JP2011157931A - Engine control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine control device for more efficiently controlling the drive of an engine with low fuel cost while securing the flow amount of pressure oil required for the operation of an hydraulic actuator without giving ill effects to the operation of the hydraulic actuator. <P>SOLUTION: A first target engine speed is set depending on a command value commanded by a command unit, and a second target engine speed lower than the first target engine speed is set in accordance with the first target engine speed. A target engine speed corresponding to the capacity of a pump is also set using the second target engine speed as a lower limit value. A second setting tool sets a third target engine speed not lower than the second target engine speed and not higher than the first target engine speed, as an upper limit value for the target engine speed corresponding to the capacity of the pump, depending on the type of the hydraulic actuator to be operated by an operation lever or the combination of the plurality of hydraulic actuators to be operated by the operation lever. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

  For construction machinery, when the pump absorption torque is less than the rated torque of the engine, the engine output torque matches the pump absorption torque in the high-speed control area in the engine output torque characteristic line that shows the relationship between the engine speed and the engine output torque. Has been done. For example, the target engine speed is set corresponding to the setting with the fuel dial, and the high speed control region corresponding to the set target engine speed is determined.

  Alternatively, a high speed control region is determined corresponding to the setting with the fuel dial, and a target engine speed of the engine is set corresponding to the determined high speed control region. Then, control for matching the pump absorption torque and the engine output torque is performed in the determined high-speed control region.

  In general, many workers often set the target engine speed to be the rated engine speed or a 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, usually exists in the medium speed rotation speed region and the high torque region on the engine output torque characteristic line. 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 the engine in a fuel-efficient region, it is possible to select a plurality of work modes by previously setting the target engine speed value of the engine and the target output torque value of the engine in association with each work mode. A control apparatus 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.

  That is, the maximum speed of the construction machine working device (hereinafter referred to as working machine) is lower than that in the case where the first working 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.

  In order to solve such problems, the applicant has already applied for an engine control device and a control method thereof (Patent Document 2). According to the engine control device of the present invention, when the pump capacity and the engine output torque are low, the engine drive control is performed based on the second target engine speed that is lower than the set first target engine speed. The engine drive control can be performed so that the target engine speed is set in advance corresponding to the pump displacement of the variable displacement hydraulic pump driven by the engine or the detected engine output torque.

  In particular, the invention of the engine control device described above can improve the fuel consumption of the engine and can change the engine speed very smoothly while ensuring the pump discharge amount required by the work implement. In addition, there is an effect that the uncomfortable feeling that the engine rotation sound changes discontinuously can be prevented.

Japanese Patent Laid-Open No. 10-273919 International Publication No. 2009/104636 Pamphlet

  In the invention of the engine control apparatus introduced as Patent Document 2, the engine speed is lower than the first target engine speed instead of starting the engine drive control from the first target engine speed indicated by the fuel command dial or the like. Engine drive control is started from the second target engine speed.

  When the pump capacity becomes greater than or equal to a predetermined pump capacity during engine drive control from the second target engine speed, the drive control at the second target engine speed shifts to drive control at the first target engine speed. I am letting.

  By the way, the margin of the pump capacity relative to the maximum pump capacity differs depending on which hydraulic actuator is operated or which hydraulic actuators are operated simultaneously. For example, when excavation work is performed by a bucket alone, the flow rate of pressure oil supplied to a hydraulic actuator that operates the bucket does not require as much. Conversely, when the bucket operation and the arm operation are performed simultaneously, a larger amount of pressure oil flow is required as the total amount of pressure oil flow supplied to each hydraulic actuator.

  When supplying the hydraulic oil flow rate to the hydraulic actuator, when there is a margin in the pump capacity relative to the maximum pump capacity, if the engine drive control is performed without reducing the target engine speed, the target engine speed is reduced. Compared to the case, the fuel consumption increases. When there is no allowance for the pump capacity with respect to the maximum pump capacity in supplying the hydraulic oil flow rate to the hydraulic actuator, the pump capacity is immediately increased from the drive control at the second target engine speed to the first target engine speed. It becomes more than a predetermined pump capacity which is a determination condition when shifting to drive control. Therefore, from the early stage when engine drive control is started, the drive control at the second target engine speed shifts to drive control at the first target engine speed.

  When there is no margin of pump capacity with respect to the maximum pump capacity in supplying the pressure oil flow rate to the hydraulic actuator, the engine will operate at an engine speed close to the first target engine speed, resulting in fuel efficiency. Reduction cannot be achieved. Furthermore, even if the pump capacity is changed slightly, the target engine speed goes back and forth between the first target engine speed and the second target engine speed. As a result, in the construction machine, the operation of the hydraulic actuator becomes unstable and the amount of fuel consumption increases.

  The invention of the present application aims to further improve the invention of Patent Document 2 described above, and the target engine speed is determined according to the type of hydraulic actuator to be operated and the combination of a plurality of hydraulic actuators to be operated. An upper limit can be set. An engine control device that can secure the flow rate of the pressure oil required for the operation of the hydraulic actuator without adversely affecting the operation of the hydraulic actuator, and can perform the engine drive control more efficiently with low fuel consumption. The purpose is to provide.

