JP2015135069A - Heater and heater element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heater capable of highly accurately measuring a resistance value of part of a heater element 40 to accurately estimate a resistance value of the entire heater element 40, and considerably reducing power consumption at a time of measuring the resistance value.SOLUTION: A heater comprises: a heater element 40 that includes a first heater 40a and a second heater 40b connected in series between a drive terminal 40c and a ground terminal 40d; a first power supply Bat selectively connected to the drive terminal 40c; a second power supply Bec selectively connected to a test terminal 40e provided between the first heater 40a and the second heater 40b; and a current detection circuit 31 connected in series to the heater element 40, the heater estimating a value of an electric resistance of the heater 40 on the basis of an output from the current detection circuit 31 at a time of connecting the test terminal 40e to the second power supply Bec and driving the heater element 40 on the basis of this estimated value.

Description

  The present invention relates to a heating device for heating fuel and a heater element used in the heating device.

  Some internal combustion engines that inject fuel using a fuel injection valve warm the fuel supplied to the fuel injection valve in order to enable a smooth start even at low temperatures. Therefore, a heating device is known in which a heater is provided in a fuel supply pipe so that fuel heated by the heater is supplied to a fuel injection valve.

  An example of such a heating device is a fuel injection system comprising at least one fuel injection device and a heatable adapter, wherein the adapter is connected to a fuel rail and a fuel injection valve of the fuel injection system. A fuel injection system is disclosed in which a thermo switch is provided in a fuel rail, and the thermo switch is connected to a device that forms an external contact and a heatable adapter (Patent Document 1). . According to Patent Document 1, complete combustion of the fuel is guaranteed by heating the fuel with the heating element based on the temperature of the fuel rail detected by the thermoswitch.

  As another example, the procedure for determining whether or not the engine can be started based on the alcohol concentration of the fuel, and when it is determined that the engine cannot be started in this determination procedure, energization of the starter motor is prohibited and fuel injection is performed. And a procedure for energizing the heater for vaporizing the fuel, a procedure for energizing the heater according to the energizing procedure, and determining the completion of heating of the heater based on the consumption current of the heater after a predetermined time has elapsed, There is disclosed a start control method for an engine for an FFV (Flexible Fuel Vehicle) engine including a procedure for energizing a starter motor and permitting fuel injection when it is determined that heating is completed in a procedure for determining heating completion of a heater ( Patent Document 2). According to Patent Document 2, it is determined that the heating completion of the heater is determined based on the consumption current of the heater after a predetermined time has passed since the heater is energized, thereby preventing an erroneous determination of the heater heating completion.

Special table 2009-503352 gazette JP-A-4-231666

  However, in the technique disclosed in Patent Document 1, since the fuel rail has a relatively large heat capacity, a delay occurs until the heat of the adapter provided with the heating element is transmitted to the thermo switch via the fuel rail. There exists a subject that the precision of heating control falls. Further, although Patent Document 1 includes a plurality of fuel injection devices, the thermoswitch is shared, and there is a problem that temperature management of the fuel supplied to each fuel injection device cannot be appropriately performed.

  Further, in the technique disclosed in Patent Document 2, although there is a procedure for determining whether or not the engine can be started based on the alcohol concentration of the fuel, it is already warmed up and the engine can be started immediately. Even if it exists, electricity supply to a heater will be performed over a predetermined period, and there exists a subject that power consumption becomes large. In order to reduce power consumption, a configuration is also considered in which the current consumption (or resistance value) of the heater is measured at the initial stage of energization performed for a predetermined period, and the energization period for the heater is determined according to the measured current consumption. It is done. In this way, power consumption can be reduced by providing a preliminary energization period for measuring current consumption. However, measuring current consumption is nothing but heating the heater, and the measurement itself consumes power. Therefore, there is a limit to reducing power consumption.

  The present invention has been devised to solve such problems of the prior art, and its main purpose is to measure the resistance value of a part of the heater element with high accuracy and to determine the resistance value of the entire heater element. It is an object of the present invention to provide a heating device and a heater element capable of accurately estimating the power consumption and reducing the power consumption when measuring the resistance value.

  The present invention made to solve the above-described problems includes a first heater portion (40a) and a second heater portion (40b) connected in series between the drive terminal (40c) and the ground terminal (40d). Select a heater element (40), a first power supply (Bat) connected to the drive terminal at a predetermined timing, and a test terminal (40e) provided between the first heater part and the second heater part. A second power supply (Bec) connected in series, a current detection circuit (31) connected in series to the heater element, and an output of the current detection circuit when the test terminal is connected to the second power supply A heating unit including a control unit (23a) for estimating a value of an electric resistance of the heater element based on the estimated value and connecting the drive terminal to the first power source based on the estimated value to control an energization amount of the heater element. It is the location.

  Accordingly, a large current is passed through the second heater portion that is a part of the heater element to measure the resistance value of the second heater portion with high accuracy, thereby accurately estimating the resistance value of the entire heater element and the heater. By measuring the resistance value of the second heater portion which is a part of the element, it is possible to greatly reduce the power consumption during the measurement.

  In the present invention, the value of the electric resistance of the second heater portion (40b) is set to be equal to or less than the value of the electric resistance of the first heater portion (40a).

  As a result, when the value of the electric resistance of the second heater portion is measured, it is possible to measure the electric resistance value with high accuracy by flowing a current only through the second heater portion having a lower resistance.

  In the present invention, the voltage of the second power source (Bec) is set lower than the voltage of the first power source (Bat).

  As a result, when measuring the value of the electrical resistance of the second heater portion, it is possible to reduce power consumption by using a lower voltage second power source.

In the present invention, the electric resistance value of the first heater portion (40a) is R1, the electric resistance value of the second heater portion (40b) is R2, and the power supply voltage of the first power source (Bat) is V1. When the power supply voltage of the second power source (Bec) is V2 and the resistance ratio α = R2 / (R1 + R2), the resistance ratio α is set in a range of V2 ² / V1 ² <α <V2 / V1. It is what.

