JP2014173302A - Construction machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a construction machine in which the temperature rise of a liquid reducing agent can be suppressed.SOLUTION: A construction machine comprises an aqueous urea tank 10 filled with aqueous urea 11, a spray nozzle 21 that sprays aqueous urea 11 over the prescribed position of a cooling fan 8b for a diesel engine 8, an aqueous urea pump 22 that pumps aqueous urea 11 from the aqueous urea tank 10 to the spray nozzle 21, and an aqueous urea cooling device 30A that is provided in a pipe 23 running from the aqueous urea tank 10 to the spray nozzle 21 and cools aqueous urea 11. The aqueous urea cooling device 30A comprises an aqueous urea cooler 32 that cools aqueous urea 11 and a switching device 34A that switches between flow channels so that aqueous urea 11 flows into the aqueous urea cooler 32 when the temperature of aqueous urea 11 is a prescribed temperature or higher.

Description

  The present invention relates to a construction machine that performs exhaust gas purification using a liquid reducing agent.

  In recent years, in a construction machine such as a hydraulic excavator equipped with a diesel engine, an exhaust gas treatment device is installed in an exhaust system in order to comply with high-order exhaust gas regulations.

  As this exhaust gas treatment device, a urea selective reduction type NOx treatment device using urea water (liquid reducing agent) is often used. This type of NOx treatment device is configured to be detoxified by injecting urea water upstream of a reduction catalyst provided in an exhaust gas passage and reducing NOx in the exhaust gas.

  The urea water used to reduce NOx in the exhaust gas is frozen and cannot be injected when the temperature becomes low. For this reason, a construction machine having a mechanism for preventing freezing of urea water using a heater or the like has been known (Patent Document 1).

JP 2012-241547 A

  On the other hand, construction machines are used in various environments and sometimes used at high temperatures. In such a case, the temperature of the urea water mounted on the construction machine also rises. Further, when a urea water tank is disposed in the vicinity of the engine, the temperature of the urea water rises depending on the engine state.

  This increase in the temperature of the urea water causes deterioration of the urea water, which may reduce the NOx purification action and may generate ammonia having an irritating odor.

  This invention is made | formed in view of said point, and it aims at providing the construction machine which can suppress the temperature rise of a liquid reducing agent.

From the first point of view, the above problem is
A liquid reducing agent tank filled with the liquid reducing agent;
An injection nozzle for injecting the liquid reducing agent to a predetermined position of an exhaust pipe of an engine;
A liquid reducing agent pump for pumping the liquid reducing agent from the liquid reducing agent tank to the injection nozzle;
A liquid reducing agent cooling device that is provided in a pipe from the liquid reducing agent tank to the injection nozzle and cools the liquid reducing agent;
The liquid reducing agent cooling device includes:
A liquid reducing agent cooler for cooling the liquid reducing agent;
And a switching device that switches the flow path of the liquid reducing agent so that the liquid reducing agent flows into the liquid reducing agent cooler when the temperature of the liquid reducing agent reaches or exceeds a predetermined value. It can be solved by the construction machine.

  According to the disclosed invention, when the temperature of the liquid reducing agent rises, the liquid reducing agent is sent to the liquid reducing agent cooler by the switching means, and cooling is performed. be able to.

FIG. 1 is a side view of a construction machine according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram in plan view of the upper swing body of the construction machine according to the embodiment of the present invention. FIG. 3 is a schematic configuration diagram of the urea water injection device. FIG. 4 is a schematic configuration diagram illustrating an example of the urea water cooling device. FIG. 5 is a cross-sectional view showing a thermo valve provided as a switching device in the urea water cooling device shown in FIG. FIG. 6 is a schematic configuration diagram illustrating another example of the urea water cooling device. FIG. 7 is a front view of the heat exchanger unit.

  Next, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a construction machine according to an embodiment of the present invention. In the present embodiment, a hydraulic excavator will be described as an example of a construction machine.

  In the construction machine, an upper swing body 2 is swingably mounted on an upper portion of the lower traveling body 1, and a cab 3 is provided on one front side of the upper swing body 2. A boom 4 is pivotally attached to the front center portion of the upper swing body 2 so as to be able to be raised and lowered. Further, a bucket 6 is attached to the tip of the arm 5 so as to be rotatable up and down.

  FIG. 2 is a diagram schematically illustrating a state in which the rear portion of the upper swing body is viewed in plan.

  As shown in FIG. 2, an engine room 7 is formed at the rear of the upper swing body 2, and a diesel engine 8 is installed in the engine room 7. A cooling fan 8b is provided on the front side (front side in FIG. 2) of the diesel engine 8. Further, a heat exchanger unit 13 including a radiator 14, an intercooler 15, a fuel cooler 16, and the like is installed in front of the cooling fan 8b (see FIG. 7).

