JP2014206053A - Engine control device of construction machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine control device of a construction machine capable of executing auto-stop control without degrading a function of an exhaust emission control system, in the engine control device of the construction machine including the exhaust emission control system executing the auto-stop control.SOLUTION: In an engine control device including an exhaust emission control system disposed on an exhaust pipe 21 of an engine 20 and provided with oxidation catalysts 30, DPF31 successively from an upstream portion, the engine 20 is automatically stopped in a car body state where the engine 20 can be automatically stopped without problems, and when an exhaust gas temperature of the upstream of the oxidation catalyst 30 is a prescribed value or more.

Description

  The present invention relates to an engine control device for a construction machine such as a hydraulic excavator or a crane that automatically stops the engine to save fuel, reduce exhaust gas, and reduce noise when the construction machine is not working. Is.

  In recent years, in order to reduce exhaust from an internal combustion engine for the purpose of environmental protection and noise prevention, for example, an automatic stop device that automatically stops the internal combustion engine when the construction machine is not working has begun to be put into practical use. In the auto stop control by the auto stop device, the fuel injection is stopped and the internal combustion engine is automatically stopped when a predetermined auto stop condition is satisfied, while the fuel injection is restarted and the internal combustion engine is restarted when the predetermined restart condition is satisfied.

  This kind of technology in construction machines such as hydraulic excavators and cranes, when a preset auto-stop condition (for example, when a lock lever that locks the hydraulic circuit inoperable) is met, There is a technique for automatically stopping (see Patent Document 1).

JP 2004-239082 A

Also, in recent years, due to increasing interest in global environmental conservation, regulations on exhaust gas emitted from diesel engines used in construction machinery have been strengthened.
Many methods for purifying diesel exhaust gas have been proposed, but a method of removing particulate pollutants (hereinafter referred to as PM (Particulate Matter)) by DPF (Diesel Particulate Filter) has become mainstream. .

Further, exhaust gas discharged from an internal combustion engine such as a diesel engine contains NO _x that affects the environment. As an apparatus for purifying the NO _x, the reducing catalyst disposed in an exhaust passage (hereinafter, SCR (Selective Catalytic Reduction), wherein the catalyst) injecting liquid reducing agent such as urea aqueous solution on the upstream side of the exhaust gas, SCR catalyst exhaust gas purification apparatus for selectively reducing and purging the NO _x in (SCR system) is known.

Here, by incorporating an exhaust gas purification device such as the DPF as described above into the engine control device of a construction machine that performs auto stop control described in Patent Document 1, environmental conservation is achieved by a synergistic effect of exhaust gas purification and auto stop. It is thought that it can plan more.
However, even if the exhaust gas purification device is simply incorporated into a construction machine that performs auto stop control, there may be a case where the auto stop control cannot be performed without impairing the function of the exhaust gas purification device.

For example, the DPF is composed of a large number of elongated cells defined by a partition made of a porous ceramic material, and particulates in exhaust gas are captured by the partition when passing through the partition. Therefore, when the amount of particulates accumulated inside increases with use, the air permeability is gradually lost due to a clogged state, and the engine performance deteriorates. For this reason, “regeneration processing” that eliminates clogging by burning PM deposited on the DPF at an appropriate timing is indispensable. Regeneration treatment means that the exhaust gas temperature is raised to about 600 ° C (or to the activation temperature for those having an oxidation catalyst), and the PM collected in the DPF is burned and removed by this high-temperature exhaust gas. To do.
The detection of the clogging of the DPF is carried out by measuring the pressure before and after the DPF with an exhaust pressure sensor and calculating the differential pressure. When the differential pressure reaches the upper limit value, the engine control unit (hereinafter referred to as ECU) automatically Alternatively, the regeneration of the DPF is started manually when the operator presses the regeneration execution switch by lighting the DPF warning lamp provided in the cab (hereinafter sometimes referred to as a cab).
Here, the PM deposited on the DPF has a different deposition state depending on the ratio of SOF (Solid Organic Fraction) and SOOT (煤), and the relationship between the differential pressure and the PM deposition amount is not always constant. There's a problem. For this reason, when auto-stop control is performed at a low temperature of the exhaust gas temperature (below the oxidation catalyst activation temperature), SOOT including the SOF component accumulates in the DPF, and the regeneration timing is determined by performing auto-stop control. There is a problem that there is a possibility that it cannot be performed accurately.

In an engine control device for a construction machine equipped with an exhaust gas purification device to which an SCR system that selectively reduces and purifies NO _x in an SCR catalyst is applied, the reducing agent remains in the reducing agent supply section after the internal combustion engine is stopped. As a result, the reducing agent is concentrated or crystallized due to evaporation of the solvent and the like, resulting in problems such as clogging in the reducing agent supply unit.
Therefore, after the internal combustion engine is stopped, a purge process for collecting the reducing agent present in the reducing agent supply unit in the reducing agent tank is performed. The purge process is performed, for example, by collecting the reducing agent using a pump of the reducing agent supply unit or by collecting the reducing agent by supplying pressurized air into the reducing agent supply unit.
Here, the auto stop control stops the internal combustion engine with the key switch turned on, and the liquid reducing agent may be injected even though there is no exhaust flow. It is necessary to coordinate with the drug supply system.
However, if the purge process of the reducing agent supply unit is always performed when the internal combustion engine is stopped, the purge process is frequently performed every time the internal combustion engine stops. It is necessary to refill the reductant and return it to a state where the reductant can be supplied immediately after starting. It takes time until the construction machine is ready for operation every time it is restarted, which reduces workability. Cause.

