PARTICULATE MATTER DETECTION SENSOR

Abstract

A particulate matter detection sensor has an accumulation section for accumulating a part of particulate matter particles contained in exhaust gas emitted from an internal combustion engine, and a pair of a first detection electrode and a second detection electrode formed on the accumulation section. The second detection electrode is formed separated from the first detection electrode. The first detection electrode has projecting parts which project toward the second detection electrode. Because a separation between the first and second detection electrodes is locally reduced at the projecting parts, the projecting parts attract and accumulate more particulate matter, and this structure makes it possible to allow the particulate matter detection sensor to have improved detection sensitivity.

Claims

1. A particulate matter detection sensor comprising: an accumulation section which accumulates particulate matter particles contained in exhaust gas emitted from an internal combustion engine; a detection electrode comprising a pair of a first detection electrode and a second detection electrode formed on the accumulation section, the second detection electrode being formed separated from the first detection electrode on the accumulation section, wherein projecting parts are formed on at least one of the first detection electrode and the second detection electrode, and the projecting parts formed on at least one of the first detection electrode and the second detection electrode project toward the other detection electrode, and a separation between the first detection electrode and the second detection electrode is locally reduced at the projecting parts. equipotential lines of electric field at the projecting parts have a high density when compared with equipotential lines of the electric field at an area excepting the projecting parts between the first detection electrode and the second detection electrode.

2. The particulate matter detection sensor according to claim 1, wherein the projecting parts are formed on both the first detection electrode and the second detection electrode, and the projecting parts are arranged so that the projecting parts formed on the first detection electrode and the projecting parts formed on the second detection electrode face each other.

3. The particulate matter detection sensor according to claim 1, wherein at least one of the first detection electrode and the second detection electrode has a plurality of the projecting parts.

4. The particulate matter detection sensor according to claim 1, wherein a minimum separation between the first detection electrode and the second detection electrode is within a range of not less than 1 μm and not more than 50 μm.

5. The particulate matter detection sensor according to claim 1, wherein the first and second detection electrodes and second detection electrodes and the insulation members are alternately stacked in the particulate matter detection sensor, the insulation members have electric insulation properties, and insulation projecting parts are formed on a surface of one of a pair of the insulation members, by which the detection electrode is sandwiched, so that the insulation projecting parts project toward the other of the pair of the insulation members, and insulation depressed parts are formed on the other of the pair of the insulation members at locations corresponding to the insulation projecting parts formed on one of the pair of the insulation members.

6. A method of producing the particulate matter detection sensor according to claim 5 in which the first detection electrodes and second detection electrodes and the insulation members are stacked and joined together, comprising the steps of: stacking each of the first and second detection electrodes between a pair of the insulation members comprising the insulation projecting parts and the insulation depressed parts so that the insulation projecting parts and the insulation depressed parts face each other; and pressing the pair of the pair of the insulation members and the first and second detection electrodes together in a stacking direction of the insulation members so as to deform each of the first and second detection electrodes sandwiched between the pair of the insulation members along the insulation projecting parts and the insulation depressed parts, and to form the projecting parts.

7. The particulate matter detection sensor according to claim 1, wherein the projecting parts have one of a triangle-like shape and a trapezoid-like shape.

8. The particulate matter detection sensor according to claim 2, wherein the projecting parts have one of a triangle-like shape and a trapezoid-like shape.

9. The particulate matter detection sensor according to claim 3, wherein the projecting parts have one of a triangle-like shape and a trapezoid-like shape.

10. The particulate matter detection sensor according to claim 4, wherein the projecting parts have one of a triangle-like shape and a trapezoid-like shape.

11. The particulate matter detection sensor according to claim 5, wherein the projecting parts have one of a triangle-like shape and a trapezoid-like shape.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0010] [FIG. 1] is a view explaining a particulate matter detection sensor according to a first exemplary embodiment.

[0011] [FIG. 2] is a view explaining a structure of the particulate matter detection sensor according to the first exemplary embodiment.

