JP2009052519A - Engine control device for working machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce fuel consumption by suppressing racing of an engine when load is eliminated from a heavy load condition in a working machine controlling engine output, based on a plurality of engine speed-output characteristics determined according to different engine target rotation speed. <P>SOLUTION: It is determined whether a load condition of the engine is a lower load condition in relation to operational tool set engine target rotation speed SN set by an accelerator dial value A. When it is determined that it is a lower load condition, reduced control engine target rotation speed LT lower than the operational tool set engine target rotation speed SN is set as engine target rotation speed TN. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention belongs to the technical field of an engine control device in a work machine such as a hydraulic excavator.

Generally, in a working machine such as a hydraulic excavator, the engine speed at no load is set as the engine target speed so that the engine speed (rpm) region to be used can be made different according to the work content. There is one in which the number of revolutions can be arbitrarily set by an operator using a setting operation tool such as an accelerator dial. In this case, the engine is controlled so that the output torque increases as the engine speed decreases as the load increases, based on a plurality of engine speed-output characteristics determined according to the engine target speed. (For example, refer to Patent Document 1).
JP-A-2005-320946

  By the way, for example, in a hydraulic excavator, when excavating and loading work for excavating earth and sand and loading it on a truck is repeated, the work for excavating earth and sand and the work for loading the earth and sand into a truck are high-load work, When the earth and sand are loaded onto the truck, the load suddenly comes off and it becomes a low-load work until excavation is started again. When performing an operation in which the load greatly fluctuates as described above, the operator usually sets the engine target rotational speed high with the setting operation tool such as the access dial described above so that the high-load operation can be efficiently performed. Since the target engine speed set by the operator using the setting operation tool does not change even when the load fluctuates, the engine speed becomes the target engine speed (the engine speed when there is no load) as soon as the load is removed from the high load operation. ) At this time, the engine is in a state of being blown up and consumes a lot of fuel, and there is a problem to be solved by the present invention.

SUMMARY OF THE INVENTION The present invention was created in view of the above circumstances and has been created for the purpose of solving these problems. The invention of claim 1 uses a different engine speed as an engine target speed when no load is applied. A controller that controls engine output based on a plurality of engine speed-output characteristics determined according to the target speed, and a setting operation tool that is operated to set the engine target speed at a plurality of positions. In the engine control device for a working machine provided, load detection means for detecting the load state of the engine is provided, and the controller sets the load state of the engine detected by the load detection means at the position of the setting operation tool. If it is determined that the load is low with respect to the target engine speed, and if it is not low, The engine setting engine target engine speed is set as the engine target engine speed while the engine target engine speed is set lower than the operation tool setting engine target engine speed when it is determined that the engine is in a low load state. An engine control device for a work machine, wherein target engine speed reduction control is performed.
According to the second aspect of the present invention, the load detection means is configured using a speed sensor that detects the engine speed, while the controller determines that the engine speed detected by the speed sensor is in accordance with the position of the setting operation tool. 2. The engine control in the work machine according to claim 1, wherein the engine load state is determined to be a low load state with respect to the operating tool setting engine target rotational speed when the set first threshold value is exceeded. Device.
According to a third aspect of the present invention, in the low load engine target speed reduction control, the engine load state detected by the load detection means is less than the operating tool setting engine target speed in the low load engine target speed reduction control. 3. The engine control device for a work machine according to claim 1, wherein the engine control device is released when it is determined that the engine is in a high load state with respect to the target engine speed for reduction control that is set to be low. .
According to a fourth aspect of the present invention, the work machine includes a hydraulic pump driven by the engine, and the load detection means includes a speed sensor that detects the engine speed and a pressure sensor that detects a discharge pressure of the hydraulic pump. On the other hand, the controller is configured such that the engine speed detected by the speed sensor is equal to or lower than a second threshold value set according to the position of the setting operation tool, and the hydraulic pump discharge detected by the pressure sensor. When the pressure is equal to or higher than a third threshold value set according to the position of the setting operation tool, it is determined that the engine load state is a high load state with respect to the engine target speed for reduction control. An engine control device for a work machine according to claim 3.
According to a fifth aspect of the present invention, the controller performs a specific work determination for determining whether or not the work performed by the work machine is a specific work that is preset as a work that is not suitable for low target engine speed reduction control. 5. The controller according to claim 1, wherein the controller does not execute low-load engine target speed reduction control when it is determined that the specific operation is performed by the specific operation determination unit. It is an engine control apparatus in the working machine as described in any one of these.

