JP5190408B2 - Engine control device for construction machinery - Google Patents

Description

  The present invention relates to an engine control device in a construction machine that performs engine drive control based on a set target engine speed, and more particularly to an engine control device in a construction machine that improves engine fuel consumption. It is.

  In the working vehicle, when the engine load is equal to or lower than the rated torque of the engine, matching with the engine torque is performed in the high-speed control region in the torque diagram. For example, the target engine speed of the engine is set corresponding to the setting with the fuel dial, and the high-speed control area corresponding to the set target engine speed is determined.

  Alternatively, an area for high speed control is determined corresponding to the setting with the fuel dial, and a target engine speed is set corresponding to the determined area for high speed control. Then, control for matching the engine load and the engine torque is performed in a predetermined high-speed control region.

  In general, many workers often set the target engine speed to be the rated engine speed or a rotational speed in the vicinity thereof in order to increase the amount of work. By the way, the region where the fuel consumption of the engine is small, that is, the region where the fuel consumption is good, is usually present in the medium speed revolution region or the high torque region on the engine torque diagram. For this reason, the high-speed control region determined between the no-load high idle rotation and the rated rotation is not an efficient region from the viewpoint of fuel consumption.

  Conventionally, in order to drive an engine in a fuel-efficient region, a target engine speed value and an engine target output torque value are set in advance in association with each work mode so that a plurality of work modes can be selected. Such a control device is known (for example, see Patent Document 1). In this type of control device, for example, when the operator selects the second work mode, the engine speed can be set lower than in the first work mode, and fuel consumption is improved. be able to.

  However, when the work mode switching method as described above is used, fuel efficiency cannot be improved unless the operator operates the mode switching means one by one. In addition, the engine speed when the second work mode is selected is set to be a value that is uniformly reduced with respect to the engine speed when the first work mode is selected. If the second work mode is selected, the following problem occurs.

  In other words, the maximum speed in the work device of the work vehicle (hereinafter referred to as work machine) is lower than when the first work mode is selected. As a result, the work amount when the second work mode is selected is smaller than the work amount when the first work mode is selected.

  As a means for solving this problem, an engine control device has been proposed (see, for example, Patent Document 2). In the engine control apparatus described in Patent Document 2, when the engine torque is low, the engine is driven based on the second target speed that is lower than the set first target speed of the engine. Control can be performed. Further, when the engine is used in a state where the engine torque is high, the engine is driven so that the target rotational speed is set in advance corresponding to the pump capacity of the variable displacement hydraulic pump driven by the engine or the detected engine torque. Control can be performed.

  As a result, the engine can be used by shifting to a region with good fuel efficiency without substantially changing the work performance of the work vehicle, and the fuel consumption of the engine can be reduced.

Japanese Patent Laid-Open No. 10-273919 International Publication No. WO2008 / 088474

  In the invention described in Patent Document 2, since engine drive control can be performed based on the second target speed that is lower than the set first target speed of the engine, the engine torque is reduced. When the engine is in a low state, the engine can be used by shifting to an area where fuel efficiency is good.

  However, in terms of a very short time when the operation is suspended while performing engine control based on the second target rotational speed, the pump capacity is at the minimum swash plate state. Therefore, it becomes difficult to obtain a state of low torque and high torque. Therefore, although it is a very short time, a situation occurs in which the flow rate discharged from the hydraulic pump is slightly insufficient.

  The invention of the present application further improves the engine control performed based on the second target rotational speed that is lower than the first target rotational speed of the set engine as in the invention described in Patent Document 2. An object of the present invention is to provide an engine control device that can prevent the flow rate discharged from the hydraulic pump from being insufficiently short in a very short time during the transition from the standby state to the non-standby state.

The object of the present invention can be achieved by the invention of the engine control apparatus according to claims 1 to 6.
That is, in the engine control apparatus for the construction machine of the present invention, the variable displacement hydraulic pump driven by the engine, the hydraulic actuator driven by the discharge pressure oil from the hydraulic pump, and the pressure discharged from the hydraulic pump. A control valve for controlling oil to supply and discharge to the hydraulic actuator, command means for selecting and commanding one command value from command values that can be commanded variably, and a command value commanded by the command means First setting means for setting a first target speed of the engine and setting a second target speed that is lower than the first target speed based on the set first target speed. With
An engine control device that performs engine control based on the second target rotational speed,
A standby state detecting means for detecting whether or not the control valve is in a standby state at a neutral position, and a decrease amount of the second target rotational speed when the standby state detecting means detects that the standby state is in the standby state And a means for reducing
When the standby state detecting means detects the standby state, engine control is performed on the basis of the third target rotational speed in which the reduction width is reduced by the reduction width reducing means, and the third target rotation is performed. When performing engine control based on the number, when the standby state detecting means detects that the standby state is not in the standby state, the engine control based on the third target rotational speed is used to determine whether the standby state detecting means is based on the second target rotational speed. Shifting to engine control is the main feature.

