JP4022494B2 - Engine lag down prevention device for construction machinery - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an engine lug-down prevention device for a construction machine that is provided in a construction machine such as a hydraulic excavator and suppresses a significant decrease in engine speed that occurs momentarily when the operating device is operated from a non-operating state.
[0002]
[Prior art]
Conventionally, as this type of technology, an engine, a variable displacement hydraulic pump that drives the engine, that is, a main pump, a tilt control actuator that controls the tilt angle of the main pump, and a maximum pump torque of the main pump are adjusted. Torque adjusting means, for example, means for controlling the tilt control actuator so as to keep the above-mentioned maximum pump torque constant regardless of the change in the discharge pressure of the main pump, an electromagnetic valve for making the maximum pump torque changeable, and the main pump There has been proposed an engine lag-down prevention device provided in a hydraulic construction machine having a hydraulic cylinder that is operated by pressure oil discharged from the cylinder, that is, a hydraulic actuator, and an operation lever device that operates the hydraulic actuator, that is, an operation device.
[0003]
This conventional engine lag-down prevention device is constituted by a processing program stored in the controller, and an input / output function and a calculation function of the controller, and the non-operation state of the operation device has passed a predetermined monitoring time. When a control signal for setting the maximum pump torque corresponding to the target engine speed up to that time to a predetermined low pump torque is output to the solenoid valve described above, and when the operating device is operated from a non-operating state, Torque control means for continuously maintaining the predetermined low pump torque during the hold time.
[0004]
In this prior art, when the operating device is suddenly operated from the non-operating state, the predetermined pump torque is maintained until the holding time elapses, and the rated pump torque, that is, the target engine speed is set after the holding time elapses. The maximum pump torque is changed accordingly. During the holding time, control is performed with a predetermined low pump torque so that the load on the engine is lightened, so engine lag down is suppressed, that is, a momentary drop in engine speed when a sudden load is applied to the engine Is suppressed, and adverse effects on workability and operability are suppressed, and it is possible to realize deterioration of fuel consumption, prevention of increase in black smoke, and the like (see, for example, Patent Document 1).
[0005]
Conventionally, the engine speed instruction means for instructing the target engine speed, and the engine speed can be controlled according to the target engine speed instructed by the engine speed instruction means, and the operating device is in a non-operating state. And an engine speed control means for controlling the engine speed to a predetermined low speed when a predetermined monitoring time has elapsed, and in the non-operating state after the above-mentioned predetermined monitoring time has elapsed. The low pump torque is controlled according to the predetermined low rotational speed, and when the operating device is operated from such a non-operating state, the low pump torque described above is held for a predetermined holding time. Technology for controlling the pump torque so that it becomes the original target maximum pump torque according to the target engine speed indicated by the engine speed instruction means after the holding time has elapsed. It has been proposed.
[0006]
This prior art contributes to suppression of engine lag down when the operating device is operated from a state where the engine speed is controlled to a predetermined low speed (for example, Patent Documents 2, 3, and 4). ).
[0007]
[Patent Document 1]
JP 2000-154803 A
(Paragraph numbers 0013, 0028-0053, FIGS. 1, 3)
[0008]
[Patent Document 2]
Japanese Patent Laid-Open No. 5-312082
[0009]
[Patent Document 3]
JP-A-6-307345
[0010]
[Patent Document 4]
JP-A-9-68169
[0011]
[Problems to be solved by the invention]
FIGS. 13 and 14 are diagrams for explaining the problems in the prior art disclosed in Patent Documents 1-4 described above, and FIG. 13A is a diagram showing desirable engine speed characteristics during a heavy load and a sudden load. FIG. 14 (b) is a diagram showing engine speed characteristics that cause problems at low load / sudden load, FIG. 14 (a) is a diagram showing desirable engine speed characteristics at low load / sudden load, FIG. FIG. 5 is a diagram showing engine speed characteristics that cause problems during heavy loads and sudden loads. In each of the above figures, the horizontal axis represents time, and the vertical axis represents engine speed.
[0012]
In the prior art disclosed in Patent Documents 1 to 4 described above, the engine load during a sudden load is maintained at a holding time T for maintaining a low pump torque according to a predetermined low speed after the operating device is operated from a non-operating state. When a relatively large value is set on the assumption of a heavy load, as shown in FIG. 13A, the engine speed characteristic during the period from the load occurrence A1 to the time A2 when the holding time T elapses. Further, the engine speed characteristic after the elapse of the holding time T can be set to the engine speed characteristic N1 indicated by the alternate long and short dash line, and a technique that does not take into consideration prevention of engine lag down, that is, the conventional technique disclosed in Patent Documents 1-4 described above Compared to the engine speed characteristic N2 indicated by the solid line, which is the engine speed characteristic in the technology prior to the technology, a characteristic in which the rotational speed is increased can be obtained. That is, it is possible to suppress an instantaneous decrease in the engine speed when a large load is applied to the engine during a sudden load.
[0013]
The same applies to the case where the holding time T is set relatively small on the assumption that the engine load becomes a small load at the time of sudden load. As shown in FIG. The rotational speed characteristic N1 can be a characteristic in which the rotational speed is increased as compared with the engine rotational speed characteristic N2 in the technology prior to the prior art disclosed in Patent Documents 1-4 described above. That is, it is possible to suppress an instantaneous decrease in the engine speed when a small load is applied to the engine during a sudden load.
[0014]
However, in the prior art disclosed in Patent Documents 1-4 described above, when it is assumed that the engine load during a sudden load becomes a large load, the load is actually small, or the engine load is small. A problem arises when the load is actually heavy even though it is assumed to be a load.
[0015]
For example, when it is assumed that the engine load is large but the load is actually small, the dead time T ′ is within the holding time T as shown in FIG. appear. The dead time T ′ is originally maintained at a predetermined low pump torque even though the hydraulic actuator can be driven at the rated pump torque, that is, at the maximum pump torque corresponding to the target engine speed (rated speed). Will be. As a result, the drive performance of the hydraulic actuator is degraded.
[0016]
On the other hand, when it is assumed that the engine load becomes a small load but the load is actually a large load, a shortage of time occurs and the holding time T shown in FIG. A relatively large engine lag down occurs even after the passage.
[0017]
That is, in the prior art disclosed in Patent Documents 1 to 4 described above, although engine lag down can be suppressed as such, highly accurate pump torque control can be performed as the holding time T is uniquely set. Realization was difficult.
[0018]
The present invention is made from the actual situation in the above-described prior art, and its purpose is to provide a more accurate operation when the operating device is operated from a non-operating state in which the engine speed is maintained at a predetermined low speed. An object of the present invention is to provide an engine lug-down prevention device for a construction machine that can realize high pump torque control.
