JP5029654B2 - Electronic control device - Google Patents

Description

  The present invention relates to an electronic control device that controls a piezo element used in an injector that injects fuel.

  2. Description of the Related Art Conventionally, an electronic control device expands and contracts a piezo element by charging and discharging charges of the piezo element in an injector, and opens or closes the valve by this expansion and contraction (see, for example, Patent Document 1). The electronic control device includes a first transistor, a second transistor, a first diode, a second diode, an electromagnetic coil, a power supply circuit, and a charge / discharge control circuit.

  The first and second transistors are connected in series between the output terminal of the power supply circuit and the ground. The electromagnetic coil is connected between the common connection terminal of the first and second transistors and the ground. The piezo element is connected between the electromagnetic coil and the ground.

  The first diode is connected between the output terminal of the power supply circuit and the common connection terminal of the first and second transistors. As a result, the first diode is connected in parallel to the first transistor.

  The second diode is connected between the common connection terminal of the first and second transistors and the ground. As a result, the second diode is connected in parallel to the second transistor.

When the charge / discharge control circuit switches the first transistor, electric charge is stored in the piezo element by the current flowing from the electromagnetic coil to the piezo element.
Specifically, when the first transistor is turned on, electric charge is stored in the piezo element by a current flowing from the power supply circuit to the piezo element through the first transistor and the electromagnetic coil. When the first transistor is turned off, electric charge is accumulated in the piezo element by the current flowing from the ground side to the piezo element through the second diode and the electromagnetic coil.

  The charge / discharge control circuit switches the second transistor to discharge the charge from the piezo element. Specifically, when the second transistor is turned on, the electric current is discharged from the piezoelectric element through the electromagnetic coil and the second transistor, thereby discharging the electric charge from the piezoelectric element. On the other hand, when the second transistor is turned off, a current is allowed to flow from the piezo element to the power supply circuit through the electromagnetic coil and the first diode, whereby electric charge is discharged from the piezo element.

  In this way, the piezoelectric element is charged or discharged by switching one of the first and second transistors.

JP-A-10-308542

  In the above-described electronic control device, it is required to control charging of the piezo element with high accuracy in order to open the injector with high accuracy.

  Therefore, the present inventor refers to the electronic circuit shown in FIG. 8 and controls the amount of energy Q stored in the piezo element by controlling the amount of charge Q discharged from the power supply circuit to the piezo element when charging the piezo element. We considered approaching the value.

  First, the energy stored in the piezo element is determined by the product (= Q × Vdc) of the amount of charge Q released from the power supply circuit to the piezo element and the power supply voltage Vdc applied from the power supply circuit to the piezo element. The amount of charge Q released from the power supply circuit to the piezo element can be obtained from the current flowing through the piezo element.

  However, in general, the power supply voltage Vdc output from the power supply circuit to the piezo element is controlled to be within a certain range as shown in FIG. 9, but is not a constant voltage. Therefore, in order to control the amount of charge Q discharged from the power supply circuit to the piezo element in order to bring the energy stored in the piezo element close to the target value by the charge / discharge control circuit, the current flowing through the piezo element and the power supply circuit It is necessary to acquire each output power supply voltage.

  Therefore, as shown in FIG. 8, the present inventor, in addition to the current sensor 2a for detecting the current flowing through the piezo element 2, sets the output voltage Vdc of the power supply circuit to the first and second resistance elements R1, R2 and the first resistance element R1, R2. Voltage dividing circuit 70 that divides the voltage by the third resistance element R3 and outputs the voltage between the second and third resistance elements R2 and R3 as a divided voltage, and the divided voltage output from the voltage dividing circuit 70 The use of an A / D converter for analog / digital conversion was studied.

  For example, if the theoretical value of the voltage dividing ratio of the voltage dividing circuit 70 is stored in the memory in advance, the microcomputer can obtain the power supply voltage based on the theoretical value of the voltage dividing ratio and the output signal of the A / D converter.

  Here, when the resistance values r1, r2, and r3 of the first to third resistance elements R1, R2, and R3 are respectively taken, the theoretical value of the voltage dividing ratio of the voltage dividing circuit is represented by (r3 / (r1 + r2 + r3)). However, due to the initial tolerance, an error occurs between the actual values of the resistance values r1 to r3 and the theoretical values (design values) of the resistance values r1 to r3. In addition, the resistance values r1 to r3 of the first to third resistance elements R1, R2, and R3 change due to deterioration over time. Therefore, an error occurs between the theoretical value of the voltage dividing ratio in the voltage dividing circuit 70 and the actual value of the voltage dividing ratio.

  In recent years, it has been required to increase the fuel injection pressure in order to reduce solid particulates contained in engine exhaust gas. In order to increase the injection pressure, it is necessary to increase the pressure of the fuel supplied from the common rail to the injector.

  Here, if an injector is used in which a high pressure of fuel is applied to the piezo element and the piezo element is opened by injecting the fuel against the high fuel pressure to inject the fuel, the piezo element is extended. Requires a lot of energy. Accordingly, it is necessary to increase the energy stored in the piezo element. Therefore, it is necessary to set the power supply voltage Vdc output from the power supply circuit to a very high value (for example, a voltage of 200 V or more).

  Therefore, since the power supply voltage itself is a very high and large value in this way, if an error occurs between the theoretical value of the voltage division ratio and the actual value of the voltage division ratio, the power supply voltage calculated by the microcomputer and the power supply voltage The value of the error that occurs between the actual value and the actual value becomes large.

  That is, if an error occurs between the theoretical value of the voltage division ratio and the actual value of the voltage division ratio, the accuracy of the power supply voltage value calculated by the microcomputer is deteriorated. Therefore, it becomes difficult to control the piezo element with high accuracy.

  In view of the above-mentioned points, the present invention has as its first object to provide an electronic control device that obtains an actual value of a voltage dividing ratio of a voltage dividing circuit, and to reduce the amount of charge released from a power supply circuit to a piezo element. It is a second object of the present invention to provide an electronic control device that controls the energy stored in the piezo element so as to be close to the target value with high accuracy.

In order to achieve the above object, in the first aspect of the present invention, determination means (S301) for determining whether or not the power supply voltage has reached a maximum value (Vset) in a certain range;
When the determination unit (S301) determines that the power supply voltage (Vdc) has reached the maximum value (Vset), the divided voltage (Va) is acquired, and the acquired divided voltage is divided by the maximum value. Voltage dividing ratio calculating means (S302) for calculating the value (Va / Vset) as an actual value (kb ′) of the voltage dividing ratio of the first voltage dividing circuit.

  As a result, it can be calculated as the actual value (kb ′) of the voltage dividing ratio of the first voltage dividing circuit.

  According to the second aspect of the present invention, the divided voltage (Va) is acquired and set based on the acquired divided voltage (Va) and each resistance value of the plurality of resistance elements (R1, R2, R3). Based on the theoretical value (kb) of the divided voltage ratio of the first divided voltage circuit (70) and the actual value (kb ′) of the divided voltage ratio calculated by the divided voltage ratio calculating means (S302) Power supply voltage calculation means (S303, S306, S100, S102) for calculating the actual value (Vdet ′) of the power supply.

  Thus, the actual value (Vdet ') of the power supply voltage can be calculated.