The object of the present invention can be suitably achieved by the first to fourth aspects of the engine control apparatus.
That is, in the engine control apparatus according to the first aspect of the present invention, the variable displacement hydraulic pump driven by the engine, the plurality of hydraulic actuators driven by the discharge hydraulic oil from the hydraulic pump, and the hydraulic pump discharged A plurality of control valves for controlling and supplying pressure oil to and from each of the plurality of hydraulic actuators; at least one operation lever for controlling the plurality of control valves; and a detecting means for detecting a pump capacity of the hydraulic pump; A fuel injection device for controlling fuel supplied to the engine;
A command means for selecting and commanding one command value from command values that can be commanded variably, a first target engine speed is set according to the command value commanded by the command means, and the first target engine First setting means for setting a second target engine speed that is lower than the first target engine speed based on the speed, and a pump capacity with the second target engine speed as a lower limit value Second setting means for setting a corresponding target engine speed;
Control means for controlling the fuel injection device so as to achieve the target engine speed determined from the second setting means,
The second setting means, depending on the type of the hydraulic actuator operated by the operation lever or the combination of the plurality of hydraulic actuators operated by the operation lever, as an upper limit value of the target engine speed corresponding to the pump capacity. The most important feature is that a third target engine speed that is greater than or equal to the second target engine speed and less than or equal to the first target engine speed is set.

  In the second invention of the present application, the third target engine speed is the maximum required flow rate required by the type of the hydraulic actuator operated by the operation lever or the plurality of hydraulic actuators operated by the operation lever. The main feature is that it is set according to the maximum required flow rate required by the combination.

Further, the third feature of the present invention is characterized in that the third target engine speed is set to the same speed as the second target engine speed.
Furthermore, in the fourth invention of the present application, further comprising detection means for detecting engine output torque, the second setting means sets the second target engine speed as a lower limit value and sets the third target engine speed as an upper limit value. Target engine speed corresponding to the pump capacity and target engine speed corresponding to the engine output torque when the second target engine speed is the lower limit and the first target engine speed is the upper limit. The main feature is to set the target engine speed, whichever is higher.

  In the engine control apparatus according to the present invention, since the second target engine speed that is lower than the first target engine speed is set, the engine can be driven to rotate at a lower speed range. Moreover, the third target engine speed that is the upper limit value of the target engine speed can be set according to the type and combination of the hydraulic actuators to be operated.

  That is, when a hydraulic actuator that is expected to cause a margin in the pump capacity relative to the maximum pump capacity is operated, the third target engine speed that is lower than the first target engine speed is set to the target engine speed. By using it as the upper limit of the number, fuel consumption can be reduced. Further, the region where the pump displacement fluctuates is a region where the target engine speed is constant at the third target engine speed. Therefore, the engine speed does not vary according to the pump displacement.

  Further, when a hydraulic actuator that is predicted not to allow a margin in the pump capacity with respect to the maximum pump capacity is operated, the first target engine speed can be used as the upper limit value of the target engine speed. As a result, engine drive control can be performed at the first target engine speed, so that there is no shortage of flow rate.

  Further, by configuring as in the second invention of the present application, the total amount of pressure oil flow required by the hydraulic actuator operated by the operation lever or the total amount required by the plurality of hydraulic actuators operated by the operation lever is always obtained. The pressure oil flow rate can be discharged from the hydraulic pump. In addition, since the pump absorption torque required by the hydraulic pump can be secured at this time, it is possible to meet the intention of the operator who sets the first target engine speed, and the operability of the hydraulic actuator is uncomfortable. There is no.

  Further, by configuring as in the third invention of the present application, particularly when there is a margin in the pump capacity, the engine can be driven to rotate in a low rotation region, so that fuel efficiency can be greatly improved. it can.

  Further, in the situation where the engine output torque becomes high by configuring as in the fourth invention of the present application, the operation using the maximum horsepower of the engine is performed by setting the first target engine speed as the upper limit value. Since it can be performed, more work can be secured.

1 is a hydraulic circuit diagram according to an embodiment of the present invention. (Example) It is a block diagram of a controller. (Example) It is explanatory drawing which sets the 3rd target engine speed according to an operation lever. (Example) It is the figure which showed the relationship between an engine speed and an engine output torque. (Example) It is an engine output torque characteristic line. (Example) It is an engine output torque characteristic line when increasing an engine output torque. (Example) It is the figure which showed the relationship between a pump capacity | capacitance and a target engine speed. (Example) It is a control flow figure concerning the present invention. (Example) It is the figure which showed the relationship from the 1st target engine speed to the 3rd target engine speed. (Example) It is the figure which showed the relationship between engine output torque and target engine speed. (Example) It is the figure which showed the relationship between the 1st target engine speed and the 2nd target engine speed. (Example) It is the figure which showed the relationship between an engine speed and an engine output torque. (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 an engine mounted on a construction machine 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 a conventionally known fuel injection device 3.

  A variable displacement hydraulic pump 6 (hereinafter 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 6a 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 6a changes.

  The pump control device 8 includes a servo cylinder 12 that controls the tilt angle of the swash plate 6a, an LS valve (load sensing valve) 17 that is controlled according to the differential pressure between the pump pressure and the load pressure of the hydraulic actuator 10, It is composed of The servo cylinder 12 includes a servo piston 14 that acts on the swash plate 6a, and hydraulic pressure discharged from the hydraulic pump 6 is supplied via oil passages 27a and 27b. The LS valve 17 operates in accordance with the differential pressure between the hydraulic pressure of the oil passage 27a (pump discharge pressure) and the hydraulic pressure of the pilot oil passage 28 (load pressure of the hydraulic actuator 10), and controls the servo piston 14. Yes.

  By controlling the servo piston 14, the tilt angle of the swash plate 6a in the hydraulic pump 6 is controlled. Further, the flow rate supplied to the hydraulic actuator 10 is controlled by controlling the control valve 9 by the pilot pressure output from the operation lever device 11 according to the operation amount of the operation lever 11a. 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 a 5-port 3 position. By selectively supplying pressure oil output from the control valve 9 to the oil passages 26a and 26b, the hydraulic actuator 10 Can be activated.

