JPH0351905B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an overspeed prevention device for an internal combustion engine.

[Prior Art] Outboard motors, etc. are equipped with an ignition device that operates based on an ignition timing signal with a frequency proportional to the engine rotation speed, and also shift the output relative to the engine rotation to forward, neutral, or reverse rotation. An internal combustion engine is used which is coupled to a shift device which allows the state to be changed.

Conventionally, in the internal combustion engines used in the above-mentioned outboard motors, etc., there is protection from damage due to overspeeding of the engine under no-load conditions during neutral shifting, and unintentional shifting to forward/reverse state due to high vibration of the engine. In order to prevent this, the upper limit of the rotational speed under the shift state is regulated. Furthermore, in order to prevent the rotation from increasing due to the small propeller load and to prevent the outboard motor body from jumping up during a reverse shift, the upper limit of the rotation speed under the shift state is regulated.

Here, in the case of conventional internal combustion engines,
As in Japanese Patent No. 156023, the upper limit of the rotational speed is regulated by regulating the throttle valve opening range of the carburetor.

In addition, for other conventional internal combustion engines,
As in Japanese Patent No. 52-168127, the upper limit of the rotational speed is regulated by adjusting the ignition timing.

[Problems to be Solved by the Invention] However, the prior art has the following problems.

No consideration is given to preventing overspeeding within one internal combustion engine, regardless of whether the shift state is set to normal rotation, neutral rotation, or reverse rotation. Furthermore, no consideration is given to realizing overspeed prevention operation regardless of the driver's intention, no matter which of the above-mentioned shift states is set.

If the overspeed prevention rotation speed is set by restricting the throttle valve opening, it is impossible to set the throttle valve to the optimal opening for starting the engine under neutral shift conditions, which impairs starting performance. cause deterioration.

When setting the overspeed prevention rotation speed and adjusting the ignition timing, it is difficult to set the medium to low overspeed prevention rotation speed required during neutral and reverse rotation. In other words, in order to keep the internal combustion engine's rotation speed to a medium to low speed, it is necessary to significantly retard the ignition timing, but in that case, combustion in the engine continues until the exhaust port is opened, causing inconveniences such as after-fire. It is an invitation.

The present invention realizes overspeed prevention operation that is optimal for each shift state, whether forward, neutral, or reverse, without impairing engine operability and regardless of the driver's intention. The purpose is to

[Means for Solving the Problems] The present invention includes an ignition device that ignites a spark plug according to the rotation of an engine, and a shift device that can switch the engine output between forward rotation, neutral rotation, and reverse rotation. In an overspeed prevention device for an internal combustion engine, the overspeed prevention rotation speed at which the spark plug should misfire is determined in advance according to each shift state of the shift device, and the overspeed prevention rotation speed at which the spark plug is to be misfired is determined in advance according to each shift state of the shift device, and the overspeed prevention rotation speed at which the spark plug is to be misfired is determined in advance. The engine is equipped with an overspeed prevention circuit that automatically sets an overspeed prevention rotation speed corresponding to the state, and controls the ignition device so that the spark plug misfires when the overspeed prevention rotation speed is higher than the automatically set overspeed prevention rotation speed. It is something.

[Function] According to the present invention, there are the following effects.

In one internal combustion engine, the optimal overspeed prevention rotation speed is set in advance for each of the forward rotation, neutral, and reverse shift states. Therefore, overspeed prevention operation can be achieved in any of the shift states.

Automatic control is performed in conjunction with the switching operation of the shift device to each shift state so as to realize an optimal over-speed prevention operation for the shift state. Therefore, it is possible to realize overspeed prevention operation that is optimal for each shift state regardless of the driver's intention.

Since the overspeed prevention rotation speed is set using misfire control, it is possible to control forward, neutral, and reverse rotation without impairing engine operability, compared to methods that restrict throttle valve opening or adjust ignition timing. Over-rotation prevention operation can be realized for each of them at the optimum rotation speed.

[Embodiment] FIG. 1 is a side view showing an outboard motor to which the present invention is applied, and FIG. 2 is an electric circuit diagram showing a first embodiment of the present invention.