Specifically, in the invention described in claim 3, the voltage division ratio calculation means (S302) is common every time the determination means (S301) determines that the power supply voltage (Vdc) has reached the maximum value (Vset). The divided voltage (Va) output from the connection terminal (70a) is acquired, and the actual value (kb ′) of the voltage dividing ratio is repeatedly calculated for each acquisition,
The power supply voltage calculation means (S303, S306, S100, S102)
First calculation means (S303) for repeatedly calculating a value (k (n), k (n + 1)) obtained by dividing the theoretical value (kb) of the partial pressure ratio by the actual value (kb ′) of the partial pressure ratio (S303) When,
Average calculating means (S306) for calculating an average value of values (k (n), k (n + 1)) calculated for each acquisition by the first calculating means;
The divided voltage (Va) output from the common connection terminal (70a) is acquired, and the acquired divided voltage is divided by the theoretical value (kb) of the voltage dividing ratio to obtain the theoretical value (Vdet) of the power supply voltage. Second calculating means (S100) for calculating;
A third value for calculating an actual value (Vdet ′) of the power supply voltage by multiplying the theoretical value (Vdet) of the power supply voltage calculated by the second calculation means by the average value (k) calculated by the average calculation means. And calculating means (S102).

The invention according to claim 4 includes current detection means (80, 82) for detecting a current flowing through the piezo element (2).
The charge control circuit (90) brings the energy stored in the piezo element (2) close to the target value based on the current detected by the current detection means (80, 82) and the actual value (Vdet ′) of the power supply voltage. Thus, the switching element (SW1) is controlled.

  In this way, based on the current detected by the current detection means (80, 82) and the actual value (Vdet ') of the power supply voltage, the switching element so that the energy stored in the piezo element (2) approaches the target value. (SW1). For this reason, the amount of electric charge discharged from the power supply circuit to the piezo element can be controlled, and the energy stored in the piezo element can be brought close to the target value with high accuracy.

Specifically, in the invention described in claim 5, the target charge amount (Qt) that needs to be stored in the piezo element (2) in order to store the energy of the target value in the piezo element (2) is the power supply voltage. Target charge amount calculation means (S113) for calculating based on the actual value (Vdet ′) of
The charge control circuit (90) calculates the amount of charge stored in the piezo element (2) after the switching of the switching element (SW1) is started based on the current detected by the current detection means (80, 82). The switching of the switching element (SW1) is continued until the charged amount reaches the target charge amount (Qt) calculated by the target charge amount calculation means.

The invention according to claim 6 includes a pressure sensor (97) for detecting the pressure of the high-pressure fuel supplied from the common rail (15) to the injector (10),
The target charge amount calculation means (S113) sets the target charge amount (Qt) to a larger value as the detected pressure of the pressure sensor (97) increases.

  Thereby, the target charge amount (Qt) corresponding to the fuel pressure applied to the piezo element can be obtained.

According to the seventh aspect of the present invention, there are a plurality of resistance elements (R4, R5) connected in series between the output terminal (50a) and the ground, and any of the plurality of resistance elements (R4, R5). A second voltage dividing circuit (75) for outputting a voltage between the two resistance elements as a divided voltage;
A voltage output circuit (87a) for outputting a reference voltage for comparing the divided voltage from the second voltage dividing circuit in order to determine whether or not the power supply voltage has reached the maximum value;
A signal indicating that the power supply voltage has reached the maximum value, assuming that the power supply voltage has reached the maximum value when the divided voltage from the second voltage dividing circuit becomes higher than the reference voltage output from the voltage output circuit. A comparison circuit (85a) for outputting
The determination means (S301) determines the power supply voltage to the maximum value (Vset) based on the output signal output from the comparison circuit (85a) when the divided voltage from the second voltage dividing circuit becomes higher than the reference voltage. Is determined to have reached.

  In the invention according to claim 8, the plurality of resistance elements (R4, R5) constituting the second voltage dividing circuit (75) are the plurality of resistance elements (R1) constituting the first voltage dividing circuit (70). , R2, R3), the difference between the actual resistance value and the theoretical resistance value is small, and the change in resistance value due to aging is small.

The invention according to claim 9 includes a diode (D2) in which the cathode terminal is connected to the switching element side terminal and the anode terminal is connected to the ground side of the electromagnetic coil (60),
When the charge control circuit (90) switches the switching element (SW1) and the switching element (SW1) is on, the piezoelectric element passes from the output terminal (50a) through the switching element (SW1) and the electromagnetic coil (60). When the current flowing in (2) stores energy in the electromagnetic coil (60), charges the piezo element (2), and the switching element (SW1) is off, the energy is stored in the electromagnetic coil (60). The piezoelectric element is charged with a current that flows from the ground side to the piezoelectric element (2) through the diode (D2) and the electromagnetic coil (60) based on energy.

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

It is a figure which shows the fragmentary sectional view of the injector for fuel injection apparatuses in one Embodiment of this invention. It is a figure which shows the electronic circuit structure of engine ECU of FIG. It is a flowchart which shows the power supply voltage calculating process performed by the microcomputer of FIG. It is a flowchart which shows the charge control process performed by the microcomputer of FIG. It is a graph which shows the relationship between the rail pressure used by the charge control process of FIG. 4, and the target value (target En) of energy. It is a flowchart which shows the average correction coefficient calculation process performed with the microcomputer of FIG. 3 is a timing chart showing a power supply voltage signal SFLG output from the power supply control circuit of FIG. 2 and a power supply voltage output from a DC / DC power supply circuit. It is a figure which shows the electronic circuit structure of engine ECU used for inventors' examination. It is a timing chart which shows the power supply voltage output from the power supply circuit of FIG.

(First embodiment)
A first embodiment of the present invention will be described. FIG. 1 is a diagram showing a partial cross-sectional view of an injector for a fuel injection device according to a first embodiment of the present invention.

  First, the configuration and operation of the injector 10 will be described. The injector 10 injects fuel stored in the common rail 15 into a cylinder of a diesel engine (not shown). The common rail 15 is a tank that stores fuel. A high pressure is applied to the common rail 15 by the operation of the supply pump 25. Thereby, the pressure of the fuel in the common rail 15 is high.

  The injector 10 includes a nozzle 1 that injects fuel when the valve is opened, a piezo element 2 that expands and contracts due to charge and discharge, and a back pressure control mechanism 3 that is driven by the piezo element 2 to control the back pressure of the nozzle 1.

  The nozzle 1 includes a nozzle body 12 in which an injection hole 11 is formed, a needle 13 that opens and closes the injection hole 11 by contacting and separating from the valve seat of the nozzle body 12, and a spring 14 that urges the needle 13 in a valve closing direction (lower side in the figure). It has. The piezo element 2 and the engine ECU 40 are connected by lead wires 21 and 22. The charge / discharge of the electric charge of the piezo element 2 is controlled by the engine ECU 40 (electronic control unit). Details of control of the piezo element 2 by the engine ECU 40 will be described later.

  The valve body 31 of the back pressure control mechanism 3 is driven by a piston 32 that moves following the expansion and contraction of the piezo element 2, a disc spring 33 that biases the piston 32 toward the piezo element 2, and a piston 32. A spherical valve element 34 is accommodated.

  The substantially cylindrical injector body 4 has a stepped columnar storage hole 41 extending in the axial direction of the injector at the center in the radial direction. The piezoelectric element 2 and the back pressure control mechanism 3 are provided in the storage hole 41. It is stored. Further, the nozzle 1 is held at the end of the injector body 4 by screwing the substantially cylindrical retainer 5 into the injector body 4.

  The nozzle body 12, the injector body 4 and the valve body 31 are formed with a high pressure passage 6 to which high pressure fuel is always supplied from the common rail, and the injector body 4 and the valve body 31 are connected to a fuel tank (not shown). 7 is formed.

  A high pressure chamber 15 is formed between the outer peripheral surface of the needle 13 on the nozzle hole 11 side and the inner peripheral surface of the nozzle body 12. The high pressure chamber 15 communicates with the nozzle hole 11 when the needle 13 is displaced in the valve opening direction (upper side in the figure). The high pressure chamber 15 is always supplied with high pressure fuel via the high pressure passage 6. A back pressure chamber 16 is formed on the side opposite to the injection hole of the needle 13. In the back pressure chamber 16, the above-described spring 14 is disposed.

