JP3991447B2 - Induction heat purification device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust gas purification device attached to an internal combustion engine for automobiles, and more particularly to a heating device for quickly and efficiently raising the temperature of the purification device for exhaust gas purification.
[0002]
[Prior art]
In a catalyst device which is one of exhaust purification devices, the temperature must be raised to a certain temperature or higher in order for the catalyst to exhibit a catalytic action. Therefore, in the case of a catalyst in an exhaust purification device such as an automobile, a sufficient catalytic function is difficult to be exhibited when the engine is started. Therefore, conventionally, various proposals have been made for means for heating directly or indirectly by an electric heater or the like in order to shorten the catalyst warm-up time.
[0003]
As one of the proposals, a method of heating a catalyst by induction heating is proposed as disclosed in JP-A-08-28250. This includes an induction heating type monolith catalyst in which a coil for induction heating of the monolith catalyst carrier is provided on the outer periphery of the monolith catalyst carrier on which the catalyst is supported via an electric insulating material. This monolithic catalyst carrier generates an induced current in the carrier when the carrier is formed of an electric resistor. For this reason, it is not necessary to form an electrode portion on the catalyst carrier itself as in the case of a so-called direct heating method in which current is directly passed from the outside to the conventional carrier itself, and the contact resistance due to oxidation of the electrode portion and thermal shock is reduced. Problems such as changes are resolved. In addition, the adjustment of the heat generation amount has an advantage that it can be controlled using an optimum method from a number of methods such as adjustment of oscillation frequency, pulse width, and pulse duty cycle.
[0004]
As another exhaust purification device, there is a particulate filter that collects particulates discharged from a diesel engine and burns the collected particulates. As for the means for burning the particulates, a method similar to the above-described prior art, that is, a method for heating and removing the particulates collected by the particulate filter by heating the metal filter by induction heating has been proposed. (Japanese Patent Laid-Open No. 08-326522)
[0005]
[Problems to be solved by the invention]
However, in the conventional induction heating type purification apparatus, since the entire purification apparatus is heated, the part that does not need to be heated is also heated, so that the heating energy is wasted and the temperature is raised to a desired temperature. Needed a lot of time. Specifically, in the catalyst device, only the catalyst metal that causes the purification action in the catalyst device and its peripheral part should be heated, but the entire catalyst including the carrier is heated, and in the particulate filter, the inside of the particulate filter The entire filter should have been heated, although only the particulate adhering portion should be heated. Furthermore, regarding the waste of heating energy, since exhaust gas is discharged outside the vehicle through the purification device, there is a problem that when the entire purification device is heated, the ratio of heat energy taken away from the vehicle by the exhaust gas increases. .
[0006]
An object of the present invention is to provide an induction heating type purification apparatus for an internal combustion engine that can be locally heated to greatly reduce heating energy by interspersing particulate magnetic bodies at desired sites to be heated. And
[0007]
[Means for Solving the Problems]
According to the first aspect of the present invention, the exhaust pipe of the internal combustion engine is provided with a catalyst for purifying the exhaust gas, and the catalyst includes a catalyst carrier and catalyst metal particles dispersed and supported on the surface of the carrier. The induction heating coil for flowing an induction current, and the catalyst is made of a magnetic material that generates heat by the induction current. When the temperature of the catalyst is to be raised, the induction heating coil is operated to In the induction heating purification device for an internal combustion engine provided with a coil energization control means for heating the body, the catalyst carrier is made of a non-magnetic material, and the magnetic material is scattered in the vicinity of catalyst metal particles on the surface of the catalyst carrier. An induction heating type purification device for an internal combustion engine is provided.
[0008]
That is, in the first aspect of the invention, the induction heating coil is energized to form an alternating magnetic field in the entire purification device. In the magnetic material scattered in the form of particles on the surface of the catalyst carrier existing in the alternating magnetic field, a voltage is induced by an electromagnetic induction action and an induced current flows. Then, Joule heat is generated by this induced current. In particular, since a large amount of induced current flows on the surface of the magnetic material, the heating temperature is higher on the particle surface of the magnetic material. When the surface of the magnetic material becomes high temperature, the space and the carrier in the vicinity of the magnetic material are heated, and since the magnetic material and the catalytic metal are close to each other, heat is conducted or transferred to the low-temperature catalytic metal particles, and the catalytic metal becomes the active temperature. Decompose HC, CO, etc. in exhaust gas. Accordingly, in the first aspect of the present invention, only the magnetic material scattered in the vicinity of the catalyst metal particles on the surface of the catalyst carrier generates heat, so that the amount of current supplied to the induction heating coil can be reduced and the waste of heating energy can be eliminated. it can.
