JP5576737B2 - Engine control device for hydraulic excavator - Google Patents

Description

  The present invention relates to an engine control device for a hydraulic excavator that performs engine drive control along a regulation characteristic (also referred to as a regulation line or a droop line) that defines a relationship between a target rotational speed and an engine output torque. The present invention relates to an engine control device for a hydraulic excavator that reduces the fuel consumption by reducing the engine speed without impairing the engine.

  When the engine torque curve that defines the relationship between the engine speed and the engine output torque is shown in the engine speed-engine output torque characteristic diagram, the regulation characteristic in the fuel injection amount adjustment region (regulation region) called the governor region is In general, each target rotational speed set by the fuel dial is represented by a single straight line having a constant slope inclined downward to the right.

  When there is no load, the engine speed is at the maximum speed Nmax. The engine control device increases the fuel injection amount as the load torque increases. By increasing the fuel injection amount, the engine output torque is increased to balance the load torque and the engine output torque. At this time, as the load torque increases, the engine speed decreases along the regulation characteristic line in the governor region, and when the load torque increases beyond the torque corresponding to the maximum fuel injection amount, the full load characteristic region is obtained. When the torque exceeds the maximum output torque of the full load characteristics, engine stall occurs.

  As described above, in the fuel injection device in the conventional engine control device, the regulation characteristic in the governor region is represented by a single straight line having a constant slope inclined downward to the right in the engine speed-engine output torque characteristic diagram. It has become.

  Here, in the hydraulic excavator, when the pump absorption torque (load torque) is equal to or lower than the rated torque of the engine, matching control between the engine output torque and the pump absorption torque is performed in accordance with the regulation characteristics in the engine torque curve. Yes.

  In matching control between engine output torque and pump absorption torque, in order to reduce fuel consumption without impairing operability, switching of pump capacity and target rotation speed command value (governor command value) according to engine output torque ) Has been proposed by the applicant of the present application (see Patent Document 1). Further, there has been proposed an engine speed control device (see Patent Document 2) that can suppress noise during no load and can secure a discharge amount from a hydraulic pump according to load torque during work.

In the invention described in Patent Document 1, when the engine output torque is low, the maximum pump capacity is increased and the engine drive control is performed based on the second target rotational speed that is lower than the first target rotational speed. When the engine output torque is high, the maximum pump displacement can be reduced and the engine drive can be controlled based on the first target rotational speed.
According to the present invention, the fuel consumption of the engine can be reduced, and the required work machine speed can be ensured.

In the invention described in Patent Document 2, in order to suppress noise during no load, the engine speed is decreased during no load. And in order to ensure the pump discharge amount which a working machine requires according to the load torque added to an engine at the time of work, a governor command value is changed continuously and engine speed is raised.

JP 2008-190506 A JP 2001-323827 A

  In the engine control apparatus disclosed in Patent Document 1, instead of starting the engine drive control from the first target rotational speed instructed by the fuel command dial, the second target rotational speed that is lower than the first target rotational speed is used. Engine drive control is started. When the load torque due to work is added and the engine output torque increases, the governor command value is increased and the target characteristic is increased in order to shift from the regulation characteristic corresponding to the second target rotational speed to the regulation characteristic corresponding to the first target rotational speed. The rotational speed is increased.

  And after shifting to the regulation characteristic according to the 1st target number of rotations, engine output torque is raised according to this regulation characteristic. However, when the work load is suddenly removed in the state where the control characteristic is controlled according to the first target rotational speed, the engine output torque decreases along the regulation characteristic according to the first target rotational speed. As a result, the engine speed increases rapidly. If this happens, the engine speed will overshoot, and the operation of the hydraulic actuator will accelerate more than necessary, or the operating piston of the hydraulic actuator will move more than necessary.

  In the engine speed control device in Patent Document 2, the governor command value is continuously changed according to the load torque applied to the engine from the state where the engine speed during no load is kept in a low speed range. The engine speed is increased. Then, by continuously changing the governor command value, the regulation characteristic corresponding to the governor command value is sequentially moved toward the regulation characteristic set by the fuel dial.

  However, when the engine drive control is performed with the regulation characteristic set with the fuel dial, if the work load suddenly falls off, the regulation characteristic set with the fuel dial follows the regulation characteristic set with the fuel dial. As the engine output torque decreases, the engine speed increases rapidly.

  In addition, when the governor command value is changed, if the engine output torque frequently varies according to the load variation, the governor command value is frequently varied to correspond to the variation of the engine output torque. Become.

  In addition, there is a time difference between the time when the engine output torque fluctuates, the time when the governor command value is commanded, and the time when fuel injection is performed. For this reason, if the governor command value repeatedly fluctuates to cope with frequent fluctuations in the engine output torque, even if fuel is injected into the engine in response to the fluctuation of the governor command value, the response may be delayed Wasteful fuel injection will be performed.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an engine control device for a hydraulic excavator that solves the above-described problems and can reduce fuel consumption by reducing the engine speed without impairing operability.

