JP6497275B2 - Electronic control unit - Google Patents

Description

  The present invention relates to an electronic control device for improving startability by heating a fuel before being introduced into an internal combustion engine.

  There are mixed fuels such as gasoline and ethanol, and FFV (flexible-fuel vehicle) using ethanol or methanol as fuel. Some internal combustion engines in FFV inject fuel into a cylinder after heating the fuel to some extent in order to ensure startability at low temperatures.

  As an example of fuel heating means, Patent Document 1 discloses a device in which a heater is provided in a fuel injection device and the fuel is heated by energizing the heater. However, if the heater is overheated and the temperature becomes too high, the fuel near the heater causes film boiling, which may reduce the heat transfer efficiency from the heater to the fuel.

  In order to solve this problem, a fuel injection sensor that includes a fuel temperature sensor that measures the temperature of the fuel and a current detection unit that measures the current value of the current flowing through the heater, and controls the current flowing through the heater by receiving feedback of the fuel temperature The device is known. According to this, the output of the heater can be reduced before the fuel near the heater causes film boiling. As a current detector for measuring the current flowing through the heater, a current detecting shunt resistor connected in series to a heater as a load is generally used as described in Patent Document 2.

JP 2005-113782 A JP-A-7-77546

  By the way, in order to appropriately adjust the output of the heater by feedback of the fuel temperature, a fuel temperature sensor is required. For this reason, a space for installing the fuel temperature sensor must be secured. In addition, since the fuel temperature is not always uniform in every part, there is a possibility that the fuel temperature (temperature near the heater) measured by the location where the fuel temperature sensor is installed cannot be obtained accurately.

  In general, since a relatively large current flows through the heater, if a current detection unit in which a shunt resistor is connected in series with the heater is employed, the allowable power of the shunt resistor needs to be set sufficiently large. Such a shunt resistor may cause an increase in size and cost.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an electronic control device capable of temperature feedback without using a fuel temperature sensor while realizing miniaturization.

  The invention disclosed herein employs the following technical means to achieve the above object. Note that the reference numerals in parentheses described in the claims and in this section indicate a corresponding relationship with specific means described in the embodiments described later as one aspect, and limit the technical scope of the invention. Not what you want.

In order to achieve the above object, the present invention is an electronic control device for controlling energization to heaters (HT1 to HT4) for heating fuel supplied to an internal combustion engine, and includes a first power supply (VB). Between the second power source (VC) and the heater, and between the heater drive circuit (11-14) having first switching elements (P1 to P4) that are interposed between the heater and the heater and turn on and off the heater. A second switching element (Q1 to Q4) connected in parallel to the first switching element with respect to the heater, and a current detection resistor (R1) connected in series to the second switching element and set to a predetermined resistance value A state detection circuit having a voltage detection unit (31 to 34) for detecting the voltage across the heater, and a current detection unit (40 for detecting the current value of the current flowing through the current detection resistor based on the voltage across the current detection resistor) )When A control unit (50) for controlling on / off of the first switching element and the second switching element, and the control unit controls the second switching element to be turned on in a period in which the first switching element is turned off, Based on the voltage across the heater and the current flowing through the current detection resistor, the temperature of the heater is estimated , a plurality of heater drive circuits are provided corresponding to the heater, and a plurality of state detection circuits are provided corresponding to the heater drive circuit, All of the plurality of state detection circuits share a single current detection resistor, and the control unit individually estimates the temperature of the heater by switching between the first switching element and the second switching element. .

  According to this, power can be supplied to the heater from the first power source by turning on the first switching element. Since the second switching element is turned on under the condition that the first switching element is off, a current supplied from the second power supply is allowed to flow through the heater independently of the first power supply. Can do. For this reason, only the current supplied from the second power source independent of the first power source, which is the power source for heating the heater, flows through the current detection resistor. The allowable power of the current detection resistor can be reduced by setting the output of the second power supply so that a smaller current flows in comparison with the first power supply having a relatively high output for heating the heater. Therefore, it is possible to reduce the size of the current detection resistor and hence the electronic control device.

