JP2005188433A - Engine protecting device for construction machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine protecting device for a construction machine, in which engine failure can be prevented, while breakage of engine parts due to high temperature can be prevented. <P>SOLUTION: This device is provided with an engine 13, a variable displacement type hydraulic pump 14 provided with a regulator 39, and driven by the engine 13, a hydraulic actuator 15 driven by delivery oil from the hydraulic pump 14, an exhaust temperature sensor 22 to detect exhaust temperature t of the engine 13, a hydraulic control device 26 to control operation pilot pressure generated by an electromagnetic change-over valve in accordance with a detection signal from the exhaust temperature sensor 22, and the electromagnetic change-over valve 34 to output the operation pilot pressure to the regulator 39 of the hydraulic pump 14 to control its absorption torque. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a construction machine such as a hydraulic excavator provided with an engine, and more particularly to an engine protection device for a construction machine that controls engine load in accordance with an exhaust temperature of the engine.

  Construction machines such as hydraulic excavators generally operate front working machines and swiveling bodies, such as booms, arms, and buckets, by hydraulic actuators such as hydraulic cylinders and hydraulic motors. These hydraulic actuators are driven by an engine. The pump operates by being supplied with the discharge pressure oil from the hydraulic pump. The engine includes a fuel injection device that sprays fuel into a combustion chamber (cylinder) and a governor mechanism that controls the fuel injection device, and controls the engine output by controlling the fuel injection amount and the injection timing. It is like that.

  By the way, when the working environment (outside air temperature, altitude, solar radiation) of the construction machine is changed or the work load is increased, or when an abnormality occurs in the engine, the exhaust temperature of the engine may increase. At this time, if the exhaust temperature exceeds the allowable temperature, engine components (specifically, engine cylinders, exhaust manifolds, etc.) may be damaged.

  Therefore, conventionally, for example, the exhaust temperature is detected by a temperature sensor provided in the exhaust manifold or the like, and the number of times that the exhaust temperature exceeds the first set temperature that causes thermal fatigue in the exhaust manifold is higher than the first set temperature. The time exceeding the second set temperature that causes destruction due to oxidation in the exhaust manifold is counted, and when the number of times exceeding the first set temperature exceeds a predetermined number of times or exceeds the second set temperature A method is disclosed in which, when the time exceeds a predetermined set time, either an alarm is output or the fuel injection amount is reduced or the injection timing is changed (for example, see Patent Document 1). . In this prior art, an increase in the exhaust gas temperature is suppressed by either reducing the fuel injection amount or changing the injection timing.

JP-A-8-319874

However, there are the following problems in the above-described prior art.
That is, in the above prior art, when the engine exhaust temperature exceeds the set temperature, either the fuel injection amount is reduced or the injection timing is changed, and the engine output is lowered to increase the exhaust temperature. Is supposed to suppress. However, as it is, it cannot be said that there is no possibility that the engine output decreases too much and becomes smaller than the engine load (in other words, the absorption torque of the hydraulic pump). In this case, the engine is overloaded and engine stall occurs. .

  The present invention has been made in view of the above matters, and an object thereof is to provide an engine protection device for a construction machine that can prevent engine parts from being damaged due to high temperatures while preventing engine stall. is there.

  (1) To achieve the above object, the present invention provides an engine, a variable displacement hydraulic pump that is driven by the engine and includes a regulator, and a hydraulic actuator that is driven by pressure oil discharged from the hydraulic pump. And a temperature detecting means for detecting an exhaust temperature of the engine, and a control means for outputting a command for controlling the absorption torque to the regulator of the hydraulic pump according to a detection result of the temperature detecting means.

  In the present invention, the temperature detecting means detects the exhaust temperature of the engine, and the control means outputs a command for controlling the absorption torque to the regulator of the hydraulic pump according to the detection result. That is, for example, the control is performed so that the absorption torque of the hydraulic pump is decreased when the exhaust temperature is high, and the absorption torque of the hydraulic pump is increased when the exhaust temperature is low. Thereby, for example, when the exhaust temperature becomes high and becomes close to the allowable temperature of the engine component, the exhaust temperature can be suppressed by reducing the absorption torque of the hydraulic pump, not the engine output, and reducing the engine load. Therefore, in any case, since the engine load does not become larger than the engine output, it is possible to prevent engine parts from being damaged due to high temperatures while preventing engine stall.