[0019]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is driven by an engine, a main pump driven by the engine, torque adjusting means for adjusting the maximum pump torque of the main pump, and pressure oil discharged from the main pump. A hydraulic actuator, an operating device for operating the hydraulic actuator, an engine speed instruction means for instructing a target engine speed, and an engine speed corresponding to the target engine speed instructed by the engine speed instruction means. The engine is provided in a construction machine that is controllable and has engine speed control means for controlling the engine speed to a predetermined low speed when a non-operating state of the operating device has passed a predetermined monitoring time. Non-operation state in which the engine speed is controlled to the predetermined low speed by the engine speed control means Then, the torque adjusting means is controlled so as to obtain a low pump torque corresponding to the predetermined low rotational speed, and when the operating device is operated from the non-operating state, it continues for the predetermined holding time. Including a torque control means for controlling the torque adjusting means so as to obtain a low pump torque corresponding to a predetermined low rotational speed, and a significant reduction in the engine rotational speed that occurs when the operating device is operated from the non-operating state. In the engine lag down prevention device for a construction machine, the predetermined holding time is composed of a reference time forming a fixed time and a variable time that is a time following the reference time, and the magnitude of the engine load. And a calculating means for obtaining the variable time according to the above.
[0020]
According to the present invention configured as described above, when the operating device is operated in a non-operating state in which the engine speed is controlled to a predetermined low speed, the low pump corresponding to the predetermined low speed during the reference time The torque adjusting means is controlled by the torque control means so as to obtain torque.
[0021]
While the reference time is counted, a variable time corresponding to the load of the engine is obtained by the calculation means. For example, when the engine load is large, a relatively large variable time is obtained by the computing means, and when the engine load is small, a relatively small variable time is obtained by the computing means.
[0022]
During the variable time after the elapse of the reference time, the torque adjusting means is controlled by the torque control means so that the low pump torque corresponding to the predetermined low rotational speed is obtained as in the above-described reference time. That is, the pump torque is adjusted so as to be a low pump torque corresponding to a predetermined low rotational speed following the reference time.
[0023]
After the variable time has elapsed, the torque adjusting means is controlled so as to obtain the original maximum pump torque corresponding to the target engine speed indicated by the engine speed indicating means.
[0024]
Therefore, the holding time can be set to a time suitable for suppressing the engine lag down caused by the load applied to the engine, and there is no fear of generating a waste time at the time of a heavy load or insufficient time at the time of a light load, More accurate pump torque control can be realized when the operating device is operated from a non-operating state where the engine speed is maintained at a predetermined low speed.
[0025]
According to the present invention, there is provided a discharge pressure detecting means for detecting a discharge pressure of the main pump in the above invention, and the calculation means detects the discharge of the main pump detected by the discharge pressure detecting means within the reference time. First calculation means for obtaining the first target maximum pump torque from the pressure and the original PQ diagram corresponding to the target engine speed, and the first target maximum pump torque obtained by the first calculation means within the reference time The second calculating means for obtaining the second target maximum pump torque, which is the largest value, the relationship between the preset second target maximum pump torque and the engine lag down suppression time, and the second calculating means And third calculating means for determining the corresponding suppression time as the variable time based on the determined second target maximum pump torque.
[0026]
According to the present invention configured as described above, when the operating device is operated in a non-operating state where the engine speed is controlled to a predetermined low speed, the low speed corresponding to the predetermined low speed is set during the reference time. The torque adjusting means is controlled by the torque control means so as to obtain the pump torque.
[0027]
Also, during the reference time, the first target maximum pump torque is calculated from the main pump discharge pressure detected by the discharge pressure detection means and the original PQ diagram corresponding to the target engine speed during the reference time. Desired. Further, during this reference time, the largest value among the first target maximum pump torques determined by the second calculation means is determined as the second target maximum pump torque.
[0028]
Further, the third calculation means obtains a suppression time suitable for suppressing the engine lag down corresponding to the second target maximum pump torque, that is, a variable time corresponding to the magnitude of the engine load.
[0029]
During this suppression time, the torque adjusting means is controlled by the torque control means so that the pump torque is low according to a predetermined low rotational speed. That is, the pump torque is adjusted so as to be a low pump torque corresponding to a predetermined low rotational speed following the reference time.
[0030]
Therefore, the holding time, which is the sum of the suppression time required in relation to the discharge pressure of the main pump and the reference time, is a suitable time for suppressing engine lag down caused by the load applied to the engine, and highly accurate pump torque control Contribute to the realization of
[0031]
According to the present invention, there is provided the discharge pressure detecting means for detecting the discharge pressure of the main pump and the pilot pressure detecting means for detecting the pilot pressure of the operating device for operating the hydraulic actuator, in the above invention. A first calculation for obtaining a first target maximum pump torque from a discharge pressure of the main pump detected by the discharge pressure detection means within the reference time and an original PQ diagram corresponding to a target engine speed. And a second target maximum pump torque based on the relationship between the pilot pressure detected by the pilot pressure detecting means within the reference time, and the preset pilot pressure and the displacement of the main pump. Second calculating means to be calculated; first target maximum pump torque determined by the first calculating means; and second target maximum torque determined by the second calculating means. It is the largest value among the third calculation means for obtaining the third target maximum pump torque which is the minimum value of the pump torque, and the third target maximum pump torque obtained by the third calculation means within the reference time. Fourth calculation means for obtaining the fourth target maximum pump torque, the relationship between the preset fourth target maximum pump torque and the engine lag down suppression time, and the fourth target maximum pump torque obtained by the fourth calculation means 5th calculating means which calculates | requires the said suppression time as said variable time based on these.
[0032]
In the present invention configured as described above, when the operating device is operated in a non-operating state in which the engine speed is controlled to a predetermined low speed, the torque control means determines the time until the reference time elapses. The pump torque is kept low according to the low rotation speed.
[0033]
Further, during the reference time, the first calculation means obtains the first target maximum pump torque corresponding to the discharge pressure of the main pump detected by the discharge pressure detection means, and the second calculation means detects the pilot pressure. The displacement volume of the main pump corresponding to the pilot pressure detected by the means is obtained, and the second target maximum pump torque is obtained from the displacement volume and the discharge pressure of the main pump.
[0034]
Further, a third target maximum pump torque, which is the minimum value of the first target maximum pump torque and the second target maximum pump torque, is obtained by the third calculation means, and the third target maximum pump within the reference time is obtained by the fourth calculation means. A fourth target maximum pump torque, which is the largest value of the pump torque, is obtained.
[0035]
Then, the fifth calculation means obtains a time suitable for suppressing the engine lag down corresponding to the above-mentioned fourth target maximum pump torque, that is, a suppression time corresponding to the magnitude of the engine load.
[0036]
During this suppression time, the torque adjusting means is controlled by the torque control means so that the pump torque is low according to a predetermined low rotational speed.
[0037]
That is, the retention time, which is the sum of the suppression time required in relation to both the discharge pressure of the main pump and the pilot pressure associated with the operation of the operating device, and the reference time is used to suppress engine lag down caused by the load applied to the engine. It is a suitable time and contributes to the realization of highly accurate pump torque control.
[0038]
According to the present invention, in the above invention, the main pump comprises a variable displacement hydraulic pump, a tilt control actuator that controls the tilt angle of the variable displacement hydraulic pump, and a discharge pressure of the variable displacement hydraulic pump. A discharge pressure detecting means for detecting the tilt angle and a tilt angle detecting means for detecting the tilt angle of the variable displacement hydraulic pump, and the calculating means detects the discharge pressure detecting means within the reference time. First calculating means for obtaining a first target maximum pump torque from the discharge pressure of the variable displacement hydraulic pump and the tilt angle detected by the tilt angle detecting means, and the first calculation means within the reference time. Second calculation means for obtaining a second target maximum pump torque which is the largest value among the first target maximum pump torques obtained by one calculation means, and a second target maximum pump set in advance. And third calculating means for determining the corresponding suppression time as a variable time based on the relationship between the torque and the engine lag down suppression time and the second target maximum pump torque determined by the second calculation means. It is characterized by.