According to the first aspect of the present invention, if the load state of the engine becomes a low load state with respect to the operating tool setting engine target speed set at the position of the setting operating tool, the engine target speed at low load is reduced. When the control is executed, the engine target speed is set lower than the operating tool setting engine target speed. As a result, the engine is controlled so as to have an output corresponding to the engine target rotational speed set lower than the operating tool setting engine target rotational speed. Therefore, even if the load fluctuates, the engine target rotational speed is controlled. As in the conventional case where the number does not change, it is possible to reliably eliminate the trouble that the engine blows up when the load is released from the high load state and consumes a lot of fuel unnecessarily. Can greatly contribute to the development.
According to the second aspect of the present invention, it is possible to easily and surely determine that the engine load state is a low load state with respect to the operating tool setting engine target engine speed, and to detect the engine speed. Since it is normally equipped on a work machine for engine control, no new sensor or the like is required, which is advantageous in terms of cost.
According to the invention of claim 3, when it is determined that the engine load state is a high load state with respect to the engine target speed for reduction control, the engine target speed reduction control during low load is released. Thus, the operating tool setting engine target speed is set again as the engine target speed. In this case, the criterion for canceling the low-load engine target speed reduction control is based on the engine target speed for reduction control. Since the engine is in a load state, it is possible to accurately cancel the engine target speed reduction control during low load.
According to the fourth aspect of the present invention, it is possible to easily and reliably determine whether the engine load state is a high load state with respect to the target engine speed for reduction control, and to detect the engine speed. Since the pressure sensor for detecting the discharge pressure of the hydraulic pump is usually provided in the work machine for engine control or pump control, it does not require a new sensor and is advantageous in terms of cost. is there.
According to the fifth aspect of the present invention, when specific work that is not suitable for low load engine target speed reduction control is being performed, such as traveling or lifting magnet work, for example, low target engine speed reduction is performed. Thus, the control is not executed, and thus it is possible to reliably avoid the problem that the low-load engine target speed reduction control is executed during the specific work and the work efficiency is lowered.

Next, embodiments of the present invention will be described with reference to the drawings.
In FIG. 1, reference numeral 1 denotes a hydraulic excavator that is an example of a work machine. The hydraulic excavator 1 includes a crawler-type lower traveling body 2 and an upper revolving body 3 that is rotatably supported above the lower traveling body 2. The revolving unit 3 is composed of various parts such as the working unit 4 mounted on the upper revolving unit 3, and the upper revolving unit 3 is equipped with an engine E and a hydraulic pump P driven by the power of the engine E, and The conventional configuration is such that various hydraulic actuators such as a travel motor, a swing motor, a boom cylinder 5, an arm cylinder 6, and a bucket cylinder 7 are operated using the hydraulic pump P as a pressure oil supply source. In FIG. 1, the bucket 8 is illustrated as an attachment attached to the working unit 4, but various attachments such as a grapple and a lifting magnet (not illustrated) may be mounted instead of the bucket 8.

  The engine E is of an electronic control system in which a governor G for controlling the fuel injection amount is operated based on a control signal from the engine controller 9, but the engine controller 9 is, as shown in the block diagram of FIG. Fuel injection is performed based on an engine target speed TN (rpm) input from a sub-controller 10 described later and a current engine speed N (rpm) input from a speed sensor 11 that detects the speed of the engine E. A control signal is output to the governor G to increase or decrease the amount to control the engine output. In this case, the engine controller 9 outputs a control signal to the governor G so as to follow the engine speed-output characteristic corresponding to the engine target speed TN. The controller of the present invention is constituted by the engine controller 9 and the sub-controller 10.

