JP2008190506A - Control device for engine and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an engine capable of improving fuel economy of an engine and when the maximum speed of a work machine is required, imparting the required maximum speed of the work machine without deterioration, and its control method. <P>SOLUTION: A first target rotational speed Nh and a high speed control region F1 are set according to a command value from a command means. A second target rotational speed N2 and a high speed control region F2 are set on a low rotation side based on the first target rotational speed Nh. During control in the high speed control region F2, the maximum pumping capacity of a hydraulic pump 6 is controlled to a high pumping capacity Hi. When a matching point of an engine load and engine output torque reaches a predetermined torque value lower than a torque value restricted by the maximum torque line, the target rotational speed is controlled to change from the second target rotational speed N2 to the first target rotational speed Nh, and the maximum pumping capacity of the hydraulic pump 6 is controlled to a low pumping capacity Lo. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

  In the working vehicle, when the engine load is equal to or lower than the rated torque of the engine, matching with the engine output torque is performed in the high-speed control region in the torque diagram. For example, a target rotational speed is set corresponding to the setting with the fuel dial, and a high speed control region corresponding to the set target rotational speed is determined. Alternatively, a high-speed control region is determined in accordance with the setting on the fuel dial, and a target engine speed is set in correspondence with the determined high-speed control region. Then, control for matching the engine load and the engine output torque is performed in the predetermined high-speed control region.

  In general, in order to increase the amount of work, many workers often set the target rotational speed to be the rated rotational speed of the engine or a rotational speed in the vicinity thereof. 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 can be improved. Can do.

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. Further, when the engine speed when the second work mode is selected is set as the value of the engine speed that is uniformly reduced with respect to the engine speed when the first work mode is selected, When 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.
Japanese Patent Laid-Open No. 10-273919

  In the present invention, in order to solve the above-described problems of the prior art, when the engine output torque is low, the maximum pump capacity of the hydraulic pump is set to the high pump capacity Hi, and the first target rotation set. When the engine is controlled based on the second target speed that is lower than the engine speed, and the engine is used with a high engine output torque, the maximum pump capacity of the hydraulic pump is set to a low pump capacity Lo. Provided is an engine control device and a control method therefor that can perform engine drive control by shifting to the first target rotational speed side. In particular, the engine control device can improve the fuel consumption of the engine, and can provide the required maximum speed of the work machine without reducing the maximum speed when the maximum speed of the work machine is required. And providing a control method thereof.

The object of the present invention can be achieved by the inventions described in claims 1 to 4.
That is, in the first invention of the present application, at least one variable displacement hydraulic pump driven by an engine, at least one hydraulic actuator driven by discharge pressure oil from the variable displacement hydraulic pump, and the variable displacement hydraulic pump A control valve for controlling the pressure oil discharged from the pump to supply and discharge the hydraulic actuator;
Command means for selecting and commanding one command value from command values that can be variably commanded, a first target rotational speed is set according to the command value commanded by the command means, and the set first target Setting means for setting a second target rotational speed that is lower than the first target rotational speed based on the rotational speed, and the maximum pump capacity of the variable displacement hydraulic pump are set to a low pump capacity Lo and a high pump capacity Lo. A pump limiter that switches between two stages with the pump capacity Hi of
During the engine drive control based on the second target rotational speed, the pump limiter is controlled to switch the maximum pump capacity of the variable displacement hydraulic pump to a high pump capacity Hi, and the engine output torque is maximized. When a predetermined torque value lower than the torque value on the torque line R is reached, the engine target speed is changed from the second target speed to the first target speed, and the pump limiter is controlled. The main feature is that the maximum pump capacity of the variable displacement hydraulic pump is switched to the low pump capacity Lo.

  In the second invention of the present application, in addition to the configuration of the first invention, the first target engine speed is set for a predetermined time after the target engine speed of the engine is changed from the second target engine speed to the first target engine speed. Furthermore, the main feature is a configuration that is prohibited from being changed.

In the third invention of the present application, the control method using the first invention is the most important feature.
Further, in the fourth invention of the present application, in addition to the configuration of the third invention, the first target engine speed is set for a predetermined time after the target engine speed of the engine is changed from the second target engine speed to the first target engine speed. The main feature is that it is prohibited to make further changes.

  In the engine control device and the control method using the control device according to the present invention, the engine is driven based on the second target rotational speed. Therefore, when the engine is driven based on the first target rotational speed. In comparison, the fuel efficiency of the engine can be greatly improved. Moreover, in controlling the pump capacity of the variable displacement hydraulic pump, the control is performed between the minimum pump capacity and the high pump capacity Hi rather than the control between the minimum pump capacity and the low pump capacity Lo. If you do, you can control using the range where the fuel efficiency of the engine is good.