  The present invention has been made in view of the above problems, and in an engine control device for a construction machine equipped with an exhaust gas purification device that performs auto-stop control, the workability is reduced while maintaining the function of the exhaust gas purification device. It is an object of the present invention to provide an engine control device for a construction machine that can perform auto-stop control without causing it.

  In order to achieve the above object, a first invention is an engine control device for a construction machine, comprising an engine, an exhaust gas passage for guiding the exhaust gas of the engine to the outside, and an exhaust gas disposed in the exhaust gas passage. A gas purification device, temperature detection means for detecting an exhaust gas temperature in the exhaust gas passage, construction machine state determination means for determining whether there is no problem even if the engine is automatically stopped, and When it is determined by the construction machine state determination means that there is no problem even if the engine is automatically stopped, and the exhaust gas temperature detected by the temperature detection means is determined to satisfy a predetermined condition, And a control unit having auto-stop control means for performing auto-stop control for stopping the engine.

  In a second aspect based on the first aspect, the construction machine state determining means determines whether or not the construction machine is not working, and it is determined that the construction machine is not working. It is determined that there is no problem even if the engine is automatically stopped.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the exhaust gas purification device includes an oxidation catalyst and a DPF that are sequentially provided from the upstream side of the exhaust gas passage. The exhaust gas temperature upstream of the oxidation catalyst is detected, and the auto stop control means detects the exhaust gas temperature when the exhaust gas temperature upstream of the oxidation catalyst detected by the temperature detection means is equal to or higher than a predetermined value. It is determined that the predetermined condition is satisfied.

  According to a fourth aspect of the present invention, in the first or second aspect of the invention, the exhaust gas purification device intermittently injects and supplies the liquid reducing agent to the exhaust gas by an injection valve in accordance with the operating state of the engine. And reducing the nitrogen oxides in the exhaust gas by a reduction reaction in the reduction catalyst, the temperature detecting means detecting the exhaust gas temperature around the injection valve, and the control unit , Further comprising an injection stop determining means for determining whether or not the supply of the liquid reducing agent from the injection valve is continuously stopped for a predetermined time, wherein the auto stop control means is detected by the temperature detecting means. When the exhaust gas temperature around the injection valve is outside a predetermined range, it is determined that the exhaust gas temperature satisfies the predetermined condition, and the liquid stop agent is determined by the injection stop determination means When the injection supply is determined to have stopped continuously for a predetermined time, but automatically stopping the engine.

  According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the coolant temperature detecting means for detecting the coolant temperature of the engine and the temperature of the hydraulic oil of the hydraulic system provided in the construction machine Of the hydraulic oil temperature detecting means for detecting the voltage, the voltage detecting means for detecting the voltage between the terminals of the in-vehicle battery provided in the construction machine, and the actuator provided in the cab of the construction machine and operating in the hydraulic system. A gate lock lever detecting means for detecting a locked state and an unlocked state of a gate lock lever which permits and prohibits an operation; and a pressure detecting means for detecting a pilot pressure of the operating device of the construction machine, the construction machine state The determination means is such that the coolant temperature detected by the coolant temperature detection means is equal to or higher than a predetermined temperature, and is detected by the hydraulic oil temperature detection means. The hydraulic oil temperature is equal to or higher than a predetermined temperature, the voltage between the terminals detected by the voltage detecting means is equal to or higher than a predetermined voltage, the gate lock lever is opened by the gate lock lever open / close detecting means, or the pressure detecting means When it is determined that the pilot lever pressure is equal to or lower than the predetermined pressure, it is determined that there is no problem even if the engine is automatically stopped.

  According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the present invention further comprises a rotational speed detecting means for detecting the rotational speed of the engine, wherein the auto stop control means performs auto stop control for automatically stopping the engine. Before performing, control is performed so that the engine rotation speed detected by the rotation speed detection means becomes a predetermined value or less.

  According to the present invention, in an engine control device for a construction machine that performs auto-stop control with an exhaust gas purification device, for example, even if the engine is frequently stopped by auto-stop control, in order to maintain the function of the exhaust gas purification device, Workability is not reduced. Further, it is possible to prevent unpurified exhaust gas from being discharged into the atmosphere, and it is possible to achieve both fuel saving by auto stop control and improved reliability of exhaust gas purification.

It is a side view of the hydraulic excavator carrying the engine control apparatus of the construction machine of this invention. It is a perspective view which shows schematic structure of the cab of the hydraulic shovel carrying the engine control apparatus of the construction machine of this invention shown in FIG. It is the block diagram which showed schematic structure of 1st Embodiment of the engine control apparatus of the construction machine of this invention. It is a flowchart figure which shows the operation example of 1st Embodiment of the engine control apparatus of the construction machine of this invention. It is the block diagram which showed schematic structure of 2nd Embodiment of the engine control apparatus of the construction machine of this invention. It is a flowchart figure which shows the operation example of 2nd Embodiment of the engine control apparatus of the construction machine of this invention.

