JP2003201819A - Oil level sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oil level sensor with no fear of leakage of oil outside from a fetching part of a lead member while saving a space and simplifying a structure. <P>SOLUTION: This oil level sensor 200 has a sensor control circuit part 200a built in an oiling port cap KP and to detect, output and work when a conducting member 4 mounted on a float 1 makes contact with an oil tank S to close an oiling port of engine oil. The float 1 is connected to the oiling port cap KP by the lead member 2 free to float on a liquid level W. Output from the sensor control circuit part 200a in the oiling port cap KP is propagated to an ignition circuit of the engine through an outer detection route 12. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oil level sensor for detecting the amount of oil contained in an oil tank.

[0002]

2. Description of the Related Art Conventionally, for example, in a four-cycle engine for an automobile, an oil level is automatically detected by a float sensor or the like, and when the oil falls below a predetermined level, an oil indicator on the cockpit is turned on to give a warning. I am trying. Since the oil state detection unit that detects the amount of oil is usually arranged in the oil tank, the lead member that connects this oil state detection unit and the circuit provided outside the oil tank is connected to the oil tank. A structure to take it out is necessary.

[0003]

According to the above structure, since the main part of the circuit is arranged inside the case provided outside the oil tank, the space must be secured. However, most engines installed in lawnmowers, fellers, etc. have a small displacement (for example, 100 cc or less), and it is essentially difficult to secure an extra space. In addition, it can be said that if a thing such as a circuit case is attached to the outside in various ways, it hinders the operation, and if the circuit is conspicuous, it is likely to cause a failure due to contact or the like.

Furthermore, since it is necessary to devise a sure seal for preventing the engine oil from leaking out,
It tends to be structurally complicated. Considering that point,
I would like to avoid complicated structures if possible. If the structure becomes complicated, there is a cost disadvantage.

It is therefore an object of the present invention to provide an oil level sensor which is space-saving and simple in structure, and which is free from the risk of oil leaking out from the lead-out portion of the lead member.

[0006]

In order to solve the above problems, an oil level sensor according to the present invention detects an oil state that switches between an open state and a short circuit state in accordance with a change in the state of engine oil. Section, a sensor control circuit section that performs a detection output operation based on the detection result of the oil state detection section, and a circuit case that accommodates the sensor control circuit section in a form of being isolated from engine oil. Is incorporated in a filler cap that covers the filler port of engine oil, and the filler cap and the circuit case are combined.

According to the present invention, the circuit portion of the oil level sensor is incorporated in a cap (fuel filler cap) that covers the filler port for engine oil. The fuel filler cap is indispensable for an internal combustion engine even if it is intended to save space. The present invention focuses on that point, and saves space by incorporating a circuit portion in the filler cap, that is, by combining the circuit case covering the sensor control circuit portion with the filler cap. It is the one. Since the filler cap is conventionally attached to the oil tank of the engine, it does not interfere with the operation of the equipment. Moreover, the filler cap is usually made sturdy so that no oil leaks out. Therefore, even if the sensor control circuit unit is housed inside, it can be reliably protected, and it is possible to prevent problems such as failure due to impact being applied to electronic parts or the like that form the circuit unit, and problems related to the oil seal. Disappear. Furthermore, since it is not necessary to make a dedicated hole in the oil tank, it is possible to contribute to the reduction of the manufacturing cost therefor.

[0008]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. First, FIG. 1 is an overall view showing an oil level sensor of the present invention. The oil level sensor 200 includes a float switch 100 as an oil state detection unit including a lead member 2 and a float 1.
(Described later with reference to FIG. 3) and the float switch 100.
A sensor control circuit portion (see FIGS. 7 to 9) electrically connected to the fuel cell and a fuel filler cap KP (circuit case) that accommodates electronic components and the like that form the sensor control circuit portion. The sensor control circuit section is built in a filler cap KP that covers the filler port of the engine oil, and the filler cap KP and the circuit case are combined.

At a portion of the filler cap KP that should be located in the oil tank S, a float switch 100 as an oil condition detecting portion is connected to the filler cap KP, and the float switch 100 and the sensor control circuit portion are connected to each other. One end of the lead member 2 for obtaining continuity is connected. The other end of the lead member 2 is attached to the float 1 which is a member that constitutes the float switch 100 and is floated on the liquid surface W of the oil.
As described above, the sensor control circuit unit in the filler cap KP and the float switch 100, which is the oil state detection unit, are formed by an extremely simple structure in which only the lead member 2 is connected.
The continuity with is secured. Therefore, it can be manufactured at low cost. In the present specification, the lead member 2 is regarded as a member belonging to the float switch 100.