The outboard motor 10 can be attached to a stern plate 12 of a hull via a bracket 11, and has an internal combustion engine 14 mounted on the upper part of its casing 13. The output of the internal combustion engine 14 can be transmitted to a propeller 18 via a drive shaft 15, a shift device 16, and a propeller shaft 17. The shift device 16 is operated by operating a shift lever (not shown) or the like, and is capable of switching the output relative to engine rotation to any one of forward, neutral, and reverse shift states and transmitting the output to the propeller 18.

The internal combustion engine 14 is also equipped with a CDI ignition device 19 shown in FIG. CDI ignition system 19
The voltage generated by the magneto power generation coil 20 is rectified by the diode 21 and then connected to the ignition capacitor 22.
After charging starts, the gate of the SCR 24 becomes conductive due to the signal current of the ignition timing signal generated by the pulser coil 23, and at the same time, the electric charge stored in the ignition capacitor 22 is suddenly released via the primary side of the ignition coil 25. By doing so, a high voltage is generated on the secondary side of the ignition coil 25, and a spark can be generated at the ignition plug 26. Here, the frequency of the ignition timing signal generated by the pulsar coil 23 is proportional to the rotational speed of the internal combustion engine 14.

Therefore, in this first embodiment, the ignition timing signal generated by the pulsar coil 23 is transmitted to the SCR 24.
A diode 2 is included in the transmission circuit 27 that enables transmission to the
8 and a resistor 29 are interposed therebetween, and an over-rotation prevention circuit 30 is provided. Overspeed prevention circuit 30
is an F/V converter 31 that converts the frequency of the ignition timing signal generated in the pulsar coil 23 into voltage.
have. The output voltage of the F/V converter 31 is
NPN through the forward rotation Zener diode 32, the neutral contact 33, the neutral Zener diode 34, and the reverse rotation contact 35 and the reverse Zener diode 36, which are arranged in parallel with each other.
It is possible to apply it to the base of the type transistor 37. The collector of the transistor 37 is connected to the transmission circuit 2
The emitter of the transistor 37 is connected between the resistor 29 of No. 7 and the SCR 24, and the emitter of the transistor 37 is grounded.

Here, the forward rotation Zener diode 32 is connected to the F/V corresponding to an engine rotation speed of 6000 RPM, for example.
It is possible to conduct a voltage higher than the output voltage of the converter 31. Therefore, the rotational speed of the engine is
When the speed exceeds 6000 RPM, the forward rotation Zener diode 32 is always conductive, and therefore the transistor 37 is also conductive, and the pulsar coil 2
3 to the SCR24 is short-circuited and grounded,
It causes the engine to misfire and prevents the engine from over-speeding above 6000 RPM. In addition, the neutral contact 33
is closed when the shift state by the shift device is set to the neutral position, and the neutral Zener diode 34 can conduct more than the output voltage of the F/V converter 31 corresponding to an engine speed of 3500 RPM, for example. It is said that Therefore, when the rotational speed of the engine exceeds the above-mentioned 3500 RPM while the shift state of the shift device is set to the neutral position, the neutral Zener diode 34 becomes conductive, and therefore the transistor 37 also becomes conductive. This causes the signal current flowing from the pulsar coil 23 to the SCR 24 to be short-circuited and grounded, causing the engine to misfire and preventing the engine from over-rotating above 3500 RPM.

Further, the reversal contact 35 is closed when the shift state of the shift device is set to the reverse position, and the reversal Zener diode 36 is closed, for example.
It is possible to conduct a voltage higher than the output voltage of the F/V converter 31 corresponding to an engine speed of 4000 RPM. Therefore, when the rotational speed of the engine exceeds the above-mentioned 4000 RPM while the shift state of the shift device is set to the reverse position, the reverse Zener diode 36 becomes conductive, and therefore the transistor 37 also becomes conductive. conduction, which causes pulser coil 2
3 to the SCR24 is short-circuited and grounded,
It causes the engine to misfire and prevents the engine from over-speeding above 4000 RPM.