  Embodiments of an engine control device for a construction machine according to the present invention will be described below with reference to the drawings.

<First Embodiment>
A first embodiment of an engine control device for a construction machine according to the present invention will be described with reference to FIGS. In FIGS. 1 to 4, a case where the construction machine is applied to a crawler hydraulic excavator will be described as an example.
1 is a side view of a hydraulic excavator equipped with an engine control device for a construction machine according to the present invention. FIG. 2 is a perspective view showing a schematic configuration of a cab of the hydraulic excavator equipped with the engine control device for a construction machine according to the present invention shown in FIG. FIG. 3 is a block diagram showing a schematic configuration of a first embodiment of an engine control device for a construction machine according to the present invention, and FIG. 4 is an operation example of the first embodiment of the engine control device for a construction machine according to the present invention. FIG.

First, the construction of a hydraulic excavator to which the engine control device for a construction machine according to the present invention is applied will be described with reference to FIG.
In FIG. 1, the hydraulic excavator is roughly constituted by a traveling body 101, a swiveling body 102 provided on the traveling body 101 so as to be capable of turning, and an excavation attachment 103 provided at a front portion of the swiveling body 102.
The traveling body 101 is composed of left and right crawler frames 104 and crawlers (both shown only on one side) 105, and the crawlers 105 on both sides are configured to travel by being individually rotated by left and right traveling motors 107.
The swivel body 102 is schematically composed of a swivel frame 108, a cab 109, a machine room 110, and the like. An excavation attachment 103 is mounted on the front portion of the swivel body 102 so as to be raised and lowered. The excavation attachment 103 includes a boom 117, a boom cylinder 118 that raises and lowers the boom 117, an arm 119, an arm cylinder 120 that rotates the arm 119, a bucket 121, and a bucket that rotates the bucket 121. A cylinder 122 is provided. Each cylinder 118, 120, 122 corresponds to an actuator.
The cab 109 on the swivel body 102 has a substantially sealed structure that is shielded from the outside air to protect the driver from external noise, dust, and the like, and an air conditioner (air conditioner) to ensure its comfort. Etc. are provided. As shown in FIG. 2, a driver's seat 10 is provided in the cab 109. Operation levers 11 and 12 and a gate lock lever 13 are arranged on the side of the driver's seat 10. Of these, the gate lock lever 13 is a position for restricting the inlet of the cab 109 (inlet restricting position), permits the operation of the actuators such as the cylinders 118, 120, 122, etc., and is an unlock position used during normal work. And the position where the inlet of the cab 109 is opened (inlet opened position), the operation of each actuator described above is prohibited, and the position can be switched to two positions of the lock position used during non-working.

Next, the configuration of the engine control apparatus of the present invention will be described with reference to FIG.
As shown in FIG. 3, the engine control apparatus includes an engine 20, an exhaust pipe 21, an oxidation catalyst 30, a DPF 31, an engine control unit (hereinafter referred to as an ECU (Engine Control Unit)) 60, a hydraulic system control unit (control unit). ) (Hereinafter referred to as MCU (Main control unit)) 80 and the like.

A diesel engine (hereinafter referred to as an engine) 20 is installed in a machine room 110 of the revolving structure 102. An exhaust pipe (exhaust gas passage) 21 is connected to the exhaust manifold of the engine 20.
The exhaust pipe 21 collects an oxidation catalyst 30 that oxidizes nitrogen monoxide (NO) into nitrogen dioxide (NO ₂ ) and PM of the exhaust gas from the upstream side along the exhaust gas passage direction. A DPF 31 and a silencer 32 are provided.

An auto stop control unit (hereinafter referred to as “ICU”) 81 is a control unit for automatically stopping the engine 20 and reducing fuel consumption and environmental preservation when a predetermined condition is satisfied when the excavator is not working. The auto stop control unit 81 is incorporated in the MCU 80.
The MCU 80 includes a temperature sensor 26 that detects the temperature of the hydraulic oil, a pilot pressure that detects an operation amount in the operation levers 11 and 12 for driving the boom cylinder 118, the arm cylinder 120, and the bucket cylinder 122 of the hydraulic excavator. Various signals are input from a sensor 27 and a switch (gate lock lever opening / closing detection means) 28 for detecting the raising / lowering of the gate lock lever 13. The MCU 80 further includes a first determination unit (construction machine state determination means) 82 that determines whether there is no problem even if the engine 20 of the hydraulic excavator is automatically stopped based on the various signals that are input.
Further, the MCU 80 cooperates with the ECU 60 interconnected via a CAN (Controller Area Network), and controls the fuel injection valve 22, the intake air amount, the EGR amount, and the like attached to the engine 20, respectively.
Here, the ECU 60 includes a rotation speed sensor 23 that detects the rotation speed Ne of the engine 20, a water temperature sensor 24 that detects a cooling water temperature Tw for cooling the engine 20, and a battery terminal mounted on the swing body 2. Voltage sensor 25 for detecting voltage Va, exhaust gas temperature sensor 40 for detecting exhaust gas temperature Tgc upstream of oxidation catalyst 30, exhaust gas temperature sensor (temperature detecting means) 41 for detecting exhaust gas temperature Tgd upstream of DPF 31, and before and after DPF 31 Each signal from the differential pressure sensor 42 for detecting the differential pressure is input to the MCU 80 connected via the CAN.