  (2) In the above (1), preferably, the control means is configured to issue a command to increase or decrease the absorption torque of the hydraulic pump by a predetermined torque in a plurality of stages according to the detection result of the temperature detection means. Output to the regulator.

  This makes it possible to reduce the absorption torque by a relatively large amount by a predetermined amount, for example, when the exhaust temperature of the engine becomes high and near the allowable temperature of the engine parts, compared with the case where the absorption torque of the hydraulic pump is proportionally controlled. Thus, safety can be improved. Therefore, it is possible to more reliably prevent engine parts from being damaged due to high temperatures.

  (3) In the above (1) or (2), preferably, the control means further includes display means for performing display when the absorption torque of the hydraulic pump is controlled according to the detection result of the temperature detection means.

  According to the present invention, it is possible to prevent engine parts from being damaged due to high temperatures while preventing engine stall.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a side view showing the entire structure of a large hydraulic excavator as an example of a construction machine to which the present invention is applied.

  In FIG. 1, 1 is a large hydraulic excavator, 2 is an endless track crawler (crawler) which is a traveling means, 3 is a traveling body having the crawler belt 2 on both the left and right sides, and 4 is turned on the traveling body 3. A revolving structure 5 is provided, a driver's cab 5 is provided on the left side of the front part of the revolving structure 4, and a multi-joint type front working machine (excavation) is provided at the center of the front part of the revolving structure 4 so as to be lifted and lowered Working device). The left and right crawler belts 2 are operated by rotational drive of left and right traveling hydraulic motors (not shown), and the revolving structure 4 is driven by rotation of a turning hydraulic motor (not shown).

  Reference numeral 7 is a boom provided on the revolving body 4 so as to be rotatable in the vertical direction, 8 is an arm provided at the tip of the boom 7 so as to be rotatable, and 9 is a bucket provided at the tip of the arm 8 so as to be rotatable. The front work machine 6 includes the boom 7, the arm 8, and the bucket 9. The boom 7, the arm 8, and the bucket 9 are operated by a boom hydraulic cylinder 10, an arm hydraulic cylinder 11, and a bucket hydraulic cylinder 12, respectively.

  In the configuration described above, the crawler belt 2, the revolving body 4, the boom 7, the arm 8, and the bucket 9 constitute a driven member that is driven by a hydraulic drive device provided in the hydraulic excavator 1.

  FIG. 2 is a circuit diagram showing an embodiment of the engine protection device for a construction machine according to the present invention together with a hydraulic drive device and a controller network for the construction machine.

  In FIG. 2, for example, 13 is a 16-cylinder diesel engine (prime mover), 14 is a variable displacement hydraulic pump driven by the engine 13, and 15 is a hydraulic actuator (FIG. 2) driven by the discharge pressure oil from the hydraulic pump 14. In FIG. 2, only one hydraulic cylinder is shown as a representative, and more specifically, the left and right traveling hydraulic motors, the turning hydraulic motor, the boom hydraulic cylinder 10, the arm hydraulic cylinder 11, and the bucket The hydraulic cylinders 12 and the like) and 16 are control valves for controlling the flow of pressure oil supplied to the hydraulic actuator 15.

  Reference numeral 17 denotes a rotational speed sensor for detecting the rotational speed of the engine 13, reference numeral 18 denotes a so-called electronic governor type fuel injection device, and reference numeral 19 denotes a detection signal input from the rotational speed sensor 17 or the like. An engine control device for controlling the number.

  Reference numeral 20 denotes an engine monitor device that is connected to the engine control device 19 via the serial communication 21 and receives detection signals from various sensors that detect state quantities related to the engine 13. Reference numeral 22 denotes an exhaust temperature sensor provided on an exhaust manifold (not shown) of the engine 13, and reference numeral 23 denotes, for example, 16 cylinder temperature sensors provided on the exhaust side of the engine cylinder (not shown) (only six for convenience in FIG. 2). The detection signals from the exhaust temperature sensor 22 and the cylinder temperature sensor 23 are input to the engine monitor device 20.

