AU2011284466B2

AU2011284466B2 - Fuel injection control device and method for an internal combustion engine of a vehicle

Info

Publication number: AU2011284466B2
Application number: AU2011284466A
Authority: AU
Inventors: Nobuyuki Aoki; Yoshiyasu Ito; Shinichi Kusakabe; Shinichiro Yoshitaki
Original assignee: Toyota Industries Corp; Toyota Motor Corp
Current assignee: Toyota Industries Corp; Toyota Motor Corp
Priority date: 2010-06-22
Filing date: 2011-06-14
Publication date: 2014-11-13
Anticipated expiration: 2031-06-14
Also published as: JP5204156B2; AU2011284466A1; JP2012007488A; WO2012014034A1; RU2012155497A; RU2542333C2; ZA201209532B; EP2585702A1

Abstract

An electronic control unit (10) is applied to a diesel engine equipped with two drive circuits (11 and 12), each of which drives an injector (INJ1 - INJ8) to change an amount of driving energy applied to the injector on the basis of an engine operating state. At the time of changing the amount of driving energy, the electronic control unit (10) causes the drive circuit (11, 12) that is executing fuel injection to accomplish the fuel injection at the pre-changed amount of driving energy, and changes the amount of driving energy of the drive circuit (11, 12) that is not executing fuel injection. With a fuel injection control device for an internal combustion engine, equipped with the electronic control unit (10), it is possible to change the amounts of driving energy for driving the two drive circuits (11, 12) without any deviation of the fuel injection amount.

Description

WO 2012/014034 PCT/IB2011/001668 1 FUEL INJECTION CONTROL DEVICE AND METHOD FOR AN INTERNAL COMBUSTION ENGINE OF A VEHICLE 5 BACKGROUND OF THE INVENTION 1. Field of the Invention [00011 The invention relates to a fuel injection control device and fuel injection control method for an internal combustion engine, which change an amount of driving 10 energy applied to an injector on the basis of an engine operating state, and a vehicle equipped with the fuel injection control device. 2. Description of Related Art [0002] In a recent diesel engine, so-called multi-stage injection control is 15 executed. The multi-stage injection control carries out multiple times of fuel injection in each combustion cycle for the purpose of improving emissions, suppressing noise, and the like. When such multi-stage injection control is executed, a fuel injection valve is required to have high-speed operation performance because of the reason why an extremely small amount of fuel injection is required, or the like. Then, in order to 20 satisfy such high-speed operation performance, a piezoelectric injector having an excellent response has become a focus of attention. [00031 The piezoelectric injector drives a nozzle in such a manner that a piezoelectric element extends or contracts as the piezoelectric element is charged or discharged to thereby inject fuel. However, the piezoelectric element has temperature 25 dependency, and the amount of extension or contraction significantly varies with temperature. Specifically, as shown in FIG. 5, the apparent capacitance C of the piezoelectric element, which correlates the electric charge stored in the piezoelectric WO 2012/014034 PCT/IB2011/001668 2 element with the voltage of the piezoelectric element, increases as the temperature increases. In this way, the electrical characteristic of the piezoelectric element varies depending on the temperature, so it is difficult to control the displacement of the piezoelectric element using an electrical state quantity, such as voltage and current. 5 [0004] FIG. 6 shows the correlation between the piezoelectric modulus d of a piezoelectric element and the temperature of the piezoelectric element. The piezoelectric modulus d of the piezoelectric element is obtained as the ratio of a displacement with respect to a voltage. As shown in the drawing, the piezoelectric modulus d of the piezoelectric element increases as the temperature increases. 10 Therefore, even when the displacement is intended to be controlled using the voltage of the piezoelectric element, high control accuracy cannot be obtained. [0005] Then, in the related art, for example, Japanese Patent Application Publication No. 2009-65812 (JP-A-2009-65812) suggests that fuel injection is controlled by operating the amount of driving energy applied to each piezoelectric element instead 15 of operating the electrical state quantity. The reason why such control is executed is that the displacement of each piezoelectric element may be made substantially constant when the amount of driving energy E applied to each piezoelectric element is the same, irrespective of the temperature of each piezoelectric element. This fact may be simply described as follows. That is, when the amount of driving energy E applied to a 20 piezoelectric element is constant, as the capacitance C of the piezoelectric element increases with an increase in the temperature owing to the relationship shown in FIG. 5, the voltage V of the piezoelectric element decreases ("V^2" denotes "the square of V") owing to the relationship "E = 1/2CV^2". Therefore, the increase in the piezoelectric modulus d with an increase in the temperature as shown in FIG. 6 is cancelled by a 25 decrease in the voltage with an increase in the temperature. As a result, the displacement of the piezoelectric element at the same amount of driving energy E is substantially constant irrespective of the temperature the piezoelectric element. 100061 However, during idle operation of an internal combustion engine, combustion noise becomes small to reduce background noise, so the operating noise of 3 each injector becomes remarkable. Then, it is conceivable that, during idle operation, the amount of driving energy applied to each injector is reduced to reduce the operating noise of the injector. However, if the amount of driving energy is changed during fuel injection, the amount of injected fuel deviates from a target injection amount. Object of the Invention [0006a] It is the object of the present invention to substantially overcome or at least ameliorate one or more of the foregoing disadvantages. Summary of the Invention [0006b] An aspect of the present invention relates to a fuel injection control device for an internal combustion engine, which drives the corresponding injector, and which changes an amount of driving energy applied to an injector on the basis of an engine operating state, the device comprising: an electronic control unit that determines whether a precondition for changing the amount of driving energy is satisfied, wherein, after the precondition for changing the amount of driving energy is satisfied, the electronic control unit causes the drive circuit that is executing fuel injection to accomplish the fuel injection at the pre-changed amount of driving energy, and changes the amount of driving energy of the drive circuit that is not executing fuel injection. [0006c] Another aspect of the present invention relates to a fuel injection control device for an internal combustion engine, which has a drive circuit that is provided for each cylinder group and that drives the corresponding injector, and that changes an amount of driving energy applied to an injector on the basis of an engine operating state, the device comprising: an electronic control unit that determines whether a precondition for changing the amount of driving energy is satisfied, wherein, after the precondition for changing the amount of driving energy is satisfied, the electronic control unit changes the amount of driving energy of the drive circuit on condition that the drive circuit is in a standby state where the drive circuit is not executing fuel injection.