  However, if the engine is driven based on the second target rotational speed, the maximum horsepower cannot be absorbed. Therefore, in the present invention, when engine drive control is performed based on the second target rotational speed, the engine output torque becomes a predetermined torque value lower than the torque value on the maximum torque line R in the torque diagram. In this case, the engine target speed is changed from the second target speed to the first target speed so that the variable displacement hydraulic pump can absorb the maximum horsepower of the engine.

  In addition, when the target engine speed is changed from the second target engine speed to the first target engine speed, the maximum hydraulic capacity of the variable displacement hydraulic pump is switched from the high pump capacity Hi to the low pump capacity Lo. . At this time, when the target engine speed is changed from the second target engine speed to the first target engine speed, if the maximum hydraulic capacity of the variable displacement hydraulic pump remains in the high pump capacity Hi, the variable capacity The discharge flow rate from the hydraulic pump increases, and the operating speed of the actuator increases.

  For this reason, by switching the maximum hydraulic capacity of the variable displacement hydraulic pump from the high pump displacement Hi state to the low pump displacement Lo, the increase in the flow rate discharged from the variable displacement hydraulic pump is suppressed, and the operation of the actuator The noticeable speed increase is suppressed.

  As described above, according to the present invention, the engine speed and the pump capacity of the variable displacement hydraulic pump can each be used with high efficiency. That is, the engine can be used by shifting to an area where the fuel efficiency is good, and the fuel consumption of the engine can be reduced.

  Further, the operating speed of the actuator does not make the operator feel uncomfortable even when compared with the case where the drive control of the engine is performed using the conventional first target rotational speed. In addition, when the engine drive control is performed based on the second target rotational speed, when the engine output torque reaches a predetermined torque value, the engine target rotational speed is changed from the second target rotational speed to the first target rotational speed. The engine speed is increased by changing the number. As a result, the variable displacement hydraulic pump can absorb the maximum horsepower of the engine.

  Since it can be configured in this manner, the same work performance as the conventional one can be exhibited in work that requires the maximum output of the engine in heavy excavation work or the like. In other words, in the range of the engine output torque that requires the maximum speed of the work implement, the work implement can be operated while performing engine drive control based on the first target rotational speed.

  The low pump capacity Lo is set as the same pump capacity as the maximum pump capacity of the variable capacity hydraulic pump that is conventionally used when engine drive control is performed based on the first target rotational speed. be able to. Therefore, the high pump capacity Hi can be set to a value larger than the maximum pump capacity of the conventional variable displacement hydraulic pump described above.

The static relational expression of (high pump capacity Hi) × second target rotational speed = (low pump capacity Lo) × first target rotational speed can be established.
By setting the high pump capacity Hi and the low pump capacity Lo in this manner, even if the engine drive control is performed at the second target speed, the engine is driven based on the conventional first target speed. The maximum working speed of the actuator equivalent to when the control is performed can be secured.

  The engine output torque when changing the target engine speed from the second target engine speed to the first target engine speed is set as a predetermined torque value lower than the torque value on the maximum torque line R in the torque diagram. I can keep it. As the predetermined torque value at this time, as a torque value that can secure a necessary torque when the engine speed is accelerated from the second target speed to the first target speed, It can be obtained by experiments or the like.

  Further, as a parameter for specifying the predetermined torque value at this time, the value of the torque can be used, the value of the pump capacity when the engine outputs the torque of the predetermined value, or the engine capacity at that time. The value of the rotational speed can also be used.

  Accordingly, the parameters that can be used to specify the predetermined torque value described above in the present invention include not only the torque value but also the pump displacement value and the engine speed value.

  Further, based on the first target rotational speed and the second target rotational speed, in the TN diagram of the engine (torque diagram composed of the engine output torque axis and the engine rotational speed axis), high-speed control corresponding to each of them is performed. Regions can be set, and engine drive control can be performed in each high-speed control region. Therefore, engine drive control in these high-speed control areas is also included in each control based on the first target speed and the second target speed in the present invention.

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

  Further, as the engine control device and the engine control method of the present invention, in addition to the shapes and configurations described below, if the shapes and configurations can solve the problems of the present invention, those shapes and configurations are used. It can be adopted. 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 and an engine control method 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 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 can be expanded and contracted.

  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 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 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.

  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.

  The oil passage 26b is provided with a lock valve 43 that prevents the boom from dropping naturally when the actuator 10 is a boom hydraulic cylinder. Depending on the configuration of the actuator 10, the lock valve 43 may not be provided. In FIG. 1, the lock valve 43 is illustrated in a simplified manner. However, when the actuator 10 extends, the check valve in the lock valve 43 is opened by the pressure oil output from the control valve 9 to the oil passage 26b. The pressure oil can flow into the bottom side of the actuator 10.

When the actuator 10 is contracted, the opening degree of the check valve is controlled according to a pilot pressure (not shown) from the operation lever device 11, and the pressure oil on the bottom side of the actuator 10 is supplied to the tank via the control valve 9. Can be discharged to 22.
The load pressure of the actuator 10 is taken out through the pilot oil passage 28, and the pump control device 8 is controlled according to the differential pressure between the taken-out load pressure and the discharge pressure of the hydraulic pump 6.

