JP2009299494A - Device for controlling amount of fuel injected - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for controlling the amount of fuel injected, achieving fuel injection by required injection quantity even under any condition by a simple structure. <P>SOLUTION: This device for controlling the amount of fuel injected, controlling the amount of fuel injected by moving the needle of a fuel injection means by driving a piezoelectric actuator, is provided with a control means controlling the fuel injection means by using a first drive mode driving the piezoelectric actuator in order to vary fuel injection time by the fuel injection means when the lift of the needle is higher than a predetermined value and by using a second drive mode driving the piezoelectric actuator in order to vary voltage applied to the piezoelectric actuator when the lift of the needle is lower than the predetermined value. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel injection amount control apparatus using a common rail.

  In a fuel injection amount control device applied to a diesel engine, a common rail system that supplies accumulated fuel to an injector (hereinafter also referred to as a fuel injection valve) that directly injects fuel into a combustion chamber of the engine is widely used. . In such a common rail system, fuel pressurized by a high-pressure pump is supplied so that a specified amount can be injected instantaneously.

  In addition, fuel can be injected from the injector in a short injection time by improving the responsiveness of the injector. Combining such a highly responsive injector and the common rail that can store high pressure as described above, fuel can be injected into the combustion chamber of the engine vigorously, fuel can be atomized, and combustion characteristics can be improved. Yes. Thus, the exhaust gas is cleaned by improving the combustion characteristics.

  Further, in the diesel engine, the output characteristics depend on the amount of fuel injected. That is, in order to supply a necessary amount of fuel to the engine when necessary, the fuel injection amount control device needs to appropriately manage the fuel injection amount.

In such a fuel injection amount control device, the actual injection amount deviates from the required injection amount determined according to the accelerator depression amount, etc., due to changes in the pressure of the common rail or changes in the environment surrounding the engine. There is. In order to realize accurate fuel injection even in such a situation, a technique for eliminating the difference between the target and actual fuel injection amount is required, and an example thereof is disclosed in Patent Document 1.
JP 2004-251272 A

According to the technique of Patent Document 1, the relationship between a parameter such as a common rail pressure and a fuel injection rate is prepared as map information or a function, and by using this map information or function, the injector is opened and closed. Control is performed.
However, with such a method, it takes a lot of work to create accurate map information and functions corresponding to common rail pressure fluctuations, etc., and situations outside the range covered by the created map information and functions. However, there is a problem that effective control cannot be performed.

  The present invention has been made in view of the above points, and an object thereof is to provide a fuel injection amount control device capable of realizing fuel injection with a required injection amount under any circumstances with a simple configuration. There is to do.

The present invention has been made to solve the above-mentioned problems, and a fuel injection amount control device (for example, the fuel injection amount control device 10 in the embodiment) described in claim 1 is a piezoelectric actuator (for example, The fuel injection for controlling the fuel injection amount by moving the needle (for example, the needle 603 in the embodiment) of the fuel injection means (for example, the fuel injection valve 6 in the embodiment) by driving the piezo actuator 601 in the embodiment. In the amount control device, when the lift amount of the needle is equal to or greater than a predetermined value, the first drive mode for driving the piezoelectric actuator so as to make the fuel injection time by the fuel injection means variable is used. When the lift amount is smaller than a predetermined value, the voltage applied to the piezoelectric actuator is variable and the piezoelectric actuator is changed. Using the second drive mode that drives Yueta, said control means for controlling the fuel injection means (for example, ECU 2 in the embodiment), characterized in that it comprises a.
This makes it possible to perform fuel injection according to the lift amount of the needle by switching between the first drive mode and the second drive mode.

In the fuel injection amount control apparatus according to the second aspect of the present invention, the control unit obtains the lift amount of the needle based on the fuel injection amount by the fuel injection unit.
Thereby, the lift amount of the needle can be obtained from the fuel injection amount, and fuel injection corresponding to the fuel injection amount can be performed.

According to a third aspect of the present invention, there is provided the fuel injection amount control apparatus according to the third aspect, wherein the control means is a fuel supply means for supplying the fuel injection means with a fuel injection amount by the fuel injection means (for example, an embodiment). In the common rail 13 and the high-pressure pipes 13b-1 to 13b-4).
Thus, the fuel injection amount can be obtained from the pressure difference in the fuel supply means.

