CN101408122A - Metering and conveying method and device for extracting, metering and releasing liquid - Google Patents

Abstract

A metering and conveying method for extracting, metering and releasing a reducing agent of an after-treatment system for purifying the tail gas of the internal combustion engine; the method comprises the following steps: 1) drawing an excess of liquid greater than the desired dosage, the dosage being determined by a fixed volume container, 2) adjusting the drawn liquid to the dosage while returning excess liquid to the source, and 3) releasing the dosage of liquid. The invention provides an economical and effective method and device for metering and conveying the reducing agent to the market. Because the preposed pressurization is cancelled, the invention ensures that the whole post-processing system has simpler and more reliable structure, further reduces the manufacturing cost and further reduces the installation space; meanwhile, the metering pump has all the advantages of other metering pumps, such as stable dosage supply, strong external interference resistance, small installation volume, low energy consumption, low cost and the like. In addition, the new pipeline enables the reducing agent delivery system to react sensitively to the change of the working condition of the engine, and further reduces the energy consumption of the metering pump.

Description

Metering delivery method and device for extracting, metering and releasing liquid

technical field

The invention relates to emission control of an internal combustion engine, in particular to a metering delivery method and a device thereof for extracting, metering and releasing a reductant in a post-treatment system for exhaust gas purification of an internal combustion engine.

Background technique

Due to the urgent need to improve fuel economy, the application of diesel engines and lean burn (lean burn) gasoline engines has increased rapidly in recent years. However, because the combustion chamber and its exhaust gas contain too much oxygen, these engines emit a large amount of nitrogen oxides and the method of using a common three-way catalyst cannot work. In response to this problem, various post-treatment technologies for reducing nitrogen oxides have been proposed. Among them, injecting ammonia into the exhaust gas as a reducing agent and using it in conjunction with a selective reduction catalyst (SCR) is considered to be the most effective method for converting toxic nitrogen oxides into harmless gases. However, ammonia itself is a toxic gas, and carrying large quantities of compressed ammonia on a motor vehicle presents safety and other concerns. Urea solution is considered to be a good substitute for ammonia, because urea can decompose ammonia at high temperature, and it is safe and harmless to the environment. In fact, an aqueous urea solution can be injected into the engine exhaust, and the ammonia produced reacts with nitrogen oxides under the action of the SCR to form water and nitrogen. In order to realize this technology, a device capable of delivering and metering urea solution is required. The dosing pump is such a multifunctional device that extracts, measures, pressurizes and releases urea solution.

There have been many inventions and patents on the delivery and metering method and device of the reducing agent. Among them, Ching H. (George) Wu's patents on urea solution injection systems at Ford Motor Company and Bosch (Bosch) are the most representative. The dosage pump invented by Ching H.Wu draws a solution in a fixed volume to achieve metering and delivery. However, Bosch's patent adopts a liquid circulation method to maintain a constant force of the liquid, and then realizes metering and delivery through a metering valve or a dosage pump. Although Ching H.Wu's invention has the advantages of small size, energy saving, accurate dosage and low manufacturing cost, it needs pre-pressurization. It has been found in practice that if there is no pre-pressurization to effectively supply the liquid to the metering pump, the pumping capacity of the metering pump itself is insufficient to achieve accurate metering. However, Bosch's system has complex structure, high energy consumption, high cost and large volume. Compared with a single metering pump system, it has no commercial prospects.

Contents of the invention

The technical problem to be solved by the present invention is to provide a metering delivery method involving the extraction, metering and release of the reductant in the post-treatment system for exhaust gas purification of the internal combustion engine. This method adopts the method of overextraction plus correction. It can fully draw liquid and accurately quantify it without pre-pressurizing the liquid. The method is to pump in excess to ensure that the liquid is fully drawn into the pump, and then withdraw the excess, leaving a fixed volume of liquid and releasing it.

Another technical problem to be solved by the present invention is to provide a metering pump related to the extraction, metering and release of the reductant in the aftertreatment system of exhaust gas purification of the internal combustion engine.

In order to solve the above-mentioned first technical problem, the present invention provides a metering delivery method for extracting, metering and releasing liquid, the steps of which are as follows:

1) Excessive withdrawal of more fluid than the required dose as determined by a fixed volume container,

2) adjusting the withdrawn fluid to the dose while returning excess fluid to the fluid source, and

3) Release the dose of liquid.

In order to solve the above-mentioned first technical problem, another metering delivery method for extracting, metering and releasing liquid in the present invention, the steps are as follows:

1) using at least one container to draw and store more than the required dose of liquid,

2) preparing the dose by filling the liquid into at least one additional container of fixed volume, and

3) Release the fixed volume dose of liquid.

