CN104005819A - Air pressure type urea metering injection system with two urea pressure containers - Google Patents

Abstract

The invention discloses a pneumatic urea metering and injection system with double urea pressure containers. The system has a first urea pressure container connected to a compressed air source as a urea supply device and a second urea pressure container which undertakes the function of urea injection; the first Both the urea pressure vessel and the second urea pressure vessel have solenoid valves connected to the compressed air source and are provided with venting solenoid valves; the first urea pressure vessel and the second urea pressure vessel are connected through solenoid valves; the first urea pressure vessel is connected to the urea supply device connection; the second urea pressure container is connected with the urea spraying mechanism; the controller is electrically connected with each electromagnetic valve and controls its disconnection, and through the adjustment of the inlet and outlet electromagnetic valves, a constant air pressure is used to add to the urea solution. pressure. The pressure at the inlet of the urea nozzle in the system of the invention is constant, which significantly reduces the pressure wave inside the pipe caused by the urea solution pulse injection, and improves the measurement accuracy and stability of the urea solution injection amount.

Description

A pneumatic urea metering injection system with double urea pressure vessels

technical field

The present invention relates to a urea injection system for post-treatment of diesel engine exhaust, which belongs to the exhaust gas purification system of internal combustion engines; more specifically, it relates to a urea solution that uses a gas pressure source as power to inject urea solution to the exhaust system of a diesel engine to reduce Selective Catalytic Reduction SCR System for Diesel Engine NOx Emissions.

Background technique

In order to realize urea injection, the existing SCR urea injection system basically adopts two injection methods: air-assisted and non-air-assisted. Its working principle is to use a DC electric pump to pressurize the urea solution. The electric pump needs to be powered by the battery in both on-road and off-road vehicle and marine applications, requiring a lot of battery power. Recently proposed pneumatic urea injection systems such as CN102032029A patent, CN102242658A patent, and CN101975103A patent use air pressure source as power to add urea solution to a certain pressure, and then control the duty cycle of the solenoid valve of the urea nozzle to achieve the injection metering target. Although these systems are feasible in principle, there are many problems in practical application and are not practical. Moreover, there is a lot of room for improvement in terms of cost, material requirements, safety, reliability and structural design.

Contents of the invention

In order to solve the problem of high energy consumption of the storage battery in the prior art and the deficiency in the design of the pneumatic urea injection metering device, the present invention provides a new structural SCR urea injection system using a gas pressure source.

The purpose of the present invention is achieved by the following means:

A pneumatic urea metering and injection system with dual urea pressure vessels, which measures the injection amount of urea by adjusting the duty ratio of the solenoid valve of the urea nozzle, including a urea supply device, a compressed air source, a urea injection mechanism and a controller, and is characterized in that , the system has a first urea pressure container connected to the compressed air source as a urea supply device and a second urea pressure container that undertakes the urea injection function; both the first urea pressure container and the second urea pressure container have solenoid valves and compressed air The source is connected and equipped with a venting electromagnetic valve; the first urea pressure container and the second urea pressure container are connected through the electromagnetic valve; the first urea pressure container is connected with the urea supply device; the second urea pressure container is connected with the urea spraying mechanism; the controller It is electrically connected with each solenoid valve and controlled to cut off, and through the adjustment of the intake and exhaust solenoid valves, a constant air pressure is generated for pressurizing the urea solution.

The working pressure of the urea pressure vessel is 0.8-1.0MPa, and the metering injection control unit is set to adjust the solenoid valve of the first urea pressure vessel and the solenoid valve of the second urea pressure vessel so that when the first pressure vessel supplies urea solution to the second pressure vessel , the pressure in the first pressure vessel is slightly higher than the pressure in the second urea pressure vessel.

The urea pressure container, the urea supply device and the material pipeline are provided with a liquid level detection unit, a temperature detection and a heating execution unit which are controlled by the controller. The gas pressure source pressure in the system, the injection pressure of urea solution, the temperature of urea solution, the liquid level of urea tank and other parameters are fed back to the electric control unit, and the electric control unit controls the heating switch solenoid valve to adjust the flow of urea solution according to the set program. Temperature, control the opening of the cooling temperature control valve to adjust the temperature of the urea nozzle.