[0012] [FIG. 3] (a) is a view explaining equipotential lines formed in the particulate matter detection sensor according to the first exemplary embodiment, and (b) is a view explaining particulate matter which has been adhered and has accumulated in the particulate matter detection sensor according to the first exemplary embodiment.

[0013] [FIG. 4] is a view explaining a particulate matter detection sensor according to a second exemplary embodiment.

[0014] [FIG. 5] is a view explaining a particulate matter detection sensor according to a third exemplary embodiment

[0015] [FIG. 6] is a view explaining a particulate matter detection sensor according to a fourth exemplary embodiment.

DESCRIPTION OF EMBODIMENTS

[0016] In the particulate matter detection sensor according to the present invention, the projecting parts are formed between the first detection electrode and the second detection electrode. It is preferable to arrange the first detection electrode and the second detection electrode to face each other. This structure makes it possible to form a strong electric field by the projecting parts in which the first detection electrode and the second detection electrode face each other. Accordingly, it is possible for the projecting parts to attract a large amount of particulate matter, and this structure makes it possible to improve the detection sensitivity of the particulate matter detection sensor.

[0017] Further, it is preferable for at least one of the first detection electrode and the second detection electrode to have the projecting parts. This structure allows each of the projecting parts to attract and stably collect particulate matter. Accordingly, it is possible for the particulate matter detection sensor having the structure to provide an improved detection sensitivity.

[0018] Still further, in the particulate matter detection sensor having the structure previously described, detection electrode layers and insulation layers are alternately stacked. The insulation layers have electrical insulation properties. It is preferable to form insulation projecting parts in one of the insulation layers with which the detection layer having the projecting parts is sandwiched, and to form insulation depressed parts in the other insulation layers with which the detection layer having the projecting parts is sandwiched, wherein the insulation projecting parts and the insulation depressed parts are faced from each other. This structure makes it possible to provide the effect to allow the detection electrodes having the projecting parts to be easily formed.

[0019] Still further, in a production process in which the detection electrode layers and the insulation layers are alternately stacked and bonded together to produce the particulate matter detection sensor, it is preferable for the detection electrode to have the projecting parts formed in a curved shape along the insulation projecting parts and the insulation depressed parts, by pressing in a stack direction of the insulation layers and the detection layers, wherein each detection layer is sandwiched by the corresponding insulation layers, and the insulation projecting parts and the insulation depressed parts face each other. This structure makes it possible to easily form the projecting parts in the detection electrode along the pair of the insulation layers, and to easily produce the particulate matter detection sensor with superior detection sensitivity for detecting the presence of particulate matter.

Exemplary Embodiments

First Exemplary Embodiment

[0020] A description will be given of the particulate matter detection sensor 1 according to the first exemplary embodiment with reference to FIG. 1 to FIG. 3. As shown in FIG. 1, the particulate matter detection sensor 1 according to the first exemplary embodiment has an accumulation section 10 and first detection electrodes 11 and second detection electrodes 12, in which the first detection electrode 11 and the second detection electrode 12 form a pair. That is, multiple pairs of the first detection electrode 11 and the second detection electrode 12 are formed on the accumulation section 10. The accumulation section 10 collects a part of particulate matter (P) particles contained in exhaust gas emitted from an internal combustion engine. The collected particulate matter P accumulates on the accumulation section 10. The second detection electrode 12 is arranged separated from the first detection electrode 11 The projecting parts 111, which project toward the second detection electrode 12, are formed in the first detection electrode 11. A separation or gap between the first detection electrode 11 and the second detection electrode 12 is locally reduced at each of the projecting parts 111.