  As a result, compared with the case where the entire heater element is energized, the current flowing through the second heater portion is increased when measuring the value of the electrical resistance of the second heater portion to improve the measurement accuracy, and at the time of measurement. It becomes possible to reduce power consumption.

  In the present invention, the heater element (40) is mounted on the internal combustion engine (E), and the control unit (23a) measures the output of the current detection circuit (31) when the internal combustion engine is warmed up. The electric resistance value of the heater element is estimated based on the measurement result, and the drive terminal (40c) is connected to the first power source (Bat) based on the estimated electric resistance value when the internal combustion engine is cold. The length of the period to connect to is determined.

  Thus, since the time for heating the fuel at the time of cooling is determined based on the data acquired at the time of warming up, it is possible to shorten the time until the internal combustion engine can be started at the time of cooling.

  In the present invention, the heater element (40) is provided in each of a plurality of cylinders of the internal combustion engine (E), and heats fuel supplied to the cylinders.

  As a result, even if the temperatures of the cylinders are different, the total power consumption can be reduced by heating the fuel for an optimum time for each cylinder.

  The present invention also provides a heater element (40) composed of a first heater part (40a) and a second heater part (40b) connected in series with each other, and the first heater part (40a) is driven when the heater element is driven. A drive terminal (40c) connected to one power supply (Bat) and a second power supply (40c) connected between the first heater portion and the second heater portion when estimating the electric resistance value of the heater element. Bec) and a test element (40e) connected to the heater element.

  As a result, the resistance value of the entire heater element is accurately measured by flowing a large current through the drive terminal to the second heater part, which is a part of the heater element, and measuring the resistance value of the second heater part with high accuracy. Estimate and measure the resistance value of the second heater part, which is a part of the heater element, using the test terminal, which can greatly reduce the power consumption when estimating the total resistance value of the heater element. It becomes.

  As described above, according to the present invention, the resistance value of the entire heater element is accurately measured by flowing a large current through the second heater part which is a part of the heater element and measuring the resistance value of the second heater part with high accuracy. In addition, by measuring the resistance value of the second heater portion that is a part of the heater element, it is possible to significantly reduce the power consumption during the measurement.

Overall schematic diagram of a fuel supply device equipped with a heating device according to the present embodiment The perspective view which shows the structure of a fuel heating unit Block diagram showing functions of ECU Block diagram showing the electrical configuration of the heating device Explanatory drawing explaining the processing content by the calculation / control part provided in the fuel heating control part Explanatory drawing explaining the setting of the resistance ratio α of the heater element (A) is explanatory drawing which shows the 1st starting mode of an internal combustion engine, (b) is explanatory drawing which shows the 2nd starting mode of an internal combustion engine.

  Hereinafter, a heating device 7 according to the present invention will be described in detail with reference to an embodiment shown in the accompanying drawings. In the following description, the terms upstream and downstream are not based on the actual fuel flow direction, but are determined based on the upstream and downstream of the fuel supply system from the fuel tank 2 to the fuel injection valve 4.

  FIG. 1 is an overall schematic diagram of a fuel supply device 1 equipped with a heating device 7 according to the present embodiment. As shown in FIG. 1, the fuel supply device 1 is provided for an in-line four-cylinder FFV engine (hereinafter referred to as “internal combustion engine E”) that uses ethanol fuel or a mixed fuel of gasoline and ethanol. The fuel stored in the tank 2 is supplied to four fuel injection valves 4 provided for each cylinder S. The fuel supply device 1 is provided for each fuel injection valve 4 on the downstream side of the fuel pump 6 and the fuel pump 6 provided at the upstream end of the fuel supply path 5 connecting the fuel tank 2 and the fuel injection valve 4. , And four fuel heating sections 14 for heating the fuel, respectively.

  The fuel pump 6 is provided in the fuel tank 2, pumps fuel stored in the fuel tank 2 through a strainer (not shown), and pumps the fuel toward the fuel injection valve 4. Although detailed illustration is omitted, the automobile is provided with an ignition switch 35 (see FIG. 3), and when the operator operates the ignition switch 35 to an ignition position (hereinafter referred to as “IG position”). The fuel pump 6 is driven to pump fuel with a predetermined pressure.

  The four fuel heating units 14 and the four fuel injection valves 4 are integrated with the fuel case 17 by the base plate 19 to constitute one fuel heating unit 3. A fuel case 17 is located at the upstream end of the fuel supply system in the fuel heating unit 3, and the fuel supply path 5 is connected to the fuel case 17.

  FIG. 2 is a perspective view showing the configuration of the fuel heating unit 3. As shown in FIG. 2, the fuel heating unit 3 is connected to a fuel supply pipe 18, a fuel case 17 connected to the downstream end of the fuel supply pipe 18, and four outlets formed in the fuel case 17. The fuel heating unit 14 and the fuel injection valve 4 connected to the downstream side of the fuel heating unit 14 via the base plate 19 are provided.

  The fuel case 17 stores fuel therein and distributes the fuel to each fuel heating unit 14 from the four outlets with equal pressure. The fuel heating unit 14 includes a heater housing 15 that defines a heating chamber and constitutes the fuel supply path 5, and a heater element 40 (see FIG. 4) on the tip side, and the heater element 40 is accommodated in the heating chamber. In this manner, the fuel is inserted into the heater housing 15, and energization of the heater element 40 is controlled by an ECU (Electric Control Unit) 20 (see FIG. 3) to appropriately heat the fuel in the heating chamber.

  The fuel injection valve 4 incorporates an electromagnetic valve that is driven and controlled by the ECU 20, and injects a predetermined amount of fuel toward the combustion chamber of the internal combustion engine E (see FIG. 1) at a predetermined time by opening and closing the electromagnetic valve. In addition, by constituting the fuel heating unit 3 in which all the fuel heating units 14 and the fuel injection valves 4 are integrated by the base plate 19, the assembly to the internal combustion engine E is facilitated, and the fuel for the internal combustion engine E is provided. The assembly accuracy of the injection valve 4 can be increased.

