JPH0218428B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field to which the Invention Pertains] The present invention relates to a non-contact ignition device for an internal combustion engine, and particularly to one that prevents ignition energy from decreasing even in a high speed range.

Conventionally, ignition systems for internal combustion engines such as automobiles have been equipped with mechanical contacts (contact points) in the distributor that open and close in synchronization with the rotation of the engine, and this controls the primary current of the ignition coil. Those with a secondary coil that generates high-voltage pulses were widely used. However,
In recent years, non-contact ignition devices that use non-contact electromagnetic pick-up coils instead of contact points have come into use in order to prevent pollution and reduce fuel consumption. Requirements are becoming increasingly sophisticated.

[Prior art and its problems]

As an example of this type of conventional contactless ignition device, FIG. 1 shows a circuit layout of a closed angle control method using a forward bias method. This device utilizes the fact that the magnitude of the output signal of the electromagnetic pickup coil 11 (see Figure 2) is proportional to the engine speed.
The output signal of the coil 11 is stored in the capacitor 13 via the diode 12, and forward bias is supplied to the control circuit 15 by the transistor 14, and the control circuit 15 changes the conduction period of the output transistor 16 accordingly. Ignition coil 17
The current flowing through the primary coil is controlled and a high voltage pulse is generated in the secondary coil. This igniter is
Although it is mainly used for four-wheeled vehicles, if it is applied to two-wheeled vehicles, it has the following drawbacks. That is, (1) As shown in FIG. 3, the output waveform of the timing signal generated by the two-wheeled vehicle electromagnetic pickup coil 11 has an interference voltage, which causes the conduction period of the output transistor 16 to correspond to the engine rotation angle. (hereinafter referred to as the closing angle) and the closing angle
If the angle is over 160° (44% duty), false ignition is likely to occur.

(2) The output voltage of the electromagnetic pickup coil 11 is
Variations may occur due to mechanical installation errors,
Since the maximum output voltage reaches three times the minimum output voltage, variations in the closing angle characteristics inevitably increase.

As a conventional technique for eliminating such drawbacks,
synchronized with engine rotation, at least the first and second
an electromagnetic pickup coil that generates a timing signal consisting of a period of time, an output transistor that responds to the timing signal and supplies current to the ignition coil during a first period; a capacitor circuit that discharges during a period of A non-contact ignition device equipped with this is shown in Japanese Patent Application Laid-Open No. 57-99268.

The operation of this conventional device will be described later in connection with the description of the embodiments of the present invention, but if the circuit elements are determined so that the closing angle control can be performed smoothly at high rotational speeds, then due to constraints such as circuit constants, In this case, the closing angle becomes large, which has the disadvantage of increasing power loss.

[Purpose of the invention]

An object of the present invention is to provide a non-contact type ignition device that can take advantage of the advantages of the conventional device in the high rotational speed region and further reduce power loss in the low rotational speed region.

[Key points of the invention]

The present invention detects a predetermined engine speed, and when the engine speed is below the predetermined speed, the output transistor is controlled on and off without any special processing on the input signal, and when the engine speed is above the predetermined speed, the closing angle control function of the conventional device is performed. It is characterized by the fact that it can be utilized as is.

[Embodiments of the invention]

FIG. 4 is a circuit diagram of an embodiment of the present invention, and the circuit composed of circuit elements with two-digit numbers is the circuit disclosed in the aforementioned Japanese Patent Application Laid-Open No. 57-99268,
A circuit (circuit surrounded by a dotted line) composed of circuit elements with digit numbers is a circuit added according to the present invention.

This ignition system includes an electromagnetic pickup coil circuit 41 that generates a timing signal synchronized with the rotation of the engine, and an ignition coil 4 that generates high-voltage pulses.
2. It consists of an output transistor circuit 43 that supplies primary current to the ignition coil 42, a closing angle control capacitor circuit 45 that controls the closing angle of the output transistor circuit 43, and a power source 46. The electromagnetic pickup coil circuit 41 has a series circuit of a resistor 51 and a Zener diode 52, and a constant voltage generated across the Zener diode 52 is connected to a control circuit 44.
supply to. Also, this Zener diode 52
A resistor 53 and a diode 54 with the polarity shown are connected across the
One end of an electromagnetic pickup coil 55 is connected to the connection point between the resistor 53 and the diode 54. The other end of the electromagnetic pickup coil 55 is connected to the base of a transistor 58 of the control circuit 44 via a resistor 56. This electromagnetic pickup coil 55 generates an output voltage having a waveform increasing from approximately zero in the positive direction in the first period _t1 , as shown in FIG. 5A, in synchronization with the rotation of the engine, and In period _t2 , the voltage increases from a negative voltage toward zero, and an output voltage having a waveform different from that in period _t1 is generated.