[0021] Hereinafter, a description will now be given of the particulate matter detection sensor 1 according to the first exemplary embodiment in detail. The particulate matter detection sensor 1 according to the first exemplary embodiment detects particulate matter P contained in exhaust gas emitted from an internal combustion engine and passing through an exhaust gas, which are mounted on a vehicle. A failure detection process of the exhaust gas purification device is performed on the basis of information obtained from the particulate matter detection sensor 1. The particulate matter detection sensor 1 is arranged in the inside of the exhaust gas pipe so that the particulate matter detection sensor 1 projects into the inside of the exhaust gas pipe. A front end side of the particulate matter detection sensor 1 is arranged inside of the exhaust gas pipe along an axial direction of the particulate matter detection sensor 1. A distal end side of the particulate matter detection sensor 1 is opposite to the front end side of the particulate matter detection sensor 1.

[0022] As shown in FIG. 1 and FIG. 2, the particulate matter detection sensor 1 has the accumulation section 10, the multiple first detection electrodes 11 and the multiple second detection electrodes 12. Particulate matter P contained in exhaust gas accumulate on the accumulation section 10, and the first detection electrode 11 is separated from the second detection electrode 12. The particulate matter detection sensor 1 has the structure in which the nine insulation members 21 and 22 made of insulation material and the eight detection electrodes 11, 12 are alternately stacked to form a stick-like shape sensor. The accumulation section 10 is formed on a front end surface of the particulate matter detection sensor 1, on which the first detection electrodes 11 and the second detection electrodes 12 are exposed.

[0023] The eight detection electrodes 11 and 12 composed of the first detection electrodes and the second detection electrodes are alternately arranged and made of copper. The first detection electrodes 11 are used as a positive electrode, and the second detection electrodes 12 are used as a negative electrode. The first detection electrode 11s and the second detection electrodes 12 are arranged adjacently from each other. Each of the first detection electrodes 11 has the projecting parts 111 which project toward the corresponding second detection electrode 12, respectively. In the first exemplary embodiment, when viewed from the front end side of the particulate matter detection sensor 1, the projection part 111 in the first detection electrode 11 has a mountain shape structure, a mountain-like shape structure, a triangle shape structure, or a triangle-like shape structure.

[0024] The second detection electrode 12 has a flat-like shape structure. Lead sections 112 and 121 are connected to the first detection electrode 11 and the second detection electrode 12, respectively and formed extending to the distal end side of the particulate matter detection sensor 1. The minimum separation between the projecting part 111 in the first detection electrode 11 and the b second detection electrode 12 is 10 μm.

[0025] The insulation members 21 and 22 are made of ceramic material such as alumina, zirconia, magnesia, beryllia, etc. and formed in a plate shape. In the first exemplary embodiment, a pair of the insulation members 21, 22 have a shape which corresponds to the shape of the first detection electrode 11. A plurality of the insulation projecting parts 211 are formed on a surface of the insulation member 21 in a pair of the insulation members 21 and 22, with which the first detection electrode 11 is sandwiched. The surface of the insulation member 21 faces the surface of the first detection electrode 11 on which the insulation projecting parts 211 are formed. The insulation projecting parts 211 project toward the insulation member 22. In addition, a plurality of the insulation depressed parts 221 are formed in the surface of the insulation member 22, which faces the first detection electrode 11 so that the insulation depressed parts 221 correspond to the insulation projecting parts 211 formed in the insulation member 21.

[0026] The first detection electrode 11 having a thin plate shape is arranged between the insulation members 21 and 22. The first detection electrode 11, the insulation members 21 and 22 are pressed in the stack direction of the insulation members 21, 22. This process makes it possible to deform the first detection electrode 11 to be fitted with the shape of the insulation projecting parts 211 and the insulation depressed parts 221. That is, the first detection electrode 11 is curved along the shape of the insulation projecting parts 211 and the insulation depressed parts 221, and the projecting part 111 are formed in the first detection electrode 11.