  In the engine control device for a construction machine according to the present invention, the standby state detection means detects engine torque, and determines that the standby state is detected when the value is equal to or less than a predetermined value for engine torque set in advance. The main feature is that when the engine torque is larger than a predetermined value, it is determined that the engine is not in the standby state.

  Further, in the engine control apparatus for a construction machine according to the present invention, the standby state detection means detects a pilot pressure for operating the control valve, and if the value is equal to or less than a predetermined value for pilot pressure set in advance, The main feature is that it is determined that the vehicle is in the standby state, and if it is greater than the predetermined value for the pilot pressure, the vehicle is not in the standby state.

  Furthermore, in the engine control apparatus for a construction machine according to the present invention, the standby state detection means detects the pump displacement of the hydraulic pump, and if the value is less than a predetermined value for a preset pump displacement, The main feature is that it is determined as a standby state, and when it is greater than a predetermined value for the pump capacity, it is determined that the state is not the standby state.

  Further, in the engine control device for the construction machine according to the present invention, the standby state detecting means detects the pump discharge pressure from the hydraulic pump, and when the value is equal to or less than a predetermined value for the pump discharge pressure set in advance. The main feature is that it is determined as the standby state, and when it is greater than a predetermined value for the pump discharge pressure, it is determined that the standby state is not satisfied.

Furthermore, in the engine control apparatus for the construction machine according to the present invention, the detected pump displacement of the hydraulic pump and the detected engine torque, and the target at the time of engine control capable of continuously changing the target rotational speed as the engine control. A second setting means for setting a correspondence relationship with the rotational speed, respectively;
In the engine control in which the target rotational speed can be continuously changed, when the engine control is performed based on the third target rotational speed, the detected value of the pump capacity of the hydraulic pump or the detected engine torque The main feature is that the control is performed so that the target rotational speed obtained from the second setting means corresponds to the value.

  In the engine control apparatus according to the present invention, the first target rotational speed of the engine is set according to the command value from the command means, and the second target rotational speed is set to the low rotational speed side based on the set first target rotational speed. Can be set. In a standby state in which the engine control is performed but the operation is interrupted, for example, in a region where the engine torque is equal to or less than a predetermined value set in advance, the engine speed is higher than the second target speed. Engine control can be performed based on the third target rotational speed of a certain engine.

  As a result, in the standby state, the engine speed can be increased to the third target speed that is higher than the second target speed, so the discharge flow rate from the hydraulic pump must be increased. Can do. Thereby, it is possible to secure a flow rate at which the operation is started with respect to the actuator from when the control valve is in the neutral position. And even if it is a very short time to move from the standby state to the non-standby state in which the operation by the actuator is performed, it is possible to prevent the flow rate discharged from the hydraulic pump from being insufficiently small.

  During idle rotation when the control valve is in the neutral position, the fuel consumption is originally low, and even if the engine is rotated at a low speed when the control valve is in the neutral position, the reduction effect on the fuel consumption is not much. There wasn't. Therefore, when the control valve is in the neutral position, the fuel consumption is hardly deteriorated even if the third target speed is set without reducing the engine speed to the second target speed.

  Conversely, when the control valve is in the neutral position, the engine speed can be set to the third target speed without being lowered to the second target speed, so that the discharge flow rate from the variable displacement hydraulic pump can be reduced. You can increase it. For this reason, even immediately after the operation of the operation lever with respect to the control valve is started, the response of the pressure oil flow rate discharged from the variable displacement hydraulic pump corresponding to the operation amount of the operation lever is improved.

  Thereby, it is possible to prevent deterioration of the operability with respect to the actuator without greatly impairing the fuel reduction effect. In addition, when starting work from the standby state, the target engine speed of the engine can be increased to the third target engine speed that is higher than the second target engine speed. It is possible to reduce the flow rate, and it is possible to prevent the flow rate from being insufficient due to the torque limiting condition for preventing engine stall due to the rotation down.

  In the present invention, when the target engine speed is set to the third target engine speed, the engine target engine speed is set to the third target engine speed when the engine enters the non-standby state where the work is performed from the standby state where the work is not performed. The engine control based on the number can be shifted to the engine control based on the second target rotational speed. As a result, it is possible to use the engine in a state where the engine is shifted to a region with good fuel efficiency without substantially changing the work performance in the work vehicle, and the fuel consumption of the engine can be reduced.

  Furthermore, in the present invention, even for engine control in which the second target rotational speed is continuously variable according to the operating position of the operating lever, pump discharge pressure, engine torque, pump capacity, and combinations thereof, It can be suitably applied.