  The engine speed-output characteristic will be described with reference to FIG. 3. The engine speed-output characteristic indicates the relationship between the engine speed N (rpm) and the output torque (kW), and is no load. The engine speed at that time is defined as an engine target speed TN, and a plurality of engine speeds are determined according to different engine target speeds TN. This engine speed-output characteristic is well-known as a characteristic used for engine control of the hydraulic excavator 1, and therefore detailed description thereof is omitted. In this embodiment, ten engine target rotations of TN1 to TN10 are performed. A number TN is provided, and each characteristic line is determined according to each engine target speed TN1 to TN10.

  On the other hand, as shown in FIG. 2, the sub-controller 10 has a dial value A of the accelerator dial 12, a current engine speed N (rpm) detected by the speed sensor 11, and a discharge line of the hydraulic pump P. The pump discharge pressure PP detected by the pressure sensor 13 disposed in the vehicle and the operation signal of the operation tool 14 for specific work that is operated when performing the specific work to be described later are input. The engine target speed TN is output to the engine controller 9.

  Here, the accelerator dial 12 is a dial operated by the operator to arbitrarily set the engine target speed according to the work content and the like, and in this embodiment, the engine target speeds of the TN1 to TN10. Corresponding to the number TN, 10-step accelerator dial value A of “1” to “10” is provided. The accelerator dial 12 corresponds to the setting operation tool of the present invention, and the accelerator dial value A corresponds to the position of the setting operation tool of the present invention.

  Further, the specific work is a work set in advance as a work that is not suitable for low-load engine target rotational speed reduction control, which will be described later, for example, traveling (even in a low-load state, due to a decrease in engine rotational speed). If the supply flow rate to the travel motor decreases, the travel speed may decrease) and lifting magnet work (even in a low load state), the supply flow rate to the lifting magnet hydraulic motor due to a decrease in engine speed Is reduced), the generated power may be reduced). And when performing these specific work, the specific work operation tool 14 (for example, traveling pedal, lifting magnet switch) is operated, and the specific work operation tool 14 corresponds to the specific work determination means of the present invention. To do.

  Next, the control in the sub-controller 10 will be described with reference to the control block diagram shown in FIG. 4. As described above, the sub-controller 10 has the accelerator dial value A, the engine speed N (rpm), the pump While inputting the discharge pressure PP and the operation signal of the operation tool 14 for specific work, the 1st-4th tables 15-18 are incorporated.

  The first table 15 is a table in which the relationship between the accelerator dial value A and the operating tool setting engine target speed SN is set, and the second table 16 is the relationship between the accelerator dial value A and the first threshold engine speed X. The set table, the third table 17, is a table in which the relationship between the accelerator dial value A and the second threshold engine speed Y is set, and the fourth table 18 is the accelerator dial value A and the third threshold pump discharge pressure Z. Is a table in which the relationship is set.

  Here, the operating tool setting engine target speed SN is an engine target speed set by the dial value A of the accelerator dial 12 operated by the operator, and in the present embodiment, the “1” to “10” 10 stages of operation tool setting engine target speeds SN1 to SN10 are provided corresponding to 10 stages of the accelerator dial value A, and the values of the operation tool settings engine target speeds SN1 to SN10 of each stage are as follows: It is set to be equal to the target engine speed TN1 to TN10 at the same stage (SN1 = TN1,... SN9 = TN9, SN10 = TN10).

  The first threshold engine speed X is a threshold value set to determine whether the load state of the engine E is a low load state with respect to the operation tool setting engine target speed SN. The first threshold engine speed X is set according to each accelerator dial value A.

  The second threshold engine speed Y is a threshold set for determining whether or not the load state of the engine E is a high load state with respect to a reduction control engine target speed LN described later. The second threshold engine speed Y is set in accordance with each accelerator dial value A. The second threshold engine speed Y is set smaller than the first threshold engine speed X (Y <X).

  The third threshold pump discharge pressure Z is a threshold value set to determine whether or not the load state of the engine E is a high load state with respect to a reduction control engine target speed LN described later. The third threshold pump discharge pressure Z is set according to each accelerator dial value A.

  Then, the sub-controller 10 uses the first to fourth tables 15 to 18 based on the accelerator dial value A, and sets the operation tool setting engine target rotational speed SN, the first threshold engine rotational speed X, and the second threshold engine rotational speed. The number Y and the third threshold pump discharge pressure Z are obtained. The value of the operating tool setting engine target rotational speed SN obtained from the first table 15 is input to the subtractor 19 and the selector 20.