The float 1 can be taken out of the oil tank S as the filler cap KP is removed from the oil tank S. Therefore, even if a malfunction occurs in the float switch 100, repair is easy. In addition, since it is allowed to take out the float 1 to the outside of the oil tank S during refueling, it does not interfere with refueling.

Next, as shown in detail in FIG.
The float switch 100 can be provided in a lubricating oil tank of an internal combustion engine, a fuel tank, or a container such as a water supply tank. When the amount of liquid such as oil stored in the container S reaches a specified level or less, the float-side contact portion provided on the columnar float 1 floating on the liquid surface W is electrically connected to the container-side contact portion to give a signal. Is output. Specifically, this corresponds to the current output to the sensor control circuit unit when the float side contact unit is switched to the ground potential level. If the container S is made of a conductive material, the container S itself can also be used as the container-side contact portion. In the oil level sensor 200, the container S means the oil tank S.

The float 1 can be made of a resin material having excellent insulation, heat resistance and oil resistance. For example, a resin material obtained by subjecting NBR (nitrile butadiene rubber) to a foaming treatment to adjust the specific gravity to about 0.3 is suitable.

The float 1 is connected to the other end of a flexible lead member 2 having one end fixed to the container S (specifically, the filler cap KP), and the lead member 2 allows the float. The liquid surface W is allowed to float within the range. From the viewpoint of preventing a short circuit with the container S, it is desirable that the lead member 2 has a conductor portion covered with an insulating resin. Further, not limited to this, any long flexible member capable of being sufficiently bent by the weight of the float 1 may be used. For example, a mesh wire or a chain-shaped lead member may be used, but it is preferable. That a stable conduction state is ensured, and the container S
It is important that no short circuit occurs with.

The float 1 has a hole 1 formed therein.
A conductive shaft core 3 is inserted and fixed to a and 1b, and the tip end of the lead member 2 is electrically connected to one end of the shaft core 3. The holes 1a and 1b formed in the float 1 are formed as through holes penetrating in a direction substantially perpendicular to the liquid surface W in a stationary state, with the diameter increasing from the hole 1b to the hole 1a. . Connection part 23 between shaft core 3 and lead member 2
The shaft core 3 is prevented from slipping out in the insertion direction with respect to the hole 1b by adjusting the size so that it cannot be inserted into the hole 1b. Since the float 1 is usually made of a resin material, it is difficult to directly join it to the lead member 2. However, according to the above, the float 1 can be easily connected to the lead member 2 with the shaft 3 interposed therebetween.

A conductive member 4 as a float side contact portion is attached to the float 1 on the side opposite to the side exposed on the liquid surface W. By contacting the conducting member 4 with the container S made of a conductive material, it is possible to detect that the liquid surface W has reached a specified level or lower. Since the float side contact portion is a member separate from the shaft core 3, the degree of freedom of its shape is large, and various adjustments can be easily made to a shape in which electrical connection with the container S is easily ensured. Further, by attaching the conducting member 4, the center of gravity of the entire float 1 moves to the lower side of the liquid surface W, and the floating state of the float 1 on the liquid surface W is also stabilized. The end of the shaft core 3 on the opposite side of the connecting portion with the lead member 2 can be used as it is as the float side contact portion. This will be described later with reference to FIG.

Further, in the embodiment shown in FIG. 3, the shaft core 3 has a split pin shape, while the protruding portion of the shaft core 3 from the float 1 is folded back to form a pair of folded back portions 3.
The conductive member 4 is attached to the float 1 by holding the conductive member 4 in such a manner that the conductive member 4 is sandwiched between the conductive member 4 and the mounting surface 1c of the float 1, and as a result, the conductive member 4 and the lead member 2 are electrically connected. Is secured. That is, the conduction member 4 is sandwiched between the folded-back portion 3a of the split pin-shaped shaft core 3 and the mounting surface 1c of the float 1. The shaft core 3 not only obtains conduction between the lead member 2 and the conduction member 4, but also functions as a means for attaching the conduction member 4 to the float 1. In this way, by making the shaft core 3 into a split pin shape or adopting the split pin itself to the shaft core 3, a fastening member such as a screw for attaching the conductive member 4 is not necessary, and the cost can be reduced.
Assembly is also very simple, which is preferable.

As for the conductive member 4, it is desirable that the conductive member 4 has a substantially plate-like shape as a whole, and further has a protrusion 4t to be brought into contact with the container S first when the liquid level W further decreases. Then, as shown in FIG. 3, the conducting member 4 can be attached to the float 1 by penetrating the split pin-shaped shaft core 3 in the plate thickness direction and folding it back, which is very simple.

