JP2007239645A - Air heater system for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air heater for an internal combustion engine capable of preventing abnormal rise in the temperature of a heater unit without fail and protecting the heater unit properly. <P>SOLUTION: A PWM unit 230 performs duty control of electric power supplied into the heater unit 100 by turning a semiconductor switch 232 on/off by a PWM circuit 231 based on instructions for heating from an ECU 210. A fuse 240 fused when performing continuous current carrying into the heater unit 100 being equivalent to duty-control by duty ratio of 100% to shut off current carrying into the heater unit 100 at abnormal time is provided. The PWM unit 230 performs the duty control by a duty ratio for preventing the fuse 240 from functioning usually. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an air heater system for an internal combustion engine used for intake air heating of, for example, a vehicle diesel engine.

  In a self-ignition engine such as a diesel engine, when the temperature of intake air to the engine is low, the air-fuel mixture compressed in the cylinder may not reach an ignition state. In order to solve such a problem, there is an engine of this type that includes a heater unit that raises the temperature of intake air inside the intake pipe. This heater unit is composed of a schematic frame and an electric heating element fixed to the frame, and generates heat when the electric heating element is energized, thereby heating the intake air. is there. This heater unit constitutes an air heater system for an internal combustion engine together with the energization unit that controls the energization.

  By the way, since the air heater system is configured to include a heater unit and an energization unit, a failure due to an abnormality of the energization unit may occur even if the heater unit is normal. For example, unintentional energization to the heater unit continues due to problems with the electronic control unit (ECU) that controls the air heater system itself, contact welding of the relay switch in the energization unit that turns on and off the energization of the heater unit, etc. If it is performed, there is a risk of causing an abnormal temperature rise of the heater unit. Such an abnormal temperature rise causes various problems such as a failure of the heater unit.

Therefore, conventionally, a technique has been devised that detects the temperature of the heater unit and cuts off the power to the heater unit by switching a switch or the like when the temperature exceeds a predetermined overheated temperature (for example, , See Patent Document 1).
Japanese Patent Laid-Open No. 2005-67222

  However, in the prior art, it is also assumed that the mechanism itself for switching a switch or the like is broken, and in that case, there is a concern that an abnormal temperature rise cannot be avoided.

  The present invention has been made to solve the above-described problems, and an object thereof is to reliably prevent an abnormal temperature rise of the heater unit and to appropriately protect the heater unit. Is to provide.

  Hereinafter, each configuration suitable for solving the above-described problems will be described in terms of items. In addition, the effect etc. peculiar to the structure which respond | corresponds as needed are added.

  Configuration 1. The air heater system for an internal combustion engine of this configuration has a heater unit for the internal combustion engine and switching means for switching energization / non-energization to the heater unit, and the electric power supplied to the heater unit by the switching means. An air heater system for an internal combustion engine including an energization unit that performs duty control, wherein electric power equal to that in which the duty control is performed with a duty ratio that is equal to or greater than a predetermined ratio is supplied to the heater unit. Current interrupting means for interrupting energization to the heater unit is provided, and the energization unit performs duty control with a duty ratio lower than the predetermined ratio.

  In Configuration 1, the energization unit performs duty control of the power supplied to the heater unit by switching between energization / non-energization to the heater unit by the switching means. Here, in particular, when electric power equal to the duty control with a duty ratio greater than or equal to a predetermined ratio is supplied to the heater unit, the heater unit is energized by the current interrupting means such as a fuse. Blocked.

  Originally, a current interrupting means such as a fuse is inserted into a circuit so as to function when an excessive current flows through the circuit due to an unintended short circuit. For this reason, even if the heater unit is continuously energized, there is no guarantee that the current interrupting means will function.