4 [0006d] Another aspect of the present invention relates to a fuel injection control device for an internal combustion engine, the device comprising an electronic control unit for determining an amount of driving energy applied to an injector on the basis of an engine operating state, wherein the fuel injection device is configured such that, if the injector is carrying out fuel injection at the time when a request for changing the amount of driving energy is issued, the amount of the driving energy is not changed during the fuel injection that is being carried out. [0006e] Another aspect of the present invention relates to a fuel injection control method for an internal combustion engine, which changes an amount of driving energy applied to an injector on the basis of an engine operating state, the method comprising: determining whether a precondition for changing the amount of driving energy is satisfied; determining whether the injector is carrying out fuel injection; and when the injector is carrying out fuel injection at the time of changing the amount of driving energy, prohibiting, even when a request to change the amount of driving energy is issued, the change of the amount of the driving energy applied to the fuel injection that is being carried out. [0007] Another aspect of the present invention provides a vehicle comprising the fuel injection control device for an internal combustion engine as described above. [0008] There is also described a fuel injection control device for an internal combustion engine, which changes an amount of driving energy applied to an injector on the basis of an engine operating state. The fuel injection control device includes an electronic control unit that, when the injector is carrying out fuel injection at the time of changing the amount of driving energy, allows the injector to accomplish the fuel injection at the pre-changed amount of driving energy. [0009] With the above configuration, even when a request to change the amount of driving energy is issued, the amount of driving energy is not changed for fuel injection that is being carried out at that moment but the injector is allowed to accomplish the fuel injection at the pre changed amount of driving energy. Therefore, with the above configuration, the amount of driving energy is not changed during fuel injection. Thus, with the above configuration, the amount of driving energy may be changed without any deviation of the fuel injection amount.

