JPH0574713B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a circuit for controlling the operation of an electric preheating device for an internal combustion engine such as a diesel engine, which is equipped with an electric preheating device for igniting fuel.

[Prior Art] In an internal combustion engine, such as a diesel engine, which is equipped with a glow plug as an electric preheating device for fuel ignition, the fuel is connected to the engine cylinder chamber to cause explosive combustion of the fuel. A sub-combustion chamber is provided for preheating and pre-combustion, and the glow plug placed in this sub-combustion chamber is made red hot just before the engine is started, and fuel is injected into this glow plug to ignite it, and once the glow plug is heated, it is heated. After the engine starts, it is configured to continue explosive combustion using the compression heat and combustion heat of the fuel mixture.

Recently, so-called glow plug afterglow has become commonplace, in which the glow plug continues to be energized for a predetermined period of time even after the engine has started. The effect of performing afterglow is that it prevents engine stalling caused by unstable combustion immediately after startup, and the generation of white smoke in the exhaust gas.
The start of such afterglow should be performed based on the engine start signal, but conventional methods for detecting engine start have been to switch the output terminal of the voltage regulator from the low voltage supply side to the high voltage supply side. This method was based on a method of electrically detecting that the switch has been switched to the side, or of capturing the switch of the engine key switch from the ST contact to the ON contact as an electrical signal (Japanese Patent Laid-Open No. 56-126674).
Publication No.).

[Problems to be Solved by the Invention] As the engine start detection method described above, in the former method of detecting the switching of the output terminal of the voltage regulator, the driver senses the complete engine explosion and turns the engine key switch. When switching from the ST contact to the ON contact, the switching contact of the output terminal of the voltage regulator should immediately be reversed from the low voltage supply side to the high voltage supply side by the action of the electric circuit, but currently this is not the case. There is a tendency for a time delay to occur in the reversal, and since afterglow does not occur during this delay time, there is a considerable possibility that the engine will stall.

Furthermore, the latter method of electrically detecting that the engine key switch has been switched from the ST contact to the ON contact (Japanese Patent Laid-Open No. 126674/1983)
Once the regulator output terminal was switched from the low voltage supply side to the high voltage supply side, the engine start was considered complete and the afterglow was forcibly stopped. There was nothing that contributed to stabilizing combustion after replacement, and it was completely inadequate.

When the engine key switch of the present invention is returned from the ST contact to the ON contact, even if there is a delay in switching the regulator output terminal to the low voltage supply side or the high voltage supply side, it will not switch back to the high voltage supply side. Afterglow is performed even after the engine has started to stabilize the combustion and eliminate the possibility of engine stalling.In addition, if the engine stalls after it has been started, this can be reliably detected and the glow plugs can be removed. An object of the present invention is to provide a starting assist system for an internal combustion engine that can interrupt afterglow and has an extremely simple configuration.

[Means for Solving the Problems] In order to achieve the above object, the internal combustion engine starting assist system of the present invention includes an energizing (ON) contact for an electrical preheating device for sticky ignition of an internal combustion engine; ,
For energizing the starter motor of the internal combustion engine (ST)
an engine key switch having a contact; and an engine key switch from the ST contact to continue energizing the electrical preheating device for a certain period of time even after the engine is started.
For a generator, which is equipped with an energization extension timer that starts when the ON contact is switched, and an output terminal for switching and supplying high voltage or low voltage current to the excitation coil of the generator driven by the internal combustion engine. It is reset by input from the voltage regulator and the ST contact,
The engine stop detection circuit generates an output signal for stopping the energization extension timer when the regulator output terminal once switches to the high voltage supply side and then switches again to the low voltage supply side. Adopted.

[Operations and Effects of the Invention] The starting assist system for an internal combustion engine of the present invention configured as described above switches the engine key switch from the ON contact, which is the contact for preheating the electrical preheating device (for example, a glow plug), to the ST contact. By switching, the engine stop detection circuit is reset. As the engine starts by switching to the ST contact, the supply voltage switching contact at the output terminal of the voltage regulator is reversed from the low voltage side to the high voltage side, and the ST contact is switched to the ON contact. The timer for extending the power supply is started. Even after the voltage regulator output terminal switches to the high voltage side, current continues to flow to further stabilize combustion, but if the engine stalls after starting, this output terminal contact switches back to the low voltage supply side. Based on this inverted signal from the high-voltage side to the low-voltage side contact, the electric circuit operates to stop the energization extension timer, cut off the power supply to the electrical preheating device, and prevent it from overheating. Ru.

The electric circuit that operates to stop the energization extension timer stops its operation by the output from the ST contact when the engine key switch is switched from the ON contact to the ST contact to restart the engine. Be prepared for the opportunity to stop the timer for extending the energization.