That is, according to the first embodiment, by setting the limit frequency of the overspeed prevention circuit 30 according to the shift state, it is possible to regulate the upper limit rotation speed in each shift state. Therefore, the throttle valve opening of the carburetor can be operated at the optimum opening for each operating state of the engine, and there is no problem such as deterioration of startability due to prevention of overspeeding of the engine.

FIG. 3 is an electrical circuit diagram showing a second embodiment of the present invention. It is assumed that the second embodiment also uses a CDI ignition device 19 similar to that of the first embodiment. However, in this second embodiment,
The ignition timing signal generated by the pulsar coil 23
An over-rotation prevention circuit 40 is connected to a transmission circuit 27 that enables transmission to the SCR 24. The over-rotation prevention circuit 40 includes a first capacitor charging/discharging circuit 41 , a comparison constant voltage circuit 41 , a comparison circuit 43 , a second capacitor charging/discharging circuit 44 , a constant voltage or higher conduction element 45 , and a transistor 46 .

Here, the first capacitor charging/discharging circuit 41 includes a first capacitor (capacitance C ₁ ) 50, a neutral/reverse contact 51, and a second capacitor (capacitance C ₂ ) 52, which are arranged in parallel with the resistor 49. and a neutral contact 53 and a third capacitor (capacitance C ₃ ) 5
It is equipped with 4. As shown in FIG. 4, the neutral/reverse contact 51 and the neutral contact 53 can be opened and closed by a changeover switch 56 operated by a cam 55 that rotates in conjunction with a shift operation. The operating element 57 of the changeover switch 56 is moved up and down by the cam 55 under the bias of the spring 58, and under each shift state, the operating contact 5 of the operating element 57
9 to the above neutral/reverse contact 51 or neutral contact 53
It is possible to connect and separate. That is, when the shift state of the shift device is set to the forward rotation position, the operating contact 59 does not contact either the neutral/reverse contact 51 or the neutral contact 53, as shown in FIG. 1 Capacitor charge/discharge circuit 4
Set the capacitor capacity of C1 to _C1 , which has a small time constant. Further, when the shift state by the shift device is set to the neutral position, as shown in FIG. 5B, the operating contact 59 contacts both the neutral/reverse contact 51 and the neutral contact 53, and the first capacitor The capacitor capacity of the discharge circuit 41 has a large time constant.
Set to C ₁ + C ₂ + C ₃ . In addition, when the shift state by the shift device is set to the reverse position,
As shown in FIG. 5C, the operating contact 59 is brought into contact only with the neutral/reverse contact 51, and the capacitor capacity of the first capacitor charging/discharging circuit 41 is set to C ₁ +C ₂ . Note that the time constant of the first capacitor charging/discharging circuit 41 may be determined by adjusting the resistance value of the resistor 49 instead of adjusting the capacitor capacity.

The first capacitor charge/discharge circuit 41 discharges when the ignition timing signal pulse _V1 is input from the pulser coil 23, and then starts charging under a predetermined time constant condition set by the shift state. The comparison constant voltage circuit 42 always outputs the reference voltage _V3 . The comparison circuit 43 compares the capacitor voltage V ₂ of the first capacitor charging/discharging circuit 41 and the reference voltage V ₃ of the comparison constant voltage circuit 42, outputs a constant voltage V 5 when V ₂ ≧V ₃ , and outputs a constant voltage V ₅ when V 2 ≧V ₃ . The output voltage is zero at <V ₃ . The second capacitor charging/discharging circuit 44 charges while the output voltage of the comparator circuit 43 is zero, and discharges when the comparator circuit 43 outputs a constant voltage _V5 . The constant voltage or higher conduction element 45 is composed of a Zener diode, and is connected to the capacitor voltage of the second capacitor charging/discharging circuit 44.
Conducts when V ₆ is above a predetermined voltage. The constant voltage or higher conduction element 45 is connected to the base of the transistor 46. The collector of the transistor 46 is connected between the resistor 29 of the transfer circuit 27 and the SCR 24, and the emitter of the transistor 46 is grounded. Therefore, when the conduction element 45 is in a conductive state at a constant voltage or higher, the transistor 46 is also conductive, thereby causing the pulser coil 23 to
The signal current directed to the SCR 24 shorts to ground, allowing the engine to misfire.