  The valve body 31 is formed with a high-pressure seat surface 35 in a path communicating the high-pressure passage 6 in the valve body 31 and the back pressure chamber 16 of the nozzle 1, and the back of the low-pressure passage 7 in the valve body 31 and the nozzle 1. A low-pressure seat surface 36 is formed in a path communicating with the pressure chamber 16. The valve body 34 described above is disposed between the high pressure seat surface 35 and the low pressure seat surface 36.

  In the above configuration, when the piezo element 2 is contracted, the valve body 34 is in contact with the low pressure seat surface 36, the back pressure chamber 16 is connected to the high pressure passage 6, and high pressure fuel pressure is introduced into the back pressure chamber 16. . The needle 13 is urged in the valve closing direction (lower side in the figure) by the fuel pressure in the back pressure chamber 16 and the spring 14 to close the nozzle hole 11.

  At this time, a high fuel pressure is applied to the valve body 34. As a result, a high fuel pressure is applied to the piezo element 2 via the valve body 34 and the piston 32.

  On the other hand, when the electric charge of the piezo element 2 is charged, the piezo element 2 extends in the direction opposite to the direction of the fuel pressure applied to the piezo element 2 (the lower side in the figure). Along with this, the piezo element 2 pushes the valve element 34 downward through the piston 32 in the figure.

  That is, when the electric charge of the piezo element 2 is charged, the piezo element 2 extends against the fuel pressure applied to the piezo element 2 via the valve element 34 and the piston 32.

  Thereafter, the valve body 34 is pushed by the piezo element 2 through the piston 32 and comes into contact with the high-pressure seat surface 35. As a result, the back pressure chamber 16 and the high pressure passage 6 are blocked, the back pressure chamber 16 and the low pressure passage 7 are connected, and the back pressure chamber 16 has a low pressure. Then, the needle 13 is urged by the fuel pressure in the high pressure chamber 15 in the valve opening direction (upper side in FIG. 1) to open the injection hole 11, and fuel is injected from the injection hole 11 into the cylinder of the engine. become.

  Thus, when the piezo element 2 is extended by charging the piezo element 2, the injector 10 is opened and fuel is injected into the cylinder of the engine from the injection hole 11.

  Next, when the electric charge is discharged from the piezo element 2, the piezo element 2 is contracted upward in the drawing. At this time, the valve body 34 is pushed upward in the figure by the fuel pressure in the high pressure passage 6, and the piston 32 moves upward in the figure by the force applied from the valve body 34 and the elastic force of the disc spring 33.

  Thereafter, the valve body 34 comes into contact with the low pressure seat surface 36 and the back pressure chamber 16 is connected to the high pressure passage 6. The high pressure fuel pressure in the high pressure passage 6 is introduced into the back pressure chamber 16. The needle 13 is biased in the valve closing direction (lower side in the figure) by the fuel pressure in the back pressure chamber 16 and the spring 14 to close the nozzle hole 11.

  When the electric charge is discharged from the piezo element 2 in this way, the piezo element 2 is contracted, whereby the injector 10 is closed and fuel injection from the injection hole 11 into the cylinder of the engine is stopped.

  Next, the engine ECU 40 for controlling charging / discharging of the piezo element 2 of the present embodiment will be described. FIG. 2 shows an electronic circuit configuration of the engine ECU 40.

  The engine ECU 40 includes a DC / DC power supply circuit 50, transistors SW1 and SW2, electromagnetic coils 60, voltage dividing circuits 70 and 75, diodes D1 and D2, resistance elements 80 and 81, a voltage sensor 82, a power supply control circuit 83, a comparator 85a, 85b, constant voltage circuits 87a and 87b, charge / discharge control circuit 90, A / D converter 91, microcomputer 93, memory 95, rail pressure sensor 97, and accelerator sensor 98.

  The DC / DC power supply circuit 50 is a circuit that outputs a power supply voltage from its output terminal 50a.

  Specifically, the DC / DC power supply circuit 50 includes an electromagnetic coil 51, a transistor 52, a diode 55, a capacitor 56, and resistance elements 53 and 57.

  The transistor 52 is connected between the power supply and the ground. The electromagnetic coil 51 is connected between the transistor 52 and the power source. The resistance element 53 is connected between the transistor 52 and the ground.

The capacitor 56 is connected between the common connection terminal 50b of the electromagnetic coil 51 and the transistor 52 and the ground. The capacitor 56 is composed of an aluminum electrolytic capacitor.
The diode 55 has its anode terminal connected to the common connection terminal 50 b and the cathode terminal of the diode 55 connected to the positive terminal of the capacitor 56. The diode 55 prevents current from flowing from the capacitor 56 side to the common connection terminal 50b side.

  The output terminal 50 a is configured between the diode 55 and the capacitor 56. The resistance element 57 is connected between the capacitor 56 and the ground.

  The voltage dividing circuit 75 constitutes a second voltage dividing circuit and includes resistance elements R4 and R5. The resistance elements R4 and R5 are connected in series between the output terminal 50a and the ground. The voltage dividing circuit 75 outputs the divided voltage Vb from the common connection terminal 75a of the resistance elements R4 and R5. The divided voltage Vb is a voltage obtained by dividing the power supply voltage by the resistance element R4 on the output terminal 50a side and the resistance element R5 on the ground side among the resistance elements R4 and R5.

  Here, the resistance elements R4 and R5 constituting the voltage dividing circuit 75 are smaller than the resistance values R1, R2 and R3 constituting the voltage dividing circuit 70 between the actual value of the resistance value and the theoretical value of the resistance value. And the change in resistance value due to aging and temperature change is small. The error is caused between the actual value of the resistance value and the theoretical value of the resistance value due to the initial tolerance.

  The divided voltage Vb from the common connection terminal 75a is input to the positive input terminal (+) of the comparator 85a. The output voltage of the constant voltage circuit 87a is input to the negative input terminal (−) of the comparator 85a.

  The constant voltage circuit 87a outputs a reference voltage for comparing the divided voltage Vb from the voltage dividing circuit 75 in order to determine whether or not the power supply voltage has reached a constant voltage Vset (maximum value). The constant voltage circuit 87a constitutes a voltage output circuit described in the claims.

  The comparator 85a is a comparison circuit that outputs one of a high level signal and a low level signal in accordance with a comparison between the divided voltage Vb from the common connection terminal 75a and the output voltage of the constant voltage circuit 87a. The comparator 85a constitutes a comparison circuit described in the claims.

  The output voltage (reference voltage) of the constant voltage circuit 87a is obtained by multiplying a voltage (= Vset−dv) obtained by subtracting a predetermined value dv from a predetermined constant voltage Vset (see FIG. 9) by the voltage dividing ratio of the voltage dividing circuit 75. It is a voltage value.

  Here, assuming that the resistance value r4 of the resistance element R4 is the resistance value r5 of the resistance element R5, the output voltage of the constant voltage circuit 87a is expressed by {(Vset−dv) × r5} / (r4 + r5).

  The divided voltage Vb from the common connection terminal 75a is input to the negative input terminal (−) of the comparator 85b. The output voltage of the constant voltage circuit 87b is input to the positive input terminal (+) of the comparator 85b.

  The comparator 85b is a comparison circuit that outputs one of a high level signal and a low level signal in accordance with a comparison between the divided voltage Vb from the common connection terminal 75a and the output voltage of the constant voltage circuit 87b.

  The constant voltage circuit 87b outputs a reference voltage for comparing the divided voltage Vb from the voltage dividing circuit 75 in order to determine whether or not the power supply voltage has reached a constant voltage Von (minimum value).

  The output voltage of the constant voltage circuit 87b is a voltage value obtained by multiplying a voltage (= Von + dv) obtained by adding a predetermined value dv to a predetermined constant voltage Von (see FIG. 9) and a voltage dividing ratio of the voltage dividing circuit 75.