  Next, operation | movement of 1st Embodiment of the engine control apparatus of the construction machine of this invention mentioned above is demonstrated using FIG.

  While the excavator is working at an operation site such as a construction site, the engine control device for the construction machine according to the present embodiment repeatedly executes a control process as shown in FIG.

In FIG. 4, first, when the driver rotates the key switch to the start position, the ECU 60 in the engine control device of the construction machine issues a start signal to start the engine 20 (step S41).
Thereafter, the key switch automatically returns to the ON position, and when the driver rotates the engine control dial from Lo to Hi at that position, the ECU 60 issues an accelerator signal and changes the set value of the governor to change the engine speed. Start controlling.

  After the engine 20 is started, the engine coolant temperature is measured by the water temperature sensor 24, the battery voltage by the voltage sensor 25, the rotational speed Ne of the engine 20 by the rotational speed sensor 23, the hydraulic oil temperature by the temperature sensor 26, and the pilot pressure sensor 27. The pilot pressure is detected by the switch 28, the position of the gate lock lever 13 is detected by the switch 28, the exhaust gas temperature before the oxidation catalyst 30 is detected by the exhaust gas temperature sensor 40, and is input to the ECU 60. 81, input to the first determination unit 82.

Next, the first determination unit 82 of the MCU 80 in the engine control device of the construction machine determines whether the driver is operating the operation levers 11 and 12 from the signal input after step S41 (step S42). .
When the driver operates the control levers 11 and 12, since the pilot pressure is detected by the pilot pressure sensor 27, it is determined that the hydraulic excavator is currently in a working state when the pilot pressure is equal to or higher than a predetermined pressure. The process returns to step S41 without proceeding to S43. That is, as long as the driver operates the operation levers 11 and 12 to extend and contract the boom cylinder 118, the arm cylinder 120, and the bucket cylinder 122, it is determined to be in a working state, and the process proceeds to the next step S43. To prevent it from progressing. On the other hand, when the pilot pressure is less than the predetermined pressure, it is determined that the driver has not operated the operation levers 11 and 12 and is not in a working state, and the process proceeds to the next step S43.

Next, the first determination unit 82 of the MCU 80 in the engine control device of the construction machine determines whether or not the power of the engine 20 is now required from the signal input after step S41 (step S43). If the voltage to the battery decreases from the voltage Va between the terminals of the battery by the voltage sensor 25 depending on, for example, whether or not the light is used during night work and charging is necessary, the engine power is used to drive the alternator. If the coolant temperature is low depending on whether or not the coolant temperature of the engine 20 is high by the water temperature sensor 24, the engine power is required for warming up. The boom sensor 118 and the arm cylinder 120 are required by the temperature sensor 26. If the hydraulic oil temperature is low depending on whether the hydraulic oil temperature for operating the bucket cylinder 122 or the like is high, the engine power is required for warming up. Whether the engine 20 power is required depending on these conditions Determine whether or not.
If it is determined that the power of the engine 20 is necessary, the process returns to step S41, and if it is determined that the power of the engine 20 is not necessary, the process proceeds to step S44.

  Next, the first determination unit 82 of the MCU 80 in the engine control device of the construction machine determines whether or not the gate lock lever 13 is raised by the on / off signal of the switch 28, that is, whether or not the hydraulic excavator is in an inoperative state (actuation). Whether or not it is in a state) is determined (step S44). If it is determined that the gate lock lever is not in the raised state in response to the ON signal from the switch 28, the process returns to step S41, and if it is determined that the gate lock lever is in the raised state, the process proceeds to step S45. Proceed.

Next, the auto stop control unit 81 in the engine control device of the construction machine determines whether or not the exhaust gas temperature Tgc detected by the temperature sensor 40 is equal to or higher than a predetermined value T1, that is, whether the bed temperature of the oxidation catalyst is higher than the active point (predetermined). It is determined whether or not a condition is satisfied (step S45).
If the exhaust gas temperature Tgc is equal to or higher than a predetermined value, the SOF content in the PM can be prevented from being burned by the oxidation catalyst 30 even if the engine 20 is automatically stopped, and the SOF content in the SOOT in the DPF can be prevented. The process proceeds to S46. On the other hand, if the exhaust gas temperature Tgc is less than a predetermined value, there is a possibility that the combustion of the SOF by the oxidation catalyst 30 may not be possible. Therefore, it is better not to automatically stop the engine 20, and the process returns to step S41. Therefore, it is desirable to set the predetermined value T1 as a reference to be higher than the activation temperature of the oxidation catalyst 30 (for example, 250 ° C.).

