JPS5982563A - Discontinuity sensing device for intake heater - Google Patents

Abstract

PURPOSE:To secure possibility to start an engine even though the heater is in discontinuity partially, by equipping the intake heater with a discontinuity sensing device, sensing the current flowing through this heater and by making a corrective control of the impress voltage using this output of sensing. CONSTITUTION:High voltage VH of a battery 17 is directly impressed on an intake heater 10 by energizing a relay x1, low voltage VL is impressed through a dropping resistance D/R by energizing a relay x2. The sensing resistance S/R connected in series with the intake heater 10 is a heater temp. sensing element to sense the surface temp. of the heater 10. A discontinuity sensing circuit 30 generates a control signal consisting of '1' and '0' in accordance with the magnitude of the current flowing through said sensing resistance S/R. When a discontinuity has occurred in the heater, the discont. sensing circuit 30 emits a control signal '0' to release the heater from impression of high voltage VH, and the low voltage VL is impressed on the heater regularly.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a disconnection detection device for an intake heater that heats the intake air flowing through the intake system of an internal combustion engine such as a diesel engine to improve the startability of the engine. The applied voltage is applied to the parallel-connected intake heaters, the current flowing through them is detected, and the applied voltage is corrected and controlled using the detected output, so even if one of the intake heaters is disconnected, the engine will not run. The present invention relates to a disconnection detection device for an intake heater that is capable of ensuring startup and issuing a false notification of disconnection.

[Technical background of the invention and its problems]

In general, internal combustion engines, especially diesel engines, are used in environments where the temperature of the air inhaled is relatively low (cold regions, cold times, etc.)
In this case, spontaneous ignition cannot be induced only by compressing the intake air within the cylinder/cylinder, making it almost impossible to start the engine smoothly.

In order to deal with this situation, as shown in Fig. 1, fuel is supplied to the intake system 2 of the engine 1 and a part of the intake air (white arrow in the figure) is combusted, and this combustion heat is used to A starting assist device called an intake heater 3 is installed, which improves the starting performance of the engine 1 by heating the flowing intake air.

Conventionally, as this type of intake heater, one shown in FIG. 2 is known. A heating resistor 4 made of Nichrono wire is inserted into a metal shaft 5 made of steel, and the metal shaft 5 is further inserted into a metal shaft 5 made of steel.
Magne/Rum powder 6 is compactly packed inside. Then, a voltage from a power source 7 is applied to the heating resistor 4 to make the metal shaft 5 red hot, and fuel is supplied thereto to vaporize and ignite and burn it.

However, the Innotheque heater 3 has the following problems.

(1) Since metal is used for the heater body (metal shaft 5) and the fuel is directly combusted, the voltage value (current value) for heating is limited due to oxidation and melting of the metal. .

(2) Alternatively, the heating resistor 4 indirectly heats the metal shaft 5 through the magnet/ram powder 6 filled in it to increase the heat capacity of the heater 3 to maintain combustion. Unfortunately, the heating time and the time required to reach the ignition temperature were prolonged, making it impossible to shorten the starting time. By the way, for large diesel engines, the time was longer than 12 seconds.

(3) Due to the current restriction, the overall temperature cannot be made high enough, and the heat capacity of the metal shaft 5 itself is small, so even if ignition occurs, if you try to drive the starter motor to start the engine, Due to the accompanying increase in intake air amount and flow rate, the metal shaft 5 was cooled and often misfired before the engine was started.

(4) Due to the fabrication of the heater 3, the inside of the metal shaft 5 ((Because the powder 6 of Magne/Ram is packed compactly, the pitch of the heating resistor 4 may be uneven, making it impossible to obtain an accurate pitch, or inside the sheath 5. This may cause a short circuit, causing local overheating or insufficient heating in the heater 3 due to its structure, burning too much oxygen in the intake system 2, resulting in an oxygen-deficient condition, or the heater 3 as a whole being unable to be heated sufficiently. Furthermore, because the pitch of the heating resistor 4 is uneven, uniform heating cannot be achieved, and as a result, a low voltage is applied at a constant rate, making it basically impossible to control the temperature by changing the applied voltage to maintain the temperature at a high temperature. Therefore, the complete explosion period was prolonged, misfires were likely to occur, and smooth starting performance was not achieved.