  As described above, various effects brought about by the engine control capable of continuously changing the target rotational speed can be exhibited as they are, together with the effects of the present invention that can be achieved in the standby state.

  The effects brought about by the engine control that can continuously change the target rotational speed include, for example, preventing the engine rotational sound from changing discontinuously, and the uncomfortable feeling caused by the engine rotational sound. Occurrence can be prevented. In the present invention, the target rotational speed can be appropriately changed according to the operation status of the actuator and the load status of the actuator, so that the fuel consumption can be greatly improved.

1 is a hydraulic circuit diagram according to an embodiment of the present invention. (Example) It is a torque diagram of an engine. (Example) It is a torque diagram when increasing an engine output torque. (Example) It is explanatory drawing which shows the rotation down at the time of sudden load. (Example) It is a torque diagram of an engine. (Example) It is a figure which shows the state of the variable displacement hydraulic pump at the time of operation of an operation lever. (Example) It is a torque diagram of another engine. (Example) It is explanatory drawing about the detection of whether it is a standby state. (Example) It is another explanatory drawing about the detection of whether it is a standby state. (Example) It is another explanatory drawing about the detection of whether it is a standby state. (Example) It is another explanatory drawing about the detection of whether it is a standby state. (Example) It is a flowchart which shows the control in a standby state. (Example)

  Preferred embodiments of the present invention will be specifically described below with reference to the accompanying drawings. The engine control device of the present invention can be suitably applied as a control device for controlling a diesel engine mounted on a work vehicle such as a hydraulic excavator, a bulldozer, or a wheel loader.

  In addition to the shape and configuration described below, the shape and configuration of the engine control device of the present invention can be adopted as long as the shape and configuration can solve the problems of the present invention. Is. For this reason, this invention is not limited to the Example demonstrated below, A various change is possible.

  FIG. 1 is a hydraulic circuit diagram of an engine control apparatus according to an embodiment of the present invention. The engine 2 is a diesel engine, and the engine output torque is controlled by adjusting the amount of fuel injected into the cylinder of the engine 2. This fuel adjustment can be performed by controlling a conventionally known fuel injection device 3 with a control signal from the controller 7.

  A variable displacement hydraulic pump 6 (hereinafter simply referred to as a hydraulic pump 6) is connected to the output shaft 5 of the engine 2, and the hydraulic pump 6 is driven by the rotation of the output shaft 5. The tilt angle of the swash plate 16a of the hydraulic pump 6 is controlled by the pump control device 8, and the pump capacity D (cc / rev) of the hydraulic pump 6 changes as the tilt angle of the swash plate 16a changes.

  The pump control device 8 includes a servo cylinder 12 that controls the tilt angle of the swash plate 16a, and an LS valve (load sensing valve) 17 that is controlled in accordance with the differential pressure between the pump pressure and the load pressure of the actuator 10. It is configured. The servo cylinder 12 includes a servo piston 14 that acts on the swash plate 16a, and the discharge pressure from the hydraulic pump 6 can be taken out by oil passages 27a and 27b. The LS valve 17 is operated according to the differential pressure between the discharge pressure taken out from the oil passage 27a and the load pressure of the actuator 10 taken out from the pilot oil passage 28, and the servo piston 14 is controlled by the operation of the LS valve 17. It has become.

  By controlling the servo piston 14, the tilt angle of the swash plate 16a in the hydraulic pump 6 is controlled. Further, the flow rate supplied to the actuator 10 is controlled by controlling the control valve 9 in accordance with the operation amount of the operation lever 11a provided in the operation lever device 11. The pump control device 8 can be configured by a known load sensing control device.

  The pressure oil discharged from the hydraulic pump 6 is supplied to the control valve 9 through the discharge oil passage 25. The control valve 9 is configured as a switching valve that can be switched to the 5-port 3 position. By selectively supplying the pressure oil output from the control valve 9 to the oil passages 26a and 26b, the actuator 10 is Can be operated.

  The actuator is not limited to the illustrated hydraulic cylinder type actuator, and may be a hydraulic motor, or may be configured as a rotary type actuator. In addition, only one set of control valve 9 and actuator 10 is illustrated, but multiple sets of control valve 9 and actuator 10 can be configured to operate multiple actuators with one control valve. It can also be configured to do so.

  That is, for example, when an actuator is described using a hydraulic excavator as an example of a working vehicle, a boom hydraulic cylinder, an arm hydraulic cylinder, a bucket hydraulic cylinder, a left traveling hydraulic motor, a right traveling hydraulic motor, a turning motor, and the like It will be used as an actuator. In FIG. 1, among these actuators, for example, a boom hydraulic cylinder is shown as a representative.