  Although not shown in detail, the internal combustion engine E is provided with a starter motor 28 (see FIG. 3) that rotationally drives the crankshaft when starting. The starter motor 28 is also energized by the ECU 20. The start operation of the internal combustion engine E is performed by a method in which the ignition switch 35 is further rotated from the IG position to the start position with a key. Further, in the internal combustion engine E of the present embodiment, as will be described later, when the ignition switch 35 is operated to the IG position, the fuel heating unit 14 starts heating the fuel.

  FIG. 3 is a block diagram showing functions of the ECU 20. Hereinafter, the ECU 20 that controls the fuel supply device 1 will be described with reference to FIG. 3. The ECU 20 includes a water temperature sensor 32 for detecting the cooling water temperature TW of the internal combustion engine E, a LAF sensor 34 for detecting the residual concentration of ethanol contained in the exhaust gas and grasping the ethanol concentration contained in the fuel, fuel heating Based on the input signal 21 to which the detection signal from the current detection circuit 31 and the like for measuring the value of the current flowing through the heater element 40 provided in the unit 14 and the status signal of the ignition switch 35 are input, and the signals from the respective sensors, etc. A fuel injection valve control unit 24 for driving and controlling the fuel injection valve 4, a fuel pump control unit 22 for driving and controlling the fuel pump 6, a fuel heating control unit 23 for driving and controlling the heater element 40, and a starter motor 28. A starter motor control unit 25 that controls driving and an output interface 27 are provided.

  FIG. 4 is a block diagram showing an electrical configuration of the heating device 7, and FIG. 5 is an explanatory diagram for explaining processing contents by the calculation / control unit 23 a provided in the fuel heating control unit 23. In FIG. 4, only one fuel heating unit 14 included in the fuel heating unit 3 is illustrated for the sake of simplicity. Further, the arrows shown in FIG. 5 indicate the access directions with respect to the respective elements when viewed from the calculation / control unit 23a, and the arrows directed to the calculation / control unit 23a indicate the read operation of the calculation / control unit 23a, the calculation / control An arrow from the control unit 23a indicates a write operation.

  As shown in FIG. 4, the heating device 7 includes a fuel heating control unit 23, a fuel heating unit 3, and a current detection circuit 31. The fuel heating control unit 23 is provided in the ECU 20, and includes an arithmetic / control unit 23a that functions as a substantial control unit, a first switch 23c, a second switch 23d, and a storage unit 23e. The arithmetic / control unit 23a includes a CPU (Central Processing Unit) (not shown). The CPU is coupled to a ROM (Read Only Memory) and a RAM (Random Access Memory) (not shown) via a system bus 23f and stored in the ROM. It operates based on the program. Of course, the arithmetic / control unit 23a may include other hardware logic circuits, or may be configured to be shared with the fuel pump control unit 22 (see FIG. 3) and the like.

  Here, the storage unit 23e is configured by an EEPROM (Electrically Erasable Programmable Read-Only Memory), and the arithmetic / control unit 23a accesses the storage unit 23e via the system bus 23f. Note that the storage unit 23e may be included in the calculation / control unit 23a in terms of hardware configuration.

  As shown in FIG. 5, the storage unit 23 e stores the first LUT describing the relationship between the electric resistance value of the entire heater element 40 (hereinafter referred to as “total resistance value Ra”) and the temperature TH of the heater element 40. (Look Up Table) 50a, the second LUT 50b describing the relationship between the coolant temperature TW detected by the water temperature sensor 32 (see FIG. 3) and the temperature TH of the heater element 40, and the temperature TH of the heater element 40 and the heater element 40 The third LUT 50c describing the relationship with the heating time TMH is stored. In the present embodiment, each LUT is defined as an array. Here, the number of elements in each array is 256, and the array index takes a value from 0 to 255.

  The arithmetic / control unit 23a can obtain the temperature TH of the heater element 40 by referring to the first LUT 50a using the total resistance value Ra of the heater element 40 as an array index, and the second LUT 50b using the cooling water temperature TW as an array index. , The temperature TH of the heater element 40 can be acquired, and the heating time TMH for driving the heater element 40 is acquired by referring to the third LUT 50c using the temperature TH of the heater element 40 as an array index. Can do. The first LUT 50a to the third LUT 50c are created in advance by performing an experiment or the like and stored in the storage unit 23e. The contents of the first LUT 50a and the second LUT 50b stored in the EEPROM can be updated by the arithmetic / control unit 23a.

  Hereinafter, returning to FIG. 4, the description will be continued. The first switch 23c and the second switch 23d are switching elements, and for example, a power MOSFET (Metal Oxide Semiconductor Field Effect Transistor) can be suitably used. The output of the calculation / control unit 23a is connected to the gates of the first switch 23c and the second switch 23d, and the first switch 23c and the second switch 23d are controlled to be turned on or off by the output of the calculation / control unit 23a. .

  The source of the first switch 23c is connected to a battery power source Bat as a first power source. Here, the battery power source Bat is a direct current power source, and its power source voltage is set to 12 [v]. The source of the second switch 23d is connected to an ECU power source Bec as a second power source. Here, the ECU power supply Bec is a DC power supply, and its power supply voltage is 5 [v]. Note that the ECU power supply Bec is composed of a stabilized power supply that is controlled so that the DC output voltage is always a constant value. Of course, the battery power source Bat may be constituted by a stabilized power source.

  The fuel heating unit 3 includes a fuel heating unit 14 including a heater element 40 and a heater relay 41. Here, the heater element 40 is constituted by a heating wire, and a first heater portion (hereinafter referred to as “first heater 40a”) and a second heater connected in series between the drive terminal 40c and the ground terminal 40d. Part (hereinafter referred to as “second heater 40 b”). As will be described later, the electric resistance value R2 of the second heater 40b is set to be equal to or less than the electric resistance value R1 of the first heater 40a, for example, R1 = 8.6 [Ω], R2 = 5.8 [Ω]. Yes.