[0039]
According to the present invention configured as described above, the torque control means determines the predetermined time until the reference time elapses after the operating device is operated in the non-operating state where the engine speed is controlled to a predetermined low speed. The pump torque is kept low according to the low rotation speed.
[0040]
Further, during the reference time, the first target maximum is calculated from the discharge pressure of the variable displacement hydraulic pump detected by the discharge pressure detection means and the tilt angle detected by the tilt angle detection means by the first calculation means. Pump torque is required. Further, during this reference time, the largest value among the first target maximum pump torques determined by the second calculation means is determined as the second target maximum pump torque.
[0041]
Further, the third calculation means obtains a suppression time suitable for suppressing the engine lag down corresponding to the second target maximum pump torque, that is, a variable time corresponding to the magnitude of the engine load.
[0042]
During this suppression time, the torque adjusting means is controlled by the torque control means so that the pump torque is low according to a predetermined low rotational speed. That is, the pump torque is adjusted so as to be a low pump torque corresponding to a predetermined low rotational speed following the reference time.
[0043]
Therefore, the holding time, which is the sum of the suppression time required in relation to the discharge pressure and tilt angle of the variable displacement hydraulic pump and the reference time, is a suitable time for suppressing engine lag down caused by the load applied to the engine. Contributes to the realization of highly accurate pump torque control.
[0044]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment of an engine lag down prevention device for a construction machine according to the present invention will be described with reference to the drawings.
[0045]
FIG. 1 is a diagram showing a main configuration of a construction machine provided with the engine lug-down prevention device of the present invention.
[0046]
A first embodiment of an engine lug-down prevention device of the present invention is provided in a construction machine such as a hydraulic excavator. This hydraulic excavator is configured as a main part, as shown in FIG. For example, a variable displacement hydraulic pump driven by the motor, that is, a main pump 2, a pilot pump 3, and a tank 4 are provided.
[0047]
Further, a hydraulic actuator (not shown) such as a boom cylinder and an arm cylinder driven by pressure oil discharged from the main pump 2, an operating device 5 for operating the hydraulic actuator, and a tilt for controlling a tilt angle of the main pump 2. A control actuator 6 and torque adjusting means for adjusting the maximum pump torque of the main pump 2 are provided.
[0048]
This torque adjusting means corresponds to the torque control valve 7 that controls the tilt control actuator 6 so as to keep the maximum pump torque constant regardless of the change in the discharge pressure of the main pump 2 and the operation amount of the operating device 5. And a position control valve 8 for adjusting the maximum pump torque.
[0049]
Further, the tilt angle detecting means for detecting the tilt angle of the main pump 2, that is, the tilt sensor 9, the discharge pressure detecting means for detecting the discharge pressure of the main pump 2, that is, the discharge pressure sensor 10, and the operating device 5 A pilot pressure detecting means for detecting a pilot pressure output in accordance with the operation, that is, a pilot pressure sensor 11, and an engine speed indicating means for instructing a target speed of the engine 1, that is, a speed indicator 12 are provided. .
[0050]
In addition, the vehicle body control that inputs signals from the sensors 9 to 11 and the rotation speed indicator 12 and has a storage function and a calculation function including a logical judgment, and outputs a control signal according to the calculation result. A controller 13 and engine speed control means for outputting a signal for operating the fuel injection pump 14 for controlling the engine speed in response to a control signal output from the vehicle body controller 13, that is, an engine controller 15 are provided. Yes. The fuel injection pump 14 is also provided with a load detection device that detects a load applied to the engine 1 and outputs the load to the engine controller 15. The engine controller 15 can be controlled to an engine speed corresponding to the target engine speed indicated by the speed indicator 12, and the non-operating state of the operating device 5 by the vehicle body controller 13 is set for a predetermined monitoring time. When it is determined that the engine speed has elapsed, for example, when it is determined that 3 seconds have elapsed, the engine speed is controlled to a predetermined low speed n1.
[0051]
In addition, an electromagnetic valve 16 is provided which operates according to a control signal output from the vehicle body controller 13 and operates the spool 7a of the torque control valve 7 against the force of the spring 7b.
[0052]
2 to 5 are diagrams showing basic characteristics possessed by the construction machine shown in FIG. 1, that is, a hydraulic excavator. FIG. 2 is a pump discharge pressure-push-off volume characteristic (corresponding to PQ characteristics), and pump discharge pressure-pump. 3 is a diagram showing torque characteristics, FIG. 3 is a diagram showing PQ diagram movement characteristics, FIG. 4 is a diagram showing target engine speed-torque characteristics, and FIG. 5 is a diagram showing position control characteristics.
[0053]
As a basic characteristic of this hydraulic excavator, the relationship between the pump discharge pressure P and the displacement volume q shown in FIG. 2A, that is, the relationship between the pump discharge pressure P and the displacement flow rate Q corresponding to the displacement volume q. It has the characteristics shown in a certain PQ diagram 20. This PQ diagram 20 corresponds to the constant pump torque diagram 21. Further, as shown in FIG. 2B, the pump torque has a characteristic shown by a pump torque diagram 22 by PQ control which is a relationship of pump discharge pressure P-pump torque.
[0054]
As described above, if the discharge pressure of the main pump 2 is P, the displacement volume is q, the pump torque is Tp, and the mechanical efficiency is ηm,
Tp = (P × q) / (628 × ηm) (1)
It is known that
[0055]
Further, as a basic characteristic of the hydraulic excavator, as shown in FIG. 3, it has a PQ diagram moving characteristic. In FIG. 3, 23 is a PQ diagram corresponding to the maximum pump torque based on the target engine speed, and 24 is a PQ diagram corresponding to the pump torque by low torque control lower than the maximum pump torque described above. By performing torque control processing described later, it is possible to move between a PQ diagram 23 corresponding to the original maximum pump torque and a PQ diagram 24 corresponding to a low pump torque corresponding to a predetermined low rotational speed n1. It has become.
[0056]
Further, as basic characteristics of the hydraulic excavator, the characteristics shown in the engine maximum torque diagram 25 shown in the relationship of the target rotational speed-torque of the engine 1 shown in FIG. 4 and the engine maximum torque diagram 25 are not exceeded. The maximum pump torque curve to be suppressed has the characteristics shown in FIG. When the target rotational speed of the engine 1 is a predetermined low rotational speed n1, the maximum pump torque becomes a small value Tp1 on the maximum pump torque diagram 26. When the target rotational speed of the engine 1 becomes, for example, the rated rotational speed n2, It becomes the maximum value Tp2 on the maximum pump torque diagram 26.
[0057]
The PQ diagram when the maximum value Tp2 is reached on the maximum pump torque diagram 26 shown in FIG. 4 is, for example, the PQ diagram 23 of FIG. 3, and a small value Tp1 is shown on the maximum pump torque diagram 26 shown in FIG. The PQ diagram at this time is, for example, the PQ diagram 24 of FIG.