In order to solve the above-mentioned second technical problem, the present invention relates to a metering pump for extracting, metering and releasing the reductant in the post-treatment system of internal combustion engine exhaust gas purification. The piston, and the valves and pipes connected to the liquid cylinder to guide the flow of liquid; the movement of the piston is controlled by the pulse width analog (FPWM) signal; the piston reciprocates in the cylinder, releasing a fixed amount of liquid every week; finally The amount of liquid released is then determined by the frequency of the piston movement and the amount released per movement. The working state of the metering pump is divided into two parts: pumping liquid into the liquid cylinder and then releasing the required amount of liquid from the release valve; during the pumping process, the piston pumps slightly more liquid than the required amount (dose) into the liquid cylinder to ensure Sufficient extraction; during the release process, the piston first corrects and drives the excess part back to the liquid source and leaves the required dose of liquid, and finally releases the remaining dose part of the liquid; this part of the remaining liquid is fixed by a cylinder in the cylinder The volume of the abdominal cavity is determined; this invention also includes a pipeline that utilizes the Venturi principle to reduce the air pressure and is connected to the release valve of the metering pump, so as to reduce the resistance of the metering valve to release the liquid and increase the liquid transmission speed from the metering pump to the nozzle.

The invention provides the market with an economical and effective reducing agent metering delivery method and device. Due to the cancellation of pre-pressurization, the invention makes the structure of the whole post-processing system simpler and more reliable, the manufacturing cost is further reduced, and the installation space is further reduced; at the same time, it also has all the advantages of other metering pumps, such as stable dosage supply and anti-interference from outside Strong performance, small installation volume, low energy consumption, low cost, etc. In addition, the new piping makes the reductant delivery system more responsive to changes in engine operating conditions and further reduces the energy consumption of the metering pumps.

Description of drawings

The specific implementation manners of the present invention will be further described in detail below in conjunction with the accompanying drawings.

Figure 1 is a schematic diagram showing one form of a metering pump, overdrawing liquid through the stroke of a piston driven by an electromagnetic and air.

Figure 2 is a schematic diagram showing two forms of synchronous control signals.

Figure 3 is a schematic diagram showing one form of metering pump, the piston being driven by a solenoid and a spring.

Figure 4 is a schematic diagram showing one form of metering pump with liquid passing through the piston.

Figure 5 is a schematic diagram showing the same metering pump version as in Figure 5 but with the addition of a check valve at the inlet to improve dose preparation efficiency.

Figure 6 is a schematic diagram showing one form of metering pump with overdrawing of liquid by means of pistons having different diameters.

Figure 7 is a schematic diagram showing the same metering pump as in Figure 6, but with one less inlet restrictor valve.

Figure 8 is a schematic diagram showing a metering pump version similar to that of Figure 6, but with a double tank cylinder and the piston being entirely electromagnetically actuated.

Figure 9 is a schematic diagram showing one form of metering pump, a dual cylinder design.

Fig. 10 is a schematic diagram showing a form of air pipeline, which utilizes the Venturi principle to reduce the air pressure on the pipe wall.

Fig. 11 is a schematic diagram showing a form of air pipeline, which utilizes the Venturi principle to reduce the air pressure on the pipe wall.

The part names represented by numbers in all the above figures are explained as follows:

3: Liquid supply pipe 300: Cylinder body 305: Metering valve piston 310: Extraction valve

315: Release valve 320: Dosing liquid chamber (lower liquid chamber) 322: Extraction liquid chamber (upper liquid chamber)

324: Vent 326: Spring 330: Three-way valve 332: Two-way valve

340: liquid circuit 342: liquid return tank of lower liquid chamber 344: liquid return tank of upper liquid chamber