  The object of the present invention can be suitably achieved by the first to sixth aspects of the invention relating to the engine control device of a hydraulic excavator.

That is, in the engine control device for a hydraulic excavator according to the first invention of the present application, a variable displacement hydraulic pump driven by the engine, a plurality of hydraulic actuators driven by the discharge pressure oil from the hydraulic pump, and the engine of the engine Torque calculating means for calculating output torque, command means for instructing the first target rotational speed of the engine, a fuel injection device for controlling fuel supplied to the engine, and a rotational speed lower than the first target rotational speed Control means for controlling the fuel injection device based on a first regulation characteristic corresponding to the second target rotational speed,
The control means has a second regulation characteristic corresponding to the first target rotational speed, and a regulation characteristic in which an increase rate of the engine rotational speed with respect to a decrease in the engine output torque is smaller than the first regulation characteristic. The fuel injection device is controlled according to the value of the engine output torque, and when the engine output torque is equal to or greater than a first torque set value, the fuel injection device is controlled based on the second regulation characteristic. Main features.

  Further, in the second invention of the present application, the first regulation characteristic and the second regulation characteristic are set such that when the engine output torque is the second torque set value, the same engine speed is set. It is said.

  In the third invention of the present application, the plurality of hydraulic actuators include a turning motor, and the second torque set value is equal to or greater than an engine output torque when the turning motor is driven independently and at a constant speed. Is the main feature.

  Furthermore, the fourth feature of the present invention is characterized in that the control means controls the fuel injection device based on isochronous control when the engine output torque is equal to or less than the second torque set value.

  In the fifth invention of the present application, the control means further comprises correction means for gradually increasing the second target rotational speed to the first target rotational speed over a predetermined time, and the first regulation characteristic indicates the first The main feature is that the switching to the 2-regulation characteristic is performed through the correction means.

  Further, in the sixth invention of the present application, the plurality of hydraulic actuators include a swing motor and a boom cylinder, and the first torque set value drives the boom cylinder in a direction in which the boom is lowered and controls the swing motor. The main feature is that the value is larger than the engine output torque during driving.

  In the engine control device for a hydraulic excavator in the first invention of the present application, it is possible to prevent the engine speed from overshooting even when the work load is suddenly lost. Further, when the work load fluctuates, the engine is not controlled by changing the governor command value but based on the regulation characteristics. Therefore, stable engine control with reduced response delay is achieved, and wasteful fuel injection is suppressed and fuel consumption can be reduced.

  In the second invention of the present application, the fluctuation range of the engine speed when switching the regulation characteristics can be reduced. Therefore, the operability for the hydraulic actuator when switching the regulation characteristics is greatly improved.

  In the third invention of the present application, in an operation in which the engine output torque suddenly increases at the start of turning, and the engine output torque decreases rapidly after the turning start, as in the case of turning alone, the operation shifts to steady turning after starting the turning. It is possible to reduce the fluctuation range of the engine speed when the engine is operated. That is, the speed change at the start of turning can be suppressed, and two-stage acceleration and breathing can be prevented.

  In the fourth invention of the present application, since the target rotational speed in the standby state when the operation lever is in the neutral state can be lowered, the fuel consumption can be further reduced during idling.

  In the fifth invention of the present application, even if the load torque fluctuates when the regulation characteristic is switched, frequent change of the governor command value can be prevented between the regulation characteristics, and the engine speed fluctuates. Can be suppressed.

  In the sixth aspect of the present invention, the engine speed at the time of turning down can be reduced, and the fuel consumption can be reduced.

1 is a hydraulic circuit diagram according to an embodiment of the present invention. Example 1 It is a figure which shows an example of the relationship between an engine speed and an engine output torque. Example 1 It is a figure which shows an example of the relationship between an engine output torque and target rotational speed. Example 1 It is a block diagram of a controller. (Example) It is a control flowchart which shows a process of engine control. (Example) It is a figure which shows an example of the relationship between an engine speed and an engine output torque. Example 1 It is a figure which shows an example of the relationship between an engine speed and an engine output torque. Example 1 It is a figure which shows an example of the relationship between an engine speed and an engine output torque. Example 1 It is a figure which shows the example of the relationship between the engine speed concerning other embodiment, and an engine output torque. (Example 2) It is a figure which shows the example of the relationship between the engine speed concerning other embodiment, and an engine output torque. (Example 3) It is a figure which shows the example of the relationship between the engine speed concerning other embodiment, and an engine output torque. Example 4

  Preferred embodiments of the present invention will be specifically described below with reference to the accompanying drawings. The engine control device for a hydraulic excavator of the present invention can be suitably applied as a control device for controlling an engine mounted on the hydraulic excavator.