  24 is provided with an operation lever 24a for instructing operation of the hydraulic actuator 15, and an operation lever device (one representative in FIG. 2) generates an operation command signal according to the operation (displacement direction and displacement amount) of the operation lever 24a. 25, an operation command signal from the operation lever device 24 is input, and a drive command signal (control signal) generated by performing predetermined arithmetic processing on the operation command signal is generated as an electromagnetic proportional pressure reducing valve (not shown). ) Is an electric lever control device. Although not shown in detail, the electromagnetic proportional pressure reducing valve reduces the primary pilot pressure from the hydraulic pressure source according to the drive command signal to generate an operating pilot pressure, and outputs the operating pilot pressure to the control valve 16. Thus, the control valve 16 is switched.

  A hydraulic control device 26 performs absorption torque control (horsepower control, details will be described later) of the hydraulic pump 14.

  A data recording device 27 is connected to the engine monitoring device 20 via the first network 28A, and is connected to the electric lever control device 25 and the hydraulic pressure control device 26 via the second network 28B. The data recording device 27 receives state quantities relating to the engine system, operation system, hydraulic system, etc. of the hydraulic excavator 1 from the engine monitoring device 20, the electric lever control device 25, and the hydraulic control device 26, and the state quantity data. Is to be remembered. Although not shown, the data recording device 27 transmits the state quantity data via a satellite communication terminal or downloads it to a portable terminal.

Here, as a major feature of the present embodiment, the hydraulic control device 26 inputs the detection signal of the exhaust temperature sensor 22 from the engine monitor device 20 via the signal line 29, for example, and the detected exhaust temperature t of the engine 13 is detected. For example, predetermined threshold values t ₁ and t ₂ (here, t ₁ <t ₂ ) set lower than the allowable temperature of engine parts (specifically, engine cylinders, exhaust manifolds, etc.) and predetermined values set substantially equal to the allowable temperature. It is determined whether it is larger than the threshold value t ₃ (where t ₂ <t ₃ ), and in the three stages (t ₁ <t ≦ t ₂ , t ₂ <t ≦ t ₃ , t ₃ <t), the hydraulic pump 14 A command signal for controlling the absorption torque is output. Details of the functions of the hydraulic control device 26 relating to such control will be described with reference to FIG.

  FIG. 3 is a block diagram showing detailed functions related to the above control of the hydraulic control device 26 together with peripheral devices.

  In FIG. 3, the hydraulic control device 26 includes an A / D circuit 30 that converts detection signals of the exhaust temperature sensor 22 and the rotation speed sensor 17 that are input via the signal line 29 from analog signals to digital signals, and control processing that will be described later. ROM (Read Only Memory) 31 for storing a program, CPU (Central Processing Unit) 32 for performing arithmetic processing based on the program stored in the ROM 31, and state quantity data relating to the hydraulic system generated by the CPU 32 A network communication circuit 33 that outputs to the second network 28B, a PWM output circuit 35 that amplifies the drive command signal generated by the CPU 32 into a pulse width modulation output signal and outputs it to the solenoid drive section 34a of the electromagnetic switching valve 34, and a CPU 32 And a digital output circuit 37 for outputting the drive command signal to the indicator lamp 36. .

  Returning to FIG. 2, 38 is a fixed displacement pilot pump as a hydraulic source having a substantially constant pressure, and 39 is a regulator for controlling the discharge flow rate of the hydraulic pump 14 so as to limit the maximum value of the absorption torque of the hydraulic pump 14. . The electromagnetic switching valve 34 is driven in response to a drive command signal from the hydraulic control device 26 and generates an operation pilot pressure based on the discharge pressure introduced from the pilot pump 38. This operation pilot pressure is applied to the regulator 39, and the limit value (maximum value) of the absorption torque of the hydraulic pump 14 by the regulator 39 is operated.

  Next, the control procedure of the hydraulic control device 26 will be described. FIG. 4 is a flowchart showing the contents of control processing of the hydraulic control apparatus.