  The subtracter 19 subtracts the predetermined engine speed ΔN from the operating tool setting engine target engine speed SN, and outputs the reduced value to the selector 20 as a reduction control engine target engine speed LN (LN = SN−ΔN). . The predetermined rotational speed ΔN is a rotational speed that is set in advance to reduce the engine target rotational speed in a low-load state that will be described later. In the present embodiment, the operation tool setting engine target rotational speeds SN2 to SN10 are set. The predetermined rotational speed ΔN at this time is set to correspond to the rotational speed for one stage of the engine target rotational speed TN. That is, reduction control engine target speeds LN2 to SN10 are calculated corresponding to the respective operation tool setting engine target speeds SN2 to SN10, but the values of the reduction control engine target speeds LN2 to SN10 are It is set so as to be equal to the values of the lower target engine speeds TN1 to TN9 (LN2 = TN1,... LN9 = TN8, LN10 = TN9). When the operating tool setting engine target rotational speed SN1 is set, the predetermined rotational speed ΔN = 0, that is, the operating tool setting engine target rotational speed SN1 and the reduction control engine target rotational speed LN1 are set to be equal. (LN1 = SN1).

  Further, the selector 20 selects either the operating tool setting engine target speed SN or the engine target speed LN for reduction control based on an OFF-ON signal input from the second AND gate 21 described later. If the input from the second AND gate 21 is an OFF signal, the operating tool setting engine target speed SN is selected, and if it is an ON signal, the reduction control engine target speed LN is selected. At the same time, the selected one is output to the engine controller 9 as the engine target speed TN. That is, when the OFF signal is input from the second AND gate 21, the operating tool setting engine target speed SN is set as the engine target speed TN, while when the ON signal is input, the reduction control is performed. The engine target speed LN is set as the engine target speed TN.

  On the other hand, the value of the first threshold engine speed X obtained from the second table 16 is input to the first determination unit 23. The first determination unit 23 inputs the engine speed N and the first threshold engine speed X, and whether or not the engine speed N is equal to or greater than the first threshold engine speed X (N ≧ X?). Judging. When the engine speed N is equal to or greater than the first threshold engine speed X (N ≧ X), it is determined that the load state of the engine E is a low load state with respect to the operation tool setting engine target speed SN. Then, S = 1 is output to a flip-flop circuit 24 described later. On the other hand, when the engine speed N is less than the first threshold engine speed X (N <X), it is determined that the load state of the engine E is not a low load state with respect to the operating tool setting engine target speed SN, S = 0 is output to the flip-flop circuit 24.

  Further, the value of the second threshold engine speed Y obtained from the third table 17 is input to the second determination unit 25. The second determination unit 25 inputs the engine speed N and the second threshold engine speed Y, and whether the engine speed N is equal to or lower than the second threshold engine speed Y (N ≦ Y?). Judging. When the engine speed N is equal to or lower than the second threshold engine speed Y (N ≦ Y), an ON signal is output to the first AND gate 26. On the other hand, when the engine speed N is larger than the second threshold engine speed Y (N> Y), an OFF signal is output to the first AND gate 26.

  Further, the value of the third threshold pump discharge pressure Z obtained by the fourth table 18 is input to the third determination unit 27. The third determination unit 27 inputs the pump discharge pressure PP of the hydraulic pump P and the third threshold pump discharge pressure Z, and the pump discharge pressure PP is equal to or higher than the third threshold pump discharge pressure Z (PP ≧ Z?). Judge whether there is. When the pump discharge pressure PP is equal to or higher than the third threshold pump discharge pressure Z (PP ≧ Z), an ON signal is output to the first AND gate 26. On the other hand, when the pump discharge pressure PP is less than the third threshold pump discharge pressure Z (PP <Z), an OFF signal is output to the first AND gate 26.