  The hydraulic actuator is not limited to the illustrated hydraulic cylinder type hydraulic actuator, and may be a hydraulic motor, or may be configured as a rotary type hydraulic actuator. Further, only two sets of the control valve 9 and the hydraulic actuator 10 are illustrated, but the set of the control valve 9 and the hydraulic actuator 10 can be configured by three or more sets. Moreover, it can also comprise so that several hydraulic actuators may be operated with one control valve.

  Further, the operation lever device 11 can be configured such that the operation lever 11a can be operated in two operation directions, front and rear and left and right, as viewed from the operator, and different control valves can be switched depending on each operation direction. .

  The hydraulic actuator operated by the operation lever device 11, that is, for example, a hydraulic excavator as an example of a construction machine will be described. A boom hydraulic cylinder, an arm hydraulic cylinder, a bucket hydraulic cylinder, a left traveling hydraulic pressure A motor, a right traveling hydraulic motor, a turning motor, and the like are used as the hydraulic actuator. In FIG. 1, among these hydraulic actuators, for example, an arm hydraulic cylinder and a boom hydraulic cylinder are shown as representatives.

  When the operation lever 11a is operated from the neutral position, pilot pressure is output from the operation lever device 11 according to the operation direction and the 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 hydraulic oil from the hydraulic pump 6 can be supplied to the bottom side of the hydraulic actuator 10 from the oil passage 26b. Can be stretched. At this time, the pressure oil on the head side of the hydraulic actuator 10 is discharged from the oil passage 26a through the control valve 9 to the tank 22.

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 hydraulic actuator 10, and the piston of the hydraulic actuator 10 is reduced. Can be made. At this time, the pressure oil on the bottom side of the hydraulic actuator 10 is discharged from the oil passage 26b to the tank 22 through the control valve 9.
Here, the head side of the hydraulic actuator 10 refers to an oil chamber on the rod side of the hydraulic cylinder. The bottom side of the hydraulic actuator 10 refers to the oil chamber on the opposite side of the rod of the hydraulic cylinder.

  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 on which the load pressure of the hydraulic actuator 10 acts and the pressing force of the spring 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 of the pilot oil passage 28 and the spring pressing force and the oil pressure in the oil passage 27c.

  The controller 7 can be realized, for example, by a computer having a storage device used as a program memory or a work memory and a CPU that executes the program. The storage device of the controller 7 stores Table 1 to Table 4 shown in FIG. 8, the correspondence shown in FIG. 7, the correspondence shown in FIG.

  Next, the control of the controller 7 will be described with reference to the block diagram of FIG. In FIG. 2, the command value 37 of the fuel dial 4 is input to the high speed control region selection calculation unit 32 in the controller 7, and the pump torque command required by the hydraulic pump 6 calculated by the pump torque calculation unit 31. The value, the pump capacity corresponding to the swash plate angle of the hydraulic pump 6, and the discrimination result from the type / combination discrimination unit 34 of the hydraulic actuator to be operated are input.

  The pump torque calculation unit 31 calculates the pump pressure (pump discharge pressure) discharged from the hydraulic pump 6 detected by the pump pressure sensor 38 and the swash plate angle command value calculation unit 30 that commands the swash plate angle of the hydraulic pump 6. The swash plate angle of the hydraulic pump 6 is input. The pump torque calculator 31 calculates a pump torque command value (engine output torque command value) required by the hydraulic pump 6 from the input swash plate angle of the hydraulic pump 6 and the pump pressure of the hydraulic pump 6.

That is, generally, the relationship among the pump discharge pressure P (pump pressure P), the discharge capacity D (pump capacity D) and the engine output torque T of the hydraulic pump 6 can be expressed as T = P · D / 200π.
From this relational expression, the swash plate angle command calculation unit 30 detects the rotational speed of the hydraulic pump 6 driven by the engine 2 as the engine rotational speed, and the pump pressure that is the discharge pressure from the hydraulic pump 6 is detected by the pump pressure sensor. By detecting by 38, the engine output torque (pump torque) can be calculated.

The pump torque command value (engine output torque command value) required by the hydraulic pump 6 to be calculated in the pump torque calculation unit 31 is obtained by calculating the pump pressure detection value and the command value calculated by the swash plate angle command calculation unit 30. Instead of using and calculating, it is also possible to calculate using the detection value of the pump pressure sensor 38 (pump pressure P) and the detection value of the swash plate angle sensor 39 (pump capacity D).
The method of calculating by the pump torque calculating unit 31 using the detected value of the pump pressure and the detected value of the swash plate angle sensor 39 is shown by using dotted arrows in FIG.

  The calculation in the swash plate angle command calculation unit 30 can be calculated using the pump pressure P detected by the pump pressure sensor 38 and the detection value from the engine rotation sensor 20. The calculation result in the swash plate angle command calculation unit 30 is input to the pump torque calculation unit 31. That is, the pump capacity D of the hydraulic pump 6 at that time can be calculated from the pump pressure P and the rotational speed of the hydraulic pump 6, and the pump swash plate angle corresponding to the pump capacity D can be calculated.

  In the type / combination discriminating section 34 of the hydraulic actuator to be operated, when a plurality of operating lever devices 11 are operated as shown in FIG. 3, a signal obtained by detecting the pilot pressure output from the operating lever device 11 by the pressure sensor 40 Is input, and it is possible to determine which operation lever device 11a of the operation lever device 11 is operated by the operator. That is, when the operation lever 11a is operated alone, the type of the operation lever 11a being operated is selected, and when a plurality of operation levers 11a are operated, in which combination the operation lever 11a is It is possible to determine whether each is operated.

