JP2010090800A - Glow plug control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a glow plug control device capable of stably controlling current carrying to a glow plug even under a low voltage condition where the communication reliability of CAN cannot be maintained. <P>SOLUTION: The glow plug control device includes a power source 1, a glow plug GP, a glow plug control device GCU3, and an electronic control device ECU2 generating control signal SI. ECU2 and GCU3 are connected via a low voltage signal line 23. Output of a switching element SW22 provided on the ECU2 side and a first resistor R<SB>1</SB>provided on the GCU3 side are connected via the low voltage signal line 23 and are connected to the power source 1 on the GCU3 side. The output voltage V<SB>IN</SB>of SW22 is input to a differential amplifying circuit CMP30 provided in GCU3. A second resistor R<SB>2</SB>and a third resistor R<SB>3</SB>proportionally dividing power source voltage +B are provided between the power source 1 and ground GND. Electric potential +B*R<SB>3</SB>/(R<SB>2</SB>+R<SB>3</SB>) between the second resistor R<SB>2</SB>and the third resistor R<SB>3</SB>is input to the differential amplifying circuit CMP30 as threshold voltage V<SB>REF</SB>. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a glow plug control device that controls energization of a glow plug that assists ignition of a diesel engine.

In diesel engines, oxygen sensor, NOx sensor, temperature sensor, accelerator opening sensor, engine speed sensor, speed sensor, crank angle to further improve combustion efficiency and reduce environmental load substances such as NOx and PM Using various sensors such as sensors, current value sensors, voltage value sensors, etc. to grasp the operating status of the engine, glow plugs, cranking devices, power generation devices, fuel injection devices, supercharging and mixing devices, EGR devices, exhaust gas purification devices The actuator is controlled.
A network such as a controller area network (hereinafter abbreviated as CAN) by a device such as various sensors and actuators, a device driver that drives these devices, and an electronic control unit (hereinafter abbreviated as ECU) that controls the entire engine. Are configured to exchange data frames, error frames, etc. with each other via a high-speed multiplex communication bus such as a CAN bus having a communication speed of 500 kbps to 1000 kbps according to a predetermined communication standard such as a CAN protocol (for example, patents) Reference 1).

A glow plug is provided for each cylinder of the engine, and assists ignition by heating fuel injected into the combustion chamber or an air-fuel mixture in the combustion chamber. In recent years, lowering the rating has been attempted in order to improve the temperature rise rate of the glow plug. In addition, in order to further improve combustion efficiency and reduce exhaust emissions, not only pre-glow that preheats when the engine starts but also afterglow that always energizes according to the operating conditions. .
For such glow plug control, a pulse width modulation (PWM) control device that controls the power supply by changing the duty ratio of the energization pulse is used (see, for example, Patent Document 2).
JP 2004-252963 A JP 2007-292063 A

However, for example, in a cryogenic environment where the temperature is below 20 ° C. below zero, the internal resistance of the battery may increase, leading to a decrease in electromotive force. Also, the inrush current tends to increase with the lower rating of the glow plug. In addition, the inrush current flowing through the starter during cranking is large. For this reason, particularly when starting in a cryogenic environment, there is a possibility that the battery load is large and a significant voltage drop is caused temporarily.
On the other hand, since the communication operation guarantee voltage of CAN is about 8V or more, when the power supply voltage is lowered to 8V or less, the communication reliability of CAN is significantly impaired. For this reason, for example, malfunctions such as energization of the glow plug being stopped due to abnormal data transmitted from the ECU with respect to the PWM control of the glow plug may be caused, and the engine may not be started.

  In addition, when the communication reliability of the CAN is reduced in this way, a method of directly energizing the reduced power supply voltage to the glow plug without transmitting a control signal from the ECU via the CAN is also conceivable. However, if such energization is continued, the life of the glow plug may be significantly impaired. In addition, since 100% energization is simultaneously performed on a plurality of glow plugs without control by the ECU, the load on the battery further increases, causing the battery to run out, and may not be able to start at all.

  Further, even when an abnormality occurs in one of the nodes connected to the CAN that is not related to the engine start due to a decrease in the power supply voltage, the communication of the entire CAN is cut off. May not be able to start.

  However, even in the cryogenic start, if the power supply to the glow plug and the starter can be maintained for a certain period or longer in a state controlled by the ECU, the engine start is completed and the power supply by the generator is started. Such a temporary voltage drop can be eliminated.