The scheme of the invention is applicable to various road and non-road vehicles and ships, and for commercial vehicles using air brakes, the original air compressor and air storage tank can be used.

The advantages and beneficial effects of the present invention are: firstly, since the gas pressure source is adopted in the urea injection system to control the injection pressure of the urea solution, the pressure at the inlet of the urea nozzle can be kept constant, which significantly reduces the urea solution pulse injection. The pressure wave in the pipe eliminates the adverse effect of unstable pressure wave on the injection volume of the urea nozzle. Therefore, the metering accuracy and stability of the urea solution injection amount are significantly improved.

Description of drawings

Fig. 1 is a schematic diagram of the pneumatic urea metering injection system using double urea pressure vessels in the present invention.

1. Compressed air inlet; 2. Air storage tank; 3. Compressed air outlet; 4. Air filter;

5. Heating relay switch and urea tank heating resistance wire; 6. Urea tank temperature sensor; 7. Urea solution filter; 8. Urea solution surface; 9. Urea solution level sensor; 10. Urea tank; 11. Urea nozzle; 12 1. Urea pipeline; 13. Heating relay and urea pipeline heating resistance wire; 14. Urea pressure vessel I pressure sensor; 15. Urea pressure vessel I liquid level sensor; 16. Urea pressure vessel I heating relay and heating resistance wire; 17 1. Urea pressure vessel I; 18. Urea pressure vessel II; 19. Urea pressure vessel switch solenoid valve; 20. Urea pressure vessel switch solenoid valve; 21. Urea pressure vessel I urea level; 22. Urea pressure vessel II urea level ;23. Pressure sensor of urea pressure vessel II; 24. Liquid level sensor of urea pressure vessel II; 25. Heating relay and heating resistance wire of urea pressure vessel II; 26. Inlet solenoid valve of urea pressure vessel II; 27. Urea pressure vessel II 28. End of urea pressure vessel I/II bleed pipe; 29. Vacuum pump for urea pressure vessel I; 30. Air intake solenoid valve for urea pressure vessel I; 31. Deflation solenoid valve for urea pressure vessel I; 32 , urea pipeline; 33, electronic control unit; 34, input signal of electronic control unit; 35, output signal of electronic control unit; 36, temperature sensor in urea pump cavity; 37, urea filling port; 38, urea pump; 39, Engine coolant inlet (for cooling urea nozzle); 40, engine coolant outlet (for cooling urea nozzle). 41. Engine CAN bus signal input.

All sensor input signals 6 , 9 , 38 , 14 , 15 , 23 , 24 are connected to the input terminal 34 of the electronic control unit 33 , and all relay switches and solenoid valve actuators are connected to the output terminal 35 of the electronic control unit 33 .

Detailed ways

The present invention will be further described below in conjunction with drawings and embodiments.

The invention is a urea injection system using a gas pressure source, wherein the gas pressure source can be a high-pressure gas storage bottle, or an air compressor and a gas storage tank, and the working principles of the two methods are similar. Now take the implementation of an air compressor and an air storage tank as an example.

The air storage tank 2 is inflated by a small air compressor through the compressed air inlet. As a gas pressure source for vehicles, the working pressure is generally 0.8-1.0MPa. 17 is urea pressure vessel 1, and the urea pressure vessel 1 volume that present embodiment selects is 1L, and gas pressure source and urea pressure vessel and relevant valve system constitute urea pump. The air intake solenoid valve 30 of the urea pressure vessel I is in the closed state, the connection switch solenoid valve 19 of the urea pressure vessel I and II is in the closed state, the deflation solenoid valve 30 of the urea pressure vessel I is in the open state, and the switch solenoid valve 20 of the urea pressure vessel I is open , the air vacuum pump 29 installed in the urea pressure vessel 1 takes away part of the air in the pressure vessel 1 to form a certain degree of vacuum, and the urea in the urea tank 10 is pumped into the urea pressure vessel 1 under the effect of pressure difference, when the urea pressure After the container 1 liquid level sensor 15 detects that the urea solution rises to a certain height, at this moment, the switch solenoid valve 20 that the urea pressure container 1 is connected with the urea tank 10 is closed, and the solenoid valve 30 of the urea pressure container 1 is closed. Simultaneously open the intake solenoid valve 30 of the urea pressure vessel I and the switch solenoid valve 19 connected to the urea pressure vessel II. Press the urea in the urea pressure vessel I into the urea pressure vessel II under the action of high-pressure air, and then close the connection switch solenoid valve 19 between the urea pressure vessel I and the urea pressure vessel II. The urea pressure vessel II is connected with the urea nozzle 11 through the urea pipeline 12 . The air pressure in the urea pressure vessel II is adjusted to a constant pressure through the intake solenoid valve 26 and the air discharge solenoid valve 27 of the urea pressure vessel II. In this way, the pressure of the urea in the pressure vessel II is always maintained at a constant pressure, and a constant internal pressure of the pressure vessel II is established. According to the engine operating condition information obtained from the CAN bus 41, the electronic control unit calculates the required urea injection amount, and measures the urea injection amount by adjusting the duty ratio of the solenoid valve of the urea nozzle. The pressure vessel I is responsible for the required urea supply function, and the pressure vessel II is responsible for the urea injection metering function. All valves and air vacuum pumps are regulated by the electronic control unit 33 .