  The heater relay 41 is composed of a magnet relay. In general, a magnet relay is suitably used as a power controller because it has a small contact resistance and can conduct a large current and has little power loss. By passing a current through the coil 41a constituting the heater relay 41, the contacts 41b and 41b are electrically connected. A zero cross SSR (solid state relay) may be used instead of the magnet relay.

  As shown in the figure, the drive terminal 40 c of the heater element 40 is connected to the battery power source Bat via the heater relay 41. When the arithmetic / control unit 23a applies a predetermined potential to the gate of the first switch 23c, the coil 41a of the heater relay 41 is connected to the battery power source Bat, the coil 41a is driven, and the contacts 41b and 41b are electrically connected. The drive terminal 40c of the element 40 is connected to the battery power source Bat. That is, the drive terminal 40c is selectively connected to the battery power source Bat via the heater relay 41.

  A test terminal 40e is provided between the first heater 40a and the second heater 40b, and the test terminal 40e is connected to the drain of the second switch 23d. When the arithmetic / control unit 23a applies a predetermined potential to the gate of the second switch 23d, the test terminal 40e is connected to the ECU power supply Bec. That is, the test terminal 40e is selectively connected to the ECU power supply Bec via the second switch 23d.

Here, the arithmetic / control unit 23a controls the first switch 23c and the second switch 23d so as to be in any one of the following states.
First state: the first switch 23c is on and the second switch 23d is off Second state: the first switch 23c is off and the second switch 23d is on Third state: the first switch 23c is off, The second switch 23d is off. In the following description, the fact that the calculation / control unit 23a controls the first switch 23c and the second switch 23d to select the first state is “transition to the first state”. (The same applies to the second state and the third state).

  The first state is a state in which the entire heater element 40 is driven using the battery power source Bat and the fuel is heated in the fuel heating unit 14. That is, by controlling the first switch 23c to be on and the second switch 23d to be off, the contacts 41b and 41b of the heater relay 41 are electrically connected, and the drive terminal 40c of the heater element 40 is connected to the battery power source Bat. On the other hand, the test terminal 40e connected to the drain of the second switch 23d is disconnected from the ECU power supply Bec. Thus, a current i1 flows through the first heater 40a and the second heater 40b connected in series with each other according to the total resistance value Ra of the heater element 40.

  In the second state, the second heater 40b is driven using the ECU power supply Bec, and the value of the electric resistance R2 of the second heater 40b is measured by detecting the value of the current i2 flowing through the second heater 40b. It is a state to do. That is, when the first switch 23c is turned off and the second switch 23d is turned on, the contacts 41b and 41b of the heater relay 41 are opened, and the drive terminal 40c of the heater element 40 is disconnected from the battery power supply Bat. On the other hand, the test terminal 40e connected to the drain of the second switch 23d is connected to the ECU power supply Bec. As a result, a current i2 flows through the second heater 40b in accordance with the electric resistance value R2 of the second heater 40b.

  The third state is a state in which the heater element 40 (including the second heater 40b that is the part) is not energized. That is, when the first switch 23c is turned off and the second switch 23d is also turned off, the drive terminal 40c is disconnected from the battery power supply Bat, and the test terminal 40e is also disconnected from the ECU power supply Bec. Note that the arithmetic / control unit 23a transitions to the third state when the ECU 20 starts operation.

  The current detection circuit 31 is provided in the ECU 20 and includes a current detection resistor 31a, an operational amplifier 31b, and an A / D converter 31c. The current detection resistor 31a is a fixed resistor having an electric resistance Rs of about several tens [mΩ] in general. One end of the current detection resistor 31a is connected to the ground terminal 40d of the heater element 40, and the other end is grounded. Since the electric resistance value of the current detection resistor 31a is much smaller than the electric resistance values of the first heater 40a and the second heater 40b (usually 1/100 or less), the ground terminal 40d is substantially May be considered to be grounded.

  The operational amplifier 31b amplifies the potential difference Vr generated at both ends of the current detection resistor 31a when current flows through the current detection resistor 31a. The A / D converter 31c converts the potential difference as an analog level signal amplified by the operational amplifier 31b into digital data and outputs the digital data. The output of the A / D converter 31c is input to the calculation / control unit 23a. In the second state described above, the value of the current i2 flowing through the second heater 40b is detected by the current detection circuit 31. In addition, the value of the current i1 flowing through the entire heater element 40 in the first state may be detected. However, the path length (harness length) through which the current i2 flows in the second state is shorter than the path length through which the current i1 flows in the first state, and the harness resistance is relatively small. The value of the current i2 can be detected with high accuracy.

  Here, if a resistor having a known electric resistance value Rs is used as the current detection resistor 31a, the power supply voltage of the ECU power supply Bec for driving the second heater 40b is also known (5.0 [v] as described above). Therefore, by detecting the value of the current i2 by the current detection circuit 31 in the second state, the electric resistance value R2 of the second heater 40b can be measured from Ohm's law (R = E / I). . The measurement result is stored in the storage unit 23e by the calculation / control unit 23a.

  In the present embodiment, the first heater 40a and the second heater 40b are made of the same material and are disposed substantially at the same position of the fuel heating unit 14, so that the first heater 40 is driven when the entire heater element 40 is driven. Since the heater 40a and the second heater 40b have the same temperature, and the driving time of these two heaters can be regarded as substantially the same (the period in which the second state is maintained is 1/100 compared with the period in the first state). As a result, the ratio between the electric resistance value R1 of the first heater 40a and the electric resistance value R2 of the second heater 40b is kept constant.

  By using this characteristic, the calculation / control unit 23a uses the measured electric resistance value R2 of the second heater 40b to determine the value of the combined resistance of the first heater 40a and the second heater 40b, that is, the heater element. A total resistance value Ra of 40 is estimated. That is, if R1: R2 is constant, R1 is determined by actually measuring R2, and the total resistance value Ra = R1 + R2 can be calculated.