5 [0010] In addition, the electronic control unit may change the amount of driving energy during a period from completion of fuel injection that is being carried out at the time when a request to change the amount of driving energy is issued to start of the next fuel injection. [0011] By so doing, even when a request to change the amount of driving energy is issued, the amount of driving energy is not changed at that moment but the amount of driving energy is changed during a period from completion of fuel injection that is being carried out to start of the next fuel injection. Therefore, with the above configuration, the amount of driving energy is not changed during fuel injection. Thus, with the above configuration, the amount of driving energy may be changed without any deviation of the fuel injection amount. [0012] In addition, the fuel injection control device may further include a drive circuit that is provided for each cylinder group and that drives the corresponding injector, wherein, at the time of changing the amount of driving energy, the electronic control unit may cause the drive circuit that is executing fuel injection to accomplish the fuel injection at the pre-changed amount of driving energy, and may change the amount of driving energy of the drive circuit that is not executing fuel injection. [0013] With the above configuration, even when a request to change the amount of driving energy is issued, the drive circuit that is executing fuel injection is not caused to change the amount of driving energy at that moment but is caused to accomplish the fuel injection at the pre-changed amount of driving energy. Then, the amount of driving energy of the drive circuit that is not executing fuel injection is changed. Therefore, with the above configuration, the amount of driving energy is not changed during fuel injection. Thus, with the above configuration, the amount of driving energy may be changed without any deviation of the fuel injection amount. [0014] Furthermore, the electronic control unit may change the amount of driving energy of the drive circuit in response to a request to change the amount of driving energy on condition that the drive circuit is in a standby state where the drive circuit is not executing fuel injection.

5a [0015] With the above configuration, even when a request to change the amount of driving energy is issued, the amount of driving energy of that drive circuit is not changed unless in a standby state where the drive circuit is not executing fuel injection. That is, with the above configuration, the amount of driving energy of the drive circuit that is executing fuel injection is not changed but is caused to accomplish the fuel injection at the pre-changed amount of driving energy. Therefore, with the above configuration, the amount of driving energy is not changed during fuel injection. Thus, with the above configuration, the amount of driving energy may be changed without any deviation of the fuel injection amount. [0016] Note that, in the fuel injection control device the electronic control unit may change the amount of driving energy on the basis of a change of the engine operating state between during idle operation of the internal combustion engine and during normal operation, other than the idle operation, of the internal combustion engine. [0017] There is also described a fuel injection control method for an internal combustion engine, which changes an amount of driving energy applied to an injector on the basis of an engine operating state. The fuel injection control method includes: determining whether a precondition for changing the amount of driving energy is satisfied; determining whether the injector is carrying out fuel injection; and when the precondition for changing the amount of driving energy is satisfied and the injector is carrying out fuel injection, allowing the injector to accomplish the fuel injection at the pre-changed amount of driving energy. [0018] Paragraph [0018] intentionally deleted. [0019] Paragraph [0019] intentionally deleted.