  In this regard, according to Configuration 1, even if no short circuit occurs, the current interrupting means functions when the power supplied to the heater unit exceeds a certain value. Here, the electric power at which the current interrupting unit functions is equal to the electric power when the duty control with the duty ratio equal to or higher than the predetermined ratio is performed in the energization unit. If the predetermined ratio is assumed to be 80%, the current interrupting means functions when electric power equal to that in which the duty control is performed with a duty ratio of 80% or more (that is, 80 to 100%) is supplied. As a result, for example, when the energization to the heater unit cannot be interrupted due to a failure of the switching means, that is, the energization to the heater unit is continued (corresponding to duty control with a duty ratio of 100%). The current interrupting means functions to interrupt the energization of the heater unit.

  As a premise for adopting such a configuration, in configuration 1, in a normal time, the energization unit performs duty control with a duty ratio lower than a predetermined ratio. In other words, during normal times, the duty ratio is made relatively small so that the power (average current) supplied to the heater unit is made small so that the current interrupting means does not function.

  Therefore, according to the configuration 1, even if a situation where the heater unit is continuously energized due to, for example, a failure of the switching means, the abnormal temperature rise of the heater unit can be reliably prevented, and the heater unit can be appropriately Can be protected.

  The switching means is embodied as a semiconductor switch as an example. Moreover, you may implement as a relay switch. In particular, when a semiconductor switch is employed, it may happen that the switch remains turned on (energization continued state) due to the failure. Therefore, especially when the switching means is formed of a semiconductor switch, the effect of the above-described configuration 1 stands out.

  Also, it has already been described that an example of the current interrupting means is a fuse. However, any means that can interrupt current based on electric power (average current) may be used. For example, a ceramic element having PTC characteristics may be adopted. Good.

  Configuration 2. The internal-combustion-engine air heater system according to the present configuration further includes acquisition means for acquiring temperature specifying information capable of specifying the temperature of the heater unit in the configuration 1, and the energization unit is configured by the acquisition means. Based on the acquired temperature specifying information, it has a determination means for determining whether or not the temperature of the heater unit is equal to or higher than a predetermined temperature, and the temperature of the heater unit is equal to or higher than the predetermined temperature by the determination means. If it is determined, the switching unit cuts off the power supply to the heater unit.

  According to the configuration 2, when the temperature of the heater unit becomes equal to or higher than the predetermined temperature, the energization to the heater unit is interrupted by the switching means, so that the temperature of the heater unit can be prevented from becoming higher than the predetermined temperature. Contributes to the protection of the unit. When such a mechanism itself fails and the electric power supplied to the heater unit exceeds a certain value, the current interruption means cuts off the power to the heater unit as in the first configuration.

  Thus, when the fail safe mechanism by the switching means is adopted in addition to the configuration of the means 1, the configuration by the current interrupting means shown in the means 1 can be the final fail safe at the time of abnormality. The effect of the above configuration 1 stands out.

  The temperature specifying information acquired by the acquisition unit may be the temperature of the electric heating element of the heater unit itself, or may be a temperature at which the temperature of the heater unit can be estimated indirectly. Since the resistance value of the electric heating element used in the heater unit is known by design, for example, the temperature of the heater unit can be indirectly specified by obtaining the current value supplied to the heater unit. . Therefore, it may be information other than temperature, and may be information indicating the energization status of the heater unit and the like.

  Further, “the predetermined temperature may be a predetermined excessive temperature”.

  Configuration 3. The air heater system for an internal combustion engine of this configuration is the above configuration 1 or 2, wherein the energization unit is configured as an independent circuit connected to an electronic control unit that controls a vehicle, and a heating instruction sent by the electronic control unit When there is, the duty control is started, and when there is a non-heating instruction, the duty control is stopped.

  Generally, a vehicle equipped with a diesel engine is controlled by an electronic control unit (ECU). Therefore, it is conceivable to realize the function of the energization unit as one function of the electronic control unit.