  Next, the auto stop control unit 81 in the engine control device of the construction machine has a rotational speed Ne of the engine 20 detected by the rotational speed sensor 23 within a predetermined range, that is, within a range of N1 to N2 where the engine 20 is in an idle state. It is determined whether or not there is (step S46). If the engine speed Ne is within the predetermined range, the process proceeds to step S47. If the engine speed Ne is not within the predetermined range, the process returns to step S41.

  Next, the auto stop control unit 81 in the engine control device of the construction machine stops the engine 20 (step S47). That is, in order to stop the engine 20, a fuel injection stop command is transmitted to the ECU 60 via the CAN, the fuel supply by the fuel injection valve 22 is shut off, and the engine 20 is stopped.

  In the first embodiment of the engine control device for a construction machine according to the present invention described above, an engine including an exhaust gas purification device that is disposed in the exhaust pipe 21 of the engine 20 and in which the oxidation catalyst 30 and the DPF 31 are disposed in order from the upstream side. In the control device, the engine 20 is automatically stopped when there is no problem even if the engine 20 is automatically stopped and the exhaust gas temperature upstream of the oxidation catalyst 30 is equal to or higher than a predetermined value.

If the temperature of the oxidation catalyst 30 is equal to or higher than the active point, combustion of the SOF content in the exhaust gas remaining in the exhaust pipe 21 can be continued to some extent even when the engine 20 is stopped by auto-stop. Since the temperature change 30 is small and the temperature decrease is small, combustion of the SOF can be restarted quickly after the engine 20 is restarted. Thereby, it can suppress that SOF content is contained in SOOT deposited on DPF.
By these effects, even if the engine 20 is automatically stopped by the automatic stop control, the SOF component is not accumulated in the DPF, and the variation in the differential pressure due to the change in the composition ratio of PM discharged from the engine 20 is prevented. Can do. Thereby, it is possible to accurately determine the start timing of the regeneration process and to prevent the function of the exhaust gas purification device from being impaired. Further, optimization of the regeneration process can be realized, and deterioration of fuel consumption can be prevented.
Therefore, in a construction machine such as a hydraulic excavator or a crane, it is possible to realize auto stop control while maintaining normal operation of the engine exhaust gas purification system, thereby improving product reliability and saving fuel.

  The exhaust gas temperature upstream of the oxidation catalyst 30 is measured by the exhaust gas temperature sensor 41 on the downstream side of the oxidation catalyst 30 or a temperature sensor provided at another location, in addition to the measurement by the exhaust gas temperature sensor 40. It can also be obtained by calculating and estimating from the value.

In step S47, the automatic stop control unit 81 controls the engine 20 to stop after a certain period of time when the idle speed (in the range of N1 to N2) of the engine 20 determined in step S46 has elapsed. Can be configured.
As a result, it is possible to prevent sudden stop by the engine 20 auto stop control, and to further improve the reliability of the product without adversely affecting the mounted equipment such as the engine 20.

  Further, the method is not limited to the method of determining the exhaust gas temperature upstream of the oxidation catalyst 30 and determining whether the bed temperature of the oxidation catalyst 30 is equal to or higher than the active point. For example, the temperature of the oxidation catalyst 30 is directly measured by a temperature sensor. It is also possible.

<Second Embodiment>
A second embodiment of the engine control device for a construction machine according to the present invention will be described with reference to FIGS. In FIGS. 5 and 6, a case where the construction machine is applied to a hydraulic excavator will be described as an example.
FIG. 5 is a block diagram showing a schematic configuration of a second embodiment of the engine control device for a construction machine according to the present invention, and FIG. 6 shows an operation example of the second embodiment of the engine control device for the construction machine according to the present invention. It is a flowchart figure.

  The construction machine engine control apparatus according to the second embodiment is mounted on a hydraulic excavator, and is substantially the same as the construction machine engine control apparatus according to the first embodiment in that the engine 20 is controlled. The same reference numerals are given and description thereof is omitted.

Second embodiment of the construction machine of the engine control device of the present invention uses a urea aqueous solution as a liquid reducing agent, the NO _x contained in the engine exhaust with an exhaust gas purification device for purifying by catalytic reduction reaction auto-stop An engine control device for a construction machine that performs control.
As shown in FIG. 5, the engine control device includes an engine 20, an exhaust pipe 21, an oxidation catalyst 30, a DPF 31, an SCR catalyst 33, an ammonia oxidation catalyst 34, a reducing agent tank 50, an injection nozzle 52, a reducing agent supply valve 51, and an ECU 60. , MCU 80, DCU 70 and the like.

  The exhaust pipe 21 passed through the oxidation catalyst 30, the DPF 31, the injection nozzle 52 for supplying urea aqueous solution, the SCR catalyst 33, and the SCR catalyst 33 from the upstream side along the exhaust gas passage direction. An ammonia oxidation catalyst 34 for oxidizing ammonia is provided.