Therefore, in order to solve the above-mentioned problems, the present inventor formed the entire heater from ceramic, installed a tungsten heating resistor inside the heater, and further detected the heater temperature to control the applied voltage. I came up with a method to do this. That is, tungsten, which has the property of rapidly increasing its resistance as the temperature rises, is used as a heating resistor, and is embedded in a ceramic having high heat resistance, high strength, and high heat capacity to form an intake heater. Since the resistive heating element can be embedded using printed wiring by employing a pressure bonding method using a hot press, a ceramic heater without any irregularity in the pitch of the resistive heating element can be formed.

By forming such a heater, temperature control using voltage becomes possible for the first time.

A plurality of heaters are connected in parallel to efficiently heat the intake air, and a power source is connected to the heaters so that high voltage and low voltage can be applied to the heaters. are controlled by switching alternately. This switching control is performed under the supervision of a heater temperature detection element provided to detect the temperature of the heater which increases due to voltage application.

The heater temperature detection element, together with the connected circuit, has the function of sending a high voltage application command to the voltage control circuit before the heater temperature reaches the ignition temperature of the fuel, and a low voltage application command immediately after reaching the ignition temperature. . High voltage refers to a voltage sufficient to cause the saturation temperature caused by its application to exceed the heat resistance limit temperature of the ceramic, for example, 24 V for a large car battery. The term "low voltage" refers to a value at which the saturation temperature of the hinter brought about by its application approaches the heat-resistant limit temperature of the ceramic, for example, 9.5 V. In response to the above command, the voltage control circuit first applies a high voltage to the Innotake heater to rapidly raise the temperature of the heater, and then -
It has the function of changing the mark 7111 voltage to Q, as in CC low voltage bulky voltage. Therefore, high voltage and low voltage are alternately applied to the heater according to the output value of the rrt degree detection element, and it is possible to maintain a constant high temperature that satisfies the heat resistance of ceramic and also satisfies the ignition temperature. .

However, such rapid temperature rise (reduced start-up time)
It has been discovered that the intake heater temperature control device intended for the following problems exists.

The heater temperature detection element does not directly detect the temperature of the intake heater, but detects it by converting the current flowing through it, and is constituted by a resistor connected in series to the parallel circuit of the Innotake heater. Although this resistance value is set to be small, the value of the heating resistor made of tungsten is set to be even smaller than the above-mentioned detection resistance value because it causes the heater to rapidly rise in temperature. Therefore, when voltage is applied at the start of temperature rise, the value of current flowing through the intake heater is almost determined by the detected resistance value. For example, when two intake heaters are connected in parallel, a current determined by the detection resistance value is shunted to each heater by applying a high voltage, and the shunt current raises the temperature of the heater. At the same time, the heater resistance increases rapidly and the shunt current decreases.

However, if one of the heaters is disconnected, a large current determined by the detection resistance value will continue to flow through the remaining one without being shunted, far exceeding the rated capacity of the heater current. There was a strong possibility that if the power was left on while the engine was disconnected, it would burn out and become inoperable, making it impossible to start the engine.

[Purpose of the invention]

This invention was made in view of the above-mentioned circumstances, and its purpose is to apply high voltage and low voltage alternately.
In a temperature control device that rapidly heats heaters in parallel, if a part of the heater is disconnected, alternate application is stopped and the temperature is lowered.
By only applying pressure, the temperature of the remaining part of the heater can be raised normally to prevent the remaining part from being burnt out, and the engine can be started, and at the same time, it is possible to give an indication of a disconnection. The present invention provides a disconnection detection device.

[Structure of the invention]

In order to achieve the above object, according to the present invention, since the current flowing through the heater circuit changes due to a partial disconnection of the heater, a resistance sensing element that detects the magnitude of the circuit current is connected in series to the heater circuit. Accordingly, control of rapid temperature rise is canceled based on information from the resistance sensing element that occurs when a wire is disconnected.

That is, a disconnection detection circuit that generates a control signal in accordance with a predetermined output value generated in the detection element when a part of the heater is disconnected is connected to the resistance detection element, and the control signal of the disconnection detection circuit causes the intake The high voltage application function of the voltage control circuit that alternately applies high voltage and low voltage to the heater is stopped. In addition, the output of the disconnection detection circuit is connected to the drive circuit of the monitor lamp, which turns off the light when the intake heater reaches the initial ignition temperature to notify that the engine can be started, and the above control signal causes a blinking signal to be sent to the monitor lamp. It is configured so that the voltage is applied.