  However, from the viewpoint of retrofit to an existing engine, an air heater system for an internal combustion engine including an energization unit connected to the outside of the ECU is desired. Therefore, as in the present configuration 3, the duty control is started when there is a heating instruction sent by the electronic control unit, and the duty control is stopped when there is a non-heating instruction. For example, when there is a heating instruction from the electronic control unit, the energization unit performs duty control with a fixed duty ratio of 30%, or changes the duty ratio according to the situation in the range of 20 to 40%. For example, duty control is performed. Moreover, when there is a non-heating instruction from the electronic control unit, the energization unit stops the duty control. This corresponds to duty control with a duty ratio of 0%. In this way, for example, the duty control of the heater unit can be performed using an electronic control unit designed to output only an on / off signal to the heater unit, which is advantageous in terms of retrofit. .

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a plan view showing a heater unit 100 arranged in an intake path of a vehicle engine in the present embodiment. The heater unit 100 includes a frame body 110, an electrothermal heating element 120 held by the frame body 110, and first and second connections fixed to the frame body 110 and electrically connected to the electrothermal heating element 120. Terminals 130 and 140 are provided. Further, the frame 110 is provided with a thermistor 220 for detecting the temperature of the heater unit 100 (according to the temperature of the electrothermal heating element 120).

  The frame 110 is a metal body made of an aluminum alloy and formed into a substantially rectangular ring shape by die casting. The frame 110 is formed with first, second, and third through holes 111, 112, and 113 that pass through between the outer surface 110a and the inner surface 110b. An internal thread is formed inside the third through hole 113. In addition, four attachment holes 110 c are formed in the corner portion of the frame body 110 in a direction orthogonal to the through holes 111, 112, and 113.

  In addition, two recesses 114 are formed on the inner side surface 110b of the frame body 110 at positions facing each other. Each of these two recesses 114 is provided with a metal bracket 115 having a substantially U-shaped cross section. Furthermore, an insulator 116 is provided inside each metal bracket 115 with a leaf spring 117 interposed therebetween (see a broken portion in FIG. 1).

  The electrothermal heating element 120 is a heating element obtained by forming a strip-like thin plate made of an iron-chromium alloy into a meandering shape. The electrothermal heating element 120 is held by the frame body 110 while being electrically insulated by fitting a plurality of bent portions 121 bent in an arc shape into the insulator 116. The insulator 116 is urged inward by the action of the leaf spring 117 so that the electrothermal heating element 120 is securely held with respect to the frame 110.

  The first connection terminal 130 is made of a metal bolt, and is inserted into the first through hole 111 of the frame body 110 via an insulating washer 131. Similarly, the second connection terminal 140 is made of a metal bolt, and is inserted into the second through hole 112 of the frame 110 via the insulating washer 141. Insulating sleeves 132 and 142 are inserted into the first and second through holes 111 and 112 in such a manner that the first and second connection terminals are inserted therethrough. With this configuration, the frame 110 and the first and second connection terminals 130 and 140 are electrically insulated.

  Further, insertion holes are formed at both ends of the electrothermal heating element 120, and the first and second connection terminals 130 and 140 are inserted through the insertion holes. Thereby, the electrothermal heating element 120 is electrically connected to the first connection terminal 130 and the second connection terminal 140.

  The thermistor 220 is provided in the third through hole 113. The thermistor 220 has a rod-shaped sensor part 220a and a cylindrical part 220b provided around the sensor part 220a. A male screw corresponding to the inner surface of the third through hole 113 is formed on the outer surface of the cylindrical portion 220b, and the thermistor 220 is screwed into the third through hole 113 via the cylindrical portion 220b. . In the screwed state as described above, the sensor unit 220a is inserted through the third through-hole 113 and the tip thereof protrudes from the inner side surface 110b.

  As described above, the heater unit 100 is provided in the intake path of the vehicle engine. Specifically, the heater unit 100 is fixed in the intake path that connects an air cleaner (not shown) and the intake manifold of the internal combustion engine. More specifically, the heating element 120 of the heater unit 100 is provided in the frame 110 so that the heating element 120 of the heater unit 100 is positioned in the intake path so that the gas (intake air) flowing in the intake path can be heated. The four mounting holes 110c are used to be fixed by a bolt (not shown).