  When the operation lever 11a is operated from the neutral position, pilot pressure (PPC pressure) is output from the operation lever device 11 according to the operation direction and operation amount of the operation lever 11a. The output pilot pressure is applied to one of the left and right pilot ports of the control valve 9. As a result, the control valve 9 is switched from the (II) position, which is the neutral position, to the left and right (I) positions or (III) positions.

  When the control valve 9 is switched from the (II) position to the (I) position, the discharge pressure oil from the hydraulic pump 6 can be supplied from the oil passage 26b to the bottom side of the actuator 10, and the piston of the actuator 10 is extended. Can be made. At this time, the pressure oil on the head side of the actuator 10 is discharged from the oil passage 26a through the control valve 9 to the tank 22. The discharge pressure from the hydraulic pump 6 can be detected by the pressure sensor 36.

  Similarly, when the control valve 9 is switched to the (III) position, the discharge pressure oil from the hydraulic pump 6 can be supplied from the oil passage 26a to the head side of the actuator 10, and the piston of the actuator 10 can be reduced. it can. At this time, the pressure oil on the bottom side of the actuator 10 is discharged from the oil passage 26b to the tank 22 through the control valve 9.

  An oil passage 27c branches off from the middle of the discharge oil passage 25, and an unload valve 15 is disposed in the oil passage 27c. The unload valve 15 is connected to the tank 22 and can be switched between a position for blocking the oil passage 27c and a position for communication. The oil pressure in the oil passage 27c acts as a pressing force for switching the unload valve 15 to the communication position.

  Further, the pilot pressure of the pilot oil passage 28 taking out the load pressure of the actuator 10 and the spring force of the spring that applies a certain differential pressure act as a pressing force for switching the unload valve 15 to the shut-off position. The unload valve 15 is controlled by the differential pressure between the pilot pressure in the pilot oil passage 28 and the spring force of the spring and the oil pressure in the oil passage 27c.

  When the operator operates the fuel dial 4 as the command means and selects one command value from command values that can be variably commanded, the target rotational speed of the engine 2 corresponding to the selected command value can be set. it can. In accordance with the target rotational speed set in this way, it is possible to set an area for high speed control in which engine load and engine output torque are matched.

  Hereinafter, engine control performed by setting an area for high-speed control in which engine load and engine output torque are matched according to the set target rotational speed will be described with reference to FIGS. 1 to 3. This engine control is described in detail in the above-mentioned Patent Document 2 (International Publication WO2008 / 0887847).

  A first target speed Nh (N'h), which is the maximum target speed of the engine, is set corresponding to the command value of the fuel dial 4, and a rated point corresponding to the first target speed Nh (N'h) A high-speed control area Fa passing through K1 can be set. Further, when the first target rotational speed Nb (N′b), which is a target rotational speed lower than the maximum target rotational speed of the engine, is set according to the operation of the fuel dial 4, as shown in FIG. A high-speed control region Fb corresponding to one target rotational speed Nb (N'b) is selected. At this time, the target engine speed of the engine 2 is the first target engine speed Nb (N′b).

  Note that the target engine speed N′b of the engine 2 is the sum of the engine friction torque at no load and the hydraulic system loss torque and the engine output when controlling the engine target engine speed to the first engine speed Nb. It is determined as a point where torque matches. In actual engine control, a line connecting the target rotational speed N′b and the matching point Ps is set as the high-speed control region Fb.

  In the following, description will be made using an example in which the target rotational speed N′b is higher than the first target rotational speed Nb. However, the target rotational speed N′b and the first target rotational speed Nb should be matched. Alternatively, the target rotational speed N′b can be brought to a lower rotational side than the first target rotational speed Nb. Further, in the following description, a rotational speed N′c with a dash is described, for example, as a first target rotational speed Nc (N′c), but the rotational speed N′c with a dash is based on the above description. It is a thing.

  When the operator operates the fuel dial 4 to set a low target rotational speed Nc (N'c) different from the initially selected target rotational speed Nb (N'b), as shown in FIG. As the above-mentioned area, the high-speed control area Fc on the low rotation speed side is set. The target rotational speed Nc (N'c) set at this time becomes the first target rotational speed.

  The region defined by the maximum torque line R in the torque diagram of FIG. 3 shows the performance that the engine 2 can produce. At the rated point K1 on the maximum torque line R, the output (horsepower) of the engine 2 becomes maximum. M indicates an equal fuel consumption curve of the engine 2, and the center side of the equal fuel consumption curve is the minimum fuel consumption region.

In the following, the first target speed Nh (N′h), which is the maximum target speed of the engine, is set corresponding to the command value of the fuel dial 4 and corresponds to the first target speed Nh (N′h). The case where the high-speed control region F1 passing through the rated point K1 is set will be described as an example. That is, the engine control performed while matching the engine load and the engine output torque will be described with reference to FIGS. 1 and 3 when the first target rotation speed Nh (N′h) is set.
FIG. 3 shows a state where the engine output torque increases.