The SCR catalyst 33 is a catalyst for reducing and purifying NO _x with ammonia obtained by hydrolyzing a urea aqueous solution, and may be any substance as long as it is a catalyst normally used for denitration. For example, a catalyst in which titanium oxide is loaded with a denitration active component such as vanadium or tungsten, or a catalyst in which a transition metal such as copper, iron, or cerium is ion-exchanged with a zeolite is supported on a cordierite honeycomb structure. .

  The reducing agent tank 50 stores a urea aqueous solution, and supplies the urea aqueous solution to the injection nozzle 52 via the reducing agent supply valve 51. The reducing agent supply valve 51 is controlled by the DCU 70 and intermittently supplies an aqueous urea solution corresponding to the engine operating state to the injection nozzle 52.

The aqueous urea solution injected and supplied from the injection nozzle 52 is hydrolyzed by exhaust heat and water vapor in the exhaust to generate ammonia. The generated ammonia reacts with NO _x in the exhaust gas in the SCR catalyst 33 and is decomposed into water and harmless gas. Further, since the ammonia that has passed through the SCR catalyst 33 is oxidized by the ammonia oxidation catalyst 34 disposed downstream of the exhaust gas, it is possible to prevent ammonia that emits a strange odor from being released into the atmosphere.

  The ECU 60 includes a rotation speed sensor 23 that detects a rotation speed Ne of the engine 20, a water temperature sensor 24 that detects a cooling water temperature Tw for cooling the engine 20, a voltage sensor 25 that detects a voltage Va between the terminals of the battery, and an oxidation. An exhaust gas temperature sensor 40 for detecting an exhaust gas temperature Tgc upstream of the catalyst 30, an exhaust gas temperature sensor 41 for detecting an exhaust gas temperature Tgd upstream of the DPF 31, a differential pressure sensor 42 for detecting a differential pressure before and after the DPF 31, and a reduction Each signal from the exhaust gas temperature sensor 43 that detects the exhaust gas temperature Tg around the agent injection nozzle 52 is input and can be used also in the MCU 80 connected via the CAN.

  In addition to the auto-stop control unit 81 and the first determination unit 82 that determines whether or not there is no problem even if the engine 20 of the hydraulic excavator is automatically stopped, the MCU 80 further uses the injection nozzle 52 from various input signals. It has the 2nd determination part (injection stop determination means) 83 which determines whether the injection supply of a reducing agent has stopped continuously for the predetermined time.

  Next, operation | movement of 2nd Embodiment of the engine control apparatus of the construction machine of this invention mentioned above is demonstrated using FIG.

  While the excavator is working at an operation site such as a construction site, the engine control device for the construction machine according to the present embodiment repeatedly executes a control process as shown in FIG.

In FIG. 6, first, when the driver rotates the key switch to the start position, the ECU 60 in the engine control device of the construction machine issues a start signal to start the engine 20 (step S61).
Thereafter, the key switch automatically returns to the ON position, and when the driver rotates the engine control dial from Lo to Hi at that position, the ECU 60 issues an accelerator signal and changes the set value of the governor to change the engine speed. Start controlling.

  After the engine 20 is started, the engine coolant temperature is measured by the water temperature sensor 24, the battery voltage by the voltage sensor 25, the rotational speed Ne of the engine 20 by the rotational speed sensor 23, the hydraulic oil temperature by the temperature sensor 26, and the pilot pressure sensor 27. The pilot pressure is detected by the switch 28, the position of the gate lock lever 13 is detected by the switch 28, the exhaust gas temperature Tg around the reducing agent injection nozzle 52 is detected by the exhaust gas temperature sensor 43, and is input to the ECU 60. The data is input to the control unit 81, the first determination unit 82, and the second determination unit 83.

  Next, the first determination unit 82 of the MCU 80 in the engine control device of the construction machine determines whether the driver is operating the operation levers 11 and 12 from the signal input after step S61 (step S62). . If the pilot pressure is equal to or higher than the predetermined pressure, it is determined that the excavator is currently in a working state, and the process returns to step S61 without proceeding to the next step S63. On the other hand, when the pilot pressure is less than the predetermined pressure, it is determined that the driver has not operated the operation levers 11 and 12 and the engine 20 is not in the working state, and the process proceeds to the next step S63.

  Next, the first determination unit 82 of the MCU 80 in the engine control device of the construction machine determines whether the power of the engine 20 is necessary from the signal input after step S61 (step S63). If it is determined that the power of the engine 20 is necessary, the process returns to step S61. If it is determined that the power of the engine 20 is not necessary, the process proceeds to step S64.

  Next, the first determination unit 82 of the MCU 80 in the engine control device of the construction machine determines whether the gate lock lever 13 is in the raised state based on the ON / OFF signal of the switch 28 (step S64). If it is determined that the gate lock lever is not in the raised state in response to the ON signal from the switch 28, the process returns to step S61. If it is determined that the gate lock lever is in the raised state, the process proceeds to step S65. Proceed.