The high-speed control region selection calculation unit 32 instructs the engine 2 to provide a high-speed control region command value 33 for performing drive control of the engine 2.
The pump pressure sensor 38 is configured to detect the pump pressure in the discharge oil passage 25 of FIG. The swash plate angle sensor 39 is configured as a sensor that detects the swash plate angle of the hydraulic pump 6.

  The pump torque calculation unit 31 uses the value input to the pump torque calculation unit 31 using the relationship diagram between the engine output torque T and the engine speed N as shown in FIG. Torque) can be calculated.

As shown in FIG. 4, the engine speed sensor 20 in the high-speed control region Fn set by the command value 37 of the fuel dial 4 corresponding to the target engine speed Nn at that time, that is, the target engine speed Nn. From the detected intersection with the engine speed Nr at that time, the estimated torque Tg of the engine at that time can be obtained.
The pump torque calculation unit 31 can also calculate the engine output torque at that time from an engine output torque command value (not shown) and the engine speed detected by the engine rotation sensor 20.

  The pump torque calculation unit 31 calculates the output torque of the hydraulic pump 6 from the pump capacity detected by the swash plate angle sensor 39 and the pump discharge pressure detected by the pump pressure sensor 38, and the calculated output torque is It can also be obtained as the engine output torque at the time. The pump torque calculation unit 31, the pump pressure sensor 38, the swash plate angle command value calculation unit 30, the engine speed sensor 20, and the swash plate angle sensor 39 are detected to detect the pump capacity of the hydraulic pump by combining them. And a function as detection means for detecting engine output torque.

  Here, when the operator operates the fuel dial 4 as the command means and selects one command value from command values that can be commanded variably, the first target engine speed corresponding to the selected command value is set. can do. According to the first target engine speed set in this way, a high-speed control region that matches the pump absorption torque and the engine output torque can be set.

  That is, as shown in FIG. 5, when the target engine speed Nb (N′b), which is the first target engine speed, is set according to the operation of the fuel dial 4, the first target engine speed Nb (N The high-speed control area Fb corresponding to 'b) is selected. At this time, the target engine rotational speed of the engine is the rotational speed Nb (N′b).

  The target engine speed N′b matches the engine output torque with the total value of the engine friction torque and the hydraulic system loss torque when there is no load when the target engine speed is controlled to the speed Nb. It will be determined as a point. In actual engine control, a line connecting the target engine speed N′b and the matching point Kb is set as the high-speed control region Fb.

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

  Further, when the operator operates the fuel dial 4 to set a new first target engine speed Nc lower than the first target engine speed Nb selected first, the high-speed control area has a high speed on the low speed side. The control area Fc is set.

  Thus, by setting the fuel dial 4, one high-speed control region can be set corresponding to the first target engine speed that can be selected by the fuel dial 4. That is, by selecting the fuel dial 4, for example, as shown in FIG. 5, a high-speed control region Fa passing through the maximum horsepower point K1 and a plurality of high-speed control regions Fb, Fc on the low rotation region side from the high-speed control region Fa. ,... Can be set to any high-speed control area, or any high-speed control area in the middle of these high-speed control areas.

  The region defined by the maximum torque line R in the engine output torque characteristic line of FIG. 6 shows the performance that the engine 2 can produce. The place where the output (horsepower) of the engine 2 is maximum is the maximum horsepower point K1 on the maximum torque line R. 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. K4 on the maximum torque line R indicates the maximum torque point at which the torque of the engine 2 is maximum.

  In the following, the first target engine speed N1, which is the maximum target engine speed of the engine, is set corresponding to the command value 37 of the fuel dial 4, and the maximum horsepower point K1 corresponding to the first target engine speed N1 is set. A case where the high-speed control region F1 passing through is set will be described as an example.

  Incidentally, in response to the command value 37 of the fuel dial 4 shown in FIG. 1, the first target engine speed N1 which is the rated speed as the engine speed (in FIG. 5, the rated speed is indicated as Nh). However, in FIG. 6, the first target engine speed N1 is also the rated speed.), And a description of the case where the high speed control region F1 passing through the maximum horsepower point K1 corresponding to the first target engine speed N1 is set However, the present invention is not limited to the case where the high-speed control region F1 passing through the maximum horsepower point K1 is set. For example, as a high-speed control region corresponding to the set first target engine speed, the plurality of high-speed control regions Fb, Fc,... In FIG. Even when an arbitrary high-speed control area is set in the middle, the present invention can be suitably applied to each set high-speed control area.

  FIG. 6 shows a state where the engine output torque increases. In the present invention, the high-speed control region F1 can be set in accordance with the first target engine speed N1 set by the operator corresponding to the command value at the fuel dial 4. Then, a second target engine speed N2 that is lower than the first target engine speed N1 is set, and engine drive control is performed based on the high-speed control region F2 corresponding to the second target engine speed N2. Has started.

  The high speed control region selection calculating unit 32 shown in FIG. 2 serves as a first setting means for setting the second target engine speed N2 from the first target engine speed N1 set by the command value 37 of the fuel dial 4. It has a function.

  When engine drive control is performed based on the high-speed control region F2, the pump capacity of the hydraulic pump 6 is set to a predetermined first pump capacity D1 (see FIG. 7, in FIG. The position of the capacity D1 is indicated as the first setting position B.) When the above is reached, the target engine speed Nn corresponding to the pump capacity Dn is always set between the high speed control area F2 and the high speed control area F3. It is configured to perform engine drive control as required.

The high speed control region F3 can be set as a high speed control region according to the third target engine speed N3. The third target engine speed N3 can be set as an upper limit value of the target engine speed that is equal to or lower than the first target engine speed N1 and equal to or higher than the second target engine speed N2. The third target engine speed N3 can be set by the type of hydraulic actuator operated by the operation lever 11a and the combination of a plurality of hydraulic actuators operated by the operation lever 11a.
The upper limit value of the third target engine speed can also be set according to the maximum required flow rate required by the hydraulic actuator operated by the operation lever 11a.