[0009]
According to the invention described in claim 2, the filter is provided for collecting particulates in exhaust gas in an exhaust pipe of an internal combustion engine, the filter is made of non-magnetic material, the induced current in the filter An induction heating coil for flowing is attached , and a magnetic body that generates heat due to an induction current is scattered in the form of particles on the surface of the filter. When the particulate of the filter is to be burned, the induction heating coil is operated. Thus, there is provided an induction heating type purification device for an internal combustion engine provided with coil energization control means for heating the magnetic body.
[0010]
That is, in the invention of claim 2, the induction heating coil is energized to form an alternating magnetic field in the entire purification device. Filter table surface magnetic material interspersed into particles onto existing in the alternating magnetic field induced current flows are induced voltage by electromagnetic induction. Then, Joule heat is generated by this induced current. In particular, since a large amount of induced current flows on the surface of the magnetic material, the heating temperature is higher on the particle surface of the magnetic material. Due to this heat, the fine particles attached around the magnetic fine particles start to be heated and burned. It is possible to remove all the particulates that have burned and adhered to the surrounding particulates one after another by the combustion heat generated by this combustion. Accordingly, in the invention of claim 2, since heat is generated only magnetic material interspersed into particles on filter table surface can be reduced energization of the induction heating coil, it is possible to eliminate the waste of heating energy.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of an exhaust emission control device for an internal combustion engine according to the present invention will be described below with reference to the drawing of FIG.
Exhaust gas discharged from an internal combustion engine (for example, a gasoline engine) mounted on the vehicle is discharged outside the vehicle through the exhaust pipe 30. In order to purify harmful components HC, CO, and NOx contained in the exhaust gas, an induction heat generation type catalyst device 1 as shown in FIG. 1 is provided in the exhaust pipe 30 as an exhaust purification device. In this induction heat generation type catalyst device 1, reference numeral 2 denotes an induction heat generation type honeycomb monolith catalyst, which is supported on the converter case 3 via a seal 4 and a cushion 5. The seal 4 is for preventing the exhaust gas from being blown through the outside of the monolith catalyst 2, and is provided at an upstream portion of the converter case 3 in the exhaust gas flow direction. The cushion 5 elastically supports the monolithic catalyst 2 on the converter case 3 and prevents damage due to vibration thereof, and is formed of a wire net, and is provided on the downstream side of the seal 4. It has been. Further, a coil 7 and a pair of electrodes 9a and 9b for generating an alternating magnetic field in the entire monolith catalyst are provided on the monolith catalyst 2 side in the seal 4 and the cushion 5, and the electrodes 9a and 9b are connected to the battery 11 and the high frequency. The generating means 12 is connected. In FIG. 1, white arrows indicate the flow direction of the exhaust gas, and the converter case 3 is formed in a cone shape on the upstream side and the downstream side, whereby the exhaust gas is transferred to the monolith catalyst 2. It can be made to flow so as to spread over the entire surface.
[0012]
Further, a temperature detection terminal 13 for detecting an exhaust gas temperature (or catalyst temperature) passing through the monolith catalyst 2 and an exhaust gas temperature (catalyst temperature) at the start of the engine based on the temperature detected by the temperature detection terminal 13. ) Is provided with energization control means 14 for energization until a predetermined value (for example, 300 ° C.) is reached.
[0013]
As seen from the exhaust gas flow direction as shown in FIG. 2, the monolith catalyst 2 is composed of a space 17 serving as an exhaust gas passage and a grid-like carrier 16 made of cordierite. A coil 7 is concentrically formed on the outer periphery of the monolith catalyst 2.
[0014]
Further, FIG. 3 shows an enlarged view of a contact surface between the exhaust gas passage 17 through which the exhaust gas passes and the carrier 16. In order to improve the purification performance by increasing the contact area between the exhaust gas and the carrier 16, the surface of the carrier 16 has a porous structure (pores 18). The catalyst metal particles 20 and the magnetic particles 21 are mixed and supported on the carrier surface including the pore surface 19 inside the pores 18. The catalyst metal particles carry at least one kind of platinum, rhodium, palladium, etc., which are white metal metals, and the magnetic particles 21 are magnetite or iron.