  Next, a vehicle air heater system 200 as an “air heater system for an internal combustion engine” including the heater unit 100 configured as described above will be described.

  As shown by a thick solid line in FIG. 2, in the vehicle air heater system 200, the heater unit 100 includes an in-vehicle battery 300 via a fuse 240 as “current interrupting means” and a semiconductor switch 232 of the PWM unit 230 described later. Is electrically connected. Thereby, when the semiconductor switch 232 is turned on (conductive state), the heater unit 100 is energized from the in-vehicle battery 300 (electric power is supplied to the heater unit 100).

  In the present embodiment, duty control of power supplied to the heater unit 100 is performed by repeatedly turning on / off the semiconductor switch 232. As a configuration for this, as shown in FIG. 2, the vehicle air heater system 200 further includes an ECU 210 and a PWM unit 230.

  The ECU 210 is a computer system that manages various controls of the vehicle engine. The ECU 210 sends a heating / non-heating instruction to the PWM unit 230.

  The PWM unit 230 includes the semiconductor switch 232, the PWM circuit 231, and the determination circuit 233.

  The semiconductor switch 232 is configured with a MOSFET as a basic structure. Then, on / off operation is performed based on the signal from the PWM circuit 231. As described above, when the semiconductor switch 232 is turned on, the heater unit 100 is energized. On the other hand, when the semiconductor switch 232 is turned off, the heater unit 100 is de-energized. The

  The PWM circuit 231 is a circuit that generates a PWM (Pulse Width Modulation) signal, and the generated PWM signal is output to the semiconductor switch 232. Then, the PWM circuit 231 outputs a PWM signal with a duty ratio of 30% when there is a heating instruction from the ECU 210. Based on the output of the PWM signal, the semiconductor switch 232 is turned on / off based on the PWM signal, and duty control is started. On the other hand, when there is a non-heating instruction from the ECU 210, the PWM circuit 231 keeps the semiconductor switch 232 off and stops duty control. In other words, in this case, the PWM circuit 231 outputs a PWM signal having a duty ratio of 0% to the semiconductor switch 232. Further, the PWM circuit 231 also turns off the semiconductor switch 232 (duty ratio 0%) when a predetermined determination signal is input from the determination circuit 233.

  The determination circuit 233 determines whether or not the temperature of the heater unit 100 has reached a predetermined overheating temperature (for example, 1000 ° C.) based on the signal from the thermistor 220. When it is determined that the temperature of the heater unit 100 has become an excessive temperature, a predetermined determination signal is output to the PWM circuit 231. As a result, the semiconductor switch 232 is turned off by the PWM circuit 231 as described above. With this configuration, when the temperature of the heater unit 100 reaches an excessive temperature, the energization to the heater unit 100 is cut off.

  The fuse 240 is a so-called current fuse, and blows when the power supplied to the heater unit 100 exceeds a certain value. In the present embodiment, when the heater unit 100 is continuously energized (a state corresponding to duty control with a duty ratio of 100%), this fixed value is exceeded, and the fuse 240 is blown.

  Next, the operation of the PWM unit 230 will be described in detail based on the timing chart of FIG.

  First, in a period from time t1 to time t2, heating of the heater unit 100 called preheating is performed prior to starting the engine. Specifically, when there is a predetermined engine key operation, a heating instruction from ECU 210 is sent to PWM unit 230. That is, during the period from time t1 to time t2, the signal from the ECU 210 is turned on (High level), and duty control by the PWM unit 230 is performed. The duty ratio in the duty control is 30% as described above. Thereby, the temperature of the heater unit 100 rises rapidly to T1. Note that this preheating period is predetermined.

  Next, at time t3, cranking is started by a predetermined engine key operation (CRANKING). Here, the heater unit 100 is not heated, but the air heated by the heater unit 100 heated by the preheating is sent to the combustion chamber. As a result, the engine starts (RUN) at time t4. At time t4 when the engine is started, the temperature of the air heater is T2 (T2 <T1).