The control circuit 44 includes a plurality of switching transistors 58, 59, 60, 61, 62 and a comparator 77.
have. Now, if a timing signal is supplied to the transistor 58 and it exceeds a predetermined level in the first period _t1 , the transistor 58 becomes conductive, as shown in FIG. 5B, and therefore the respective transistors 59 is non-conductive, transistor 60 is conductive, and transistor 62 is non-conductive, so Darlington-connected transistors 84 and 85 in output transistor circuit 43 are conductive, and primary current is supplied to ignition coil 42. However, when the timing signal reaches the second period _t2 , transistor 58 becomes non-conductive, as shown in FIG. 5B, transistor 59 becomes conductive, and transistor 60 becomes non-conductive. this period
At t ₂ , transistor 62 becomes conductive or non-conductive depending on the state of previous transistor 61 . The control circuit 44 further includes switching transistors 66, 76, and 74.
Transistors 66 and 76 are configured such that transistor 60 is non-conducting (i.e., during the second period of the timing signal).
_t2 ), transistor 66 controls the start of discharging of capacitor circuit 45, and transistor 76, together with transistor 74, controls comparator 77.
Set the constants of the reference voltage circuit. Comparator 77
compares the reference voltage with the voltage of the capacitor circuit 45, and outputs a high level voltage when a predetermined condition is satisfied as described later, and feeds this back to the capacitor circuit 45 via the resistor 78. to the initial state, and resistor 7
The conduction of the transistor 61 is controlled through the transistor 9.
The capacitor circuit 45 includes a resistor 65 and a diode 6.
7, and an initialization circuit including a discharging resistor 68, a resistor 70, and a transistor 71. During the first period _t1 of the timing signal, the transistor 66 is non-conductive, so a charging current is supplied to the capacitor 69 via the resistor 65 and the diode 67, and the capacitor 69
As shown in FIG. C, the Zener diode 52 gradually charges the battery to a constant voltage. However, the second
During period _t2 , the transistor 66 becomes conductive,
Since the diode 67 becomes reverse biased and becomes non-conductive, the capacitor 69 starts discharging through the resistor 68. At this time, in the control circuit 44, the transistor 76 becomes conductive, and the transistor 76 becomes conductive.
4 becomes non-conductive, and a voltage obtained by dividing the above-mentioned constant voltage by resistors 72 and 73 is inputted to a comparator 77 as a reference voltage. The comparator 77 compares this reference voltage, V _r , and the terminal voltage V _c of the capacitor 69 (see FIG. 5C), and sets the low level voltage L when V _c ≧V _r , and sets the low level voltage L when V _c ≧V r. When _r , a high level voltage H is output (see FIG. 5D). Therefore, when the terminal voltage V _c of the capacitor 69 decreases to V _c < V _r , the comparator 77 transfers the high level voltage H to the resistor 78 ,
Since the voltage is supplied to the transistors 71 and 61 through the respective transistors 79, the transistors 71 and 61 become conductive. Therefore, the capacitor 69 is rapidly discharged through the resistor 70 and the transistor 71, and returns to its initial state. Furthermore, when the transistor 61 becomes conductive, the transistor 62 becomes non-conductive and the output transistors 85 and 84 become conductive, so that the primary current I _c flows through the ignition coil 42 during the second period t ₂ as well, causing ignition. Energy compensation is performed. Fifth
Figures E, F, and G are transistors 61 and 6, respectively.
2 is a waveform diagram showing the relationship between the operation of No. 2 and the primary current I _c. FIG.

Next, the operation of the non-contact ignition device configured as described above will be further explained with reference to the waveform diagrams of FIGS. 5A to 5G and 6A to C.

The electromagnetic pickup coil 55 generates a timing signal in synchronization with the rotation of the engine, as shown in FIG. 5A, and during the first period _t1 , the transistor 58 is conductive (FIG. 5B). Therefore, transistors 60, 85, and 84 become conductive, but transistors 59 and 62 become non-conductive. When the transistors 85 and 84 become conductive, a primary current I _c (FIG. 5G) flows through the ignition coil 42, and ignition energy is stored. At this time, transistor 6
6 becomes non-conductive, so the capacitor 69 is replaced by the resistor 6.
5. Charging begins with the current supplied through diode 67, and this charging continues throughout the period _t1 (FIG. 5C). Further, the transistor 76 is non-conductive,
Since transistor 74 is conductive, the reference voltage of comparator 77 becomes a very low voltage, and comparator 77
supplies a low level L output voltage (FIG. 5D) to transistors 61 and 71, thus transistor 6
1 and 71 are in a non-conducting state during period _t1 .

Then, during the second period _t2 of the timing signal, a negative voltage is applied to transistor 58 and transistor 58 is non-conducting, so transistors 60, 85, 84 are non-conducting and transistor 5 is non-conducting.
9 and 62 are electrically connected. Then, the primary current of the ignition coil 42 is suddenly cut off, and the energy stored in the ignition coil 42 during period _t1 is released, so a high voltage, for example 30 kV, is induced on the secondary side.
Spark discharge occurs at the spark plug. Also, during this period
At t ₂ , the transistors 66 and 76 become conductive, so the capacitor 69 starts discharging via the resistor 68, and as the transistor 74 becomes non-conductive, the reference voltage V _r is supplied to the comparator 77. . The capacitor 69 discharges slowly, but when its terminal voltage V _c becomes lower than the reference voltage V _r (V _c
<V _r ), the comparator 77 generates a high-level H output voltage (D in FIG. 5) and feeds it back to the transistor 71, so that the transistor 71 becomes conductive.
The capacitor 69 is rapidly discharged and returns to its initial state, as shown in FIG. 5C. Since the high level H output voltage of the comparator 77 is also supplied to the transistor 61, the transistor 61 becomes conductive, the transistor 62 becomes non-conductive (FIG. 5E), and the output transistors 85 and 84 become conductive (Fig. 5E). (see Figure 5F),
A primary current I _c (FIG. 5G) begins to flow through the ignition coil 42. In this way, one of the ignition coils 42
It is possible to advance the timing at which the next current I _c starts conducting and to increase the closing angle.