Further, if the conductive member 4 is plate-shaped, the area for forming the float side contact portion can be increased, and the holding using the folded-back portion 3a of the split pin-shaped shaft core 3 described above can be performed well. It can be realized stably.
Specifically, when the conducting member 4 is formed in a plate shape, the peripheral portion of the conducting member 4 is bent so as to extend substantially toward the container-side contact portion so as to be substantially perpendicular to the mounting surface 1c of the float 1, and the protrusion 4t is formed. Is forming. In this way, the plate-shaped conducting member 4
The contact resistance with respect to the container-side contact portion can be reduced by using the protrusion 4t as the float-side contact portion without forming the entire plate surface as the float-side contact portion. Further, if the peripheral portion of the conducting member 4 is the protrusion 4t, the plate surface positioned radially inward of the protrusion 4t is located at the folded portion 3a of the split pin-shaped shaft core 3 as described above. It can be effectively used as a holding part. In addition, it is desirable that the shape of the protrusion 4t is adjusted so that the protrusion 4t has a sawtooth shape toward the side in contact with the container side contact portion. By adjusting in this way,
This is because even if sludge or the like covers the inner surface of the container S that is the container-side contact portion, reliable conduction can be ensured through the sludge.

Further, it is desirable that the conducting member 4 is adjusted so as to extend outward from the outer peripheral edge of the mounting surface 1c of the float 1 to which it is fixed. That is, in the float 1, the side exposed on the liquid surface W is defined as the upper surface side, and the surface opposite to the upper surface side in the penetrating direction of the shaft core 3 is defined as the lower surface side, and the float 1 is defined as the shaft from the upper surface side. It is preferable that the conductive member 4 attached to the lower surface side is adjusted to appear on the projection surface when projected in the penetrating direction of the core 3. By doing so, the container S itself is tilted and the liquid surface W is below the prescribed level, so that even if the float 1 is tilted, the conducting member 4 itself can surely contact the container S.

As mentioned above, the conduction member 4 is eliminated,
FIG. 4 shows an example in which the protruding portions (a pair of folded-back portions 3a) of the shaft core 3 from the float 1 are used as the float side contact portions. Similar to the embodiment shown in FIG. 3, a split pin shape is adopted for the shaft core 3, and a protruding portion is folded back on the lower surface side of the float 1. Since the conductive member 4 is omitted, the conductive member 4 can be manufactured at low cost, but the conductive state is likely to change because the contact resistance changes depending on the bottom state of the float 1 on the container S, and the form shown in FIG. 3 is more reliable. Can be said to be expensive.

Next, the connection between the lead member 2 and the shaft core 3 (split pin) will be described in detail. Examples of the method of connecting the lead member 2 and the shaft core 3 include soldering, welding and pressure bonding. The embodiment shown in FIG. 3 is crimped,
The embodiment shown in FIG. 4 is an example in which soldering is adopted.
Among these methods, crimping using plastic deformation of metal is suitable because it can easily realize strong joining.

FIG. 5 illustrates a specific example of a method for crimping the lead member 2 and the shaft core 3. First, the embodiment shown in FIG. 5A is an example in which the lead member 2 and the shaft core 3 are directly pressure bonded. First, the conductor portion of the lead member 2 is inserted into the through hole 3a of the split pin-shaped auxiliary shaft core 3'in which the through hole 3a is formed near the central portion of the direction changing portion 3b whose direction has been changed (step ). Next, the spare shaft core 3 ′ is caulked, and the lead member 2 and the spare shaft core 3 ′ are crimped to form a bonded body of the shaft core 3 (split pin) and the lead member 2 (step).

In the embodiment shown in FIG. 5B, the through hole is not provided in the direction changing portion 3b whose direction is changed, and the conductor portion of the lead member 2 is covered on the direction changing portion 3b from the radial direction. The caulking forming portion 3c, which is used for caulking after the conductor portion is arranged, is integrally provided to connect the shaft core 3 and the lead member 2.

As shown in FIG. 3 or FIG. 4, such a connecting portion 23 and a soldering portion 27 are embedded in the hole 1a formed in the float 1, and the shaft core 3 is attached to the float 1. It is desirable that it be inserted. This is because, if they are exposed on the upper surface side of the float 1, the flexibility of the lead member 2 may be impaired, and in such a case, the float 1 becomes difficult to move.