When the urea pump stops working, by opening the solenoid valves 19 and 20, the urea in the urea pressure containers I and II is pressed back into the urea tank 10 under the action of the pressure difference. Close the electromagnetic valve 20 of the pressure vessel II, start the air vacuum pump at the same time, and open the electromagnetic valve 27 and the urea nozzle electromagnetic valve 11, and the residual urea in the urea pipeline 12 will be drawn back to the container cavity of the AB section of the urea pressure vessel under the action of the pressure difference Inside. Close the solenoid valves 27, 11, and open the solenoid valves 19 and 28 at the same time, the urea in the container cavity AB is pressed back into the urea tank 10 under the action of the pressure difference.

Both the urea pressure vessel I and the urea pressure vessel II are equipped with electric heating wires 16, 26, and temperature sensors 26, liquid level sensors 15, 24, pressure sensors 14, 23 are installed inside, and the relevant urea pipeline heating wires are electrically controlled. Unit 33 controls.

The urea cooling device is used for cooling the urea nozzle 11 by the coolant inlet pipe 39 and the coolant outlet pipe 40 to prevent the urea nozzle 11 from overheating and being damaged. A liquid level sensor 9 is installed on the urea tank 10 to measure the liquid level of the urea solution; a temperature sensor 40 is also installed on the urea tank to measure the temperature of the urea solution and feed it back to the electronic control unit 33; The heating resistance wire 5 (or engine coolant) heats the urea in the urea tank.

The control device and control method of the urea injection system in the present invention belong to the prior art, and therefore will not be described in detail in this specification.

Claims (3)

1. a two urea pressurized container pneumatic-typed urea metering injection system, by the emitted dose that regulates the duty of urea nozzle solenoid valve recently to measure urea, comprise urea supply device, source of compressed air, urea emitting mechanism and controller, it is characterized in that in system, having and be connected respectively as the first urea pressurized container of urea supply device with source of compressed air and bear urea-spray function the second urea pressurized container; The first urea pressurized container all has solenoid valve to be connected with source of compressed air with the second urea pressurized container and is equipped with emptying solenoid valve; The first urea pressurized container is connected by solenoid valve with the second urea pressurized container; The first urea pressurized container is connected with urea supply device; The second urea pressurized container is connected with urea emitting mechanism; Controller and each solenoid valve are electrically connected and control it and cut-off, and regulate to produce constant air pressure for pressurizeing to spray urea liquid by inlet and outlet solenoid valve.

2. two urea pressurized container pneumatic-typed urea metering injection systems according to claim 1, it is characterized in that, the working pressure of described urea pressurized container is 0.8～1.0MPa, metered injection control unit is set and regulates the solenoid valve of the first urea pressurized container and the solenoid valve of the second urea pressurized container to make in the time that the first pressurized container is the second pressurized container supply urea liquid, the first reservoir pressure is a little more than the pressure in the second urea pressurized container.

3. two urea pressurized container pneumatic-typed urea metering injection systems according to claim 1, it is characterized in that, in urea pressurized container, urea supply device and on material pipeline, be provided with controller and be subject to level detection unit, temperature sensing and the heating performance element of its control.