  From time t4, the heater unit 100 is heated after engine start, which is called after heat. During this period, the signal from the ECU 210 is turned on, and duty control by the PWM unit 230 is performed again. As a result, the temperature of the heater unit 100 quickly rises to approximately T1. Then, since the air flow is generated in the intake passage by starting the engine, the temperature of the heater unit 100 changes substantially constant. Note that the after-heat period is also predetermined in the same manner as the pre-heat period.

  Incidentally, in FIG. 3, the engine is stopped at time t5 (STOP). In this case, as indicated by a solid line in the figure, the signal from the ECU 210 is turned off (Low level) in order to stop the after heat, and thereby the duty control by the PWM unit 230 is stopped (duty ratio 0%). Equivalent to control). Therefore, at the normal time, the temperature of the heater unit 100 decreases after time t5 (solid line in FIG. 3).

  However, at time t5, the signal from the ECU 210 may not turn off due to, for example, a malfunction of the ECU 210 (broken line in FIG. 3). In this case, the PWM unit 230 continues the duty control according to the heating instruction from the ECU 210 (broken line in FIG. 3). When such a situation occurs, the temperature of the heater unit 100 will continue to rise because the engine is stopped and there is no air flow in the intake path.

  Therefore, in the present embodiment, as the first fail safe, the temperature of the heater unit 100 is constantly detected by the thermistor 220, and when the above situation occurs, the temperature of the heater unit 100 is predetermined at time t7. When the temperature rises to the excessive temperature T3, a predetermined determination signal (High level signal) is output from the determination circuit 233 of the PWM unit 230 to the PWM circuit 231. Thereby, as described above, the semiconductor switch 232 is turned off by the PWM circuit 231 (corresponding to control with a duty ratio of 0%). As a result, the temperature of the heater unit 100 decreases from time t7 (broken line in FIG. 3).

  However, the case where the semiconductor switch 232 which comprises the said 1st fail safe will fail is assumed. If the semiconductor switch 232 fails, the semiconductor switch 232 may remain on. This is a state in which continuous power supply to the heater unit 100 (power supply corresponding to duty control with a duty ratio of 100%) is performed. In FIG. 3, a two-dot chain line is used to show a state in which the semiconductor switch 232 is always on at time t6. In such a state, since the engine is stopped at time t5 and there is no air flow in the intake path, the temperature of the heater unit 100 rapidly increases from time t6.

  In this regard, in the present embodiment, as the second fail safe, when the power supplied to the heater unit 100 exceeds a certain value, the fuse 240 is blown. As a result, the energization of the heater unit 100 is interrupted, and as a result, the temperature of the heater unit 100 falls from the temperature T4 slightly later than the time t6 (two-dot chain line in FIG. 3).

  Note that the ECU 210 in this embodiment corresponds to an “electronic control unit”, and the PWM unit 230 corresponds to an “energization unit”. The semiconductor switch 232 included in the PWM unit 230 corresponds to “switching means”, and the determination circuit 233 corresponds to “determination means”.

  As described above in detail, according to the present embodiment, as the first fail safe, the temperature of the heater unit 100 is constantly detected by the thermistor 220, and the temperature of the heater unit 100 is set to a predetermined excessive temperature. Then, a predetermined determination signal is output from the determination circuit 233 of the PWM unit 230 to the PWM circuit 231. As a result, the semiconductor switch 232 is turned off by the PWM circuit 231.

  In addition to this, according to the present embodiment, even if the first fail safe does not function, the second fail safe functions. Specifically, when the electric power supplied to the heater unit 100 exceeds a certain value, the fuse 240 is blown and the energization to the heater unit 100 is interrupted. In this embodiment, when energization to the heater unit 100 corresponding to duty control with a duty ratio of 100% is performed, the power to the heater unit 100 exceeds a certain value. Accordingly, even when the semiconductor switch 231 constituting the first failsafe fails and the energization to the heater unit 100 cannot be interrupted, the energization to the heater unit 100 is interrupted by the melting of the fuse 240.