5b Brief Description of the Drawings [0020] Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein: FIG. 1 is a diagram that schematically shows the overall configuration of a fuel injection control device for an internal combustion engine according to an embodiment of WO 2012/014034 PCT/IB2011/001668 6 the invention; FIG. 2 is a cross-sectional view that shows the side cross-sectional structure of a piezoelectric injector employed in the embodiment; FIG. 3 is a time chart that shows a mode of driving energy amount change control 5 according to the embodiment; FIG. 4 is a flowchart that shows the procedure of driving energy amount change determination routine employed in the embodiment; FIG. 5 is a graph that shows the correlation between the apparent capacitance C of a piezoelectric element and the temperature of the piezoelectric element; and 10 FIG. 6 is a graph that shows the correlation between the piezoelectric modulus d of a piezoelectric element and the temperature of the piezoelectric element. DETAILED DESCRIPTION OF EMBODIMENTS [00211 Hereinafter, a specific embodiment of a fuel injection control device for 15 an internal combustion engine according to the aspect of the invention will be described in detail with reference to FIG. 1 to FIG. 4. The fuel injection control device according to the present embodiment is applied to a V-eight diesel engine. Four cylinders, that is, a first cylinder #1, a third cylinder # 3, a fifth cylinder # 5 and a seventh cylinder #7, are arranged in the left bank of the diesel engine, and four cylinders, that is, a second 20 cylinder #2, a fourth cylinder #4, a sixth cylinder #6 and an eighth cylinder #8, are arranged in the right bank of the diesel engine. Incidentally, ignition takes place in the diesel engine in the order of the first cylinder #1, the second cylinder #2, the seventh cylinder #7, the third cylinder #3, the fourth cylinder #4, the fifth cylinder #5, the sixth cylinder #6 and the eighth cylinder #8. Note that, in the diesel engine, fuel injection is 25 always carried out in any one of the cylinders during engine operation. [0022] FIG. I shows the overall structure of a fuel injection control device according to the present embodiment. As shown in the drawing, the fuel injection control device includes an electronic control unit (ECU) 10 and two drive circuits (EDUs). The two drive circuits include a first drive circuit 11 and a second drive circuit WO 2012/014034 PCT/IB2011/001668 7 12. The electronic control unit 10 determines the injection amount and injection timing of fuel to issue a command to the drive circuits 11 and 12 on the basis of a detected diesel engine operating condition, such as an engine rotational speed and an accelerator operation amount. Then, the drive circuits 11 and 12 drive injectors INJI to INJ8 on the 5 basis of the command. [0023] Note that, in the present embodiment, the first drive circuit (EDU 1) 11 has charge of a cylinder group formed of four cylinders of the first cylinder #1, the fourth cylinder #4, the sixth cylinder #6 and the seventh cylinder #7. That is, the first drive circuit 11 drives the injector INJI. of the first cylinder #1, the injector INJ4 of the fourth 10 cylinder #4, the injector INJ6 of the sixth cylinder #6 and the injector INJ7 of the seventh cylinder #7. In addition, the second drive circuit (EDU2) 12 has charge of a cylinder group formed of four cylinders of the second cylinder #2, the third cylinder #3, the fifth cylinder #5 and the eighth cylinder #8. That is, the second drive circuit 12 drives the injector INJ2 of the second cylinder #2, the injector INJ3 of the third cylinder #3, the 15 injector INJ5 of the fifth cylinder #5 and the injector INJ8 of the eighth cylinder #8. That is, in the present embodiment in which the order of ignition is set as described above, the two drive circuits 11 and 12 alternately execute fuel injection. 100241 Next, the structure of each of the injectors INJ1 to INJ8 will be described with reference to FIG. 2. FIG. 2 shows the side cross-sectional structure of each of the 20 injectors INJl to INJ8. In the present embodiment, piezoelectric injectors that are driven by piezoelectric elements are employed as the injectors INJ1 to INJ8. A needle accommodating portion 21, which is a cylindrical columnar space, is provided at the distal end of a body 20 of each piezoelectric injector. Then, a nozzle needle 22 is accommodated inside the needle accommodating portion 21 so as to be displaceable in 25 the axial direction. The nozzle needle 22 is seated on an annular needle seat portion 23 to shut off the needle accommodating portion 21 from the outside, that is, a combustion chamber of the diesel engine. The needle seat portion 23 is formed at the distal end portion of the body 20. In addition, the nozzle needle 22 is separated from the needle seat portion 23 to provide fluid communication between the needle accommodating WO 2012/014034 PCT/IB2011/001668 8 portion 21 and the outside. Note that a high-pressure fuel passage 24 is connected to the needle accommodating portion 21 and high-pressure fuel discharged by a fuel pump is supplied through the high-pressure fuel passage 24. [00251 In addition, the back surface side, that is, the side opposite to the side 5 facing the needle seat portion 23, of the nozzle needle 22 faces a back pressure chamber 25. Fuel from the high-pressure fuel passage 24 is supplied to the back pressure chamber 25 via an orifice 26. In addition, a needle spring 27 is arranged in the back pressure chamber 25. The needle spring 27 urges the nozzle needle 22 toward the needle seat portion 23. 