  The pump control device 8 includes a servo cylinder 12 that controls the tilt angle of the swash plate 6a, a load sensing valve 17 (hereinafter referred to as LS valve 17) that is controlled according to the load pressure of the actuator 10, and the servo piston 2. And a position switching valve 16. The servo cylinder 12 includes a servo piston 14 that acts on the swash plate 6a and a switching piston 13 that restricts the maximum operating position of the servo piston 14 in two stages.

  From the middle of the discharge oil passage 25, an oil passage 27a and an oil passage 27b branch off. The oil passage 27 a is disposed as a pilot pressure that acts on the LS valve 17 and an oil passage that supplies pressure oil to the LS valve 17. Further, the oil passage 27b is connected to the port 23d of the servo cylinder 12, and the servo piston 14 can be pressed in the direction of immersing into the servo cylinder 12 by the pressure oil from the oil passage 27b. By immersing the servo piston 14 in the servo cylinder 12, the tilt angle of the swash plate 6a can be increased.

  The servo piston 14 slides between a position where the tilt angle of the swash plate 6a is minimized and a position where the tilt angle is maximized by the differential pressure between the oil pressure in the oil passage 32 and the oil pressure from the oil passage 27b. Will do. The maximum tilt angle of the swash plate 6a, that is, the maximum pump capacity of the hydraulic pump 6, depends on whether the switching piston 13 is set at the A position 15a or the B position 15b. It can be adjusted in two stages: Hi and low pump capacity Lo.

  The state where the end face of the switching piston 13 on the left side in FIG. 1 is in contact with the servo cylinder 12 is A position 15a, and the end face of the large diameter portion of the switching piston 13 on the right side in FIG. The state in contact with the cylinder 12 is a B position 15b. The servo piston two-position switching valve 16 is configured as a two-position / four-port switching valve, and is switched to two positions (a) and (b) by a control signal from the controller 7.

  By switching the servo piston 2 position switching valve 16 to the position (a), the switching piston 13 can be switched to the A position 15a. At this time, the maximum pump capacity of the hydraulic pump 6 can be set to the high pump capacity Hi. . Further, by switching to the (b) position, the switching piston 13 can be switched to the B position 15b. At this time, the maximum pump capacity of the hydraulic pump 6 can be set to the low pump capacity Lo.

  That is, by switching the servo piston 2-position switching valve 16, the operating position of the servo piston 14 contacting the switching piston 13 can be switched in two stages. The A position 15a defining the high pump capacity Hi and the B position 15b defining the low pump capacity Lo can be obtained by mechanically contacting the switching piston 13 within the servo cylinder 12. Is in position.

  Therefore, the high pump capacity Hi and the low pump capacity Lo that define the maximum pump capacity of the hydraulic pump 6 can be set as fixed pump capacity that does not vary. Accordingly, it is possible to prevent the high pump capacity Hi and the low pump capacity Lo from fluctuating and becoming unstable.

  Thus, the maximum tilt angle of the swash plate 6a in the hydraulic pump 6 can be regulated in two stages by switching the servo piston 2-position switching valve 16. Therefore, the servo piston 2-position switching valve 16 functions as a pump limiter that regulates the maximum pump capacity of the hydraulic pump 6.

  The LS valve 17 is configured as a two-position / three-port switching valve, and can be switched between a position where the oil passage 32 is connected to the tank 22 and a position where the oil passage 32 is connected to the oil passage 27a. The oil passage 32 is connected to the port 23c of the servo cylinder 12, and the oil passage 27a communicates with the discharge oil passage 25. Switching to the position where the oil passage 32 and the oil passage 27a are connected is performed by a differential pressure between the pump pressure of the oil passage 27a and the load pressure of the pilot oil passage 28. Further, switching to the position where the oil passage 32 is connected to the tank 22 is effected by the load pressure of the actuator 10 by the pilot oil passage 28 and the pressing force of the spring 24. The pressing force of the spring 24 is adjusted according to the movement of the interlocking member 18 that moves in conjunction with the sliding of the servo piston 14, and position feedback control is performed.

  The LS valve 17 is switched to a position where the discharge pressure of the hydraulic pump 6 acting on one end, the load pressure of the actuator 10 acting on the other end, and the urging force of the spring 24 via the interlocking member 18 are balanced. Become.

  Thus, the LS valve 17 is controlled according to the differential pressure between the load pressure of the actuator 10 and the discharge pressure of the hydraulic pump 6, and the servo cylinder 12 can be controlled by controlling the LS valve 17. Further, the swash plate angle of the hydraulic pump 6 can be controlled by controlling the servo cylinder 12. Therefore, the hydraulic pump 6 can be controlled according to the differential pressure between the load pressure of the actuator 10 and the discharge pressure of the hydraulic pump 6.