  In addition, in the state where the second switching element is turned on, the current flowing through the heater and the voltage across the heater can be detected by the current detection unit and the voltage detection unit, respectively, so that the predetermined temperature at the predetermined temperature and the heater at the temperature can be detected. The heater temperature can be estimated based on the resistance value, the resistance temperature coefficient, the detected current flowing through the heater, and the voltage across the heater. The controller can control the amount of current flowing through the heater based on the estimated heater temperature. That is, it is possible to feed back to the amount of current flowing through the heater based on the estimated heater temperature without using a fuel temperature sensor that has been necessary in the past.

It is a circuit diagram which shows schematic structure of the electronic controller and heater in 1st Embodiment. It is a timing chart which shows the control flow of an electronic controller.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same reference numerals are given to the same or equivalent parts.

(First embodiment)
First, a schematic configuration of the electronic control device according to the present embodiment will be described with reference to FIG.

  The electronic control device in the present embodiment controls energization to a heater for preheating the fuel in an FFV that uses a mixed fuel such as gasoline and ethanol, or ethanol or methanol as fuel. In particular, an example of an electronic control device that controls four heaters in parallel will be described below. The number of heaters is an example, and is not limited to four.

  As shown in FIG. 1, the electronic control unit 100 controls energization to the four heaters HT1 to HT4. The heaters HT1 to HT4 are arranged in a fuel passage in the internal combustion engine, and raise the temperature of the fuel before being sprayed to the cylinder to a predetermined temperature. In the present embodiment, the heaters HT1 to HT4 are of a heating wire type that releases an amount of heat proportional to the internal resistance of each of the heaters HT1 to HT4 when energized. As a result, the fuel is sprayed into the cylinder in a state where the temperature is raised to a temperature at which ignition is possible or ignition is possible under conditions with better combustion efficiency. One end of each of the heaters HT1 to HT4 is grounded, and the battery voltage VB is applied to the other end. In other words, the four heaters HT1 to HT4 are connected in parallel to the battery.

  The electronic control device 100 controls the energization to the heaters HT1 to HT4, the four heater drive circuits 11 to 14, the four state detection circuits 21 to 24, the four voltage detection units 31 to 34, the current A detection unit 40 and a control unit 50 are provided.

  The heater drive circuits 11 to 14 are switch circuits that control ON / OFF of energization to the heaters HT1 to HT4, respectively. The heater drive circuit 11 mediates the battery voltage VB and the heater HT1, the heater drive circuit 12 mediates the battery voltage VB and the heater HT2, the heater drive circuit 13 mediates the battery voltage VB and the heater HT3, and the heater drive circuit 14 It mediates battery voltage VB and heater HT4. The power source that generates the battery voltage VB corresponds to the first power source in the claims.

  Since the four heater drive circuits are equivalent to each other, the heater drive circuit 11 will be specifically described as a representative. The heater drive circuit 11 has a reverse conducting MOS transistor P1 as a switching element. The transistor P1 has a gate electrode connected to a terminal GH1 in the control unit 50 described later, and is turned on when a High signal is input from the terminal GH1. When the transistor P1 is turned on, the battery voltage VB is applied to the heater HT1, and the temperature of the heater HT1 rises.

  The same applies to the remaining heater driving circuits 12 to 14, which have transistors P2 to P4, respectively, and the gate electrodes are connected to the terminals GH2 to GH4. The first switching element in the claims corresponds to the transistors P1 to P4.

  The state detection circuits 21 to 24 are circuits that supply current to the heaters HT1 to HT4, respectively, in order to detect the states of the heaters HT1 to HT4. Here, the state is the current flowing through the heaters HT1 to HT4, the voltage across the heaters HT1 to HT4, and the temperature of the heaters HT1 to HT4 estimated from the current and voltage. The state detection circuit 21 mediates the reference voltage VC and the heater HT1, the state detection circuit 22 mediates the reference voltage VC and the heater HT2, the state detection circuit 23 mediates the reference voltage VC and the heater HT3, and the state detection circuit 24 It mediates the reference voltage VC and the heater HT4. The power source that generates the reference voltage VC corresponds to the second power source in the claims.