Although the internal combustion engine starting assist system according to the present invention has a simple configuration, it can prevent engine stalling, which tends to occur immediately after starting the engine, by continuing to energize the glow plug even after the regulator output terminal is switched to the high voltage side. On the other hand, if the regulator output terminal switches once to the high voltage side and then switches again to the low voltage supply side, this can be detected, and the electric preheating device of the fuel can be activated in the event of an engine stall. If it continues to operate (for example, afterglow operation of a glow plug in a diesel engine), it is reliably stopped and the preheating device is prevented from becoming brittle due to overheating.

[Example] The structure of the present invention will be specifically described below based on the example shown in the attached drawings. FIG. 1 is a system block diagram illustrating a first embodiment in which the starting assist system of the present invention is applied to a diesel engine for automobiles, in which A is a self-control glow plug; are shown. 1 is an engine key switch for starting the engine,
OFF contact and ON contact for energizing glow plug A to heat glow plug A to the temperature required for fuel ignition prior to operating the engine's starter motor (not shown), and a starter for starting the engine. For energizing the motor
Equipped with ST contact. 2 is the output of a voltage regulator for a generator, which switches and supplies high-voltage or low-voltage current to the excitation coil of a generator (not shown) driven by an automobile engine (not shown) in accordance with its output voltage. terminal,
3 is an engine stall detection circuit, and 4 is a pre-glow timer, which is started when the engine key switch 1 is switched to the ON contact and energizes the glow plug A for a set time to heat it to a predetermined temperature. 5 is an afterglow timer, which is started when engine key switch 1 is switched from the ST contact to the ON contact, and is an optional afterglow timer that starts when the engine key switch 1 is switched from the ST contact to the ON contact and continues until the deflagration of the fuel mixture in the engine cylinder is stabilized a while after the engine is started. It plays the role of continuously energizing glow plug A only for a period of time. 6
7 is a water temperature sensor for engine cooling water; 7 is a vehicle speed sensor; 8 is a vehicle speed determination circuit for detecting that the vehicle speed is below a set level; and 9 is a circuit for preventing excessive voltage from being applied to glow plug A. An overvoltage detection circuit, 10 a lamp timer for checking the preheating state of the glow plug A, and a lamp timer for keeping the preheating lamp 14 lit only for a set time after the start of energization to the glow plug A; 11 and 12, respectively, the glow plug A; The contacts of the glow relay and its excitation coil are used to energize for a set time, and 13 is an on-board battery power source.

FIG. 2 is a circuit diagram of the engine stall detection circuit incorporated in the system of the present invention, where 40 is an operational amplifier, and the numerical symbols in the diagram correspond to those in FIG. 1.

FIG. 3 is an operation time chart of the system of the first embodiment.

Fig. 4 is a block diagram of a system similar to Fig. 1 for a second embodiment in which a normal rapid preheating glow plug A' is used in place of the self-regulating glow plug A used in the first embodiment. Figure 5 is an operating time chart of this circuit, where 15 and 17 are the contacts of the first glow relay for preheating (pre-glow) glow plug A' by energizing it for a set time, respectively. These are the excitation coils, and 16 and 18 are the contacts of the second glow relay and their excitation coils, respectively, to keep the glow plug A' energized for a set time even after the engine has started (afterglow). . Further, 30 is a chopping timer for intermittently energizing the glow plug A' in the latter half of energization to suppress the excessive temperature rise of the glow plug A', and 31 is a chopping timer for energizing the second glow relay. Glow relay contact 1
This is a heat retention timer for continuously energizing the engine 6 after the engine key switch 1 is switched to the ON contact until the engine is started. Other symbols in the figure are the same as those in the first embodiment.

Next, the operation of the glow plug energization control circuit shown in the first embodiment will be explained with reference to FIGS. 1 and 2 and FIG. 3 as an operation time chart. First, by switching the engine key switch 1 from the OFF contact to the ON contact, a pre-heating pre-glow timer 4 is started to energize the glow plug A for a set time and heat it to the required temperature, and the glow plug A
When the contact 11 of the glow relay for energizing is closed and the glow plug A reaches a certain temperature, the pre-heating pre-glow timer 4 is stopped and the contact 11 of the relay is opened {FIG. 3, E and G}. After confirming that the preheating lamp 14 for monitoring the preheating state is turned off, the engine key switch 1 is switched from the ON contact to the ST contact for starting the starter motor, and the engine stall detection circuit 3 is activated based on the input from this ST contact. is started and the contact 11 of the glow relay is kept closed. Further, the voltage V1 at the negative input terminal a of the operational amplifier 40 increases due to the input from the ST contact. The output terminal c of the operational amplifier 40 serves as an output terminal for transmitting an engine stall signal of the engine stall detection circuit 3, and the capacitor C1 is a positive input terminal b to which an electric voltage is applied.
When the voltage Vc is Vc<V1, the engine stall detection circuit 3
is configured to output a Lo signal and a Hi signal when Vc>V1, and when the output terminal c is sending out a Lo signal, the afterglow timer 5 for extending the energization to the glow plug A is activated. operation is maintained;
Once the output terminal c is switched to a Hi signal, the operation of the afterglow timer 5 is stopped.