  When the controller 7 shown in FIG. 1 reads the command value of the fuel dial 4, the controller 7 uses the first setting means 30 to set the first target rotational speed Nh of the engine 2 according to the read command value of the fuel dial 4. (N′h) is set, and the high-speed control region F1 is set based on the set first target rotational speed Nh (N′h).

  As shown in FIG. 3, when the first target rotational speed Nh (N′h) and the high-speed control region F1 are set, the controller 7 uses the first setting means 30 to set the first target rotational speed Nh ( N′h), corresponding to the second target rotational speed N2 (N′2) and the second target rotational speed N2 (N′2) on the low rotational speed side set in advance corresponding to the high-speed control region F1 The high-speed control area F2 is determined.

  In FIG. 3, a line connecting the high idle point N'h at the maximum target rotational speed Nh and the rated point K1 is shown as a high-speed control region F1. This high idle point N′h is the engine at no load when the target engine speed of the engine is controlled to the maximum target engine speed Nh as already described in the description of the high-speed control region Fb using FIG. The total value of the friction torque and the loss torque of the hydraulic system can be determined as a point where the engine output torque matches.

  As the high speed control area F2, for example, when the operation lever 11a of the hydraulic excavator is operated, the operation speed is hardly decreased by the load sensing control even when compared with the control in the high speed control area F1. It can be set in advance as a control area. That is, the high speed control is performed so that the target rotational speed is obtained from the second setting means 31 for setting the correspondence between the target rotational speed and the pump capacity of the hydraulic pump 6 and the correspondence relation between the target rotational speed and the engine torque. Area F2 is set.

  When the operation lever 11a is operated, as indicated by a fine dotted line in FIG. 3, the controller 7 controls the fuel injection device 3 so that matching between the engine load and the engine output torque is performed on the high-speed control region F2. Will do. Then, the operator operates the operation lever 11a to perform control to increase the work implement speed of the hydraulic excavator.

  Here, the case where the operator greatly operates the operation lever 11a to increase the work implement speed of the hydraulic excavator will be further described. When the operation lever 11a is operated greatly and thereby the control valve 9 is switched to, for example, the (I) position, the opening area 9a at the (I) position of the control valve 9 increases, and the pump discharge pressure and the pilot in the discharge oil passage 25 increase. The differential pressure from the load pressure in the oil passage 28 decreases. At this time, the pump control device 8 configured as a load sensing control device operates in a direction to increase the pump capacity of the hydraulic pump 6.

  When the pump capacity of the hydraulic pump 6 increases to the maximum pump capacity state, the discharge amount from the hydraulic pump 6 in the high-speed control region F2 becomes the maximum discharge amount that can be discharged from the hydraulic pump 6 in the high-speed control region F2. be able to. In this manner, engine control can be performed while matching the engine load and the engine output torque.

  FIG. 4 shows a case where the engine speed is reduced from the first target speed Nh to the second target speed N2, and the engine control is performed from the standby state where the control valve 9 is in the neutral position and the operation is suspended. This will be described with reference to FIG. In FIGS. 4, 5, and 7, which will be described below, the description of N ′ 2, N′h, etc., which are rotation speeds with dashes, is omitted.

  FIG. 4 shows a torque diagram of the engine, where the vertical axis indicates the engine torque and the horizontal axis indicates the engine speed. When the engine speed is lowered to a low speed target speed, for example, the second target speed N2, and the work is started from the standby state and the engine control is performed based on the high speed control region F2, the engine 2 is suddenly A load is applied, and the rotational speed of the engine 2 decreases as shown in FIG.

  Then, as shown in FIG. 4, when the transition from the standby state where the control valve 9 is set to the neutral position and the operation is suspended to the non-standby state where the operation is performed is started from the second target rotational speed N2, Compared with the case where the engine speed starts from the third target speed N3 which is higher than the 2 target speed N2, the engine torque reaches the engine stall prevention torque limit line 34 earlier.

  Therefore, in the present invention, in the standby state, when the engine speed is controlled at the third target rotational speed N3 by reducing the decrease range of the second target rotational speed N2, the engine enters the non-standby state in which work is performed from the standby state. After the shift to the high-speed control area F2, the engine control based on the high-speed control area F2 is performed after the shift to the high-speed control area F2.