  Since the four state detection circuits are equivalent to each other, the state detection circuit 21 will be specifically described as a representative. As shown in FIG. 1, the state detection circuit 21 and the heater drive circuit 11 are connected in parallel when viewed from the heater HT1. The state detection circuit 21 has a reverse conducting MOS transistor Q1 as a switching element and a shunt resistor R1 as a current detection resistor. The shunt resistor R1 and the MOS transistor Q1 are connected in series between the reference voltage VC and the heater HT1. In this embodiment, the shunt resistor R1 is connected to the high side with respect to the MOS transistor Q1, that is, the side close to the reference voltage VC. The transistor Q1 has a gate electrode connected to a terminal GV1 in the control unit 50 described later, and is turned on when a High signal is input from the terminal GV1. When the transistor Q1 is turned on, the reference voltage VC is applied to the heater HT1, and a current flows from the reference voltage VC to the ground (GND) via the heater HT1.

  In addition, a diode 61 is provided between the state detection circuit 21 and the heater drive circuit 11 in the forward direction from the state detection circuit 21 toward the heater drive circuit 11 as shown in FIG. The diode 61 prevents a current from flowing backward from the heater drive circuit 11 toward the state detection circuit 21.

  The same applies to the remaining state detection circuits 22 to 24, which have transistors Q2 to Q4 and current detection resistors, respectively, and the gate electrodes of the transistors Q2 to Q4 are connected to terminals GV2 to GV4, respectively. Further, between the state detection circuits 22 to 24 and the heater drive circuits 12 to 14, diodes 62 to 64 are provided in the forward direction from the state detection circuits 22 to 24 toward the heater drive circuits 12 to 14. .

  The second switching element in the claims corresponds to the transistors Q1 to Q4. In the present embodiment, the state detection circuits 21 to 24 share the shunt resistor R1 as a current detection resistor. That is, as shown in FIG. 1, the transistors Q1 to Q4 are connected in parallel to each other with respect to the shunt resistor R1.

  The reference voltage VC is preferably sufficiently smaller than the battery voltage VB.

  The voltage detectors 31 to 34 are circuits for detecting the voltages at both ends of the heaters HT1 to HT4, respectively. Since the four voltage detection units are equivalent to each other, the voltage detection unit 31 will be specifically described as a representative.

  The voltage detector 31 is a circuit including a generally known differential amplifier circuit and an A / D converter. The voltage detection unit 31 receives the high-side and low-side voltages of the heater HT1 and differentially amplifies them, and then the amplified potential difference is A / D converted. The voltage detector 31 outputs the voltage across the heater HT1 to the terminal V1 of the controller 50 described later. Hereinafter, the voltage across the heater HT1 detected by the voltage detector 31 may be indicated as φV1.

  The same applies to the remaining voltage detection units 32 to 34, and both-end voltages φV 2 to φV 4 of the heaters HT 2 to HT 4 are respectively output to the terminals V 2 to V 4 of the control unit 50.

  The current detection unit 40 is a circuit for detecting a current flowing through the shunt resistor R1, which is a current detection resistor shared by the state detection circuits 21 to 24. Specifically, the current detection unit 40 is a circuit including a generally known differential amplifier circuit and an A / D converter. The current detection unit 40 receives the high side voltage and the low side voltage of the shunt resistor R1 and differentially amplifies them, and the amplified potential difference is A / D converted. The resistance value of the shunt resistor R1 is defined in advance, and the current value of the current flowing through the shunt resistor R1 is calculated from the measured voltage across the shunt resistor R1 and the resistance value of the shunt resistor R1. The calculation for obtaining the current may be a configuration in which the current detection unit 40 includes a calculation unit, or a configuration in which the control unit 50 includes a calculation unit. In the present embodiment, the current detection unit 40 has a calculation unit, and the current value of the current flowing through the shunt resistor R <b> 1 is output to the terminal C of the control unit 50. In the present embodiment, since the current detection resistors are shared by the four state detection circuits 21 to 24 and there is one shunt resistor R1, there is one current detection unit 40 corresponding to the number of shunt resistors R1. is there.