  In FIG. 4, first, at step 100, whether or not the engine 13 is being driven is determined based on, for example, the engine speed detected by the speed sensor 17. If it is determined that the engine 13 is not driven, the determination in step 100 is not satisfied, and this determination is repeated. On the other hand, if it is determined that the engine 13 is operating, the determination in step 100 is satisfied, and the routine proceeds to step 110. In step 110, for example, the driving time of the engine 13 is calculated based on the detection signal of the rotational speed sensor 17, and this driving time is a predetermined time (specifically, the time until the engine 13 that has started driving is stabilized, for example, 1 hour). Determining whether it is longer). If the drive time of the engine 13 is shorter than the predetermined time, the determination in step 110 is not satisfied, and the routine returns to step 100 and the same procedure is repeated. On the other hand, if the drive time of the engine 13 is longer than the predetermined time, the determination at step 110 is satisfied, and the routine proceeds to step 120.

In step 120, enter the exhaust temperature t detected by the exhaust temperature sensor 22, the process proceeds to step 130, the exhaust gas temperature t is determined whether greater than the threshold value t ₁ of the first (smallest). If the exhaust gas temperature t is the first threshold value t ₁ below, the determination is not satisfied in step 130, to repeat the same procedure returns to step 100.

On the other hand, the exhaust gas temperature t may first greater than the threshold _{t 1,} the determination of step 130 is satisfied and the operation goes to step 140. In step 140, it is determined whether the exhaust gas temperature t is higher than the threshold value _{t 2} of the second (intermediate). If the exhaust gas temperature t is equal to or lower than the second threshold t ₂ (that is, t ₁ <t ≦ t ₂ ), the determination at step 140 is not satisfied and the routine proceeds to step 150. In step 150, predetermined processing is performed to generate a first drive command signals V ₁ for driving an electromagnetic switching valve 34, and outputs to the solenoid driver 34a of the electromagnetic switching valve 34. This first driving command signal V ₁ will be described with reference to FIG.

  FIG. 5 is a characteristic diagram showing a drive command signal generated by the hydraulic control device 26 and an operation pilot pressure generated by the electromagnetic switching valve 34 corresponding thereto. The horizontal axis represents time, and the vertical axis represents drive voltage and operation pilot pressure.

In FIG. 5, a first drive command signal V ₁ is a command signal for switching the electromagnetic switching valve 34 to ON / OFF state at a constant cycle, and the ratio of the drive time (valve opening time) to the constant cycle ( The so-called duty ratio is relatively smaller than drive command signals V ₂ and V ₃ described later. The electromagnetic switching valve 34 is driven according to the first drive command signal V ₁ , and generates an operation pilot pressure P ₁ based on the discharge pressure from the pilot pump 38. Then, the generated operation pilot pressure P ₁ is applied to the regulator 39, the absorption torque limit value of the hydraulic pump 14 by the regulator 39 is adapted to reduce by the predetermined torque [Delta] T _1.

  Returning to FIG. 4, the process proceeds to step 160 where a drive command signal for lighting the indicator lamp 36 is generated and output to the indicator lamp 36. When step 160 ends, the process returns to step 100 and the same procedure is repeated.

In step 140, the exhaust gas temperature t may greater than the second threshold _{t 2,} the determination is satisfied, the flow proceeds to step 170. In step 170, it is determined whether the exhaust gas temperature t is larger than the threshold value _{t 3} of the third (maximum). If the exhaust gas temperature t is equal to or lower than the third threshold value t ₃ (ie, t ₂ <t ≦ t ₃ ), the determination at step 170 is not satisfied and the routine proceeds to step 180. In step 180, a predetermined calculation process is performed to generate a _second drive command signal V ₂ for driving the electromagnetic switching valve 34 and output it to the solenoid driving unit 34 a of the electromagnetic switching valve 34.

Drive instruction signal V ₂ of the second, as shown in FIG. 5 described above, the first driving command signal V ₁ Similarly, be a command signal for switching driving the electromagnetic switching valve 34 to the ON / OFF state at a fixed period , the ratio of driving time for the predetermined period is relatively larger than the first drive instruction signal V _1. The electromagnetic switching valve 34 is driven in accordance with the second drive command signal V ₂ and generates an operation pilot pressure P ₂ (where P ₂ > P ₁ ) based on the discharge pressure from the pilot pump 38. The generated operation pilot pressure P ₂ is applied to the regulator 39, and the absorption torque limit value of the hydraulic pump 14 by the regulator 39 is reduced by a predetermined torque ΔT ₂ (where ΔT ₂ > ΔT ₁ ).