  In addition to the configuration described below, the engine control device of the hydraulic excavator of the present invention can adopt these configurations as long as the configuration can solve the problems of the present invention. 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 a hydraulic excavator according to an embodiment of the present invention. The hydraulic excavator includes a crawler-type lower traveling body and an upper swing body that can rotate 360 degrees. The hydraulic excavator includes a boom, an arm, and a bucket that are driven by hydraulic pressure, and can excavate and release earth and sand.

  The engine output torque in the engine 2 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 6 a of the hydraulic pump 6 is detected by the swash plate angle sensor 31 and input to the controller 7. The pump control device 8 controls the tilt angle of the swash plate 6 a of the hydraulic pump 6 by a control signal from the controller 7. As the tilt angle of the swash plate 6a changes, the pump capacity D (cc / rev) of the hydraulic pump 6 changes.

  The operation lever devices 12 to 14 have operation levers 12a to 14a, respectively. The operation levers 12a to 14a are operation members operated by an operator.

  By operating the operation levers 12a to 14a, the pilot pressure oil discharged from the pilot hydraulic pump 16 can be applied to the spools of the control valves 9 to 11 via the pipes indicated by broken lines. Then, the corresponding control valves 9 to 11 are respectively controlled according to the operation amount and the operation direction in each operation lever 12a to 14a. As a result, the flow rate of the pressure oil supplied to the hydraulic actuators 39 to 41 is controlled.

  The operation amount in each operation lever device 12-14 can be detected by pressure sensors 27a-27f. Each pressure sensor 27a to 27f is provided in each pipe connecting the operation lever devices 12 to 14 and the control valves 9 to 11, respectively.

  The detected pressures detected by the pressure sensors 27a to 27f are input to the controller 7 via harnesses indicated by a to f, respectively. The controller 7 can detect the operation states of the operation levers 12a to 14a based on the detected pressures detected by the input pressure sensors 27a to 27f.

  The pressure oil discharged from the hydraulic pump 6 is supplied to the control valves 9 to 11 through the oil passages 23a to 23c. Each control valve 9-11 is configured as a switching valve that can be switched to 6 port 3 position, and selectively supply the hydraulic oil output from each control valve 9-11 to the hydraulic actuators 39-41 can do. And the hydraulic actuator corresponding to each control valve 9-11 can be operated, respectively.

  The hydraulic actuator 39 is a hydraulic motor (swing motor) that turns the upper swing body relative to the lower traveling body. The hydraulic actuator 40 is an arm hydraulic cylinder (arm cylinder) that drives the arm. The hydraulic actuator 41 is a boom hydraulic cylinder (boom cylinder) that drives the boom. Although not shown, a bucket hydraulic cylinder, a left traveling hydraulic motor, a right traveling hydraulic motor, and the like are also provided.

  The operation lever device 12 can operate a hydraulic actuator 39 configured as a turning motor. The operation lever 13 can operate a hydraulic actuator 40 configured as an arm hydraulic cylinder. The operation lever device 14 can operate a hydraulic actuator 41 configured as a boom hydraulic cylinder. In addition, although not shown, an operation lever device that can operate a bucket hydraulic cylinder, a left traveling hydraulic motor, a right traveling hydraulic motor, and the like is also provided.

  When the operation levers 12a to 14a are operated from the neutral position, pilot pressures are output from the operation lever devices 12 to 14 in accordance with the operation direction and the operation amount of the operation levers 12a to 14a. The output pilot pressure is applied to one of the left and right pilot ports of each control valve 9-11. Thereby, each control valve 9-11 is switched from the (II) position which is a neutral position to the left and right (I) position or (III) position.

  Here, since the control valves 9 to 11 have the same configuration, description of the operation of the control valves 9 and 10 is omitted by describing the operation of the control valve 11 as a representative.

  When the control valve 11 is switched from the (II) position to the (III) position, the discharge pressure oil from the hydraulic pump 6 is supplied to the hydraulic actuator 41. At this time, pressure oil is supplied to the head side of the hydraulic actuator 41, and the piston of the hydraulic actuator 41 can be extended. Then, the pressure oil on the rod side of the hydraulic actuator 41 passes through the control valve 11 and is discharged to the tank 22.

  Similarly, when the control valve 11 is switched to the (I) position, the discharge pressure oil from the hydraulic pump 6 is supplied to the rod side of the hydraulic actuator 41, and the piston of the hydraulic actuator 41 can be contracted. At this time, the pressure oil on the head side of the hydraulic actuator 41 passes through the control valve 11 and is discharged to the tank 22.

  Incidentally, if none of the operation lever devices 12 to 14 is operated to the full stroke, none of the control valves 9 to 11 is switched to the full stroke position. Therefore, surplus oil that has not been used for the operation of the hydraulic actuator is returned to the tank 22 through the tank return circuit 26.