350: dose line

Detailed ways

Schematic diagram 1 shows the main structure of a form of the invention, ie a metering pump (hereinafter the device). The device is mainly composed of a cylinder body 300 and a piston 305. The piston reciprocates in the cylinder, and completes the extraction, measurement and release of liquid every reciprocating cycle. There is a part in the cylinder as a dose liquid chamber (hereinafter referred to as the lower liquid chamber or liquid chamber) 320, which is connected with the liquid extraction valve 310, the liquid release valve 315 and the liquid circuit 340. Wherein the valve 310 is a one-way valve, and its opening and closing are controlled by the flow direction of the liquid. When the piston 305 moves upward, a negative pressure is generated in the liquid chamber 320 , the liquid suction valve 310 is hydraulically opened, the liquid release valve 315 is closed, and the liquid is sucked into the liquid chamber 320 . When the piston 305 travels to the cylinder top (highest position), the bottom of the piston 305 crosses the dose line 350 causing more liquid than required to be dosed into the cylinder. When the piston moves downward, a positive pressure is generated in the liquid chamber 320, and the liquid extraction valve 310 is hydraulically closed, while the liquid release valve 315 remains closed, and the piston squeezes out excess liquid above the dosage line through the liquid return groove 342 and passes through The liquid circuit 340 drives back the liquid supply pipe 33 . When the bottom of the piston reaches the dose line 350, all excess liquid is expelled out of the cylinder and the remaining liquid between the dose line 350 and the bottom of the cylinder is the desired dose. At this point, since the fluid is not compressible, the piston will stop traveling down until the fluid relief valve 315 is opened. Once the release valve 315 is opened, the piston will continue to travel down to the bottom, releasing a certain volume (dose) of liquid out of the metering pump to mix with air. In order to discharge the liquid into the air delivery tube 450 with a certain air pressure, it is necessary to give the piston 305 a sufficient driving force to overcome the pressure in the air delivery tube 450 . When the liquid release process is completed, the release valve 315 is closed, the piston moves upwards, and the next cycle begins. The metering pump releases a fixed volume of liquid every time the piston reciprocates one cycle. The faster the piston reciprocates, the more doses the metering pump will deliver in a given period of time. Movement of the piston 305 may be controlled by a pulse width analog (FPWM) signal. The drive of the piston 305 can be arranged in various ways. In the arrangement shown in Figure 1, the downward movement of the piston is driven by electromagnetic force, while the return upward movement of the piston is driven by the negative vacuum between the piston and the top of the cylinder. The arrangement shown in Figures 3 to 7 is driven by a combination of a spring and an electromagnetic force to move the piston. Of course, the piston 305 can also be completely driven only by electromagnetic force (as shown in FIG. 8 ). If the liquid release valve 315 is driven by electromagnetic force (as shown in Figures 1 and 3), its control signal must be coordinated with the piston control signal. Figure 2 shows two templates for the control signals. If the release valve 315 is opened and closed more than once during a downward stroke of the piston 305, a higher precision dose can be obtained. The switch of the liquid release valve 315 can also be driven by the pressure of the liquid/gas without the need for electromagnetic signals to control (as shown in Figures 4-8). In this case, the release valve 315 remains closed during the entire operating cycle of the piston 305 under the combined action of a spring (not shown) and air pressure until the liquid needs to be released at the end, i.e. due to the piston 305 reaching the dose line 350. At this time, the pressure of the liquid chamber 320 increases enough to overcome the double resistance of the spring acting on the release valve 315 and the air pressure on the inner wall of the air delivery pipe to open the release valve 315 and release the liquid into the air delivery pipe 450 .

When the engine is shut down, the three-way valve 330 turns to the liquid circuit and includes the liquid supply pipe 33, the liquid circuit 340 and the air supply in the liquid cylinder, and the liquid in the pipeline is driven back to the liquid source under the pressure of the compressed air, such as a liquid storage tank (Fig. (not shown in the figure), the piston 305 continues to run several times to clean the metering pump and the liquid/gas channel from the metering pump to the nozzle (not shown in the figure). After the cleaning is completed, the three-way valve 330 turns to the original position (normal working position), stops supplying gas to the liquid circuit, and prepares for the next start. In fact, the three-way valve 330 can also be replaced by a two-way valve 332 (as shown in FIGS. 6 and 7 ).

The device shown in Figure 3 is similar to that shown in Figure 1, except that the piston 305 is driven by a combination of spring and electromagnetic force. For example, the electromagnetic force drives the piston down, while the spring drives the piston up, or vice versa.

Figure 4 shows another version of the device. Wherein, the valve 360 installed on the piston 305 and the release valve 315 are both one-way valves, whose opening and closing are controlled by the flow direction and pressure of the liquid. When the piston moves upward, the liquid opens the one-way valve 360 on the piston and injects into the liquid chamber 320 through the piston 305 . When the piston 305 crosses the dose line 350 to overfill, liquid also fills the lower chamber 320 via the return groove 342 at the same time. When the piston moves downward, the liquid is drawn into the upper liquid chamber 322 through the top of the liquid cylinder, and the excess liquid in the lower liquid chamber is driven back to the liquid source through the return groove 342 and the return channel 340 . When the piston reaches the dose line 350, the dose is ready. The liquid release valve 315 is a one-way valve containing a spring (simplified and not shown in the figure). It remains closed under the combined action of its spring and the compressed air in the air delivery tube 450 throughout the reciprocating cycle of the piston until the piston reaches the dose line 350 . When the piston reaches the dose line 350, the liquid in the liquid chamber 320 leaves only one outlet of the release valve 315. If the driving force is large enough to overcome the resistance of the release valve spring and the compressed air, the piston will continue to move downward, forcing the release valve 315 to open, and the liquid in the liquid chamber 320 will be discharged from the cylinder through the release valve 315. The device shown in FIG. 5 is similar to the device shown in FIG. 4 , except that a check valve 310 is installed on the top of the liquid cylinder to prevent the liquid in the cylinder from flowing back from the top and improve the filling efficiency of the lower liquid chamber 320 .