  Thereafter, the process proceeds to step 160 where a drive command signal for turning on the indicator lamp 36 is generated and output to the indicator lamp 36. When step 160 ends, the process returns to step 100 and the same procedure is repeated.

If it is determined in step 170 that the exhaust gas temperature t is greater than the third threshold value t ₃ (ie, t ₃ <t), the determination is satisfied, and the routine proceeds to step 190. In step 190, predetermined processing is performed to generate a third drive instruction signal V ₃ for driving the electromagnetic switching valve 34, and outputs to the solenoid driver 34a of the electromagnetic switching valve 34.

As shown in FIG. 5, the third drive command signal V ₃ switches the electromagnetic switching valve 34 to the ON / OFF state at a constant cycle, like the first and second drive command signals V ₁ and V _2. a command signal to be driven, the proportion of the driving time for the predetermined period is relatively larger than the second drive instruction signal V _2. The electromagnetic switching valve 34 is driven in accordance with the third drive command signal V ₃ and generates an operation pilot pressure P ₃ (where P ₃ > P ₂ ) based on the discharge pressure from the pilot pump 38. The generated operation pilot pressure P ₃ is applied to the regulator 39, and the absorption torque limit value of the hydraulic pump 14 by the regulator 39 is reduced by a predetermined torque ΔT ₃ (where ΔT ₃ > ΔT ₂ ).

  Thereafter, the process proceeds to step 160 where a drive command signal for turning on the indicator lamp 36 is generated and output to the indicator lamp 36. When step 160 ends, the process returns to step 100 and the same procedure is repeated.

  In the above description, the exhaust temperature sensor 22 constitutes temperature detection means for detecting the exhaust temperature of the engine described in the claims. The hydraulic control device 26 and the electromagnetic switching valve 34 constitute control means for outputting a command for controlling the absorption torque to the regulator of the hydraulic pump in accordance with the detection result of the temperature detection means. Further, the indicator lamp 36 constitutes a display unit that performs a display when the control unit controls the absorption torque of the hydraulic pump according to the detection result of the temperature detection unit.

Next, the operation and effect of this embodiment will be described below.
For example, a hydraulic actuator 15 of the excavator 1 (for example, the left and right traveling hydraulic motors, the turning hydraulic motor, the boom hydraulic cylinder 10, the arm hydraulic cylinder 11, When the operator operates the operation lever 24a when operating the bucket hydraulic cylinder 12 or the like, the electric lever control device 25 generates a drive command signal based on the operation signal from the operation lever device 24, and this drive command signal Is output to the electromagnetic proportional pressure reducing valve, and the control valve 16 is switched in response to this, and the hydraulic actuator 15 is driven.

  For example, when the operation of such an operation is performed at a high altitude or the like, the air density decreases and the amount of air taken into the engine 13 decreases as the altitude increases. Therefore, it is known that the exhaust temperature t of the engine 13 increases. ing. Further, it is known that when the outside air temperature increases, the intake temperature of the engine 13 also increases and the exhaust temperature t rises. When such a change in the working environment, an increase in work load, or some abnormality occurs in the engine 13 and the exhaust temperature t of the engine 13 exceeds the allowable temperature, engine parts (specifically, engine cylinders, exhaust manifolds, etc.) May be damaged.

In the present embodiment, predetermined threshold values t ₁ and t ₂ (where t ₁ <t ₂ ) lower than the allowable temperature of the engine component and a predetermined threshold value t ₃ (where t ₂ <t ₃ ) substantially equal to the allowable temperature are set. Set. If the exhaust temperature t of the engine 13 rises and the exhaust temperature t is lower than the allowable temperature but is in the range of t ₁ <t ≦ t ₂ , the process goes through steps 100, 110, 120, and 130 of FIG. In step 150, the hydraulic control device 26 performs a predetermined calculation process and outputs the first drive command signal V ₁ to the electromagnetic switching valve 34. Thus, the operation pilot pressure P ₁ produced by the electromagnetic switching valve 34 is applied to the regulator 39, to reduce the absorption torque limit value of the hydraulic pump 14 by the regulator 39 by the predetermined torque [Delta] T _1. In step 160, the drive command signal generated by the hydraulic control device 26 is output to the indicator lamp 36, and the indicator lamp 36 is turned on. Thereby, the operator can confirm that the absorption torque limit value of the hydraulic pump 14 is small.