Next, the operation of the second embodiment will be explained with reference to FIGS. 6 to 8. In addition, in the display of each signal voltage V ₂ , V ₅ , V ₆ in Figures 6 to 8, the solid line shows an example when the shift state is in the neutral position, and the one-dot chain line shows an example when the shift state is in the normal rotation position. An example is shown below.

When the engine speed is low, for example around 3000 RPM, where overspeed prevention is not required,
As shown in FIG. 6, the pulse interval T ₁ of the ignition timing signal pulse V ₁ is relatively long. Therefore, when the shift state is in the neutral position, the time constant of the first capacitor charging/discharging circuit 41 is larger than that in the normal rotation position. The capacitor voltage V ₂ changes relatively slowly and requires a relatively long time to reach the reference voltage V ₃ of the comparison constant voltage circuit 42 . However, the first capacitor charging/discharging circuit 4
The capacitor voltage V ₂ of the second capacitor charging/discharging circuit 44 reaches the reference voltage V ₃ in any case, and the comparator circuit 43 outputs a constant voltage V ₅ , so the capacitor voltage V ₆ of the second capacitor charging/discharging circuit 44 is conductive at a constant voltage or higher. The conduction voltage of the element 45 is not reached and the engine does not misfire.

For example, when the engine rotational speed requires overspeed prevention when the shift state is in the neutral position.
In the case of a medium speed state exceeding 3500 RPM, as shown in FIG. 7, the pulse interval T ₂ of the ignition timing signal pulse V ₁ is smaller than the pulse interval T ₁ .
Therefore, when the shift state is in the neutral position, the capacitor voltage V ₂ of the first capacitor charging/discharging circuit 41 is discharged before being charged to the reference voltage V ₃ , and V ₂ <V ₃ is always maintained. Comparison circuit 43
The output voltage remains zero, and the capacitor voltage _V6 of the second capacitor charge/discharge circuit 44 continues to rise without discharging, exceeding the constant voltage or the conduction voltage of the conduction element 45, the transistor 46 also becomes conductive, and the pulsar coil It becomes possible to short-circuit and ground the signal current flowing from SCR 23 to SCR 24, causing the engine to misfire. Note that under this medium speed condition, when the shift condition is in the forward rotation position, the capacitor voltage V ₂ of the first capacitor charging/discharging circuit 41 exceeds the reference voltage V ₃ , so that it is possible to prevent the engine from misfiring. do not have.

When the engine rotational speed reaches a high speed state exceeding 6000 RPM, which requires overspeed prevention even when the shift state is in the normal rotation position or the neutral position, the ignition is activated as shown in Figure 8. The pulse interval T ₃ of the timing signal pulse V ₁ is even smaller than the pulse interval T ₂ . In this case, the first capacitor charging/discharging circuit 41 is not only in the neutral position but also in the normal rotation position.
The capacitor voltage V ₂ is discharged before it reaches the reference voltage V ₃ , and V ₂ <V ₃ always holds, so the output voltage of the comparator circuit 43 is always zero, and the capacitor voltage V of the second capacitor charging/discharging circuit 44 ₆ exceeds the constant voltage or the conduction voltage of the conduction element 45 without discharging, and the transistor 46 also becomes conductive, making it possible to short-circuit and ground the signal current flowing from the pulsar coil 23 to the SCR 24, causing the engine to misfire.

In addition, in the second embodiment, when the shift state is set to the reverse rotation position, the time constant of the first capacitor charging/discharging circuit 41 is different when the shift state is set to the forward rotation position and when the shift state is set to the neutral position. Therefore, over-rotation is prevented at a speed approximately intermediate between the over-rotation prevention speed at the neutral position and the over-rotation prevention speed at the normal rotation position.