  The controller 50 applies a predetermined gate voltage to the transistors P1 to P4 included in the heater drive circuits 11 to 14 and the gate electrodes of the transistors Q1 to Q4 included in the state detection circuits 21 to 24 to turn on / off each transistor. Is controlling. In addition, to the control unit 50, the voltages φV1 to φV4 of the heaters HT1 to HT4 detected by the voltage detection units 31 to 34 are input to the terminals V1 to V4, respectively. Further, the current value of the current flowing through the shunt resistor R <b> 1 detected by the current detection unit 40 is input to the terminal C in the control unit 50.

The control unit 50 includes a temperature estimation unit that estimates the temperatures of the heaters HT1 to HT4 based on the voltage V input to the terminals V1 to V4 and the current I input to the terminal C. The temperature estimation unit stores in advance a reference resistance value R ₀ and a resistance temperature coefficient α at the heater reference temperature T ₀ , and calculates the temperatures of the heaters HT1 to HT4 as described below.

First, the temperature estimation unit in the control unit 50 calculates the resistance value R of the heater at the temperature T based on the current I and the voltage V at the temperature T to be estimated by the heater. Next, the heater temperature T is calculated based on the equation T = (R / R ₀ −1) / α + T ₀ . Note that the temperature estimation unit may be configured by an analog circuit or a digital circuit.

  Based on the estimated heater temperature T, the control unit 50 determines the duty ratio of pulses applied to the gate electrodes of the transistors P1 to P4 in the heater drive circuits 11 to 14. For example, if the temperature of the heaters HT1 to HT4 is lower than the boiling point of the fuel, the duty ratio is increased, and if the temperature is higher than the boiling point of the fuel, the duty ratio is decreased. Since the fuel existing in the vicinity of the heaters HT1 to HT4 is maintained at a temperature not exceeding the boiling point, the fuel can be heated without causing film boiling around the heaters HT1 to HT4.

  Next, with reference to FIG. 2, estimation and control of the temperature of the heaters HT <b> 1 to HT <b> 4 by the electronic control device 100 according to this embodiment will be described.

  The control unit 50 outputs high signals (hereinafter simply referred to as H) to the gate electrodes of the transistors P1 to P4, thereby turning on the transistors P1 to P4, respectively, and a low signal (hereinafter simply referred to as L). By outputting, the transistors P1 to P4 are turned off. The control unit 50 outputs H to the gate electrodes of the transistors Q1 to Q4 to turn on the transistors Q1 to Q4, and outputs L to turn off the transistors Q1 to Q4.

  The control unit 50 performs PWM control so that H and L are periodically applied to the transistors P1 to P4 and Q1 to Q4 for a predetermined time. Regarding the transistors P1 to P4 belonging to the heater drive circuits 11 to 14, the longer the period of High, the longer the energization time to the heaters HT1 to HT4, and thus the temperature becomes higher.

  The control unit 50 in the present embodiment performs control so that two or more of the transistors P1 to P4 belonging to the heater drive circuits 11 to 14 cannot be turned off at the same time. Further, the transistors Q1 to Q4 belonging to the state detection circuits 21 to 24 are controlled so as to be turned on only during a period in which the transistors P1 to P4 are off.

  An example of the control flow of the electronic control apparatus 100 in this embodiment will be described. As shown in FIG. 2, from the state where the terminals GH1 to GH4 output H, that is, the state where all of the transistors P1 to P4 belonging to the heater driving circuits 11 to 14 are turned on, the terminal GH1 at any time t1. Transition from H to L. At almost the same time, the signal at the terminal GV1 changes from L to H. As a result, the voltage connected to the heater HT1 is switched from the battery voltage VB through which the current for heating is supplied to the reference voltage VC for detecting the state. At this time, the control unit 50 obtains the voltage φV1 across the heater HT1 and the current value of the current flowing through the shunt resistor R1 from the voltage detection unit 31.

At this time, the current flowing through the shunt resistor R1 is equal to the current flowing through the heater HT1. The both-ends voltage φV1 and current I of the heater HT1 acquired here are values reflecting the temperature of the heater HT1 at time t1. The temperature estimation unit in the control unit 50 calculates the temperature T1 of the heater HT1 based on the equation T = (R / R ₀ −1) / α + T ₀ .