Figure 6 shows another version of the device. The diameter of the upper liquid chamber 322 is slightly larger than that of the lower liquid chamber 320; correspondingly, the diameter of the upper part of the piston is also slightly larger than that of the lower part. When the piston 305 moves downward from the top of the hydraulic cylinder, under the action of hydraulic pressure, the liquid release valve 315 and the one-way restrictor valve 370 are opened, the one-way valve 360 on the piston is closed, and the piston transfers a fixed amount of fluid in the lower liquid chamber 320 The liquid is discharged out of the liquid cylinder through the release valve 315 , and at the same time, fresh liquid is sucked into the upper liquid chamber 322 . Since the diameter of the upper liquid chamber is larger than that of the lower liquid chamber, more liquid is drawn in than discharged. In this way, even if for some reason, the liquid drawn into the upper liquid chamber 322 can be guaranteed to be more than the required dose, that is, the volume of the lower liquid chamber, even if the upper liquid chamber 322 is not fully filled. The volume of the lower chamber 320 is determined by the space between the bottom of the piston and the bottom of the cylinder. When the piston moves to the top, the volume of the lower liquid chamber 320 reaches the maximum, which is the dose released by the piston every reciprocating operation, that is, the unit dose of the metering pump. When the piston moves upwards, the liquid release valve 315 and the one-way restrictor valve 370 are closed, the one-way valve 360 is opened, and the liquid flows from the upper liquid chamber to the lower liquid chamber under the pressure generated by the piston and fills the lower liquid chamber. However, since the diameter of the upper liquid chamber 322 is larger than that of the lower liquid chamber 320 and the liquid is incompressible, the liquid in the upper liquid chamber will be returned to the liquid supply pipe 33 in addition to being used to fill the lower liquid chamber. This requires a drain (return) passage to allow the liquid to flow back from the upper liquid chamber 322 to the liquid supply pipe 33 when the valve 370 is closed. The channel can be formed in many ways, for example, a small hole or a small groove can be opened at any position between the valve 370 (valve or valve seat) or the upper liquid chamber 322 and the return channel 340, allowing a small amount of liquid to flow through. The size of the hole (or groove) needs to be appropriate, so that the upper liquid chamber can generate a certain pressure to help the lower liquid chamber to be effectively filled, and can not form excessive resistance to the movement of the piston. If the diameter of the upper liquid chamber is designed to be larger than the lower liquid chamber, the one-way flow limiting valve 370 can be removed (as shown in Figure 7), and the liquid is directly returned from the inlet. At this time, the liquid inlet and the return port are the same.

In fact, the functions of the device shown in FIG. 6 can also be realized by two or more independent cylinders and pistons under coordinated control signals and driving forces. For example, the cylinder body in FIG. 6 can be two independent cylinder bodies up and down to facilitate processing. The piston can also be two separate pistons.

The device shown in Fig. 7 is similar to the device shown in Fig. 6, but the cylinder body has two grooves, that is, the upper and lower liquid chambers have a liquid return groove 342 and 344. The upper liquid tank 344 is used to drive excess liquid back to the liquid supply pipe 33 at the initial stage of the upward movement of the piston. When the bottom of the piston is higher than the lower liquid tank 342, the liquid will return from the lower liquid tank 342. In this design, valve 370 is a one-way valve with no liquid return path.

In all the variations above, the three-way valve 330 or the two-way on-off valve 332 can be integrated with the metering pump as a device, or can be used as a separate device connected to the metering pump through pipelines.

