JPH04102460U - alcohol concentration sensor - Google Patents

Abstract

(57) [Summary] [Purpose] A sensor that detects alcohol concentration by detecting changes in capacitance between an outer electrode through which fuel passes and an inner electrode can be miniaturized and have a large capacitance. The aim is to improve detection accuracy. [Structure] A hollow center electrode 24 extending along the central axis is inserted inside the cylindrical portion 2, and a rear end portion 24b of the center electrode 24 is supported through the bush 9 and the O-ring 10.
Further, the center electrode 24 is provided with a plurality of communication holes 28 near the opening 2a, which communicate the inner space 25 of the center electrode 24 with the space 26 between the cylindrical portion 2 and the center electrode 24. [Effect] Since the center electrode 24 is formed hollow, it has a large section modulus and therefore high strength, so its diameter can be increased, the electrode spacing d can be reduced, and the capacitance C can be increased. Furthermore, the alcohol concentration sensor 21 itself can be made smaller.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

The present invention relates to an alcohol concentration sensor, and particularly to a capacitive type sensor.

0002

[Conventional technology]

In recent years, methanol and ethanol have been added to gasoline as alternative fuels for automobile internal combustion engines. An alcohol-mixed fuel containing alcohols such as alcohols has been proposed. When using such alcohol mixed fuel, the stoichiometric air-fuel ratio depends on the alcohol concentration. Since the alcohol concentration changes, the alcohol concentration of the supplied alcohol-mixed fuel is detected and It is necessary to control the fuel supply amount and ignition timing based on the alcohol concentration of For example, see Japanese Unexamined Patent Publication No. 56-958540).

0003 Therefore, the fuel supply passage of the internal combustion engine is equipped with a An alcohol sensor configured with a capacitive alcohol concentration sensor that outputs voltage. Alcohol concentration detection devices are known, and capacitance type alcohol concentration sensors have been proposed. ing. This capacitive alcohol concentration sensor has conventionally been configured as shown in Figure 2. Ru.

0004 That is, the cylindrical housing 1 that constitutes a part of the fuel supply passage of the engine is connected to the outer electrode. The central axis of the cylindrical portion 2 with respect to the opening 2a formed in the middle of the cylindrical portion 2 and a cylindrical portion 3 connected in a direction orthogonal to the cylindrical portion 3. At one end of the cylindrical part 2 there is a diagram. The fuel inlet section 4 to which a fuel pipe (not shown) is connected is opened, and the opposite end of the cylindrical section 3 is opened. A fuel outlet portion 5 to which a fuel pipe (not shown) is similarly connected is opened. Cylinder part 2 A solid center electrode 6 extending along the central axis is inserted inside the center electrode. 6 is located a predetermined distance downstream from the fuel inlet section 4, and the rear end is located at the rear of the cylinder section 2. via an insulator 7 fitted to the inner peripheral surface of the end and a pipe 8 made of a conductive member. It is penetrated and supported by a bush 9 and an O-ring 10 fitted to the inner circumferential surface of the rear end of the cylindrical portion 2. . The protruding end of the center electrode 6 from the bush 9 is composed of a washer 11 and a nut 12. It is fixed by a fastener 13.

[0005] One end of the terminal 14 is clamped and fixed at the joint between the pipe 8 and the bush 9. This terminal 14 is connected to the cylindrical portion 2, that is, the outer electrode 2 via the pipe 8. . Also, one end of the terminal 15 is clamped and fixed at the joint between the fastener 13 and the bush 9. This terminal 15 is connected to the center electrode 6. Then, connect the terminals 14 and 15 directly to an AC power source and a resistor (both not shown). The capacitance C between electrodes 2 and 6 changes depending on the alcohol concentration in the fuel. By measuring the output voltage across the resistor, the Detect alcohol concentration. In addition, the capacitance C is determined as shown in the following formula. .

[0006] C=K×s×ε/d... However, s is the electrode area d is the electrode spacing between the center electrode 6 and the outer electrode 2 ε is the dielectric constant of the detected fuel K is a proportionality constant.

[0007]

[Problem that the idea aims to solve]

In order to accurately control fuel supply amount and ignition timing based on alcohol concentration, It is necessary to accurately measure the amount of methanol. By the way, improving measurement accuracy and performance To achieve this, in conventional alcohol concentration sensors, the capacitance C must be increased. It is necessary.