As described above, the float switch 10
0, the lead member 2 is guided into the filler cap KP and electrically connected to the sensor control circuit unit as shown in FIG. FIG. 6 shows a vertical cross-sectional view of a filler cap KP, which serves as a circuit case for accommodating the sensor control circuit portion in a space 17 formed therein and serves as a lid member for the oil filler port.

The sensor control circuit unit is the float switch 1
The detection output operation is performed based on the detection result of 00. The sensor control circuit unit is formed by mounting a plurality of electronic components on the printed wiring board 18, and the printed wiring board 18 is built in the filler cap KP. If a dedicated printed wiring board 18 is prepared in advance, electronic components such as a resistor, a diode and a capacitor are mounted on the printed wiring board 18 to form a sensor control circuit portion, and this is simply attached when assembling the filler cap KP. It is possible to assemble the fuel filler cap KP very easily and quickly, which contributes to the reduction of manufacturing cost.

In the present embodiment, the form of attachment of the filler cap KP to the oil tank S is based on the fitting of the screw portions formed on them. Therefore, the rotation axis O of the filler cap KP can be defined by itself. Then, as shown in FIG. 6, the printed wiring board 1
8 is a space 17 formed inside the filler cap KP.
The plate surface is the rotation axis O of the filler cap KP.
Are arranged so as to be substantially perpendicular to. Arranging the printed wiring board 18 in this manner is preferable as a method for firmly fixing the printed wiring board 18 in the space 17. Further, as shown in the present embodiment, when the conductive path is taken out from the side of the filler cap KP, it is advantageous that the peripheral portion of the printed wiring board 18 is closer to the inner wall of the filler cap KP. The placement method is desirable.

Further, the lead member 2 is guided to the inside of the filler cap KP along the rotation axis O of the filler cap KP. By doing so, the lead member 2 is attached almost vertically to the printed wiring board 18, and the lead member 2 can be easily attached to the printed wiring board 18. Further, the space 17 for disposing the printed wiring board 18 to be provided in the filler cap KP is sufficient in a small space. This result can contribute to simplification of the structure of the filler cap from the viewpoint of ensuring a conduction path from the inside of the oil tank S to the outside.

The oil filler cap KP has a male screw portion 16 which is screwed into the female screw portion of the oil filler port provided in the oil tank S to prevent oil from leaking from the oil filler port. When the advancing direction when attaching the filler cap KP to the oil tank S (that is, the traveling direction of the screw) is the front direction of the filler cap KP and the opposite direction is the rear direction, the male thread portion 1
A rear side portion following 6 is enlarged in diameter to form a cap head portion 14. Further, the filler cap KP is arranged on the front side of the cap head 14 so as to allow rotational sliding with respect to the cap main body 25 including the male screw portion 16 and the cap head 14. A ring member 13 is further included, and the cap head 14 is seated at the cap attachment position of the oil tank S via the ring member 13. On the other hand, the ring member 13 has an insulating portion 13b that is in contact with the oil tank S, and a conductive portion 13a that forms a sliding surface with the cap head 14 and that secures the external detection path 12 to the radially outer side of the ring. It is configured to include. Then, the conductive portion 1 of the ring member 13
The conducting portion on the sensor control circuit portion side is in contact with 3a on the sliding surface, and a conductive path from the inside to the outside of the filler cap KP is formed.

With the above arrangement, the cap body 25 including the male screw portion 16 and the cap head 14 is free to rotate with respect to the ring member 13. Therefore, when screwing the filler cap KP into the oil tank S or when removing it, the external detection path 12 is not twisted. As a result, the external detection path 12 can be made of an appropriate wire, and it is not necessary to provide an extra connector or the like, which can contribute to simplification of the structure for forming the conductive path.

Further, when the filler cap KP is attached to the oil tank S, the gauge portion 11 protruding into the oil tank S is formed so as to extend from the front end of the male screw portion 16, and the gauge portion 11 is formed. The lead member 2 is guided to the inside of the filler cap KP from the front end face thereof and is electrically connected to the sensor control circuit section. If such a gauge portion 11 is provided, the filler cap KP also has a level gauge function of visually checking the oil amount. That is, if this is provided in the oil level sensor that can detect only the lower level of the oil, the upper level can be visually confirmed as in the conventional case, so that it is possible to prevent the problem that too much oil is added during refueling. In that case, gauge part 1
It is more preferable to form the knurled surface 11r for indicating the upper level of the amount of oil.

In addition to the above, the filler cap KP
The details of the members constituting the above will be described below. First, the lid 16 is attached to the cap body 25 so as to seal the space 17 in which the printed wiring board 18 is set, and the sealing material 26
Sealed by. As a result, the printed wiring board 18
Can be protected from dirt and shock from the outside.