  Further, whether or not the engine is in the standby state by the standby state detection means 33 provided in the controller 7 is determined based on whether or not the engine torque is smaller than the predetermined value T1. For example, as shown in FIG. 5, in the standby state, the amount of decrease in the second target speed N2 is reduced and engine control is performed at the third target speed N3, and the engine torque becomes greater than a predetermined value T1. When it is determined that it is not in the standby state but is in a non-standby state in which work is performed, the process shifts to the high-speed control area F2, and after the shift to the high-speed control area F2, engine control is performed based on the high-speed control area F2. I tried to make it.

  Note that, in order to determine whether or not the standby state is detected by the standby state detection means 33, in addition to determining by detecting the engine torque as described above, by detecting the pilot pressure that operates the control valve 9 Alternatively, the determination can be made either by detecting the pump capacity of the hydraulic pump 6 or by detecting the pump discharge pressure from the hydraulic pump 6.

  As the predetermined value of the engine torque for switching the target rotational speed described above, for example, the engine torque when the actuator operated by the hydraulic pump 6 starts operation is experimentally obtained, and the obtained value is set as the predetermined value described above. Can be set. For example, when the operation lever 11a is in the neutral position, that is, when the engine is idling, the engine torque often shows a value of 2 to 3 kgm. When the engine torque reaches a value of 5 kgm, the actuator starts to operate, and from the time when the engine torque indicates a value of 6 kgm, the actuator starts full-scale operation.

  Therefore, in the case of the above-described example, for example, 5 kgm is set as the predetermined value T1 of the engine torque, and 6 kgm is set as the value T2 of the engine torque when the shift to the high speed control region F2 is completed. it can. When the engine torque is in the range of 5 kgm or less, the engine control is performed at the third target rotational speed N3. When the engine torque becomes greater than 5 kgm, the shift to the high speed control region F2 is performed and the engine torque is 6 kgm. As described above, after the shift to the high-speed control area F2, the engine control based on the high-speed control area F2 can be performed.

  In the present invention, such engine control is performed, and the engine control can be performed as shown in FIG. That is, the first target speed Nh of the engine 2 is set according to the command value of the fuel dial 4, and the second target speed N2 corresponding to the first target speed Nh is set. Then, in the range where the engine torque is less than or equal to a predetermined value, the second target rotational speed N2 is reduced by means 32 (see FIG. 1) for reducing the lowering speed of the second target rotational speed N2. A target rotational speed N3 is set, and engine control is performed with the target rotational speed of the engine 2 as the third target rotational speed N3 within a range where the engine torque is not more than the predetermined value T1 as described above.

  When the engine torque becomes larger than the predetermined value T1, as described above, the target rotational speed of the engine 2 is changed from the third target rotational speed N3 to the high speed control region F2 based on the second target rotational speed N2. Let After the shift to the high speed control area F2, engine control based on the high speed control area F2 is performed.

  The state when the engine control is performed and the effects achieved by the present invention will be described with reference to FIG. FIG. 6 shows the state from the standby state in which the operation lever 11a is in the neutral position until the stable engine control is performed in the high-speed control region F2, with the time axis on the horizontal axis. It is. The top of FIG. 6 shows the state of the engine speed with the vertical axis representing the engine speed N (rpm), and the middle stage shows the pump flow rate Q (L / min) from the hydraulic pump 6 with the pump flow rate Q (L / min). The lower part shows the pump capacity of the hydraulic pump 6 with the vertical axis representing the pump capacity D (cc / rev).

  In FIG. 6, the thick line indicates the case where the engine control is performed without lowering the engine speed to the low speed side (hereinafter referred to as control A), that is, the engine control is performed on the high speed control region F1 in FIG. Shows the case. When the control according to the present invention is performed, that is, in the range where the engine torque is equal to or less than T1 (see FIG. 5), the thick dotted line indicates that the engine control is performed at the third target speed N3 and the engine torque is greater than T1. When the engine torque has shifted to the high speed control area F2, the engine torque becomes T2 (see FIG. 5) or more, and after the shift to the high speed control area F2, the engine control based on the high speed control area F2 is performed. The case (hereinafter referred to as control B) is shown. The thin line indicates the case where engine control based on the high speed control region F2 is performed from the second target rotational speed N2 (hereinafter referred to as control C).

  When the operation lever 11a is in the neutral position, the pump displacement shown in the lower part of FIG. 6 is that even if there is a difference in the target rotational speed of the engine 2 between the control A, the control B and the control C, Both are in the minimum state. For reference, the lower part of FIG. 6 is a pump capacity that can discharge the same flow rate as in control A even when control lever 11a is in the neutral position, even in control B and control C. Is indicated by a thin dotted line as a virtual line.

  When the control lever 11a is at the neutral position, the target speed of the engine 2 shown in the upper part of FIG. 6 is as follows. In the control A, the first target speed Nh of the engine 2 is the second target speed in the other controls B and C. Since the speed is set higher than the number N2 and the third target speed N3, the speed of the engine 2 is also higher than that during the control in the other controls B and C. Then, as the rotational speed of the engine 2, the engine rotational speed in the control B is next higher than the engine rotational speed in the control C.

