Methods for generating particles and particle generator

Abstract

Method for generating particles (P) of a particle generator (1), characterized by the use of the particles generated by a commutator motor (2).

Description

[0001] The invention relates to a method for generating particles of a particle generator according to the preamble of claim 1 and to a particle generator according to claim 8.

[0002] The range of applications for particle generators is very broad. Particle generators are used, for example, for air humidification, powder extraction, vacuum drying, and medical inhalation therapy. They are also used in experimental aerodynamics when tracer or light-scattering particles must be added to a wind tunnel for laser nemometry studies. The most important operating parameters of a particle generator are the generation rate and the particle size spectrum, including the mean particle diameter.

[0003] In further application, for example, the calibration or validation of particle measuring devices could be carried out with particles that have similar properties in terms of shape, size, density, surface texture and refractive index to the aerosol actually to be measured, e.g. diesel soot.

[0004] DE 10 2006 000 315 A1 discloses the subject matter of the preamble of claim 8.

[0005] US 6 097 128 A describes a dust cover for a universal motor comprising a device with an opening for receiving a brush. Extending from this device is a shroud that surrounds the part of the commutator in contact with the brush. A passage connects the interior of the shroud to a cooling airflow through the motor, so that dust generated by brush wear on the commutator is directed through the passage into the airflow and away from the bearing holder. The shroud also has oil reservoirs that capture and retain some of the carbon dust particles by capillary action, thereby reducing dust accumulation.

[0006] EP 0 353 746 B1 describes a device for generating a solid aerosol, in particular a carbon aerosol, which is used for calibrating measuring devices, filter tests, and inhalation experiments. The device uses two electrodes with parallel end faces that can be guided axially against each other. Between these electrodes, electrode material is vaporized by high-voltage sparks, which subsequently condense into aerosol particles. A flow of an inert gas such as argon carries the generated aerosol particles. The breakdown voltage between the electrodes is measured and serves to regulate the synchronous advance of the electrodes to ensure a constant particle concentration. The electrodes are driven by spindles with opposing threads, which ensures uniform guidance and thus even combustion of the electrodes.

[0007] The object of the invention is to provide an improved and, in contrast to the prior art, simplified method for generating particles and a simplified particle generator for generating particles.

[0008] This object is achieved according to the invention by a method having the features of claim 1 and a particle generator having the features of claim 8.

[0009] Further advantageous features are contained in the subclaims.

[0010] According to the invention, the method for generating particles in a particle generator provides for the use of particles generated during operation by a commutator motor. Preferably, the use of particles generated by mechanical abrasion during grinding of the brushes of the commutator motor on its commutator can also be provided. The creation or generation of the particles thus occurs essentially purely mechanically. One advantage of the newly developed method for generating particles is that, due to the very slow wear of the brushes, long-lasting and constant reproducibility of the particles, and in particular of the particle number, can be expected.

[0011] One embodiment provides for the use of particles generated by sparking when the energized brushes of the commutator motor grind on its commutator.

[0012] Another embodiment provides for a particle concentration that can be varied by changing the load and / or speed of the commutator motor. For example, the pressure with which the brushes are applied to the commutator can be a variable indicator of particle generation.

[0013] Preferably, the particles emerging from a particle outlet can be specifically fed to a particle counter for calibration or validation. This can be done by providing temporary or continuous measurement.

[0014] State-of-the-art particle counters can be used as particle counters.

[0015] The size, size distribution, or number of particles can be further influenced by supplying cooling air to the commutator motor. This means that instead of a fan normally present in the motor housing, connection nozzles can be provided through which cooling air can enter the housing.

[0016] The method further provides for conveying the particles to the particle outlet opening by a fan, in particular a motor fan on the motor shaft of the commutator motor. Continuous or temporary conveying can also be provided here.

[0017] According to the invention, the particle generator for generating particles comprises a commutator motor integrated with the particle generator. The structure and function of a commutator motor are well known. Typically, commutator motors comprise a rotating commutator and stationary brushes. The commutator is provided with circumferential lamellae on which the brushes are abraded. The lamellae can be made of copper; the brushes of graphite. The particles generated by abrasion can be guided through suitable means for the calibration or validation of particle measuring devices or for soot measurement.

