JP2532683Y2 - Alcohol sensor - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alcohol sensor for an internal combustion engine or the like, and more particularly to a technique for stabilizing output characteristics by improving the structure of a liquid-tight seal portion of a center electrode.

[0002]

2. Description of the Related Art In recent years, an alcohol-mixed fuel obtained by mixing alcohol such as methanol and ethanol with gasoline has been proposed as an alternative fuel for an internal combustion engine for an automobile. When such an alcohol-mixed fuel is used, since the stoichiometric air-fuel ratio changes according to the alcohol concentration, the alcohol concentration of the supplied alcohol-mixed fuel is detected, and the fuel supply amount control and the ignition timing control are performed based on the alcohol concentration. (See, for example, JP-A-56-958540).

[0003] Therefore, there has been proposed a capacitance type alcohol sensor which outputs a voltage corresponding to the alcohol concentration in a mixed fuel to a fuel supply passage of an internal combustion engine. This capacitance type alcohol sensor is conventionally configured as shown in FIG. That is, the cylindrical housing 1 constituting a part of the fuel supply passage of the engine includes a cylindrical portion 2 serving as an outer electrode and a central axis of the cylindrical portion 2 with respect to an opening formed in the middle of the cylindrical portion 2. And a cylindrical portion 3 connected in a direction perpendicular to the direction. A fuel inlet, to which a fuel pipe (not shown) is connected, is opened at one end of the tubular section 2, and a fuel outlet, to which a fuel pipe (not shown) is connected, is also opened at the opposite end of the tubular section 3. You. A central electrode 6 extending along the central axis of the cylindrical portion 2 is inserted into the cylindrical portion 2, and a front end portion of the central electrode 6 is located a predetermined distance downstream from the fuel inlet portion 4, and a rear end portion of the central electrode 6 is located in the cylindrical portion 2.
The cylindrical portion 2 is penetrated and supported by a 0 ring 10 made of fluoro rubber and a bush 9 fitted to the inner peripheral surface of the rear end portion through a protector 7 made of Teflon fitted to the inner peripheral surface of the rear end portion. The end of the center electrode 6 protruding from the bush 9 is a nut 1
It is fixed by a fastener such as 1. And the outer electrode 2
And a terminal (not shown) connected to the center electrode 6, a constant voltage power supply, and a resistor are connected in series to utilize the fact that the capacitance between the electrodes 2, 6 changes according to the alcohol concentration in the fuel. Then, by measuring a voltage based on a signal from the sensor, the alcohol concentration in the fuel is detected.

[0004]

However, in such a conventional alcohol sensor, the O-ring 1
Although the liquid-tight sealing of the rear end side of the cylindrical portion 2 is performed by 0, the distance between the outer peripheral surface and the inner peripheral surface of the protector 7 and the inner peripheral surface of the cylindrical portion 2 and the outer peripheral surface of the center electrode 6 is zero. The fuel may enter the space in which the ring 10 is interposed, and the invading fuel may come into contact with the O-ring 10, and the O-ring may gradually absorb the fuel and swell.

As shown in FIG. 4, as a result of the 0 ring 10 absorbing fuel and swelling, the capacitance between the electrodes 2 and 6 is changed by the amount of methanol absorbed in the fuel, and the output characteristic is reduced. Therefore, there has been a problem that the amount of methanol cannot be measured accurately, and the fuel supply amount and ignition timing controlled based on the alcohol concentration cannot be optimized.

In view of the above-mentioned conventional problems, the present invention reduces the swelling of the O-ring and suppresses the change in the output characteristics by adopting a configuration that minimizes the penetration of fuel into the interposed portion of the O-ring. It is an object of the present invention to prevent and detect an accurate alcohol concentration.

[0007]

For this reason, the alcohol sensor of the present invention has a configuration in which a center electrode is inserted along a central axis into a cylindrical portion serving as a fuel supply passage and functioning as an outer electrode. An alcohol sensor that detects the alcohol concentration in the fuel by utilizing the change in the capacitance between the outer electrode and the center electrode according to the alcohol concentration. The end of the center electrode is fixedly held. A cylindrical protector having a through hole through which the center electrode passes is fitted to the inner peripheral surface of the end of the cylindrical portion fixed via the means, and a center electrode between the protector and the fixed holding means. In an alcohol sensor having an O-ring interposed between an outer peripheral surface and an inner peripheral surface of a cylindrical portion, an annular ring contacting the inner peripheral surface of the cylindrical portion and the outer peripheral surface of the center electrode respectively with the outer peripheral surface and the inner peripheral surface of the protector. Thereby projecting form part, a structure of forming the end face of the 0-ring side of the protector in a concave curved surface.

[0008]

In this configuration, when the protector is fitted to the inner peripheral surface of the cylindrical portion, the rib portion is pressed against the inner peripheral surface of the cylindrical portion and deformed. In this case, the pressure contact area between the rib portion and the inner peripheral surface of the cylindrical portion is small, and the rib portion is pressed against the inner peripheral surface of the cylindrical portion with high pressure to perform reliable sealing. In a state where the center electrode passes through the through hole of the protector, the rib portion is deformed by pressing against the outer peripheral surface of the center electrode. In this case, the pressure contact area between the rib portion and the outer peripheral surface of the center electrode is small, and the rib portion is pressed against the outer peripheral surface of the center electrode with high pressure to perform reliable sealing.