[0058]
In addition, as shown in FIG. 5, the hydraulic excavator has a position control characteristic based on the operation of the position control valve 8 accompanying the operation of the operating device 5 as shown in FIG. 5. FIG. 5 shows a position control diagram 27 when the discharge pressure P of the main pump 2 is P1.
[0059]
As shown in FIG. 1, since the position control valve 8 and the torque control valve 7 are connected in tandem, in this excavator, when the pump discharge pressure P is P1, the PQ diagram of FIG. The maximum pump torque is controlled according to the minimum value of 20 and the position control diagram 27.
[0060]
6 is a diagram showing engine control characteristics possessed by the construction machine shown in FIG. 1, that is, a hydraulic excavator, FIG. 7 is a diagram showing pilot pressure-displacement volume characteristics stored in the vehicle body controller, and FIG. 8 is a vehicle body controller. It is a figure which shows the torque MaxT (target maximum pump torque) memorize | stored in-engine lag-down suppression time characteristic.
[0061]
As shown in FIG. 6, this hydraulic excavator has an isochronous characteristic realized by, for example, electronic governor control as an engine control characteristic.
[0062]
Further, as shown in FIG. 7, the vehicle body controller 13 stores the relationship between the pilot pressure Pi corresponding to the operation amount of the operating device 5 and the displacement volume q of the main pump 2. As the pilot pressure Pi increases, the displacement q of the main pump 2 gradually increases.
[0063]
Further, the vehicle body controller 13 stores in advance the relationship between the target maximum pump torque and the engine lag down suppression time T2. This relationship is obtained in consideration of, for example, the engine load obtained empirically in an actual machine. When the target maximum pump torque corresponding to the engine load increases, it is considered necessary to suppress the engine lug down accordingly. The suppression time T2, which is time, is set so as to increase.
[0064]
Among the components described above, the side of the tilt sensor 9, the discharge pressure sensor 10, the pilot pressure sensor 11, the rotation speed indicator 12, the vehicle body controller 13, the electromagnetic valve 16, and the spring 7 b of the torque control valve 7. The engine lug of the present invention that suppresses a significant decrease in the engine speed that occurs momentarily when the operating device 5 is operated from a non-operating state by the pressure receiving chamber 7c that is disposed in the pressure receiving chamber 7c to which the pressure oil supplied from the electromagnetic valve 16 is guided. A first embodiment of the down prevention device is configured.
[0065]
Further, when the vehicle body controller 13, the electromagnetic valve 16, and the pressure receiving chamber 7 c of the torque control valve 7 are in the non-operating state of the operating device 5, a predetermined low rotation speed of the engine 1 is reached. The spool 7a of the torque control valve 7 is moved so as to have a low pump torque corresponding to the number n1, and when the operating device 5 is operated from the non-operating state described above, it continues for a predetermined holding time T. Torque control means for holding the spool 7a of the torque control valve 7 is configured so as to make the pump torque low according to the low rotational speed n1.
[0066]
In particular, the first embodiment includes a reference time T1 in which the predetermined holding time T described above forms a fixed time, and a suppression time T2 that is a time following the reference time T1, and the vehicle body controller 13 However, it has a calculation means for obtaining the suppression time T2 as a variable time according to the load of the engine 1.
[0067]
For example, this calculation means is an original corresponding to the discharge pressure P of the main pump 2 detected by the discharge pressure detection sensor 10 within the reference time T1 and the target engine speed indicated by the speed indicator 12. First calculation means for obtaining the first target maximum pump torque MaxT ′ from the PQ diagram, for example, the PQ diagram 23 of FIG. 3 described above, and the first target maximum obtained by the first calculation means within the reference time T1 described above. A relationship between the second calculation means for obtaining the second target maximum pump torque MaxT, which is the largest value of the pump torque MaxT ', and the preset second target maximum pump torque MaxT and the engine lag down suppression time T2, That is, based on the relationship shown in FIG. 8 described above and the second target maximum pump torque MaxT obtained by the second calculation means, the corresponding suppression time T2 is variable. And a third arithmetic means for finding a while.
[0068]
FIG. 9 is a flowchart showing a processing procedure in the vehicle body controller 13 including the first to third arithmetic means described above. The processing operation in the first embodiment of the present invention will be mainly described below with reference to the flowchart shown in FIG.
[0069]
The vehicle body controller 13 first inputs a signal from the pilot pressure sensor 11 as shown in step S1 of FIG. 9, and based on this signal, as shown in step S2, the controller device 5 continues for 3 seconds, for example. Determine whether it is in a non-operation state. When the controller device 5 is continuously in a non-operating state for 3 seconds, the process proceeds to step S3, and a process of setting the target engine speed of the engine 1 to a predetermined low engine speed n1 (AI rotation) is performed. That is, a signal corresponding to a predetermined low speed n1 is output from the vehicle body controller 13 to the engine controller 15, and in response to this, a control signal corresponding to the fuel injection pump 14 is output from the engine controller 15. 14 operates, and the rotational speed of the engine 1 is controlled to a predetermined low rotational speed n1.
[0070]
Next, the process proceeds to step S4, where the pump torque in the vehicle body controller 13 is set to a pump torque corresponding to a predetermined low rotational speed n1, that is, a small value Tp1 (AI rotation) of the low pump torque based on the relationship of FIG. Settings are made. Next, the process proceeds to step S5, where processing for setting the timer 1 provided in the vehicle body controller 13 to the reference time T1 is performed, and the process proceeds to step S6.
[0071]
In step S <b> 6, a control signal (OFF signal) for switching the electromagnetic valve 16 is output from the torque control means included in the vehicle body controller 13. As a result, the solenoid valve 16 is switched to the upper position as shown in FIG. 1 by the force of the spring 16 a, and the pilot pressure is supplied to the pressure receiving chamber 7 c of the torque control valve 7 via the solenoid valve 16. The combined force of the force due to the discharge pressure of the main pump 2 applied to the pressure receiving chamber 7d and the force due to the pressure in the pressure receiving chamber 7c is larger than the force of the spring 7b, and the spool 7a moves to the left in FIG. As a result, the pilot pressure is supplied to the pressure receiving chamber 6a of the tilt control actuator 6 via the position valve 8 and the torque control valve 7, and the force due to the pressure in the pressure receiving chamber 6a is greater than the force due to the pressure in the pressure receiving chamber 6b. The spool 6c of the tilt control actuator 6 moves to the right in FIG. 1, and the tilt angle of the main pump 2 changes in the direction of the arrow 30 and becomes the minimum. As a result, the pump torque becomes a small value Tp1 of the low pump torque corresponding to the aforementioned predetermined low rotational speed n1.
[0072]
Then, when the operating device 5 is suddenly operated to operate the hydraulic actuator (not shown) while the torque control means is controlling to the low value Tp1 of the low pump torque as described above, the determination in step S2 of FIG. No, the process proceeds to step S7.
[0073]
In this procedure S7, the vehicle body controller 13 performs a process of setting the rotational speed of the engine 1 to a target engine rotational speed indicated by the rotational speed indicator 12, for example, a rated rotational speed n2. However, a control signal corresponding to the target engine speed is not output to the engine controller 15 at this stage, for example.