  As a result, the abnormal temperature rise of the heater unit 100 can be reliably prevented, and the heater unit 100 can be appropriately protected.

  In particular, when the semiconductor switch 232 is employed, it may be in an on state (energization continued state) due to the failure. Therefore, in the configuration of the present embodiment using the semiconductor switch 232, an extremely large effect is achieved by the second fail safe. Further, since the second fail safe functions as a final fail safe, the heater unit 100 can be reliably protected in combination with the function of the first fail safe.

  Further, according to the present embodiment, since the PWM unit 230 is provided separately from the ECU 210, heating / non-heating of the heater unit is controlled (for example, an on / off signal is output to the outside as in the present embodiment). ) Retrofit to an existing engine equipped with an engine ECU is possible.

  In addition, this invention is not limited to the said embodiment at all, In the range which does not deviate from the meaning of invention, it can implement with a various form. For example, you may implement as follows.

  (A) Although the fuse 240 is provided on the in-vehicle battery 300 side (upstream side) with respect to the heater unit 100 in the above embodiment, the fuse 240 is provided somewhere in the circuit indicated by the thick solid line in FIG. In particular, the arrangement position of the fuse 240 is not limited. For example, as in a vehicle air heater system 201 shown in FIG. 2B, the heater unit 100 (electric heating element 120) may be provided on the downstream side.

  (B) Although the semiconductor switch 232 is employed as the “switching means” included in the PWM unit 230 in the above embodiment, a relay switch may be employed.

  (C) Although the thermistor 220 is used to detect the temperature of the heater unit 100 in the above embodiment, the thermistor 220 is not limited to the thermistor 220 as long as the temperature of the heater unit 100 can be specified. For example, information obtained by monitoring the energization status of the heater unit 100 may be used. Further, for example, the temperature of engine cooling water may be used.

It is a top view which shows the structure of the heater unit which comprises an electrothermal heating element. (A) is explanatory drawing which shows the structure of the vehicle air heater system of embodiment, (b) is explanatory drawing which shows the structure of the vehicle air heater system of another embodiment. It is a timing chart which shows operation | movement of the air heater system for vehicles.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Air heater, 110 ... Frame, 120 ... Electric heating type heating element, 200, 201 ... Vehicle air heater system, 210 ... ECU, 220 ... Thermistor, 220a ... Sensor part, 220b ... Cylindrical part, 230 ... PWM unit, 231 ... PWM circuit, 232 ... semiconductor switch, 233 ... determination circuit, 240 ... fuse, 300 ... vehicle battery.

Claims (3)

A heater unit for an internal combustion engine;
An air heater system for an internal combustion engine comprising switching means for switching energization / non-energization to the heater unit, and an energization unit that performs duty control of electric power supplied to the heater unit by the switching means. ,
When electric power equal to the duty control with a duty ratio greater than or equal to a predetermined ratio is supplied to the heater unit in the energization unit, current interrupting means for interrupting energization to the heater unit is provided,
The heater unit system for an internal combustion engine, wherein the energization unit performs duty control with a duty ratio lower than the predetermined ratio. The air heater system for an internal combustion engine according to claim 1,
Furthermore, it has an acquisition means for acquiring temperature specifying information capable of specifying the temperature of the heater unit,
The energization unit is
Based on the temperature specifying information acquired by the acquisition means, and having a determination means for determining whether or not the temperature of the heater unit is equal to or higher than a predetermined temperature,
An air heater system for an internal combustion engine, wherein when the determining means determines that the temperature of the heater unit has become equal to or higher than the predetermined temperature, the switching means interrupts energization of the heater unit. The air heater system for an internal combustion engine according to claim 1 or 2,
The energization unit is configured as an independent circuit connected to an electronic control unit that controls the vehicle, and starts the duty control when there is a heating instruction sent by the electronic control unit, and when there is a non-heating instruction, An air heater system for an internal combustion engine, wherein duty control is stopped.

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