[0008] Here, in such a conventional alcohol concentration sensor, the capacitance C is increased. As is clear from the formula, in order to The electrode area s can be increased by increasing the length L, or the center electrode 6 can be made thicker. The electrode spacing d can be reduced by making the outer electrode 2 narrower or by making the outer electrode 2 thinner. However, in the former case, the cylindrical housing 1 becomes large and However, the concentration sensor itself has become too large to meet the needs for miniaturization. The center electrode 6 is supported in a cantilevered state by the insulator 7 and the bush 9. Therefore, the strength of the center electrode 6 in the support portion also tends to be insufficient. Cantilevered again As the distance increases, there is a risk that the product will become more susceptible to vibrations, so take measures to prevent vibrations. The need arises, leading to increased costs.

[0009] On the other hand, in the latter case, if the electrode spacing d is reduced, the dust contained in the fuel There is a risk that impurities such as these may become clogged between the outer electrode 2 and the center electrode 6, resulting in poor fuel flow. There is. Therefore, in view of the above-mentioned conventional problems, the present invention has been developed to achieve miniaturization and reduce capacitance. The present invention also aims to provide a large alcohol concentration sensor.

0010

[Means to solve the problem]

Therefore, the present invention detects changes in capacitance between electrodes through which fuel passes. At one end, an alcohol concentration sensor outputs a voltage corresponding to the alcohol concentration. a cylindrical outer electrode constituting a part of a fuel supply passage with one end closed and the other end open; a hollow center electrode extending from the closed end side along the central axis inside the outer electrode; a fuel inlet/outlet connected to an opening formed in the middle of the outer electrode; Configure.

[0011] Further, an inner cavity of the center electrode is provided in the center electrode near the opening formed in the outer electrode. A plurality of communication holes may be provided to communicate between the space and the external space.

0012

[Effect]

In such a configuration, a part of the fuel supply passage with one end closed and the other end open is Fuel passes between the cylindrical outer electrode and the hollow center electrode, and the outer electrode and the inner Detects changes in capacitance between heart electrodes and outputs voltage corresponding to alcohol concentration The fuel then flows out from an opening formed in the middle of the outer electrode.

[0013] Here, since the center electrode is hollow, its section modulus is larger than if it were solid. Since it is small and has high strength, it is possible to increase its diameter. Therefore solid The electrode spacing d is reduced compared to the case where the capacitance C is increased. In addition, if you want to maintain the same capacitance, make the center electrode hollow. Since it is possible to reduce the electrode spacing d compared to the case where the electrode area is It is possible to shorten the detection length of the center electrode, which corresponds to The sensor itself can be made smaller.

[0014] Further, an inner cavity of the center electrode is provided in the center electrode near the opening formed in the outer electrode. If multiple communication holes are provided to communicate between the inner space of the center electrode and the outer space, The inflowing fuel flows out into the external space through the plurality of communication holes, and the fuel flows through the openings. The fuel will flow out to the entrance and exit, ensuring a sufficient fuel passage.

[0015]

【Example】

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. In the following explanation, the overall configuration of the alcohol concentration sensor is based on the conventional example. Since it is similar to Figure 2, its explanation will be omitted, and the same elements as in Figure 2 will be given the same reference numerals. Add numbers to simplify explanations.

[0016] In the alcohol concentration sensor 21 shown in Figure 1, a part of the fuel supply passage of the engine is configured. The cylindrical housing 1 includes a cylindrical portion 2 that serves as an outer electrode, and a cylindrical portion 2 formed in the middle of the cylindrical portion 2. a fuel outlet connected to the opening 2a in a direction perpendicular to the central axis of the cylindrical portion 2; It is composed of a cylindrical portion 3 and a cylindrical portion 3. A fuel pipe (not shown) is connected to one end of the cylindrical portion 2. A fuel inlet section 4 connected to the connection is opened, and a fuel inlet section 4, which is also not shown, is opened at the opposite end of the cylindrical section 3. A fuel outlet portion 5 to which a fuel pipe is connected is opened.