  Therefore, in view of such circumstances, the present invention reliably transmits a control signal from the electronic control unit to the control unit even when the power supply voltage is lowered to such a low voltage that the reliability of CAN communication cannot be maintained. It is an object of the present invention to provide a glow plug control device that enables stable energization control.

  According to the first aspect of the present invention, a limited capacity power source, a glow plug for heating the diesel combustion engine, a glow plug control device for controlling energization from the power source to the glow plug, and the operation of the diesel combustion engine A glow plug control device having an electronic control device for transmitting a control signal according to a situation, wherein the electronic control device and the glow plug control device are connected via a low voltage signal line.

  According to the first aspect of the present invention, the communication between the electronic control unit and the glow plug control unit is directly performed by the low voltage signal line, and the power source capacity is reduced by starting in a cryogenic environment. In the diesel combustion engine, even when an excessive load is generated on the power source due to large power consumption other than the glow plug, the power source is switched from the power source to the glow plug according to a control signal from the electronic control unit. Energization can be controlled by the glow plug control device. Therefore, the reliability of the glow plug control device is improved.

  More specifically, as in the invention of claim 2, the low-voltage signal line includes an output of a switching element provided on the electronic control device side and a first resistor provided on the glow plug control device side. And connect to the power source on the glow plug control device side.

  According to the invention of claim 2, when the switching element is opened and closed according to a control signal generated by the electronic control unit and the control signal is 1, that is, when the ON signal is issued from the electronic control unit, the switching element When the control signal is 0, that is, when an OFF signal is issued from the electronic control unit, the switching element is opened, and the output of the switching element is short-circuited to the ground. The output of the switching element is connected to the power supply voltage via the first resistor, and has substantially the same potential as the power supply. Therefore, the control signal generated by the electronic control device can be reliably transmitted to the glow plug control device side, although the potential is inverted between positive and negative. Therefore, it is possible to realize energization control from the power source to the flow plug by the glow plug control device according to a control signal from the electronic control device at all times, and the reliability of the glow plug control device is improved.

  Further, as in a third aspect of the present invention, the output voltage of the switching element is input to a differential amplifier circuit provided in the glow plug control device, and the power supply voltage is divided between the power supply and the ground. It is desirable to provide a resistor between the second resistor and the third resistor and input the potential between the second resistor and the third resistor as a threshold voltage to the differential amplifier circuit.

  According to the invention of claim 3, when the output voltage and the threshold voltage are compared by the differential amplifier circuit, even if the output voltage increases or decreases due to a change in the power supply voltage, the threshold voltage is The power supply voltage is divided by the second resistor and the third resistor, and the threshold voltage changes according to the change in the power supply voltage. Therefore, it is reliably determined whether the change in the output voltage is due to ON / OFF of the control signal or the change in the power supply voltage, and the output from the upper differential amplifier circuit and the control signal are completely separated. Can be matched.

  According to a fourth aspect of the present invention, the power source, the electronic control unit, and the glow plug control unit are connected to a multiplex communication circuit having a predetermined communication protocol to form a communication network. When the voltage drops below the voltage, information communication is performed between the electronic control unit and the glow plug control unit via the low voltage signal line. When the power source is higher than a predetermined voltage, the communication network It is good also as a structure which performs the information communication between the said electronic control apparatus and the said glow plug control apparatus via this.

  According to the invention of claim 4, the communication path between the electronic control device and the glow plug control device is selected according to the state of the power source, and the energization to the glow plug is controlled in a stable state at all times. This makes it possible to realize a glow plug control device with extremely high reliability.

  According to a fifth aspect of the present invention, the glow plug is a low-rated ceramic glow plug or a metal glow plug, and the glow plug control device includes a large-capacity switching element, and the large-capacity is controlled by an output from the differential amplifier circuit. Open and close the switching element.

  According to the fifth aspect of the present invention, when a low-rated glow plug excellent in quick warming is used, the glow plug control is performed according to the control signal from the electronic control device even if the power supply voltage is in an unstable state. Since the device can control the energization of the glow plug, it is possible to quickly raise the temperature of the glow plug while suppressing an excessive load on the power source, leading to stable ignition. it can. Therefore, a glow plug control device with extremely high reliability can be realized.

