JPH063140Y2 - Back pressure port structure of exhaust gas back pressure measuring device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an exhaust gas purifying device for a diesel engine, and more particularly, to a back pressure port structure of an exhaust back pressure measuring device for a diesel exhaust solid particulate collection device capable of filter regeneration. Regarding

[Background technology]

BACKGROUND ART An exhaust gas purifying device for purifying diesel exhaust gas by collecting solid particulate emissions such as exhaust black smoke particulates contained in the exhaust gas of a diesel engine is well known in the art. Such a purifying device is usually a trap using a heat-resistant porous filter such as ceramics.
It is composed of. An example of a conventional exhaust solid particulate collector system will be described with reference to FIG. 5, where 10 is a diesel engine, 12 is an exhaust manifold, and 14 and 16 are shown.
Is an exhaust pipe, and 18 is a collector. A monolithic filter 22 is housed in the housing 20 of the collector 18, so that solid particles in diesel exhaust gas can be collected mainly by the principle of collision collection.

When solid particles collected by the use of a collector accumulate in the filter, clogging of the filter increases the ventilation resistance and reduces the collection effect.Therefore, the filter must be regenerated at an appropriate time or periodically. I have to. Since the solid particles of diesel exhaust are mainly composed of carbon and are therefore flammable, it is possible to regenerate the filter by igniting a part of the solid particles accumulated in the filter, sequentially spreading the heat over the entire area of the filter, and then skipping it Is. Various methods of regenerating a filter are known. For example, a method of igniting solid fine particles by reducing the intake air amount by raising the exhaust gas temperature by reducing the engine intake system, and limiting the engine exhaust system There is a method of igniting the fine particles by increasing the fuel injection amount to raise the exhaust gas temperature, but in the conventional example of FIG. 5, the electric heater 24 is brought into contact with or close to the upstream end face of the filter 22.
The control circuit 26 closes the relay 28 at an appropriate time and energizes the heater 24 for a certain period of time to heat it, thereby igniting the solid fine particles in the filter.

The method for determining the filter regeneration time is to integrate the engine speed with an integrator and regenerate the filter when the integrated speed reaches a set value. The exhaust gas back pressure upstream of the collector is detected and the back pressure of the exhaust gas upstream of the collector is detected when the back pressure reaches the set value. There is a method to reproduce when the pressure reaches the set value, etc.,
Since the former two methods do not always accurately reflect the clogging of the filter, the latter two methods are the most rational. For example, in the example of FIG. 5, a back pressure detecting port 30 is bored in the exhaust pipe 14, a back pressure is guided to a back pressure sensor 34 by a back pressure transmission pipe 32, and a piezoelectric resistance element built in the sensor or The back pressure value is converted into a current value by a strain gauge, and the regeneration timing is detected by comparing this with a set value in the control circuit 26. In general, an introduction mouthpiece for taking in exhaust backpressure is attached to the detection port, and a backpressure transmission pipe is connected to this mouthpiece.

In this method of determining the filter regeneration timing by detecting the back pressure of the exhaust gas, the structure of the back pressure introducing cap attached to the back pressure detecting port formed in the exhaust pipe has a very important meaning. That is, during long-term use, solid fine particles in the exhaust gas and corrosive condensate components may act on the resistance element of the back pressure sensor to deteriorate the performance of the element. In addition, solid particles and condensate also adhere to the detection port and the inner wall surface of the back pressure transmission pipe. Is not transmitted and the reliability of the back pressure sensor is significantly impaired. Therefore, the back pressure introducing die must be capable of smoothly transmitting the exhaust gas pressure on the one hand and completely blocking solid fine particles and condensable components in the exhaust gas on the other hand.

Therefore, recently, a back pressure introducing portion structure has been already proposed in which a honeycomb filter is loaded in the detection port, and an electric heater is wound around the outer periphery of the honeycomb filter (for example,
No. 58-163617). According to this, exhaust particulates and the like in the exhaust gas are filtered by the honeycomb filter, and only clean exhaust gas enters the detection port. Fine particles and the like adhering to the honeycomb filter by filtration are incinerated by heating an electric heater, and thus the honeycomb filter is appropriately regenerated.