According to a fourth aspect of the present invention, in the fuel injection amount control apparatus according to the fourth aspect of the present invention, when the fuel injection amount by the fuel injection unit deviates from the requested fuel injection amount, the control unit learns the deviation and performs the next time. The fuel injection amount is corrected at the time of fuel injection.
Thus, the optimum fuel injection can be performed quickly at the next fuel injection using the learning result.

  According to a fifth aspect of the present invention, the control means selects the first or second drive mode in accordance with the requested fuel injection amount.

  According to the first aspect of the invention, it is possible to perform fuel injection according to the lift amount of the needle by switching between the first drive mode and the second drive mode. Therefore, since the map information or the like is not used, the configuration can be simplified, and since the map information or the like is not restricted to the corresponding range, the desired fuel injection can be realized under any circumstances.

  According to the second aspect of the present invention, it is possible to determine the lift amount of the needle from the fuel injection amount and perform fuel injection according to the fuel injection amount.

  According to the third aspect of the invention, the fuel injection amount can be obtained from the pressure difference in the fuel supply means.

  According to the invention described in claim 4, it is possible to quickly perform the optimum fuel injection at the next fuel injection by using the learning result.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is an overall configuration diagram of a fuel injection amount control apparatus according to an embodiment of the present invention. The fuel injection amount control device 10 is applied to a diesel engine (hereinafter referred to as the engine 1) mounted on a vehicle (not shown), and controls the injection amount of fuel supplied to the combustion chamber of the engine 1.

The fuel tank 11 stores the fuel supplied to the engine 1. In the fuel tank 11, a low pressure pump P1 is provided.
The low-pressure pump P1 is provided with a motor P1-M connected to an ECU (Electronic Control Unit) 2. The low pressure pump P1 is an electric pump whose motor P1-M is controlled by the ECU 2 and is always operated during operation of the engine 1. The low pressure pump P1 increases the fuel in the fuel tank 11 to a predetermined pressure (for example, 5 bar (bar)). Discharge.
A filter 17 is provided on the suction side of the low-pressure pump P1, and a fuel supply path 12 is connected on the discharge side. The connected fuel supply path 12 has a filter 18 having a heater for controlling the temperature of the fuel by the control from the ECU 2, and an electromagnetic flow rate control for controlling the flow rate of the fuel supplied from the low-pressure pump P 1 by the control from the ECU 2. A valve 21 is provided sequentially.

  A fuel return path 16 that returns fuel to the fuel tank 11 is branched and connected to the fuel supply path 12 between the filter 18 and the electromagnetic flow control valve 21. A pressure control valve 22 that controls the pressure of the fuel supply path 12 is interposed in the fuel return path 16. The pressure control valve 22 is opened when the pressure in the fuel supply passage 12 exceeds the predetermined pressure, and returns the fuel into the fuel tank 11 through the fuel return passage 16.

A high pressure pump P2 is connected to the downstream side of the electromagnetic flow control valve 21, and a common rail 13 is connected to the discharge side of the high pressure pump P2 via a high pressure pipe 13a. The high pressure pump P2 further increases the pressure of the fuel supplied from the low pressure pump P1 and supplies it to the common rail 13. The pressure of the fuel discharged from the high-pressure pump P2 is controlled by the flow control of the electromagnetic flow control valve 21.
The fuel temperature sensor 35 attached to the high-pressure pump P2 detects the temperature of the fuel pressurized by the high-pressure pump P2, and outputs a detection signal indicating the detected temperature to the ECU 2.

A high pressure pipe 13c is connected to the return path side of the common rail 13, and a fuel return path 16 is connected to the high pressure pipe 13c. The high-pressure pipe 13 c is provided with an electromagnetic pressure control valve 23, and the fuel return path 14 is connected from the electromagnetic pressure control valve 23 to the fuel return path 16.
The electromagnetic pressure control valve 23 has a function that operates mechanically and a function that operates electrically by control from the connected ECU 2. In the mechanical operation, the valve is opened when the fuel pressure Prail exceeds a predetermined set pressure Prail_max (for example, 2000 bar (bar)) by the operation of the high-pressure pump P2. Thereby, the fuel in the common rail 13 is returned into the fuel tank 11, and the fuel pressure Prail is reduced to a predetermined set pressure Prail_max. In the electrical operation, the valve is opened according to a pressure reduction instruction from the ECU 2 that is output as necessary, so that the fuel accumulated in the common rail 13 can be discharged and the pressure can be reduced.

