 10. That is, the controller 7 determines whether the detection signals of the oil pressure sensor 10 and the pressure switch 6 are in either of the following states (1) and (2).

■The detected value P of the oil pressure sensor 10 is the set value P. The following is
And the detection signal of the pressure switch 6 is on.

■Other than that.

Here is the setting value P. is set as a threshold value at which the running load is small, and if it is less than this, the engine 2 will overrun.

When the above state (■) occurs, for example, the excavator is excavating and the work equipment is being driven, or the excavator is running uphill and there is no difference in whether it is running or not. The load on the hydraulic pump 1 is large and the detected value P is the upper set value P. This is the case when the detected value P is less than or equal to the set value Po because the vehicle is not running and the load on the hydraulic pump 1 is small. At these times, there is no risk of engine 2 overrunning. Therefore, at this time, the set value of the throttle amount setter 15 is set as the target rotation speed of the engine 2. That is, as shown in the engine performance curve diagram of FIG. 2, the maximum target rotation speed N set by the throttle amount setting device 15.

The actuator 14 is driven to control the fuel injection amount so that the amount of fuel injection is obtained. Then, the maximum speed regulation line 1. The output torque T of the engine 2 at the maximum torque point B above. and the absorption torque T of the hydraulic pump 1. will be matched. The engine speed at this time is the rated speed N. It can be seen that there is no overrun.

On the other hand, when the power excavator is traveling downhill, the operating lever 5a is operated and an on signal is manually input from the pressure switch 6. In addition to this, the load applied to the hydraulic pump 1 is smaller and the detected value P is the set value P. It is as follows. Therefore, assume the state shown in ■ above.

Now, assuming that the fuel injection amount is controlled so as to obtain the maximum target rotation speed N1 set by the throttle amount setting device 15 in this state, A on the maximum speed regulation line 11
At the point, the engine torque TL and the absorption torque TL of the hydraulic pump 1 are matched, and the engine 2 reaches the rotational speed N E
This results in an overrun of No. Therefore, at this time, regardless of the set rotation speed N1 of the throttle amount setter 15, the target rotation speed is reset to a low value N2, matching is performed at the 0 point on the regulation line 12, and the engine 2 is set to the rated rotation speed N. Make sure to rotate it. The engine torque TL is a running load, and means the discharge pressure P of the hydraulic pump 1, which is the running drive hydraulic pressure. Therefore, it can be seen that the set target rotation speed N2 can be obtained by reducing the set rotation speed N by the rotation speed determined as described later in accordance with the decrease in the discharge pressure P of the hydraulic pump 1. The rotational speed reduction amount is determined as follows.

The contents of the engine torque curve shown in FIG. 2, that is, the rated rotation speed N, are stored in advance in the controller 7. , rated torque T. ,
The maximum engine speed N on the torque curve, the maximum capacity DM of the hydraulic pump 1, the torque efficiency η of the hydraulic pump 1,
is entered and stored.

The absorption torque TL of the hydraulic pump 1 can be determined by the following equation (1) based on the discharge pressure P detected by the oil pressure sensor 10.

TL - (PXDM /200π) (1/η,)...
(1) On the other hand, the engine rotation speed NE is the rotation speed on the maximum speed regulation line 11, that is, the rated rotation speed N. and the maximum engine speed N, the engine torque T at the engine speed NE can be determined by an equation that is inversely proportional to the engine speed N, as shown below.

T= iTo/(N+No)) (
NE No )+To...(2) This equation (2) is the overrun amount N. Solving for −No, NE No = f (N+ No
) / To l (T.

T) ... (3) is obtained. Here, the engine torque T of this equation (3)
is equal to the absorption torque T of pump 1 in equation (1) above, so T and TL can be eliminated, and the overrun amount N, -N, is Nl! No-((NM No)/To)
(T.

(PXDM/200π)(1/η+)l (4). Therefore, from this equation (4), it is clear that the overrun amount N, -N is unique from the pump discharge pressure P.

It turns out that you can find . Overrun amount N,
It can be seen that -No becomes larger as the discharge pressure P becomes smaller. Since the regulation angle of the engine 2 is constant regardless of the drive position of the governor 12, this overrun amount N, -N0 becomes the amount of reduction from the set target rotation speed N.

That is, as shown in FIG. 3, the relationship between the control angle θ of the motor 14 that drives the governor 12 and the engine rotation speed N under no load is stored in a memory (not shown) of the controller 7. Therefore, if the overrun amount N, !, -No is found based on the discharge pressure P of the hydraulic pump 1 from the above (4-inch type), then from the above memory, the overrun amount N, -N is calculated from the engine rotation speed N.

The control angle θ2 of the motor 14 corresponding to the decreased rotation speed N2 is determined, and the control angle θ2 of the motor 14 is determined so that this angle θ2 is obtained.
What is necessary is to drive and control the angle θ of 4.

As a result, the motor 14 is driven so as to obtain the target rotation speed N2 which has been reset to be lower by an overrun amount NE-N than the maximum target rotation speed N1 set by the throttle amount setter 15, and the engine 2 is activated. Rated rotation N. Rotate with. This allows the vehicle to always travel below the rated speed when exiting the vehicle.

In the embodiment, a power shovel is assumed as the construction machine, but any construction machine can be used.

〔Effect of the invention〕

As explained above, according to the present invention, engine overrun is prevented, so the durability of the engine and the hydraulic equipment driven by it is improved, the reliability of the equipment is improved, and the construction machinery is constantly operated. The vehicle is driven at a speed below the rated speed, improving safety.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an embodiment of the control device for construction machinery according to the present invention, and FIG. 2 is a graph showing the performance curve of the engine shown in FIG. The graph used for explanation, FIG. 3, which is said to be stored in the controller shown in FIG. 1, is a graph showing the relationship between the rotation angle of the motor that drives the banner and the rotation speed of the engine. DESCRIPTION OF SYMBOLS 1... Hydraulic pump, 2... Engine, 3... Traveling operation valve, 4... Traveling hydraulic motor, 5a... Traveling operating lever 6... Pressure switch, 7... Controller, 10...Oil pressure sensor, 11...Fuel injection pump, 12...Governor, 15...-Throttle amount setting device. , Ding, +1. 'L Fig. 2 Avana the same female fII device Fig. 3

Claims (1)

[Scope of Claims] Pressure oil discharged from a hydraulic pump driven by an engine is supplied to a travel actuator in accordance with the operation of a travel control lever to drive the travel actuator and to increase the rotational speed of the engine. In a control device for construction machinery that controls the fuel injection amount of the engine so as to reach a target rotation speed set by a rotation speed setting device, operation detection detects that the travel operation lever is operated. means, a pressure detection means for detecting the pressure of the discharge pressure oil of the hydraulic pump, and the operation detection means detects that the traveling operation lever is operated, and the detection pressure of the pressure detection means is set. The target rotation speed of the engine is set lower than the target rotation speed set by the rotation speed setting device according to the decrease in the detected pressure so that the rotation speed of the engine becomes the rated rotation speed when the pressure becomes lower than the pressure. A control device for a construction machine, comprising: means for controlling a fuel injection amount of the engine so as to achieve the reset target rotation speed.