FIG. 6 shows an example of a conventional back pressure measuring device with a built-in heater.

In FIG. 6, a hollow protection cover pipe 41 is inserted in the lower portion of the housing 40, and the lower end of the protection cover pipe 41 is exposed to the exhaust gas of the exhaust pipe 14. A hollow ceramic heater 43 is fixed in the housing 40, and burns and removes exhaust particulates in the exhaust gas flowing through the hollow ceramic heater. The positive terminal 43a of the heater 43 is fixed to, for example, the tip of an inner pipe 44 attached to the housing 40 by welding or the like. A lead wire 45 connected to an external power source is connected to the inner pipe 44, so that the heater 43 can be energized. The inner pipe 44 is fixed and held in the rear cover 49 fixed to the housing 40 via the airtight holding talc ring 46, the ring pad 47, and the ring spacer 48 via the silicone rubbers 50 and 51. The inner pipe 44 is fixed by caulking the rear cover 49 together with the silicone rubbers 50 and 51 from the outside.

The ground potential of the heater 43 is formed by the housing 40.

[Problems to be solved by the invention]

In this conventional structure, the inner pipe 44 is made of silicone rubber 5.
Since it is fixed with a flexible material such as 0, 51, there is a problem that disconnection of the plus terminal 43a and peeling of the welded portion are likely to occur due to the influence of vibration of the engine or the like.

Further, when the silicon rubber deteriorates due to heat, the inner pipe 44, which is a positive electrode, may come into contact with the rear cover 49, which is a ground level, and short-circuit due to vibration. Conventionally, as described above, the inner pipe 44 is held by silicone rubber.
Since only the heaters 50 and 51 are used, the positive terminal 43a of the heater may come into contact with the ground potential portion such as the rear cover 49 unless it is welded to the inner pipe through an insulating pipe (not shown) such as alumina. However, when such an insulating tube is passed through, the terminal 43a is inevitably linear, which causes a problem of insufficient strength against tension.

The present invention solves the above problems and damages the heater terminal portion,
An object of the present invention is to provide a back pressure port structure having a simple structure that prevents insulation failure and has sufficient strength.

[Means for solving problems]

In order to achieve the above object, the back pressure port structure of the exhaust gas back pressure measuring device according to the present invention comprises a mouthpiece portion which constitutes an exhaust gas introduction passage which is exposed to the exhaust gas and introduces the exhaust gas, and the mouthpiece portion. It has a hollow housing having an outer tube that holds and guides the exhaust gas introduced from the mouthpiece to the outside, and a heater that is provided in the exhaust passage that connects the mouthpiece and the outer tube and that burns and removes adhered exhaust particulates. The heater terminal connecting the heater to an external power source is guided through a ceramic spacer into an inner pipe whose lower portion is fixedly held in the outer pipe, and is taken out of the inner pipe through a notch formed in the inner pipe. It is joined to the inner pipe.

〔Example〕

Embodiments of the present invention will be described below. FIG. 2 is an overall external view of a back pressure port structure of a back pressure measuring device according to an embodiment of the present invention. The external appearance is similar to that of FIG.
The description will be omitted by using the same part number.

FIG. 1 is an enlarged view of the internal structure of the portion A in FIG. The most important feature of the present invention is that the lower portion of the inner pipe 44 'is held by the ceramic spacer 60. That is,
The inner pipe 44 'is a cylindrical ceramic spacer 60.
It is fixedly held in the rear cover 49 via.

The ceramic spacer 60 is formed of a material having low thermal conductivity, such as ZrO ₂ . This ceramic spacer 6
In addition to preventing vibration of the inner pipe 44 ', 0 also has a role of positioning. That is, the inner pipe 44 'is positioned only by fitting it into the groove 60a formed in the ceramic spacer 60. The recessed groove 60a extends as a hole 60b corresponding to the terminal extraction protrusion 45a of the heater 43. The inner pipe 44 'is provided with a notch 63 at a position where it does not interfere with the ceramic spacer 60, and the positive terminal 43a of the heater 43 is once taken out from here and welded to the inner pipe 44'. At this time, the plus terminal 43a is provided with some allowance in the extending direction. An airtight silicon rubber 67 is attached to the top of the ceramic spacer 60. Since the silicon rubber 67 keeps the inner pipe 44 'and airtightness by caulking the rear cover (outer pipe) 49 as indicated by 69, the mounting position is important. Therefore, for example, a positioning leg (not shown) is attached to the bottom of the silicon rubber 67, and the position is determined by bringing the leg into close contact with the ceramic spacer 60.