  The first AND gate 26 outputs R = 1 when an ON signal is input from both the second determination unit 25 and the third determination unit 27. When the output of R = 1 from the first AND gate 27 continues for a predetermined time T1 (for example, several seconds), the signal of R = 1 is input to the flip-flop circuit 24. That is, the engine speed N is equal to or lower than the second threshold engine speed Y (N ≦ Y), and the pump discharge pressure PP is equal to or higher than the third threshold pump discharge pressure Z (PP ≧ Z). When the time T1 continues, it is determined that the load state of the engine E is a high load state with respect to the target engine speed LN for reduction control, and R = 1 is input to the flip-flop circuit 24. On the other hand, when an OFF signal is input to the first AND gate 26 from at least one of the second determination unit 25 and the third determination unit 27, or the output of R = 1 from the first AND gate 26 is less than the predetermined time T1. In this case, R = 0 is input to the flip-flop circuit 24.

  The flip-flop circuit 24 outputs Q = 1 to the second AND gate 21 when S = 1 and R = 0 are input, while second when S = 0 and R = 1 is input. Q = 0 is output to the AND gate 21. When S = 0 and R = 0, the previous output is held as it is.

  Further, the sub-controller 10 inputs an operation signal of the specific work operation tool 14 to the fourth determination unit 28, and the fourth determination unit 28 determines whether or not the specific work operation tool 14 is not operated. When the fourth determination unit 28 determines that the specific work operation tool 14 is not operated, an ON signal is output, but the output of the ON signal continues for a predetermined time T2 (for example, several seconds). In this case, it is determined that no specific work is performed, and an ON signal is input to the second AND gate 21. On the other hand, when the fourth determination unit 28 determines that the specific work operation tool 14 is being operated, or when the output of the ON signal from the fourth determination unit 28 is less than the predetermined time T2, the specific operation is performed. It is determined that the operation is being performed, and an OFF signal is input to the second AND gate 21.

  The second AND gate 21 outputs an ON signal to the selector 20 when a signal of Q = 1 is input from the flip-flop circuit 24 and an ON signal is input from the fourth determination unit 28. On the other hand, when a signal of Q = 0 is input from the flip-flop circuit 24, or when an OFF signal is input from the fourth determination unit 28, an OFF signal is output to the selector 20. As described above, when an OFF signal is input from the second AND gate 21 to the selector 20, the operating tool setting engine target speed SN is set as the engine target speed TN, while the ON signal is set. When the value is input, the engine target speed LN for reduction control is set as the engine target speed TN.

  That is, when the engine speed N is less than the first threshold engine speed X (N <X), the load state of the engine E is the operating tool setting engine target speed SN set by the dial value A of the accelerator dial 12. However, in this case, the operation tool setting engine target rotational speed SN is set as the engine target rotational speed TN.

  On the other hand, when the engine speed N is equal to or greater than the first threshold engine speed X (N ≧ X), it is determined that the load state of the engine E is a low load state with respect to the operating tool setting engine target speed SN. However, in this case, a reduction control engine target speed LN obtained by subtracting the predetermined speed ΔN from the operating tool setting engine target speed SN is set as the engine target speed TN. As a result, when it is determined that the engine E is in a low load state, a low control engine target rotational speed LN having a rotational speed lower than the operating tool setting engine target rotational speed SN is set as the engine target rotational speed TN. The engine target rotational speed reduction control is executed during loading.

  Further, at the time of the low load engine target speed reduction control, the engine speed N is equal to or lower than the second threshold engine speed Y (N ≦ Y), and the pump discharge pressure PP is equal to or higher than the third threshold pump discharge pressure Z. If (PP ≧ Z) and this state continues for a predetermined time T1, it is determined that the load state of the engine E is a high load state with respect to the engine target rotational speed LN for reduction control. On the other hand, the low engine load target speed reduction control is released, and the operating tool setting engine target speed SN is set as the engine target speed TN.

  When a specific work is being performed, the operation tool setting engine target speed SN is set as the engine target speed TN regardless of the load state of the engine E. That is, the low target engine speed reduction control is not executed during specific work.

  Next, an example of low load engine target speed reduction control and its release control example when the dial value A of the accelerator dial 12 is set to “10” and work other than the specific work is performed will be described with reference to FIG. To do. First, in a high load state such as excavation work, the engine speed N is less than the first threshold engine speed X (N <X). In this state, the sub-controller 10 is set by the accelerator dial 12. The set operation tool setting engine target speed SN10 is set to the engine target speed TN. Since the value of the operating tool setting engine target speed SN10 is the same as the value of the engine target speed TN10, the engine E is controlled to follow the characteristic line of the engine target speed TN10.