[Embodiments of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the Innotake heater disconnection detection device according to the present invention will be described in detail below with reference to the accompanying drawings. In the description, we will first describe the structure of the ceramic intake heater and the temperature control device for this heater, which are the premise of the present invention, and then refer to the disconnection detection device.

FIG. 3 is a schematic structural diagram showing one embodiment of the intake heater which is the premise of the present invention.

As shown in the figure, the heater 10 is formed into a rod-shaped body, and a cylindrical holder 13 extends from the vaporizer 6511 side to the combustion end 12 side.
is surrounded by. This heater 10 is entirely molded of ceramic by hot pressing, and has a heating resistor 1 made of tungsten inside with printed wiring etc.
4 is installed internally. Ceramic has a large heat capacity and releases the heat generated by the heating resistor 14 from the outer circumferential surface of the heater 10, while retaining a large amount of heat within itself and constantly maintains the entire heaters 1 and 0 at a high temperature to ensure stable combustion. It has the ability to continue. However, this ceramic retains the heating resistor 14 inside to prevent oxidation of tungsten due to rapid temperature rise, and to prevent the heater 10 from oxidizing as much as possible.
On the other hand, tungsten has the property of rapidly increasing its own resistance value as the temperature rises and generating high heat.
It has a function of rapidly heating a ceramic having a large heat capacity by applying a voltage, instantly raising the surface temperature of the heater 10, and vaporizing or igniting the supplied fuel 15.

Figure 4 shows such a ceramic intake heater 10.
This shows the temperature rise characteristics of Cross-sectional area 16mI! This is an example in which the sample was formed into a rectangular parallelepiped with a length of □Qmm and measured at room temperature. According to this, when a battery voltage of 24 V for large automobiles is applied to the heater 10, the energy consumption is only 1.9 se.
It can be seen that the fuel reaches the ignition temperature TF of 800° C. at c, and exhibits such a steep temperature rise characteristic that it directly exceeds the heat resistance limit temperature TL of the ceramic. On the other hand, when 9.5V, which is lower than the battery voltage, is applied, the saturation temperature 'F8 is 98V.
Heat resistance limit of 6°C (has a value very close to 1 temperature 'F1., exhibits a slower rise characteristic compared to the case of 24V, and reaches the ignition temperature TF) 2.5 s
It also costs ec. In this way, even if the voltage that causes the heater 10 to quickly turn off is applied continuously at high voltage VI (111i
-j A voltage that saturates to a value close to the thermal limit temperature TL at 1: is called a low voltage VL.

FIG. 5 shows the/stem circuit 16 that controls the voltage applied to the intake heater 10.

A parallel circuit consisting of a relay X1 circuit and a relay X2 contact is connected to the two intake heaters 10 connected in parallel, and the high voltages V and I of the battery 17 are directly applied by excitation of the relay XI. Also, by energizing relay X2, low voltage V1. is applied.

The sensing resistor S/R connected in series to the intake heater 10 is a heater temperature detection element 18 that senses the surface temperature of the heater 10, and its resistance value changes in proportion to the temperature of the heating resistor 14. Since the current changes in response to this change, the temperature of the heater 10 is sensed with equal constraints by detecting the voltage generated across the resistor S/R due to this current.

19 connected to the battery 17 is a key switch;
In the ON position, voltage can be supplied to the control circuit 20 which is the core of the system circuit 16 from the terminal (1). Still, the starter motor 21 is driven by exciting the ST deposition starter relay X5 and closing its contacts. The switch connected to the terminal is a water temperature detection element 22 that detects the temperature of the cooling water of the internal combustion engine, and when the water temperature Tw indicates a predetermined temperature 'rwo', for example, 5°C or less, it is turned ON and "'0" is output. Output and conversely 5
When the temperature is above °C, it turns OFF and outputs "l". Reference numeral 23 denotes an engine rotational speed detector, which is configured to output a ``l'' signal when the engine reaches a predetermined rotational speed NS, for example, 1000 rotations or more, and output a ``0'' signal when the engine rotational speed is lower than that. Note that L is a monitor lamp that will be described later.

FIG. 6 shows the control circuit 20 in detail, and in the same figure, the control circuit 20 is a portion surrounded by a dotted line.

As shown in the figure, the terminals connected to the output of the water temperature detection element 22 are G+, G2, G3 +G4
+ G5 and a driver G6 through a relay X+ circuit 24 to terminal ■, where it is connected to relay X1. This relay X+ circuit 24 has a crystal detection element 22
When it detects a temperature below 5°C, the detection output value becomes II Ou, which activates and turns driver G6 on. When key switch 19 is in the ON position, relay X! It has the function of being able to excite.