As an embodiment of the present invention, an outline when applied to a glow plug control device (hereinafter abbreviated as GCU) 3 for controlling energization to a glow plug (hereinafter abbreviated as GP) that assists ignition of a diesel engine (not shown) as an embodiment of the present invention. Will be described with reference to FIG.
In an internal combustion engine such as an automobile engine, a battery 1 having a limited capacity as a power source before starting the engine and a generator 100 as a power source after starting the engine are mounted, and the battery 1 is opened and closed by a start key 11, and a power control device. 10, the control voltage + B and the drive voltage BATT are controlled.

An electronic control device for engine control (hereinafter abbreviated as ECU) 2 includes an unillustrated voltage sensor, current sensor, water temperature sensor, crank angle sensor, rotational speed sensor, oxygen sensor, air-fuel ratio sensor, accelerator for detecting the state of the engine. Based on information from various sensors (hereinafter, abbreviated as SEN) such as an opening sensor, a combustion pressure sensor, a temperature sensor, a speed sensor, a knock sensor, etc., the state of the engine is detected, and the power supply device 10, starter (hereinafter abbreviated as STR). ), Control STR to control various actuators (hereinafter abbreviated as ACT) such as GP, fuel supply pump (not shown), fuel injection valve, intake throttle, intake valve, exhaust valve, swirl control valve, EGR valve, etc. starter driver _{(hereinafter,} abbreviated as _{D STR),} GCu3, sensor driver for controlling each SEN _{(hereinafter, D SE} Abbreviated), an actuator driver for driving the ACT (hereinafter, transmits a control signal to the abbreviated as D _ACT), and controls the operation of the engine.

  Of the SEN, a water temperature sensor, a crank angle sensor, etc. that can operate normally even under a low voltage are difficult to ensure the operation under a low voltage as a means for detecting the minimum necessary engine state under a low voltage. A path for directly connecting each sensor and the ECU 2 is provided separately from the feared CAN or not via the CAN, and the water temperature TW, the crank angle CA, and the like are input to the ECU 2.

Power supply 10, ECU 2, _GCu3, nodes that contain _{D STR (hereinafter,} abbreviated as _{N STR),} nodes that contain _{D ACT (hereinafter,} abbreviated as _{N ACT),} the node containing the _{D SEN (hereinafter,} abbreviated as _{N SEN)} is , A control area network (hereinafter abbreviated as CAN), a power supply device 10, an ECU 2, a GCU 3, and each node N _STR , N _ACT , N _SEN , a CAN driver (hereinafter, D _CAN) that controls access to _CAN. And information such as data frames and error frames are transmitted to each other according to a predetermined communication protocol via a CAN bus capable of high-speed multiplex communication. Termination resistor _{R E} is provided on the CAN bus.

Further, the ECU 2 and the GCU 3 are connected to each other via the low voltage signal line 23, which is a main part of the present invention, separately from the CAN, and information transmission between the ECU 2 and the GCU 3 under a low voltage is guaranteed. Yes. Below, the more concrete structure of ECU2, GCU3, and the signal line 23 for low voltages is demonstrated.
The ECU 2 includes an arithmetic circuit (hereinafter abbreviated as “CPU”) 20 that determines the operating state of the engine based on information transmitted from the SEN to the ECU 2 via the D _CAN and issues a control signal to each ACT, and a calculation result of the CPU 20 PWM signal circuit for generating a pulse width modulation (hereinafter abbreviated as PWM) control signal (hereinafter abbreviated as SI) for controlling the duty ratio of the pulse current supplied from BATT to GP in order to control the heat generation of GP in accordance with 21 and a switching element (hereinafter abbreviated as SW) 22 having an open collector or open drain function. SI consists of binary values of 0 and 1, and is connected to the base or gate of SW22 to control the opening and closing of SW22. Here, the signal communicated via the CAN bus also includes a signal having information equivalent to SI and is transmitted from the ECU 2 to the GCU 3.

The emitter or source of SW22 is grounded, the collector or drain is connected to the GCU3 side via the low voltage signal line 23, and is pulled to the battery voltage + B via the first resistor (hereinafter abbreviated as R1). Has been up.
When SI is 1, that is, when an ON signal is issued from the ECU 2, the SW 22 is in a conducting state, and the output of the SW 22 is short-circuited to the ground and becomes 0v.
On the other hand, when SI is 0, that is, when an OFF signal is issued from the ECU 2, the SW 22 is in an open state, and the output of the SW 22 is connected to + B through R 1 and has substantially the same potential as + B. Therefore, the SI generated in the ECU 2 is transmitted to the GCU 3 side as a potential with the positive and negative reversed.