  Further, an exhaust pipe 8a is connected to the diesel engine 8, and nitrogen oxide (hereinafter referred to as NOx) in the engine exhaust gas is purified on the downstream side of the exhaust pipe 8a in order to comply with higher-order exhaust gas regulations. An exhaust gas treatment device 9 is installed.

  As the exhaust gas treatment device 9, a urea selective reduction type NOx treatment device using urea water as a liquid reducing agent is used. This exhaust gas treatment device 9 injects urea water 11 from an injection nozzle 21 upstream of a reduction catalyst (not shown) provided in the exhaust pipe 8a to reduce NOx in the exhaust gas, and this reduction reaction is performed as a reduction catalyst. It is set as the structure which promotes by this and detoxifies NOx.

  The exhaust gas treatment device 9 includes a diesel particulate filter that collects particulate matter (PM) contained in exhaust gas, and a selective reducing agent that reduces and removes nitrogen oxides (NOx) (in this embodiment, urea water). A selective reduction catalyst (SCR) that reduces and removes the fuel using a gas, and an injection nozzle 21 that is disposed upstream of the SCR of the exhaust pipe 8a and injects urea water 11 toward the exhaust gas in the exhaust pipe 8a. have.

  NOx contained in the exhaust gas flowing in the exhaust pipe 8a is reduced by the urea water 11 injected from the injection nozzle 21. This reduction reaction with respect to NOx is promoted in the SCR, so that NOx contained in the exhaust gas can be rendered harmless in the exhaust gas treatment device 9.

  Therefore, in construction machines equipped with this type of exhaust gas treatment device 9, urea water 11 stored in a liquid reductant tank 10 (hereinafter referred to as urea water tank) is supplied to the injection nozzle 21 to be injected. An injection device 20 is provided.

  FIG. 3 is a perspective view schematically showing the urea water injection device 20.

  As shown in FIG. 3, the urea water injection device 20 includes a urea water tank 10, an injection nozzle 21, a urea water pump 22, a urea water cooling device 30A, and the like.

  The urea water tank 10 stores urea water 11. The urea water pump 22 sucks the urea water 11 stored in the urea water tank 10 and pumps it toward the injection nozzle 21. The injection nozzle 21 injects the urea water 11 pumped by the urea water pump 22 toward the exhaust gas in the exhaust pipe 8a.

  A suction pipe 23 and a return pipe 24 are provided between the urea water tank 10 and the urea water pump 22. The suction pipe 23 is a pipe for sucking the urea water 11 in the urea water tank 10. The return pipe 24 is a pipe for returning surplus urea water 11 from the urea water pump 22 to the urea water tank 10 when the urea water 11 is pumped from the urea water pump 22 to the injection nozzle 21. is there.

  Further, a supply pipe 25 is disposed between the urea water pump 22 and the injection nozzle 21. Therefore, the urea water 11 whose pressure has been increased by the urea water pump 22 is sent to the injection nozzle 21 via the supply pipe 25.

  By the way, as described above, when the temperature of the urea water 11 in the urea water tank 10 rises, the urea water 11 may be deteriorated, and the NOx purification action may be reduced. Therefore, in this embodiment, the urea water injection device 20 is provided with a urea water cooling device 30A that cools the urea water 11.

  Next, the urea water cooling device 30A will be described with reference to FIGS. 4 and 5 in addition to FIG.

  In the present embodiment, the urea water cooling device 30 </ b> A is provided in the suction pipe 23 disposed between the urea water tank 10 and the urea water pump 22. As shown in FIG. 4, the urea water cooling device 30A includes a urea water cooler 32, a switching device 34A, a bypass pipe 36, and the like.

  For example, as shown in FIG. 7, the urea water cooler 32 is disposed at the front position of the radiator 14 together with the intercooler 15 and the fuel cooler 16. Inside the urea water cooler 32, cooling tubes through which the urea water 11 flows are arranged with high density. The urea water 11 flowing in the cooling tube is cooled by the cooling air generated by the cooling fan 8b.

  The urea water cooler 32 having the above configuration is disposed in a bypass pipe 36 branched from the suction pipe 23. The switching device 34 </ b> A is disposed at a branch position between the suction pipe 23 and the bypass pipe 36.

  This switching device 34A performs a flow path switching process between a flow path for flowing urea water 11 flowing from the urea water tank 10 toward the urea water pump 22 to the suction pipe 23 and a flow path for flowing the urea water cooler 32. It is. In the present embodiment, a thermo valve shown in FIG. 5 is used as the switching device 34A.

  As shown in FIG. 5, the thermo valve as the switching device 34A has a spool housing 40, a spool 41, a thermo actuator 42, a return spring 44, and the like.