[0015]
Next, specific control and operation in the catalyst purification apparatus 1 will be described. When it is detected that the engine has been started after it is cold, the high frequency generator 12 is activated. The high frequency generating means 12 applies a high frequency (10 to 100 MHz) as an exciting coil to the coil 7, whereby an alternating magnetic field is formed in the entire carrier 16. Each magnetic particle present in the alternating magnetic field is induced by an electromagnetic induction action as an electric resistor, an induced current flows, and Joule heat is generated. In particular, by optimizing the frequency, a large amount of induced current flows on the surface of the magnetic particles, so that the heating temperature is higher as the particle surface. FIG. 10 shows the temperature rise characteristics of the solenoid coil with respect to this heating temperature rise. In FIG. 10, a 200 KHZ / 5 KW alternating current is applied to the solenoid coil, and the temperature rise is measured by a thermocouple in which iron fine particles (50 to 200 μm) are applied as magnetic fine particles to the center and ends of the solenoid coil. is there. Thus, by supplying an alternating current for about 8 seconds, the surface of the magnetic particles becomes high temperature (250 ° C. or higher), the space and the carrier in the vicinity of the magnetic particles are heated, and heat is conducted to the low-temperature catalyst metal particles. Communicated. As a result, the temperature of the catalyst particles rises to the activation temperature early, and decomposes HC, CO, etc. in the exhaust gas. The catalyst temperature further rises due to the reaction heat and heat received from the exhaust gas at this time, and the entire catalyst quickly reaches the activation temperature. This temperature rise is detected by the temperature detection terminal 13. For example, when the exhaust gas temperature exceeds 300 ° C., the energization control means 14 cuts off the energization by a signal from the temperature detection terminal 13, and the heating by the magnetic particles is finished. To do. In FIG. 10, the magnetic particles have a size of 50 to 200 μm, but a temperature rise characteristic may be obtained which may be fine particles having a size on the order of nm.
[0016]
Next, a second embodiment of the exhaust emission control device for an internal combustion engine of the present invention will be described based on the drawings of FIGS.
52 denotes an exhaust manifold connected to the diesel engine, 53 denotes a filter casing connected to the exhaust manifold 52, and 54 denotes a filter made of porous ceramic inserted into the casing 53. A coil 48 and a pair of electrodes 49 a and 49 b for generating an alternating magnetic field are provided on the outer peripheral surface of the filter 54, and the electrodes 49 a and 49 b are connected to the battery 47 and the high frequency generator 46. . Further, a seal member 55 and steel wool 56 are inserted between the outer peripheral surface of the filter 54 and the inner peripheral surface of the casing 53 in order to prevent exhaust gas from being blown through. As shown in the figure, the filter 54 has a honeycomb structure including a plurality of cells 58a and 58b extending in parallel with each other with a thin wall 57 in the filter axial direction. As shown in FIGS. 6 and 7, each cell 58a, 58b has a square cross-sectional shape. Further, as can be seen from FIG. 8, each cell 58a, 58b is alternately inserted into one end by plugs 59a, 59b. Blocked.
In FIGS. 5 to 7, the plugs 59a and 59b are indicated by hatching. In such an exhaust gas filter, the exhaust gas flowing into the cell 58a from the upstream side of the filter (left side of FIG. 8) passes through the thin wall 57 made of porous ceramic as shown by the arrow in FIG. It flows into the adjacent cell 58b and then flows out from the rear opening of the cell 58b. Particulates contained in the exhaust gas are collected by the thin wall 57 when the exhaust gas passes through the thin wall 57. Here, the particulate mainly consists of solid carbon fine particles (SOOT) and an organic solvent soluble component (SOF).
[0017]
FIG. 9 shows the thin wall 57 in detail. The thin wall 57 is composed of innumerable pores 62 that allow the exhaust gas to pass through in order to filter the particulates contained in the exhaust gas, and innumerable magnetic particles 63 are attached to the surface of the pores 62. Yes. The exhaust gas passes from the cell partition wall 60 on the exhaust gas inlet side to the cell partition wall 61 on the exhaust gas outlet side as indicated by an arrow. Further, countless magnetic particles 63 are attached to the cell partition wall 60 on the exhaust gas inlet side. The size of the pores is set to a size that allows particulates to flow. Specifically, the average particle size of the particulates is 10 to 30 nm, and the particulates are usually connected in a straight chain, so that the pore size is preferably larger than this, preferably 25 to 40 μm. Degree. In addition, since the pores are connected to each other through a narrow passage, even if the pore size is quite large, the pores are trapped in the passage and hardly pass through the partition wall. Furthermore, in order to put more particulates into the pores, it is more preferable to increase the size of the pores on the exhaust gas inlet side and reduce the size of the pores on the exhaust gas outlet side.