  In the following, when the first target engine speed N1 is set, how to set the second target engine speed N2 that is lower than the first target engine speed N1, and the target engine speed How to set the third target engine speed N3 that is the upper limit of the number will be described.

  When the third target engine speed N3 is set as the upper limit value of the target engine speed corresponding to the type of hydraulic actuator to be operated or the combination of the plurality of operated hydraulic actuators, for example, the control flow of the present invention is It can be set as shown in Table 2 of FIG.

  As shown in Table 2 of FIG. 8, for example, when the single operation of only the traveling operation is performed by the operation lever 11a, the third target engine speed N3 can be set as 1900 rpm. When performing a combined operation of a traveling operation and a bucket excavation operation, the third target engine speed N3 can be set as 2500 rpm.

Although not described in Table 2, the third target engine speed N3 can be set to 1700 rpm when performing a single operation of bucket excavation. In other cases, the third target engine speed N3 can be set to 2500 rpm.
Note that the numerical values shown in Table 2 of FIG. 8 and the above-described numerical values are examples, and the third target engine speed N3 can be appropriately set according to the type and size of the construction machine.

  As described above, when a hydraulic actuator that is predicted to generate a margin in the pump capacity with respect to the maximum pump capacity is operated, the upper limit value of the target engine speed with respect to the pump capacity is set low. That is, the third target engine speed N3 can be configured to be smaller than the first target engine speed N1.

  Furthermore, when a hydraulic actuator that is predicted not to cause a margin in the pump capacity with respect to the maximum pump capacity is operated, the third target engine speed N3 is set to the first target engine speed to The pump flow rate supplied to the actuator can be ensured.

  Here, the maximum pump flow rate Q1 at the first target engine speed N1 can be expressed by the product Q1 = N1 · Dmax of the first target engine speed N1 and the maximum pump capacity Dmax. Accordingly, if the maximum required flow rate is Qa (Qa <Qmax) depending on the type and combination of the hydraulic actuators to be operated, the third target engine speed N is smaller than the first target engine speed N1. The engine speed can be lowered to N3 = Qa / Dmax. Therefore, in this embodiment, as shown in FIG. 7 (Table 3 in FIG. 8), the upper limit value of the target engine speed N is limited to the third target engine speed N3. As a result, when the pump capacity D of the hydraulic pump 6 becomes equal to or greater than the third pump capacity D3, the target engine speed N is constant at the third target engine speed N3.

  As a result, it is possible to prevent the engine speed from fluctuating during engine drive control at the third target engine speed, and to increase the fuel consumption reduction effect.

Furthermore, the third target engine speed can be set to the same speed as the second target engine speed. At this time, since the engine can be driven on the low rotation side, the fuel consumption reduction effect can be greatly improved.
Further description will be continued with reference to FIG. 9. In FIG. 9, the state indicated by the alternate long and short dash line extending from the thick line indicates the case where the third target engine speed N3 is not provided. As in the present invention, when a hydraulic actuator that is expected to generate a margin in the pump capacity with respect to the maximum pump capacity is operated, the third target engine speed N3 is provided as the upper limit value of the target engine speed N. This case is indicated by a solid thick line.

  As shown in FIG. 9, in the state indicated by the one-dot chain line extending from the thick line, 2100 rpm is set as the first target engine speed N1, and 1800 rpm is set as the second target engine speed N2. . In the state indicated by the alternate long and short dash line extending from the thick line, the control configuration does not use the third target engine speed.

  Explaining the state indicated by the alternate long and short dash line extending from the bold line, engine drive control is performed at the second target engine speed N2 of 1800 rpm until the pump capacity D reaches 90% (D1) of the maximum pump capacity. When the pump capacity D becomes 90% (D1) or more of the maximum pump capacity, the pump capacity D is increased while the target engine speed N is increased. When the pump capacity D becomes 95% (D2) or more of the maximum pump capacity, engine drive control is performed based on the first target engine speed N1 of 2100 rpm.

  In the state indicated by the bold solid line, 2100 rpm is set as the first target engine speed N1, 1800 rpm is set as the second target engine speed N2, and 1900 rpm is set as the third target engine speed N3. ing. Until the pump capacity D reaches 90% (D1) of the maximum pump capacity, engine drive control is performed at the second target engine speed N2 of 1800 rpm. When the pump capacity D becomes 90% (D1) or more of the maximum pump capacity, the pump capacity D is increased while the target engine speed N is increased. When the pump capacity D becomes about 92% (D3) or more of the maximum pump capacity, the engine drive control is performed based on the third target engine speed N3 of 1900 rpm.

  That is, if the pump flow rate when the first target engine speed N1 and the hydraulic pump 6 has the maximum pump capacity D2 is sufficient to supply the flow rate required for the hydraulic actuator to be operated, The third target engine speed N3, which is lower than the 1 target engine speed N1, is set as the upper limit value of the target engine speed.

  When a hydraulic actuator that is expected to generate a margin in the pump capacity D with respect to the maximum pump capacity is operated, it is possible to perform control as shown by a thick solid line. That is, the target engine speed N can be set to a lower speed within a range in which a pump flow rate required for the hydraulic actuator can be secured when the pump capacity D is the maximum pump capacity. As a result, the fuel consumption reduction effect can be increased without adversely affecting the operation of the hydraulic actuator.

  In the state indicated by the bold solid line, for example, if 1900 rpm is set as the third target engine speed N3, there is no problem with the operation of the hydraulic actuator. As indicated by the chain line, it is not necessary to increase the engine speed up to the first target engine speed N1.