[0074]
Next, the process proceeds to step S8, where it is determined whether or not the reference time T1 set by the timer 1 is greater than zero. Now, since the reference time T1 is set for the timer 1 in step S5 described above, the reference time T1 is greater than 0, and the process proceeds to step S9. In this procedure S9, the reference time T1 is counted.
[0075]
Next, the process proceeds to step S10, and a signal from the discharge pressure sensor 10 is input. Next, the procedure proceeds to step S11, and the first calculating means included in the vehicle body controller 13 performs a calculation for obtaining the first target maximum pump torque MaxT '. In this case, the original PQ diagram corresponding to the discharge pressure P of the main pump 2 detected by the discharge pressure sensor 10 and the target engine speed (rated speed n2) set in step S7, that is, the PQ of FIG. The corresponding displacement volume q is obtained from the diagram 23, and the first target maximum pump torque MaxT 'is obtained from the above-described equation (1).
[0076]
Next, the procedure proceeds to step S12, and the first target maximum pump torque MaxT 'obtained within the reference time T1 is compared with the second target maximum pump torque MaxT by the second calculation means included in the vehicle body controller 13. . If the first target maximum pump torque MaxT ′ obtained in step S11 is larger than that obtained so far, in step S13, the first target maximum pump torque MaxT ′ is set to the second target maximum pump torque MaxT. . That is, the processing contents of steps S12 and S13 are the calculation contents of the second calculation means.
[0077]
If the first target maximum pump torque MaxT ′ obtained by the first calculation means is smaller than the second target maximum pump torque MaxT obtained so far in the determination of the step S12, and the first corresponding in the step S13. After the process of setting the target maximum pump torque MaxT ′ to the second target maximum pump torque MaxT is finished, the process proceeds to step S14.
[0078]
In this step S14, the relationship between the second target maximum pump torque set in advance and the engine lag down suppression time T2 by the third calculation means included in the vehicle body controller 13, that is, the relationship shown in FIG. Based on the second target maximum pump torque MaxT obtained by the second computing means, a computation for obtaining the suppression time T2 is performed, and the suppression time T2 is set in the timer 2. Next, the procedure proceeds to step S15. In this procedure S15, as in the procedure S4 described above, the pump torque is set to a small value Tp1 (AI rotation) of the low pump torque shown in FIG. 4 corresponding to the predetermined low rotational speed n1.
[0079]
Next, the process proceeds to step S6, and as described above, a control signal (OFF signal) corresponding to the small value Tp1 of the low pump torque is output from the torque control means included in the vehicle body controller 13 to the electromagnetic valve 16. Accordingly, the spool 7a of the torque control valve 7 is positioned in the left direction in FIG. 1, the tilt angle of the main pump 2 is minimized, and the pump torque is maintained at the low value Tp1 of the low pump torque. .
[0080]
That is, a process of holding the low pump torque at a small value Tp1 is performed for the reference time T1 counted from when the operating device 5 is operated from the non-operating state.
[0081]
When the reference time T1 is timed and the timer 1 becomes 0, the above-described determination in step S8 is no and the process proceeds to step S16.
[0082]
In step S16, it is determined whether the suppression time T2 set by the timer 2 is greater than zero. Now, since the suppression time T2 is set for the timer 2 in step S14 described above, it is determined that the suppression time T2 is greater than 0, and the process proceeds to step S17. In this procedure S17, the suppression time T2 is counted.
[0083]
Next, the procedure proceeds to step S18, and the pump torque is set to a small value Tp1 (AI rotation) of the low pump torque corresponding to the predetermined low rotation speed n1, as in the above-described steps S4 and S15.
[0084]
Next, the process proceeds to step S6, and as described above, a control signal (OFF signal) corresponding to the small value Tp1 of the low pump torque is output from the torque control means included in the vehicle body controller 13 to the electromagnetic valve 16. As a result, the pump torque is held at the small value Tp1 of the low pump torque.
[0085]
That is, even after the reference time T1 has elapsed, the low pump torque is kept at a small value Tp1 until the suppression time T2 is continuously counted.
[0086]
When the suppression time T2 is timed and the timer 2 becomes 0, the determination in step S16 described above becomes no and the process proceeds to step S19.
[0087]
In this step S19, the maximum value shown in FIG. 4 is the pump torque corresponding to the engine speed set in step S7 described above, that is, the target engine speed (for example, the rated speed n2) indicated by the speed indicator 12. Tp2 is determined.
[0088]
Next, the process proceeds to step S6, and a control signal (ON signal) corresponding to the maximum value Tp2 of the pump torque is output from the torque control means included in the vehicle body controller 13 to the electromagnetic valve 16. As a result, the electromagnetic valve 16 is switched to the lower position in FIG. 1 against the force of the spring 16 a, and the pressure receiving chamber 7 c of the torque control valve 7 is in communication with the tank 4 via the electromagnetic valve 16. Therefore, in the torque control valve 7, the spool 7a moves in accordance with the magnitude relationship between the force due to the discharge pressure of the main pump 2 applied to the pressure receiving chamber 7d and the force of the spring 7b. For example, in this case, the force of the spring 7b is strong, and the spool 7a tends to move rightward in FIG. Accordingly, the pressure receiving chamber 6a of the tilt control actuator 6 communicates with the tank 4 via the torque control valve 7, the spool 6c moves to the left in FIG. 1, and the main pump 2 as shown by the arrow 31 in FIG. The tilt angle increases. The PQ diagram at this time is the PQ diagram 23 of FIG. That is, from the PQ diagram 24 corresponding to the small value Tp1 of the low pump torque to the PQ diagram 23 corresponding to the maximum value Tp2 which is the maximum pump torque according to the original target engine speed (rated speed n2). Moving.
[0089]
FIG. 10 is a graph showing engine speed characteristics at the time of heavy load / sudden load obtained in the first embodiment.
[0090]
Now, for example, the operating device 5 is not operated, and the pump torque is maintained at a small value Tp1 of the low pump torque corresponding to the predetermined low rotational speed n1, that is, a small value Tp1 corresponding to the PQ diagram 24 of FIG. It is assumed that a sudden operation in which a heavy load is applied to the engine 1 is performed from the state where the engine 1 is present. In the technique prior to the prior art disclosed in Patent Documents 1-4 described above, the change in the engine speed with the passage of time at this time is as indicated by the engine speed characteristic N2 indicated by the solid line in FIG.
[0091]
On the other hand, in the first embodiment of the present invention described above, for example, the pump torque is held at the low value Tp1 of the low pump torque for the reference time T1, the suppression time T2 is obtained during the reference time T1, and the reference time The original maximum pump according to the target engine speed (rated speed n2) is maintained after the elapse of T1 and is maintained at a small value Tp1 for the suppression time T2, and after the elapse of the suppression time T2, that is, after the elapse of the holding time T. Since the process of returning to torque is performed, the change in the engine speed can be changed to an engine speed characteristic N1 indicated by a one-dot chain line in FIG. In FIG. 10, reference numeral A1 indicates when a load is generated.
[0092]
The engine speed characteristic N1 indicated by the alternate long and short dash line in the first embodiment is set in advance in a holding time T on the assumption that a large load is applied to the engine 1 in the prior art disclosed in Patent Documents 1-4 described above. Is apparently similar to the engine speed characteristic N1 shown in FIG. 13 (a). However, in the first embodiment of the present invention, the holding time T includes a suppression time T2 that changes according to the load applied to the engine 1, that is, a variable time. Different from the technology shown.