  The spool housing 40 has a substantially cylindrical shape, and has a port P1 connected to the urea water tank 10, a port P2 connected to the urea water pump 22, and a port P3 connected to the urea water cooler 32. Yes.

  Inside the spool housing 40, a spool 41, which is a valve body, is disposed. The spool 41 is a valve body having a bottomed cylindrical shape, and is configured to be movable in the spool housing 40 while maintaining an airtight state in the directions of arrows X1 and X2 in the drawing. A communication hole 46 communicating with the port P1 is formed at the bottom.

  The port P2 formed in the spool housing 40 is configured to be opened when the spool 41 moves in the arrow X2 direction. The port P3 is configured to open when the spool 41 moves in the direction of the arrow X1.

  The thermoactuator 42 includes an actuator body 42a and a piston 43 that extends from the actuator body 42a in the X1 direction.

  Wax is disposed inside the actuator main body 42a, and the end of the piston 43 on the X2 direction side is inserted into the wax. The actuator body 42a is disposed at a location where the temperature of the urea water 11 can be sensed. Further, a spool 41 is fixed to an end portion of the piston 43 on the X1 direction side.

  The wax in the actuator main body 42a is heated when the temperature of the urea water 11 rises, and moves the piston 43 in the X1 direction. The urea water 11 has a problem of deterioration when the temperature is 40 ° C. or higher. Therefore, in this embodiment, when the temperature of the urea water 11 exceeds 40 ° C., the piston 43 is configured to move in the X1 direction by the wax in the actuator body 42a.

  When the piston 43 moves in the X1 direction, the spool 41 moves in the X1 direction, so that the port P2 is closed and the port P3 is opened. As a result, the port P1 connected to the urea water tank 10 and the port P3 connected to the urea water cooler 32 communicate with each other. Therefore, the flow path of the urea water 11 that has flowed out of the urea water tank 10 is switched to a flow path that flows through the urea water cooler 32 (a flow path that flows through the bypass pipe 36).

  Thereby, even if the temperature of the urea water 11 rises, it is cooled by the urea water cooler 32, and the urea water 11 is maintained at a stable temperature at which no degradation or the like occurs. Therefore, by providing the urea water cooling device 30A, it is possible to reliably prevent the NOx purification function from deteriorating or the generation of a strange odor due to the generation of ammonia.

  On the other hand, when the temperature of the urea water 11 is a temperature at which deterioration does not occur, the spool 41 is urged by the return spring 44 disposed in the spool housing 40 and moves in the X2 direction.

  In this case, the port P3 connected to the urea water cooler 32 is closed, and the port P2 directly connected to the urea water pump 22 is opened. Therefore, the urea water 11 from the urea water tank 10 is directly supplied to the urea water pump 22 without being cooled by the urea water cooler 32. Thereby, it is possible to prevent the urea water 11 from being supercooled.

  In addition, since the urea water 11 can be cooled by the urea water cooler 32, the pipes 23, 24, and 25 through which the urea water 11 flows can be arranged at relatively high temperatures in the engine room 7. Become. For this reason, even if the construction machine is used under a low temperature environment in which the urea water 11 is frozen, the urea water 11 can be prevented from freezing.

  FIG. 6 shows another urea water cooling device 30B.

  In FIG. 6, the same components as those shown in FIG. 4 are denoted by the same reference numerals, and the description thereof is omitted.

  In the urea water supply device 30A shown in FIG. 4, a thermo valve is used as the switching device 34A. On the other hand, the urea water cooling device 30B shown in FIG. 6 is characterized in that the switching device 34B for switching the flow path of the urea water 11 is configured by the switching valve 50, the temperature sensor 51, the control device 52, and the like.

  The switching valve 50 is, for example, a three-way valve that switches electrically. The switching valve 50 selectively connects a pipe 23 a connecting the urea water tank 10 and the switching valve 50 to a pipe 23 b directly connected to the urea water pump 22 or a bypass pipe 36 connected to the urea water cooler 32. . The switching valve 50 is connected to the control device 52 and is configured to perform the switching process under the control of the control device 52. The pipes 23a and 23b constitute a part of the suction pipe 23.

  The temperature sensor 51 is disposed in the suction pipe 23 and detects the temperature of the urea water 11 flowing in the suction pipe 23. The temperature sensor 51 is connected to the control device 52, and the detected temperature of the urea water 11 is sent to the control device 52.

  The control device 52 performs switching control of the switching valve 50 based on the temperature of the urea water 11 sent from the temperature sensor 51. That is, when the temperature of the urea water 11 detected by the temperature sensor 51 exceeds 40 ° C. where deterioration is a problem, the control device 52 controls the switching valve 50 so that the pipe 23a and the bypass pipe 36 are connected.