  Next, the auto stop control unit 81 in the engine control device of the construction machine determines whether or not the exhaust gas temperature Tg around the reducing agent injection nozzle 52 detected by the temperature sensor 43 is within a predetermined range (T1 or more and T2 or less) (predetermined). It is determined whether or not the condition is satisfied (step S65). If the exhaust gas temperature Tg is not within the predetermined range, the process proceeds to step S66 assuming that urea in the urea water is not crystallized near the injection nozzle 52 and the injection hole of the injection nozzle 52 is not clogged. On the other hand, if the exhaust gas temperature Tg is within the predetermined range, the process returns to step S61 without automatically stopping the engine 20, assuming that urea in the urea water may crystallize and the injection nozzle 52 may be clogged. Therefore, it is desirable that the predetermined value T1 is set to be equal to or higher than the melting point temperature of urea (132.7 ° C.), and the predetermined value T2 is set to be higher than the decomposition temperature of cyanuric acid (360 ° C.).

Next, the second determination unit 83 in the engine control apparatus of the construction machine determines whether or not the urea aqueous solution injection supply from the injection nozzle 52 is stopped (step S66). When it is determined that it has stopped, the process proceeds to step S67, and when it is determined that it has not stopped, the process returns to step S61.
Further, the second determination unit 83 in the engine control device of the construction machine determines whether or not a predetermined time has elapsed since the supply of the urea aqueous solution from the injection nozzle 52 was stopped (step S67). Here, the predetermined time is a time determined in consideration of the time during which the urea aqueous solution is hydrolyzed in order to suppress the precipitation of urea in the exhaust pipe 21, and is set to 10 seconds, for example. If a predetermined time has elapsed since the stop of the supply of urea aqueous solution, the process proceeds to step S68. On the other hand, if the predetermined time has not elapsed since the stop of the supply of urea aqueous solution, the process returns to step S61.

  Next, the auto stop control unit 81 in the engine control device of the construction machine has a rotational speed Ne of the engine 20 detected by the rotational speed sensor 23 within a predetermined range, that is, within a range of N1 to N2 where the engine 20 is in an idle state. It is determined whether or not there is (step S68). If the engine speed Ne is within the predetermined range, the process proceeds to step S69. On the other hand, if the engine speed Ne is not within the predetermined range, the process returns to step S61.

  Next, the auto stop control unit 81 in the engine control device of the construction machine stops the engine 20 (step S69). That is, in order to stop the engine 20, a fuel injection stop command is transmitted to the ECU 60 via the CAN, and the engine 20 is stopped.

In the second embodiment of the engine control device for a construction machine according to the present invention, a liquid reducing agent corresponding to the engine operating state is injected by the injection nozzle 52 upstream of the SCR catalyst 33 disposed in the exhaust pipe 21 of the engine 20. In an engine control device having an exhaust gas purification device that intermittently supplies and injects, and reduces and purifies NO _x in the exhaust gas by a reduction reaction in the SCR catalyst 33, a vehicle body state in which there is no problem even if the engine 20 is automatically stopped, The fuel injection valve when the construction machine is not in operation, the exhaust gas temperature around the reducing agent injection nozzle 52 is not within a predetermined range, and the liquid reducing agent injection supply is continuously stopped for a predetermined time. The fuel supply by 22 is shut off, and the engine 20 is automatically stopped.

If the exhaust gas temperature around the injection nozzle 52 is not within the predetermined range, for example, if it is below the melting point temperature of urea or above the decomposition temperature of cyanuric acid, urea in the urea water will be in the vicinity of the injection nozzle 52 when the engine 20 is automatically stopped. Therefore, the reducing agent can be supplied to the SCR catalyst 33 immediately after restarting after the engine 20 is automatically stopped by the automatic stop control. Therefore, it is possible to prevent NO _x in the exhaust gas discharged from the engine 20 from being exhausted without being purified. Further, the purge process is not frequently performed every time the engine 20 is stopped, and the engine 20 is not started after returning to a state in which the reducing agent can be supplied at the time of restart. There is nothing.
Therefore, in construction machines such as hydraulic excavators and cranes, the engine exhaust control system can be realized while maintaining the normal operation of the engine exhaust gas purification system while improving the workability and reliability. It becomes possible to do.

  Note that the method of obtaining the exhaust gas temperature around the injection valve 52 is not limited to the method of directly measuring the temperature around the injection valve 52 by the temperature sensor 43 described in the above embodiment, and is disposed, for example, upstream of the oxidation catalyst 30. Obtained by calculating and estimating from the exhaust gas temperature sensor 40 and the exhaust gas temperature sensor 41 arranged downstream of the oxidation catalyst 30 and the exhaust gas temperature detected by the temperature sensor arranged in another location. Can do.

In step S69, the engine 2 can be stopped after a predetermined time has elapsed after the determination in step S68.
As a result, the engine 20 is prevented from being suddenly stopped by the automatic stop control, and the mounted equipment such as the engine 20 is not adversely affected, and the product reliability can be further improved.

<Others>
The present invention is not limited to the above-described embodiment, and various modifications and applications are possible. For example, in the first and second embodiments, the engine speed Ne is an idle speed N1 to N2. Although the engine is stopped on condition that it is within the range, the engine speed Ne may be automatically reduced to a predetermined idle speed and then stopped. In addition to restarting with a key switch, the engine can be restarted by various operations to start work, such as switching to a state where the gate lock lever is lowered (lock release position), operating the operation lever, etc. It can be carried out.