[0018] According to the invention, a particle outlet opening is provided on the commutator side, leading to a measuring device. The generated particles can exit through this outlet opening.

[0019] One embodiment of the particle generator provides a fan assembly located at the motor end facing away from the commutator, which conveys the particles to the particle outlet opening. This fan assembly, in particular, has a fan wheel mounted on the corresponding motor shaft end. This fan wheel serves both to transport the particles toward the particle outlet opening and to cool the commutator motor. A separate cooling air supply is also conceivable. This allows for influencing the particles, for example, with regard to size, size distribution, and number.

[0020] The particle generator can have an air inlet on the fan side, preferably equipped with a particle filter. If the particles contained in the room or ambient air are to be excluded, the supplied air can be cleaned by a highly efficient particle filter. Furthermore, it is conceivable that gases (e.g., N2) or synthetic air (a gas mixture of nitrogen and oxygen) or similar could be used as a cooling medium instead of air.

[0021] Further advantages, features, and details of the invention will become apparent from the following description, which describes an exemplary embodiment of the invention with reference to the drawing. The features mentioned in the claims and in the description may be essential to the invention individually or in any combination. The invention is explained in more detail below with reference to the sole drawing.

[0022] The only Fig. 1 shows the essential components of a schematically represented particle generator 1.

[0023] The particle generator 1 comprises a commutator motor 2 with an internal commutator 3 and energizable brushes 4, 5 contacting the commutator. The commutator motor 2 further comprises a drive shaft A on which the commutator 3, a rotor 6, and a fan wheel 7 are arranged. The rotor 6 is surrounded by a stator 8.

[0024] Furthermore, an air inlet opening 11 equipped with a particle filter 10 is provided on the fan side. The introduced air L serves, on the one hand, to cool the motor components and, on the other hand, to transport the particles P toward a provided particle outlet opening 12. The particles P are generated, on the one hand, by the operational use of the commutator motor 2 and, on the other hand, by the grinding of the brushes 4, 5 on its commutator 3. Thus, a particle concentration PK is present, generated by mechanical abrasion.

[0025] The mechanically generated particle concentration PK can be fed via the particle outlet opening 12 by means of a hose connection or the like, e.g. to a particle counter for calibration or validation.

[0026] Particles P generated by sparking during the grinding of the energized brushes 4, 5 of the commutator motor 2 on its commutator 3 essentially only occur when the brushes 4, 5 and the windings are energized simultaneously. Furthermore, abrasion can also occur during rotation without energization, but in this case, the integration of an external drive would be necessary.

[0027] Both the method and the device according to the invention can also be used for soot measurement, for example, in motor vehicles. No special adaptation is required.

Claims

[1] Method for generating particles (P) of a particle generator (1), characterized by Use of the particles generated by a commutator motor (2). [2] Method according to claim 1, characterized by Use of the particles (P) generated by mechanical abrasion during grinding of the brushes (4, 5) of the commutator motor (2) on its commutator (3). [3] Method according to claim 1 and / or 2, characterized by Use of the particles (P) generated by sparking when the energized brushes (4, 5) of the commutator motor (2) grind on its commutator (3). [4] Method according to at least one of the preceding claims, characterized by a particle concentration (PK) that can be varied by changing the load and / or speed of the commutator motor (2). [5] Method according to at least one of the preceding claims, characterized bya targeted supply of the particles (P) emerging from a particle outlet opening (12) via a particle counter with calibration or validation. [6] Method according to claim 5, characterized by that cooling air is supplied to the commutator motor (2). [7] Method according to at least one of the preceding claims, characterized by conveying the particles (P) to the particle outlet opening (12) by a fan, in particular a motor fan on the motor axis of the commutator motor (2). [8] Particle generator for generating particles, in particular according to the method of one of the preceding claims, with a commutator motor (2) integrated into the particle generator (1), characterized by a particle outlet opening (12), in particular on the commutator side, leading to a measuring device. [9] Particle generator according to claim 8, characterized bya fan arrangement which conveys the particles (P) to the particle outlet opening (12) and is arranged at the motor end facing away from the commutator (3), in particular a fan wheel (7) fastened to the corresponding motor shaft end. [10] Particle generator according to claim 9, characterized by an air inlet opening (11) on the fan side, preferably equipped with a particle filter (10).

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