Further, the common rail 13 balances the amount of fuel pressurized and supplied by the high-pressure pump P2 with the amount discharged and depressurized by the electromagnetic pressure control valve 23 or the like, so that the internal space is in a high-pressure state (for example, , 2000 bar (bar)). A fuel pressure sensor 37 is attached to the common rail 13, and the fuel pressure sensor 37 detects a fuel pressure Pail that is a fuel pressure in the common rail 13, and outputs a detection signal representing the detected pressure to the ECU 2.
The common rail 13 has a high-pressure pipe 13b- for supplying fuel to four fuel injection valves 6-1 to 6-4 (hereinafter collectively referred to as "fuel injection valves 6") that inject fuel into the engine 1. 1 to 13b-4 are connected.
The fuel injection valve 6 is opened by a signal from the ECU 2 and injects fuel supplied from the common rail 13 into the combustion chamber of the engine 1.

The fuel return path 15 indicates a fuel return path from each fuel injection valve 6, and a fuel supply path between the low pressure pump P 1 and the filter 18 via a check valve 24 and a pressure control valve 25 connected in parallel. 12 is connected.
A check valve 24 and a pressure control valve 25 provided in the middle of the fuel return path 15 adjust the pressure of the discharged oil from the fuel injection valve 6 to be constant. The pressure control valve 25 also has a function of pressurizing the fuel return path 15 from the fuel supply path 12 to the fuel injection valve 6 by the low-pressure pump P1 connected to the fuel supply path 12 when the operation of the engine 1 is started.

The ECU 2 is constituted by a microcomputer including a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), an I / O (Input / Output) interface (all not shown), and the like.
The ECU 2 controls the fuel injection timing at the fuel injection valve 6 from the crank angle information of the engine 1 detected by the crank angle sensor 33 provided in the engine 1. Further, the ECU 2 determines the operating state of the engine 1 according to the detection signals from the fuel temperature sensor 35, the fuel pressure sensor 37, etc., and controls the electromagnetic flow control valve 21, the electromagnetic pressure control valve 23, and the low pressure pump P1. Thus, the pressure of the common rail 13 is controlled, and the fuel injection amount control is executed by opening and closing the fuel injection valve 6. A detailed control method of the ECU 2 will be described later.

With the above-described configuration, in the fuel injection amount control device 10, the operating state of the high-pressure pump P <b> 2 controlled by the electromagnetic flow control valve 21, the open / close state of the electromagnetic pressure control valve 23, and the open / close state of the fuel injection valve 6. Thus, the fuel pressure Prail of the common rail 13 is controlled within a range having a predetermined set value Prail_max as an upper limit.
In addition, the connection by the continuous line shown by FIG. 1 shows piping of fuel system, and the connection by a dashed-dotted line shall show the connection by the control line by an electrical signal. In addition, although the low pressure pump P1 is provided in the fuel tank 11, the low pressure pump P1 may be disposed outside the fuel tank 11.

FIG. 2 is a view showing a cross-sectional structure of the fuel injection valve (injector) 6.
In FIG. 2, the fuel injection in the fuel injection valve 6 is realized by controlling a piezo actuator 601 that expands and contracts according to the applied voltage.

  The lower end portion of the piezo actuator 601 passes through an opening 611 communicating with the low pressure passage 625 connected to the fuel return passage 15 and protrudes to the valve chamber 612. A hemispherical valve body 602 is attached to the tip thereof with its flat surface facing down. The bottom surface of the valve chamber 612 communicates with a communication passage 622 branched from the high-pressure passage 621 connected to the common rail 13. When the piezo actuator 601 contracts, the upper spherical surface of the valve body 602 closes the opening 611 and blocks the valve chamber 612 and the low pressure passage 625. Further, the flat portion of the valve body 602 closes the communication passage 622 when the piezo actuator 601 extends, and shuts off the valve chamber 612 and the high-pressure passage 621 side.

  On the other hand, a cylindrical vertical hole 614 is provided below the piezoelectric actuator 601, and a rod-like needle 603 is disposed in the vertical hole 614. The vicinity of the center of the needle 603 is formed with a larger diameter than other portions, and the space below the large diameter portion of the vertical hole 614 forms a fuel reservoir 615. The fuel pool 615 is always supplied with fuel from the common rail 13 through the high-pressure passage 621.