  Therefore, when the operation lever 11a is in the neutral position, the flow rate discharged from the hydraulic pump 6 is the highest in the control A and the lowest in the control C as shown in the middle stage of FIG. The time of control B is intermediate between the time of control A and the time of control C.

  When the operation of the operation lever 11a is started at time t1, the first target speed Nh and the second target speed N2 of the respective engines 2 are not changed in the control A and the control C, but the engine 2 in the control B is not changed. The target rotational speed is controlled to be the third target rotational speed N3 when the engine torque is less than or equal to a predetermined value, and to the second target rotational speed N2 when the engine torque exceeds the predetermined value.

  As a result, as shown by the temporal change in the pump capacity shown in the lower part of FIG. 6, the control B and the control C can quickly reach the pump capacity state indicated by the virtual line. Moreover, the pump capacity can be increased in the case of the control B and the control C compared to the case of the control A, so even if the engine speed is smaller than that of the control A, the control A and The same discharge flow rate can be discharged from the hydraulic pump 6.

  As for the discharge flow rate from the hydraulic pump 6 shown in the middle stage of FIG. 6, the control B can quickly discharge from the hydraulic pump 6 the same flow rate as the discharge flow rate in the control A compared to the control C. As a result, fuel efficiency can be improved without impairing the operability of the operation lever 11a, and engine control comparable to the operation of the operation lever 11a in the control A can be performed.

  In the above description, as shown in FIG. 5, the high-speed control region F2 has been described in a state substantially parallel to the high-speed control region F1, but for example, the high-speed control region F2 shown in FIG. The present invention can also be suitably applied to those that perform engine control along the region F3. As in the case described with reference to FIG. 5, in FIG. 7, when the engine torque is within the predetermined value T1, the engine 2 is controlled to rotate with the third target speed N3 as the target speed of the engine 2, and the engine torque When the value exceeds the predetermined value T1, the target rotational speed of the engine 2 can be smoothly shifted from the third target rotational speed N3 to the second target rotational speed N2.

  After the engine torque becomes equal to or higher than T2 and the target rotational speed of the engine 2 reaches the second target rotational speed N2, engine control along the high-speed control region F3 can be performed.

  As shown in FIGS. 8 to 12, various methods are used to detect whether or not the engine 2 is in a standby state that serves as a reference for changing the target speed of the engine 2 from the third target speed N3 to the second target speed N2. Can be obtained. FIG. 8 shows a configuration in which a plurality of hydraulic pumps 6 driven by the engine 2 are provided.

  In general, the relationship between the discharge pressure P, the discharge capacity D (pump capacity D) of the hydraulic pump and the engine torque T can be expressed as T = P · D / 200π. From this relational expression, when a plurality of variable displacement hydraulic pumps 6a and 6b (hereinafter referred to as hydraulic pumps 6a and 6b) are provided as shown in FIG. 8, engine torque T = (hydraulic pump 6a ) Pump pressure P1 × pump capacity D1 of the hydraulic pump 6a + pump pressure P2 of the hydraulic pump 6b × pump capacity D2 + of the hydraulic pump 6b +) / 200π.

  That is, it can be obtained as a value obtained by dividing the sum of the products of the pump pressure and the pump capacity in each hydraulic pump connected to the engine 2 by 200π. The discharge pressure P of each hydraulic pump can be detected by pressure sensors 36a, 36b... Provided in the discharge passages of the hydraulic pumps 6a, 6b, and the pump capacity D of each hydraulic pump 6a, 6b is inclined. It can be detected by the plate angle sensors 37a, 37b.

  When only one hydraulic pump 6 is provided, the engine torque can be calculated only for the hydraulic pump 6a. When there are a plurality of hydraulic pumps 6, a value obtained by summing up the respective torques calculated for each hydraulic pump can be obtained as the engine torque.

  As described above, the value of the engine torque T is, for example, the engine output torque held in the controller 7 instead of directly obtaining from the discharge pressure P and the discharge capacity D (pump capacity D) of the hydraulic pump 6. The command value can also be used.

  Further, as shown in FIG. 9, the operation levers 38a, 38b, 38c, 38d,. When any one of the detected pilot pressures is detected as a pilot pressure and exceeds a predetermined value set in advance, or when the total value of each pilot pressure exceeds a predetermined value set in a standby state Instead, it can be assumed to be in a non-standby state. The pilot pressure in each operation lever 38a, 38b, 38c, 38d... Can be detected by pressure sensors 39a, 39b, 39c, 39d.

