DE102016213637A1 - Particle sensor with protective element against contamination - Google Patents

Abstract

The invention relates to a particle sensor (100) for detecting a quantity of particles in a gas stream in an internal combustion engine. The particle sensor (100) has a housing (110), in which a measuring area (120) is arranged, an at least partially in the measuring area (120) arranged and substantially cylindrical sensor electrode (130) extending over the second housing portion (118) extending from the measuring region (120), and an electrically non-conductive protective element (160) attached to the sensor electrode (130) and adapted to at least partially prevent the gas flow at the second housing region (118) from the measuring range (120). 120) flows out.

Description

The present invention relates to a particle sensor for detecting a particle amount in a gas flow in an internal combustion engine, in particular a particle sensor with a protective element against internal contamination.

The reduction of exhaust emissions in motor vehicles is an important goal in the development of new motor vehicles. Therefore, combustion processes in internal combustion engines are thermodynamically optimized, so that the efficiency of the internal combustion engine is significantly improved. In the automotive sector diesel engines are increasingly used, which, with modern design, have a very high efficiency. The disadvantage of this combustion technique over optimized Otto engines, however, is the emission of soot or particles. The soot or the particles is particularly because of the polycyclic aromatics strongly carcinogenic, which has already been reacted in various regulations. For example, exhaust emission standards with maximum limits for soot emissions were issued. In order to meet the exhaust emission standards nationwide for motor vehicles with diesel engines, there is a need to produce low-cost sensors that reliably measure the soot content in the exhaust stream of the motor vehicle.

The use of such soot sensors is used to measure the currently expelled soot or particulate amount, so that the engine management in a motor vehicle in a current driving situation information to reduce with regulatory adjustments to reduce emissions. In addition, with the help of the soot sensors active exhaust gas purification can be initiated by exhaust soot filter or an exhaust gas recirculation to the engine. In the case of soot filtering, regenerable filters, such as particulate filters, are used which filter and trap a substantial portion of the soot content from the exhaust. Soot sensors are required for the detection of soot in order to monitor the function of the soot filters or to control their regeneration cycles. For this purpose, the soot filter, which is also referred to as a diesel particulate filter, a soot sensor before and / or -nachgeschaltet.

The soot or particle sensor upstream of the particulate filter serves to increase system safety and to ensure operation of the particulate filter under optimum conditions. Since this depends to a great extent on the amount of particulates stored in the particulate filter, accurate measurement of the particulate concentration upstream of the particulate filter system, in particular the determination of a high particulate concentration upstream of the particulate filter, is of great importance.

A soot or particle sensor arranged downstream of the particle filter offers the possibility of making an on-board diagnosis and also serves to ensure the correct operation of the exhaust gas aftertreatment system.

The prior art shows various approaches to the detection of soot and particulates. A widely used approach in laboratories is the use of light control by the soot particles. This procedure is suitable for complex measuring devices. If it is attempted to use this as a mobile sensor system in the exhaust system, it must be noted that approaches for the realization of an optical sensor in a motor vehicle are associated with very high costs. Furthermore, there are unresolved problems regarding the pollution of the required optical windows by combustion exhaust gases.

From the US 8 713 991 B2 is a particle sensor for detecting the amount of particulates in an exhaust stream of an internal combustion engine known.

From the DE 10 2014 219 555 A1 and the DE 10 2014 222 844 A1 each soot sensors are known.

From the US 2008/0282769 A1 For example, an apparatus and method for shielding a soot sensor are known.

The present invention has for its object to provide a particle sensor in which contamination of the particle sensor can be reduced by entrained in the gas stream of the engine particles.

This object is achieved with a particle sensor according to independent claim 1. Advantageous embodiments are specified in the subclaims.

Essentially, the present invention is based on the idea of providing in a particle sensor an electrically non-conductive protective element which can at least partially prevent the gas stream flowing through the particle sensor from passing from a measuring region into a contact receiving region in which, for example, the electrical contacts of the particle sensor are arranged is. The protective element thus serves as a shield against the introduced into the gas flow with the gas sensor particles, in particular soot.