  When at least one of the operation lever devices 12 to 14 is operated to the full stroke, the corresponding control valve among the control valves 9 to 11 is switched to the full stroke position. In that case, there is no excess oil recirculated to the tank 22 through the tank return circuit 26.

  At this time, the differential pressure across the throttle 25 provided in the tank return circuit 26 can be detected by the differential pressure detection sensor 29. The front-rear differential pressure detected by the differential pressure detection sensor 29 is input to the controller 7 via the harness g. If the relationship between the differential pressure before and after the throttle 25 and the pump capacity of the hydraulic pump 6 is set in the controller 7 in advance as a pump control characteristic diagram, the controller 7 can detect the front and rear of the throttle 25 detected by the differential pressure detection sensor 29. From the differential pressure, the pump capacity of the hydraulic pump 6 can be calculated.

  Then, a command value for the calculated pump capacity is output to the pump control device 8. The tilt angle of the swash plate 6a is controlled by the pump control device 8 so that the pump displacement of the hydraulic pump 6 becomes the pump displacement corresponding to the command value.

  Here, when the operator operates the fuel dial 4 and selects one command value from command values that can be variably commanded, the target rotational speed corresponding to the selected command value can be set. That is, as shown in FIG. 2, the regulation characteristic Fa that matches the pump absorption torque and the engine output torque can be set according to the target rotational speed N1 (first target rotational speed) set by the fuel dial 4. . That is, the target rotational speed N1 is the engine rotational speed at the intersection K1 between the maximum torque line R in the full load region and the regulation characteristic Fa in the governor region.

The engine rotational speed Na ′ is the rotational speed at which the engine output torque matches the total value of the engine friction torque and the hydraulic system loss torque when there is no load when the target rotational speed is set to N1. When the target rotational speed N1 is set according to the operation of the fuel dial 4, a point at the engine rotational speed N1 on the full load region R of the engine torque curve and a point at no load (engine rotational speed Na ′) Will be set as the regulation characteristic Fa.

  When the regulation characteristic F1 is set in place of the regulation characteristic Fa as the regulation characteristic set according to the target rotational speed N1, the engine rotational speed N1 ′ is the rotational speed when there is no load. N2 ′, Nn ′, and Nb ′ are similarly no-load rotation speeds corresponding to the respective target rotation speeds.

  Further, the target rotational speed Na ′ may be set according to the operation of the fuel dial 4, and the regulation characteristic Fa may be set according to the target rotational speed Na ′. Also in this case, the first target rotational speed is the engine rotational speed N1 at the intersection of the full load region R and the regulation characteristic Fa.

  In the present embodiment, when the target rotational speed N1 is set by the fuel dial 4, and the engine output torque is low, the target rotational speed N2 (second target rotational speed) that is lower than the target rotational speed N1. The driving control of the engine 2 can be performed. By comprising in this way, fuel consumption can be reduced and a noise can be suppressed.

  Here, a description will be given of a case where the target rotational speed N2 that is lower than the target rotational speed N1 set by the fuel dial 4 is obtained and the drive control of the engine 2 is performed along the regulation characteristic F2 according to the target rotational speed N2. To do.

  In FIG. 2, the regulation characteristic according to the target rotational speed N1 is set as Fa. Further, the full load region defined by the maximum torque line R indicates 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. That is, the maximum horsepower point K1 is set as the intersection of the regulation characteristic Fa and the maximum torque line R when the target engine speed N1 is the rated engine speed.

  In the following explanation, the target rotational speed N1 set with the fuel dial 4 is described as the rated rotational speed of the engine. However, the target rotational speed N1 set with the fuel dial 4 is the rated rotational speed of the engine. An arbitrary target rotational speed less than the number can be set.

  Now, when any one of the operation levers 12a to 14a is operated and the drive control of the engine 2 is performed according to the regulation characteristic F2, the engine output torque is set to a predetermined torque set value T2 (A on the regulation characteristic F2). (Point) When the above is reached, movement from the regulation characteristic F2 to the regulation characteristic F1 side is performed. That is, by increasing the governor command value for controlling the fuel injection device 3, the engine 2 is driven along the line connecting the point A on the regulation characteristic F2 and the point B on the regulation characteristic Fa shown in FIG. Control is performed.

  That is, as shown in FIG. 3, when engine drive control is controlled based on the second target rotational speed N2, until the detected engine output torque T reaches a predetermined torque set value T2. Then, control based on the second target rotational speed N2 is performed.

  When the detected engine output torque T is equal to or greater than the torque set value T2, the detected engine output torque is determined based on the correspondence between the preset engine output torque T and the target rotational speed N as shown in FIG. The target rotational speed N corresponding to T is obtained. Then, the engine 2 is driven and controlled so as to achieve the determined target rotational speed N.