When the filler cap KP is attached to the oil tank S, the first spring 2 is provided so that a repulsive force acts on the cap body 25 in the direction opposite to the screwing direction.
0 is fitted in a groove formed in a shape along the circumferential direction of the cap body 25. The first spring 20 is a member that conducts with the printed wiring board 18, and rotates and slides with respect to the ring member 13 together with the cap body 25 when tightening or unscrewing the screw. The convex portion 20t formed on the first spring 20 and the printed wiring board 18 are bonded by the wire 24 to form a conduction path connected to the conduction portion 13a of the ring member 13.

Further, in the direction of the axis O, a flat plate-shaped Cu ring 15 is arranged between the male screw portion 16 and the ring member 13. When the filler cap KP is attached to the oil tank S, the cap body 25, the Cu ring 15, and the ring member 13 are sandwiched so that a repulsive force acts in a direction opposite to the screwing direction on the cap body 25. The second spring 21 is arranged in such a manner as to be formed. A ground pin 19 for applying a ground potential level to the printed wiring board 18 is electrically connected to the second spring 21 and the Cu ring 15 in the cap body 25. That is, the ground pin 19 inserted in the printed wiring board 18 → second spring 21 → Cu ring 15
The printed wiring board 18 is supplied with the ground potential by conducting in the order of → ground potential.

A conduction path from the inside of the oil tank S to the outside will be described. A through hole is formed in the end surface of the gauge portion 11, and the lead member 2 is inserted through the through hole.
Is connected to a predetermined position of the printed wiring board 18. The detection output from the printed wiring board 18 is the bonding wire 24 → the convex portion 20t of the first spring 20.
→ first spring 20 → conductive portion 13a of ring member 13
→ The external detection path 12 is propagated in this order.

The ring member 13 has a conductive portion 13a made of a material having good conductivity, and the remaining portion made of an insulating resin material.
1 and the Cu ring 15 are insulated. Similarly, the cap body 25 is also made of an insulating resin material.

As described above, the form of forming the conductive path from the inside to the outside of the filler cap KP has been illustrated, but as shown in FIG. 2, from the rear end of the filler cap KP to the terminals 12a, 12b. May be exposed to secure the conduction path. In this case, since the terminals 12a and 12b follow the rotation of the filler cap KP, it is necessary to provide an appropriate connector or the like.
There is also an advantage that the internal structure of can be simplified. In addition,
One of the terminals 12a and 12b is for applying a ground potential level.

Next, referring to FIG. 7, the oil level sensor 2
The circuit diagram of the engine start control apparatus 300 comprised including 00 is shown. The sensor control circuit unit 200a includes an engine ignition circuit and an oil state detection unit (the float switch 10).
0), which is provided on the detection path 36, and the float switch is switched from one of a predetermined open state and a short circuit state to the other so that the operation of the engine ignition circuit is changed from the normal state to the normal state. It is configured as a start control unit that switches to a difficult start state in which the engine can be started after many engine start trials.

According to the starting control device 300 as described above, when the engine oil is abnormal (in this embodiment, it means running out of oil), the float switch 10 is used.
This is detected by 0, and in response to this, the sensor control circuit unit 200a switches the operation of the engine ignition circuit from the normal state to the difficult start state in which the engine can be started after a number of engine start trials greater than the normal state have been passed. . That is, when an abnormality occurs in the engine oil, the number of engine start trials becomes larger than usual, that is, the engine start is deteriorated, so that the engine user can be surely prompted to change the oil. Moreover, in this case, the engine does not become unusable but becomes hard to start, and the engine can be used for the time being by conducting several trials. Therefore, it is possible to eliminate the inconvenience that the engine suddenly becomes unusable due to an oil abnormality. Further, since the sensor control circuit unit 200a for realizing the above function is directly provided on the detection path 36 that connects the engine ignition circuit and the float switch 100, erroneous detection is unlikely to occur and reliability is high.

The basic part of the ignition system is that a secondary coil 32 of the ignition coil 30 is connected to a spark plug 31 for engine ignition, and a high voltage for ignition is applied to the secondary coil 32 due to a change in magnetic field generated in the primary coil 33. It is a general one that is generated and causes the spark plug 31 to fly. In consideration of portable use outdoors such as a lawn mower, a felling machine, or a private power generator, a recoil starter method without a battery is adopted in order to make the whole compact and lightweight. In the ignition circuit in this case, the recoil starter 34 accompanies the primary coil 33 of the ignition coil 30. Recoil starter 34
Is a well-known one, a pulling force of a rotary magnet is manually pulled and forced to rotate, so that a rapid magnetic field change is generated in the primary coil 33 and a high voltage for ignition is generated in the secondary coil 32. It is what makes me.