[0093]
In the first embodiment of the present invention, the engine speed characteristic N1 indicated by the one-dot chain line in FIG. 10 can be secured at such a heavy load / sudden load. The holding time T can be set to an optimum value according to the time T, and during this holding time T, the low pump torque is kept at a small value Tp1 corresponding to the predetermined low rotational speed n1, so Engine lag down can be suppressed.
[0094]
Further, for example, it is assumed that a sudden operation in which a small load is applied to the engine 1 is performed from a state where the operating device 5 is not operated and the pump torque is maintained at a small value Tp1 of the low pump torque. In the technique prior to the prior art disclosed in Patent Documents 1-4 described above, the change in the engine speed with the passage of time at this time is represented by the engine speed characteristic N2 indicated by the solid line in FIG. It becomes like this.
[0095]
In contrast, in the first embodiment of the present invention, as described above, the low value Tp1 of the low pump torque is held for the reference time T1, and further held for the suppression time T2, and after the suppression time T2 has elapsed, Since returning to the maximum pump torque according to the target engine speed (rated speed n2), the change in the engine speed is obtained by the technique shown in Patent Document 1-4 shown in FIG. This is similar to the engine speed characteristic N1 indicated by the one-dot chain line.
[0096]
In other words, even during a light load or a sudden load, the optimum holding time T can be set according to the engine load that does not cause a dead time or a short time. During this holding time T, a predetermined low rotational speed n1 By keeping the low pump torque at a small value Tp1 corresponding to the engine lag down, it is possible to suppress the engine lag down at the time of a light load and a sudden load.
[0097]
Thus, according to the first embodiment of the present invention, the holding time T held at the low value Tp1 of the low pump torque corresponding to the predetermined low rotational speed n1 is the reference time T1 and the variable time corresponding to the engine load. Since the pump torque is held at a small value Tp1 during this holding time T, when the engine load is a large load, the engine speed characteristic N1 shown in FIG. A desirable engine speed characteristic similar to the engine speed characteristic is obtained, and when the engine load is a small load, a desirable engine speed characteristic similar to the engine speed characteristic N1 of FIG. Therefore, there is no concern of causing the engine speed characteristic N1 in FIG. 13B and the engine speed characteristic N1 in FIG. 14B, and the engine speed is maintained at a predetermined low speed n1. When the operating device 5 is operated from the non-operating state, the pump torque control with higher accuracy can be realized, and the operating device 5 is operated from the non-operating state while preventing a decrease in driving performance of a hydraulic actuator (not shown). The engine lag down that occurs for a moment can be suppressed, and the operability and workability of the hydraulic excavator provided with the first embodiment can be improved.
[0098]
FIG. 11 is a flowchart showing a processing procedure in the vehicle body controller included in the second embodiment of the present invention.
[0099]
In the second embodiment including the vehicle body controller 13 that performs the processing shown in FIG. 11, only the calculation means for obtaining the variable time included in the holding time T according to the load of the engine 1 is described above. Different from. Other configurations are the same as those of the first embodiment described above.
[0100]
In the second embodiment, the calculation means has an original PQ corresponding to the discharge pressure P of the main pump 2 detected by the discharge pressure sensor 10 within the reference time T1 and the target engine speed (for example, the rated engine speed n2). The first calculation means for obtaining the first target maximum pump torque MaxT1 from the diagram and the PQ diagram 23 in FIG. 3, the pilot pressure Pi detected by the pilot pressure sensor 11 within the reference time T1, and a pilot set in advance Based on the relationship between the pressure Pi and the displacement volume q of the main pump 2, the second calculation means for obtaining the second target maximum pump torque MaxT2, and the first target maximum pump torque MaxT1 obtained by the first calculation means described above. And third computing means for obtaining a third target maximum pump torque MaxT3 that is the minimum value of the second target maximum pump torque MaxT2 obtained by the second computing means. And Nde.
[0101]
Further, fourth calculation means for obtaining a fourth target maximum pump torque MaxT, which is the largest value among the third target maximum pump torque MaxT3 obtained by the third calculation means within the reference time T1, and a preset fourth time. 5th which calculates | requires applicable suppression time T2 as above-mentioned variable time based on the relationship between target maximum pump torque and suppression time T2 of engine lag down, and 4th target maximum pump torque MaxT calculated | required by the 4th calculating means. Computing means.
[0102]
The processing operation in the second embodiment will be described mainly based on FIG.
[0103]
Note that steps S1 to S10 and S16 to S19 in FIG. 11 are the same as the processing steps S1 to S10 and S16 to S19 shown in FIG. 9 in the first embodiment described above, and are redundant, so as to avoid complexity. In addition, here, the description of the processing contents of the procedures S1 to S10 and S16 to S19 will be omitted as much as possible.
[0104]
In the second embodiment, the controller device 5 is operated from a state in which the controller device 5 is not operated and is controlled with a small value Tp1 of the low pump torque corresponding to the predetermined low rotational speed n1, and the reference time When the timer 1 related to T1 has not yet reached 0 and the time is being measured for the reference time T1, the timer 1 is counted in step S9 in FIG. The discharge pressure P of the main pump 2 is input by the signal, and the process proceeds to step S20.
[0105]
In this step S20, the first calculation means included in the vehicle body controller 13 performs a calculation for obtaining the first target maximum pump torque MaxT1. In this case, the corresponding displacement volume q is obtained from the discharge pressure P of the main pump 2 and the original PQ diagram corresponding to the target engine speed, that is, the PQ diagram 23 in FIG. The first target maximum pump torque MaxT1 is obtained by 1).
[0106]
Next, the procedure proceeds to step S21, and the pilot pressure Pi detected by the pilot pressure sensor 11 in accordance with the operation of the operating device 5 by the second calculation means included in the vehicle body controller 13 and the preset FIG. From the relationship between the pilot pressure pi and the displacement volume q, first, the corresponding displacement volume q is obtained, and then, the displacement pressure q and the discharge pressure P of the main pump 2 detected by the discharge pressure sensor 10. Based on the above, the second target maximum pump torque MaxT2 is obtained by the above-described equation (1).
[0107]
Next, the process proceeds to step S22, in which the first target maximum pump torque MaxT1 calculated by the first calculation means and the second target maximum pump calculated by the second calculation means are calculated by the third calculation means included in the vehicle body controller 13. A third target pump torque MaxT3, which is the minimum value of the torque MaxT2, is obtained.
[0108]
Next, the process proceeds to step S23, and the fourth target means included in the vehicle body controller 13 compares the third target maximum pump torque MaxT3 calculated within the reference time T1 with the fourth target maximum pump torque MaxT. . If the third target maximum pump torque MaxT3 obtained in step S22 is larger than that obtained so far, in step S24, the third target maximum pump torque MaxT3 is changed to the fourth target maximum pump torque MaxT. That is, the processing contents of steps S23 and S24 are the contents of the calculation of the fourth calculation means.
[0109]
When it is determined in step S23 that the third target maximum pump torque MaxT3 obtained by the third calculation means is smaller than the fourth target maximum pump torque MaxT obtained so far, this is true in step S24. After finishing the process of setting the third target maximum pump torque MaxT3 to the fourth target maximum pump torque MaxT, the process proceeds to step S25.