  Further, the tip 603a of the needle 603 has a conical shape, and when the needle 603 is lowered, the tip 603a enters a recess 616 formed on the bottom surface of the fuel reservoir 615. The recess 616 has an opening 617 having a diameter smaller than the maximum diameter of the tip 603 a of the needle 603. The recess 616 is formed with an injection hole 618 for injecting fuel accumulated in the fuel reservoir 615 into the combustion chamber of the engine 1.

  Further, a back pressure chamber 613 that communicates with the high pressure passage 621 through the communication passage 623 and communicates with the valve chamber 612 through the communication passage 624 is formed in the upper portion of the needle 603. The ceiling of the back pressure chamber 613 restricts the upward movement of the needle 603.

  In the fuel injection valve 6 configured as described above, when the piezo actuator 601 is contracted, the valve body 602 is separated from the bottom surface of the valve chamber 612 so that the valve chamber 612 communicates with the communication passage 622 and the valve body 602. The upper spherical surface closes the opening 611 and the valve chamber 612 and the low pressure passage 625 are blocked. As a result, the high-pressure fuel from the common rail 13 is sequentially supplied to the back pressure chamber 613 through the high pressure passage 621, the communication passage 622, the valve chamber 612, and the communication passage 624, and the fuel supplied to the back pressure chamber 613 is supplied to the low pressure passage. Since it does not leak to 625, the pressure in the back pressure chamber 613 increases. The pressure applied to the back pressure chamber 613 acts as a force for pushing the needle 603 downward. When the pressure value exceeds a predetermined value, the needle 603 is seated in the recess 616 and the needle tip 603a closes the opening 617. The fuel injection from the nozzle hole 618 stops.

  When the piezo actuator 601 is extended from the above state and the upper spherical surface of the valve body 602 is separated from the opening 611, the valve chamber 612 and the low pressure passage 625 communicate with each other and are accumulated in the back pressure chamber 613. The fuel leaks to the low pressure passage 625 side, and the pressure in the back pressure chamber 613 decreases. Then, the needle 603 is held at a position where the pressure in the back pressure chamber 613 and the pressure in the fuel reservoir 615 are balanced, and is separated from the recess 616. As a result, the fuel accumulated in the fuel reservoir 615 flows out to the concave portion 616 side through the gap formed between the opening 617 of the concave portion 616 and the conical needle tip 603a, and depends on the size of the gap. The fuel is injected from the nozzle hole 618 at a fuel injection amount.

  As the piezo actuator 601 extends, the amount of fuel leaked into the low pressure passage 625 increases, the pressure in the back pressure chamber 613 decreases, the balance position where the needle 603 is held moves upward, and the needle tip 603a is recessed. As the depth of entry to 616 becomes shallower, the gap is expanded. Accordingly, the fuel injection amount can be controlled by controlling the expansion and contraction of the piezo actuator 601.

  When the piezo actuator 601 further extends and the valve body 602 is seated on the bottom surface of the valve chamber 612, the valve chamber 612 and the communication passage 622 are cut off, and the high pressure passage 621, the communication passage 622, and the valve are disconnected from the common rail 13. The fuel is not supplied to the back pressure chamber 613 through a path that sequentially passes through the chamber 612 and the communication passage 624. Then, the pressure in the back pressure chamber 613 cannot be maintained, and the head (upper part) of the needle 603 eventually comes into contact with the ceiling of the back pressure chamber 613, and the needle 603 can no longer move upward. Therefore, the size of the gap, in other words, the fuel injection amount takes the maximum value in this state.

  FIG. 3 is a graph showing the relationship between the voltage V applied to the piezo actuator 601 and the actual opening area a in the opening 617 of the recess 616 corresponding to the size of the gap. Here, the piezo actuator 601 contracts when the applied voltage is reduced, and expands when the applied voltage is increased.

As described above, when the piezo actuator 601 is contracted (assuming that the applied voltage V is zero), the needle 603 is seated in the recess 616 and the opening 617 is closed by the needle tip 603a. Zero (A in the figure). When the piezo actuator 601 is extended until the valve body 602 is seated on the bottom surface of the valve chamber 612 (the applied voltage at this time is V _max ), the opening area a is such that the head of the needle 603 is the back pressure chamber 613. It is a value determined by the positional relationship between the needle tip 603a and the opening 617 in a state of contact with the ceiling (the opening area is a _max ) (C in the figure). Even if an applied voltage V higher than this is applied to the piezoelectric actuator 601, the opening area a does not increase. In a state where a voltage between zero and V _max is applied to the piezo actuator 601, the opening area a takes a value between zero and a _max according to the voltage value (B in the figure).