10 [0026] Furthermore, the back pressure chamber 25 is communicable with a low-pressure fuel passage 30 via a valve 28. As the back surface side of the valve 28 is seated on an annular valve seat portion 29, the low-pressure fuel passage 30 is shut off from the back pressure chamber 25. As the valve 28 is displaced toward the distal end side of the body 20, the low-pressure fuel passage 30 is brought into fluid communication 15 with the back pressure chamber 25. [0027] The side of the valve 28 adjacent to the valve seat portion 29 is coupled to a small-diameter piston 32 via a pressure pin 31. The rear side of the small-diameter piston 32 faces the distal end side of a large-diameter piston 33 that is larger in diameter than the small-diameter piston 32. Then, a displacement transmitting chamber 34 is 20 defined by the small-diameter piston 32, the large-diameter piston 33 and the inner peripheral surface of the body 20, and then the displacement transmitting chamber 34 is filled with fluid, such as fuel. [0028] On the other hand, the side of the large-diameter piston 33 adjacent to the rear side of the body 20 is coupled to a piezoelectric element 35. Incidentally, the 25 piezoelectric element 35 is fixed to the body 20 at its back surface side of the side facing the large-diameter piston 33. [0029] The thus arranged piezoelectric element 35 is formed of a stack in which a plurality of piezoelectric elements are stacked on top of each other (piezoelectric stack), and the piezoelectric stack extends or contracts owing to inverse piezoelectric effect to WO 2012/014034 PCT/IB2011/001668 9 thereby function as an actuator. Electrically, the piezoelectric element 35 is a capacitive load, and extends when it is charged or contracts when it is discharged. Incidentally, the piezoelectric element 35 installed in each injector according to the present embodiment uses a piezoelectric element made of a piezoelectric material, such as PZT (lead zirconate 5 titanate). [0030] In the thus configured piezoelectric injector, when the piezoelectric element 35 is not supplied with current and is contracted, the pressure of high-pressure fuel in the high-pressure fuel passage 24 is applied to the valve 28 and the small-diameter piston 32, so the valve 28 and the small-diameter piston 32 are placed at the rear side of 10 the body 20. The back pressure chamber 25 at this time is shut off by the valve 28 from the low-pressure fuel passage 30. Therefore, the nozzle needle 22 at this time is pressed toward the distal end side of the body 20 by the pressure of fuel in the back pressure chamber 25 and the urging force of the needle spring 27, so the nozzle needle 22 is in a valve closed state where the nozzle needle 22 is seated on the needle seat portion 23. 15 [00311 On the other hand, when the piezoelectric element 35 is supplied with current and is extended, the valve 28 moves toward the distal end side of the body 20 and then the back pressure chamber 25 is brought into fluid communication with the low-pressure fuel passage 30. By so doing, when the pressure of fuel in the back pressure chamber 25 decreases, the force that high-pressure fuel in the needle 20 accommodating portion 21 presses the nozzle needle 22 toward the rear side of the body 20 overcomes the force that fuel in the back pressure chamber 25 and the needle spring 27 press the nozzle needle 22 toward the distal end side of the body 20. Then, as a result, the nozzle needle 22 at this time is in a valve open state where the nozzle needle 22 is separated from the needle seat portion 23. 25 [0032] Note that the operation of the piezoelectric element 35 of each piezoelectric injector has temperature dependency and the piezoelectric modulus d increases as the temperature increases. Then, in the present embodiment, in order to appropriately drive each piezoelectric injector irrespective of the temperature dependency of the piezoelectric element 35, the amount of driving energy applied to the piezoelectric WO 2012/014034 PCT/IB2011/001668 10 element 35 is operated to control fuel injection. [00331 On the other hand, during idle operation of the diesel engine, combustion noise becomes small to reduce background noise, so the operating noise of each injector becomes remarkable. Then, in the present embodiment, during idle operation, the 5 amount of driving energy applied to each piezoelectric element 35 is reduced to thereby reduce the operating noise of each injector. That is, in the present embodiment, when the diesel engine shifts into idle operation, the amount of driving energy applied to each piezoelectric element 35 is changed from the normal amount of driving energy to the smaller amount of driving energy for idle operation. 