[0017] Here, as a configuration according to the present invention, inside the cylindrical portion 2, there is a portion extending along the central axis thereof. A hollow center electrode 24 is inserted, and the tip 24a of the center electrode 24 is connected to the fuel inlet. The rear end portion 24b is located a predetermined distance downstream from the portion 4, and the rear end portion 24b is fitted into the inner circumferential surface of the rear end portion of the cylindrical portion 2. The inner circumferential surface of the rear end of the cylindrical portion 2 is It is supported through a bush 9 and an O-ring 10 which are fitted into the bush 9 and the O-ring 10.

[0018] Further, in the center electrode 24, an inner space 25 of the center electrode 24 is provided at a position near the opening 2a. A plurality of communication holes 28 are provided to communicate the space 26 between the cylindrical portion 2 and the center electrode 24. There is. According to this configuration, the fuel flowing in from the fuel inlet portion 4 flows into the space 26, that is, the outer electrode. Fuel passes between the pole 2 and the hollow center electrode 24, and between the outer electrode 2 and the center electrode 24. Detects the change in capacitance C and outputs a voltage corresponding to the alcohol concentration to open the aperture. It flows out from 2a through the cylindrical part 3.

[0019] Here, since the center electrode 24 is formed hollow, it has a large section modulus and therefore has high strength. Therefore, it is possible to increase the diameter φD. Therefore, the diameter of the cylindrical portion 2 is limited. Even in the case of At the same time, the detection length L of the center electrode 24 corresponding to the electrode area is shortened. As a result, the alcohol concentration sensor 21 itself can be made smaller.

[0020] Furthermore, the center electrode 24 becomes more robust against vibrations, etc., thereby extending the cantilever distance. Therefore, there is no need to take measures against vibration, leading to cost reduction. In addition, some of the fuel flows into the internal space 25 of the center electrode 24 from the fuel inlet portion 4 and It flows out into the space 26 from the communication hole 28 and flows out from the opening 2a through the cylindrical part 3. Since a sufficient fuel passage is secured, impurities such as dust mixed in the fuel can be removed. It can also prevent clogging.

[0021] Therefore, according to this embodiment, the alcohol concentration sensor 21 itself can be made smaller. Therefore, it becomes possible to increase the capacitance C by reducing the electrode spacing d, etc. The measurement of alcohol concentration by the alcohol concentration sensor 21 becomes accurate, and the It becomes possible to accurately control the fuel supply amount and ignition timing based on the fuel concentration. Although the present invention has been explained above with reference to specific embodiments, the present invention is not limited to this. The present invention is not limited to this invention by experts in the relevant technical field. Various changes and modifications may be made without departing from the scope of the attached utility model registration claims. It should be noted that this is possible.

[0022]

[Effect of the idea]

As explained above, according to the alcohol concentration sensor according to the present invention, the center electrode is hollow, and a plurality of By providing a communication hole, the sensor itself can be miniaturized and accurate alignment can be achieved. The amount of fuel supplied can now be measured and controlled based on alcohol concentration. This has a great practical effect of optimizing the engine speed and ignition timing.

[Brief explanation of drawings]

[Fig. 1] Partial cross-sectional front view of an embodiment of the alcohol concentration sensor of the present invention.

[Fig. 2] Partially sectional front view of an example of a conventional alcohol concentration detection device

[Explanation of symbols]

1 Cylindrical housing 2 Cylindrical part (outer electrode) 2a opening 3 Cylinder part 4 Fuel inlet 24 Center electrode 25 Interior space 26 Space 28 Communication hole

Claims (2)

[Scope of utility model registration request] Claim 1: An alcohol concentration sensor that outputs a voltage corresponding to alcohol concentration by detecting changes in capacitance between electrodes through which fuel passes, the fuel supply having one end closed and the other end open. A cylindrical outer electrode constituting a part of the passage, a hollow center electrode extending from the closed end side along the central axis inside the outer electrode, and an opening formed in the middle of the outer electrode. An alcohol concentration sensor comprising: a connected fuel inlet/outlet; 2. The alcohol according to claim 1, wherein the center electrode near the opening formed in the outer electrode is provided with a plurality of communication holes that communicate the inner space and the outer space of the center electrode. Concentration sensor.