  Therefore, similarly to the above, when the resistance values of the resistance elements R4 and R5 are r4 and r5, the output voltage of the constant voltage circuit 87b is represented by {(Von + dv) × r5} / (r4 + r5). Become.

  The power supply control circuit 83 is composed of an integrated circuit or the like, controls the transistor 52 in accordance with the output signals of the comparators 85a and 85b, and sends a signal indicating the power supply voltage (hereinafter referred to as a power supply voltage signal SFLG) to the microcomputer 93. Output.

  As the power supply voltage signal SFLG of the present embodiment, a signal that becomes a low level signal when the power supply voltage is lower than the constant voltage Vset and becomes a high level signal when the power supply voltage reaches the constant voltage Vset is used. A specific operation of the power supply control circuit 83 will be described later.

  The transistors SW1 and SW2 are connected in series between the output terminal 50a and the ground.

  The transistor SW1 is disposed on the output terminal 50a side of the transistors SW1 and SW2. As will be described later, the transistor SW1 charges the piezo element 2 in accordance with the power supply voltage output from the output terminal 50a by switching.

  The transistor SW2 is disposed on the ground side of the transistors SW1 and SW2. As will be described later, the transistor SW2 collects the charge stored in the piezo element 2 in the capacitor 56 of the DC / DC power supply circuit 50 by switching.

  Note that the transistors SW1, SW2, and 52 are composed of switching elements such as field effect transistors.

  The diode D1 has an anode terminal connected to the common connection terminal 50c of the transistors SW1 and SW2, and a cathode terminal of the diode D1 connected to the output terminal 50a. Thereby, the diode D1 is connected in parallel to the transistor SW1. As will be described later, the diode D1 bypasses the transistor SW1 and causes a current to flow from the common connection terminal 50c side to the output terminal 50a side.

  The cathode terminal of the diode D2 is connected to the common connection terminal 50c, and the anode terminal of the diode D2 is connected to the ground. As a result, the diode D2 is connected in parallel to the transistor SW2. As will be described later, the diode D2 bypasses the transistor SW2 and causes a current to flow from the ground side to the common connection terminal 50c side.

  The resistance element 81 is connected between the transistor SW2 and the ground. The resistance element 81 limits the current flowing through the transistor SW2 and the like. The electromagnetic coil 60 is connected between the common connection terminal 50c of the transistors SW1 and SW2 and the ground.

  The resistance element 80 is connected between the electromagnetic coil 60 and the ground. The voltage sensor 82 detects a voltage between one terminal and the other terminal of the resistance element 80. The piezo element 2 is connected between the electromagnetic coil 60 and the resistance element 80.

  The resistance element 80 and the voltage sensor 82 constitute a current detection unit that detects a current flowing through the piezo element 2.

  As will be described later, the charge / discharge control circuit 90 is instructed by the microcomputer 93 and controls the transistors SW1 and SW2 to charge the piezo element 2 and discharge the charge from the piezo element 2.

  The charge / discharge control circuit 90 is composed of an integrated circuit or the like. The charge / discharge control circuit 90 constitutes the charge control circuit described in the claims.

  The voltage dividing circuit 70 constitutes a first voltage dividing circuit and includes resistance elements R1, R2, and R3. The resistance elements R1, R2, and R3 are connected in series between the output terminal 50a and the ground. The voltage dividing circuit 70 generates a divided voltage Va from the common connection terminal 70a of the resistance elements R2 and R3. The divided voltage Va is a voltage obtained by dividing the power supply voltage by the resistance elements R1, R2 on the output terminal 50a side and the resistance element R3 on the ground side among the resistance elements R1, R2, R3.

  If the power supply voltage is Vdc and the resistance values of the resistance elements R1, R2, and R3 are r1, r2, and r3, the divided voltage Va can be expressed as (Vdc × r3) / (r1 + r2 + r3).

  The A / D converter 91 performs analog / digital conversion on the divided voltage Va and outputs a digital signal.

  The rail pressure sensor 97 is a pressure sensor that detects the pressure in the common rail 15. That is, the rail pressure sensor 97 detects the pressure of fuel supplied from the common rail 15 to the injector 10 (that is, fuel pressure). The accelerator sensor 98 detects the depression angle of the accelerator pedal that is depressed by the driver's foot.

  The microcomputer 93 executes a computer program, and with the execution of the computer program, an output signal of the A / D converter 91, an output signal of an engine speed sensor (not shown) for detecting the speed of the diesel engine, The injector 10 is controlled via the charge / discharge control circuit 90 based on the output signals of the sensors 97 and 98.

  The memory 95 includes a DRAM, a flash memory, and the like, and stores a computer program, and stores data as the microcomputer 93 executes the computer program.

  Next, the operation of this embodiment will be described.

  First, prior to the description of the control processing executed by the microcomputer 93, the operation of the DC / DC power supply circuit 50 and the power supply control circuit 83 will be described.

  First, the power supply voltage output from the output terminal 50a of the DC / DC power supply circuit 50 decreases due to the natural discharge of the capacitor 56 and the discharge from the capacitor 56 accompanying the switching of the transistor SW1.

  When the power supply voltage decreases and reaches the voltage Von (minimum value), the divided voltage Vb from the common connection terminal 75a becomes lower than the output voltage of the constant voltage circuit 87b.

  Along with this, the output signal of the comparator 85b changes from a high level signal to a low level signal. Thus, when the low level signal output from the comparator 85 b is input to the power supply control circuit 83, the power supply control circuit 83 starts switching of the transistor 52.

  Here, when the transistor 52 is on, a current flows from the power source through the electromagnetic coil 51 and the transistor 52 to the ground through the resistance element 53. Along with this, energy is stored in the electromagnetic coil 51 by the current flowing into the electromagnetic coil 51 from the power source.

  On the other hand, when the transistor 52 is turned off, a current flows from the electromagnetic coil 51 side to the capacitor 56 through the diode 55 based on the energy. As a result, energy is stored in the capacitor 56.

  Thereafter, when the transistor 52 is turned on, a current flows from the power source through the electromagnetic coil 51 and the transistor 52 to the ground through the resistance element 53, and energy is stored in the electromagnetic coil 51 by this current.

  Thus, when the transistor 52 is repeatedly turned on and off, the energy stored in the capacitor 56 increases. Along with this, the power supply voltage output from the output terminal 50a rises and reaches the voltage Vset (maximum value).

  At this time, the divided voltage Vb from the common connection terminal 75a becomes higher than the output voltage of the constant voltage circuit 87a. Along with this, the output signal of the comparator 85a changes from the low level signal to the high level signal. Thus, when the high level signal output from the comparator 85 a is input to the power supply control circuit 83, the power supply control circuit 83 stops switching of the transistor 52.

  Thereafter, when the power supply voltage output from the output terminal 50a decreases to reach the voltage Von, the power supply control circuit 83 starts switching of the transistor 52 as described above. For this reason, accumulation of energy in the capacitor 56 is started, and the power supply voltage output from the output terminal 50a increases.

  Thus, the switching of the transistor 52 is started and stopped according to the power supply voltage output from the output terminal 50a. As a result, the power supply voltage output from the output terminal 50a is maintained at a voltage value not less than the voltage Von (minimum value) and not more than the voltage Vset (maximum value).

  Next, control processing executed by the microcomputer 93 of this embodiment will be described.

  The microcomputer 93 determines the valve opening timing for opening the injector 10 and the valve closing timing for closing the injector 10 according to the output signal of the engine speed sensor and the output signals of the sensors 97 and 98, respectively. In addition to this, the charge / discharge control circuit 90 is commanded to open the injector 10 at the valve opening timing, and the charge / discharge control circuit 90 is commanded to close the injector 10 at the valve closing timing.