In fact, the functions of the devices shown in Figure 1 and Figures 3-8 can also be realized by two or more independent cylinders and pistons under coordinated control signals and driving forces. For example, as shown in Figure 9, a similar effect can also be achieved by placing a piston in two independent cylinders up and down. In this device, the two pistons can move upwards controlled by a synchronous control signal. At this time, the liquid release valve 315 is opened, the large liquid cylinder draws liquid, and the small liquid cylinder releases liquid. The dose is determined by the volume of the small cylinder. After the release of the liquid in the small liquid cylinder is completed, the liquid release valve 315 is closed, and the large piston moves downward under the action of the spring, and the liquid flows from the large liquid cylinder to the small liquid cylinder, and the small piston moves downward to the bottom of the cylinder under the action of hydraulic pressure. Of course, the two liquid cylinders can also be of the same diameter, and the same effect can be achieved with two pistons with different strokes, that is, the liquid drawn is always slightly more than the required dose. Surplus liquid can stay in the cylinder that is responsible for extracting (being above) so that use next time, so that the stroke of extracting piston can be shorter next time like this. The result is that the filling of the (lower) constant dose liquid cylinder is guaranteed by adjusting the liquid volume in the extraction cylinder. Another method is to open a liquid return channel to return excess liquid.

Figure 10 shows that the air delivery tube narrows at the metering pump release valve 315, which increases the velocity of the air flow there, thereby reducing the pressure on the release valve 315 using the Venturi effect and reducing the energy required to drive the piston 305. Figure 11 shows another similar example of using the Venturi principle to reduce the air pressure at the relief valve. The liquid-gas mixture can be directly sprayed into the engine exhaust pipe and further atomized through the mixer, or it can be sprayed into the engine exhaust pipe through the nozzle (Figure 10).

What is described herein is only one form of the invention. However, the present invention includes many different variants. Each specific detail can have an infinite number of different forms, combinations or arrangements, which are not described here. Any modification to the present invention or adoption of different methods, combinations and arrangements of methods, and the results thereof still fall within the scope of the present invention.

Claims (10)

1. A metering delivery method for extracting, metering and releasing liquid, characterized in that the steps are as follows: 1) Excessive withdrawal of more fluid than the required dose as determined by a fixed volume container, 2) adjusting the withdrawn fluid to the dose while returning excess fluid to the fluid source, and 3) Release the dose of liquid. 2. A metering delivery method for extracting, metering and releasing liquid, characterized in that the steps are as follows: 1) using at least one container to draw and store more than the required dose of liquid, 2) preparing the dose by filling the liquid into at least one additional container of fixed volume, and 3) Release the fixed volume dose of liquid. 3. A metering pump for pumping, metering and releasing liquid, characterized in that it comprises: a) at least one chamber communicating with at least one outlet, at least one inlet and at least one return port; b) at least one valve is connected to the inlet through which the liquid enters the chamber; c) at least one valve is connected to the outlet through which the liquid is released to the outside; d) At least one piston is placed in the chamber for reciprocating motion, at least to accomplish the following tasks: pump more liquid into the chamber than the required dose, adjust the pumped liquid to the dose determined by a certain space in the chamber with a fixed volume, and simultaneously drain the excess the liquid is returned to the liquid source through the return port, the dose of liquid is released through the outlet port, and e) At least one drive means reciprocates the piston. 4. The metering pump for extracting, measuring and releasing liquid according to claim 3, characterized in that: the valve is a non-electrically driven or electrically driven valve. 5. The metering pump for pumping, metering and releasing liquid according to claim 3, characterized in that the piston is driven by electromagnetic force and mechanical energy storage device. 6. The metering pump for pumping, metering and releasing liquid according to claim 3, characterized in that said piston is completely driven by electromagnetic force. 7. The metering pump for pumping, measuring and releasing liquid according to claim 3, characterized in that: the inlet and the return port of the device are the same. 8. The metering pump for extracting, measuring and releasing liquid according to claim 3, characterized in that: the inlet and the return port are different ports. 9. A metering pump for pumping, metering and releasing liquid, characterized in that it comprises: a) At least two chambers, the two chambers are connected by a one-way flow valve, one of which is used for drawing and storing liquid, contains at least one inlet connected to the liquid source through a valve; the other is used for metering liquid, contains at least one inlet and the pumping chamber is connected, and at least one outlet is connected to the liquid release valve, b) At least one piston is placed in each of the above two chambers for reciprocating motion: when the piston of the extraction chamber moves to a certain direction, the liquid is pumped into the chamber, and when it moves to the other direction, the liquid is injected into the dosing chamber; preparing a dose of fluid when moving in one direction and releasing that dose when moving in the other direction, and c) at least one drive means for reciprocating said piston. 10. The metering pump for extracting, metering and releasing liquid according to claims 3-9, characterized in that the fluid delivery pipe with a changed cross section uses the Venturi effect to reduce the resistance of the metering device to release another stream of fluid to the delivery pipe .

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