When the target rotational speed N is between the target rotational speed N2 and the target rotational speed N1 set by the fuel dial 4, the target rotational speed N corresponding to the detected engine output torque T is always obtained. Then, drive control of the engine 2 is performed so that the obtained target rotational speed N is obtained.

  For example, when the detected engine output torque T at the present time is the engine output torque Tn, the target rotational speed Nn is obtained as the target rotational speed N. If it is detected that the engine output torque T has changed from the engine output torque Tn state to the engine output torque Tb state, the target rotational speed Nb corresponding to the engine output torque Tb is newly obtained. Then, the drive control of the engine 2 is performed such that the newly obtained target rotational speed Nb is obtained.

  In the prior art, when the detected engine output torque T increases to a predetermined engine output torque T1, as shown in FIG. 2, the drive control of the engine 2 is performed according to the regulation characteristic F1 corresponding to the target rotational speed N1. Will be done. When the drive control of the engine 2 is performed according to the regulation characteristic F1, the drive control of the engine 2 continues to be performed according to the regulation characteristic F1 until the detected engine output torque T becomes equal to or less than the engine output torque T1. become. Then, by performing drive control of the engine 2 according to the regulation characteristic F1, the maximum horsepower point K1 that the engine 2 can output on the engine torque curve can be passed.

  In this embodiment, two or more regulation characteristics having different gradients are used. That is, as shown in FIG. 2, a regulation characteristic F2 having the same slope as the regulation characteristic F1 and a regulation characteristic Fa having a slope different from the regulation characteristic F2 are used. The regulation characteristic selection calculation unit 35 shown in FIG. 4 selects a required regulation characteristic according to the engine output torque from the regulation characteristics of two or more different gradients set in advance.

  As shown in FIG. 2, the regulation characteristic Fa is configured as a gradient larger than the gradients of the regulation characteristics F1 and F2. That is, the regulation characteristics F1 and F2 are configured as regulation characteristics with a gradual slope, and the regulation characteristics Fa are configured as regulation characteristics with a large slope.

  Here, a large gradient means that the increase rate of the engine speed with respect to a decrease in engine output torque is small, and a small gradient means that the increase rate of the engine speed with respect to a decrease in engine output torque is large.

  In FIG. 2, the regulation characteristic Fa having a large gradient has an angle α with the X axis of the horizontal axis in FIG. In addition, in the regulation characteristics F1 and F2 having a small gradient, the angle between the horizontal axis and the X axis in FIG. 2 is β. Therefore, in FIG. 2, the regulation characteristic Fa has a larger gradient than the regulation characteristics F1 and F2.

The regulation characteristic Fa and the regulation characteristic F2 intersect at the torque point C during steady turning (torque point C), and the regulation characteristic Fa has a characteristic that passes through the maximum horsepower point K1.
Steady turning means when the turning speed of the upper turning body is constant when the turning operation of the upper turning body is performed independently. Further, the torque during steady turning refers to the engine output torque during steady turning.

The steady turning torque point C is set as a matching point between the engine speed and the engine output torque T3 (second torque setting value) during steady turning. Further, the drive control of the engine 2 along the regulation characteristic Fa is performed from when the engine output torque T becomes larger than the point B. That is, point B is the engine drive control according to the regulation characteristic Fa when the engine output torque T becomes equal to or higher than the engine output torque Tb when the transition from the regulation characteristic F2 to the regulation characteristic F1 side is performed. Is the point in time.
As shown in FIG. 2, the engine output torque Tb (first torque set value) is larger than the engine output torque T3 (second torque set value).

  By providing the regulation characteristic Fa, it is possible to perform control along the regulation characteristic Fa from the point B in the middle of the transition to the regulation characteristic F1, without making a transition from the regulation characteristic F2 to the regulation characteristic F1. Further, even when the work load suddenly drops during the control along the regulation characteristic Fa, the engine output torque can be reduced along the regulation characteristic Fa.

  Moreover, the increase in engine speed is suppressed when the engine output torque is reduced along the regulation characteristic Fa, compared to when the engine output torque is reduced along the regulation characteristic F1. It becomes. That is, when the work load suddenly drops, for example, as shown in FIG. 6, when the engine output torque decreases along the regulation characteristic F1, the engine output torque follows the regulation characteristic F1 as indicated by the dotted line R1. Decreases and the engine speed increases. On the other hand, in this embodiment, as indicated by a two-dot chain line Ra in FIG. 6, the engine output torque decreases and the engine speed increases while following the regulation characteristic Fa.

  Therefore, the rotational speed difference between the engine speed at the two-dot chain line Ra in FIG. 6 and the engine speed at the dotted line R1 increases rapidly after the engine output torque starts to decrease. Thus, in the present invention, even if the engine output torque decreases, the engine speed does not increase rapidly. Therefore, in the present invention, it is possible to prevent the engine 2 from blowing up.

