JP4483952B2 - Pump with motor - Google Patents

Description

  The present invention relates to a motor-equipped pump including an electric motor unit that drives a pump unit.

  In recent years, selective catalytic reduction (SCR) type urea SCR systems that reduce NOx (nitrogen oxides) in exhaust gas are being developed in internal combustion engines (particularly diesel engines) applied to automobiles and the like. Some have been put to practical use.

In this urea SCR system, a selective reduction type NOx purification catalyst (SCR catalyst) is provided in an exhaust pipe of an internal combustion engine, and urea water (urea aqueous solution) as a reducing agent is added to the exhaust pipe upstream thereof. A water addition valve is provided. In such a system, urea water is added to the exhaust pipe by the urea water addition valve, whereby urea water is supplied to the NOx purification catalyst together with the exhaust gas, and the exhaust gas is purified by a NOx reduction reaction on the NOx purification catalyst. The At the time of NOx reduction, ammonia (NH3) is generated by hydrolyzing urea water with exhaust heat, and NOx is selectively reduced by ammonia in the NOx purification catalyst even in an environment with a high oxygen concentration. Purification will be performed (see Patent Document 1).
Japanese translation of PCT publication No. 2004-510093

  Such a urea SCR system requires a urea water pump that pumps urea water stored in a tank to a urea water addition valve. The inventors tried to adopt a conventional general motor-equipped pump for the urea water pump. The motor-equipped pump includes a pump unit that pumps liquid and an electric motor unit that drives the pump unit.

  However, it has been found that when the conventional pump with a motor is used as it is as a urea water pump, the corrosion of the winding described below becomes a problem.

  The winding is provided on a stator or a rotor constituting the pump unit, and generates a magnetic field by energization. A conventional general winding is an electric conductor made of copper and an insulation covering the electric conductor. Consists of the body. Further, the conventional motor-equipped pump has a structure in which the entire stator or rotor is covered with resin (coating resin) so that the winding does not corrode due to the liquid pumped by the pump unit. Further, the urea water easily penetrates into the coating resin and the insulator as compared with simple water, and also easily corrodes the copper electric conductor, so that it has been found that a countermeasure for corrosion of the winding is newly required.

  Such a problem of winding corrosion is not limited to urea water, but can also occur in other liquids other than water. For example, in recent years, alcohol, biofuel, and the like are sometimes used as fuel for internal combustion engines for vehicles, and even in a pump with a motor that pumps such fuel to a fuel injection valve, the fuel penetrates the coating resin and the insulator. There is a concern that the copper electrical conductor is corroded.

The present invention has been made in order to solve the above-described problems, and an object of the present invention is to provide a motor-equipped pump having an electric motor unit that drives the pump unit, and the winding corrodes due to urea water pumped by the pump unit. It is providing the pump with a motor which aimed at suppression of doing.

  Hereinafter, means for solving the above-described problems and the operation and effects thereof will be described.

The invention according to claim 1 is a pump with a motor that is mounted on a vehicle having an internal combustion engine and pumps urea water for reducing nitrogen oxides contained in the exhaust gas of the internal combustion engine, and pumps urea water. and parts, are arranged in a flow passage for circulating the urea water to be pumped from the pump unit, an electric motor for driving the pump section, provided at least one of the stator and rotor constituting the electric motor, energized A winding for generating a magnetic field by
A part of the flow path is formed by a gap on a magnetic circuit formed between the stator and the rotor, and the winding covers the electric conductor to be energized and the electric conductor. The electrical conductor is mainly composed of carbon.