  When engine drive control is performed along the dashed-dotted line extending from the thick solid line so that the engine speed can be increased to the first target engine speed N1, on the dashed-dotted line extending from the thick solid line The engine speed is also controlled in a region surrounded by a solid line in FIG. When the pump capacity D fluctuates in the area circled by the solid line, the engine speed also fluctuates according to the pump capacity fluctuation.

  On the other hand, in the present invention, since it is possible to perform engine drive control in a state surrounded by a dotted line on the thick solid line at the third target engine speed N3, even if the pump capacity D fluctuates, Since the third target engine speed N3 does not fluctuate, it is possible to prevent the engine speed from fluctuating.

Next, the engine drive control performed along the high speed control region F2 at the second target engine speed N2 and the above-described first pump capacity and drive control at the third target engine speed will be described with reference to FIG. To do.
As the drive control of the engine 2, until the pump displacement D of the hydraulic pump 6 reaches a preset first pump displacement D1 (see FIG. 7, point B being the first set position in FIG. 6), the high speed control region F2 is entered. Along with the control.

  When the pump capacity D of the hydraulic pump 6 becomes equal to or greater than the first pump capacity D1, as shown in FIG. 7, based on the correspondence between the preset pump capacity D and the target engine speed N. Therefore, the target engine speed N of the engine 2 is obtained.

  Then, as shown in FIG. 7, the pump capacity D of the hydraulic pump 6 driven by the engine 2 is equal to or greater than a preset third pump capacity D3 (point C as the third set position in FIG. 6). In some cases, as shown in FIG. 6, drive control of the engine 2 is performed along the high speed control region F3 at the third target engine speed N3.

Next, the control flow shown in FIG. 8 will be described.
In step S <b> 1 of FIG. 8, the controller 7 reads the command value 37 of the fuel dial 4. When the controller 7 reads the command value 37 of the fuel dial 4, the process proceeds to step S2.
In step S2, the controller 7 sets the first target engine speed N1 according to the read command value 37 of the fuel dial 4, and sets the high speed control region F1 based on the set first target engine speed N1. .

  It is explained that the first target engine speed N1 of the engine 2 is first set according to the read command value 37 of the fuel dial 4, but first, the high speed control region F1 is set, The first target engine speed N1 can also be set corresponding to the set high speed control region F1. Alternatively, the first target engine speed N1 and the high speed control region F1 can be set simultaneously according to the read command value 37 of the fuel dial 4.

As shown in FIG. 6, when the first target engine speed N1 and the high speed control region F1 are set, the process proceeds to step S3.
In step S3, the high-speed control region selection calculation unit 32 of the controller 7 shown in FIG. 2 is used to set the first target engine speed N1 and the low-speed region that is set in advance corresponding to the high-speed control region F1. (2) A high speed control region F2 corresponding to the target engine speed N2 and the target engine speed N2 is determined.
As the high-speed control region F2, for example, when the operation lever 11a (see FIG. 1) of the hydraulic excavator is operated, the operation speed is almost reduced by the load sensing control compared to the case where the control is performed in the high-speed control region F1. It can be set in advance as a high-speed control area that does not occur.

  That is, as shown in FIG. 11 in which Table 1 of FIG. 8 is enlarged, the second target engine speed N2 and the high speed control region are determined from the correspondence relationship between the first target engine speed N1 and the second target engine speed N2. F2 can be set. In addition, the numerical value of the rotation speed shown in Table 1 is an example, and can be appropriately set according to the construction machine or the like.

In this way, using Table 1, corresponding to each high-speed control region F1 that can be set with the fuel dial 4, the high-speed control region F2 that is on the rotation region side lower than the high-speed control region F1 is previously controlled at each high-speed control. It can be set as a high-speed control area corresponding to the area F1.
When the high speed control area F2 is determined by the controller 7, the process proceeds to step S4.

  In step S4, the operation information of the operation lever 11a is read, and the process proceeds to step S5. In step S5, based on the operation information of the operation lever 11a read in step S4, the correspondence between the operation information of the operation lever 11a shown in Table 2 (type / combination of hydraulic actuator to be operated) and the third target engine speed N3 A third target engine speed N3 is set based on the table. For example, when a plurality of operation levers 11a are operated, the third maximum flow rate required by the hydraulic actuator operated by the plurality of operation levers 11a can be supplied by the maximum pump capacity of the hydraulic pump 6. Set the target engine speed N3.

  More specifically, when traveling control is being performed independently by the operation of the operation lever 11a, the maximum target engine speed N3 can be selected as 1900 rpm based on Table2. When traveling control and bucket control are performed by operation with a plurality of operation levers 11a, 2500 rpm can be selected as the third target engine speed N3 based on Table2.

  In step S6, the upper limit value of the target engine speed N in Table 3 is set in correspondence with the third target engine speed N3 set using Table 2 in Step S5. For example, when traveling control is being performed solely by operation with the operation lever 11a, 1900 rpm can be selected as the third target engine speed N3 based on Table 2. Then, 1900 rpm is set as the upper limit value of the target engine speed N in Table 3.

  When traveling control and bucket control are being performed by operation with a plurality of operating levers 11a, the third target engine speed N3 of 2500 rpm can be selected in Table2. Then, 2500 rpm is set as the upper limit value of the target engine speed N in Table 3.

  When the second target engine speed N2 is set, the controller 7 injects the fuel so that the pump absorption torque and the engine output torque are matched on the high-speed control region F2, as indicated by a fine dotted line in FIG. Control of the device 3 is started.

