JPS6021503Y2 - Intake preheating device for diesel engines - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an intake air preheating device for a diesel engine that preheats intake air of the engine in order to facilitate starting of the diesel engine in cold weather.

Conventionally, in this type of device, a heating wire that heats and ignites the fuel is attached to a fuel outflow pipe that penetrates the wall of the intake pipe, and is used not only during engine startup but also before engine startup, that is, to drive the starter motor. Before starting, an electric current is applied to this heating wire to heat it to a temperature sufficient to ignite the fuel, and the fuel is supplied to the fuel outflow pipe before or at the same time as driving the starter motor.The heated heating wire causes the fuel to flow out. The fuel flowing out of the pipes was ignited, and the heat generated by the combustion of this fuel was used to preheat the intake air, and after the engine started, the intake air preheating device was stopped immediately to avoid depleting the oxygen in the intake air. .

In this device, it is further necessary to drive the starter motor after a predetermined period of time has elapsed after the start of intake air preheating.

For example, Japanese Utility Model Application Publication No. 49-83433 discloses that a bimetal switch is used to control the preheating time of a preheating plug.

However, bimetal switches have large manufacturing variations and cannot be adequately controlled.

Therefore, there is a shift in the starting timing of the starter motor, which poses a problem in ensuring reliable starting.

To solve this problem, the inventor considered using a charging/discharging circuit using a capacitor.

The use of this charging/discharging circuit has the effect of making control more accurate, but since the discharging circuit for discharging the energy charged in the capacitor releases the charging energy of the capacitor as heat, a circuit that can withstand heat is required. There was a problem that the circuit became large.

Furthermore, it was necessary to prevent the heating wire from suddenly cooling down.

The purpose of the present invention is to solve the above problems.

In other words, it is necessary to make the discharge circuit of the charge/discharge circuit smaller and further to prevent the heating wire from cooling down suddenly.

The feature of this invention is that the timer switch that controls the time from supplying current to the heating wire to driving the starter motor is composed of a charging/discharging circuit and a semiconductor switch that operates when the output voltage of the charging/discharging circuit reaches a predetermined value. The semiconductor switch excites the excitation coil of the starter switch, and the charging/discharging circuit is composed of a charging circuit that supplies current to the capacitor and a discharging circuit that discharges the energy charged in the capacitor. This energy is discharged through the heating wire.

As a result, the drive time of the starter motor can be accurately controlled, and the discharge energy of the capacitor is dissipated as heat through the heating wire, so there is an advantage that the discharge circuit can be made small.

Furthermore, this discharge has the effect of setting the temperature drop characteristics of the heating wire.

The present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention.

In the same figure, 1 is a heating wire that penetrates the wall of the intake pipe (not shown) and is placed inside the intake pipe, and 2 is used to start the engine after the heating wire 1 reaches a temperature at which the fuel can be ignited. This is the electromagnetic coil of the electromagnetic valve that opens the valve in conjunction with driving the starter motor to allow fuel to flow out from the fuel outflow pipe.

One end of the heating wire 1 is grounded, and the other end thereof is connected to a starter contact 4 of a key switch 5, which is a changeover switch having a general load contact 3 and a starter contact 4, which are first and second fixed contacts.

A movable contact 6 of the key switch 5 is connected to a positive terminal of a power source 7.

Between the starter contact 4 and one end of the excitation coil 10 of the electromagnetic switch 9, which is a starter switch that controls the energization of the starter motor 8 used to start the engine, is connected as part of a timer for standby power supply to the starter motor. A normally open electromagnetic switch 11 is provided.

In addition, in case intake air preheating is not required, the electromagnetic switch 11
A manual switch 12 is provided in parallel with.

One end of the electromagnetic coil 2 is grounded, and the other end is an electromagnetic switch 11
It is connected to the fixed contact 13 of the excitation coil side contact of the electromagnetic switch 9.

The other end of the excitation coil 10 of the electromagnetic switch 9 is grounded.

The excitation coil 14 of the starter motor 8 is coupled to the positive terminal of the power supply 7 via the normally open contact 15 of the drive electromagnetic switch 9 .

Reference numeral 16 denotes a lamp 1 that starts a timed operation when the heating wire 1 starts to be energized to indicate that the heating wire 1 is being energized.
7 is turned on and when a predetermined time period has elapsed, the lamp 17 is turned off and the starter motor 8 is connected between the excitation coil 10 of the electromagnetic switch 9 and the starter contact 4 of the key switch 5. This is a timer circuit that controls the driving of 8.