When the electric motor unit is arranged in the flow passage, there is a concern that the winding of the electric motor unit is corroded by urea water pumped from the pump unit, but the electric conductor of the winding according to the present invention is mainly composed of carbon. It is said. Then, the carbon, together with the electric resistance is equal to the copper, corrosion resistance against the urea water is higher than that of copper. Therefore, the coil | winding which concerns on this invention can improve corrosion resistance, without increasing electrical resistance compared with the coil | winding by the conventional copper electrical conductor.
Furthermore, the invention according to claim 1 is mounted on a vehicle having an internal combustion engine and is applied as means for pumping urea water for reducing nitrogen oxides contained in exhaust gas of the internal combustion engine. When such urea water is used as an object, the electrical conductor according to the present invention containing carbon as a main component is preferable because the corrosion resistance is remarkably improved as compared with a conventional copper electrical conductor. In addition, in the case of a motor-equipped pump mounted on a vehicle having an internal combustion engine in this way, heat resistance is required for the electric conductor because it is in a high temperature environment, but the heat resistance of carbon is equivalent to that of copper. Therefore, the above requirement can be satisfied.

  As a specific example of the electrical conductor whose main component is carbon, as in the invention according to claim 2, electricity is produced by a wire constituted by spinning carbon nanotubes alone or a wire constituted by holding carbon nanotubes with a binder. Forming a conductor. Specific examples of the binder include rubber and resin.

  Carbon nanotubes are preferably produced by using carbon fibers as a base material, and wires are formed by spinning carbon fibers alone instead of carbon nanotubes, or wires formed by holding carbon fibers with a binder. The electrical conductor may be formed by

  The invention according to claim 3 is characterized in that the electric conductor is formed in a wire shape by twisting a plurality of wires formed mainly of carbon. According to this, the strength of the winding can be improved by improving the strength of the electric conductor. In particular, in the manufacturing process in which the winding is wound around the core member constituting the electric motor unit, the winding is required to have a tensile strength that can withstand the tension when winding the winding while applying a tension. Therefore, the effect of improving the winding strength as described above is preferably exhibited.

  The motor-equipped pump according to any one of claims 1 to 3, wherein a fuel pump mounted on a vehicle having an internal combustion engine and pumping fuel in a fuel tank to a fuel injection valve provided in the internal combustion engine. You may make it apply.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.

  The motor-equipped pump according to the present embodiment is applied to a urea water pump that pumps a urea aqueous solution (hereinafter simply referred to as urea water) using urea as a reducing agent, and urea water discharged from the urea water pump. Is pressurized and fed to the addition valve. The addition valve is disposed so as to inject urea water into an exhaust flow in an exhaust passage of a diesel engine (hereinafter referred to as an engine) as an internal combustion engine.

  FIG. 1 is an overall configuration diagram showing the overall configuration of the urea SCR system in the present embodiment. This overall configuration diagram shows an exhaust emission control device for purifying exhaust gas discharged from an engine of an automobile (not shown). The configuration of the exhaust purification device is roughly classified into an exhaust system component, a urea water supply system component, and a control system component.

  The constituent parts of the exhaust system are arranged in order from the exhaust upstream side, DPF1 (Diesel Particulate Filter), exhaust pipe 2 (upstream exhaust passage of the catalyst), catalyst 3, and exhaust pipe 4 (downstream exhaust of the catalyst) Passage). The DPF 1 is a continuously regenerating PM removal filter that collects PM (Particulate Matter, particulate matter) in exhaust gas, and repeatedly collects and removes the collected PM by, for example, post injection after main fuel injection ( This is equivalent to the regeneration process of the PM removal filter). Further, the DPF 1 carries a platinum-based oxidation catalyst (not shown) and can remove HC and CO together with a soluble organic component (SOF) which is one of the PM components.

The catalyst 3 is a part that promotes a reduction reaction of NOx and purifies exhaust gas.
4NO + 4NH3 + O2 → 4N2 + 6H2O (Formula 1)
6NO2 + 8NH3 → 7N2 + 12H2O (Formula 2)
NO + NO2 + 2NH3 → 2N2 + 3H2O (Formula 3)
Such a reaction is promoted to reduce NOx in the exhaust. In these reactions, an aqueous solution (hereinafter referred to as urea water) containing ammonia (NH 3) serving as a NOx reducing agent is mixed with exhaust gas and supplied to the catalyst 3. Specifically, urea water is injected and supplied by an addition valve, which will be described later, toward the exhaust gas flowing through the exhaust pipe 2 on the upstream side of the catalyst 3.