  Next, control from step S8 or control from step S11 is performed. When drive control of the engine 2 is performed at the target engine speed N corresponding to the detected pump capacity D, control from step S8 to step S10 is performed. When the drive control of the engine 2 is performed at the target engine speed N corresponding to the detected engine output torque T, the control from step S11 to step S14 is performed.

First, the control step for obtaining the target engine speed corresponding to the detected pump displacement from step S8 to step S10 will be described.
In step S8, the pump capacity D of the hydraulic pump 6 detected by the swash plate angle sensor 39 is read. When the pump capacity D is read in step S8, the process moves to step S9. As described above, the pump capacity D can be obtained from the relationship between the pump discharge pressure P, the discharge capacity D (pump capacity D), and the engine output torque T (engine output torque T).

  The outline of the control for obtaining the target engine speed N corresponding to the detected pump displacement D in step S9 is as follows. That is, as shown in FIG. 7 which is an enlarged view of Table 3, when the engine drive control is controlled based on the second target engine speed N2, the pump capacity D of the hydraulic pump 6 is the predetermined first pump capacity. Until D1, the control based on the second target engine speed N2 is performed.

  When the detected pump capacity D of the hydraulic pump 6 is equal to or greater than the first pump capacity D1, it is detected based on the correspondence between the preset pump capacity D and the target engine speed N as shown in FIG. The target engine speed N corresponding to the pump capacity D is obtained. When the pump capacity Dn of the hydraulic pump 6 is detected, the drive control of the engine 2 is controlled so as to be the obtained target engine speed Nn.

  Thereafter, if it is detected that the pump capacity Dn is changed to the pump capacity Dn + 1, the target engine speed Nn + 1 corresponding to the pump capacity Dn + 1 is newly obtained from FIG. Then, drive control for the engine 2 is performed so that the newly obtained target engine speed Nn + 1 is obtained.

  Thus, when the target engine speed Nn is between the third target engine speed N3 and the second target engine speed N2, the target engine speed Nn corresponding to the detected pump capacity Dn is always obtained. Therefore, the drive of the engine 2 is always controlled with the obtained target engine speed Nn. In this control, the high-speed control region selection calculation unit 32 serves as second setting means for setting the target engine speed corresponding to the pump displacement detected by the detection means with the second target engine speed as a lower limit. It has a function.

  Further, in this control, the high-speed control region selection calculation unit 32 sets the upper limit value of the target engine speed corresponding to the pump displacement as the type of the hydraulic actuator operated by the operation lever or the operation lever operated by the operation lever. According to a combination of a plurality of hydraulic actuators, there is provided a function as a second setting means for setting a third target engine speed that is greater than or equal to the second target engine speed and less than or equal to the first target engine speed.

  When the detected pump displacement D becomes the third pump displacement D3, drive control of the engine 2 is performed along the high speed control region F3 at the third target engine speed N3. When the drive control of the engine 2 along the high speed control region F3 is being performed, the engine 2 along the high speed control region F3 is kept until the pump capacity D of the hydraulic pump 6 becomes smaller than the third pump capacity D3. Drive control continues to be performed. When the maximum torque line R is reached as shown in FIG. 6, engine control along the maximum torque line R is performed.

  Returning to FIG. 8, the description of the control step S9 will be continued. In step S9, when the target engine speed N corresponding to the detected pump capacity D is obtained based on the correspondence relationship between the preset pump capacity D and the target engine speed N shown in Table 3, the process proceeds to step S10.

In step S10, the value of the target engine speed N is corrected according to the change rate of the pump capacity of the hydraulic pump 6, the change rate of the pump discharge pressure, or the change rate of the engine output torque T. That is, when the rate of change, that is, the degree of increase is high, the target engine speed N can be corrected to the higher side. However, even if the target engine speed N is corrected to the higher side, the third target engine speed N3 is not exceeded.
In addition, although the control step which corrects the value of the target engine speed N is described as step S10, it can also be configured to skip the control of step S10.

Next, the control step for obtaining the target engine speed corresponding to the detected engine output torque in step S11 to step S14 will be described.
When the detection signal from the swash plate angle sensor 39 and the detection signal from the pump pressure sensor 38 are read in step S11, the process proceeds to step S12.
In step S12, the engine output torque T is calculated based on the pump displacement and pump pressure detection signals read in step S11. When the engine output torque T is calculated, the process moves to step S13.

  The outline of the control for obtaining the target engine speed N corresponding to the detected engine output torque T in step S13 is as follows. That is, as shown in FIG. 10 which is an enlarged view of Table 4 in FIG. 8, when the engine drive control is controlled based on the second target engine speed N2, the detected engine output torque T is a predetermined value. Until the first engine output torque T1 is reached, control based on the second target engine speed N2 is performed.

  When the detected engine output torque T is equal to or greater than the first engine output torque T1, it is detected based on the correspondence between the preset engine output torque T and the target engine speed N as shown in FIG. The target engine speed N corresponding to the engine output torque T is obtained. At this time, the drive control of the engine 2 is controlled so that the obtained target engine speed N is obtained.

  For example, when the engine output torque T detected at the present time is the engine output torque Tn, the target engine speed Nn is obtained as the target engine speed N. If it is detected that the engine output torque T has changed from the state of the engine output torque Tn to the state of the engine output torque Tn + 1, the target engine speed Nn corresponding to the engine output torque Tn + 1 is detected from FIG. +1 is newly required. Then, drive control for the engine 2 is performed so that the newly obtained target engine speed Nn + 1 is obtained.

  The upper limit value of the target engine speed N corresponding to the engine output torque T is preferably not set to the third target engine speed N3 that is smaller than the first target engine speed N1. When the engine output torque T increases, it is better to set the first target engine speed N1 that is higher than the third target engine speed N3 to the upper limit, even if the pump capacity is reduced. Many pump flow rates can be secured.