A particle sensor according to the invention for detecting a quantity of particles in a gas flow in an internal combustion engine has a housing in which a measuring region is arranged, which is arranged between a first housing region and the one is formed, at least partially protrude in an installed state of the particle sensor in the gas stream of the internal combustion engine, and a second housing portion extending substantially along a longitudinal axis. The particle sensor according to the invention further comprises an at least partially arranged in the measuring range and substantially cylindrical sensor electrode which is arranged coaxially to the longitudinal axis and extending beyond the second housing portion out of the measuring range, and an electrically non-conductive protective element, which is attached to the sensor electrode and thereto is formed, at least partially to prevent the gas flow at the second housing portion flows out of the measuring range. In particular, the particle sensor is a soot sensor for detecting the amount of soot in the exhaust gas of an internal combustion engine, wherein the protective element can at least partially prevent the soot contained in the gas flow passes into the contact receiving region of the sensor, are housed in the electrical contacts of the soot sensor in the housing.

In an advantageous embodiment of the particle sensor according to the invention, the protective element has a substantially disc-shaped section which extends radially outward in the direction of an inner wall of the housing with respect to the longitudinal axis. By means of this disk-shaped section of the protective element, a shielding of the measuring region is provided and can at least partially prevent particles from escaping from the measuring region into the contact-receiving region.

The particle sensor according to the invention further comprises, in a further advantageous embodiment, an electrically non-conductive insulator, which may be attached to the sensor electrode outside the measuring range, wherein the protective element is attached to the insulator.

According to a further preferred embodiment of the particle sensor according to the invention, a further electrical non-conductive protective element is provided, which is mounted on the second housing portion and extends at least partially radially inwardly with respect to the longitudinal axis, so that this further electrically non-conductive protective element together with attached to the sensor electrode electrically non-conductive protective element can form a substantially labyrinthine seal. Thus, a further enhancement of the shielding effect for particles from the measuring range can be produced.

Advantageously, the further protective element is integrally formed with the housing. For example, the further protective element may be formed on the housing.

In a further exemplary embodiment of the particle sensor, a substantially cylindrical main insulator is provided outside the measuring area, more precisely in the contact receiving area, which is attached to an inner wall of the housing and to the sensor electrode and is designed to insulate the measuring area from a contact receiving area of the gas sensor Contact receiving area, a cable can be contacted to the operating electronics of the particle sensor. The operating electronics can exercise the supply of the particle sensor and the processing of the sensor signals.

Preferably, the protective element and / or the further protective element are formed from a ceramic material. Alternatively, the protective element and / or the further protective element may be formed from a high temperature resistant plastic.

Further features and objects of the present invention will become apparent to those skilled in the art by exercising the present teachings and considering the accompanying drawings in which:

1 shows a sectional view along a longitudinal axis through an exemplary particle sensor,

2 shows a sectional view along a longitudinal axis through a particle sensor according to the invention, and

3 a sectional view along a longitudinal axis of a further particle sensor according to the invention shows.

The 1 shows a section through an exemplary particle sensor 100 , which is a substantially cylindrical housing 110 which extends substantially along a longitudinal axis 102 extends. In further embodiments, the housing 110 be formed conical or stepped. The housing 110 has a threaded portion 112 on, by means of which the particle sensor 100 For example, in an exhaust passage of an internal combustion engine (not shown) can be screwed. The housing 110 also has an area 114 on, for example in the form of an external hex, on which a corresponding tool can be attached, so that the particle sensor 100 can be screwed as desired in the exhaust passage of the internal combustion engine.