After confirming that the engine has started due to the action of the starter motor, return the engine key switch 1 from the ST contact to the ON contact, and the afterglow timer 5 will start, and the voltage regulator for the generator of a normal diesel engine will start. As a characteristic of the generator, when the generator starts, its output terminal should immediately switch from the low voltage supply side to the high voltage supply side, but after some time delay (t), it switches to the high voltage supply side. There is a tendency to change {3rd
Figure b}. Therefore, during this time t, V1 drops from the Zener voltage to the value obtained by dividing Vz1 by R5 and R6, but since Vc = 0, the output of the engine stall detection circuit 3 continues to send out the Lo signal. Figure 3 D, C}. If engine stall does not occur immediately after time t has elapsed, regulator output terminal 2
is switched to the high voltage supply side contact, so Vc as the charging voltage of capacitor C1 rises to the voltage divided by R2 and R3, and V1 also becomes almost Zener voltage due to the action of diodes D2 and R4. {Figure 3 D}. And Vc holds the relationship of Vc<V1 due to voltage drop due to voltage division,
The engine stall detection circuit 3 continues to output the Lo signal. However, in the circuit shown in Figure 2, R4≪R
5, set to the condition of R6.

If an engine stall occurs during the operation period of the afterglow timer 5, the regulator output terminal 2 is inverted to the low voltage supply side, so the operational amplifier 4
The negative input terminal voltage V1 of 0 drops the Zener voltage to a voltage divided by R5 and R6. On the other hand, the positive input terminal Vc of the operational amplifier 40, which serves as the charging voltage of the capacitor C1, causes the capacitor C1 to start discharging due to the reversal of the regulator output terminal 2 from the high voltage supply side to the low voltage supply side. Since Vc is maintained at a sufficiently high voltage, the relationship Vc > V1 holds and the output signal of the engine stall detection circuit 3 changes from Lo to
Inverted to Hi {Fig. 3 D, C}. At this time, Vc is maintained at a high voltage due to the positive feedback effect of the diode D3, and the engine stall detection circuit 3 continues to send out a Hi signal to stop the operation of the afterglow timer 5, so that the operation of this timer is stopped. When the contact 11 of the glow relay is opened, the current to the glow plug A is cut off, thereby preventing the glow plug A from being thermally damaged due to the current being maintained even after the engine stalls.

After the engine stalls, when the engine key switch is switched from the ON contact to the ST contact again in order to restart, V1 rises to the Zener voltage as described above, but Vc is equal to the voltage drop of the transistor in the operational amplifier. and diode D due to positive feedback.
Since the voltage is reduced by the forward voltage drop of 3,
Since the relationship of Vc<V1 is established, the output of the engine stall detection circuit 3 is reversed to Lo, and returns to the starting state when switching from the original ON contact to the ST contact (see Figure 3 A, C, and F). .

Next, the operation of the above system will be explained based on the block diagram shown in FIG. By switching the engine key switch 1 from the OFF contact to the ON contact in order to start the engine, an energization signal is output from the pre-glow timer 4 to the glow plug A, which passes through the OR gate 20 to the AND gate 21.
is input. The vehicle speed determination circuit 8 is one of the two inputs to the NOR gate 22 which is another input source of the AND gate 21, and the overvoltage detection circuit 9 to the glow plug A is the other input source. If there is no signal input above the set level, a pass judgment output is sent out.
is activated, the contact 11 of the glow relay is closed, and preheating of the glow plug A is started.