  As described above, the behavior of the opening area a that determines the fuel injection amount has a constant value regardless of the region (A to C in the figure) that changes according to the applied voltage V to the piezo actuator 601 and the applied voltage V. It can be divided into two areas (the higher voltage side than C in the figure). Therefore, controlling the fuel injection amount suitable for each of the two regions leads to optimization of the control. Hereinafter, the latter region is referred to as a full lift region because the needle 603 has been raised (lifted) to the limit, and the former region is referred to as a non-full lift region.

  FIG. 4 is a diagram showing a fuel injection control method in each of the full lift region and the non-full lift region. The first drive mode is a control method applied to the non-full lift region, and the second drive mode is a control method applied to the full lift region.

In the non-full lift region, the opening area a can be changed by the applied voltage V to the piezo actuator 601, so the injection time (the time for applying the voltage to the piezo actuator 601 to open the opening 617 and injecting fuel) is constant. The injection amount is controlled by changing the applied voltage V. This is the first drive mode. The voltage V applied to the piezo actuator 601 in the first drive mode is equal to or less than the maximum voltage V _max shown in FIG. In the control in the first drive mode, the above-described constant injection time is T (referred to as a reference injection time), and the fuel when the maximum voltage V _max is applied to the piezo actuator 601 and fuel injection is performed for the reference injection time T is performed. the injection quantity when the Q _0, can control the injection amount from 0 to Q _0.

On the other hand, in the full lift region, even if the applied voltage V to the piezo actuator 601 is changed, the opening area a does not change. Therefore, the applied voltage is set to the voltage value V _max corresponding to the maximum value a _max of the opening area, and the injection time is changed. By controlling the injection amount. This is the second drive mode. In the control by the second drive mode can be controlled by the injection amount in Q ₀ is larger than the range.

  Of the two drive modes, the ECU 2 selects an appropriate drive mode according to the full lift region or the non-full lift region, and the ECU 2 performs fuel injection control according to the selected drive mode. The determination of the full lift region or the non-full lift region can be made based on the fuel injection amount. For example, when the fuel injection amount is very small, the needle 603 is not in contact with the ceiling of the back pressure chamber 613 in order to inject fuel with a small opening area a, that is, a non-full lift region. It can be judged. Further, when the fuel injection amount is sufficiently large, the needle 603 is in contact with the ceiling of the back pressure chamber 613 in order to inject the fuel with the opening area a being maximized, that is, the full lift region. I can judge.

Next, an example of fuel injection control by the ECU 2 will be described.
First, the basic concept of control is shown in FIG. In the figure, the required injection quantity of the first is Q _1, the required injection amount of the second is Q _2, the required injection amount of the third time is Q _3. However, it is assumed that Q ₁ <Q ₂ <Q ₀ <Q ₃ . The required injection amount is the amount of fuel to be injected this time determined by the ECU 2 based on the accelerator depression amount and the like.

In the first injection, the required injection amount Q ₁ is smaller than Q _0, ECU 2 is determined to be non-full lift region, controls the fuel injection by the first drive mode. That is, the injection time T ₁ is set to the reference injection time T, and the voltage applied to the piezo actuator 601 is set to a value corresponding to the required injection amount Q ₁ , for example, V ₁ (<V _max ). The second injection is also a non-full lift region, and the injection time T ₂ is set to the reference injection time T and the applied voltage is set to V ₂ (<V _max ), for example, as in the first injection.

In the third injection, the required injection amount Q ₃ for greater than Q _0, ECU 2 is determined to be full lift region, controls the fuel injection by the second drive mode. That is, the voltage applied to the piezoelectric actuator 601 is set to the maximum voltage _{V max,} the injection time _{T 3,} the value corresponding to the required injection amount _{Q 3,} is set, for example, _T 3 (> _T) and.
As described above, the ECU 2 controls the fuel injection amount by switching between the first drive mode and the second drive mode in accordance with the required injection amount.

  By the way, the pressure fluctuation of the common rail 13 may occur due to various factors during the operation of the engine 1. In such a case, the internal pressure of the fuel reservoir 615 of the fuel injection valve 6 and the back pressure chamber 613 does not become an appropriate pressure. Therefore, even if the piezo actuator 601 is driven with the instructed applied voltage and injection time to control the valve opening time and the opening area a of the needle 603, fuel is injected with an injection amount different from the required injection amount. Become. Therefore, in order to realize accurate fuel injection, it is necessary to control to correct the difference between the actual fuel injection amount and the required injection amount.