[0027] As shown in FIG. 3(b), when the particulate matter P is accumulated on the accumulation section 10, the particulate matter P accumulated on the accumulation section 10 allows the electrical conduction to occur between the first detection electrode 11 and the second detection electrode 12, and as a result, reduces an electrical resistance between the first detection electrode 11 and the second detection electrode 12. An amount of a current, which represents an electrical signal, flowing between the first detection electrode 11 and the second detection electrode 12 varies due to the variation of the electrical resistance between the first detection electrode 11 and the second detection electrode 12. The particulate matter detection sensor 1 outputs a current value which varies the variation of the current flowing between the first detection electrode 11 and the second detection electrode 12. That is, the current value as the output of the particulate matter detection sensor 1 varies on the basis of the accumulation amount of particulate matter P accumulated on the accumulation section 10, and provides information regarding the amount of particulate matter P accumulated on the accumulation section 10. It is accordingly possible to detect the amount of particulate matter P accumulated on the accumulation section 10 on the basis of the current value as the output of the particulate matter detection sensor 1. In the particulate matter detection sensor 1 according to the first exemplary embodiment, a particulate matter amount detection section detects a current, and outputs the detected current value to a control unit having a shunt resistance. The control unit outputs a voltage value which is obtained by multiplying the current value and the shunt resistance together. This voltage value is the output of the particulate matter detection sensor 1.

[0028] Next, a description will now be given of the explanation of the behavior and effects of the particulate matter detection sensor 1 according to the first exemplary embodiment.

[0029] In the particulate matter detection sensor 1 according to the first exemplary embodiment, the projecting parts 111 are formed on the first detection electrode 11 in a pair of the first detection electrode 11 and the second detection electrode 12. The formation of the projecting parts 111 makes it possible to improve the detection sensitivity of the particulate matter detection sensor 1. That is, as shown in FIG. 3(a), the formation of the projecting parts 111 allows the separation between the first detection electrode 11 and the second detection electrode 12 to be drastically reduced at the projecting parts 111. This makes it possible to provide equipotential lines L having a high density between the first detection electrode 11 and the second detection electrode 12, and generates a strong electric field at the projecting parts 111 when compared with the parts other than the projecting parts 111.

[0030] As shown in FIG. 3(b), particulate matter P is strongly attracted to and adhered on the projecting parts 111. When particulate matter P adhered on the projecting parts 111 has conductivity, because the projecting parts 111 and the particulate matter P accumulated and adhered on the projecting parts 111 have the same electrical potential, the particulate matter P adhered on the projecting parts 111 function as the projecting parts 111, and as a result, the projecting parts 111 further attract particulate matter P contained in exhaust gas. This makes it possible for the projecting parts 111 to provide selective attraction of particulate matter P, and speedily execute the electrical conduction between the first detection electrode 11 and the second detection electrode 12. This makes it possible to improve the detection sensitivity of the particulate matter detection sensor 1.

[0031] Further, because the first detection electrode 11 has a plurality of the projecting parts 111, the projecting parts 111 attract and accumulate particulate matter P. This makes it possible to provide the stable collection of particulate matter P and to more improve the detection sensitivity of the particulate matter detection sensor 1.

[0032] Still further, the minimum separation between the first detection electrode 11 and the second detection electrode 12 is within a range of not less than 1 μm and not more than 50 μm. This structure makes it possible to provide the improved detection sensitivity of the particulate matter detection sensor 1 while maintaining the productivity of the particulate matter detection sensor 1. In particular, it is preferable for the separation between the first detection electrode 11 and the second detection electrode 12 to have the minimum value, as small as possible, of not less than 1 μm. The more the minimum separation between the first detection electrode 11 and the second detection electrode 12 reduces, the more the conductivity between the first detection electrode 11 and the second detection electrode 12 rapidly occurs. This makes it possible to improve the detection sensitivity of the particulate matter detection sensor 1.

[0033] Still further, the particulate matter detection sensor 1 is produced to have a structure in which the multiple first detection electrodes 11, the multiple second detection electrodes 12 and the multiple insulation members 21, 22 are alternately stacked, and each first detection electrode 11 is sandwiched by the first insulation member 21 and the second insulation member 22. The insulation projecting parts 211 are formed on he insulation member 21 to project toward the second insulation member 22. The insulation depressed parts 221 are formed o the second insulation member 22 to face the insulation projecting parts 211. This structure makes it possible to easily form the projecting parts 111 in the first detection electrode 11.