After confirming that the preheating lamp 14 is off, switch the engine key switch 1 from the ON contact to the ST contact.
When the direct glow relay contact 11 is closed by the ST signal, the output from the ST contact is also applied to the engine stall detection circuit 3, and the engine stall detection circuit 3 operates as described above and switches from the ST contact to the ON contact. After that, the time count of afterglow timer 5 starts, and as long as the engine stall does not occur, the Lo signal is continued to be input to afterglow timer 5.
Since the afterglow timer 5 does not disturb the time counting, the output signal is sent out without interruption from the afterglow timer 5, and this output signal is inputted to the AND gate 21 via the OR gate 20, and is then input to the NOR gate 2 as described above.
As long as the input condition of 2 is satisfied, AND gate 2
The afterglow of glow plug A is continued by the output from 1. If the engine stalls after the engine starts and the regulator output terminal 2 once becomes Hi, the engine stall detection circuit 3 sends a Hi signal to the afterglow timer 5 to stop the engine, as described above, so the afterglow timer 5 is stopped. When the output signal from timer 5 stops, AND gate 21
loses at least one of its inputs, and the signal transmission for forced closing of the contact 11 of the glow relay is stopped. Additionally, if the vehicle speed increases above the set level or the voltage supplied to the glow plug A increases excessively during the activation period of the afterglow timer 5,
Since the output from the vehicle speed determination circuit 8 or the overvoltage detection circuit 9 is stopped, one input to the AND gate 21 is lost, so power supply to the glow plug A is stopped even if no engine stall occurs. The afterglow timer 5 is also stopped based on this detection signal when the engine coolant temperature sensor 6 detects a water temperature higher than a set level. The water temperature sensor 6 also sends a similar stop signal to the lamp timer 10 for turning off the preheating lamp 14 after a set time, so that the preheating lamp 14 is turned on only for a minimum period of time.

To summarize the operational characteristics of the starting assist system for an internal combustion engine according to the present invention described in the above embodiment, the engine stall detection circuit 3 connects the regulator output terminal 2 to the engine from the high voltage supply side contact which means that the engine is running. Operational amplifier 4 indicates that the contact has switched to the low voltage supply side, which means that the
0 is detected (of glow plug A, which is started in conjunction with the operation of switching engine key switch 1 from the ST contact to the ON contact).
It sends out a signal to stop the afterglow timer 5, and serves to prevent the glow plug A from being overheated and burnt out. When the engine is restarted, the operation of the engine stall detection circuit 3 is automatically stopped as the engine key switch 1 is switched from the ON contact to the ST contact.

Next, regarding the operation of a starting assist system for a diesel engine as a second embodiment of the present invention using a normal rapid heating type glow plug A', FIG. 4 is an operational block diagram and FIG. 5 is a time chart. This will be explained with reference to.

By switching the engine key switch 1 from the OFF contact to the ON contact, the pre-glow timer 4 for preheating the glow plug A' and the glow plug
Once the temperature of glow plug A has risen to the required temperature, a start signal is input to the chopping timer 30, which intermittently energizes the plug to prevent the plug from overheating. The contact 15 of the first glow relay is closed. Since the outputs from both timers 4 and 30 pass through the OR gate 32, even if the operation of either one is stopped by operating a switch or the like, the power supply to the glow plug A' is not stopped. When the heat retention timer 31 is incorporated into the circuit, this timer is started at the same time as the ON contact is switched.

Next, turn engine key switch 1 from the ON contact.
By switching to the ST contact, the engine stall detection circuit 3 is started by inputting the switching signal of the engine key switch 1 from the ST contact to the engine stall detection circuit 3, and the ST signal causes the contact of the second glow relay to be started. 16 is started.
Afterglow timer 5 is started when the ST contact is switched to the ON contact, but this operation is
There is no difference compared to that of the embodiment except that the pre-glow timer 4 in the former is replaced with a heat retention timer 31, so a description thereof will be omitted.

Although the above embodiments are all explained in the case where the internal combustion engine is a diesel engine, the starting assist system of the present invention can also be applied to other types of internal combustion engines that require an electric fuel preheating device similar to a glow plug. It can be utilized.

[Brief explanation of the drawing]

Fig. 1 is a system block diagram of a first embodiment in which the starting assist system of the present invention is applied to an automotive diesel engine, Fig. 2 is a circuit diagram of an engine stall detection circuit incorporated in the system of the present invention, and Fig. 3 4 is a system block diagram of the second embodiment. FIG. 5 is a system operation time chart of the second embodiment. In the figure, A, A'... Glow plug, 1... Engine key switch, 2... Regulator output terminal, 3... Engine stall detection circuit, 4... Pre-glow timer, 5... After-glow timer, 11, 1
5, 16...Glow relay contact, 12, 17,
18... Glow relay coil.

Claims (1)

[Scope of Claims] 1. An engine key switch equipped with an (ON) contact for energizing an electrical preheating device for igniting fuel of an internal combustion engine, and a (ST) contact for energizing a starter motor of the internal combustion engine. and from the ST contact in order to continue energizing the electrical preheating device for a certain period of time even after the engine is started.
For a generator, which is equipped with an energization extension timer that starts when the ON contact is switched, and an output terminal for switching and supplying high voltage or low voltage current to the excitation coil of the generator driven by the internal combustion engine. It is reset by input from the voltage regulator and the ST contact,
An internal combustion engine comprising an engine stop detection circuit that generates an output signal for stopping the energization extension timer when the regulator output terminal once switches to the high voltage supply side and then switches again to the low voltage supply side. start-up assistance system.