6 and 7 show control examples for performing the above correction.
In FIG. 6, the required injection amount is the same value Q _A for the first time, the second time, and the third time. However, it is assumed that Q _A <Q ₀ and the situation is in the non-full lift region (that is, the first drive mode is applied). Here, in the first injection, the amount of fuel actually injected as a result of injecting fuel with the applied voltage of the piezo actuator 601 set to V ₁ in accordance with the required injection amount Q _A (hereinafter referred to as the actual injection amount). Is Q ₁ ′, which is smaller than the required injection amount Q _A by ΔQ ₁ . At this time, in the second injection, the required injection amount is the same Q _A as in the first injection, but the applied voltage of the piezo actuator 601 is not the same V ₁ as in the first injection, but the actual injection amount and the actual injection amount in the first injection. The value corresponding to ΔQ ₁ is corrected to a value V ₂ that is larger than V ₁ so that more fuel can be injected by the difference ΔQ _{1 from} the injection amount.

By setting the applied voltage to V ₂ , the actual injection amount in the second injection increases from the first time. Here, it is assumed that the second actual injection amount is Q ₂ ′ which is larger than the required injection amount Q _A by ΔQ ₂ . This difference ΔQ ₂ has a smaller absolute value than ΔQ ₁ because the _second applied voltage V ₂ is corrected in consideration of the _first difference ΔQ ₁ . At this time, similarly to the above, in the third injection, the piezo actuator 601 is configured so that less fuel than Q ₂ ′ can be injected by the difference ΔQ ₂ between the required injection amount and the actual injection amount in the _second injection. The applied voltage is corrected to a value V ₃ smaller than the _second applied voltage V ₂ by a value corresponding to ΔQ ₂ . Thus, the actual injection quantity of third time decreased from the second, closer to the required injection amount Q _A. That is, the absolute value of the difference ΔQ ₃ between the required injection amount and the actual injection amount in the _third injection is further smaller than the absolute value of ΔQ ₂ .

  Thereafter, similarly, the fuel injection amount (actual injection amount) is successively corrected by changing the applied voltage of the piezo actuator 601 in the current injection in accordance with the difference between the required injection amount and the actual injection amount in the previous injection. Eventually, the actual injection amount matches the required injection amount. Therefore, optimal control for injecting fuel at the required fuel injection amount is realized.

Further, the ECU 2 stores the voltage V _n applied to the piezo actuator 601 when the actual injection amount and the required injection amount finally coincide with each other as an appropriate applied voltage when the required injection amount is Q _{A in} the RAM. and (learning), the next time the required injection amount Q _a is instructed, ECU 2 is immediately carried out fuel injection by the learned applied voltage V _n from the first injection. As a result, it is possible to quickly realize optimum fuel injection control without waiting for the actual injection amount and the required injection amount to coincide with each other. It is preferable to perform such learning for an arbitrary Q _A in the range of 0 <Q _A <Q ₀ and store the result in the RAM of the ECU 2.

FIG. 7 shows a control example in the situation of the full lift region (that is, the first drive mode is applied). Required injection amount is first time, second time, a Q ₀ is larger than the same value Q _B the third time both. Here, first the injection time according to the required injection amount Q _B in injection T _{1 (>} T) set to a result of injecting fuel, the actual injection quantity is required injection amount Q _B from only Delta] Q ₁ small Q ₁ Suppose that At this time, in the second injection, the required injection amount is the same Q _{B as} in the first injection, but the injection time is not the same T ₁ as the first injection, but the required injection amount and the actual injection amount in the first injection The value corresponding to ΔQ ₁ is corrected to T ₂ longer than T _{1 so that} more fuel can be injected by the difference ΔQ ₁ .

By injection time is set to T _2, the actual injection quantity in the second injection is increased than the first. Here, as in the case of FIG. 6, the difference ΔQ ₂ between the actual injection amount Q ₂ ′ of the _second injection and the required injection amount Q _B has an absolute value smaller than ΔQ ₁ . In the third injection, the injection time is corrected to T ₃ shorter than the _second injection time T ₂ by a value corresponding to ΔQ ₂ so that fuel less than Q ₂ ′ can be injected by this difference ΔQ ₂ . Thus, the actual injection quantity of third time decreased from the second, closer to the required injection amount Q _B.