[0034] Further, the multiple detection electrodes 11, 12 and the insulation members 21, 22 are alternately stacked and joined together.

[0035] In the production of the particulate matter detection sensor 1, the first detection electrode 11 is sandwiched between the first and second insulation members 21, 22 so that the insulation projecting parts 211 are arranged to face the insulation depressed parts 221. The insulation members 21, 22 and the first detection electrode 11 are pressed in the stack direction of the insulation members 21, 22 to deform the first detection electrode 11 along the insulation projecting parts 211 and the insulation depressed parts 221 so as to form the projecting parts 111 in the first detection electrode 11. This process makes it possible to easily form the projecting parts 111 in the first detection electrode 11 by using the insulation members 21, 22. This process makes it possible to provide the particulate matter detection sensor 1 with superior detection sensitivity for detecting particulate matter P.

[0036] As previously described, the first exemplary embodiment provides the particulate matter detection sensor 1 capable of detecting particulate matter P with improved detection sensitivity.

Second Exemplary Embodiment

[0037] A description will be given of the particulate matter detection sensor 1 according to the second exemplary embodiment with reference to FIG. 4.

[0038] As shown in FIG. 4, the particulate matter detection sensor 1 according to the second exemplary embodiment has a structure which is different in part from the structure of the particulate matter detection sensor 1 according to the first exemplary embodiment.

[0039] In the structure of the particulate matter detection sensor 1 according to the second exemplary embodiment, the projecting parts 111 and projecting parts 121 are formed on the first detection electrode 11 and the second detection electrode 12, respectively. The first detection electrode 11 has substantially the same structure of the first detection electrode 11 formed in the particulate matter detection sensor 1 according to the second exemplary embodiment. On the other hand, the second detection electrode 12 is formed in the accumulation section 10 so that the second detection electrode 12 and the first detection electrode 11 are arranged in linear symmetry when viewed from the straight line which is perpendicular to the stack direction of the insulation members 21, 22 in the particulate matter detection sensor 1. Accordingly, the projecting parts 111 in the first detection electrode 11 face the projecting parts 121 in the second detection electrode 12, respectively.

[0040] Further, the insulation projecting parts 211 and insulation depressed parts 221 are formed on the surfaces of the insulation members 21, 22, respectively, between which the second detection electrode 12 is sandwiched. Those surfaces of the insulation members 21, 22 face the second detection electrode 12. Other components of the particulate matter detection sensor 1 according to the second exemplary embodiment are the same as the particulate matter detection sensor 1 according to the first exemplary embodiment previously described. The same components will be referred with the same reference numbers and characters.

[0041] In the structure of the particulate matter detection sensor 1 according to the second exemplary embodiment, the projecting parts 111 and the projecting parts 121 are formed on the first detection electrode 11 and the second detection electrode 12, respectively, so that the projecting parts 111 in the first detection electrode 11 face the projecting parts 121 in the second detection electrode 12. Accordingly, the parts at which the projecting parts 111 face the projecting parts 121, respectively, have a strong electric field intensity, and the parts attract and accumulate particulate matter P contained in exhaust gas. This makes it possible to provide the particulate matter detection sensor 1 having the improved detection sensitivity to detect particulate matter P. The particulate matter detection sensor 1 according to the second exemplary embodiment has the same effects of the particulate matter detection sensor 1 according to the first exemplary embodiment.

Third Exemplary Embodiment

[0042] A description will be given of the particulate matter detection sensor 1 according to the third exemplary embodiment with reference to FIG. 5.

[0043] As shown in FIG. 5, the particulate matter detection sensor 1 according to the third exemplary embodiment has projecting parts capable of attracting particulate matter P, each of which has a structure which is different from the structure of the projecting parts 111 and the projecting parts 121 in the particulate matter detection sensor 1 according to the second exemplary embodiment previously described.