If the exhaust temperature t of the engine 13 does not exceed the allowable temperature but is in the range of t ₂ <t ≦ t ₃ , the determination of step 170 is not satisfied through steps 100, 110, 120, 130, and 140, and step At 180, the hydraulic control device 26 performs a predetermined calculation process and outputs a _second drive command signal V ₂ to the electromagnetic switching valve 34. As a result, the operation pilot pressure P ₂ generated by the electromagnetic switching valve 34 is applied to the regulator 39, and the absorption torque limit value of the hydraulic pump 14 by the regulator 39 is reduced by a predetermined torque ΔT ₂ (where ΔT ₂ > ΔT ₁ ). .

If the exhaust temperature t of the engine 13 exceeds the allowable temperature and becomes t ₃ <t, the determination of step 170 is satisfied through steps 100, 110, 120, 130, and 140, and the hydraulic control device is determined in step 190. 26 performs a predetermined calculation process and outputs a _third drive command signal V ₃ to the electromagnetic switching valve 34. As a result, the operation pilot pressure P ₃ generated by the electromagnetic switching valve 34 is applied to the regulator 39, and the absorption torque limit value of the hydraulic pump 14 by the regulator 39 is reduced by a predetermined torque ΔT ₃ (where ΔT ₃ > ΔT ₂ ). .

As described above, in the present embodiment, the reduction range of the absorption torque limit value of the hydraulic pump 14 is stepwise as the exhaust temperature t of the engine 13 increases and approaches the allowable temperature of the engine components, or when the allowable temperature is exceeded. (ΔT ₃ > ΔT ₂ > ΔT ₁ ), the exhaust temperature t can be suppressed by reducing the load on the engine 13. Therefore, in any case, since the load of the engine 13 does not become larger than the output of the engine 13, it is possible to prevent engine parts from being damaged due to high temperatures while preventing engine stall.

  In particular, the large excavator 1 is used for, for example, debris excavation work in a vast work site, and is generally continuously operated to improve productivity. Therefore, by obtaining the above effect, the operation according to the production plan can be achieved without interrupting the debris excavation work by the hydraulic excavator.

In the above embodiment, the temperature sensor 22 provided in the exhaust manifold or the like has been described as an example of the temperature detection means for detecting the exhaust temperature t of the engine 13, but is not limited thereto. That is, for example, the average exhaust temperature t _av may be calculated from the exhaust temperature of each cylinder detected by the cylinder temperature sensor 23 provided on the exhaust side of each cylinder of the engine. FIG. 6 is a flowchart showing the control processing contents of the hydraulic control device 26 ′ in such a modification. In FIG. 6, steps that are the same as in the above embodiment are given the same reference numerals, and descriptions thereof are omitted as appropriate.

  In FIG. 6, when the engine 13 is driven and the driving time is longer than a predetermined time, the determinations of the above steps 100 and 110 are satisfied, and the process proceeds to step 200.

In step 200, the exhaust temperature of each cylinder detected by the cylinder temperature sensor 23 is input, and the average exhaust temperature t _av is calculated. Then, the process proceeds to step 210, and it is determined whether or not the average exhaust temperature t _av is higher than the first threshold value t ₁ . When the average exhaust temperature t _av is equal to or lower than the first threshold t ₁ , the determination in step 210 is not satisfied, and the same procedure is repeated by returning to step 100 described above.

On the other hand, if the average exhaust temperature t _av is greater than the first threshold t ₁ , the determination at step 210 is satisfied and the routine goes to step 220. In step 220, average exhaust gas temperature _{t av} is determined whether a second threshold value _{t 2} is greater than. When the average exhaust temperature t _av is equal to or lower than the second threshold t ₂ (that is, t ₁ <t _av ≦ t ₂ ), the determination in step 220 is not satisfied, and the process proceeds to steps 150 and 160 described above.