Then, the contact XI is closed by the energization of this relay XI, and a high voltage Vll is applied to the intake heater 10. As described above, an application circuit consisting of the relay X1 circuit 24, the relay X1, the battery 17, and the relay contacts is formed.

The monitor lamp L connected to the control circuit terminal 2 is connected to the gate G5, Gll, and driver G connected to the gate G5 output of the relay X+ circuit 24.

The lamp circuit 32 is connected to a lamp circuit 32 consisting of a lamp circuit 32, and is basically turned on and off in accordance with the excitation and demagnetization of the relay X+.

Terminal ■ connected to both ends of Sen/Fugu resistor S/R.

(2) is connected to the Tsuyumi circuit 25 in the control circuit 20, and its circuit output is connected to the gate G2 of the relay X1 circuit 24.
It is connected to the. Schmitt circuit 25 is the intake
When an input voltage corresponding to the ignition temperature TF of heater 1o of 800°C is received from the sensing resistor S/R, if the voltage value exceeds that voltage value, the output will turn ON, and if it is below that value, the output will turn OFF. 1″ output. In addition, in order to prevent malfunctions, an input voltage d corresponding to 8oo'C is set to OFF operation, and an input voltage corresponding to 700'C is set to ON operation to provide hysteresis.

Therefore, the output value generated at the sensing resistor S/R is 70
When it reaches 0'C, close gate G2 and IJ L/-X1
The circuit 24 is designed to deenergize (') FF j and IJ Ray X+. The output value still exceeds 800'C
When the voltage drops to 0, the output changes from 0'' to 1'' and serves to open gate G2. Therefore, the Schmitt circuit 25 connects the relay X1 circuit 24 to the Innotake heater 10.
It has a function to control ON/OFF according to the temperature of

On the other hand, the ON position of the key switch 19 is connected to the automatic voltage regulator 26 which supplies the power supply VCC to the gate group via the terminal (3) of the control circuit 20, and also connects to the gate G+ which drives the relay X4.

and its gate Gl of the relay X4 circuit consisting of the driver Gl+. It is connected to contact x4 of relay X4 which is connected to relay X2 via human power and terminal 3. Therefore, when the key switch 19 is turned ON, the control circuit 20 is supplied with the power V.
cc is supplied, relay X2 is energized, its contacts x2 are closed, and low voltage V
The application of L will continue. Especially relay contact x2
The circuit is connected in parallel with the relay contact X3 circuit, and when this relay contact X1 circuit is turned on, it short-circuits the relay contact X2 circuit, so when the relay contact High voltage VI
+ is applied. In this way, the key switch 19 is turned on.
The reason for the configuration in which the relay contact X2 circuit is always ON by operation is to prevent the intake heater 10 from becoming de-energized during the switching interval between the low voltage vL and the high voltage VI+. In this way, if the key switch 19 is in the ON position, the relay
is turned off and relay X1 is deenergized, high voltage v1. is applied to the intake heater 10. Instead, a low voltage VL will be applied. Conversely, if relay X1 is energized, high voltage Vl will be applied to intake heater 1o. According to '2, /Umit circuit 25,
Gate GIO, Gll, relay x4, relay contact x
4, a switching circuit consisting of a relay X2, a battery 11, and two phosphorus contacts is formed. In addition, if the switching time is extremely fast and the interval can be ignored, do not adopt the method of constantly applying the low voltage VL, but literally alternately switch the low voltage VL and the high voltage V11 to apply it. Of course, it is possible. A voltage control circuit is formed by the above-mentioned application circuit and this switching circuit. The above configuration is an example of the basic configuration of an intake heater temperature control device, which is the premise of the present invention.

The present invention is constituted by organically adding the following characteristic configuration to the above configuration.

(In Figure 5, 30il-1 disconnection detection circuit, power supply V
It operates after a certain time + c has passed after CC is turned on, and when the input voltage is above a predetermined value ■□, it outputs "1", and when it is after that, it has the function of outputting "O" as before the elapse of a certain time jc. The input of this circuit 30 is a sensing resistor S/ in order to share the input with the already mentioned Tsumitsu circuit 25.
The voltage across R is applied. Therefore, the disconnection detection circuit 30 generates the control signals ``1'' and ``o'' depending on the magnitude of the current flowing through the sensing resistor S/R.