  Moreover, although demonstrated using the hydraulic shovel as an example of a construction machine, the construction machine in this invention is not restricted to a hydraulic shovel.

20 ... diesel engine,
21 ... exhaust pipe,
22 ... Fuel injection valve,
23 ... rotational speed sensor,
24. Engine water temperature sensor,
25 ... Battery voltage sensor,
26 ... hydraulic oil temperature sensor,
27 ... Pilot pressure sensor,
28 ... (gate lock lever) switch,
30 ... oxidation catalyst,
31 ... DPF,
32 ... Silencer,
33 ... SCR catalyst,
34 ... NH ₃ oxidation catalyst,
40 ... exhaust gas temperature sensor (before oxidation catalyst),
41 ... exhaust gas temperature sensor (before DPF),
42 ... differential pressure sensor,
43 ... exhaust gas temperature sensor (nozzle circumference),
50 ... reducing agent tank,
51 ... Reducing agent supply valve,
52 ... Reducing agent injection nozzle,
60 ... Control unit (ECU),
70 ... Reducing agent injection control unit (DCU),
80 ... Main control unit (MCU),
81 ... Auto stop control unit (ICU),
82 ... the first determination unit,
83: Second determination unit.

Claims (6)

An engine control device for a construction machine,
An engine,
An exhaust gas passage for guiding the exhaust gas of the engine to the outside,
An exhaust gas purification device disposed in the exhaust gas passage;
Temperature detecting means for detecting an exhaust gas temperature in the exhaust gas passage;
A construction machine state determination unit that determines whether or not there is no problem even if the engine is automatically stopped, and a determination that there is no problem even if the engine is automatically stopped by the construction machine state determination unit. And an auto stop control means for performing auto stop control for stopping the engine when it is determined that the exhaust gas temperature detected by the temperature detection means satisfies a predetermined condition. An engine control device for a construction machine. The engine control device for a construction machine according to claim 1,
The construction machine state determination means determines whether or not the construction machine is not working, and there is no problem even if the engine is automatically stopped when it is determined that the construction machine is not working. An engine control device for a construction machine, characterized in that it is determined to be in a state. The engine control device for a construction machine according to claim 1 or 2,
The exhaust gas purification device comprises an oxidation catalyst and a DPF provided in order from the upstream side of the exhaust gas passage,
The temperature detection means detects exhaust gas temperature upstream of the oxidation catalyst,
The auto stop control means determines that the exhaust gas temperature satisfies the predetermined condition when the exhaust gas temperature upstream of the oxidation catalyst detected by the temperature detection means is equal to or higher than a predetermined value. Engine control device for construction machinery. The engine control device for a construction machine according to claim 1 or 2,
The exhaust gas purification device intermittently injects and supplies a liquid reducing agent to the exhaust gas by an injection valve according to the operating state of the engine, and reduces nitrogen oxides in the exhaust gas by a reduction reaction in a reduction catalyst. It consists of what is reduced and purified,
The temperature detection means is configured to detect an exhaust gas temperature around the injection valve,
The control unit further includes an injection stop determination unit that determines whether or not the supply of the liquid reducing agent from the injection valve is continuously stopped for a predetermined time,
The auto stop control means determines that the exhaust gas temperature satisfies the predetermined condition when the exhaust gas temperature around the injection valve detected by the temperature detection means is outside a predetermined range, and stops the injection. An engine control device for a construction machine, wherein the engine is automatically stopped when it is determined by the determination means that the supply of the liquid reducing agent is continuously stopped for a predetermined time. The engine control device for a construction machine according to any one of claims 1 to 4,
Cooling water temperature detecting means for detecting the cooling water temperature of the engine;
Hydraulic oil temperature detection means for detecting the temperature of the hydraulic oil of the hydraulic system provided in the construction machine;
Voltage detection means for detecting a voltage between terminals of an in-vehicle battery provided in the construction machine;
A gate lock lever detecting means for detecting a locked state and an unlocked state of a gate lock lever provided in the cab of the construction machine and permitting and prohibiting an operation of an actuator operating in the hydraulic system;
Pressure detecting means for detecting a pilot pressure of the operating device of the construction machine,
The construction machine state determination means has a cooling water temperature detected by the cooling water temperature detection means that is a predetermined temperature or higher, a hydraulic oil temperature detected by the hydraulic oil temperature detection means is a predetermined temperature or higher, and the voltage It is determined that the voltage between the terminals detected by the detecting means is equal to or higher than a predetermined voltage and the gate lock lever is opened by the gate lock lever opening / closing detecting means or the pilot lever pressure is lower than the predetermined pressure by the pressure detecting means. An engine control device for a construction machine, wherein when the engine is stopped, it is determined that there is no problem even if the engine is automatically stopped. The engine control device for a construction machine according to any one of claims 1 to 5,
A rotation speed detecting means for detecting the rotation speed of the engine;
The auto stop control means includes
An engine control device for a construction machine, wherein an engine rotation speed detected by the rotation speed detection means is controlled to be a predetermined value or less before performing an automatic stop control for automatically stopping the engine.

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