  When the load is removed from the high load state and the low load state is reached, the engine speed N increases. When the engine speed N is equal to or greater than the first threshold engine speed X (N ≧ X), the sub-controller 10 Sets the engine target rotational speed LN10 for reduction control obtained by subtracting the predetermined rotational speed ΔN from the operating tool setting engine target rotational speed SN10 to the engine target rotational speed TN. Since the value of the engine target speed LN10 for reduction control is equal to the value of the engine target speed TN9 at a lower stage, the engine E is controlled to follow the characteristic line of the engine target speed TN9, Thus, low target engine speed reduction control is executed.

  Further, the low load state is changed to the high load state again, the engine speed N becomes less than the second threshold engine speed Y (N <Y), and the pump discharge pressure PP is set to the third threshold pump discharge pressure Z. When the above is satisfied (PP ≧ Z), the sub-controller 10 sets the operation tool setting engine target speed SN10 to the engine target speed TN. As a result, the engine E is controlled so as to follow the characteristic line of the engine target speed TN10, and thus the low-load engine target speed reduction control is released.

  In the present embodiment configured as described above, the output of the engine E is controlled based on a plurality of engine speed-output characteristics determined according to different engine target speeds TN. In this case, When it is determined that the load state of the engine E is not a low load state with respect to the operating tool setting engine target rotational speed SN set by the dial value A of the accelerator dial 12, the operating tool setting engine target rotational speed SN is determined. Is set as the engine target speed TN, and when it is determined that the engine is in a low load state, the engine target speed reduction control at the time of low load is executed, and a predetermined speed is determined from the operating tool setting engine target speed SN. The engine target speed LN for reduction control obtained by subtracting the number ΔN is set as the engine target speed TN.

  As a result, for example, when a high-load operation and a low-load operation are repeatedly performed in a hydraulic excavator, the operator sets the engine target speed high with the dial value A of the accelerator dial 12 in order to efficiently perform the high-load operation. If the load state of the engine E becomes a low load state with respect to the operating tool setting engine target rotational speed SN set by the accelerator dial value A, the engine target rotational speed TN becomes the engine control rotational speed LN for reduction control. Will fall to. Then, when the engine target rotational speed TN decreases from the operating tool setting engine target rotational speed SN to the reduction control engine target rotational speed LN, the engine E becomes an output corresponding to the reduction control engine target rotational speed LN. As a result, the target engine speed does not change even when the load fluctuates, and the engine blows up when the load is released from the high load state, as in the conventional case. Therefore, it is possible to reliably eliminate the problem of consuming a lot of fuel unnecessarily, which can greatly contribute to lower fuel consumption. Further, even when the engine target speed TN is set to the maximum value by the accelerator dial value A, that is, the engine target speed TN10 in this embodiment, as described in the control example shown in FIG. In this case, the target engine speed TN decreases to the target engine speed TN9. Therefore, the high engine speed range TN10 (AB portion in FIG. 5) is not used. It can also contribute to noise reduction.

  Further, the engine target speed reduction control at the time of low load is configured to be released when it is determined that the load state of the engine E is a high load state with respect to the engine target speed LN for reduction control. Therefore, when returning from low load work to high load work, the engine target speed TN automatically returns to the operating tool setting engine target speed SN set by the dial value A of the accelerator dial 12, The engine output according to the operating tool setting engine target rotational speed SN is obtained. In this case, the criterion for determining the engine target rotational speed reduction control release at low load is the load state of the engine E with respect to the engine target rotational speed LN for reduction control. Therefore, it is possible to accurately cancel the engine target speed reduction control during low load.

  Further, whether or not the load state of the engine E is a low load state with respect to the operating tool setting engine target rotational speed SN is determined based on whether the engine rotational speed N is set according to the accelerator dial value A. The determination is made based on whether or not the engine speed X is greater than or equal to the threshold engine speed X, and whether or not the load state of the engine E is a high load state with respect to the target engine speed LN for reduction control is determined by: It is determined whether the engine speed N is equal to or less than a second threshold engine speed Y set according to the accelerator dial value A, and the pump discharge pressure PP is set according to the accelerator dial value A. It is configured based on the determination as to whether or not it is equal to or higher than the three threshold pump discharge pressure Z. Thus, the load state of the engine E can be easily and reliably determined, and the engine speed N is detected. Speed Since the pressure sensor 13 and the pressure sensor 13 for detecting the pump discharge pressure PP are normally provided in the hydraulic excavator 1 for engine control and pump control, a new sensor or the like is not required and cost is low. Is also advantageous.