  By operating the fuel dial 4 as a command means, the operator can select one command value from command values that can be commanded variably with the fuel dial 4, and the target rotational speed corresponding to the selected command value. Can be set. 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.

  As shown in FIG. 2, when the target rotational speed Nb (N'b), which is the first target rotational speed, is set according to the operation of the fuel dial 4, a high speed corresponding to the target rotational speed Nb (N'b) is set. The control area Fb is selected. At this time, the target engine speed is the engine speed Nb (N'b).

  Note that the target engine speed N′b is the sum of the engine friction torque at no load and the hydraulic system loss torque and the engine output torque when the target engine speed Nb is controlled to the engine speed Nb. It will be determined as a matching point. 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 target rotational speed Nb. However, it is also possible to make the target rotational speed N′b coincide with the target rotational speed Nb. The number N′b can also be configured to be brought to the lower rotation side than the target rotation number Nb. In the following description, a rotational speed N′c with a dash is described, for example, as a target rotational speed Nc (N′c), but the rotational speed N′c with a dash is based on the above description. Is.

  Here, 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), the region for high-speed control is as follows. The high speed control region Fc on the low rotation region side is set. The target rotational speed Nc (N'c) set at this time becomes the first target rotational speed.

  Thus, by setting the command value with the fuel dial 4, the target rotational speed corresponding to the selected command value can be set. Then, one high-speed control area can be set corresponding to the set target rotational speed. That is, by selecting the fuel dial 4, for example, as shown in FIG. 2, a plurality of high-speed control regions Fb on the low-rotation region side from the high-speed control region Fa passing through the rated point K1 and the high-speed control region Fa, An arbitrary high-speed control area or an arbitrary high-speed control area in the middle of these high-speed control areas can be set from Fc,.

  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 target engine speed Nh (N'h), which is the maximum target engine speed of the engine, is set corresponding to the command value of the fuel dial 4, and the rated point K1 corresponding to the target engine speed Nh (N'h). A case where a high-speed control region F1 passing through is set will be described as an example. That is, the case where the target rotational speed Nh (N′h) is set as the first target rotational speed will be described. At this time, the control flow for moving on the high-speed control region F1 while matching the engine load and the engine output torque is illustrated in the control flow diagram and FIG. 5 mainly referring to FIGS. The description will be made with reference to the block diagram of the controller No. 6.

  In the following, in accordance with the command value of the fuel dial 4, the maximum target speed Nh (N'h) as the engine speed and the high speed control region F1 passing through the rated point K1 are set as the first target speed. However, the present invention is not limited to the case where the high-speed control region F1 passing through the rated point K1 is set. For example, even if an arbitrary high-speed control region is set from among a plurality of high-speed control regions Fb, Fc,... In FIG. The present invention can be suitably applied to each set high-speed control area.

  FIG. 3 shows a state when the engine output torque increases, and FIG. 4 shows a state when the engine output torque decreases. FIG. 5 shows a control flow. Further, the controller 7 is shown in FIG.

In step 1 of FIG. 5, the controller 7 reads the command value of the fuel dial 4. When the controller 7 reads the command value of the fuel dial 4, the process proceeds to step 2.
In step 2, the controller 7 sets the target rotational speed Nh (N'h) of the engine 2 as the first target rotational speed in accordance with the read command value of the fuel dial 4, and sets the target rotational speed Nh (N ' The high-speed control area F1 is set based on h).

  It is explained that the target rotational speed Nh (N'h) of the engine 2 is first set according to the read command value of the fuel dial 4, but first, the high-speed control region F1 is set. Thus, the target rotational speed Nh (N'h) can be set in correspondence with the set high-speed control area F1. Alternatively, the target rotational speed Nh (N'h) and the high-speed control region F1 can be simultaneously set according to the read command value of the fuel dial 4.

As shown in FIG. 3, when the target rotational speed Nh (N'h) as the first target rotational speed and the high-speed control region F1 are set, the routine proceeds to step 3.
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.

  In step 3, the controller 7 uses the setting means to set the target rotational speed N2 as the second target rotational speed on the low rotational speed side that is preset in correspondence with the first target rotational speed and the high-speed control region F1. (N'2), a high-speed control region F2 corresponding to the target rotational speed N2 (N'2) is determined. Further, the servo piston 2-position switching valve 16 which is a pump limiter is controlled to set the maximum pump capacity of the hydraulic pump 6 to the high pump capacity Hi.

  As the high-speed control region F2, for example, when operating the working machine lever 11a of the hydraulic excavator, the operation speed is hardly reduced by the load sensing control even when compared with the case of controlling in the high-speed control region F1. It can be set in advance as an area for high-speed control.