  That is, it is possible to prevent the engine speed from overshooting even when the work load is suddenly lost during the control according to the regulation characteristic Fa.

  Next, the control of the controller 7 will be described with reference to the block diagram of FIG. 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 pump torque calculation unit 34 in the controller 7 calculates the pump pressure discharged from the hydraulic pump 6 detected by the pump pressure sensor 28 and the swash plate angle command value calculation unit 33 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 34 calculates the pump torque (engine output torque) of 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.

The pump torque (engine output torque) calculated by the pump torque calculation unit 34 is calculated by using the pump pressure sensor instead of the detection value by the pump pressure sensor 28 and the command value calculated by the swash plate angle command value calculation unit 33. It is also possible to calculate using the detection value by 28 and the detection value of the swash plate angle sensor 31.
The method of calculating by the pump torque calculation unit 34 using the detected value of the pump pressure and the detected value of the swash plate angle sensor 31 is shown in FIG. The detected value is indicated by a dotted arrow.

The swash plate angle command value calculation unit 33 includes a detection value from the engine rotation sensor 30 and a tank return circuit 26.
And a detection signal from the front-rear differential pressure detection sensor 29 of the tank return circuit throttle that detects the front-rear differential pressure of the throttle 25 provided in Then, by using the relationship between the differential pressure across the throttle 25 and the pump capacity D of the hydraulic pump 6 set in advance as a pump control characteristic diagram, the hydraulic pump can be calculated from the differential pressure across the throttle 25 detected by the differential pressure detection sensor 29. A pump capacity D of 6 can also be obtained.

  The regulation characteristic selection calculation unit 35 selects a regulation characteristic according to the value of the engine output torque T from two or more different regulation characteristics set in advance. The selected regulation characteristic is commanded to engine 2 as regulation characteristic command value 36. That is, in the regulation characteristic selection calculation unit 35, when the engine output torque T becomes equal to or higher than the first torque set value Tb indicated by the point B during the engine drive control according to the regulation characteristic F2, the regulation characteristic F2 is used as the regulation characteristic. In order to shift to Fa, regulation characteristic Fa is selected and commanded to engine 2 as regulation characteristic command value 36. At this time, the regulation characteristic may be selected according to the operation state of the operation lever.

  The governor command value correction calculation unit 37 determines a governor command value 38 (target rotational speed) based on the fuel dial value and the regulation characteristic selected by the regulation characteristic selection calculation unit 35, and commands the engine as a governor command value 38. To do.

  The control flow shown in FIG. 5 will be described using the engine torque curves shown in FIGS. 2 and 6 as the regulation characteristics in the present embodiment. In this control flow, it is assumed that in the fuel dial 4, the rated engine speed is selected as the target engine speed N1, and the regulation characteristic Fa (second regulation characteristic) is set as shown in FIG. Assume that engine drive control is performed in accordance with a regulation characteristic F2 (first regulation characteristic) corresponding to a target revolution speed N2 that is a revolution speed lower than the target revolution speed N1.

In step S1 of FIG. 5, the controller 7 initializes the regulation characteristics, the governor command value 38, and the like. When initial values such as regulation characteristics and governor command value 38 are set, the process proceeds to step S2.
In step S2, the pump pressure sensor 28 is calculated using the relationship between 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, T = P · D / 200π. The engine output torque T is calculated using the discharge pressure P of the hydraulic pump 6 detected in step S1 and the tilt angle of the swash plate 6a of the hydraulic pump 6 detected by the swash plate angle sensor 31.

As the pump capacity D, the calculation result calculated by the swash plate angle command value calculation unit 33 can also be used. When the engine output torque T is calculated, the process proceeds to step S3.
In step S3, torque determination is performed. That is, it is determined whether or not the engine output torque T calculated in step S2 is equal to or greater than a preset first torque set value Tb. If it is determined in step S3 that the engine output torque T is greater than or equal to the preset first torque set value Tb, the process proceeds to step S4, and if it is determined that the engine output torque T is smaller than the first torque set value Tb, Move on to S5.

  In addition, when the engine output torque T becomes equal to or higher than the preset torque set value T2 before the control in step S3 is performed, control for shifting from the regulation characteristic F2 to the regulation characteristic Fa is performed. Explanation and illustration of steps are omitted.

In step S4, the regulation characteristic Fa is selected. That is, the engine drive control along the regulation characteristic Fa is performed so that the drive control from the point B in FIG. 2 toward the maximum horsepower point K1 is performed. When the control in step S4 is performed, the process proceeds to step S6.

  When the process proceeds from step S3 to step S5, the engine output torque T has not reached the first torque set value Tb, so the regulation characteristic F2 is selected. When the control in step S5 is performed, the process proceeds to step S6.