  Thereafter, in the same manner, the fuel injection amount (actual injection amount) is sequentially corrected by changing the injection time in the current injection in accordance with the difference between the required injection amount and the actual injection amount in the previous injection. Specifically, the actual injection amount matches the required injection amount. Therefore, optimal control for injecting fuel at the required fuel injection amount is realized.

Further, the ECU 2 stores (learns) the injection time T _n when the actual injection amount and the required injection amount finally coincide with each other as an appropriate injection time when the required injection amount is Q _{B in} the RAM. when the next required injection amount Q _B is instructed, ECU 2 is immediately implement the learned injection duration fuel injection by T _n from the first injection. As a result, it is possible to quickly realize optimum fuel injection control without waiting for the actual injection amount and the required injection amount to coincide with each other. It is preferable to store the result in ECU2 of the RAM performed such learning any _{Q B} satisfying _Q 0 _{<Q B.}

In the correction of the fuel injection amount described above, it is necessary to know the actual injection amount in order to change the applied voltage and the injection time of the piezo actuator 601, but the actual injection amount Q is expressed by the following equation: Q = C · A · √ (2 · ΔP / ρ)
Can be obtained using Here, C is the flow coefficient, ρ is the density of the fuel (gas), ΔP is the fuel pressure Prail in the common rail 13 measured by the fuel pressure sensor 37 and each high-pressure pipe 13b-1 to 13b measured by a pressure sensor provided separately. -4 is the difference from the fuel pressure in -4, and A is the cross-sectional area of the high-pressure pipes 13b-1 to 13b-4.

In the present embodiment, the number of fuel injection valves 6 is four and the number of common rails 13 is one. However, the number of fuel injection valves 6 is not limited to four and one, but depends on the configuration of the engine 1. The quantity can be set arbitrarily.
Although the engine 1 has been described as a diesel engine, the fuel supply control device 10 can be applied to a gasoline engine.

  The present invention can be applied to various industrial internal combustion engines including internal combustion engines for ship propulsion devices such as outboard motors.

1 is an overall configuration diagram of a fuel injection amount control device according to an embodiment of the present invention. It is a figure which shows the cross-section of a fuel injection valve (injector). It is the figure which showed the graph showing the relationship between the voltage V applied to a piezoelectric actuator, and the opening area a. It is a figure which shows the control method of the fuel injection in each of a full lift area | region and a non-full lift area | region. It is a figure which shows the example of control (basic) of the fuel injection by ECU. It is a figure which shows the example of control (non-full lift area | region) which correct | amends fuel injection quantity by ECU. It is a figure which shows the example of control (full lift area | region) which correct | amends fuel injection quantity by ECU.

Explanation of symbols

2 ECU (control means)
6 Fuel injection valve (fuel injection means)
10 Fuel injection amount control device 13 Common rail (fuel supply means)
13b-1 to 13b-4 High-pressure piping (fuel supply means)
601 Piezo actuator (piezo actuator)
603 needle

Claims (5)

In a fuel injection amount control device for controlling the fuel injection amount by moving the needle of the fuel injection means by driving a piezoelectric actuator,
When the lift amount of the needle is greater than or equal to a predetermined value, the first drive mode is used to drive the piezoelectric actuator so that the fuel injection time by the fuel injection means is variable, and the lift amount of the needle is a predetermined value. When the fuel injection amount is smaller, the fuel injection amount includes a control means for controlling the fuel injection means using a second drive mode for driving the piezoelectric actuator by changing a voltage applied to the piezoelectric actuator. Control device.   2. The fuel injection amount control apparatus according to claim 1, wherein the control unit obtains a lift amount of the needle based on a fuel injection amount by the fuel injection unit.   The fuel injection amount according to claim 2, wherein the control means calculates a fuel injection amount by the fuel injection means based on a pressure difference in a fuel supply means for supplying fuel to the fuel injection means. Control device.   3. The control unit according to claim 2, wherein when the fuel injection amount by the fuel injection unit deviates from the requested fuel injection amount, the control unit learns the deviation and corrects the fuel injection amount at the next fuel injection. Or the fuel-injection-amount control apparatus of Claim 3.   The fuel injection amount control according to any one of claims 1 to 4, wherein the control means selects the first or second drive mode in accordance with a requested fuel injection amount. apparatus.

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