  If these conditions are satisfied, a high-speed control region F2 can be set for each high-speed control region F1 corresponding to each command value that can be set by the fuel dial 4. Further, the second target rotational speed N2 corresponding to the high speed control area F2 can be set to be, for example, 10% lower than the first target rotational speed Nh corresponding to the high speed control area F1. The case where the second target rotational speed is set to be 10% lower than the first target rotational speed Nh has been described as an example. However, the numerical values given here are merely examples, and the present invention includes these numerical values. It is not limited.

  In this way, corresponding to each high-speed control region F1 that can be set by the fuel dial 4, the high-speed control region F2 that is on the lower rotation region side than the high-speed control region F1 is preliminarily assigned to each high-speed control region. It can be set as a high-speed control area corresponding to F1.

The low pump capacity Lo or the high pump capacity Hi, which is the maximum pump capacity of the hydraulic pump 6 regulated by the servo piston 2-position switching valve 16, can be determined as follows.
That is, the discharge flow rate of the hydraulic pump 6 when the engine speed is the first target speed with the low pump capacity Lo, and the hydraulic pump when the engine speed is the second target speed with the high pump capacity Hi The low pump capacity Lo and the high pump capacity Hi can be determined as satisfying the condition that the discharge flow rate of 6 is substantially equal to the discharge flow rate. Expressed by the equation, a static relational expression of (high pump capacity Hi) × second target rotational speed = (low pump capacity Lo) × first target rotational speed can be established. .

That is, the low pump capacity Lo is set as the same pump capacity as the maximum pump capacity of the variable displacement hydraulic pump that is conventionally used when engine drive control is performed based on the first target rotational speed. I can keep it. The high pump capacity Hi can be set to a value larger than the maximum pump capacity of the conventional variable displacement hydraulic pump described above. When the high-speed control region F2 is determined by the controller 7 and the pump capacity of the hydraulic pump 6 can be increased to the maximum capacity Hi state, the process proceeds to step 4.
In step 4, when the operation lever 11a is operated, as shown by a fine dotted line in FIG. 3, the controller 7 performs fuel injection so that matching between the engine load and the engine output torque is performed on the high-speed control region F2. The device 3 is controlled.

  The operating state of the operating lever 11a can be detected by detecting the pressure fluctuation of the pressure oil in the operating lever device 11 with the pressure sensor 23, but the pressure fluctuation of each pilot pressure acting on the control valve 9 is It can also be detected by detecting with a sensor. It can also be detected by electrically detecting the operation amount and operation direction of the operation lever 11a.

As described above, by using various detection means capable of detecting the operation amount and the operation direction of the operation lever 11a, the operation state of the operation lever 11a can be detected.
When the operator operates the operation lever 11a to start the control for increasing the work implement speed of the hydraulic excavator, the process proceeds to step 5.

  In step 5, it is determined whether or not the engine speed has increased to a predetermined value while increasing the engine speed toward the second target speed N2. When attention is paid to the engine output torque, it is determined in step 5 whether or not the engine output torque has become a predetermined torque value lower than the torque value on the maximum torque line R on the high-speed control region F2. .

  As the predetermined torque value, when the engine speed is accelerated from the second target speed to the first target speed, a torque value that can secure a necessary torque is obtained in advance through experiments or the like. For example, it can be determined as a value of 90% of the torque value on the maximum torque line R. Then, whether or not the engine output torque has become a predetermined torque value lower than the torque value on the maximum torque line R is determined using the values of various parameters such as the pump capacity of the hydraulic pump 6 and the engine output torque. Can be detected.

  When the engine output torque reaches a predetermined torque value lower than the torque value on the maximum torque line R, the engine drive control is changed from the control in the high-speed control region F2 to the control in the high-speed control region F1.

  The control of the controller 7 performed at this time will be described with reference to FIG. In FIG. 6, the fuel dial command value calculation unit 42 in the controller 7 receives the command value 47 of the fuel dial 4 and the pump output from the pump capacity calculation unit 43 that calculates the pump capacity of the hydraulic pump 6. The capacity is entered. Further, a fuel dial command value calculation is performed using a detection signal from a differential pressure sensor 46 that detects a differential pressure between the pump pressure and the load pressure of the actuator 10 or a detection signal from a pump displacement sensor 49 (both not shown in FIG. 1). It can also be input to the unit 42.

  In FIG. 6, the detection signal output from the differential pressure sensor 46 to the fuel dial command value calculation unit 42, the detection signal from the hydraulic pump 6 to the pump displacement sensor 49, and the pump displacement sensor 49 to the fuel dial command value calculation unit 42. The detection signals to be output are shown using dotted lines. This is indicated by a dotted line in order to show that these detection means can be used as an alternative means of the pump capacity calculation unit 43 as described below. Further, the differential pressure sensor 46 and the pump displacement sensor 49 can be used independently.