  In step S6, a regulation characteristic command value, which is a command value for the determined gradient of the regulation characteristic, and a governor command value are commanded to the engine 2. If control of step S6 is performed, it will return to step S2 and the control from step S2 will be repeated.

  If the explanation is added using FIG. 6 and the engine drive control is performed according to the regulation characteristic Fa, and the work load is suddenly removed, the regulation characteristic as shown by a two-dot chain line Ra. While decreasing the engine output torque T along Fa, the engine speed can be increased.

  On the other hand, when the engine load is suddenly removed while the engine is being controlled according to the regulation characteristic F1, the engine output torque is maintained according to the regulation characteristic F1, as indicated by the dotted line R1 in FIG. It will fall. As the engine output torque decreases, the engine speed increases rapidly, and becomes higher than in the present embodiment indicated by the two-dot chain line Ra in FIG.

  As described above, when the engine drive control is performed according to the regulation characteristic Fa, it is possible to prevent the engine speed from overshooting even when the work load is suddenly lost. .

  Further, as indicated by the dotted circle in FIG. 7, even when a load fluctuation occurs near the maximum horsepower point K1 during work, the engine drive control can be performed according to the regulation characteristic Fa. The drive control of the engine 2 can be stably performed even with respect to a load fluctuation in the vicinity of the horsepower point K1.

  Further, as shown in FIG. 8, the fluctuation range of the target rotational speed (indicated by an arrow in FIG. 8) when shifting from the regulation characteristic F2 having a gentle gradient to the regulation characteristic Fa having a large gradient is shown in Patent Document. As shown in FIG. 1, it can be configured to be smaller than the fluctuation range of the target rotational speed when shifting from the regulation characteristic F2 corresponding to the second target rotational speed N2 to the regulation characteristic F1 corresponding to the first target rotational speed N1.

  As described above, in this embodiment, since the fluctuation range of the target rotational speed when shifting between the two regulation characteristics can be reduced, it is possible to suppress the engine fluctuation width when switching the regulation characteristics. . Thereby, the operability for the hydraulic actuator when switching the regulation characteristics can be greatly improved.

  In addition to the control type hydraulic circuit shown in FIG. 1, the present invention can be suitably applied to a positive control type hydraulic circuit, a load sensing type hydraulic circuit, and an open center type hydraulic circuit. it can. Further, even an open center type hydraulic circuit, a negative control type hydraulic circuit or a positive control type hydraulic circuit in an open center type hydraulic circuit can be suitably applied.

  A second embodiment according to the present invention will be described with reference to FIG. In the second embodiment, the engine drive control below the steady turning torque point C (torque point C) is isochronous control. Other configurations are the same as those in the first embodiment. Therefore, the description of the same configuration as that in the first embodiment is omitted.

  As shown in FIG. 9, below the torque point C during steady turning, the target rotational speed can be set constant as the target rotational speed Nc at the steady turning torque point C. Thereby, the idling rotation speed (standby rotation speed) when the operation levers 12a to 14a are all in the neutral position can be lowered. That is, the fuel consumption during idling can be reduced.

  A third embodiment according to the present invention will be described with reference to FIG. In the third embodiment, the governor command value for switching the regulation characteristic from the regulation characteristic F2 to the regulation characteristic Fa is changed with time. Other configurations are the same as those in the first embodiment. Therefore, the description of the same configuration as that in the first embodiment is omitted.

  As shown in FIG. 10, when switching the regulation characteristic from the regulation characteristic F2 to the regulation characteristic Fa, the switching control from the regulation characteristic F2 to the regulation characteristic Fa is smoothly performed by changing the governor command value with time. It can be carried out.

  As shown in FIG. 4, by providing the governor command value correction calculation unit 37 in the controller 7, the governor command value can be changed over time. The governor command value correction calculation unit 37 functions as a correction unit that gradually changes the governor command value for the fuel injection device over time. As this correction means, a configuration in which modulation is set for the command value, a configuration using a low-pass filter, or the like can be employed.

  By configuring the governor command value to change over time when switching regulation characteristics, frequent switching between regulation characteristics can be prevented even when load torque fluctuations occur when switching regulation characteristics. It is possible to prevent the engine rotation from fluctuating according to the fluctuation of the load torque.

A fourth embodiment according to the present invention will be described with reference to FIG. In the fourth embodiment, the first torque set value Tb (shown as point A in FIG. 11) is a matching point (shown as point D in FIG. 11) between the target rotational speed and engine output torque at the time of turning down. It is configured as a value larger than the torque at the time of downturning. Other configurations are the same as those in the first embodiment. Therefore, the description of the same configuration as that in the first embodiment is omitted.
Down turning refers to an operation including two operations, a turning operation and a boom lowering operation. The down-turning torque refers to engine output torque during down-turning.