  Accordingly, since the pump capacity can be reduced by setting the first target engine speed N1 to the upper limit value, even if the engine output torque T is the same, work can be performed up to a larger pump pressure. In other words, the operator can secure a larger amount of work by controlling the engine so as to pass the maximum horsepower point (K1) shown in FIG. In other words, in a situation where the engine output torque T is high, the first target engine speed N1 is set as the upper limit value of the target engine speed N, so that the drive control of the engine that has passed the maximum horsepower point (K1) is performed. , Can secure more work.

  Returning to FIG. 8, the description of the control step S13 will be continued. In step S13, when the target engine speed N corresponding to the detected engine output torque T is obtained based on the correspondence relationship between the preset engine output torque T and the target engine speed N, the process proceeds to step S14.

In step S14, the value of the target engine speed N is corrected according to the rate of change of the pump capacity of the hydraulic pump 6, the rate of change of the pump discharge pressure, or the rate of change of the engine output torque T. That is, when the rate of change, that is, the degree of increase is high, the target engine speed N can be corrected to the target engine speed on the high speed side.
In addition, although the control step which corrects the value of the target engine speed N is described as step S14, the control of step S11 can be skipped.

  Of the target engine speed N corresponding to the detected pump capacity D and the target engine speed N corresponding to the detected engine output torque T, when using the target engine speed with the higher speed, Both the control in steps S8 to S10 and the control in steps S11 to S14 are performed. In this case, control of step S15 is performed following step S10 and step S14.

  When drive control of the engine 2 is performed with the target engine speed N corresponding to the detected pump capacity D, or when drive control of the engine 2 is performed with the target engine speed N corresponding to the detected engine output torque T Skips the control of step S15 and moves to step S16.

  In step S15, the target engine speed having the higher speed is selected from the target engine speed N corresponding to the detected pump capacity D and the target engine speed N corresponding to the detected engine output torque T. Is done. When the higher target engine speed is selected, the process proceeds to step S16.

In step S16, the high-speed control region selection calculation unit 32 outputs the high-speed control region selection calculation unit 32 shown in FIG. 2 to perform engine drive control using the target engine speed N. In this control, the high-speed control region selection calculation unit 32 has a function as a control unit that controls the fuel injection device so that the target engine speed obtained from the second setting unit is obtained.
When the control in step S16 is performed, the control returns to the control in step S1 and the control is repeatedly performed.

  As described above, in the present invention, the rotation of the engine can be controlled based on the second target engine speed N2 on the low speed range side, and the type of the hydraulic actuator to be operated or the plurality of hydraulic actuators to be operated With this combination, it is possible to perform engine drive control at the third target engine speed N3 as the upper limit value of the target engine speed. As described above, the engine drive control can be performed in a state in which the margin of the pump capacity is taken into consideration, the fuel efficiency can be improved, and the work speed required for operating the work implement can be sufficiently obtained.

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

  2 ... Engine, 3 ... Fuel injection device, 4 ... Fuel dial (command means), 6 ... Variable displacement hydraulic pump, 7 ... Controller, 8 ... Pump control device, 9 ... Control valve, 10 ... Hydraulic actuator, 11 ... Operating lever device, 11a ... Operating lever, 12 ... Servo cylinder, 17 ... LS valve, 32 ... High speed control area selection Calculation unit, 34... Type / combination determination unit of hydraulic actuator to be operated, 40... Pressure sensor, F1 to F3, Fa to Fc... High speed control region, B. ... 3rd set position, Nh ... Rated speed, K1 ... Maximum horsepower point, K4 ... Maximum torque point, R ... Maximum torque line, M ... Fuel consumption curve.

Claims (4)

A variable displacement hydraulic pump driven by an engine;
A plurality of hydraulic actuators driven by the discharge pressure oil from the hydraulic pump;
A plurality of control valves for controlling the pressure oil discharged from the hydraulic pump and supplying and discharging the hydraulic actuators respectively;
At least one operation lever for controlling the plurality of control valves;
Detecting means for detecting a pump capacity of the hydraulic pump;
A fuel injection device for controlling fuel supplied to the engine;
Command means for selecting and commanding one command value from command values that can be commanded variably;
A first target engine speed is set according to the command value commanded by the command means, and the second target is a speed lower than the first target engine speed based on the first target engine speed. First setting means for setting the engine speed;
Second setting means for setting a target engine speed corresponding to the pump capacity, with the second target engine speed as a lower limit;
Control means for controlling the fuel injection device so as to achieve the target engine speed determined from the second setting means;
With
The second setting means uses the type of the hydraulic actuator operated by the operation lever or a combination of the plurality of hydraulic actuators operated by the operation lever as an upper limit value of the target engine speed corresponding to the pump capacity. Accordingly, a third target engine speed that is greater than or equal to the second target engine speed and less than or equal to the first target engine speed is set.   The third target engine speed is a maximum required flow rate required by a type of the hydraulic actuator operated by the operation lever or a maximum required flow rate required by a combination of the plurality of hydraulic actuators operated by the operation lever. 2. The engine control apparatus according to claim 1, wherein the engine control apparatus is set in accordance with the above.   3. The engine control device according to claim 1, wherein the third target engine speed is set to the same speed as the second target engine speed. 4. It further comprises detection means for detecting engine output torque,
The second setting means includes
A target engine speed corresponding to a pump capacity when the second target engine speed is a lower limit and the third target engine speed is an upper limit;
A target engine speed corresponding to an engine output torque when the second target engine speed is a lower limit and the first target engine speed is an upper limit;
The engine control device according to any one of claims 1 to 3, wherein a higher target engine speed is set.

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