10 10034] Note that, when the amount of driving energy applied to each piezoelectric element 35 is changed during fuel injection, the amount of injected fuel deviates from a target injection amount. In addition, depending on a change of the amount of driving energy during fuel injection, the operation of the drive circuit 11 or 12 may fall outside a rated value to cause switching elements, or the like, to be overloaded. 15 [0035] Then, in the present embodiment, at the time of changing the amount of driving energy, when any one of the injectors is carrying out fuel injection, the injector is allowed to accomplish the fuel injection at the pre-changed amount of driving energy. Then, the amount of driving energy is changed during a period from completion of fuel injection that is being carried out at the time when a request to change the amount of 20 driving energy is issued to start of the next fuel injection. [00361 More specifically, in the present embodiment, at the time of changing the amount of driving energy, the drive circuit 11 or 12 that is executing fuel injection is caused to accomplish the fuel injection at the pre-changed amount of driving energy, and the driving circuit 11 or 12 that is not executing fuel injection changes the amount of 25 driving energy. In other words, in the present embodiment, in response to a request to change the amount of driving energy, the amount of driving energy of the drive circuit is changed on condition that the drive circuit is in a standby state where the drive circuit is not executing fuel injection. [0037] Note that, when the amount of driving energy is changed, the fuel WO 2012/014034 PCT/IB2011/001668 11 injection rate varies, so a necessary injection time for supplying a required amount of fuel also varies. For example, when the amount of driving energy is reduced, a necessary amount of fuel cannot be supplied unless an injection time is elongated. Then, the electronic control unit 10 also changes the offset of the injection time (correction of the 5 injection time with the amount of driving energy) in synchronization with changing the amount of driving energy. [00381 FIG. 3 shows a mode of control for changing the amount of driving energy according to the present embodiment. In the drawing, at time t], the precondition for changing from normal energy drive to idling low energy drive is 10 satisfied. The precondition is satisfied, for example, when the accelerator operation amount is "0" and the engine rotational speed is lower than or equal to "1000 rpm". [0039] In the present embodiment, the electronic control unit 10 determines whether to change the amount of driving energy at the time- of updating a cylinder number that indicates which cylinder in which ignition currently takes place. After the 15 precondition is satisfied, the second cylinder #2 is an ignition cylinder at time t2 when initial change determination as to whether to change the amount of driving energy is made, and fuel injection into the second cylinder #2 is started at time t2. Fuel injection into the second cylinder #2 is executed by the second drive circuit 12. The first drive circuit 11 at this time is in a standby state where the first drive circuit 11 is not executing 20 fuel injection. Then, in the present embodiment, at time t2, the second drive circuit 12 maintains the pre-changed amount of driving energy, and only the first drive circuit 11 in a standby state changes the amount of driving energy. Then, changing the amount of driving energy in the second drive circuit 12 is suspended until time t3 at which the next change determination is made. 25 10040] FIG. 4 shows a flowchart of driving energy amount change determination routine employed in the present embodiment. The process of the routine is repeatedly executed by the electronic control unit 10 each time the cylinder number is updated. [0041] When the routine is started, the electronic control unit 10 initially checks in step S100 whether a precondition for changing from normal energy drive to idling low WO 2012/014034 PCT/IB2011/001668 12 energy drive is satisfied. Here, the electronic control unit 10 causes the process to proceed to step S101 when the precondition is satisfied (S100: YES); whereas the electronic control unit 10 causes the process to proceed to step S104 when the precondition is not satisfied (S 100: NO). 5 [00421 When the process proceeds to step S101, the electronic control unit 10 determines whether the first drive circuit 11 is currently executing fuel injection, that is, the first drive circuit 11 has charge of the injector of the ignition cylinder at that moment. Here, when the first drive circuit 11 is not executing fuel injection (Sl0l: NO), that is, when the second drive circuit 12 is executing fuel injection, the electronic control unit 10 10 issues a command for idling low energy drive to the first drive circuit 11 in step S 102, and then ends the process of the current routine. In addition, when the first drive circuit 11 is executing fuel injection (S101: YES), the electronic control unit 10 issues a command for idling low energy drive to the second drive circuit 12 in step S103 and then ends the process of the current routine. 