  In addition, work that is not suitable for engine target speed reduction control at low load, such as traveling or lifting magnet work, is set as a specific work in advance, and when the specific work is being performed, Since the engine target speed reduction control is not executed, it is possible to reliably avoid a problem that the engine target speed reduction control during low load is executed during specific work and the work efficiency is lowered.

Of course, the present invention is not limited to the above-described embodiment. For example, in the above-described embodiment, when the operating tool setting engine target rotational speed SN1, the predetermined rotational speed ΔN = 0, that is, the operating tool. The set engine target rotational speed SN1 and the reduction control engine target rotational speed LN1 are set to be equal, and accordingly, when the dial value A of the accelerator dial 12 is “1”, the engine target at low load is set. The engine speed reduction control is not executed. However, in the region where the engine target engine speed TN is low, the above-described phenomenon that the engine blows up hardly occurs, so not only when the accelerator dial value A is “1”. For example, when the load is “1” to “5”, the engine target speed reduction control at low load may not be executed.
In the above embodiment, an electronic control type governor is used. However, the present invention is not limited to this, and it is needless to say that a mechanical (mechanical) governor can be used.

It is a side view of a hydraulic excavator. It is a block diagram which shows the input / output of an engine controller and a sub controller. It is a figure which shows an engine speed-output characteristic. It is a block diagram which shows control of a sub controller. It is a figure which shows the example of control.

Explanation of symbols

9 Engine Controller 10 Sub-controller 11 Speed Sensor 12 Acceleration Dial 13 Pressure Sensor 14 Specified Operation Control Tool A Acceleration Dial Value E Engine P Hydraulic Pump

Claims (5)

A controller for controlling the engine output based on a plurality of engine speed-output characteristics determined according to different engine target speeds, with the engine speed at no load being set as the engine target speed;
In an engine control device for a work machine comprising a setting operation tool operated to set the target engine speed at a plurality of positions.
While providing a load detection means for detecting the load state of the engine,
The controller is
It is determined whether or not the engine load state detected by the load detecting means is a low load state with respect to the operating tool setting engine target speed set at the position of the setting operating tool. If it is determined, the operating tool setting engine target speed is set as the engine target speed, while if it is determined that the engine is in a low load state, the engine target speed is set lower than the operating tool setting engine target speed. An engine control device for a work machine, wherein the engine target speed reduction control is performed at a low load to be set.   The load detecting means is configured using a speed sensor that detects the engine speed, while the controller is configured such that the engine speed detected by the speed sensor is greater than or equal to a first threshold value set according to the position of the setting operation tool. In this case, it is determined that the engine load state is a low load state with respect to the operating tool setting engine target rotational speed.   Low target engine speed reduction control is a reduction control in which the engine load state detected by the load detecting means is set lower than the operating tool setting engine target speed in the low load engine target speed reduction control. 3. The engine control device for a work machine according to claim 1, wherein the engine control device is released when it is determined that the engine target rotational speed is in a high load state.   The work machine includes a hydraulic pump driven by the engine, and the load detection unit is configured using a speed sensor that detects the engine speed and a pressure sensor that detects a discharge pressure of the hydraulic pump, The controller is configured such that the engine speed detected by the speed sensor is equal to or lower than a second threshold value set according to the position of the setting operation tool, and the discharge pressure of the hydraulic pump detected by the pressure sensor is 4. The operation according to claim 3, wherein when the engine is not less than a third threshold value set in accordance with the position, the engine load state is determined to be a high load state with respect to the target engine speed for reduction control. Engine control device in the machine.   The controller is connected to a specific work determination means for determining whether the work performed by the work machine is a specific work set in advance as a work not suitable for low target engine speed reduction control. The engine target speed reduction control during low load is not executed when it is determined that the specific work is being performed by the specific work determination means. Engine control device in a working machine.

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