  Hereinafter, description will be made with reference to FIG. The arithmetic / control unit 23a refers to the first LUT 50a using the estimated total resistance value Ra and acquires the temperature TH of the heater element 40. Then, using the temperature TH of the heater element 40, the fuel heating time TMH is obtained by referring to the third LUT 50c. The arithmetic / control unit 23a transitions to the first state described above based on the acquired heating time TMH and heats the fuel. In the present embodiment, the first state is continuously maintained based on the acquired heating time TMH. However, when a solid state relay is employed as the heater relay 41, a high-speed on / off operation is possible. Therefore, PWM (pulse width modulation) driving may be performed. Thereby, the energization amount to the heater element 40 is controlled.

  In the present embodiment, the arithmetic / control unit 23a first transitions from the above-described third state to the second state and estimates the total resistance value Ra of the heater element 40. Next, the arithmetic / control unit 23a transits from the second state to the first state (in actual control, the first switch 23c and the second switch 23d are both prevented from instantaneously being turned on. Therefore, the arithmetic / control unit 23a changes the order of the second state → the third state → the first state), and heats the fuel with the heater element 40. It is known that a resistance element such as a heating wire constituting the heater element 40 generally increases in electric resistance value at a high temperature (see the characteristic (solid line portion) of the first LUT 50a shown in FIG. 5). According to the embodiment, the total resistance value Ra of the heater element 40 is estimated prior to the heating of the fuel, and the fuel is appropriately heated when the internal combustion engine E is started based on the estimated value.

  FIG. 6 is an explanatory diagram for explaining the setting of the resistance ratio α of the heater element 40. Hereinafter, FIG. 6 will be used together with FIG. 4 to describe the electric resistance values of the first heater 40a and the second heater 40b constituting the heater element 40 in detail. In FIG. 6, the description of the first switch 23c, the second switch 23d, and the current detection resistor 31a is omitted for the sake of simplicity.

If the ratio (hereinafter referred to as resistance ratio α or simply α) of the total resistance value Ra of the heater element 40 occupied by the electric resistance value of the second heater 40b is α (0 <α <1),
The electric resistance value R1 of the first heater 40a is R1 = Ra × (1−α).
The electric resistance value R2 of the second heater 40b is R2 = Ra × α.
It is expressed.

Here, if the power supply voltage of the battery power supply Bat connected to the drive terminal 40c is V1, and the power supply voltage of the ECU power supply Bec connected to the test terminal 40e is V2,
In the second state described above, the current flows only through the second heater 40b, and the current value I2 at this time is
I2 = V2 / (α × Ra) (Formula 1)
It becomes.

On the other hand, in the first state described above, the current flows through both the first heater 40a and the second heater 40b connected in series with each other, and the current value I1 at this time is
I1 = V1 / {Ra × (1-α) + Ra × α} = V1 / Ra (Expression 2)
It becomes.

Considering that a certain noise component is additionally superimposed on the current due to the routing of the harness, etc., the noise component becomes relatively small by increasing the current flowing through the current detection resistor 31a when measuring the electric resistance. Measurement accuracy can be improved. That is, the entire heater element 40 is not energized, but only the second heater 40b, which is a part of the heater element 40, is energized, and the current value I2 is increased at this time (the total resistance of the entire heater element 40). The electric resistance value R2 of the second heater 40b, which is a part of the second heater 40b, is naturally smaller than the value Ra, so that a larger current value I2 can be easily ensured). Therefore, I2> I1 should be satisfied. From Equation 1 and Equation 2,
V2 / (α × Ra)> V1 / Ra (Expression 3)
Solving for α,
α <V2 / V1 (Formula 4)

The power consumption P2 of the second heater 40b in the second state is
P2 = V2 ² / R2 = V2 ² / (Ra × α) (Formula 5)
The power consumption P1 of the first heater 40a and the second heater 40b in the first state is
P1 = V1 ² / Ra (Formula 6)

Since power consumption is reduced by making the power consumption in the second state smaller than that in the first state, P2 <P1 should be satisfied. Therefore, from Equation 5 and Equation 6,
V2 ² / (Ra × α) <V1 ² / Ra (Expression 7)
Solving for α,
α> V2 ² / V1 ² (Equation 8)

Therefore, from Equation 4 and Equation 8,
V2 ² / V1 ² <α <V2 / V1 (Equation 9)
The range of the resistance ratio α may be determined so as to satisfy the above condition.

Specifically, in this embodiment, since V1 = 12 [v] and V2 = 5 [v], the resistance ratio α is expressed by Equation 9 as follows:
0.174 <α <0.417
Is set in the range.

  At the lower limit value (α = 0.174) of the resistance ratio α, the current i2 flowing through the second heater 40b is maximized when measuring the resistance value R2, and the measurement accuracy is the highest, but the power consumption is the heater element. This is almost the same as when the entire 40 is driven. On the other hand, in the upper limit value (α = 0.417) of the resistance ratio α, the current i2 flowing through the second heater 40b when measuring the resistance value R2 is substantially equal to that when the entire heater element 40 is driven. Power consumption is the smallest. For example, by setting the resistance ratio α to an intermediate value between the upper limit value and the lower limit value ((0.174 + 0.417) /2=0.296), the measurement accuracy of the electric resistance value of the second heater 40b is improved. The power consumption during measurement can be reduced. Of course, the range of the resistance ratio α may be arbitrarily determined between the upper limit value and the lower limit value, depending on which of the improvement in measurement accuracy and the reduction in power consumption is prioritized. Of course, the resistance ratio α may be set larger (for example, 0.5) within a range in which the measurement accuracy in the current detection circuit 31 can be maintained. By doing in this way, the power consumption at the time of measuring resistance value can be reduced further.

In the fuel heating unit 3, the target consumed by the heater element 40 in consideration of the environmental temperature range in which the internal combustion engine E (see FIG. 1) is placed, the heating time allowed when the internal combustion engine E is started, and the like. Electric power is determined. For example, if the power supply voltage of the battery power supply Bat to which the drive terminal 40c of the heater element 40 is connected is 12 [V] and the target power is 10 [W], Equation 6 is transformed,
Ra = V1 ² / P1 (Formula 10)
Thus, Ra = 144/10 = 14.4 [Ω] is calculated.