  The components of the urea water supply system include a urea water supply unit 5, an addition valve 6, a delivery pipe 7, and the like. The urea water supply unit 5 includes a urea water tank 8, a urea water pump 9 (a pump with a motor), and the like. I have. The urea water tank 8 is constituted by a sealed container with a liquid supply cap, and urea water having a predetermined concentration is stored therein. In the present embodiment, an in-tank type in which the urea water pump 9 is disposed in the urea water tank 8 is adopted.

  The urea water pump 9 is an electric pump that is rotationally driven by a drive signal from an ECU 10 (control means) that is an electronic control unit. When the urea water pump 9 is driven, the urea water in the urea water tank 8 is sucked into the urea water pump 9 through the strainer 9a and the filter 9b and is pressurized and sent. Thereafter, the discharge pressure is adjusted by the regulator 9 c and then supplied to the addition valve 6 through the delivery pipe 7. Note that the urea water pump 9, the filter 9b, the regulator 9c, and the like are accommodated in a unit case 9d and unitized. When the supply pressure from the urea water pump 9 exceeds the set value of the regulator 9c, the urea water in the delivery pipe 7 is returned to the urea water tank 8 by the regulator 9c.

  An injection port is formed at the tip of the addition valve 6. When the needle valve that opens and closes the injection port is opened by an electromagnetic actuator, the urea water supplied to the addition valve 6 by driving the urea water pump 9 is fogged. Is injected into the exhaust pipe 2. When urea water is added and supplied in this way, urea water is supplied to the SCR catalyst 3 together with the exhaust gas in the exhaust pipe 2, and the exhaust gas is purified by the NOx reduction reaction in the SCR catalyst 3. Composed.

When reducing NOx, for example,
(NH2) 2CO + H2O → 2NH3 + CO2 (Formula 4)
By such a reaction, urea water is hydrolyzed by exhaust heat. As a result, ammonia (NH3) is generated, and this ammonia is added to the NOx in the exhaust gas selectively adsorbed by the SCR catalyst 3. Then, a reduction reaction based on the ammonia (the above reaction formulas (Formula 1) to (Formula 3)) is performed on the catalyst 3, whereby NOx is reduced and purified.

  Next, the single-piece | unit structure of the urea water pump 9 is demonstrated in detail using FIGS.

  As shown in FIG. 2, the urea water pump 9 includes a pump unit 18 that pumps urea water and an electric motor unit 19 that drives the pump unit 18. The pump unit 18 is a vortex pump including a pump case and an impeller 22. The pump case joins two members, the upper case 20 and the lower case 21, and forms a space as a pump chamber inside the mating surface to be joined. An impeller 22 is rotatably accommodated in the pump chamber. When the impeller 22 is rotated, the urea water in the urea water tank 8 is sucked from the suction port 24 provided in the lower case 21 and then boosted in the pump chamber and is pumped to the electric motor unit 19 described later.

  It is desirable to employ a material having corrosion resistance and oxidation resistance to urea water for a member having a portion through which urea water flows in the urea water pump 9. The upper case 20 and the lower case 21 are made of metal, and are made of, for example, austenitic stainless steel as a passive film regenerating material in view of the above-described corrosion resistance and oxidation resistance. is there. The impeller 22 is formed of a resin (for example, a phenol resin).

  The electric motor unit 19 is a brushless motor including a stator 25, a rotor 26, and the like, and functions to generate a driving force that is energized to pump urea water. As shown in FIG. 3A, which is a cross-sectional view taken along the line II in FIG. 2, the stator 25 is configured by arranging six divided cores 25a (core members) in the circumferential direction. Each divided core 25a is integrally formed by laminating magnetic steel plates provided with an insulating film in the rotation axis direction (vertical direction in FIG. 2). A bobbin 28 formed of an insulating material such as resin is attached to each divided core 25a (see FIGS. 2 and 3B).