  As shown in FIG. 11, by configuring the torque determination value Tb as a value larger than the down-turning torque, the target rotational speed during the down-turning can be set low, and the fuel consumption can be reduced. Can be planned.

The technical idea of the present invention can be applied to engine control for an engine mounted on 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 -11: control valve, 25: throttle, 29 ... (before and after the tank return circuit throttle) differential pressure detection sensor, 33 ... swash plate angle command value calculator, 34 ... pump torque calculation 35, regulation characteristic selection calculation section 36, regulation characteristic command value 37, governor command value correction calculation section 38, governor command value, F 1, F 2, Fa. .

Claims (6)

A variable displacement hydraulic pump driven by an engine;
A plurality of hydraulic actuators driven by the discharge pressure oil from the hydraulic pump;
Torque calculating means for calculating the engine output torque of the engine;
Command means for commanding the first target rotational speed of the engine;
A fuel injection device for controlling fuel supplied to the engine;
Control means for controlling the fuel injection device based on a first regulation characteristic corresponding to a second target rotational speed that is a rotational speed lower than the first target rotational speed;
The control means has a second regulation characteristic corresponding to the first target rotational speed, and a regulation characteristic in which an increase rate of the engine rotational speed with respect to a decrease in the engine output torque is smaller than the first regulation characteristic. The fuel injection device is controlled according to the value of the engine output torque, and when the engine output torque is equal to or greater than a first torque set value at the time of switching from the first regulation characteristic to the second regulation, the second An engine control device for a hydraulic excavator, wherein the fuel injection device is controlled based on a regulation characteristic.   2. The hydraulic excavator according to claim 1, wherein the first regulation characteristic and the second regulation characteristic are set to have the same engine speed when the engine output torque is a second torque set value. Engine control device. A variable displacement hydraulic pump driven by an engine;
A plurality of hydraulic actuators driven by the discharge pressure oil from the hydraulic pump;
Torque calculating means for calculating the engine output torque of the engine;
Command means for commanding the first target rotational speed of the engine;
A fuel injection device for controlling fuel supplied to the engine;
Control means for controlling the fuel injection device based on a first regulation characteristic corresponding to a second target rotational speed that is a rotational speed lower than the first target rotational speed;
The control means has a second regulation characteristic corresponding to the first target rotational speed, and a regulation characteristic in which an increase rate of the engine rotational speed with respect to a decrease in the engine output torque is smaller than the first regulation characteristic. ,
The plurality of hydraulic actuators include a turning motor,
The second torque setting value smaller than the first torque setting value at the time of switching from the first regulation characteristic to the second regulation characteristic is equal to or greater than the engine output torque when the swing motor is driven independently and at a constant speed. An engine control device for a hydraulic excavator , characterized by: A variable displacement hydraulic pump driven by an engine;
A plurality of hydraulic actuators driven by the discharge pressure oil from the hydraulic pump;
Torque calculating means for calculating the engine output torque of the engine;
Command means for commanding the first target rotational speed of the engine;
A fuel injection device for controlling fuel supplied to the engine;
Control means for controlling the fuel injection device based on a first regulation characteristic corresponding to a second target rotational speed that is a rotational speed lower than the first target rotational speed;
The control means has a second regulation characteristic corresponding to the first target rotational speed, and a regulation characteristic in which an increase rate of the engine rotational speed with respect to a decrease in the engine output torque is smaller than the first regulation characteristic. ,
The control means performs fuel injection based on isochronous control when the engine output torque is equal to or less than a second torque set value smaller than the first torque set value at the time of switching from the first regulation characteristic to the second regulation characteristic. An engine control device for a hydraulic excavator , characterized by controlling the device. The control means further includes correction means for gradually increasing the second target rotation speed over the predetermined time to the first target rotation speed,
The engine control device for a hydraulic excavator according to any one of claims 1 to 4, wherein switching from the first regulation characteristic to the second regulation characteristic is performed via the correction unit. A variable displacement hydraulic pump driven by an engine;
A plurality of hydraulic actuators driven by the discharge pressure oil from the hydraulic pump;
Torque calculating means for calculating the engine output torque of the engine;
Command means for commanding the first target rotational speed of the engine;
A fuel injection device for controlling fuel supplied to the engine;
Control means for controlling the fuel injection device based on a first regulation characteristic corresponding to a second target rotational speed that is a rotational speed lower than the first target rotational speed;
The control means has a second regulation characteristic corresponding to the first target rotational speed, and a regulation characteristic in which an increase rate of the engine rotational speed with respect to a decrease in the engine output torque is smaller than the first regulation characteristic. ,
The plurality of hydraulic actuators include a swing motor and a boom cylinder,
The first torque setting value at the time of switching from the first regulation characteristic to the second regulation characteristic is greater than the engine output torque when the boom cylinder is driven in the direction in which the boom is lowered and the swing motor is driven. A hydraulic excavator engine control device characterized by a large value.

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