The output of the disconnection detection circuit 30 is connected to the lamp circuit 32 together with the relay X1 circuit 24.

The relay X1 circuit 24 is connected to its gate G2, and if the current flowing through the sensor resistor S/R is abnormally low, the 1-X1 circuit 24 is turned OFF'L, and the Innotheque
i! Do not apply high voltage ■□ to the heater 10! It's in control. Further, the lamp circuit 32 is connected to the gates 1-G2. through gate G7 and further through gate G3o.
8 is connected to. A gate G25 is connected to this gate G:1O and has a function of directly transmitting the output of an oscillator 45 whose duty cycle can be arbitrarily set when the key switch 19 is in the ON position. Therefore, the disconnection detection circuit 30 is connected to the sensor song resistor S/R.
When the current flowing through the circuit is normal, the gate GW is opened for a certain period of time and the signal from the relay The lamp circuit 32 is controlled so as to send out the signal as it is.

In FIG. 6, 31 is a fuel circuit that controls the fuel supplied to the intake heater 10, relay X3 is a relay for the fuel valve, 26 is a release circuit that deactivates the entire control circuit 20, and 33 is a relay. This circuit deactivates only the X1 circuit 24.

The operation of the present wire breakage detection device having the above configuration will be described.

FIG. 7 shows a tight chart based on the circuit configuration of FIG. 6.

First, the key switch 19 is switched from the OFF position to the ON position when starting the machine. This switching activates the automatic voltage regulator 26 to supply power VCC to the control circuit 20. Simultaneously with this supply, the relay X4 circuit is activated and relay X2f is energized. Here, when the cooling water temperature of the internal combustion engine is below the predetermined value TWO of 5°C, the gate G2 of the phosphor XI circuit 24 is opened (initially, the output of the TSUMITSU circuit 25 is
Since the temperature of
is excited and a high voltage vH of 24V is applied to the intake heater 10 via its contact xl. At the same time, the V-wrap circuit 32 also responds and the monitor lamp L lights up. The initial application time T of 24 V shown in FIG. 7 is as follows: By using tungsten as the heating resistor 14, the time it takes for the Innotheque heater 10 to reach the ignition temperature TF of 800°C is extremely short, as mentioned above. The value is 19 to 2.0 seconds, but this time is equivalent. That is, battery 1
By directly applying a pressure of 70°C to the Innotheque heater 10, its surface temperature rapidly rises to 800°C.
At the same time, the output value is detected by the sensor resistor S/R, and the output of the tsumitsu circuit 25 is inverted from 1 to "1".
” to “0” (Accurately, it is reversed at 700°G, but for convenience, we will use 800°C as the switching point). Due to this reversal, relay , the relay contact circuit is opened, and the relay contact circuit of relay
．． 5V will be applied instead of the high voltage VH24V after 19 to 20 seconds. By this switching, the reintake heater 10 is set to 11 of the ceramic 1 heat limit temperature TL.
00℃ will be avoided. Also, unlike the high voltage VH, the voltage value of the low voltage VL is low, so the Innotheque heater 10 exposed to the cold air of the intake system after 95V is applied loses heat and begins to drop in temperature. Each time the descending F ignites T
When the temperature reaches 800°C of F, roundness/Umit circuit 25
is activated and inverts its output from "0" to "]" and excites l/-XI. In this way, 7. of Innotheque heater 10. The voltage applied to this heater is alternately switched between a high voltage Vl+ and a low voltage VL depending on the W1 degree. During this time, the monitor lamp L is connected to the disconnection detection circuit 3.
0 output "i" causes the gate G of the lamp circuit 32 to
7 is closed, so it won't light up. Therefore, the monitor lap L is lit for a certain period of time tc only once when it first appears. This time tc is desirably made to coincide with the time Tm for the intake heater 10 to reach 800°C. This is to give the driver information that it is okay to start the engine by confirming that the monitor lamp L is off.

In this way, high voltage VII and low voltage ■ are connected to the intake
Since it is applied alternately to the heater 10, simply turn on the high voltage.
・Unlike when it is turned off, even when the high voltage VH is turned off, it is heated at a low voltage, so the intake
The temperature of the heater 10 can be maintained within an extremely high temperature range that is above the ignition rIIiA degree TF and below the ceramic heat resistance limit temperature TL.

In this way, the fuel supplied to the intake heater 10 evaporates and vaporizes, ignites, and continues to burn, heating the surrounding air.