  The winding 29 is concentratedly wound (or distributedly wound) on the outer periphery of the bobbin 28 for each divided core 25a, and is electrically connected to the terminal 43 on the end cover 37 side shown in FIG. The winding 29 is divided into three types of U phase, V phase, and W phase. Switching from the terminal 43 to the winding 29 of each phase is controlled by switching by the ECU 10. As a result, a magnetic pole is generated in the winding 29 of each phase. Therefore, the gap between the inner peripheral surface of the stator 25 and the outer peripheral surface of the rotor 26 functions as the flow path 38 as described above, and also functions as a gap on the magnetic circuit between the stator 25 and the rotor 26.

  The permanent magnet 31 is a plastic magnet formed into a cylindrical shape by kneading magnetic powder into a thermoplastic resin material such as PPS, and is directly formed on the outer periphery of the rotating shaft 27 by injection molding or the like. As shown in FIG. 3A, the permanent magnet 31 forms eight magnetic pole portions in the rotation direction. These magnetic pole portions are magnetized so as to form different magnetic poles alternately in the rotation direction on the outer peripheral surface facing the stator 25.

  FIG. 4 is a longitudinal sectional view showing the stator 25 and the insulating resin material 45 for molding the stator 25. As shown in FIG. 4, the plurality of divided cores 25 a, the windings 29 of each phase, and the terminal 43 are integrally molded by resin molding with an insulating resin material 45. The insulating resin material 45 also covers the inner peripheral surface of the split core 25a. On the other hand, the permanent magnet 31 is also covered with an insulating resin material. That is, strictly speaking, the above-described flow passage 38 is formed between the inner peripheral wall portion 45a of the insulating resin material 45 and the outer peripheral wall portion 31a of the insulating resin material 31 (see FIG. 3B). Incidentally, reference numeral 45 b in FIG. 3B indicates an outer peripheral wall portion of the insulating resin material 45.

  The housing 36 serves as both the housing of the pump unit 18 and the electric motor unit 19. The housing 36 is made of metal, and is formed by caulking the lower case 21 and the end cover 37 at both ends in the axial direction. The upper case 20 is abutted against the step 36 a of the housing 36 in the axial direction. Thereby, the upper case 20 is positioned in the axial direction. The above-described bearing portion 32 is fixed to the center portion of the upper case 20 by press-fitting. The lower case 21 is fixed by caulking at one end side of the housing 36. Due to the axial force generated by the caulking, the upper case 20 and the stepped portion 36a and the lower surface 21 and the upper case 20 are pressed against each other in the axial direction. Secure and seal with urea water.

  The urea water pumped to the electric motor unit 19 side is sent out in the order of the flow passage 38 (see FIGS. 2 and 3B) between the stator 25 and the rotor 26 and the discharge passage 39, and is added from the discharge port 40. Supplied to the valve 6 side. The discharge port 40 of the discharge passage 39 that opens to the outside from the end cover 37 is formed eccentrically with respect to the bearing portion 33.

  The insulating resin material 45 described above is integrally formed with an end cover 37 that covers the end of the stator 25 opposite to the pump portion 18. The end cover 37 is configured by integrally forming a bearing portion 33 that supports the rotary shaft 27, a support portion of the terminal 43, and the discharge port 40 with an insulating resin material 45.

  A check valve 47 and a spring 48 are accommodated in the discharge port 40 formed by the end cover 37. When the urea water increased in pressure by the pump unit 18 exceeds a predetermined pressure, the check valve 47 lifts against the load of the spring 48 and the urea water is discharged from the discharge port 40 to the addition valve 6 side. The check valve 47 is provided so as to prevent a back flow of urea water discharged from the urea water pump 9.