Further, the output of the SW 22 is connected as an input voltage _{VIN to} an inverting input terminal (−) of a differential amplifier circuit (hereinafter abbreviated as CMP) 30 such as a comparator.
The non-inverting input terminal (+) of the CMP 30 has a threshold voltage (approximated by a second resistor and a third resistor (hereinafter abbreviated as R ₂ and R ₃ respectively) provided between + B and the ground (respectively). Hereinafter, _VREF is abbreviated. Further, as a driving voltage for the CMP 30, the high voltage side (V +) is connected to + B, and the low voltage side (V−) is connected to the ground.
The CMP 30 compares the level of V _IN that changes according to the opening / closing of the SW 22 with the level of V _REF that changes according to the increase / decrease of + B, and the result is a binary value of 0 and 1 and is output from the output terminal (hereinafter referred to as OUT). Is done.

The output from CMP30, that is, equal to the SI PWM signal glow plug drive circuit _{(hereinafter,} abbreviated as _{D GP)} is transmitted to, and opening and closing the switching element 32 such as a power MOSFET for controlling the opening and closing of a large current, the BATT Energization to a plurality of GPs provided for each cylinder is controlled. Note that, by setting R ₂ and R ₃ to the same resistance value, V _REF becomes ½ of + B, and a margin for variations and fluctuations can be taken.

The effects of the present invention will be described with reference to FIGS.
As shown in FIG. 4A, the start key 11 is turned on, the IG signal is turned on, and the engine starts. At this time, as shown in (b), an energization signal SI _GP is transmitted from the ECU 2 to the GP. Further, as shown in (c), the ECU 2 transmits an energization signal SISTR to the STR for a predetermined time t2 after a predetermined time t1 from the turning on of the IG, and cranking by the STR is started. At this time, since the inrush current of the STR is large, the load on the battery 1 is large and the battery voltage + B rapidly decreases as shown in (d). (E) is the enlarged schematic diagram, and + B shows a large change from 13.5V to 5.0V. At the same time, the ECU 2 also controls each ACT such as a fuel injection valve.

As shown in FIG. 3A, when a signal SI for performing PWM control as shown in FIG. 3B is transmitted from the ECU 2 when + B changes, the input voltage V transmitted to the GCU 3 via the SW22. _As shown in (c), _IN generates a potential opposite to ON and OFF of SI. At this time, the voltage of _VIN increases or decreases according to + B. Therefore, when comparing the reference potential and V _IN of the constant voltage, there is a possibility that reduction of V _IN due to the decrease in + B is misidentified as the output stop of V _IN. However, in the present embodiment, V _REF is a value obtained by dividing + B by a ratio of R ₂ and R ₃ + B · R ₃ / (R ₂ + R ₃ ), and as shown in (d), + B Will change accordingly. Therefore, the difference ΔV between VIN and VREF always coincides with the change in PWM as shown in (e), and as a result, the output OUT from the CMP 30 becomes the same signal as PWM as shown in (f). Further, as shown in (g), a predetermined PWM signal is sequentially sent from D _GP to a plurality of GP ₁ , GP ₂ , GP ₃ , GP _{4 in} accordance with the PWM signal SI transmitted from the ECU ₂ . . Note that the PWM signal changes the duty ratio r = d2 / d1 of the period d2 during which the energization is ON with respect to the pulse period d1 according to + B, thereby controlling the power supplied to the GP.
Therefore, according to the present invention, + B decreases due to a rapid change of + B accompanying the driving of STR or a decrease in electromotive force due to an increase in the internal resistance of the battery 1 in a low temperature environment, and the reliability of CAN is lost. Even in such a case, the PWM signal generated by the ECU 2 can be stably transmitted to the GCU 3, and the control of energization from the BATT to the GP is performed under conditions suitable for the operating state of the engine.

FIG. 4 shows an equivalent circuit for a more specific configuration example of the CPM 30 in the present embodiment. Keep this embodiment, CMP30 is composed of a differential amplifier circuit for amplifying the potential difference is compared with V _IN and V _REF, the output circuit section for outputting a result of the comparison.
Further, the connection portion of R ₁ and R _{2 to} the + B power supply may be connected to a 5V or 3.3V power supply capable of stable output even at a low voltage.