Next, an abnormal case where one of the Innotheque heaters 10 is disconnected will be explained based on FIG. 8. The initial resistance value of the intake heater 10 is set to be quite small in order to rapidly raise the temperature, and is smaller than that of the sensing resistor S/R. Therefore, under normal conditions, the voltage drops ■8/R and ■1/□ at the sensing resistor S/R and the intake heater 10 will draw a curve as shown by a solid line over time, but in an abnormal situation, Since approximately two currents of normal current flow through the intake heater 10, a curve with a large change is drawn as shown by a broken line, and there is a noticeable difference between the two curves. Predetermined input value of disconnection detection circuit 30 ■□
is set to be between each voltage drop SA and v'8/R of the sensing resistor S/R, which have a noticeable difference over a certain period of time tc, so when the heater is disconnected, the disconnection detection circuit 30 detects O'' control signal is output.For this reason, the gate G2 is closed, so the output of the tsumitsu circuit 25 is turned on.
(Regardless of i'J, the relay X1 circuit 24 becomes inactive,
The application of high voltage II to the intake heater 10 is canceled. Since the gate Gsa is opened at the same time, the lamp circuit 32
The output of the oscillator 45 is sent out to cause the monitor lamp L to blink at a period based on its duty cycle.

Therefore, since the low voltage VL is constantly applied to the intake heater 10, it is possible to prevent the remaining heater from burning out due to excessive current, and the low voltage VL is applied even though the temperature rises slowly. It is possible to reliably increase the temperature and raise the Peter 10 to the ignition temperature TF after 125 seconds at the latest. During this period, the monitor lamp L still notifies the driver of a warning signal by flashing, so the driver can sense the intake heater disconnection and take appropriate measures such as repair.

Note that the control circuit 20 is not limited to the above-mentioned embodiment, and it goes without saying that modifications can be made within the scope of the present invention.

In summary, the present invention provides the following distinct effects.

(1) Since high voltage and low voltage are applied alternately to the intake heater, the temperature can be raised to the ignition temperature extremely quickly without destroying the heater, and the temperature can be maintained at a constant temperature. The startability of the engine can be improved as much as possible. In addition, in the event of a disconnection of the Innotheque heater, the application of only high voltage is stopped and low voltage is continued, making it possible to prevent burnout of the remaining heater and ensure startability of the engine. .

(2) Since the control signal of the disconnection detection circuit is also sent to the monitor lamp, it is possible to notify the driver of the disconnection of the intake heater and prevent the abnormal condition from continuing.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the engine showing the installation position of the intake heater, Fig. 2 is a schematic sectional view of a conventional intake heater, and Figs. 3 to 8 are diagrams showing disconnection of the intake heater according to the present invention. 3 is a schematic sectional view of the Innotake heater, FIG. 4 is a temperature rise characteristic diagram, FIG. 5 is a system circuit diagram, FIG. 6 is a detailed diagram of the same, and FIG. The figure is a timing chart of FIG. 6, and FIG. 8 is a voltage characteristic diagram when the intake heater is normal and when it is disconnected. In the figure, 10 is an intake heater, 18 is a sensing resistor which is an example of a resistance detection element, 30 is a disconnection detection circuit, 24, X+, 17, x+ and 25+GI
n + GII + X4 + x4 + X2
+17 +X2 is an application circuit and a switching circuit that constitute a voltage control circuit. VII is a high voltage, VL is a low voltage, VR is a predetermined output value, and L is a monitor lap. Patent applicant: Isuma Jidosha Co., Ltd. Attorney [Nobu Kinutani J41゜

Claims (1)

[Claims] It consists of multiple intake heaters connected in parallel, and high voltage and low voltage are applied alternately to both ends of the intake heater.
Temperature control of an intake heater, which is equipped with a voltage control circuit that causes the heater to generate heat to a constant temperature, and uses the heat generated to ignite fuel supplied to the intake heater to heat intake air flowing into the intake system of an internal combustion engine. In the device, a resistance detection element is connected in series to the intake heater to detect the magnitude of the current flowing through them, and a disconnection detection circuit is provided to generate a control signal according to a predetermined output value of the resistance detection element. The control signal for the disconnection detection circuit is added to the voltage control circuit described above to stop the alternating application of high voltage and low voltage, so that only the low voltage is applied to the intake heater, and is also supplied to the monitor lamp. A disconnection detection device for an intake heater, characterized in that it generates a warning signal.