  Next, the structure and material of the winding 29, which is the main part of the present invention, will be described with reference to FIGS.

  The same winding 29 is employed for each of the U-phase, V-phase, and W-phase. The winding 29 includes an electric conductor 29a that is energized and an insulator 29b that covers the electric conductor 29a. It is composed of FIG. 5 is a perspective view showing the end portion of the winding 29, and the tip of the electric conductor 29 a is exposed from the insulator 29 b at the end portion, and this exposed end portion is connected to the terminal 43. Yes.

  As shown in FIG. 6 which is a cross-sectional view of the winding 29, the electric conductor 29a is formed by twisting a plurality of wires 29c into a wire shape. The wire 29c is a material mainly composed of carbon. Specifically, it is configured by spinning carbon nanotubes alone, or is configured by holding carbon nanotubes with a binder. Production of such a wire 29c can be realized by a production method disclosed in Japanese Patent Application Laid-Open Nos. 2007-126318 and 2007-161512.

  The terminal 43 is also preferably formed of a material mainly composed of carbon, and preferably has the same configuration as that of the wire 29c described above (for example, a configuration using carbon nanotubes or carbon fibers). The insulator 29b is made of resin or rubber.

  By the way, when the urea water pump 9 is a pump with a motor, since the urea water pumped by the pump unit 18 circulates in the electric motor unit 19, the electric parts and other various parts of the electric motor unit are made of urea water. There is concern about corrosion. As a countermeasure, in this embodiment, the inner peripheral wall portion 45a is formed on the insulating resin material 45 for molding the stator 25, and the outer peripheral wall portion 31a is formed on the insulating resin material 31 for molding the permanent magnet 31.

  As a result, when the urea water flow passage 38 is formed in the gap between the inner peripheral surface of the stator 25 and the outer peripheral surface of the rotor 26, the electrical components of the stator 25 such as the split core 25a and the winding 29 are transferred to the inner peripheral wall portion 45a. It is avoided that it is covered and directly exposed to the urea water in the flow passage 38. Further, it is avoided that the rotor 26 parts such as the permanent magnet 31 are covered with the outer peripheral wall portion 31 a and directly exposed to the urea water in the flow passage 38. Therefore, it can suppress that the split core 25a, the coil | winding 29, and the permanent magnet 31 corrode with urea water.

  However, the present inventors have obtained the knowledge that the inner peripheral wall portion 45a and the outer peripheral wall portion 31a made of resin swell with urea water, and the urea water easily penetrates into both the wall portions 45a and the wall portion 31a due to this swelling. It was. Furthermore, since the conventional electric conductor 29a used for the coil | winding 29 is generally copper, it turned out that it is necessary to improve corrosion resistance especially about the electric conductor 29a.

  In view of this point, in the present embodiment, the electric conductor 29a is formed of a material mainly composed of carbon. The carbon has the same electrical resistance as copper and higher corrosion resistance to ammonia (NH3) than copper. Further, since the urea water pump 9 is disposed in the engine room of the vehicle, the environmental temperature is high, and the winding 29 is also required to have heat resistance. However, the heat resistance of carbon is superior to copper. Therefore, according to the present embodiment in which carbon is applied to the electrical conductor 29a, the electrical resistance does not increase and the heat resistance does not decrease as compared with the conventional winding made of copper electrical conductor. Corrosion resistance to water can be improved.

  In the present embodiment, since the electric conductor 29a is formed by twisting a plurality of wires 29c into a wire shape, the strength of the winding 29 can be improved by improving the strength of the electric conductor 29a. In particular, in the manufacturing process in which the winding 29 is wound around the split core 25a, the winding 29 is required to have a tensile strength that can withstand the tension when the winding 29 is wound while being tensioned. Therefore, the effect of improving the winding strength as described above is preferably exhibited.