  Hereinafter, (1) when the microcomputer 93 instructs the charge / discharge control circuit 90 to open the injector 10, (2) separately when the charge / discharge control circuit 90 is commanded to close the injector 10. explain.

  (1) The case where the microcomputer 93 instructs the charge / discharge control circuit 90 to open the injector 10 will be described.

  First, the microcomputer 93 performs power supply voltage calculation processing for calculating the actual value Vdet ′ of the power supply voltage output from the output terminal 50a of the DC / DC power supply circuit 50, and charging according to the actual value Vdet ′ of the power supply voltage. A charge control process for controlling the discharge control circuit 90 is executed. Hereinafter, the power supply voltage calculation process and the charge control process will be described separately.

(Power supply voltage calculation processing)
The microcomputer 93 executes power supply voltage calculation processing according to the flowchart of FIG.

  First, in step S100, the theoretical value Vdet of the power supply voltage output from the output terminal 50a of the DC / DC power supply circuit 50 is calculated.

  Specifically, a digital signal output from the A / D converter 91 (hereinafter referred to as a digital signal Vod) is acquired, and the acquired digital signal Vod is divided by the theoretical value kb of the voltage division ratio to obtain a theoretical power supply voltage. The value Vdet (= Vod / kb) is calculated.

  Here, the theoretical value kb of the voltage division ratio is data set based on the resistance values of the resistance elements R1, R2, and R3, and is stored in the memory 95 in advance. The theoretical value kb of the voltage dividing ratio is represented by {r3 / (r1 + r2 + r3)} as the theoretical value kb of the voltage dividing ratio when the resistance values of the resistance elements R1, R2, and R3 are r1, r2, and r3, respectively. Value.

  Note that step S100 constitutes the second calculating means described in the claims.

  In the next step S101, the average correction coefficient k is called from the memory 95. The average correction coefficient k is a coefficient for calculating the actual value Vdet 'of the power supply voltage based on the theoretical value Vdet of the power supply voltage, and is stored in the memory 95 when the engine ECU 40 is manufactured, as will be described later.

  In the next step S102, the actual value Vdet '(= Vdet × k) of the power supply voltage is calculated by multiplying the theoretical value Vdet of the power supply voltage by the average correction coefficient k. Accordingly, the actual value Vdet 'of the power supply voltage is obtained by correcting the theoretical value Vdet of the power supply voltage.

  Step S102 constitutes a third calculation means described in the claims.

  Next, in step S103, an emission charge amount correction coefficient P is calculated based on the actual value Vdet 'of the power supply voltage. As will be described later, the charge amount correction coefficient P obtains a target charge amount that needs to be discharged from the DC / DC power supply circuit 50 and stored in the piezo element 2 in order to store the target value energy in the piezo element 2. Used when.

  Here, the emission charge amount correction coefficient P and the actual value Vdet 'of the power supply voltage are in a one-to-one relationship. As the emission charge amount correction coefficient P, a smaller value is used as the actual value Vdet 'of the power supply voltage increases.

(Charge control process)
The microcomputer 93 executes the charge control process according to the flowchart of FIG.

  First, in step S110, a detection value (that is, rail pressure) of the rail pressure sensor 97 is acquired. Next, in step S111, the target value of energy that needs to be stored in the piezo element 2 when the injector 10 is opened is calculated based on the detected value of the rail pressure sensor 97 and the graph Ga in FIG. To do.

  The graph Ga in FIG. 5 is stored in the memory 95 in advance. The vertical axis represents the target value of energy (denoted as target En in the figure), the horizontal axis represents the rail pressure, and the rail pressure and the target value of energy. Data indicating the relationship.

  The target value of energy and the rail pressure are set so as to be specified on a one-to-one basis. As the target value of energy, a larger value is set as the rail pressure increases, and a smaller value is set as the target value of energy as the rail pressure decreases.

  Here, the reason why the relationship between the target value of energy and the rail pressure is as shown in the graph Ga of FIG. 5 is as follows.

  That is, in the state where the injector 10 is closed, the fuel pressure is applied to the piezo element 2 as described above. When the injector 10 opens, it is necessary to stretch the piezo element 2 against the fuel pressure applied to the piezo element 2. For this reason, as the rail pressure increases, a larger value is required as energy required to stretch the piezo element 2.

  Here, the energy stored in the piezo element 2 is determined by the product (= Q × Vdc) of the charge amount Q stored in the piezo element 2 and the power supply voltage Vdc.

  Therefore, in the present embodiment, in order to store the energy of the target value in the piezo element 2, the target charge amount (hereinafter referred to as the target discharge charge amount) that needs to be discharged from the DC / DC power supply circuit 50 and stored in the piezo element 2. Qt) is obtained in the next steps S112 and S113.

  First, the target emission charge amount Qt varies depending on the power supply voltage even if the target value of energy is a constant value.

  For example, when the target value of energy is constant, the target emission charge amount Qt increases as the power supply voltage decreases, and the target emission charge amount Qt decreases as the power supply voltage increases.

  Then, in step S112, assuming that the power supply voltage is a predetermined constant value Vs, in order to store the energy of the target value in the piezo element 2, it is discharged from the DC / DC power supply circuit 50 to the piezo element 2. The amount of charge that needs to be stored (hereinafter, the reference emission amount is referred to as Qbase) is determined.

  Here, the reference emission charge amount Qbase is determined by data stored in the memory 95 in advance. In the data, the reference emission charge amount Qbase increases as the energy target value increases, and the reference emission charge amount Qbase and the energy target value are specified one-to-one.

  Next, in step S113, the target emission charge amount Qt (= Qbase × P) is calculated by multiplying the reference emission charge amount Qbase by the emission charge amount correction coefficient P. Note that step S113 constitutes the target charge amount calculation means described in the claims.

  The emission charge amount correction coefficient P is a coefficient for correcting the reference emission charge amount Qbase so that the reference emission charge amount Qbase corresponds to the actual value Vdet 'of the power supply voltage. As described above, a smaller value is used as the emission charge amount correction coefficient P as the actual value Vdet 'of the power supply voltage increases.

  The target emission charge amount Qt obtained in this way is a target charge amount corresponding to the actual value Vdet 'of the power supply voltage, and a larger value is set as the rail pressure increases.

  In the next step S114, the target discharge amount Qt is transmitted to the charge / discharge control circuit 90.

  Thereafter, in step S115, the charge / discharge control circuit 90 is instructed to charge the piezoelectric element 2 with the charge of the target discharge amount Qt. That is, a command is issued to open the injector 10 based on the target discharge amount Qt.

  Then, the charge / discharge control circuit 90 starts switching of the transistor SW1 with the transistor SW2 of FIG. 2 turned off.

  In addition to this, the charge / discharge control circuit 90 obtains the amount of charge Qp released from the DC / DC power supply circuit 50 to the piezo element 2 after the switching of the transistor SW1 is started, and the transistor SW1 is controlled according to the amount of charge Qp. Decide whether to continue or stop switching.

  Specifically, the charge / discharge control circuit 90 integrates the current i flowing through the resistance element 80 (that is, the piezo element 2) at the time t when the transistor SW1 is turned on after the start of switching of the transistor SW1, and the integrated value ( ∫idt) is obtained as the charge amount Qp. The current i is a value (= V / r) obtained by dividing the detection value V of the voltage sensor 82 by the resistance value r of the resistance element 80.

  As described above, the amount of charge excluding the amount of charge stored in the piezo element 2 when the transistor SW1 is turned off from the amount of charge stored in the piezo element 2 after the start of switching of the transistor SW1 is obtained as the charge amount Qp.

  Then, the charge / discharge control circuit 90 continues switching of the transistor SW1 until the charge amount Qp thus determined reaches the target discharge amount Qt.

