JP2015081545A - Reducing agent supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reductant supply device which can properly defrost a reductant which is frozen in a tank even in a low-temperature environment.SOLUTION: An addition valve 1 of a reductant supply device receives the supply of urea water from a tank 4, and adds the urea water to an exhaust passage 2 by valve-opening drive by an electronic control device 6. When a temperature in the tank 4 is lowered at the heating of the urea water frozen in the tank 4 by a heater 14, that is, when the urea water is not completely defrosted by only the heating by the heater 14, the electronic control device 6 introduces an exhaust gas into the tank 4 on the basis of the pressure of the exhaust gas in the exhaust passage 2 by bringing the addition valve 1 into a valve-opened state in a state that the drive of a pump 5 is stopped. By introducing the high-temperature exhaust gas in the exhaust passage 2 into the tank 4 as above, the urea water can be properly defrosted even in a low-temperature environment in which the urea water in the tank 4 cannot be completely defrosted by only the heating by the heater 14.

Description

  The present invention relates to a reducing agent supply apparatus.

  As an exhaust gas purification device for an internal combustion engine, a device that reduces and purifies NOx in exhaust gas by the NOx purification catalyst by adding a reducing agent upstream of a selective reduction type NOx purification catalyst provided in an exhaust passage. Are known. Such an exhaust purification device includes an addition valve that receives the supply of the reducing agent from the tank and adds the reducing agent to the exhaust passage in order to realize the addition of the reducing agent upstream of the NOx purification catalyst in the exhaust passage. A reducing agent supply device is provided. Further, Patent Document 1 describes that a heater for heating the reducing agent in the tank is provided in the reducing agent supply device.

JP2012-219655A

  By the way, when the reducing agent is frozen in the tank, it is conceivable that the frozen reducing agent is thawed through heating of the heater. is there. If the reducing agent frozen in the tank cannot be thawed, the reducing agent cannot be properly supplied from the tank to the addition valve, which may hinder the addition of the reducing agent from the addition valve to the exhaust passage. .

  An object of the present invention is to provide a reducing agent supply device capable of appropriately thawing a reducing agent frozen in a tank even in a low temperature environment.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
A reducing agent supply device that solves the above problems includes a heater that heats a reducing agent in a tank, and an addition valve that receives the supply of the reducing agent from the tank and adds the reducing agent to an exhaust passage of an internal combustion engine. The reducing agent is heated by a heater in order to thaw the reducing agent frozen in the tank. However, in a low-temperature environment, the frozen reducing agent cannot be thawed only by heating the heater, and in this case, the temperature in the tank decreases when the heater is heated. In such a situation, high temperature exhaust gas is introduced into the tank through the pressure in the exhaust passage of the internal combustion engine by opening the addition valve. By introducing high-temperature exhaust gas into the tank in this way, the reducing agent can be appropriately thawed even in a low-temperature environment where the reducing agent in the tank cannot be thawed only by heating with the heater.

1 is a schematic diagram showing an entire reducing agent supply apparatus.

Hereinafter, an embodiment of a reducing agent supply apparatus will be described with reference to FIG.
As shown in FIG. 1, the addition valve 1 of the reducing agent supply device is provided upstream of the selective reduction type NOx purification catalyst 12 in the exhaust passage 2 of the internal combustion engine 11. The addition valve 1 is connected to a tank 4 through a pipe 3, and a pump 5 is provided in a portion of the pipe 3 located in the tank 4. Through the driving (forward rotation) of the pump 5, urea water in the tank 4 is supplied to the addition valve 1 through the pipe 3. The reducing agent supply device includes an electronic control device 6 that controls the driving of the addition valve 1 and the pump 5. Further, a temperature sensor 13 for detecting the temperature in the tank 4 and a heater 14 for heating the urea water in the tank 4 are connected to the electronic control unit 6.

  Then, the urea water in the tank 4 is supplied to the addition valve 1 through the pipe 3 through the drive (forward rotation) of the pump 5 by the electronic control device 6. The addition valve 1 is supplied with urea water in a pressurized state through driving of the pump 5, and adds the urea water to the exhaust passage 2 through valve opening driving by the electronic control device 6. The urea water added to the exhaust passage 2 in this way is hydrolyzed by exhaust heat to become ammonia. This ammonia is supplied as a reducing agent to the NOx purification catalyst. In addition, when the urea water in the tank 4 is frozen, the electronic control unit 6 defrosts the urea water by heating the frozen urea water with the heater 14.

  However, even if the urea water frozen in the tank 4 is to be thawed through heating of the heater 14 in a low temperature environment, it may not be thawed only by heating with the heater. In this case, urea water cannot be properly supplied from the tank 4 to the addition valve 1, which may hinder the addition of urea water from the addition valve 1 to the exhaust passage 2. In order to cope with this, the electronic control unit 6 opens the addition valve 1 to open the exhaust passage 2 when the temperature in the tank 4 decreases when the urea water in the tank 4 is heated by the heater 14. The exhaust inside is introduced into the tank 4. Specifically, the exhaust valve 1 is introduced into the tank 4 through the pressure of the exhaust gas in the exhaust passage 2 by maintaining the addition valve 1 in the open state while the drive of the pump 5 is stopped.

Next, the operation of the reducing agent supply device will be described.
The electronic control unit 6 determines whether or not the urea water in the tank 4 is frozen based on the temperature in the tank 4 detected by the temperature sensor 13. The urea water is heated by the above. If the reductant that has been frozen cannot be thawed only by heating with the heater 14, the temperature in the tank 4 decreases even when the heater 14 is heated. In such a situation, the exhaust gas is introduced into the tank 4 through the pressure of the exhaust gas in the exhaust passage 2 by keeping the addition valve 1 open while the pump 5 is stopped as described above. To do. By introducing the high-temperature exhaust gas in the exhaust passage 2 into the tank 4 in this way, the urea water is appropriately thawed even in a low temperature environment where the urea water in the tank 4 cannot be thawed only by heating by the heater 14. be able to.

According to the embodiment described in detail above, the following effects can be obtained.
(1) The urea water frozen in the tank 4 can be appropriately thawed even in a low temperature environment.

In addition, the said embodiment can also be changed as follows, for example.
In the situation where the temperature in the tank 4 decreases when the heater 14 is heated, the addition valve 1 may be opened while the pump 5 is driven to rotate in the reverse direction. In this case, by the reverse rotation of the pump 5, the hot exhaust gas in the exhaust passage 2 can be introduced into the tank 4 more efficiently, and the urea water frozen in the tank 4 can be quickly thawed.

  -Although urea water (ammonia) was illustrated as a reducing agent added from the addition valve 1, other reducing agents can also be used.

  DESCRIPTION OF SYMBOLS 1 ... Addition valve, 2 ... Exhaust passage, 3 ... Piping, 4 ... Tank, 5 ... Pump, 6 ... Electronic control unit, 11 ... Internal combustion engine, 12 ... NOx purification catalyst, 13 ... Temperature sensor, 14 ... Heater.

Claims (1)

In a reducing agent supply apparatus comprising: a heater that heats a reducing agent in a tank; and an addition valve that receives supply of the reducing agent from the tank and adds the reducing agent to an exhaust passage of an internal combustion engine.
When the reducing agent in the tank is heated by the heater and the temperature in the tank decreases, exhaust in the exhaust passage is introduced into the tank by opening the addition valve. Reducing agent supply device.