[0110]
In this step S25, the fifth calculation means included in the vehicle body controller 13 is equivalent to the relationship between the preset fourth target maximum pump torque and the engine lag down suppression time T2, that is, the relationship shown in FIG. Based on the above relationship and the fourth target maximum pump torque MaxT obtained by the fourth computing means, a calculation for obtaining the corresponding suppression time T2 is performed, and a process for setting the suppression time T2 in the timer 2 is performed.
[0111]
Subsequent to this step S25, the pump torque is set to a small value Tp1 (AI rotation) of the low pump torque shown in FIG. 4 corresponding to a predetermined low rotational speed n1, as in the step S4.
[0112]
After step S26, the process proceeds to step S6. In this step S6, as described above, a control signal (OFF signal) corresponding to the small value TP1 of the low pump torque is output from the torque control means included in the vehicle body controller 13 to the electromagnetic valve 16. Accordingly, the torque control valve 7 is positioned in the left direction in FIG. 1, the tilt angle of the main pump 2 is minimized, and the pump torque is maintained at the small value Tp1 of the low pump torque.
[0113]
Other processes are the same as those in the first embodiment described above.
[0114]
Even in the second embodiment configured as described above, the holding time T held at the low value Tp1 of the low pump torque corresponding to the predetermined low rotational speed n1 is the reference time T1 and the variable time corresponding to the engine load. Since it consists of a certain suppression time T2, it can be set to the optimal holding time T according to the magnitude of the engine load, and the same effect as the first embodiment described above can be obtained.
[0115]
In particular, in the second embodiment, the suppression time T2, that is, the variable time is obtained in association with the pilot pressure Pi associated with the operation of the operation device 5, and the pump torque is controlled. The pump torque control according to can be realized, and the operability can be further improved.
[0116]
FIG. 12 is a flowchart showing a processing procedure in the vehicle body controller included in the third embodiment of the present invention.
[0117]
In the third embodiment including the vehicle body controller 13 that performs the processing shown in FIG. 12, only the arithmetic means for obtaining the variable time included in the holding time T according to the load of the engine 1 is the first and first described above. Different from the second embodiment. Other configurations are the same as those of the first and second embodiments described above.
[0118]
In the third embodiment, the calculation means calculates the first target maximum from the discharge pressure P of the main pump 2 detected by the discharge pressure sensor 10 and the tilt angle detected by the tilt sensor 9 within the reference time T1. First calculation means for obtaining the pump torque MaxT1, and second calculation for obtaining the second target maximum pump torque MaxT2 that is the largest value of the first target maximum pump torque MaxT1 obtained by the first calculation means within the reference time T1. A corresponding suppression time T2 based on the relationship between the second target maximum pump torque set in advance and the engine lag down suppression time T2 and the second target maximum pump torque MaxT2 obtained by the second calculation means. And a third calculating means for determining as a variable time.
[0119]
The processing operation in the third embodiment will be described mainly based on FIG.
[0120]
Note that steps S1 to S9 and S16 to S19 in FIG. 12 are the same as the processing steps S1 to S9 and S16 to S19 shown in FIG. 9 in the first embodiment described above, and are redundant, so as to avoid complexity. In addition, here, the description of the processing contents of these procedures S1 to S9 and S16 to S19 will be omitted as much as possible.
[0121]
In the third embodiment, as in the first and second embodiments described above, the operating device 5 is in a non-operating state and is controlled with a small value Tp1 of low pump torque corresponding to a predetermined low rotational speed n1. When the controller device 5 is operated from the current state, and the timer 1 related to the reference time T1 has not yet reached 0, and the time for the reference time T1 is being measured, step S9 in FIG. In step S30, the timer 1 is counted, and the process proceeds to step S30. In step S30, the discharge pressure P of the main pump 2 is input by a signal from the discharge pressure sensor 10, and the tilt angle of the main pump 2 is input by a signal from the tilt sensor 9. Next, the procedure proceeds to step S31.
[0122]
In step S31, the first calculation means included in the vehicle body controller 13 performs calculation for obtaining the first target maximum pump torque MaxT1. In this case, based on the discharge pressure P of the main pump 2 detected by the discharge pressure sensor 10 and the tilt angle of the main pump 2 detected by the tilt sensor 9, the first target maximum is obtained by the above-described equation (1). A pump torque MaxT1 is obtained.
[0123]
Next, the process proceeds to step S32, and the second target means included in the vehicle body controller 13 compares the first target maximum pump torque MaxT1 obtained within the reference time T1 with the second target maximum pump torque MaxT. If the first target maximum pump torque MaxT1 obtained in step S31 is larger than that obtained so far, in step S33, the first target maximum pump torque MaxT1 is set to the second target maximum pump torque MaxT. That is, the processing contents of steps S32 and S33 are the calculation contents of the second calculation means.
[0124]
When the first target maximum pump torque MaxT1 determined by the first calculation means is smaller than the second target maximum pump torque MaxT determined so far in the determination of step S32, and the first target corresponding in step S33 After the process of setting the maximum pump torque MaxT1 to the second target maximum pump torque MaxT is finished, the process proceeds to step S34.
[0125]
This step S34 is a third calculation means included in the vehicle body controller 13, and is a relationship between the preset second target maximum pump torque and the engine lag down suppression time T2, that is, the relationship shown in FIG. Based on the second target maximum pump torque MaxT obtained by the second computing means, a computation for obtaining the suppression time T2 is performed, and the suppression time T2 is set in the timer 2. Next, the procedure proceeds to step S35. In step S35, as in step S4, the pump torque is set to a small value Tp1 (AI rotation) of the low pump torque shown in FIG. 4 corresponding to a predetermined low rotation speed n1.
[0126]
Next, the process proceeds to step S6, and as described above, the control signal (OFF signal) corresponding to the small value Tp1 of the low pump torque is output from the torque control means included in the vehicle body controller 13 to the solenoid valve 16. The Accordingly, the torque control valve 7 is positioned in the left direction, the tilt angle of the main pump 2 is minimized, and the pump torque is maintained at the small value Tp1 of the low pump torque.
[0127]
That is, a process of holding the low pump torque at a small value Tp1 is performed for the reference time T1 counted from when the operating device 5 is operated from the non-operating state.
[0128]
Other processes are the same as those in the first and second embodiments described above.
[0129]
Even in the third embodiment configured as described above, the holding time T held at the low value Tp1 of the low pump torque corresponding to the predetermined low rotational speed n1 is the reference time T1 and the variable time corresponding to the engine load. Since it consists of a certain suppression time T2, it can be set to the optimum holding time T according to the magnitude of the engine load, and the same effect as the first and second embodiments described above can be obtained.
[0130]
【The invention's effect】
Since the present invention is configured as described above, more accurate pump torque control can be realized when the operating device is operated from a non-operating state in which the engine speed is maintained at a predetermined low speed. The operability of the construction machine equipped with the engine lag-down prevention device can be suppressed while preventing the engine lag-down that occurs for a moment when the operation device is operated from the non-operating state, while preventing the drive performance of the hydraulic actuator from being lowered. And workability can be improved compared with the past.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a main part of a construction machine provided with an engine lug-down prevention device of the present invention.