In each of the above embodiments, the case where the collectors of the transistors 37 and 46 are connected to the transmission circuit 27 has been described.
The collectors 7 and 46 may be connected, for example, between the ignition capacitor 22 of the primary circuit of the ignition device 19 and the primary side of the ignition coil 25, as shown by the two-dot chain line in FIG. In this case, for example, in a state where the Zener diodes 32, 34, and 36 are conductive due to overspeed of the engine as in the first embodiment, even if the gate of the SCR 24 is turned on by the ignition timing signal of the pulsar coil 23. conduction,
Even if the charge of the ignition capacitor 22 is released, the charge is short-circuited to ground via the transistor 37.
No voltage is applied to the primary side of the ignition coil 25.

Further, in each of the embodiments described above, when the engine overspeeds, the ignition timing signal generated by the pulsar coil 23 is short-circuited to ground, so that the gate of the SCR 24 is not brought into conduction. However, the present invention
For example, the portion indicated by 38 in FIG. 2 becomes conductive under normal rotation of the engine, and is rendered non-conductive by an ignition timing signal of a predetermined limit frequency or higher, such as that determined by the Zener diodes 32, 34, and 36 in the first embodiment. A switch (such as a transistor) may be interposed. In this case, under overspeeding of the engine, the voltage generated in the power generation coil 20 does not charge the ignition capacitor 22, and even if the gate of the SCR 24 is made conductive by the ignition timing signal of the pulsar coil 23, To misfire an engine without releasing an ignition charge to the primary side of an ignition coil 25.

Further, in the present invention, for example, the portion indicated by 39 in FIG. 2 is electrically conductive under normal rotation of the engine.
A switch (transistor, etc.) which becomes non-conductive in response to an ignition timing signal having a frequency higher than a predetermined limit frequency such as that defined by No. 4, 36 may be interposed. In this case,
Even if the gate of the SCR 24 is made conductive by the ignition timing signal of the pulsar coil 23 under overspeed of the engine, the ignition charge of the ignition capacitor 22 is not applied to the primary side of the ignition coil 25 and the engine stops. misfire.

In addition, although each of the above embodiments describes a case where the present invention is applied to an internal combustion engine equipped with a CDI ignition device, the present invention also applies to an ignition device that operates based on an ignition timing signal with a frequency proportional to the engine rotation speed. It is also applicable to internal combustion engines equipped with other ignition devices.

[Effects of the Invention] As described above, according to the present invention, in any of the shift states of forward rotation, neutral rotation, and reverse rotation, each shift can be performed without impairing the operability of the engine and regardless of the driver's intention. It is possible to achieve overspeed prevention operation that is optimal for the situation.

[Brief explanation of drawings]

Fig. 1 is a side view showing an outboard motor to which the present invention is applied, Fig. 2 is an electric circuit diagram showing a first embodiment of the invention, and Fig. 3 is an electric circuit showing a second embodiment of the invention. 4 is a side view showing the changeover switch used in the second embodiment, FIGS. 5A, B, and C are operating state diagrams showing different operating states of the changeover switch, and FIG.
The figure is an explanatory diagram showing the signal processing state of the overspeed prevention circuit at low speed in the second embodiment, and FIG.
FIG. 8 is an explanatory diagram showing the signal processing state of the overspeed prevention circuit at medium speed in the embodiment, and FIG. 8 is an explanatory diagram showing the signal processing state of the overspeed prevention circuit at high speed in the second embodiment. 14... Internal combustion engine, 19... CDI ignition system, 2
3...Pulsa coil, 24...SCR, 30,4
0...Overspeed prevention circuit.

Claims (1)

[Claims] 1. In an overspeed prevention device for an internal combustion engine, which has an ignition device that ignites a spark plug in accordance with engine rotation, and a shift device that can switch the engine output between forward rotation, neutral rotation, or reverse rotation, the shift device The overspeed prevention rotation speed at which the spark plug should misfire is determined in advance according to each shift state, and the overspeed prevention rotation speed corresponding to the shift state is automatically set in conjunction with the switching operation of the shift device to each shift state. An over-speed prevention device for an internal combustion engine, comprising an over-speed prevention circuit that controls an ignition device to cause a spark plug to misfire when the speed exceeds an automatically set over-speed prevention speed.