Inside the case 110 is a measuring range 120 provided, which extends between a first housing portion 116 which is adapted to, in a built-in state of the particle sensor 100 at least partially into a gas stream ( indicated with an arrow 10 in the 1 ), which flows through the exhaust passage of the internal combustion engine, at least partially protrude, and a second housing portion 118 essentially along the longitudinal axis 102 extends. In particular, describes the first housing area 116 a front end portion of the housing 110 and the second housing portion describes one of the first housing portion 116 spaced housing portion of the housing 110 , More specifically, the measuring range 120 through the first housing area 116 and the second housing portion 118 in a direction parallel to the longitudinal axis 102 defined or defined.

The housing 110 also has another, along the longitudinal axis 102 extending and the first housing portion 116 opposite housing area 119 in which a contact receiving area 122 is provided, in which at least partial electrical contacts (not shown) of the particle sensor can be accommodated, via which the particle sensor 100 can be connected to, for example, a control unit of a vehicle.

In measuring range 120 is also a substantially cylindrical sensor electrode 130 arranged coaxially with the longitudinal axis 102 is arranged. In further embodiments, the sensor electrode 130 be formed tapered stage. The sensor electrode 130 includes one within the measuring range 120 arranged measuring section 132 as well as along the longitudinal axis 102 through the second housing area 118 in the contact reception area 122 extending connecting section 134 , The measuring section 132 is for example a hollow cylindrical area.

The connecting section 134 is in particular adapted to a connection of the measuring section 132 to one in the contact reception area 122 arranged electrical contacts (not shown) via which the particle sensor 100 with z. B. the control unit of the vehicle can be connected.

Furthermore, the particle sensor 100 According to the embodiments shown in the drawings, a substantially cylindrical flow guide 140 in the measuring range 120 with respect to the longitudinal axis 102 in the radial direction outside the sensor electrode 130 and is arranged coaxially thereto. In further embodiments, the flow guide 140 have a conical or stepped shape. In particular, the flow guide is 140 around the measuring section 132 the sensor electrode 130 arranged such that a first flow path 100 between a radial inner wall 111 of the housing 110 and a radial outer wall 141 the flow guide is formed such that the gas flow through the first flow path 104 from the first housing area 116 in the direction of the second housing area 118 flows, and a second flow path 106 between the sensor electrode 130 and the flow guide 140 is formed such that the gas flow through the second flow path 106 from the second housing area 118 in the direction of the first housing area 116 flows. In the 1 is the flow direction of the gas flow through the first flow path 104 with an arrow 12 indicated and the flow direction through the second flow path 106 with an arrow 14 indicated.

In particular, the first flow path 104 and the second flow path 106 each substantially provided as cylindrical portions, with respect to the longitudinal axis 102 are provided coaxially with each other and from the flow guide 140 limited or separated from each other. Generally, however, the shape of the first flow path becomes 104 by the shape of the case 110 and by the shape of the flow guide 140 defined and the shape of the second flow path 106 by the shape of the flow guide 140 and by the shape of the sensor electrode 130 Are defined. Thus the gas flow 10 through the measuring range 120 can flow, the housing has 110 in the first housing area 116 at least one inlet opening 101 in the jacket of the case 110 is provided, and one along the longitudinal axis 102 extending outlet opening 103 on.

According to the 1 has the particle sensor 100 further on the second housing portion 118 attached deflecting element 150 which is adapted to the gas flow through the first flow path 104 in the second flow path 106 redirect. The deflecting element 150 is preferably with the housing 110 formed integrally and is in the shape of a from the radial inner wall 111 of the housing 110 with respect to the longitudinal axis 102 formed at least partially radially inwardly extending projection. The deflecting element 150 has a groove 152 on that in a side surface of the deflecting element 150 is formed. The groove 152 preferably has a concave bottom, so that the gas flow through the first flow path 104 optimized in the second flow path 106 can be redirected. The groove 152 is one around the longitudinal axis 102 circumferential groove and has a round bottom.