  Here, when the transistor SW1 is switched with the transistor SW2 turned off, energy is stored in the piezo element 2 as follows.

  First, when the transistor SW1 is on, the current from the output terminal 50a of the DC / DC power supply circuit 50 flows to the ground through the transistor SW1, the electromagnetic coil 60, the piezo element 2, and the resistance element 80. Thus, energy is stored in the electromagnetic coil 60 by the current flowing from the output terminal 50a, and energy is stored in the piezo element 2.

  On the other hand, when the transistor SW1 is turned off, a current flows from the resistance element 81 side to the ground through the diode D2, the electromagnetic coil 60, the piezo element 2, and the resistance element 80 based on the energy stored in the electromagnetic coil 60. As a result, energy is stored in the piezo element 2 based on the energy stored in the electromagnetic coil 60.

  When the charge / discharge control circuit 90 determines that the charge amount Qp is less than the target discharge amount Qt, the charge / discharge control circuit 90 continues switching of the transistor SW1. Thereby, charging of the electric charge to the piezo element 2 is continued, and the energy stored in the piezo element 2 is increased.

  Thereafter, the charge stored in the piezoelectric element 2 reaches the target emission charge amount Qt. Then, the piezo element 2 extends against the fuel pressure applied to the piezo element 2 via the valve body 34 and the piston 32. For this reason, as described above, the valve body 34 is pushed by the piezo element 2 through the piston 32 and comes into contact with the high-pressure seat surface 35.

  As a result, the back pressure chamber 16 and the low pressure passage 7 are connected, and the back pressure chamber 16 has a low pressure. Then, the needle 13 is urged in the valve opening direction (upper side in FIG. 1) by the fuel pressure in the high pressure chamber 15 to open the nozzle hole 11. That is, the injector 10 opens and fuel is injected from the injection hole 11 into the cylinder of the engine.

  On the other hand, when the charge amount Qp reaches the target discharge amount Qt, the charge / discharge control circuit 90 determines that the energy released from the DC / DC power supply circuit 50 to the piezo element 2 has reached the target value, and the transistor SW1. Stops continuation of switching. Then, the state where the injector 10 is opened is maintained.

  (2) A case where the microcomputer 93 instructs the charge / discharge control circuit 90 to close the injector 10 will be described.

  First, the microcomputer 93 instructs the charge / discharge control circuit 90 to close the injector 10.

  Then, the charge / discharge control circuit 90 starts switching of the transistor SW2 with the transistor SW1 turned off in order to release the electric charge from the piezo element 2.

  First, when the transistor SW2 is turned on, a current flows from the resistance element 80 side to the resistance element 81 side through the piezo element 2, the electromagnetic coil 60, and the transistor SW2 based on the electric charge (that is, energy) stored in the piezo element 2. . Accordingly, energy is stored in the electromagnetic coil 60 by the current flowing from the piezoelectric element 2 side to the electromagnetic coil 60 side.

  Next, when the transistor SW2 is turned off, a current flows from the resistance element 80 side to the capacitor 56 through the piezoelectric element 2, the electromagnetic coil 60, and the diode D1 based on the energy stored in the electromagnetic coil 60. Therefore, electric charge (energy) is stored in the capacitor 56 by the current flowing from the resistance element 80 side and through the diode D1 to the capacitor 56.

  When the transistor SW2 is repeatedly turned on and off in this way, the energy stored in the piezo element 2 is released, and a part of the released energy is recovered by the capacitor 56.

  Thereafter, when the electric charge is discharged from the piezo element 2 by switching of the transistor SW2, the current flowing to the piezo element 2 side through the resistance element 80 becomes small, and the current becomes less than a predetermined value. Then, the charge / discharge control circuit 90 determines that the charge of the target emission charge amount Qt is released from the piezo element 2, and stops switching of the transistor SW2.

  On the other hand, when the charge of the target emission charge amount Qt is released from the piezo element 2, the piezo element 2 contracts to the state shown in FIG.

  At this time, the piston 32 moves together with the valve body 34 to the upper side in the figure by the fuel pressure applied via the valve body 34 and the elastic force of the disc spring 33. Accordingly, the valve body 34 comes into contact with the low pressure seat surface 36.

  Then, the back pressure chamber 16 is connected to the high pressure passage 6, and high pressure fuel pressure is introduced into the back pressure chamber 16. The needle 13 is urged in the valve closing direction (lower side in FIG. 1) by the fuel pressure in the back pressure chamber 16 and the spring 14 to close the nozzle hole 11. That is, the injector 10 is closed.

  Next, a correction coefficient calculation process for calculating the above-described average correction coefficient k will be described with reference to FIG. FIG. 6 is a flowchart showing the correction coefficient calculation process.

  The correction coefficient calculation process is executed by the microcomputer 93 when the engine ECU 40 is manufactured. That is, when the engine ECU 40 is manufactured, when a battery is connected to the engine ECU 40 and power supply to the engine ECU 40 is started, the microcomputer 93 starts executing the correction coefficient calculation process according to the flowchart shown in FIG. .

  Here, the power supply voltage Vdc output from the DC / DC power supply circuit 50 decreases due to natural discharge of the capacitor 50a. Therefore, during the correction coefficient calculation process, as described above, the power supply control circuit 83 controls the transistor 52 of the DC / DC power supply circuit 50 so that the power supply voltage Vdc is as shown in FIG. The value is between the voltage Vset and the voltage Von. FIG. 7B is a timing chart of the power supply voltage Vdc with the vertical axis representing voltage and the horizontal axis representing time.

  Hereinafter, the correction coefficient calculation process will be described.

  First, in step S300 of FIG. 6, the count value n is set to 1 (n = 1). The count value n is the number of times of calculating a correction coefficient k (n) described later.

  Next, in step S301, it is determined whether or not the signal level of the power supply voltage signal SFLG input from the power supply control circuit 83 to the microcomputer 93 has changed from a low level to a high level (denoted as SFLG = 1 in FIG. 6). .

  Here, as shown in FIGS. 7A and 7B, the power supply control circuit 83 sets the signal level of the power supply voltage signal SFLG to a low level (in FIG. 7) every time a high level signal is input from the comparator 85a. The level is changed from “Lo” to high level (indicated as “Hi” in FIG. 7). FIG. 7A is a timing chart of the power supply voltage signal SFLG with the vertical axis representing the signal level and the horizontal axis representing time. As described above, the comparator 85a changes the signal level of the output signal from the low level to the high level every time the power supply voltage Vdc reaches the constant voltage Vset.

  In step S301, when a low level signal as the power supply voltage signal SFLG is input from the power supply control circuit 83, it is determined as NO because the power supply voltage Vdc is less than the constant voltage Vset. Step S301 constitutes the determination means described in the claims.

  Thereafter, the determination in step S301 is repeated until a high level signal as the power supply voltage signal SFLG is input from the power supply control circuit 83. When power supply voltage Vdc reaches constant voltage Vset and a high level signal as power supply voltage signal SFLG is input from power supply control circuit 83, YES is determined in step S301.

  That is, in step S301, it is determined that the power supply voltage Vdc has reached the constant voltage Vset based on the high level signal output from the comparator 85a when the power supply voltage Vdc has reached the constant voltage Vset.

  In the next step S302, an actual value kb 'of the voltage dividing ratio of the voltage dividing circuit 70 is obtained. Specifically, the digital signal output from the A / D converter 91 is acquired. The digital signal is a signal indicating the divided voltage Va output from the common connection terminal 70 a of the voltage dividing circuit 70. Then, the divided voltage Va is divided by the constant voltage Vset, and the divided value (= Va / Vset) is set as the actual value kb ′ of the voltage dividing ratio. Step S302 constitutes a partial pressure ratio calculation means described in the claims.