On the other hand, as a result of forming the end surface on the O-ring side of the protector into a concave curved surface, the space between the end surface and the outer peripheral surface of the O-ring, that is, the dead volume, is smaller than when the end surface is flat. Is reduced. As a result, when fuel enters the space, the amount of fuel that contacts the O-ring can be reduced.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the accompanying drawings. In the drawings referred to below, the same elements as those in FIG. FIG.
In the configuration, the center electrode 6 is inserted along the center axis of the cylindrical portion 2 serving as a fuel supply passage and functioning as an outer electrode, and the outer electrode 2 and the center electrode 6 are connected in accordance with the alcohol concentration in the fuel. The configuration for detecting the alcohol concentration in the fuel by utilizing the change in the capacitance between them is the same as the conventional one.

The end of the center electrode 6 is fixed through a bush 9, a nut 11 or the like as a fixing and holding means. The structure in which the protector 17 is fitted and the O-ring 11 is interposed between the outer peripheral surface of the center electrode 6 and the inner peripheral surface of the cylindrical portion between the protector 17 and the fixed holding means is the same as the conventional one.

The structure different from the conventional one is that the protector 17 has annular rib portions 18 and 19 which are in contact with the inner peripheral surface of the cylindrical portion 2 and the outer peripheral surface of the center electrode 6 on the outer peripheral surface and the inner peripheral surface, respectively. That is, the end face of the protector 17 on the O-ring 10 side is formed as a concave curved surface 20 (see FIG. 2). Here, the rib portion 18 is formed at a substantially intermediate position in the axial direction on the outer peripheral surface of the protector 17. or,
The rib portion 19 is formed at a substantially intermediate position in the axial direction of the small-diameter through-hole 17b among the large-diameter and small-diameter through-holes 17a and 17b of the protector 17.

The ribs 18 and 19 have a triangular cross section and an acute angle at the tip. According to such a configuration, in a state where the protector 17 is fitted to the inner peripheral surface of the cylindrical portion 2, the rib portion 18 is pressed against the inner peripheral surface of the cylindrical portion 2 and deformed. In this case, the pressure contact area between the rib portion 18 and the inner peripheral surface of the cylindrical portion 2 is small, and the rib portion 18 is pressed against the inner peripheral surface of the cylindrical portion 2 with a high pressure to perform reliable sealing.

The through holes 17a, 1 of the protector 17
In a state where the center electrode 6 penetrates through the rib 7b,
Are pressed against the outer peripheral surface of the center electrode 6 and deformed. In this case, the pressure contact area between the rib portion 19 and the outer peripheral surface of the center electrode 6 is small, and the rib portion 19 is pressed against the outer peripheral surface of the center electrode 6 with a high pressure to perform reliable sealing. On the other hand, 0 ring 1 of protector 17
As a result of forming the end surface on the zero side into the concave curved surface 20, the space between the end surface and the outer peripheral surface of the O-ring 10, that is, the dead volume is reduced as compared with the case where the end surface is a flat surface. As a result, when fuel enters the space, the O-ring 1
The amount of fuel that comes into contact with zero can be reduced.

As described above, the liquid-tight sealing function of the protector 17 is improved, and the amount of fuel in contact with the O-ring 10 can be reduced. As a result, the swelling of the O-ring 10 by absorbing the fuel can be reduced. In addition, a change in capacitance between the electrodes 2 and 6 can be reduced, and a change in output characteristics can be suppressed as much as possible. Therefore, the amount of methanol can be accurately measured, and the fuel supply amount and the ignition timing controlled based on the alcohol concentration can be optimized.

Although the present invention has been described with reference to a specific embodiment as described above, the present invention is not limited to this, and is attached to the present invention by a person skilled in the art. It should be noted that various changes and modifications can be made without departing from the scope of the claimed utility model registration claim.

[0017]

As described above, according to the alcohol sensor according to the present invention, the structure of the protector is improved, the liquid-tight sealing function is improved, and the amount of fuel contacting the O-ring is reduced. As a result, it is possible to alleviate the swelling of the O-ring by absorbing the fuel, to suppress the change in the output characteristics as much as possible, and to increase the practical effect of being able to accurately measure the alcohol concentration. Things.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment of the alcohol sensor of the present invention.

FIG. 2 is a sectional view of the protector of the embodiment.

FIG. 3 is a cross-sectional view of an example of a conventional alcohol sensor.

FIG. 4 is a characteristic diagram illustrating a conventional problem of the relationship between the methanol concentration and the capacitance.

[Explanation of symbols]

 2 cylindrical part (outer electrode) 6 center electrode 9 bush 100 ring 11 nut 17 protector 18 rib part 19 rib part 20 curved surface

Claims (1)

(57) [Scope of request for utility model registration] 1. A structure in which a center electrode is inserted along a center axis of a cylindrical portion serving as a fuel supply passage and functioning as an outer electrode. An alcohol sensor for detecting an alcohol concentration in fuel by utilizing a change in capacitance, wherein an inner periphery of a cylindrical portion end portion is fixed to an end portion of a center electrode via fixing holding means. The surface is fitted with a cylindrical protector having a through hole through which the center electrode penetrates, and an O-ring is provided between the outer peripheral surface of the center electrode and the inner peripheral surface of the cylindrical portion between the protector and the fixed holding means. In the interposed alcohol sensor, annular protectors which are in contact with the inner circumferential surface of the cylindrical portion and the outer circumferential surface of the center electrode are formed on the outer circumferential surface and the inner circumferential surface of the protector, and the O-ring of the protector is formed. Alcohol sensor, characterized in that the end face of the formed concave curved surface.