  The controller 50 determines a duty ratio for driving the transistor P1 based on the estimated temperature T1. That is, in the PWM control after the time point when the temperature T1 is estimated, the duty ratio is changed so that the temperature of the heater HT1 does not exceed the boiling point of the fuel.

  Since VB> VC, when the power source connected to the heater HT1 is switched from the battery voltage VB to the reference voltage VC, a current may flow from the heater drive circuits 12-14 toward the state detection circuits 21-24. However, in this embodiment, the diodes 62 to 64 prevent this.

  Next, at time t2, the signal at the terminal GV1 transitions from H to L, and the signal at the terminal GH1 transitions from L to H almost simultaneously. As a result, the voltage connected to the heater HT1 is switched from the reference voltage VC for state detection to the battery voltage VB through which a heating current flows, and the heater HT1 resumes heat generation.

  Next, at time t3, the signal at the terminal GH2 changes from H to L, and the signal at the terminal GV2 changes from L to H almost simultaneously. As a result, the voltage connected to the heater HT2 is switched from the battery voltage VB through which the current for heating is supplied to the reference voltage VC for detecting the state. Similar to the time t1 to the time t2, the control unit 50 calculates the temperature T2 of the heater HT2 based on the both-ends voltage φV2 of the heater HT2 and the current I reflecting the temperature of the heater HT2 at the time t3.

  The controller 50 determines a duty ratio for driving the transistor P2 based on the estimated temperature T2. That is, in the PWM control after the time point when the temperature T2 is estimated, the duty ratio is changed so that the temperature of the heater HT2 does not exceed the boiling point of the fuel.

  Thereafter, similarly, control unit 50 estimates temperature T3 of heater HT3 from time t5 to time t6, and estimates temperature T4 of heater HT4 from time t7 to time t8. The controller 50 determines a duty ratio for driving the transistors P3 and P4 based on the estimated temperatures T3 and T4. That is, in the PWM control after the time when the temperatures T3 and T4 are estimated, the duty ratio is changed so that the temperature of the heaters HT3 and HT4 does not exceed the boiling point of the fuel.

  Next, the effect by employ | adopting the electronic control apparatus 100 which concerns on this embodiment is demonstrated.

  The electronic control device 100 described above can supply power from the battery voltage VB to the corresponding heaters HT1 to HT4 by turning on the transistors P1 to P4 belonging to the heater driving circuits 11 to 14, respectively. Then, under the condition that any of the transistors P1 to P4 is off, the transistor corresponding to the turned off transistor among the transistors Q1 to Q4 belonging to the state detection circuits 21 to 24 is turned on. A current supplied from the reference voltage VC can flow through the heater independently of the battery voltage VB. For this reason, only the current supplied from the reference voltage VC for state detection can flow through the shunt resistor R1.

  In the conventional configuration, since the shunt resistor is connected in series between the battery voltage and the heater, a sufficient allowable power is required for the output of the battery voltage VB. On the other hand, the current supplied from the reference voltage VC can flow through the shunt resistor R1 of the electronic control device 100 in this embodiment independently of the battery voltage VB. The allowable power of the shunt resistor R1 can be reduced by setting the output of the reference voltage VC so that a current smaller than the battery voltage VB, which is a relatively high output for heating the heater, flows. Therefore, the shunt resistor R1 can be downsized, and thus the electronic control device can be downsized.

In addition, when any of the transistors Q1 to Q4 belonging to the state detection circuits 21 to 24 is turned on, the current I flowing through the heater by the current detection unit 40 and the voltage detection units 31 to 34 and the voltage V across the heater are respectively Therefore, based on a predetermined reference temperature T ₀ determined in advance, the resistance value R ₀ of the heater at the temperature, the resistance temperature coefficient α, the detected current I flowing through the heater, and the voltage V across the heater. The temperature T of the heater can be estimated. The controller 50 can control the amount of current flowing through the heater based on the estimated heater temperature T. That is, it is possible to feed back to the amount of current flowing through the heater based on the estimated heater temperature T without using a fuel temperature sensor which has been conventionally required.