On the other hand, connect the lead wire 45 to the lead wire holding silicone rubber 7
After passing through 1, the lead connector 73 is crimped. This is attached to the inner pipe 44 'as a plus side lead wire by welding, and the rear cover 49 is mounted over the whole (this assembly is hereinafter referred to as a heater assembly). Thereafter, as in the conventional case shown in FIG. 6, the protection cover 41 is put in the housing 40, and the heater heat generating portion 43 '(second
Assembling the heater assembly while confirming that the figure is in the center of the cover, attaching the airtight holding talc 46, the ring pad 47, and the ring spacer 48, and completely fixing them by curving. Finally 69,79
By caulking from the rear cover 49 at the portion, the vibration resistant back pressure port structure is completed. The heater 43 has a tubular shape and extends to a lower portion of the inner circumference of the protection cover 41 to form a heat generating portion.

If the plus terminal is not properly attached to the inner pipe 44, the heater does not work and the exhaust passage 60b is clogged, making pressure detection difficult. Therefore, as shown in FIG. 3, a reinforcing ring 80 is attached to the welded portion of the positive terminal 43a to the inner pipe.
May be provided. The reinforcing ring 80 presses the welded portion from above and prevents the welded portion from separating or coming off. This ring 80 is made of silicone rubber 6
Since the inner pipe 44 'is partially embedded in the inner pipe 44', the inner pipe 44 'is also prevented from coming off. FIG. 4 shows another embodiment in which one end 44a 'of the inner pipe 44' is widened toward the end and the ceramic spacer is divided into 60a and 60b so as to prevent the inner pipe from coming off. The lower end of the ceramic spacer 60a is the inner pipe 4
It has a taper shape corresponding to the end portion 44a 'of 4', and therefore the inner pipe 44 'is restricted in position in both directions in the longitudinal direction.

The inner pipe 44 'is connected to a back sensor (not shown) via a flexible hose (not shown) to supply back pressure.

[Effect of device]

As described above, according to the present invention, the ceramic spacer is provided between the inner pipe and the rear cover to reduce the vibration of the inner pipe, thereby improving the insulation between the heater positive terminal weld and the rear cover. Can be made.

In addition, by using a ceramic spacer for a completely insulating structure, the positive terminal of the heater is welded to the inner pipe through an insulating tube of alumina or the like as described above to prevent the possibility of contacting the ground potential part of the rear cover or the like. It is not necessary, and the degree of freedom of the direction of the lead wire is considerably increased, and a considerable improvement in durability against external factors such as vibration and shock can be expected.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a back pressure port structure according to the present invention, and FIG.
FIG. 3 is an overall external view of the cap structure of the back pressure measuring device, FIG. 3 is a view showing a modified embodiment of FIG. 1, FIG. 4 is a view showing still another embodiment of the present invention, and FIG. FIG. 6 is a conceptual view of an exhaust solid particulate collection device, and FIG. 6 is a cross-sectional view of a conventional back pressure introducing die. 40 ... Housing, 41 ... Protection cover (base part), 43 ... Heater, 44 '... Inner pipe, 49 ... Rear cover (outer pipe), 60 ... Ceramic spacer.

Claims (1)

[Scope of utility model registration request] 1. A hollow having a mouthpiece part that constitutes an exhaust gas introduction path that faces the exhaust gas and introduces the exhaust gas, and an outer tube that holds the mouthpiece part and guides the introduced exhaust gas from the mouthpiece part to the outside. It has a housing, and a heater provided in an exhaust passage connecting the base portion and the outer pipe to burn off adhering exhaust particulates, and a heater terminal connecting the heater to an external power source is below the heater via a ceramic spacer. Is introduced into an inner pipe fixedly held in the outer pipe, is taken out of the inner pipe through a notch formed in the inner pipe, and is joined to the inner pipe. Back pressure port structure.