If the average exhaust temperature t _av is greater than the second threshold t ₂ at step 220, the determination is satisfied and the routine goes to step 230. In step 230, it is determined whether the average exhaust temperature t _av is greater than a third threshold value t ₃ . When the average exhaust temperature t _av is equal to or lower than the third threshold t ₃ (that is, t ₂ <t _av ≦ t ₃ ), the determination at step 230 is not satisfied, and the process proceeds to the above-described steps 180 and 160.

If the average exhaust temperature t _av is greater than the third threshold value t ₃ (ie, t ₃ <t _av ) in step 230, the determination is satisfied, and the process proceeds to steps 190 and 160 described above.

Also in the present modification as described above, the absorption torque limit of the hydraulic pump 14 is limited when the average exhaust temperature t _av of the engine 13 approaches the allowable temperature of the engine components or exceeds the allowable temperature, as in the above embodiment. While increasing the value reduction stepwise (ΔT ₃ > ΔT ₂ > ΔT ₁ ), the load on the engine 13 can be reduced to suppress the exhaust temperature t. Therefore, it is possible to prevent engine parts from being damaged due to high temperatures while preventing engine stall.

In the above, the hydraulic control device 26 outputs a command signal for increasing or decreasing the absorption torque of the hydraulic pump 14 by a predetermined torque in three stages according to the exhaust temperature t or the average exhaust temperature t _av of the engine 13. However, the present invention is not limited to this. For example, the number of stages may be two, four, five, or the like, or proportional control may be performed. In this case, the same effect is obtained.

  The operation lever device 24 has been described by taking the electric lever system as an example, but is not limited thereto, and may be a hydraulic pilot system, for example. Although a hydraulic excavator has been described as an example of a construction machine, the present invention is not limited to this, and the present invention can also be applied to other construction machines such as a crawler crane, a wheel loader, and the like.

It is a side view showing the whole structure of a large sized hydraulic excavator as an example of the construction machine used as the application object of the engine protection device of the construction machine of the present invention. It is a circuit diagram showing one embodiment of an engine protection device of a construction machine of the present invention with a hydraulic drive device and a controller network of a construction machine. It is a block diagram showing the detailed function of the hydraulic control apparatus which comprises one Embodiment of the engine protection apparatus of the construction machine of this invention with a peripheral device. It is a flowchart showing the control processing content of the hydraulic control apparatus which comprises one Embodiment of the engine protection apparatus of the construction machine of this invention. It is a characteristic view showing the operation command pressure generated with the drive command signal generated with the oil pressure control device which constitutes one embodiment of the engine protection device of the construction machine of the present invention, and the electromagnetic switching valve corresponding to this. It is a flowchart showing the control processing content of the hydraulic control apparatus which comprises the modification of the engine protection apparatus of the construction machine of this invention.

Explanation of symbols

13 Engine 14 Hydraulic pump 15 Hydraulic actuator 22 Exhaust temperature sensor (temperature detection means)
23 Cylinder temperature sensor (temperature detection means)
26 Hydraulic control device (control means)
34 Electromagnetic switching valve (control means)
36 Indicator light (display means)
39 Regulator

Claims (3)

  An engine, a variable displacement hydraulic pump that is driven by the engine and includes a regulator, a hydraulic actuator that is driven by pressure oil discharged from the hydraulic pump, temperature detection means that detects an exhaust temperature of the engine, and An engine protection device for a construction machine, comprising: control means for outputting a command for controlling the absorption torque to the regulator of the hydraulic pump according to a detection result of the temperature detection means.   2. The engine protection device for a construction machine according to claim 1, wherein the control means commands to increase or decrease the absorption torque of the hydraulic pump by a predetermined torque in a plurality of stages according to the detection result of the temperature detection means. An engine protection device for a construction machine, characterized in that the output is output to the regulator.   The engine protection device for a construction machine according to claim 1 or 2, further comprising display means for displaying when the control means controls the absorption torque of the hydraulic pump according to the detection result of the temperature detection means. The engine protection device for construction machinery.

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