[0044] In the structure of the particulate matter detection sensor 1 according to the third exemplary embodiment shown in FIG. 5, multiple projecting parts 111-1 and multiple projecting parts 121-1 are formed on the first detection electrode 11 and the second detection electrode 12, respectively, each of which has a trapezoid shape or a trapezoid-like shape. Other components of the particulate matter detection sensor 1 according to the third exemplary embodiment are the same as the particulate matter detection sensor 1 according to the second exemplary embodiment previously described. The same components will be referred with the same reference numbers and characters.

Fourth Exemplary Embodiment

[0045] A description will be given of the particulate matter detection sensor 100 according to the fourth exemplary embodiment with reference to FIG. 6.

[0046] As shown in FIG. 6, the particulate matter detection sensor 100 according to the fourth exemplary embodiment has a structure which is different from the structure of the particulate matter detection sensor 1 according to each of the first to third exemplary embodiments previously described.

[0047] The particulate matter detection sensor 100 according to the fourth exemplary embodiment has the accumulation section 10 for accumulating particulate matter P contained in exhaust gas, and a pair of first and second detection electrodes 13, 14. The first and second detection electrodes 13, 14 are arranged in the accumulation section 10 to separate from each other by a predetermined separation. The accumulation section 10 has a rectangle-like plate shape and is made of insulation material. The first and second detection electrodes 13, 14 are made of conductive material. The first and second detection electrodes 13, 14 have a plate thin film which is printed on a surface of the accumulation section 10 by a pattern printing process, etc. In a pair of the first and second detection electrodes 13, 14, the first detection electrodes 13 has comb teeth parts 132, and the second detection electrodes 14 has comb teeth parts 142.

[0048] The electrode base parts 131, 141 are formed on the accumulation section 10 along and in parallel to a longitudinal direction of the accumulation section 10. The comb teeth parts 132, 142 are formed extending from the electrode base parts 131, 141, in the first detection electrodes 13 and the second detection electrode 14 respectively. The first and second detection electrodes 13, 14 are arranged facing each other on the surface of the accumulation section 10, and the comb teeth parts 132, 142 are arranged alternately on the surface of the accumulation section 10 so that the comb teeth parts 132, 142 in the second detection electrode 14 are arranged between the comb teeth parts 132, 142 of the first detection electrodes 13.

[0049] Each of the comb teeth parts 132 has projecting parts 133, and each of the comb teeth parts 142 has projecting parts 143.

[0050] The projecting part 133, 143 has a mountain shape structure, a mountain-like shape structure, a triangle shape structure, or a triangle-like shape structure. The continuous formation of the projecting parts 133 and the projecting parts 143 provides the comb teeth parts 132 having a wave-like shape, and the comb teeth parts 142 having a wave-like shape. In the structure of the particulate matter detection sensor 100 according to the fourth exemplary embodiment, the minimum separation between the first detection electrode 13 and the second detection electrode 14 is 50 μm.

[0051] The fourth exemplary embodiment provides the particulate matter detection sensor 100 having a simpler structure.

[0052] In the particulate matter detection sensor 100 according to the fourth exemplary embodiment having the structure in which the first and second detection electrodes 13 and 14 having a plane film shape are formed on the surface of the accumulation section 10 by a by a pattern printing process, it is preferable that the minimum separation between the first detection electrode 13 and the second detection electrode 14 has a value of not less than 50 μm and is as small as possible. This structure makes it possible to provide the particulate matter detection sensor 100 with increased detection sensitivity because of having a reduced separation between the first and second detection electrodes 13, 14 while maintaining the production of those first and second detection electrodes 13, 14. Further, the particulate matter detection sensor 100 according to the fourth exemplary embodiment has the same behavior and effects as the particulate matter detection sensor 1 according to the first exemplary embodiment.

REFERENCE SIGNS LIST

[0053] 1, 100 Particulate matter detection sensor, 10 Accumulation section, 11, 12, 13, 14 Detection electrode, 11, 13 First detection electrode, 12, 14 Second detection electrode, and 111, 121, 111-1, 121-1, 133, 143 Projection parts.