When the heater element 40 has such a total resistance value Ra,
For example, when the resistance ratio α is the above-described intermediate value (α = 0.296),
Electric resistance value R1 of the first heater 40a = 14.4 × (1−0.296) = 10.14 [Ω]
Electric resistance value R2 of the second heater 40b = 14.4 × 0.296 = 4.26 [Ω]
It is determined as follows. Based on this value, for example, by adjusting the length of the heating wire constituting the first heater 40a and the second heater 40b, the heater element 40 having two heater portions having specific electrical resistance values can be easily obtained. Can be realized.

  Hereinafter, returning to FIG. The first LUT 50a is a function (first temperature estimating means) that inputs the total resistance value Ra of the heater element 40 and outputs the temperature TH of the heater element 40, and the second LUT 50b receives the cooling water temperature TW and inputs the temperature of the heater element 40. It is a function (second temperature estimation means) that outputs TH. In the present embodiment, the arithmetic / control unit 23a refers to the first LUT 50a using the output of the current detection circuit 31 (total resistance value Ra estimated from now), or refers to the second LUT 50b using the output of the water temperature sensor 32. It is possible to estimate the temperature TH of the heater element 40 by any of the above.

  The outputs of the first temperature estimating means and the second temperature estimating means are normalized to an 8-bit quantity. For example, the correspondence between the value of the array element and the temperature TH of the heater element 40, such as 0x1f → 0 ° C., is the same as the first LUT 50a. It is the same as the second LUT 50b.

  The calculation / control unit 23a executes the estimation of the temperature TH of the heater element 40 using the first LUT 50a and the second LUT 50b at a timing close to each other during cold operation. For example, the output of the outside air temperature sensor (not shown) and the first and second temperatures By comparing with the output of the estimating means, it is possible to easily determine the disconnection of the heater element 40, the failure of the NTC (Negative Temperature Coefficient Thermistor) thermistor constituting the water temperature sensor 32, or the like. In addition, by providing a plurality of temperature estimation means in this way, fail-safe is achieved without referring to the output of the temperature estimation means in which a failure is detected.

  Now, it is known that a resistor such as a heating wire used for the heater element 40 undergoes secular change due to long-term driving, and the value of electric resistance gradually increases. That is, as the secular change of the heater element 40 progresses, the total resistance value Ra increases, so that the temperature TH of the heater element 40 is observed higher than the actual temperature. On the other hand, a passive element such as an NTC (Negative Temperature Coefficient Thermistor) thermistor constituting the water temperature sensor 32 generally has a very small secular change.

  For these reasons, the calculation / control unit 23a determines that the outputs of the first and second temperature estimation means are both in the normal range, and the absolute value of the output difference between the two is greater than a predetermined threshold value. If this occurs (hereinafter, this condition is referred to as “LUT update condition”), the contents of the first LUT 50a, which is the first temperature estimation means, are updated to compensate for the secular change of the heater element 40. Of course, the contents of the first LUT 50a may be updated when the LUT update condition satisfies another requirement, for example, the LUT update condition a plurality of times.

  When the LUT update condition is satisfied, the contents of the first LUT 50a are updated by the following first processing procedure. In the first processing procedure, the second LUT 50b is used as a reference.

<First processing procedure>
(A) The temperature TH of the heater element 40 is estimated from the coolant temperature TW using the second LUT 50b.
(B) The value of the temperature TH is searched from the array element of the first LUT 50a.
(C) An array index corresponding to the temperature TH in the first LUT 50a (hereinafter, the array index obtained by searching the value of the temperature TH is referred to as “INDX1”) is acquired. If no hit is found, INDX1 closest to the value of temperature TH is obtained. In the process of (c), it is assumed that the updated first LUT 50a is a monotonically increasing (or monotonically decreasing) function.

(D) Transition to the second state described above, measure the electric resistance value R2 of the second heater 40b (see FIG. 4), and estimate the total resistance value Ra of the heater element 40.
Here, the total resistance value Ra of the heater element 40 is the array index of the first LUT 50a (hereinafter, the array index based on the total resistance value Ra of the heater element 40 is referred to as “INDX2”) (that is, the input of the first LUT 50a). ). When the total resistance value Ra of the heater element 40 is increased due to aging, INDX2> INDX1 is satisfied.
(E) Calculate δp = INDX2−INDX1.
(F) The array element of the first LUT 50a is shifted to the right by δp within the array.
However, this processing is performed in a range where the value of the array index + δp does not exceed the number of array elements, and NULL is assigned to the array elements corresponding to 0 to (δp−1) in the array index. By the process (f), the first LUT 50a is translated to the right as indicated by the dotted line in FIG. Then, the arithmetic / control unit 23a stores the newly generated first LUT 50a in the storage unit 23e (see FIG. 4).

  The processing procedures (a) to (f) described above are based on the premise that the total resistance value Ra of the heater element 40 changes over time, and the contents of the first LUT 50a are updated to eliminate the influence of the change over time. is there. On the other hand, when the total time for which the heater element 40 is driven is relatively short and it is not necessary to consider the secular change of the total resistance value Ra, the contents of the second LUT 50b are updated using the first LUT 50a as a reference. Also good. As a result, the contents of the second LUT 50b are constantly updated in accordance with the state of the internal combustion engine E. Even when the contents of the second LUT 50b are updated, the LUT update conditions are the same as those in the first processing procedure described above. The second processing procedure for updating the second LUT 50b is as follows.

<Second processing procedure>
(G) Transition to the second state to estimate the total resistance value Ra of the heater element 40, and estimate the temperature TH of the heater element 40 by referring to the first LUT 50a using the total resistance value Ra.
(H) The value of the temperature TH is retrieved from the array element of the second LUT 50b.
(I) An array index (INDX1) corresponding to the temperature TH in the second LUT 50b is acquired. If there is no hit, INDX1 closest to the value of temperature TH is obtained. In the process (i), it is assumed that the second LUT 50b is a monotonically increasing (or monotonically decreasing) function.