The timer circuit 16 includes a capacitor 20 connected in parallel to both ends of the heating wire 1 via a diode 18 and a resistor 19. The timer circuit 16 has a charging time constant of the capacitor 20, which is charged from a power source 7 via a diode 18 and a resistor 19. has been established.

A series circuit of a diode 21 and a resistor 22 is connected in parallel to both ends of the series circuit of the diode 18 and the resistor 19, and the diode 21, the resistor 22, and the heating wire 1 constitute a discharge circuit for the capacitor 20.

One end of the capacitor 20 on the resistor 19 side is connected to the base of a transistor 24 via a constant voltage diode 23, and the collector of the transistor 24 is connected to the starter contact 4 of the key switch 5 via a resistor 25.

The emitter of the transistor 24 is connected to the base of a transistor 26 whose emitter is connected to the other end of the capacitor 20, and between the starter contact 4 of the key switch 5 and the transistor 2.
The excitation coil 2 of the electromagnetic switch 11 is connected between the collector of 6 and the collector of 6.
Connect 7.

One end of the series circuit of resistors 28 and 29 is connected to the starter contact 4 of the key switch 5, and the other end is connected to the base of a transistor 30 connected to the other end of the capacitor 20.

A diode 31 is connected between the connection point between the resistors 28 and 29 and the collector of the transistor 26.

The collector of transistor 30Φ is connected to the base of transistor 33 via resistor 32.

The emitter of the transistor 33 is connected to the starter contact 4 of the key switch 5, and the collector is connected to the lamp 17 with one end grounded.
Connect to the other end.

In the above device, when the starter contact 4 of the key switch 5 is closed during low-temperature starting of the diesel engine, electricity starts flowing through the heating wire 1 and, at the same time, charging of the capacitor 20 through the diode 18 and the resistor 19 starts.

Similarly, a base current flows through the transistor 30 through the resistors 28 and 29.

As a result, the transistor 30 becomes conductive and the resistor 32 becomes conductive.
A base current flows to the transistor 33 through the transistor 33, and the transistor 33 becomes conductive, and a current flows to the lamp 17, thereby lighting the lamp.

The terminal voltage of the capacitor 20 is the resistor 19 and the capacitor 20.
When the voltage across the capacitor 20 exceeds the Zener voltage of the voltage regulator diode 23, a base current flows to the transistor 24 through the voltage regulator diode 23.

As a result, the transistors 24 and 26 become conductive, current flows through the excitation coil 27 of the electromagnetic switch 11, this electromagnetic switch 11 is closed, and current flows through the excitation coil 10 of the electromagnetic switch 9, starting to energize the starter motor. The starter motor starts.

When the electromagnetic switch 11 is closed, current flows through the electromagnetic coil of the electromagnetic valve and the valve opens, allowing fuel to flow out.

At the same time, the base current of the transistor 30 flowing through the resistors 28 and 29 is short-circuited from the connection point between the resistors 28 and 29 through the diode 31 and the transistor 26.

Therefore, transistors 30 and 33 become non-conductive and lamp 17 goes out.

In the above embodiment, the temperature rise characteristics of the heating wire 1 with respect to time are known, and the time required for the terminal voltage of the capacitor 20 to exceed the Zener voltage of the constant voltage diode 23 and the temperature at which the heating wire 1 can ignite the fuel are determined. By setting the charging time constant of the capacitor 20 so that the time required to reach the desired value is approximately equal, the desired operation can be performed.

The setting of the charging time constant of the capacitor 20 can be appropriately adjusted by appropriately selecting the resistance value of the resistor 19 and the capacitance of the capacitor 20.

Next, in the above device, when the starter contact 4 of the key switch 5 is opened, the power supply to the heating wire and the timer circuit is stopped, the electromagnetic switch 11 is opened, and the starter motor is stopped.
Lamp 17 is turned off.

At the same time, the charges accumulated in the capacitor 20 are discharged through the diode 21, the resistor 22, and the heating wire 1.

The time constant of this discharging circuit can be set independently of the charging time constant of the capacitor 20, and the discharging time constant of the capacitor 20 can be set appropriately according to the temperature drop characteristics of the heating wire with respect to time after energization is stopped. If this setting is made, the time limit of the timer can be shortened when the starter contact 4 of the key switch 5 is closed again. This will eliminate the problem of having to wait for a long time instead of working extra hours.