15 100431 On the other hand, when the process proceeds to step S104, the electronic control unit 10 determines whether the first drive circuit 11 is currently executing fuel injection, that is, the first drive circuit 11 has charge of the injector of the ignition cylinder at that moment. Here, when the first drive circuit 11 is not executing fuel injection (S104: NO), that is, when the second drive circuit 12 is executing fuel 20 injection, the electronic control unit 10 issues a command for normal energy drive to the first drive circuit 11 in step S105 and then ends the process of the current routine. In addition, when the first drive circuit 11 is executing fuel injection (S104: YES), the electronic control unit 10 issues a command for normal energy drive to the second drive circuit 12 in step S106 and then ends the process of the current routine. 25 [0044] With the fuel injection control device for an internal combustion engine according to the above described embodiment, the following advantageous effects may be obtained. (1) In the present embodiment, at the time of changing the amount of driving energy, the drive circuit 11 or 12 of the electronic control unit 10, which is executing fuel WO 2012/014034 PCT/IB2011/001668 13 injection, is caused to accomplish the fuel injection at the pre-changed amount of driving energy, and the drive circuit 11 or 12 that is not executing fuel injection changes the amount of driving energy. That is, in the present embodiment, in response to a request to change the amount of driving energy, the electronic control unit 10 changes the amount 5 of driving energy of the drive circuit 11 or 12 on condition that the drive circuit 11 or 12 is in a standby state where the drive circuit 11 or 12 is not executing fuel injection. In this embodiment, even when a request to change the amount of driving energy is issued, the drive circuit 11 or 12 that is executing fuel injection is not caused to change the amount of driving energy at that moment but is caused to accomplish the fuel injection at 10 the pre-changed amount of driving energy. Then, the drive circuit that is not executing fuel injection is caused to change the amount of driving energy. Therefore, in the present embodiment, the amount of driving energy is not changed during fuel injection. Thus, according to the present embodiment, the amount of driving energy may be changed without any deviation of the fuel injection amount. 15 [00451 (2) In the present embodiment, it is possible for the amount of driving energy not to be changed during fuel injection. This may prevent a situation that the operation of the drive circuit 11 or 12 falls outside a rated value to cause the switching elements, or the like, of the drive circuit 11 or 12 to be overloaded. [0046] Note that the above embodiment may be modified into the following 20 alternative embodiments. In the above embodiment, the fuel injection system includes two drive circuits; instead, the aspect of the invention may be applied to an internal combustion engine that includes a fuel injection system having three or more drive circuits. In such a case as well, the drive circuit that is executing fuel injection is caused to accomplish the fuel injection at the pre-changed amount of driving energy, and the 25 drive circuits that are not executing fuel injection each are caused to change the amount of driving energy. By so doing, it is possible to change the amount of driving energy without any deviation of the fuel injection amount. [0047] In the above embodiment, the fuel injection system includes the plurality of drive circuits; instead, the aspect of the invention may be applied to an internal WO 2012/014034 PCT/IB2011/001668 14 combustion engine that includes a fuel injection system having a single drive circuit. In such a case, at the time of changing the amount of driving energy, while the injector is carrying out fuel injection, the injection is allowed to accomplish the fuel injection at the pre-changed amount of driving energy. Then, if the amount of driving energy is 5 changed during a period from completion of fuel injection that is being carried out at the time when a request to change the amount of driving energy is issued to start of the next fuel injection, it is possible to change the amount of driving energy without any deviation of the fuel injection amount. [0048] In the above embodiment, the case where the amount of driving energy is 10 changed during idle operation and during normal operation other than the idle operation are described; however, the aspect of the invention may also be similarly applied to the case where the amount of driving energy is changed in another mode. [0049] In the above embodiment, the aspect of the invention is applied to a fuel injection device employed in a V-eight diesel engine; instead, the aspect of the invention 15 may also be similarly applied to an internal combustion engine that has different cylinder arrangement or a different number of cylinders or that uses a different fuel. [0050] While the disclosure has been explained in conjunction with specific exemplary embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, exemplary 20 embodiments of the disclosure as set forth herein are intended to be illustrative, not limiting. There are changes that may be made without departing from the scope of the disclosure.