(J) The cooling water temperature TW is measured.
Here, the cooling water temperature TW is the array index (INDX2) itself of the second LUT 50b.
(K) Calculate δp = INDX2−INDX1.
(L) When δp is a positive number, the array element of the second LUT 50b is shifted to the right by δp within the array. When δp is a negative number, the array element of the second LUT 50b is shifted left by δp.
Then, the arithmetic / control unit 23a stores the newly generated second LUT 50b in the storage unit 23e (see FIG. 4).

  FIG. 7A is an explanatory view showing a first start mode of the internal combustion engine E, and FIG. 7B is an explanatory view showing a second start mode of the internal combustion engine E. More specifically, FIGS. 7A and 7B show the relationship between the measurement period SP for measuring the electric resistance value R2 of the second heater 40b and the heating period DP for driving the heater element 40 in each start mode. Show. Hereinafter, each start mode will be described with reference to FIGS. 3, 4 and 5 in FIGS. 7 (a) and 7 (b).

  In the following description, the state of the ignition switch 35, the output of the water temperature sensor 32, etc. are detected or measured by the ECU 20 (both see FIG. 3) and transmitted to the fuel heating control unit 23 (see FIG. 3) together with predetermined event information. Is done. The calculation / control unit 23a (see FIG. 4) of the fuel heating control unit 23 receives this event information, thereby executing the transition from the first state to the third state described above, and that the heating of the fuel is completed. This information is transmitted from the calculation / control unit 23a to the ECU 20 together with predetermined event information, and the ECU 20 that has received the information operates an actuator such as the starter motor 28 in response to a start operation of the passenger or the like.

<First start mode>
In the first start mode, when the ignition switch 35 (see FIG. 3) is operated to the IG position (described as “ignition ON” in FIG. 7A, the same applies to FIG. 7B), for example, by the ECU 20 When the difference between the measured cooling water temperature TW and the output of an outside air temperature sensor (not shown) is larger than a predetermined threshold, that is, the internal combustion engine E (see FIG. 1) is in an intermediate state between when warmed up and when cold, Selected when warming up.

  In the first start mode, as shown in FIG. 7A, when the ignition switch 35 is operated to the IG position, the calculation / control unit 23a of the fuel heating control unit 23 transitions to the second state, and the second heater The electric resistance value R2 of 40b is measured, and the total resistance value Ra of the heater element 40 (both see FIG. 4) is obtained. Here, when obtaining the total resistance value Ra, the time during which the second heater 40b is energized (measurement period SP) is about 200 ms. Then, the calculation / control unit 23a estimates the temperature TH of the heater element 40 with reference to the first LUT 50a (see FIG. 5), and further heats the heater element 40 with reference to the third LUT 50c (see FIG. 5). Get TMH.

  The arithmetic / control unit 23a transitions to the above-described first state at a predetermined timing (here, after the measurement period SP ends), and continues the first state for the heating period DP. That is, the fuel is heated by controlling the energization amount of the heater element 40 according to the heating period DP. As described above, the heating period DP is a function described in the third LUT 50c and whose period length is determined by the temperature TH of the heater element 40, and is between several tens of seconds and several minutes. When the heating period DP elapses, the calculation / control unit 23a transitions to the third state, the energization of the heater element 40 is stopped, and thereafter event information indicating completion of heating is transmitted from the calculation / control unit 23a to the ECU 20. The ECU 20 starts the operation of the internal combustion engine E by starting the starter motor 28 (see FIG. 3) based on an instruction from the operator.

  In the sequence of the first start mode, the measurement period SP is started from the time when the ignition switch 35 is operated to the IG position, and the fuel heating is actually started after the ignition switch 35 is operated to the IG position. After about 200 ms, the second state described above is maintained in the measurement period SP, and the power consumption when measuring the electric resistance value R2 of the second heater 40b is kept low. Note that the ECU 20 may detect that the vehicle door has been opened or the driver has been seated, and the measurement period SP may be set at that time. By doing in this way, it becomes possible to start heating period DP immediately after the ignition switch 35 is operated to the IG position.

  As described above, in the first start mode, the calculation / control unit 23a determines the electric resistance of the heater element 40 based on the output of the current detection circuit 31 when the test terminal 40e is connected to the ECU power supply Bec as the second power supply. A value (total resistance value Ra) is estimated, and based on this estimated value, the drive terminal 40c is connected to the battery power source Bat as the first power source to control the energization amount of the heater element 40. In other words, the calculation / control unit 23a determines the timing for connecting the drive terminal 40c to the battery power source Bat and the timing for disconnecting the drive terminal 40c from the battery power source Bat.

<Second start mode>
In the second start mode, when the ignition switch 35 is once turned off and then operated to the IG position, for example, the difference between the coolant temperature TW measured by the ECU 20 and the output of an outside air temperature sensor (not shown) is a predetermined value. It is selected when it is smaller than the threshold value. That is, the second start mode is selected when the internal combustion engine E is cold.

  In the second start mode, as shown in FIG. 7B, when the ignition switch 35 is operated to the IG position, the arithmetic / control unit 23a immediately starts energizing the heater element 40. That is, in the second start mode, the predetermined timing at which energization of the heater element 40 is started is immediately after the ignition switch 35 is in the IG position. Since the cooling water temperature TW and the temperature TH of the heater element 40 have a very high correlation when cold, the calculation / control unit 23a refers to the second LUT 50b using the cooling water temperature TW measured by the water temperature sensor 32. The temperature TH of the heater element 40 is acquired. Then, the heating time TMH of the heater element 40 is acquired by referring to the third LUT 50c using the temperature TH.

  The arithmetic / control unit 23a sets the heating period DP based on the acquired heating time TMH, and transitions to the first state described above to energize the heater element 40. As described above, in the second start mode, when the ignition switch 35 is operated to the IG position, the heater element 40 starts heating the fuel immediately after changing to the first state without changing to the second state. As a result, the time required to start the internal combustion engine E is shortened by δt (specifically, about 200 to 500 ms) compared to the first start mode.