Both one end (first end) of the primary coil 33 and one end of the secondary coil 32 are grounded. The spark plug 31 is connected to the other end of the secondary coil 32.
On the other hand, the detection path 3 is provided at the other end (second end) of the primary coil 33.
One end of 6 is connected. The detection route 36
Is a path constituted by a sensor control circuit section 200a built in the filler cap KP and a float switch 100.

A stop switch 35, which opens and closes by a key operation or the like, is diverged in the middle of the detection path 36. If the stop switch 35 is open, the second end side of the primary coil 33 is open as long as the float switch 100 is in the open state (that is, there is sufficient oil), and the recoil starter 34 is operated. Almost no primary current flows even when a magnetic field fluctuation is applied.
As a result, a high voltage for ignition is generated in the secondary coil 32, and the spark plug 31 can be made to fly (that is,
The engine can be started). On the other hand, stop switch 3
When 5 is closed, the primary coil 33 is grounded at both ends,
Even if the recoil starter 34 is operated, the high voltage for ignition is not generated in the secondary coil 32, and the engine cannot be started.

Next, the detection path 36 is formed so as to connect the ignition circuit and the float switch 100. As described above, the float switch 100 includes the float 1 with the conducting member 4 arranged on the liquid surface W in the oil tank S.
And the oil tank S has a detection contact which is arranged in a grounded state corresponding to the oil out position. When the oil level falls to the oil out position, the contact member 4 on the float 1 side is detected. The contact with the contact causes a short circuit. In the present embodiment, the oil tank S itself made of a conductive material serves as the detection contact.

Next, on the detection path 36, between the float switch 100 and the second end of the primary coil 33 of the ignition coil 30, a capacitor 38 constituting the sensor control circuit section 200a is provided. Accordingly, the detection path 36 functions as a charging path for charging the capacitor 38 with the primary current flowing through the primary coil 33 of the ignition coil 30 when the recoil starter 34 is pulled while the float switch 100 is in the short-circuited state. This charging is performed by a sink current to the primary coil 33 side.

When the float switch 100 is in the open state, the charging path is opened, so that the charging of the capacitor 38 by the sink current is blocked. As a result, if the recoil starter 34 is pulled, the ignition coil 30 is always allowed to be ignited (normal state) (naturally, the stop switch 35 is kept open). On the other hand, when the oil level decreases and the float switch 100 is short-circuited, the charging path is closed via the float switch 100. When the recoil starter 34 is pulled in this state, the primary coil 3
The primary current flowing in 3 is generated in the form of the above-mentioned sink current,
The capacitor 38 is charged. At this time, the capacitor 3
Since 8 is equivalently short-circuited (that is, substantially the same state as when the stop switch 35 is closed), ignition by the ignition coil 30 is blocked.

The capacitor 38 is the recoil starter 34.
Since the charging is repeated every time when is pulled, the battery is eventually fully charged and equivalently opened, ignition by the ignition coil 30 is allowed, and the engine can be started. That is, when the oil level is lowered and the float switch 100 is short-circuited, the engine cannot be started because the capacitor 38 does not become fully charged until after more engine starting trials than in the normal state. The state (difficulty starting state) is reached, and the engine user can be surely urged to change oil. Further, in this case, the engine does not become impossible to start, and it can be surely started except that a few attempts are made. That is, the inconvenience that the engine suddenly becomes unusable due to an oil abnormality can be eliminated.

If the impedance on the primary coil 33 side is low, the capacitor 38, which is once charged by the above-described pull-in current, starts discharging as the pull-in current is interrupted. Therefore, when this discharge occurs rapidly, there is a possibility that the capacitor 38 will not be fully charged and the engine cannot be started even if the recoil starter 34 is pulled until exhaustion occurs. Therefore, if a diode 37 (rectifying unit) that blocks the above-described discharge is provided between the ignition coil 30 and the capacitor 38, the capacitor 38 can be smoothly led to a fully charged state, and the capacitor 38 can be charged at an appropriate number of times. The engine can be surely started. At this time, the diode 37 has a cathode on the second end side of the primary coil 33 and an anode on the capacitor 38 side.
Connect to one end of.

It is important that the difficult starting state is such that the user recognizes that "the engine is running a little badly" so as not to feel excessive frustration. Specifically, about 3 to 9 times is suitable. The difference between the two times and the normal state in which the engine can be started even once is not clear and is not suitable for reporting an oil abnormality. On the other hand, if it is performed 10 times or more, the start operation such as pulling the recoil starter 34 may be troublesome, and it may be mistaken for a failure.