Of the 1 it can be seen that the deflection 150 deflects the gas flow by about 180 °, what with an arrow 18 is indicated schematically. In particular, the deflecting element 150 designed to prevent it, the gas stream including its entrained particles in the contact receiving area 122 reaches outside the measuring range 120 located. In particular, will the contact receiving area 122 through the second housing area 118 from the measuring range 120 separated. Thus, the risk of excessive contamination by particles, especially soot, by the gas flow in the particle sensor 100 can be reduced, and the gas sensor can work reliably over a longer life.

More precisely, the deflecting element 150 Prevent a flow direction vector from flowing through the first flow path 104 flowing gas stream directly into the contact receiving area 122 shows. Preferably, one is about the longitudinal axis 102 running gap 154 between the deflecting element 150 and the measuring section 132 the sensor electrode 130 designed as small as possible, thus the penetration of particles into the electrode area 122 can be reduced.

With reference to the 2 is a particle sensor according to the invention 100 already shown in the 1 Known elements are provided with the same reference numerals.

The particle sensor 100 from the 2 is different from the particle sensor 100 of the 1 in that no deflecting element 150 is provided and a connection between the first flow path 104 and the second flow path 106 by means of a flow guide 140 formed an opening 142 will be produced. It is envisaged that the majority of the gas flow through 180 ° according to the arrow 18 is diverted. However, some of the gas flow could be along the arrow 19 (dotted arrow in the 2 ) and would thus flow into the contact receiving area 122 reach.

To prevent this, the particle sensor points 100 of the 2 an electrically non-conductive protective element 160 on, at the sensor electrode 130 more precisely at the connecting section 134 the sensor electrode 130 , is mounted and adapted to at least partially prevent the gas flow at the second housing portion 118 out of the measuring range 120 flows out and into the contact receiving area 122 arrives. Again 2 can be seen, has the electrically non-conductive protective element 160 preferably a disk-shaped section 162 on, referring to the longitudinal axis 102 extends in the radial direction outwards and thus a shield for the along the arrow 19 forms flowing gas stream and thus prevents the particles contained in the gas stream thereof, in the contact receiving area 122 to stream and pollute it.

The particle sensor 100 of the 2 also has another electrically non-conductive protective element 170 on, the second housing area 118 is attached and one with respect to the longitudinal axis 102 at least partially such radially inwardly extending disc-shaped portion 172 on, in combination with the disc-shaped section 162 of the protective element 160 forms a substantially labyrinthine seal. The interaction of the two protective element 160 . 170 Strengthens a shield against particles and makes it difficult for the particles, from the measuring range 120 in the contact reception area 122 to get.

The disc-shaped section 162 or the disc-shaped section 172 are each adapted to extend in the radial direction such that between the section 162 and the protective element 170 or the housing 110 the smallest possible gap is provided or that between the section 172 and the connection section 134 the sensor electrode 130 or the protective element 160 the smallest possible gap is provided. In particular, the two gaps are designed to at least partially prevent it from being attached to the protective elements 160 . 170 depositing and electrically conductive soot an electrical connection between the sensor electrode 130 and the housing 110 which causes a short circuit and the measuring signal of the particle sensor 100 could falsify.

Preferably, the protective element 160 and / or the further protective element 170 formed from a ceramic material. Alternatively, the protective elements 160 . 170 be formed of a high temperature resistant plastic.

The 3 shows a further particle sensor according to the invention 100 that is both the one from 1 known deflection 150 as well as from the 2 known protective elements 160 . 170 having. Due to the interaction of the deflecting element 150 and the protective element 160 The risk can be further reduced that particles from the gas stream at the transition from the first flow path 104 in the second flow path 106 out of the measuring range 120 in the contact reception area 122 can reach and thus cause pollution of the electrical contacts.

To further enhance the shielding, the particle sensor 100 of the 3 also in the contact receiving area 122 arranged main insulator 180 on, at the sensor electrode 130 and on the housing area 119 of the housing 110 is appropriate. The main insulator 180 is designed to isolate the measuring voltage from its counterpart potential.