  The pump capacity calculation unit 43 uses the pump pressure of the hydraulic pump 6 detected by the pump pressure sensor 48 and the engine torque 44 obtained from the engine torque diagram using, for example, the engine speed in the high-speed control region, This is input to the capacity calculation unit 43. The pump displacement calculator 33 calculates the pump displacement from these input values and outputs it to the fuel dial command value calculator 42. For example, the pump pressure sensor 48 can be arranged so that the pump pressure in the discharge oil passage 25 of FIG. 1 can be detected.

  Instead of using the pump displacement output from the pump displacement calculator 43, a detection signal from the pump displacement sensor 49 may be input to the fuel dial command value calculator 42. The pump capacity sensor 49 can be configured as a sensor or the like that detects the swash plate angle of the hydraulic pump 6.

  When the fuel dial command value calculation unit 42 determines that the following condition is satisfied, the new fuel dial command value 45 is used to shift control from the high speed control region F2 to the high speed control region F1. Set. Then, the set new fuel dial command value 45 is commanded to the fuel injection device 3 of the engine 2.

  A condition for performing control to shift from the high-speed control region F2 toward the high-speed control region F1 is when the engine output torque reaches a predetermined torque value. When this predetermined torque value is reached, the pump capacity of the hydraulic pump 6 when the engine output torque reaches the predetermined torque value, the engine speed at that time, the pump discharge pressure and the load pressure of the actuator 10 It can be detected using differential pressure or the like.

  Returning to the control flow of FIG. 5, the case where the value of the engine output torque is first used as a parameter for obtaining a predetermined torque value will be described.

  Based on the torque diagram stored in the controller 7, the controller 7 specifies the position on the high-speed control region F2 corresponding to the engine speed from the engine speed detected by the rotation sensor 20. Can do. Based on the specified position on the high speed control region F2, the value of the engine output torque at that time can be obtained.

  When the pump capacity of the hydraulic pump 6 is used as a parameter value, the relationship between the discharge pressure P, the discharge capacity D (that is, the pump capacity D) of the hydraulic pump 6 and the engine output torque T is T = P・ It can be expressed as D / 200π. From the equation of D = 200π · T / P using this relational expression, the pump capacity of the hydraulic pump 6 at that time can be obtained. Alternatively, the pump capacity of the hydraulic pump 6 can be obtained by mounting a swash plate angle sensor (not shown) on the hydraulic pump 6 and directly measuring the pump capacity of the hydraulic pump 6.

  It is determined that the matching point between the engine load and the engine output torque controlled to move along the high-speed control region F2 has become a predetermined torque value lower than the torque value on the maximum torque line R. If so, the process proceeds to step 6, and if it is determined that it has not been reached yet, the process proceeds to step 11.

  In step 6, the engine speed is increased from the second target speed to the first target speed, and control is performed to change the maximum pump capacity of the hydraulic pump 6 from a high pump capacity Hi to a low pump capacity Lo. .

  In FIG. 3, the state indicated by the fine dotted line arrow shows how the matching point is changed and moved from the high speed control area F2 to the high speed control area F1 based on the present invention. The state shown shows how the matching points that have been conventionally performed are moved on the high-speed control region F1.

When the operation lever 11a is returned from the deeply operated state, the swash plate angle of the hydraulic pump 6 decreases, and the controller 7 controls the fuel injection device 3 to reduce the fuel injection amount. As described above, in the high-speed control region F1, control is performed to reduce the engine output torque by reducing the pump capacity of the hydraulic pump 6 from the maximum state while matching the engine load and the engine output torque.
When the control in step 6 is performed, the process proceeds to step 7.

  In step 7, it is determined whether or not a predetermined time has elapsed since the control of shifting the target engine speed of the engine 2 from the second target engine speed to the first target engine speed. Until the predetermined time elapses, the controller 7 performs control so as not to shift from the high-speed control region F1 corresponding to the first target rotational speed to another high-speed control region.

If the shift to the high-speed control region on the high rotation region side is further performed before the predetermined time elapses, the shift to the high-speed control region on the high rotation region side will frequently occur. . If the shift to the high-speed control area on the high-rotation area side is frequently performed, the engine speed fluctuates, and the fluctuation of the engine sound may give the operator a sense of incongruity.
Therefore, in step 7, the control in step 7 is repeated until the predetermined time elapses, and after the predetermined time elapses, the process proceeds to step 8. As the predetermined time, an arbitrary time can be set as required.

  In step 8, when the controller 7 performs control to reduce the engine output torque while matching the engine load and the engine output torque in the high-speed control region F1 corresponding to the first target rotational speed, the hydraulic pump 6 Decreases from a predetermined pump capacity, for example, the maximum pump capacity Lo, and further, the pump capacity of the hydraulic pump 6 tends to decrease, the point on the high-speed control region F1 at this time is set to the set position C (ie, It can be set as a predetermined pump capacity.