Therefore, as the engine speed increases, as shown in FIG. 6A, although the output waveform of the electromagnetic pickup coil 55 does not substantially change, the period t ₁ ,
Since t ₂ becomes shorter, the charging voltage of capacitor 69 decreases, as shown by the dotted line in FIG. 6B. Therefore, the terminal voltage of the capacitor 69 gradually decreases during period t ₂ due to discharge, but the voltage reaches the reference voltage V _r more quickly during high-speed rotation than during low-speed rotation.
, and as shown by the dotted line in Figure 6C, the primary current
The closing angle of I _c increases during high-speed rotation, which can compensate for the decrease in ignition energy.

By the way, the circuit explained so far uses capacitor 6.
9 is a circuit based on charging and discharging, and when trying to smoothly control the closing angle in the high rotation range,
The charging/discharging time constant of the capacitor must be made small, and this has the disadvantage that the closing angle becomes too large in the low rotation range, causing unnecessary current to continue flowing through the output transistor for a long time, increasing loss. .

Therefore, in the present invention, a comparator 100 is newly provided, and in this comparator 100, the resistors 101 and 102 are
(Setting value corresponding to the specified rotation speed N)
is compared with the potential of the capacitor 69 as an electrical quantity related to the number of rotations, and if the number of rotations exceeds N, the transistor 104 is turned off and the conventional closing angle control circuit using the comparator 77 functions. Do it like this.

When the rotation speed is below N, the comparator 100 and transistor 104 are turned on, so
The transistor 61 is turned OFF regardless of the presence or absence of the output of the comparator 77, and the transistor 62 is turned OFF and OFF in the opposite relationship to the ON and OFF states of the transistor 60.
It becomes ON. In other words, the output transistors 85 and 84 are controlled only by inverting or non-inverting the input signal. Transistor 105, resistor 10
6 is a comparator 100 when the transistor 60 is OFF.
This was added to prevent the control from working.

Thus, the operating waveforms when the rotational speed is low are as shown in FIG. In FIG. 7, A is the voltage of the pickup coil 55, and B is the voltage of the transistor 58.
, C is the potential of the capacitor 69, D is the operating state of the transistor 104, and E is the potential of the transistor 62.
, F is the primary current of the ignition coil 42, and G is the secondary voltage waveform of the ignition coil 42.

〔Effect of the invention〕

As described above, according to the present invention, by simply adding a simple circuit to the conventional circuit, it is possible to perform closing angle control with little loss over a wide range of rotational speeds.

[Brief explanation of drawings]

Figure 1 is a circuit diagram of a conventional non-contact ignition system, Figures 2 and 3 are waveform diagrams of the timing signal from the electromagnetic pickup coil in Figure 1, and Figure 4 is a diagram of the timing signal from the electromagnetic pickup coil in Figure 1.
The figure is a circuit diagram showing one embodiment of the non-contact ignition device according to the present invention, Figure 5 is a waveform diagram of each part thereof, Figure 6 is a waveform diagram for explaining closing angle control during high speed rotation, The figure is a waveform chart for explaining the closing angle control according to the present invention during low speed rotation. 41... Electromagnetic pickup coil circuit, 42... Ignition coil, 43... Output transistor circuit, 44...
Closed angle control circuit, 45... Capacitor circuit, 46...
Power supply, 100... Comparator, 104... Transistor.

Claims (1)

[Scope of Claims] 1. An electromagnetic pickup coil that is synchronized with the rotation of the engine and generates a timing signal having at least a first and a second period; an output transistor that supplies a current; a capacitor circuit that charges during the first period of the timing signal and discharges during the second period; In the contactless ignition device, the contactless ignition device includes a first control circuit that outputs a signal to set the capacitor circuit in an initial state and controls an operation of the output transistor.
The output transistor is made conductive during the period of
A second transistor that makes the output transistor non-conductive during the period of
A second control circuit detects a predetermined rotational speed of the engine, and when the rotational speed is below the specified rotational speed, the output of the second control circuit is
A non-contact ignition device further includes a rotation speed detection switching circuit that supplies the output of the first control circuit to the output transistor when the rotation speed is above the specified rotation speed. 2. In the device according to claim 1,
A contactless ignition device characterized in that a terminal voltage of a capacitor circuit is used as a rotation speed detection input of a rotation speed detection switching circuit.