With the deflection element 150 and / or the protective elements 160 . 170 can be at least partially prevented that particles, in particular electrically conductive soot particles from an exhaust gas of an internal combustion engine of a vehicle, in the contact receiving area 122 between the main insulator 180 and the measuring range 120 enter and join the main isolator 180 deposit. At the main insulator 180 depositing soot particles could be an electrical connection between the housing 110 and the energized sensor electrode 130 and thus cause an unwanted short circuit.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 8713991 B2 [0007]
• DE 102014219555 A1 [0008]
• DE 102014222844 A1 [0008]
• US 2008/0282769 A1 [0009]

Claims (10)

Particle sensor ( 100 ) for detecting a particle amount in a gas flow in an internal combustion engine, wherein the particle sensor ( 100 ): - a housing ( 110 ), in which a measuring range ( 120 ) arranged between a first housing region ( 116 ) which is adapted to be in a built-in state of the particle sensor ( 100 ) protrude at least partially into the gas flow of the internal combustion engine, and a second housing region ( 118 ) substantially along a longitudinal axis ( 102 ), one at least partially in the measuring range ( 120 ) and substantially cylindrical sensor electrode ( 130 ) coaxial with the longitudinal axis ( 102 ) is arranged and over the second housing portion ( 118 ) out of the measuring range ( 120 ), and - an electrically non-conductive protective element ( 160 ) connected to the sensor electrode ( 130 ) and is adapted to at least partially prevent the gas flow at the second housing region ( 118 ) out of the measuring range ( 120 ) flows out. Particle sensor ( 100 ) according to claim 1, wherein the protective element ( 160 ) has a substantially disc-shaped section ( 162 ), which with respect to the longitudinal axis ( 102 ) radially outward in the direction of an inner wall ( 111 ) of the housing ( 110 ). Particle sensor ( 100 ) according to one of the preceding claims, further comprising an electrically non-conductive insulator attached to the sensor electrode ( 130 ) outside the measuring range ( 120 ), the protective element ( 160 ) is attached to the insulator. Particle sensor ( 100 ) according to one of the preceding claims, further comprising a further electrically non-conductive protective element ( 170 ) on the housing ( 110 ) and a with respect to the longitudinal axis () at least partially radially inwardly extending disc-shaped portion ( 172 ), which is connected to the at the sensor electrode ( 130 ) mounted electrically non-conductive protective element ( 160 ) forms a substantially labyrinthine seal. Particle sensor ( 100 ) according to claim 4, wherein the further protective element ( 170 ) Is formed integrally with the housing. Particle sensor ( 100 ) according to one of the preceding claims, furthermore with an outside of the measuring range ( 120 ) and substantially cylindrical main insulator ( 180 ) connected to the sensor electrode ( 130 ) and an inner wall ( 111 ) of the housing ( 110 ) and is adapted to the measuring range ( 120 ) from outside the measuring range ( 120 ) arranged contact receiving area ( 122 ) to isolate. Particle sensor ( 100 ) according to one of the preceding claims, wherein the protective element ( 160 ) and / or the further protective element ( 170 ) are formed of a ceramic material or a high temperature resistant plastic. Particle sensor ( 100 ) according to one of the preceding claims, wherein the flow guide element ( 140 ) on the first housing area ( 116 ) and / or on the second housing area ( 118 ) is attached. Particle sensor ( 100 ) according to one of the preceding claims, further comprising at least one in the first housing region ( 116 ) in the jacket of the housing ( 110 ) formed inlet opening ( 101 ), through which the gas flow into the first flow path ( 104 ) can flow. Particle sensor ( 100 ) according to any one of the preceding claims, further comprising a through the first housing portion ( 116 ) along the longitudinal axis ( 102 ) extending outlet opening ( 103 ), through which the gas flow from the measuring range ( 120 ) can flow out.

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