Therefore, the capacity of the capacitor 38 also needs to be appropriately adjusted according to the number of trials to be set in the difficult starting state before starting, the inductance of the ignition coil 30, and the capacity of the recoil starter 34. For example, in consideration of the inductance level of an ignition coil generally used in a 25 cc four-cycle engine and the capability of a standard recoil starter, in order to start the engine by three trials, a capacitor 38 is used.
It is appropriate to set the capacitance of the above to about 22 μF.

When the engine is stopped, the fully charged capacitor 38 is self-discharged by leaving it for a certain period of time. Therefore, if the engine is started with an oil abnormality and then stopped, if the engine is restarted without oil replacement or replenishment, the capacitor 38 cannot be started until it is fully charged again. It becomes difficult to start. However, if an attempt is made to restart immediately without sufficient time, the capacitor 38 maintains a state close to full charge, so the float switch 10
Despite the fact that 0 is short-circuited, it leads to the contradiction that the engine can be started immediately. Therefore, such a problem can be effectively prevented by providing a discharging unit for discharging the electric charge charged in the capacitor 38 when the engine is stopped.

FIG. 8 shows an example thereof, in which, in addition to the circuit configuration shown in FIG. 7, the discharging section includes a resistor 39 connected in parallel to the capacitor 38. When the engine is stopped, the resistor 39 and the capacitor 38 form a closed circuit, and the resistor 39 serves as a load to consume the electric charge of the capacitor 38 in the form of current, thereby promoting discharge. The resistor 39 does not function as a bypass path at the time of charging the capacitor 38, and also considers the capacity of the capacitor 38 as a discharge path of the capacitor 38 so that discharge can be completed within an appropriate time (for example, within 1 minute). It is necessary to select the resistance value. For example, when the capacitance of the capacitor 38 is 22 μF and the resistor 39 is set to about 1 MΩ, discharging can be performed within 1 minute after the engine is stopped.

Next, the rotating magnet of the recoil starter 34 is directly connected to the engine shaft, and while the engine is operating, the magnetic field fluctuation is continuously given to the primary coil 33. However, in the configuration of FIG. 7 and FIG. 8, unless the float switch 100 is short-circuited, the detection path 36
Since the end of the capacitor is open, the charging path of the capacitor 38 is not secured and it is difficult for the capacitor 38 to be in a fully charged state. In such a state, the float switch 100 is operated during engine operation.
Is short-circuited, the capacitor 38 once again becomes a state in which the charging path is secured, and temporarily becomes incapable of ignition until it becomes fully charged. In this case, if the engine can continue to rotate during the ignition disabled period due to inertia, the capacitor 38 can be fully charged and ignition can be restarted. However, when the engine is heavily loaded, it may be possible to stop the engine. Therefore, it is convenient to provide an engine stop prevention mechanism for preventing such an engine stop when the float switch 100 is short-circuited after the engine is started.

FIG. 9 shows an example thereof. In addition to the circuit configuration shown in FIG. 8, the engine stop prevention mechanism has a capacitor 38 branching from the detection path 36 between the float switch 100 and the capacitor 38. The auxiliary charging path 40 is included. This allows
The charging path of the capacitor 38 is secured even during engine operation. As a result, the magnetic field fluctuation is continuously applied to the primary coil 33 by the rotating magnet of the recoil starter 34, so that the capacitor 38 can shift to the fully charged state immediately after the engine is started, and the float switch can be operated during engine operation. Even when 100 is short-circuited, it is possible to effectively prevent the problem that the engine is stopped.

The auxiliary charging path 40 has one end connected to the connection point between the capacitor 38 and the float switch 100, and the other end installed at the ground having the same potential as one ends of the primary coil 33 and the secondary coil 32. be able to.
The capacitor 38 is charged by drawing electric charge from the ground. In this case, if the resistance of the path is excessively low, it means that the float switch 100 is always short-circuited, and the oil abnormality cannot be detected accurately. Therefore, it is desirable to provide the resistor 41 in the middle of the auxiliary charging path 40. The resistance value of this resistor 41 is
When the engine is stopped, the float switch 100 is open, the engine is operating, and the capacitor 38
It is desirable to make adjustments so that the voltage application level necessary for starting the engine can be secured on the second end side of the primary coil 33 of the ignition coil 30 when is discharged. That is, since the resistor 41 acts as a resistance against the charging current due to the current drawing from the ground, it is possible to apply an appropriate voltage to the second end side of the primary coil 33 of the ignition coil 30 even at the start of charging. As a general specification of an ignition coil using a recoil starter, if the capacitance of the capacitor 38 is set to 22 μF and the resistor 39 is set to about 1 MΩ, the resistance value of the resistor 41 is preferably set to about 1 kΩ. If the resistance value is too small, it becomes difficult to detect the oil abnormality. On the contrary, if the resistance value is too large, the charging of the capacitor 38 is hindered and the effect cannot be sufficiently achieved.