[0018]
Particulates contained in the exhaust gas are trapped (attached) by the pores or the surface of the exhaust gas inlet side wall. When the diesel engine is operated for a predetermined period, the surface is gradually piled up by the particulates, covering the magnetic particles and gradually reducing the passage area of the exhaust gas. As a result, the flow resistance for passing the exhaust gas increases, and it is determined that the trapped particulates should be removed by combustion. Here, as a judgment means for removing the combustion, it may be judged that the combustion should be removed when the mileage of the vehicle or the operation time of the diesel engine is a predetermined value or more, or a pressure sensor is provided in the upstream exhaust pipe of the particulate filter. Further, it may be determined that the combustion should be removed when the detected value of the pressure sensor is equal to or greater than a predetermined value. When it is determined by the above means that the particulates should be burned and removed, the high frequency generator 46 is operated to apply a high frequency (10 to 100 MHz) as an exciting coil to the coil 48, thereby generating an alternating magnetic field in the entire filter. Let A voltage is induced in each magnetic particle existing in the alternating magnetic field by an electromagnetic induction action as an electric resistor, and an induced current flows. Then, Joule heat is generated by this induced current. In particular, by optimizing the frequency, a lot of induced current flows on the surface of the magnetic particles, so that the heating temperature is higher as the particle surface. When the alternating magnetic field is continuously generated for a predetermined period, the particulates attached around the magnetic particles start to be heated and burned. It is possible to remove all the particulates that have burned and adhered to the surrounding particulates one after another by the combustion heat generated by this combustion. The operating time of the high-frequency generator 46 is set to a value determined in advance through experiments or the like so that all the particulates of the particulate filter are burned and removed.
[0019]
【The invention's effect】
According to the invention described in each claim, when heating the exhaust gas purification device for removing harmful substances of exhaust gas by induction heat generation, the amount of heating heat is locally and efficiently applied to a portion requiring a temperature increase. Therefore, energy required for heating can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a catalyst device showing a first embodiment. FIG. 2 is a cross-sectional view of the catalyst device of FIG. 1. FIG. Fig. 4 is a detailed cross-sectional view. Fig. 4 is a schematic configuration diagram of a filter device showing a second embodiment. Fig. 5 is a perspective view of the filter of Fig. 4. Fig. 6 is a line AA in Fig. 4. Fig. 7 is a side view of a part of the filter end surface taken along the line. Fig. 7 is a side view of a part of the filter end surface taken along the line BB of Fig. 4. Fig. 8 is an axial cross section of the filter of Fig. 4. FIG. 9 is a detailed cross-sectional view of the portion of the present invention in the filter device of FIG. 4. FIG. 10 is a temperature rise characteristic diagram due to induction heat generation.
DESCRIPTION OF SYMBOLS 1 ... Catalyst apparatus 2 of internal combustion engine ... Monolith catalyst 16 ... Carrier 17 ... Space 18 ... Fine pore 19 ... Fine pore surface 20 ... Catalytic metal particle 21 ... Magnetic substance particle 54 ... Filter 60 ... Cell partition wall 61 on the exhaust gas inlet side Cell partition wall 62 on the exhaust gas outlet side ... pore 63 ... magnetic particles

Claims (2)

A catalyst for purifying exhaust gas is provided in an exhaust pipe of an internal combustion engine. The catalyst includes a catalyst carrier, catalyst metal particles dispersedly supported on the surface of the carrier, and an induction heating coil for flowing an induction current. Further, the catalyst is composed of a magnetic body that generates heat by an induced current, and when the temperature of the catalyst is to be raised, coil induction control means for heating the magnetic body by operating the induction heating coil is provided. In the induction heat purification device for an internal combustion engine, the catalyst support is made of a non-magnetic material, and the magnetic material is scattered in the vicinity of the catalyst metal particles on the surface of the catalyst support. Exothermic purification device. Filter is provided for collecting particulates in exhaust gas in an exhaust pipe of an internal combustion engine, the filter is made of non-magnetic material, the induction heating coil for supplying an induced current is attached to the filter, Coil energization control means for heating the magnetic material by operating the induction heating coil when the magnetic material that generates heat by the induced current is scattered in the form of particles on the surface of the filter and the particulates of the filter are to be burned. induction heating type purification apparatus for an internal combustion engine, wherein the kite comprising a.

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