  When the set position C is detected, a shift from the high speed control region F1 to the high speed control region F2 is performed. As the setting position C, in addition to setting the position when the pump capacity of the hydraulic pump 6 decreases from the maximum capacity and the pump capacity of the hydraulic pump 6 tends to decrease, the setting position C is as follows. Can be set. That is, a point on the high-speed control region F1 when the differential pressure between the discharge pressure of the hydraulic pump 6 and the load pressure of the actuator 10 exceeds the load sensing differential pressure set by the pump control device 8 is set. It can also be set as position C.

  Further, for example, the actuator 10 obtained when the control is performed in the high-speed control region F2 shifted down from the high-speed control region F1 and the operating speed of the actuator 10 obtained when the control is performed in the high-speed control region F1. The setting position C can also be set as a position where the operation speed can be obtained in a substantially inferior state.

  That is, when the engine output torque is decreased and the engine load and the engine output torque are matched and moved on the high speed control area F1, the reduction rate of the work machine speed of the actuator 10 and the high speed control area F2 A position where smooth connection can be achieved by experimentally determining what conditions can be used to achieve a smooth connection with the reduction rate of the work equipment speed of the actuator 10 when shifted. Can also be set as the setting position C.

As parameters for specifying the setting position C, various parameters used for obtaining a predetermined torque value that is a condition for shifting from the high-speed control region F2 to the high-speed control region F1 are used. it can.
Until the set position C is detected, the control in step 8 is repeated. When the set position C is detected, the process proceeds to step 9.

  In step 9, the controller 7 allows the maximum pump capacity of the hydraulic pump 6 to be increased to a high pump capacity Hi and decreases the engine speed so that the high-speed control area F1 is on the low speed area side. Control to shift to the high-speed control area F2 side is performed.

  In the high-speed control area F2, the control is performed as shown by the fine dotted arrows in FIG. 4, and the control is performed in the state of the conventional high-speed control area F1. In the case where it is broken, control as shown by a thick dotted arrow is performed.

  As a result, the engine load can be controlled to match the engine output torque by shifting from the high speed control region F1 to the high speed control region F2. Therefore, the engine 2 can be rotated on the low rotation region side, and the fuel efficiency of the engine 2 can be improved.

  Further, the position of the set position C can be changed according to the rate of change of the engine output torque T or the rate of change of the pump capacity of the hydraulic pump 6. That is, when the rate of decrease of these change rates is high, the position of the set position C can be set to the position where the engine output torque is high, and the shift to the high speed control area F2 can be performed early.

When the control in step 9 is performed, the process proceeds to step 10.
In step 10, it is determined whether or not a predetermined time has elapsed since the high-speed control region F 1 was shifted to the high-speed control region F 2 on the low rotation region side. Until the predetermined time elapses, the controller 7 performs control so as not to shift from the high-speed control area F2 to another high-speed control area.

If the shift to the high-speed control region on the high rotation speed side is further performed before the predetermined time elapses, the shift between the high-speed control regions frequently occurs. If shifting between different high-speed control areas is frequently performed, the engine speed fluctuates and the actuator operating speed is modulated.
For this reason, in step 10, the control in step 10 is repeated until the predetermined time elapses, and the process proceeds to step 11 after the predetermined time elapses. As the predetermined time, an arbitrary time can be set as required.

In step 11, the controller 7 confirms the first target rotational speed corresponding to the command value in the fuel dial 4, and proceeds to step 12 when the confirmation is completed.
In step 12, it is determined whether or not the value of the first target rotational speed corresponding to the command value in the fuel dial 4 has been changed to another target rotational speed value. When the value of the first target rotational speed is changed, the process returns to step 2 and the control after step 2 is performed. Further, when the value of the first target rotational speed has not been changed, the process returns to step 5 and the control after step 5 is sequentially performed.
In addition, since control of step 11 and step 12 is not necessarily a required control step, these steps can be abbreviate | omitted and a control flow can also be comprised.

  According to the present invention, the fuel efficiency of the engine is improved, and the region F1 for high speed control is set according to the first target rotational speed set by the operator corresponding to the command value in the fuel dial 4, and the first target set is set. A second target rotational speed and a high-speed control area F2 set in advance according to the rotational speed and the high-speed control area F1 are set, and the engine is determined based on the second target rotational speed or the high-speed control area F2. The drive control can be started. In addition, the maximum pump capacity of the hydraulic pump 6 can be set to the high pump capacity Hi during the control in the high-speed control area F2, and the maximum hydraulic pump 6 can be controlled during the control in the high-speed control area F1. The pump capacity can be set to the low pump capacity Lo.

  As a result, in an area where high engine output torque is not required, the engine speed can be controlled based on the second target speed on the low speed range side, and the fuel efficiency of the engine can be improved. In areas where high engine output torque is required, engine drive control can be performed by shifting to a high speed control area on the high rotation range side, and the work speed required for operating the work implement can be reduced. It can be obtained sufficiently.

  Also, when the engine output torque is decreased from the high output state of the engine, the engine drive control can be performed by shifting to the second target rotation speed (high speed control area F2) on the low rotation speed side. The fuel consumption can be improved.