  Therefore, when the temperature of the urea water 11 becomes higher than 40 ° C., the flow path of the urea water 11 is switched to the flow path that flows into the urea water cooler 32 also in the example shown in FIG. As a result, it is possible to prevent the NOx purification function from deteriorating and the generation of a strange odor due to the generation of ammonia.

  On the other hand, when the temperature of the urea water 11 detected by the temperature sensor 51 is lower than 40 ° C. where deterioration is a problem, the control device 52 controls the switching valve 50 so that the pipe 23a and the pipe 23b are connected. In this case, since the urea water 11 from the urea water tank 10 is supplied to the urea water pump 22 without being cooled by the urea water cooler 32, the urea water 11 can be prevented from being overcooled.

  In the above-described embodiment, an example in which the urea water cooling devices 30A and 30B are provided in the suction pipe 23 that connects the urea water tank 10 and the urea water pump 22 is shown. However, the arrangement positions of the urea water cooling devices 30A and 30B are not limited to the suction pipe 23. Even if the urea water cooling apparatuses 30A and 30B are provided in the return pipe 24 shown by the arrow A1 in FIG. 3, they are arranged in the supply pipe 25 shown by the arrow A2. A configuration may be adopted. Regardless of the location of the urea water cooling devices 30A and 30B, the urea water 11 can be cooled.

  However, the suction pipe 23 is a pipe having a larger flow rate of the urea water 11 than the return pipe 24 and the supply pipe 25. Therefore, the urea water 11 can be efficiently cooled by providing the urea water cooling devices 30 </ b> A and 30 </ b> B in the suction pipe 23 with a large amount of the urea water 11 flowing.

  Further, the spray nozzle 21 and the urea water pump 22 are devices that are greatly damaged when the temperature of the urea water 11 rises and deterioration occurs. Therefore, in order to protect the injection nozzle 21 and the urea water pump 22, it is desirable to cool the urea water 11 before the urea water 11 flows into the urea water pump 22.

  For the above reasons, when the urea water cooling devices 30A and 30B are provided in the suction pipe 23, the effect is greater than in the case where they are provided in the other pipes 24 and 25.

  Moreover, in above-described embodiment, the example which has arrange | positioned the urea water cooler 32 in front of the radiator 14 which comprises the heat exchanger unit 13 was shown. However, the arrangement position of the urea water cooler 32 is not limited to this position, and may be another position as long as the urea water 11 can be cooled. In that case, as shown in FIG. 6, it is good also as a structure provided with the cooling fan 55 etc. which supply the cooling water forcibly to the urea water cooler 32.

  The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific embodiments described above, and various modifications are possible within the scope of the gist of the present invention described in the claims. It can be modified and changed.

DESCRIPTION OF SYMBOLS 1 Lower traveling body 2 Upper turning body 7 Engine room 8 Diesel engine 9 Exhaust gas treatment device 10 Urea water tank 11 Urea water 13 Heat exchanger unit 20 Urea water injection device 21 Injection nozzle 22 Urea water pump 23 Suction piping 24 Return piping 25 Supply piping 30A, 30B Urea water cooling device 32 Urea water coolers 34A, 34B Switching device 36 Bypass piping 40 Spool housing 41 Spool 42 Thermo actuator 43 Piston 44 Return spring 50 Switching valve 51 Temperature sensor 52 Control device 55 Cooling fans P1-P3 Port

Claims (5)

A liquid reducing agent tank filled with the liquid reducing agent;
An injection nozzle for injecting the liquid reducing agent to a predetermined position of an exhaust pipe of an engine;
A liquid reducing agent pump for pumping the liquid reducing agent from the liquid reducing agent tank to the injection nozzle;
A liquid reducing agent cooling device that is provided in a pipe from the liquid reducing agent tank to the injection nozzle and cools the liquid reducing agent;
The liquid reducing agent cooling device includes:
A liquid reducing agent cooler for cooling the liquid reducing agent;
And a switching device that switches the flow path of the liquid reducing agent so that the liquid reducing agent flows into the liquid reducing agent cooler when the temperature of the liquid reducing agent reaches or exceeds a predetermined value. And construction machinery.   The construction machine according to claim 1, wherein the liquid reducing agent cooling device is provided in a pipe through which the liquid reducing agent flows from the liquid reducing agent tank toward the liquid reducing agent pump.   The construction machine according to claim 1 or 2, wherein the switching device is a thermo valve. The switching device is
A temperature sensor for detecting the temperature of the liquid reducing agent;
A switching valve for switching the flow of the liquid reducing agent;
The construction machine according to claim 1, further comprising a control unit that performs switching control of the switching valve based on an output from the temperature sensor.   The construction machine according to any one of claims 1 to 4, wherein the cooler for the liquid reducing agent is disposed in front of a radiator of the engine.

Images