  Further, as shown in FIG. 10, when any one of the pump pressures of the hydraulic pumps 6a, 6b,... Driven by the engine 2 exceeds a predetermined value set in advance, When the average value exceeds a predetermined value set in advance, it can be assumed that the device has entered a non-standby state instead of a standby state.

Furthermore, as shown in FIG. 11, each hydraulic pump 6 a is detected by a slope angle sensor 37 a, 37 b... Detecting each swash plate angle in each hydraulic pump 6 a, 6 b,. , 6b,... When any one of the pump capacities exceeds a preset predetermined value, or the sum of the pump capacities of the hydraulic pumps 6a, 6b,. When the value is exceeded, it can be assumed that the device has entered a non-standby state instead of a standby state.
In this manner, for each calculation cycle of the controller 7, it is determined whether or not the vehicle is in the standby state shown in FIG. 12, and the target rotational speed for engine control is set.

  The hydraulic circuit in the present invention is not limited to the load sensing type hydraulic circuit as shown in FIG. 1, and the present invention is also suitably applied to a conventionally known open center type hydraulic circuit. be able to. Moreover, as an open center type hydraulic circuit, a negative control type hydraulic circuit and a positive control type hydraulic circuit are known. The present invention is preferably applied to both types of hydraulic circuits. can do.

  The technical idea of the present invention can be applied to engine control for a diesel engine of a construction machine.

DESCRIPTION OF SYMBOLS 2 ... Engine, 4 ... Fuel dial, 6 ... Variable displacement hydraulic pump, 7 ... Controller, 9 ... Control valve, 11 ... Operation lever device, 12 ... Servo cylinder , 30 ... 1st setting means, 31 ... 2nd setting means, 32 ... means for reducing the reduction width, 33 ... standby state detection means, F1 to F3 ... high speed control area, Nh: rated speed (first target speed), N2: second target speed, N3: third target speed.

Claims (6)

A variable displacement hydraulic pump driven by an engine;
A hydraulic actuator driven by pressure oil discharged from the hydraulic pump;
A control valve for controlling the pressure oil discharged from the hydraulic pump to supply and discharge to the hydraulic actuator;
Command means for selecting and commanding one command value from command values that can be commanded variably;
A first target rotational speed of the engine is set according to the command value commanded by the command means, and a second rotational speed lower than the first target rotational speed is set based on the set first target rotational speed. First setting means for setting a target rotational speed;
With
An engine control device that performs engine control based on the second target rotational speed,
Standby state detecting means for detecting whether or not the control valve is in a standby state in a neutral position;
Means for reducing the amount of decrease in the second target rotational speed when the standby state detecting means detects that the standby state is detected;
When the standby state detecting means detects that it is in the standby state, engine control is performed on the basis of the third target rotational speed in which the reduction range is reduced by the means for reducing the reduction range,
When engine control based on the third target rotational speed is being performed, if the standby state detection means detects that the engine is not in the standby state, the second engine control is performed based on the engine control based on the third target rotational speed. A control apparatus for an engine in a construction machine, wherein the engine control is based on a target rotational speed.   The standby state detection means detects engine torque, and determines that the standby state is detected when the value is equal to or less than a predetermined value for engine torque set in advance, and the standby state when the value is larger than the predetermined value for engine torque. The engine control apparatus for a construction machine according to claim 1, wherein it is determined that the engine is not in a state.   The standby state detecting means detects a pilot pressure for operating the control valve, and determines that the standby state is detected when the value is equal to or less than a predetermined value for pilot pressure, which is larger than the predetermined value for pilot pressure. 2. The engine control apparatus for a construction machine according to claim 1, wherein it is determined that the state is not the standby state.   The standby state detection means detects the pump displacement of the hydraulic pump, and determines that the standby state is greater than a predetermined value for the pump displacement when the value is less than or equal to a predetermined value for the pump displacement set in advance. 2. The engine control apparatus for a construction machine according to claim 1, wherein it is determined that the state is not the standby state.   The standby state detecting means detects a pump discharge pressure from the hydraulic pump, and determines that the standby state is detected when the value is equal to or less than a predetermined value for a pump discharge pressure set in advance, and determines a predetermined value for the pump discharge pressure. The engine control apparatus for a construction machine according to claim 1, wherein when it is larger, it is determined that the vehicle is not in the standby state. Second setting means for setting a correspondence relationship between the detected pump capacity of the hydraulic pump and the detected engine torque and the target rotational speed at the time of engine control capable of continuously changing the target rotational speed as the engine control. Further comprising
In the engine control in which the target rotational speed can be continuously changed, when the engine control is performed based on the third target rotational speed, the detected value of the pump capacity of the hydraulic pump or the detected engine torque 6. The engine control device for a construction machine according to claim 1, wherein control is performed so as to achieve a target rotational speed obtained from the second setting means in accordance with the value.

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