  Furthermore, in the present embodiment, when forming the electric conductor 29a with the wire 29c composed mainly of carbon, the wire 29c of the electric conductor 29a is formed of carbon nanotubes, so that high electrical conductivity is obtained, Can be high strength.

  Further, in forming the electric conductor 29a, if the wire 29c is formed by spinning carbon nanotubes alone, it is higher than that formed by the wire 29c formed by holding the carbon nanotubes with a binder. Electrical conductivity can be obtained and high strength can be achieved.

(Other embodiments)
The above embodiments may be implemented with the following modifications. Further, the present invention is not limited to the description of the above embodiment, and the characteristic structures of the embodiments may be arbitrarily combined.

  In the above embodiment, carbon nanotubes are adopted as the material of the wire 29c forming the electric conductor 29a. However, carbon fibers may be adopted instead of the carbon nanotubes. That is, the wire 29c may be formed by spinning carbon fiber alone, or the wire 29c may be formed by holding the carbon fiber with a binder.

  The wire 29c made of carbon fiber or carbon nanotube may have a shape that continuously extends from one end to the other end of the winding 29 without having a connection portion, or a plurality of wires 29c may be extended from one end of the winding 29. You may form by connecting in the middle to the other end.

  In the above embodiment, the motor-equipped pump according to the present invention is applied to the urea water pump, but the present invention is not limited to such a urea water pump, and is mounted on a vehicle having an internal combustion engine, for example. When the fuel in the fuel tank is pumped to the fuel injection valve that injects fuel into the combustion chamber or the intake pipe of the internal combustion engine, the motor-equipped pump according to the present invention may be applied to the fuel pump that pumps the fuel. . Alternatively, in the internal combustion engine in which hydrocarbon (HC) is added as a reducing agent instead of adding urea water as a reducing agent to the exhaust, the present invention relates to a pump that pumps the hydrocarbon to an addition valve. You may make it apply a pump with a motor.

  In the above embodiment, the stator 25 is for a motor-equipped pump having a winding 29, and the electric conductor 29a of the stator-side winding 29 is made of carbon, but the rotor is a motor-equipped pump having a winding. The electrical conductor of the winding on the rotor side may be made of carbon.

The figure which shows the whole urea SCR system structure to which the urea water pump (pump with a motor) which concerns on one Embodiment of this invention was applied. Sectional drawing which shows the detailed structure of the urea water pump of FIG. (A) is II sectional drawing of FIG. 2, (b) is an enlarged view of (a). The longitudinal cross-sectional view which shows the stator of FIG. 3 and the insulating resin material which molds the stator. The perspective view which shows the edge part of the coil | winding which concerns on FIG. Sectional drawing of the coil | winding which concerns on FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 9 ... Urea water pump (pump with a motor), 18 ... Pump part, 19 ... Electric motor part, 25 ... Stator, 26 ... Rotor, 29 ... Winding, 29a ... Electric conductor, 29b ... Insulator, 29c ... Wire material.

Claims (3)

A motor-equipped pump that is mounted on a vehicle having an internal combustion engine and pumps urea water that reduces nitrogen oxides contained in the exhaust gas of the internal combustion engine,
A pump unit that pumps urea water ;
An electric motor unit that is disposed in a flow path for circulating urea water pumped from the pump unit and drives the pump unit;
Windings that are provided on at least one of the stator and the rotor constituting the electric motor unit and generate a magnetic field by energization;
With
A part of the flow path is formed by a gap on a magnetic circuit formed between the stator and the rotor,
The winding is composed of an electric conductor to be energized and an insulator covering the electric conductor,
A motor-equipped pump, wherein a main component of the electric conductor is carbon.   2. The motor-equipped pump according to claim 1, wherein the electric conductor is formed of a wire configured by spinning carbon nanotubes alone or a wire configured by holding carbon nanotubes with a binder. 3. .   The pump with a motor according to claim 1 or 2, wherein the electric conductor is formed in a wire shape by twisting a plurality of wires made of carbon as a main component.

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