  When changing from the high speed control area F2 to the high speed control area F1, the engine speed increases, but the maximum pump capacity of the hydraulic pump 6 is controlled from the high pump capacity Hi to the low pump capacity Lo. The discharge flow rate of the hydraulic pump 6 can be maintained at a substantially constant discharge flow rate. For this reason, the operating speed of the actuator does not increase or decrease with the change of the high-speed control region, and the responsiveness of the operation of the operator to the actuator can be maintained.

  Moreover, since the high pump capacity Hi and the low pump capacity Lo can be set as mechanically fixed pump capacity, the state where the hydraulic pump 6 is set to the maximum pump capacity can be stabilized.

  In the above-described embodiment, the description has been given using the hydraulic circuit including the load sensing control device as the hydraulic circuit. However, in the method of obtaining the capacity of the hydraulic pump 9 from the measured value of the engine speed and the engine torque diagram or the method of obtaining the pump capacity directly by the pump swash plate angle sensor, the hydraulic circuit as shown in FIG. 7 is opened. Even if it is configured as a center type, the same can be done. Even in this case, the pump control device 8 needs to be configured so that the swash plate angle of the variable displacement hydraulic pump 6 can be regulated in two stages, similarly to the pump control device described above.

  The technical idea of the present invention can be applied to a device or the like to which the technical idea of the present invention can be applied.

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 a torque diagram when reducing an engine output torque. (Example) It is a control flow figure concerning the present invention. (Example) It is a block diagram of a controller. (Example) It is a hydraulic circuit diagram comprised as an open center type. (Example)

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 ... Engine, 3 ... Fuel injection apparatus, 4 ... Fuel dial, 6 ... Hydraulic pump, 7 ... Controller, 8 ... Pump control apparatus, 9 ... Control valve, 11 ... Operating lever device, 12 ... servo cylinder, 13 ... switching piston, 14 ... servo piston, 16 ... servo piston 2-position switching valve, 17 ... LS valve, 18 ... Interlocking member, 23a to 23d ... port, F1 ... high speed control area, F2 ... high speed control area, C ... first setting position, Nh ... rated rotational speed (high speed control area) F1 target rotation speed), K1... Rated point, R... Maximum torque line, M.

Claims (4)

At least one variable displacement hydraulic pump driven by an engine;
At least one hydraulic actuator driven by pressure oil discharged from the variable displacement hydraulic pump;
A control valve for controlling the pressure oil discharged from the variable displacement hydraulic pump to supply and discharge the hydraulic actuator;
In an engine control device comprising:
Command means for selecting and commanding one command value from command values that can be commanded variably;
A first target rotational speed is set according to the command value commanded by the command means, and a second target rotational speed that is lower than the first target rotational speed based on the set first target rotational speed. Setting means for setting the number;
A pump limiter that switches the maximum pump capacity of the variable displacement hydraulic pump in two stages, a low pump capacity Lo and a high pump capacity Hi;
Have
During the engine drive control based on the second target rotational speed, the pump limiter is controlled to switch the maximum pump capacity of the variable displacement hydraulic pump to a high pump capacity Hi, and the engine output torque is a torque. When the predetermined torque value lower than the torque value on the maximum torque line R in the diagram is reached, the engine target speed is changed from the second target speed to the first target speed, and the pump An engine control device characterized by controlling a limiter to switch the maximum pump capacity of the variable displacement hydraulic pump to a low pump capacity Lo.   It is prohibited to further change the first target rotational speed for a predetermined time after the target rotational speed of the engine is changed from the second target rotational speed to the first target rotational speed. The engine control apparatus according to claim 1, wherein At least one variable displacement hydraulic pump driven by an engine;
At least one hydraulic actuator driven by pressure oil discharged from the variable displacement hydraulic pump;
A control valve for controlling the pressure oil discharged from the variable displacement hydraulic pump to supply and discharge the hydraulic actuator;
In the control method of the engine in the control device comprising:
Making it possible to switch the maximum pump capacity of the variable displacement hydraulic pump in two stages: a low pump capacity Lo and a high pump capacity Hi;
Selecting one command value from command values that can be commanded variably, and setting the first target rotational speed according to the selected command value;
Setting a second target speed that is lower than the first target speed based on the set first target speed;
During the drive control of the engine based on the second target rotational speed, the maximum pump capacity of the variable displacement hydraulic pump is switched to a high pump capacity Hi, and the engine output torque is on the maximum torque line R in the torque diagram. The engine target rotational speed is changed from the second target rotational speed to the first target rotational speed when a predetermined torque value lower than the torque value at is reached, and the maximum pump of the variable displacement hydraulic pump Switching capacity to low pump capacity Lo,
An engine control method.   The further change of the first target speed is prohibited during a predetermined time after the target speed of the engine is changed from the second target speed to the first target speed. Item 4. The engine control method according to Item 3.

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