The starter motor is stopped until the starter contact 4 of the key switch 5 is closed and the timer operation is completed, but normally the starter motor starts immediately when the starter contact 4 is closed. It is supposed to be.

Therefore, here, a lamp is lit and displayed while the starter motor is in a standby state by a timer.

This lamp not only lets you know that the heating wire is being preheated, but also prevents you from mistaking the fact that the starter motor does not start because it is preheating as a failure of the starter motor.

When the engine is restarted after it has been warmed up or when the engine is started at room temperature, the manual switch 12 is closed because intake air preheating is not necessary.

This allows the starter motor to start starting immediately without waiting.

Furthermore, in this case, if a water temperature switch that operates by detecting the engine cooling water temperature is used instead of the manual switch 12,
It is possible to automatically select whether to wait or not depending on the environmental temperature and engine warm-up state.

FIG. 2 shows another embodiment of the present invention, which differs from FIG. 1 in that an automatic return type push button switch 34 is provided instead of the key switch 5 as the power switch for the intake air preheating device, and a manual switch 12 is used instead of the key switch 5. It has been abolished.

Push button switch 34 connects movable contact 35 to the positive terminal of power supply 7.

A fixed contact 13 of the power switch 11 is connected to a starter contact 4 of the key switch 5.

In the embodiment shown in FIG. 2, the intake air preheating device is activated and automatically drives the starter motor by arbitrarily closing or closing the push button switch 34 depending on the state of the engine.

This allows the device to be activated only when humans judge and feel it is necessary.

In the above embodiment, the push button switch 34 is directly connected to the power supply, but this push button switch 34 is connected to the general load contact 3 of the key switch 5, and the combination of the key switch 5 and the push button switch 34 is used to control the intake air preheating device. A power switch may also be configured.

In the above embodiment, the timer is a combination of electromagnetic switches and semiconductor switches, but the timer may be made entirely of semiconductor switches in place of semiconductors for the electromagnetic switches.

Further, a general timer such as a bimetal type or a mechanical type may be used.

In the above embodiment, the starter/motor start waiting lamp 17
Although this is assumed to be lit, it is not necessary to do so.

Further, instead of the lamp, a sounding device such as a buzzer may be used as the display means.

In the above embodiment, the fuel supply means for the intake air preheating device is of the electromagnetic valve type using the electromagnetic coil 2, but a thermal expansion valve type may also be used.

As described above, since the present invention uses a charging/discharging circuit and a semiconductor switch that detects its output, it is possible to accurately control the time from when the heating wire is driven until when the starter motor is driven. Furthermore, there is little variation among each product.

In addition, in the above embodiment, since the charging circuit and the discharging circuit are made independent, the charging time and the discharging time can be set separately, and the temperature drop characteristics can be adjusted by discharging the charging energy of the capacitor in the charging/discharging circuit via the heating wire. It can be set to prevent a sudden drop in temperature of the heating wire.

[Brief explanation of the drawing]

FIG. 1 is a connection diagram showing one embodiment of the present invention, and FIG. 2 is a connection diagram of another embodiment. 1... Heating wire, 5... Key switch (
Power switch), 7...Power, 8...
Starter motor, 9... Electromagnetic switch (starter switch), 10... Excitation coil, 16...
...Timer circuit (timer).

Claims (1)

[Scope of utility model registration request] A fuel supply means for supplying fuel into the intake pipe at the time of starting, a heating wire connected to a DC power supply via a power switch, and an excitation coil of a starter switch to which the voltage of the DC power supply is applied via a timer switch. The timer switch is set to the time required for intake air preheating, and the power switch is operated to supply current to the heating wire, and the timer starts operating, delayed by the timer switch setting time. in which the starter motor is operated; the timer switch includes a charging/discharging circuit that performs charging or discharging in response to the operation of the power switch;
The charging/discharging circuit includes a semiconductor switch circuit that causes an exciting current to flow through the exciting coil of the starter switch when the output voltage of the charging/discharging circuit exceeds a predetermined value, and the charging/discharging circuit responds to the closing operation of the power switch by capacitors. 1. An intake air preheating device for a diesel engine, comprising: a charging circuit that supplies current to the power switch; and a discharging circuit that discharges the charging energy of the capacitor via the heating wire in response to the opening operation of the power switch.