  In the next step S303, the correction coefficient k (n) is calculated using the actual value kb 'of the voltage division ratio.

  Specifically, the reciprocal number (= 1 / kb ′) of the actual value kb ′ of the voltage dividing ratio is obtained, and this reciprocal number is multiplied by the theoretical value kb of the voltage dividing ratio of the voltage dividing circuit 70 to obtain the multiplied value (= kb / Let kb ′) be the correction coefficient k (n). The theoretical value kb of the voltage dividing ratio of the voltage dividing circuit 70 is a value represented by {r3 / (r1 + r2 + r3)} as described above.

  Step S303 constitutes the first calculation means described in the claims, and Steps S303, S306, S100, and S102 constitute the power supply voltage calculation means recited in the claims.

  In the next step S304, the count value n is incremented to set the count value n to 2 (n = n + 1).

  In the next step S305, it is determined whether or not the count value n is 2. When the count value n is 2, it determines with YES and returns to step S301.

  Therefore, the determination in step S301 is repeated until a high level signal as the power supply voltage signal SFLG is input from the power supply control circuit 83.

  Thereafter, when the power supply voltage reaches the voltage Vset (maximum value) and a high level signal as the power supply voltage signal SFLG is input from the power supply control circuit 83 to the microcomputer 93, YES is determined in step S301.

  In the next step S302, the actual value kb 'of the voltage dividing ratio of the voltage dividing circuit 70 is obtained again (hereinafter referred to as the actual value kb' of this time). Next, in step S303, the correction coefficient k (n + 1) is calculated using the actual value kb 'of this time.

  In the next step S304, the count value n is incremented to set the count value n to 3 (n = n + 1).

  In the next step S305, it is determined whether or not the count value n is 2. At this time, since the count value n is 3, it is determined as NO.

  Then, the process proceeds to the next step S306, where the average value (= {(k (n) + k (n + 1)} / 2) of the correction coefficient k (n) and the correction coefficient k (n + 1) calculated in step S303 described above. ) And the average value ({(k (n) + k (n + 1)} / 2) is used as the average correction coefficient k. Note that step S306 constitutes the average calculation means described in the claims. ing.

  Thereafter, the average correction coefficient k is stored in the memory 95 in step S307. As described above, the average correction coefficient k is used to calculate the actual value Vdet 'of the power supply voltage.

  According to the present embodiment described above, every time the power supply voltage Vdc reaches the maximum value Vset of the output range of the DC / DC power supply circuit 50 in the engine ECU 40, the power supply control circuit 83 causes the high voltage as the power supply voltage signal SFLG. Output level signal. The microcomputer 93 obtains a digital signal output from the A / D converter 91 every time a high level signal as the power supply voltage signal SFLG is inputted from the power supply control circuit 83, and every time the acquisition is performed, the actual voltage dividing ratio is obtained. Value kb ′ (= Va / Vset) is calculated based on the digital signal. In addition to this, every time a digital signal is acquired, the correction coefficients k (n) and k (n + 1) are calculated based on the actual value kb ′ of the voltage division ratio and the average of the correction coefficients k (n) and k (n + 1). The value is calculated as an average correction coefficient k, and the average correction coefficient k is stored in the memory 95.

  On the other hand, when the microcomputer 93 instructs the charge / discharge control circuit 90 to open the injector 10, the average correction coefficient k is called from the memory 95, and the theoretical value Vdet of the power supply voltage is set to the called average correction coefficient k. To calculate an actual value Vdet ′ of the power supply voltage. In addition to this, the microcomputer 93 calculates the target discharge amount Qt that needs to be stored in the piezo element 2 in order to store the energy of the target value in the piezo element 2 based on the actual value Vdet ′ of the power supply voltage. To do. When instructed by the microcomputer 93 to open the injector 10, the charge / discharge control circuit 90 starts switching of the transistor SW1 with the transistor SW2 turned off. Along with this, the current i flowing through the resistance element 57 is integrated at time t, and the integrated value (∫idt) is obtained as the charge amount Qp released from the DC / DC power supply circuit 50 to the piezo element 2. The switching of the transistor SW1 is continued until Qp reaches the target emission charge amount Qt. As a result, the energy stored in the piezo element 2 can be brought close to the target value.

  In the present embodiment, the target value of energy stored in the piezo element 2 is set to a larger value as the rail pressure increases.

For example, it may be possible to set the target value to a constant value regardless of the rail pressure.
Even when the rail pressure reaches the maximum value, the piezo element 2 needs to be stretched against the fuel pressure. Therefore, it is necessary to set a large value as the target value. Therefore, even if the rail pressure is a small value, it is necessary to store large energy (charge amount) in the piezo element 2. For this reason, large power consumption occurs in the DC / DC power supply circuit 50.

  On the other hand, in the present embodiment, as described above, the target value of the energy stored in the piezo element 2 varies depending on the rail pressure, so that the power consumption generated in the DC / DC power supply circuit 50 can be suppressed.

  In the present embodiment, the actual value Vdet ′ of the power supply voltage is calculated by multiplying the average correction coefficient k, which is the average value of the correction coefficients k (n) and k (n + 1), by the theoretical value Vdet of the power supply voltage.

  Here, it is also conceivable to calculate an actual value Vdet ′ (= k (n) × Vdet) of the power supply voltage by multiplying the correction value k (n) instead of the average correction coefficient k by the theoretical value Vdet of the power supply voltage. .

  However, electromagnetic noise is generated by switching of the transistor 52. For this reason, a large error may be included in the digital signal output from the A / D converter 91 due to electromagnetic noise.

  On the other hand, the correction coefficient k (n) is a value calculated based on the digital signal output from the A / D converter 91 as described above. For this reason, the accuracy of calculation of the correction coefficient k (n) is lowered due to electromagnetic noise, and the accuracy of calculation of the actual value Vdet 'of the power supply voltage may be deteriorated.

  On the other hand, in the present embodiment, as described above, since the average correction coefficient k which is the average value of the correction coefficients k (n) and k (n + 1) is used, the accuracy of the actual value Vdet ′ of the power supply voltage is deteriorated. Can be suppressed.

  In the present embodiment, as described above, the resistance elements R4 and R5 that constitute the voltage dividing circuit 75 are compared with the resistance elements R1, R2, and R3 that constitute the voltage dividing circuit 70. The error between this value and the theoretical value is small, and the change in resistance value due to aging is small.

  Therefore, the comparator 85a can accurately output a high-level signal indicating that the power supply voltage has reached the voltage Vset when the power supply voltage has reached the voltage Vset (maximum value). Then, as described above, the power supply control circuit 83 changes the signal level of the power supply voltage signal SFLG from the low level to the high level every time the high level signal is input from the comparator 85a.

  As described above, the microcomputer 93 can determine with high accuracy whether or not the power supply voltage has reached the voltage Vset in accordance with the divided voltage output from the voltage dividing circuit 75.

(Other embodiments)
In the above-described embodiment, an example in which the microcomputer 93 executes the correction coefficient calculation process of FIG. 6 at the time of manufacturing the engine ECU 40 has been shown. Instead, the microcomputer 93 of FIG. Correction coefficient calculation processing may be executed.

  Here, the resistance values of the resistance elements R1, R2, and R3 constituting the voltage dividing circuit 70 also vary depending on temperature change and aging (that is, time passage). For this reason, the voltage dividing ratio of the voltage dividing circuit 70 also changes due to temperature changes and aging deterioration.

  On the other hand, as described above, if the microcomputer 93 executes the correction coefficient calculation process of FIG. 6 after the engine ECU 40 is mounted on the vehicle, the actual value kb ′ of the partial pressure ratio corresponding to the temperature change and the aging deterioration can be accurately obtained. Can be sought. Accordingly, the actual value Vdet 'of the power supply voltage corresponding to the temperature change and aging deterioration can be calculated with high accuracy.