The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the spirit of the present invention.
For example, in the above embodiment, the signal communicated via the CAN bus includes a signal having information corresponding to SI, but the signal communicated via the CAN bus includes the signal equivalent to SI. The SI signal may be transmitted only through the low voltage signal line 23 without including a signal having information.
The SI may be transmitted via the low voltage signal line 23 only when the power supply voltage is low, or the SI may be transmitted constantly regardless of the power supply voltage level. When SI is always transmitted, the GCU side uses a signal having information equivalent to SI included in a signal communicated via the CAN bus according to the level of the power supply voltage or for low voltage The determination / control program may be configured to select whether to use SI transmitted via the signal line 23 and to use it for control.

Further, in the above embodiment, only the SI communicates between the ECU 2 and the GCU 3 via the low voltage signal line. However, the present invention is not limited to this. A plurality of types of signals such as installation, SI, engine speed signal, fuel injection amount signal, and power supply voltage signal may be transmitted from the ECU 2 to the GCU 3.
In addition, a diagnosis (self-diagnosis signal, hereinafter abbreviated as DI) is returned from the GCU 3 to the ECU 2. The DI is sent from the GCU 3 to the ECU 2 via at least one of the plurality of low voltage signal lines. The transmission may be configured, or the transmission may be performed to the ECU 2 through the CAN bus after the engine has been successfully started and the power supply from the generator 100 is started and stable + B is obtained.

  The present invention is particularly suitable for improving the reliability of a glow plug control device that controls energization of a low-rated glow plug excellent in quick warming regardless of whether it is made of ceramic or metal. This communication can be appropriately employed even when the communication is performed regardless of the CAN.

These are the block diagrams which show the outline | summary of the whole CAN containing the glow plug control apparatus and electronic control apparatus in the embodiment of this invention, and other nodes. FIG. 4 is a time chart showing the effect of the present invention together with FIG. 3. FIG. 3 is a time chart showing the effect of the present invention together with FIG. 2. These are equivalent circuit diagrams which show the specific structural example of the differential amplifier circuit in embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery 10 Power supply control apparatus 11 Start key 100 Generator 2 Electronic control apparatus (ECU)
20 Arithmetic circuit (CPU)
21 PWM signal circuit 22 Switching element SW
23 Low Voltage Signal Line 3 Glow Plug Control Unit (GCU)
30 Comparator (differential amplifier circuit)
31 GP drive circuit 32 Large capacity switching element ACT Various actuators + B Battery voltage BATT Drive voltage CAN Controller area network CA Crank angle D _ACT ACT driver D _CAN CAN driver D _SEN SEN driver DI Diagnosis (self-diagnosis signal)
GP glow plug R ₁ first resistor R ₂ second resistor R ₃ third resistor (threshold voltage application resistor)
SEN Various sensors STR Starter SI Control signal TW Water temperature

Claims (5)

A power source with a limited capacity, a glow plug for heating the diesel combustion engine, a glow plug control device for controlling energization from the power source to the glow plug, and a control signal corresponding to the operation status of the diesel combustion engine A glow plug control device having an electronic control device for transmitting,
A glow plug control device, wherein the electronic control device and the glow plug control device are connected via a low voltage signal line.   The low voltage signal line connects the output of the switching element provided on the electronic control device side to the first resistor provided on the glow plug control device side, and is connected to the power source on the glow plug control device side. The glow plug device according to claim 1, wherein:   An output voltage of the switching element is input to a differential amplifier circuit provided in the glow plug control device, and a second resistor and a third resistor are provided between the power source and the ground to apportion the power source voltage. 3. The glow plug control device according to claim 2, wherein a potential between the second resistor and the third resistor is input to the differential amplifier circuit as a threshold voltage.   The power supply, the electronic control device, and the glow plug control device are connected to a multiplex communication circuit having a predetermined communication protocol to form a network. When the power supply drops below a predetermined voltage, the low voltage Information communication is performed between the electronic control device and the glow plug control device via a signal line, and the electronic control device and the glow plug control device are connected via the network when the power source is at a predetermined voltage or higher. The glow plug control device according to any one of claims 1 to 3, wherein information communication is performed.   The glow plug is a low-rated ceramic glow plug or a metal glow plug, and the glow plug control device includes a large capacity switching element, and the large capacity switching element is opened and closed by an output from the differential amplifier circuit. The glow plug control device according to any one of claims 1 to 4, wherein:

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