As described above, the present invention is not limited to the embodiments, and it goes without saying that the present invention can be implemented in various modes without departing from the scope of the invention. Further, it is obvious that application of the present invention to liquids other than oil (for example, water, fuel, chemicals, paints, etc.) belongs to the equivalent range. It should be noted that the attached drawings are schematic for understanding.

[Brief description of drawings]

FIG. 1 is an overall view of an oil level sensor of the present invention.

FIG. 2 is a view showing another mode following FIG.

FIG. 3 is an overall view of a float switch that forms an oil state detection unit.

FIG. 4 is a view showing another mode following FIG. 3;

FIG. 5 is a view for explaining a joining mode of a lead member and a shaft core in a float switch.

FIG. 6 is a vertical cross-sectional view of a filler cap (circuit case).

FIG. 7 is a circuit diagram showing an embodiment of an engine start control device including an oil level sensor.

8 is a circuit diagram showing a modified example of the engine start control device of FIG.

9 is a circuit diagram showing another modification of the engine start control device of FIG. 7. FIG.

[Explanation of symbols]

1 float 2 Lead member 11 gauge 12 signal lines 13 Ring member 13a Insulation part of ring member 13b Conductive part of ring member 14 cap head 16 Male thread 18 Printed wiring board 25 cap body 36 detection route 100 float switch (oil condition detector) 200 oil level sensor 200a Sensor control circuit unit KP filler cap (circuit case) W liquid level S oil tank O rotation axis

Claims (6)

[Claims] 1. An oil state detection section that switches between an open state and a short-circuit state according to a change in the state of engine oil, and a sensor control circuit section that performs detection output operation based on the detection result of the oil state detection section. And a circuit case for accommodating the sensor control circuit section in a form of being isolated from the engine oil, wherein the sensor control circuit section is built in a filler cap that covers the engine oil filler port, An oil level sensor, wherein the cap and the circuit case are combined. 2. A portion of the filler cap that should be located in the oil tank, the oil condition detector being connected to the filler cap, and the oil condition detector being electrically connected to the sensor control circuit unit. While one end of a lead member for connecting the lead member is connected, the other end of the lead member is attached to a float that is a member that constitutes the oil state detection unit and floats above the liquid surface of oil. The oil level sensor according to claim 1, wherein 3. The oil level sensor according to claim 1, wherein the lead member is guided into the inside of the fuel filler cap in a form along a rotation axis of the fuel filler cap. 4. The fuel filler cap has a male screw portion that is screwed into a female screw portion of a fuel filler port provided in an oil tank to prevent oil from leaking from the fuel filler cap. When the advancing direction when attaching to the oil tank is the front direction of the filler cap, and the opposite direction is the rear direction, the rear side portion following the male screw portion is expanded in diameter to form the cap head, and The cap head further includes a ring member arranged on the front side of the cap head so as to allow rotational sliding with respect to the cap body including the screw portion and the cap head, and the cap head is the ring member. While being seated at the cap attachment position of the oil tank, the ring member forms a sliding surface between the insulating portion in contact with the oil tank and the cap head, and also to the outside of the ring. And a conductive portion for ensuring a conductive path, and the conductive portion of the ring member is in contact with the conductive portion on the sensor control circuit portion side on the sliding surface, and the inside of the filler cap is formed. The conductive path from the outside to the outside is formed.
4. The oil level sensor according to any one of items 1 to 3. 5. When the filler cap is attached to an oil tank, a gauge portion protruding into the oil tank is formed so as to extend from a front end of the male screw portion,
The oil level sensor according to claim 4, wherein the lead member is guided from the front end surface of the gauge portion into the inside of the filler cap and is electrically connected to the sensor control circuit portion. 6. The sensor control circuit section is provided on a detection path that connects an engine ignition circuit and the oil state detection section, and the oil state detection section is preset to the open state and the short circuit state. By switching from one to the other, the operation of the engine ignition circuit is configured as a start control unit that switches from a normal state to a difficult start state in which the engine can be started after more engine start trials than the normal state. The oil level sensor according to any one of claims 1 to 5.