  In the above-described embodiment, the actual value Vdet ′ of the power supply voltage is calculated by multiplying the theoretical value Vdet of the power supply voltage by the average correction coefficient k that is an average value of the correction coefficients k (n) and k (n + 1). However, the present invention is not limited to this, and the actual value Vdet ′ of the power supply voltage may be calculated by multiplying the theoretical value Vdet of the power supply voltage by the correction coefficient k (n).

  In the above-described embodiment, the example in which the average correction coefficient k is calculated using the two correction coefficients k (n) and k (n + 1) is shown, but the present invention is not limited to this, and the average is calculated using three or more correction coefficients. The correction coefficient k may be calculated.

1 nozzle 2 piezo element 10 injector 15 common rail 40 engine ECU
50 DC / DC power supply circuit SW1 transistor SW2 transistor 60 electromagnetic coil 70 voltage dividing circuit 75 voltage dividing circuit D1 diode D2 diode 80 resistance element 81 resistance element 82 voltage sensor 83 power supply control circuit 85a comparator 85b comparator 87a constant voltage circuit 87b constant voltage circuit 90 charge / discharge control circuit 91 A / D converter 93 microcomputer 95 memory 97 rail pressure sensor 98 accelerator sensor

Claims (9)

It has a piezo element (2) that extends due to charge charging, and the pressure of the high-pressure fuel supplied from the common rail (15) is applied to the piezo element (2), and the piezo element ( 2) an electronic control device for controlling an injector (10) that opens when the valve extends to eject the high-pressure fuel;
A power supply circuit (50) having an output terminal (50a) for outputting a power supply voltage;
A power supply control circuit (83) for controlling the power supply circuit so that the power supply voltage falls within a certain range;
A plurality of resistance elements (R1, R2, R3) connected in series between the output terminal (50a) and the ground, and a voltage between any two resistance elements among the plurality of resistance elements; A first voltage dividing circuit (70) that outputs a divided voltage (Va);
A switching element (SW1) disposed between the output terminal (50a) and the piezo element (2);
An electromagnetic coil (60) disposed between the switching element (SW1) and the piezoelectric element (2);
The switching element (SW1) is controlled to be switched according to the divided voltage (Va), and the piezoelectric element (60) is switched from the electromagnetic coil (60) side based on the power supply voltage when the switching element is switched. 2) a charge control circuit (90) for charging the piezo element (2) with current flowing in the current;
Determining means (S301) for determining whether or not the power supply voltage has reached a maximum value (Vset) in the certain range;
When the determination means (S301) determines that the power supply voltage (Vdc) has reached the maximum value (Vset), the divided voltage (Va) is acquired, and the acquired divided voltage is set to the maximum value (Vset). A voltage dividing ratio calculating means (S302) for calculating a value (Va / Vset) divided by the value as an actual value (kb ') of the voltage dividing ratio of the first voltage dividing circuit; Control device.   The divided voltage (Va) is acquired, and the first voltage is set based on the acquired divided voltage (Va) and each resistance value of the plurality of resistance elements (R1, R2, R3). Based on the theoretical value (kb) of the voltage dividing ratio of the voltage dividing circuit (70) and the actual value (kb ′) of the voltage dividing ratio calculated by the voltage dividing ratio calculating means (S302), The electronic control device according to claim 1, further comprising power supply voltage calculation means (S303, S306, S100, S102) for calculating a value (Vdet '). The voltage dividing ratio calculation means (S302) is output from the common connection terminal (70a) every time the determination means (S301) determines that the power supply voltage (Vdc) has reached the maximum value (Vset). The divided voltage (Va) is acquired, and the actual value (kb ′) of the voltage dividing ratio is repeatedly calculated for each acquisition,
The power supply voltage calculation means (S303, S306, S100, S102)
First calculation means for repeatedly calculating a value (k (n), k (n + 1)) obtained by dividing the theoretical value (kb) of the voltage division ratio by the actual value (kb ′) of the voltage division ratio for each acquisition. (S303),
Average calculating means (S306) for calculating an average value of the values (k (n), k (n + 1)) calculated for each acquisition by the first calculating means;
The divided voltage (Va) output from the common connection terminal (70a) is acquired, and the acquired divided voltage is divided by the theoretical value (kb) of the voltage dividing ratio to obtain a theoretical value ( Second calculating means (S100) for calculating Vdet);
The actual value (Vdet ′) of the power supply voltage is calculated by multiplying the theoretical value (Vdet) of the power supply voltage calculated by the second calculation means by the average value (k) calculated by the average calculation means. The electronic control device according to claim 2, further comprising third calculation means (S102). Current detection means (80, 82) for detecting a current flowing through the piezo element (2);
Based on the current detected by the current detection means (80, 82) and the actual value (Vdet ′) of the power supply voltage, the charge control circuit (90) calculates energy stored in the piezo element (2). The electronic control device according to claim 2 or 3, wherein the switching element (SW1) is controlled so as to approach a target value. Based on the actual value (Vdet ′) of the power supply voltage, the target charge amount (Qt) that needs to be stored in the piezoelectric element (2) in order to store the energy of the target value in the piezoelectric element (2). A target charge amount calculating means (S113) for calculating,
The charge control circuit (90) is discharged from the power supply circuit to the piezo element (2) after the switching of the switching element (SW1) is started based on the current detected by the current detection means (80, 82). The charge amount is calculated, and the switching of the switching element (SW1) is continued until the calculated charge amount reaches the target charge amount (Qt) calculated by the target charge amount calculation means. Item 5. The electronic control device according to Item 4. A pressure sensor (97) for detecting the pressure of the high-pressure fuel supplied from the common rail (15) to the injector (10);
6. The electronic control according to claim 5, wherein the target charge amount calculation means (S113) sets the target charge amount (Qt) to a larger value as the detected pressure of the pressure sensor (97) increases. apparatus. A plurality of resistance elements (R4, R5) connected in series between the output terminal (50a) and the ground, and between any two resistance elements among the plurality of resistance elements (R4, R5). A second voltage dividing circuit (75) that outputs the voltage of
A voltage output circuit (87a) for outputting a reference voltage for comparing the divided voltage from the second voltage dividing circuit in order to determine whether or not the power supply voltage has reached the maximum value;
When the divided voltage from the second voltage dividing circuit becomes higher than the reference voltage output from the voltage output circuit, the power supply voltage reaches the maximum value, assuming that the power supply voltage reaches the maximum value. A comparison circuit (85a) for outputting a signal indicating that the object has been reached,
The determination means (S301) determines the maximum value (based on an output signal output from the comparison circuit (85a) when the divided voltage from the second voltage dividing circuit becomes higher than the reference voltage. The electronic control device according to claim 1, wherein it is determined that the power supply voltage has reached Vset).   The plurality of resistance elements (R4, R5) constituting the second voltage dividing circuit (75) are compared with the plurality of resistance elements (R1, R2, R3) constituting the first voltage dividing circuit (70). The electronic control device according to claim 7, wherein an error between an actual resistance value and a theoretical resistance value is small, and a change in the resistance value due to aging is small. A cathode (D2) having a cathode terminal connected to the switching element side terminal and an anode terminal connected to the ground side of the electromagnetic coil (60);
When the charging control circuit (90) switches the switching element (SW1), when the switching element (SW1) is on, the switching element (SW1) and the electromagnetic coil from the output terminal (50a) When energy is stored in the electromagnetic coil (60) by the current flowing through the piezo element (2) through (60) and the piezo element (2) is charged, and the switching element (SW1) is off. Based on the energy stored in the electromagnetic coil (60), the piezoelectric element is charged with a current flowing from the ground side through the diode (D2) and the electromagnetic coil (60) to the piezoelectric element (2). 9. The electronic control device according to claim 1, wherein

Images