  In the second start mode, the measurement period SP is set during operation of the internal combustion engine E (when warming up). More specifically, the operation of the internal combustion engine E is continued for a predetermined period, and the temperature TH of the heater element 40 (the above-described third state is maintained during operation and the heater element 40 is not energized). The measurement period SP is set when the cooling water temperature TW of the internal combustion engine E is in an equilibrium state. The value R2 of the electrical resistance of the second heater 40b measured during the measurement period SP is stored in the storage unit 23e (see FIG. 4).

  Then, the arithmetic / control unit 23a reads the electric resistance value R2 of the second heater 40b stored in the storage unit 23e, updates the second LUT 50b according to the above-described second processing procedures (g) to (l), and updates it. The stored second LUT 50b is stored in the storage unit 23e. Then, the temperature TH of the heater element 40 is estimated from the coolant temperature TW using the updated second LUT 50b, the heating time TMH is determined from the estimated temperature TH, and the energization amount of the heater element 40 is based on the heating time TMH. Is controlled.

  Of course, the first LUT 50a may be updated and stored in accordance with the first processing procedures (a) to (f) described above. As a result, the first LUT 50a is kept in the latest state in which the aging of the heater element 40 is compensated.

  As described above, in the second start mode, the output of the current detection circuit 31 is measured when the internal combustion engine E is warmed up, and the total resistance value Ra of the heater element 40 is estimated based on the measurement result. At this time, the length of the period for connecting the drive terminal 40c (see FIG. 4) to the battery power source Bat is determined based on the estimated total resistance value Ra.

  In both the first start mode and the second start mode, the measurement period SP is a short period of about 200 ms. For this reason, the change in electrical resistance due to the heat generated by the second heater 40b during the measurement period SP is minute, and does not deteriorate the measurement accuracy of the resistance value, and further the secular change of the second heater 40b is accelerated. There is nothing. The heater element 40 is provided for each cylinder. However, since the power consumption in the measurement period SP is reduced as described above, the electric resistance value R2 of the second heater 40b is simultaneously applied to the plurality of cylinders S. Can be measured.

  The third LUT 50c has been described as having a single characteristic, but a plurality of LUTs describing different characteristics are prepared, for example, referring to the output of the LAF sensor 34 (see FIG. 3), The LUT used as the third LUT 50c may be selected according to the alcohol concentration in the fuel.

  Although the description of the specific embodiment is finished as described above, the present invention is not limited to this embodiment and can be widely modified. For example, in the present embodiment, the heating device 7 according to the present invention is applied to an FFV engine, but it can also be applied to an internal combustion engine E that uses other components as fuel, such as light oil and gasoline, other than inline four cylinders. Of course, the present invention can also be applied to the internal combustion engine E. Further, the heater element 40 may be provided in the injector, or may be provided in a common rail in the fuel supply path. Further, the intake air introduced into the internal combustion engine E by the heater element 40 may be heated. Further, the heater element 40 may be composed of three or more heater portions, and the present invention can be easily applied if at least the resistance ratio of each heater portion is known.

  The heating device and the heater element according to the present invention accurately measure the resistance value of a part of the heater element to accurately estimate the resistance value of the entire heater element, and reduce power consumption when measuring the resistance value. Therefore, it can be suitably used for a heating device for heating fuel used in a vehicle.

DESCRIPTION OF SYMBOLS 1 Fuel supply apparatus 3 Fuel heating unit 7 Heating apparatus 14 Fuel heating part 20 ECU
23 Fuel Heating Control Unit 23a Calculation / Control Unit (Control Unit)
23c 1st switch 23d 2nd switch 23e Memory | storage part 31 Current detection circuit 31a Current detection resistance 32 Water temperature sensor 35 Ignition switch 40 Heater element 40a 1st heater (1st heater part)
40b Second heater (second heater part)
40c Drive terminal 40d Ground terminal 40e Test terminal 41 Heater relay 50a First LUT
50b 2nd LUT
50c 3rd LUT
Bat Battery power supply (first power supply)
Bec ECU power supply (second power supply)

Claims (7)

A heater element comprising a first heater portion and a second heater portion connected in series between a drive terminal and a ground terminal;
A first power source connected to the drive terminal at a predetermined timing;
A second power source selectively connected to a test terminal provided between the first heater portion and the second heater portion;
A current detection circuit connected in series to the heater element;
A value of an electric resistance of the heater element is estimated based on an output of the current detection circuit when the test terminal is connected to the second power supply, and the drive terminal is connected to the first power supply based on the estimated value. And a controller for controlling the energization amount of the heater element.   2. The heating apparatus according to claim 1, wherein the electric resistance value of the second heater portion is equal to or less than the electric resistance value of the first heater portion.   The heating apparatus according to claim 1 or 2, wherein the voltage of the second power source is set lower than the voltage of the first power source. The value of the electric resistance of the first heater portion is R1,
The electric resistance value of the second heater portion is R2,
The power supply voltage of the first power supply is V1,
The power supply voltage of the second power supply is V2,
When the resistance ratio α = R2 / (R1 + R2),
The resistance ratio α is
V2 ² / V1 ² <α <V2 / V1
The heating device according to any one of claims 1 to 3, wherein the heating device is set in a range of. The heater element is mounted on an internal combustion engine;
The controller is
The output of the current detection circuit is measured when the internal combustion engine is warmed up, and the value of the electrical resistance of the heater element is estimated based on the measurement result, and the estimated electrical resistance value is obtained when the internal combustion engine is cold. The heating apparatus according to any one of claims 1 to 4, wherein a length of a period for connecting the drive terminal to the first power source is determined based on the length.   The heating device according to claim 5, wherein the heater element is provided in each of a plurality of cylinders of the internal combustion engine, and heats fuel supplied to the cylinders. A heater element composed of a first heater portion and a second heater portion connected in series with each other,
A drive terminal connected to a first power source when driving the heater element;
A heater element, comprising: a test terminal connected between the first heater part and the second heater part and connected to a second power source when estimating the electric resistance value of the heater element.

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