Claims

1. A fuel injection control device for an internal combustion engine, which drives the corresponding injector, and which changes an amount of driving energy applied to an injector on the basis of an engine operating state, the device comprising: an electronic control unit that determines whether a precondition for changing the amount of driving energy is satisfied, wherein, after the precondition for changing the amount of driving energy is satisfied, the electronic control unit causes the drive circuit that is executing fuel injection to accomplish the fuel injection at the pre-changed amount of driving energy, and changes the amount of driving energy of the drive circuit that is not executing fuel injection.

2. A fuel injection control device for an internal combustion engine, which has a drive circuit that is provided for each cylinder group and that drives the corresponding injector, and that changes an amount of driving energy applied to an injector on the basis of an engine operating state, the device comprising: an electronic control unit that determines whether a precondition for changing the amount of driving energy is satisfied, wherein, after the precondition for changing the amount of driving energy is satisfied, the electronic control unit changes the amount of driving energy of the drive circuit on condition that the drive circuit is in a standby state where the drive circuit is not executing fuel injection.

3. The fuel injection control device according to claim 1 or 2, wherein the electronic control unit determines whether the precondition for changing the amount of driving energy is satisfied, on the basis of a change of the engine operating state between during idle operation of the internal combustion engine and during normal operation, other than the idle operation, of the internal combustion engine.

4. A fuel injection control device for an internal combustion engine, the device comprising an electronic control unit for determining an amount of driving energy applied to an injector on the basis of an engine operating state, wherein the fuel injection device is configured such that, if the injector is carrying out fuel injection at the time when a request for changing the amount of driving energy is issued, the amount of the driving energy is not changed during the fuel injection that is being carried out. 16

5. The fuel injection control device according to claim 4, wherein the electronic control unit changes the amount of driving energy during a period from completion of fuel injection that is being carried out at the time when a request to change the amount of driving energy is issued to start of the next fuel injection.

6. The fuel injection control device according to claim 4, further comprising: a drive circuit that is provided for each cylinder group and that drives the corresponding injector, wherein, at the time of changing the amount of driving energy, the electronic control unit causes the drive circuit that is executing fuel injection to accomplish the fuel injection at the pre-changed amount of driving energy, and changes the amount of driving energy of the drive circuit that is not executing fuel injection.

7. The fuel injection control device according to claim 6, wherein the electronic control unit changes the amount of driving energy of the drive circuit in response to a request to change the amount of driving energy on condition that the drive circuit is in a standby state where the drive circuit is not executing fuel injection.

8. The fuel injection control device according to any one of claims 4 to 7, wherein the electronic control unit changes the amount of driving energy on the basis of a change of the engine operating state between during idle operation of the internal combustion engine and during normal operation, other than the idle operation, of the internal combustion engine.

9. A fuel injection control method for an internal combustion engine, which changes an amount of driving energy applied to an injector on the basis of an engine operating state, the method comprising: determining whether a precondition for changing the amount of driving energy is satisfied; determining whether the injector is carrying out fuel injection; and when the injector is carrying out fuel injection at the time of changing the amount of driving energy, prohibiting, even when a request to change the amount of driving energy is issued, the change of the amount of the driving energy applied to the fuel injection that is being carried out.

10. A vehicle comprising the fuel injection control device for an internal combustion engine according to any one of claims 4 to 7. 17

11. A fuel injection control device substantially as hereinbefore described with reference to the accompanying drawings.

12. A fuel injection control method substantially as hereinbefore described with reference to the accompanying drawings.

13. A vehicle substantially as hereinbefore described with reference to the accompanying drawings. Toyota Jidosha Kabushiki Kaisha Kabushiki Kaisha Toyota Jidoshokki Patent Attorneys for the Applicant/Nominated Person SPRUSON & FERGUSON