  In the present embodiment, the heater driving circuit 11 and the state detection circuit 21 corresponding to the heater HT1, the heater driving circuit 12 and the state detection circuit 22 corresponding to the heater HT2, and the heater driving circuit 13 and the state detection circuit corresponding to the heater HT3. 23, a heater driving circuit 14 and a state detection circuit 24 corresponding to the heater HT4 are connected in parallel to the battery voltage VB and the reference voltage VC. For this reason, about the some heater HT1-HT4, the heating of heater HT1-HT4 and temperature estimation can be performed independently. And since the electronic control apparatus 100 is equipped with the diodes 61-64 which interrupt | block the inflow of the electric current from the heater drive circuits 11-14 to the state detection circuits 21-24, in the period which estimates the temperature of one heater, Inflow of current from the heater drive circuits 11 to 14 to the state detection circuits 21 to 24 can be prevented.

  Furthermore, in this embodiment, as shown in FIG. 2, the transistors Q1 to Q4 belonging to the state detection circuits 21 to 24 do not turn on at the same time. Therefore, when the shunt resistor R1 is arranged closer to the reference voltage VC than the transistors Q1 to Q4 as in the present embodiment, the state detection circuits 21 to 24 connect one shunt resistor R1 to the current detection resistor. As a shared configuration. Accordingly, the number of current detection resistors can be reduced, and the number of current detection units 40 can be reduced in accordance with the number of current detection resistors.

(Other embodiments)
The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

  In the above-described embodiment, the configuration in which the shunt resistor R1 as the current detection resistor is shared by the four state detection circuits 21 to 24 has been described. However, the configuration in which the shunt resistor is provided for each of the state detection circuits 21 to 24. It may be.

  Moreover, although the example which employ | adopts reverse conducting MOS transistors P1-P4, Q1-Q4 was demonstrated as a 1st switching element and a 2nd switching element, the kind of switching element is not limited. For example, for example, bipolar transistors can be adopted as the first switching element and the second switching element.

DESCRIPTION OF SYMBOLS 11-14 ... Heater drive circuit, 21-24 ... State detection circuit, 31-34 ... Voltage detection part, 40 ... Current detection part, 50 ... Control part, 61-64 ... Diode, P1-P4 ... Transistor (1st switching) Element), Q1-Q4 ... transistor (second switching element), HT1-HT4 ... heater

Claims (4)

An electronic control device for controlling energization to a plurality of heaters (HT1 to HT4) for heating fuel supplied to an internal combustion engine,
Heater driving circuits (11 to 14) having first switching elements (P1 to P4) interposed between a first power supply (VB) and the heater to turn on and off the energization of the heater;
A second switching element (Q1 to Q4) interposed between a second power source (VC) and the heater and connected in parallel to the first switching element with respect to the heater, and in series with the second switching element A state detection circuit (21-24) having a current detection resistor (R1) connected to and set to a predetermined resistance value;
A voltage detector (31-34) for detecting the voltage across the heater;
A current detector (40) for detecting a current value of a current flowing through the current detection resistor based on a voltage across the current detection resistor;
A control unit (50) for controlling on / off of the first switching element and the second switching element,
The controller controls to turn on the second switching element during a period in which the first switching element is turned off, and based on the voltage across the heater and the current flowing through the current detection resistor, the temperature of the heater to estimate,
A plurality of heater drive circuits are provided corresponding to the heaters, and a plurality of the state detection circuits are provided corresponding to the heater drive circuits,
All of the plurality of state detection circuits share a single current detection resistor,
The said control part estimates the temperature of the said heater separately by switching of the said 1st switching element and the said 2nd switching element, The electronic control apparatus characterized by the above-mentioned . The control unit controls a plurality of first switching elements to be sequentially turned off, and controls the same number of second switching elements as the first switching elements to be turned on in a corresponding off period of the first switching elements. Item 2. The electronic control device according to Item 1. The electronic control device according to claim 1 or 2 , further comprising a diode (61 to 64) that blocks inflow of current from the heater drive circuit to the state detection circuit. The electronic control device according to claim 1 , wherein the current detection resistor is connected to the second power supply side with respect to the second switching element.

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