FIG. 2 is a diagram showing a pump discharge pressure-push-off volume characteristic (corresponding to a PQ characteristic) and a pump discharge pressure-pump torque characteristic among the basic characteristics possessed by the construction machine shown in FIG.
FIG. 3 is a diagram showing PQ diagram movement characteristics among basic characteristics possessed by the construction machine shown in FIG. 1;
4 is a diagram showing a target engine speed-torque characteristic among basic characteristics possessed by the construction machine shown in FIG. 1; FIG.
FIG. 5 is a diagram showing position control characteristics among basic characteristics possessed by the construction machine shown in FIG. 1;
6 is a diagram showing engine control characteristics possessed by the construction machine shown in FIG. 1; FIG.
FIG. 7 is a diagram showing a pilot pressure-push-off volume characteristic stored in a vehicle body controller included in the first embodiment of the engine lag-down prevention device of the present invention.
FIG. 8 is a diagram showing a torque MaxT-suppression time T3 characteristic stored in a vehicle body controller included in the first embodiment of the present invention.
FIG. 9 is a flowchart showing a processing procedure in the vehicle body controller included in the first embodiment of the present invention.
FIG. 10 is a graph showing engine speed characteristics at the time of heavy load / sudden load obtained in the first embodiment of the present invention.
FIG. 11 is a flowchart showing a processing procedure in a vehicle body controller included in the second embodiment of the present invention.
FIG. 12 is a flowchart showing a processing procedure in a vehicle body controller included in the third embodiment of the present invention.
FIGS. 13A and 13B are diagrams for explaining problems in the prior art, in which FIG. 13A shows a desirable engine speed characteristic at a heavy load and a sudden load, and FIG. 13B shows a problem at a small load and a sudden load. It is a figure which shows an engine speed characteristic.
14A and 14B are diagrams for explaining problems in the prior art, in which FIG. 14A shows a desirable engine speed characteristic at a small load and a sudden load, and FIG. 14B shows a problem at a large load and a sudden load. It is a figure which shows an engine speed characteristic.
[Explanation of symbols]
1 engine
2 Main pump (variable displacement hydraulic pump)
3 Pilot pump
4 tanks
5 Operation device
6 Tilt control actuator
6a Pressure receiving chamber
6b Pressure receiving chamber
6c spool
7 Torque control valve (torque adjustment means)
7a spool
7b Spring
7c Pressure receiving chamber (torque control means)
7d Pressure receiving chamber
8 Position control valve (torque adjustment means)
8a spring
8b spool
9 Tilt sensor (Tilt angle detection means)
10 Discharge pressure sensor (Discharge pressure detection means)
11 Pilot pressure sensor (Pilot pressure detection means)
12 Speed indicator (Engine speed indicator)
13 Car body controller (torque control means) (calculation means)
14 Fuel injection pump
15 Engine controller (engine speed control means)
16 Solenoid valve (torque control means)
16a spring
23 PQ diagram
24 PQ diagram
25 Engine maximum torque diagram
26 Maximum pump torque diagram
n1 Predetermined low speed
n2 Rated speed
Value Tp1
Maximum value Tp2
T retention time
T1 reference time
T2 suppression time

Claims (4)

Engine, main pump driven by the engine, torque adjusting means for adjusting the maximum pump torque of the main pump, a hydraulic actuator driven by pressure oil discharged from the main pump, and an operation for operating the hydraulic actuator An engine speed instruction means for instructing a target engine speed, an engine speed in accordance with the target engine speed instructed by the engine speed instruction means, and non-operation of the operating device. Provided in a construction machine having an engine speed control means for controlling the engine speed to a predetermined low speed when a predetermined monitoring time has elapsed;
In a non-operation state where the engine speed is controlled to the predetermined low speed by the engine speed control means, the torque adjusting means is set so that the pump torque is low according to the predetermined low speed. Torque control for controlling the torque adjusting means so as to continuously reduce the pump torque according to the predetermined low rotational speed during a predetermined holding time when the operating device is operated from the non-operating state. Including means,
In an engine lag down prevention device for a construction machine that suppresses a significant decrease in the engine speed that occurs when the operating device is operated from the non-operating state,
The predetermined holding time is composed of a reference time forming a fixed time and a variable time that is a time following the reference time,
An engine lug-down prevention device for a construction machine, comprising arithmetic means for obtaining the variable time in accordance with the load of the engine. While having a discharge pressure detecting means for detecting the discharge pressure of the main pump,
The computing means is
First calculation means for obtaining a first target maximum pump torque from the discharge pressure of the main pump detected by the discharge pressure detection means within the reference time and an original PQ diagram corresponding to the target engine speed;
Second computing means for obtaining a second target maximum pump torque that is the largest value of the first target maximum pump torques obtained by the first computing means within the reference time;
Based on the relationship between the preset second target maximum pump torque and the engine lag down suppression time and the second target maximum pump torque obtained by the second calculation means, the corresponding suppression time is set to the variable time. The engine lug-down prevention device for a construction machine according to claim 1, further comprising: third calculating means obtained as follows. A discharge pressure detecting means for detecting a discharge pressure of the main pump;
A pilot pressure detecting means for detecting a pilot pressure of the operating device for operating the hydraulic actuator,
The computing means is
First calculation means for obtaining a first target maximum pump torque from the discharge pressure of the main pump detected by the discharge pressure detection means within the reference time and an original PQ diagram corresponding to the target engine speed;
A second target maximum pump torque for obtaining a second target maximum pump torque based on a pilot pressure detected by the pilot pressure detecting means within the reference time and a relationship between a pilot pressure set in advance and a displacement of the main pump; Computing means;
Third calculation means for obtaining a third target maximum pump torque that is a minimum value of the first target maximum pump torque obtained by the first calculation means and the second target maximum pump torque obtained by the second calculation means; ,
Fourth computing means for obtaining a fourth target maximum pump torque that is the largest value of the third target maximum pump torques obtained by the third computing means within the reference time;
Based on the relationship between the preset fourth target maximum pump torque and the engine lag down suppression time and the fourth target maximum pump torque obtained by the fourth calculation means, the corresponding suppression time is set to the variable time. 5. The engine lug-down prevention device for a construction machine according to claim 1, further comprising: The main pump comprises a variable displacement hydraulic pump, a tilt control actuator for controlling the tilt angle of the variable displacement hydraulic pump, a discharge pressure detecting means for detecting a discharge pressure of the variable displacement hydraulic pump, A tilt angle detecting means for detecting the tilt angle of the variable displacement hydraulic pump;
The computing means is
A first target maximum pump torque is obtained from the discharge pressure of the variable displacement hydraulic pump detected by the discharge pressure detecting means within the reference time and the tilt angle detected by the tilt angle detecting means. One computing means;
Second computing means for obtaining a second target maximum pump torque that is the largest value of the first target maximum pump torques obtained by the first computing means within the reference time;
Based on the relationship between the preset second target maximum pump torque and the engine lag down suppression time and the second target maximum pump torque obtained by the second calculation means, the corresponding suppression time is set as a variable time. 3. The engine lug-down prevention device for a construction machine according to claim 1, further comprising third calculating means to be obtained.

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