WO2020116427A1

WO2020116427A1 - Injection control device for internal combustion engine

Info

Publication number: WO2020116427A1
Application number: PCT/JP2019/047167
Authority: WO
Inventors: 柱成尹; 淳川村
Original assignee: 株式会社デンソー
Priority date: 2018-12-05
Filing date: 2019-12-03
Publication date: 2020-06-11
Also published as: JP2020090928A

Abstract

An injection control device for an internal combustion engine (70) controls a fuel injection amount from a fuel injection valve (20) by changing a lift amount of a nozzle needle (31). The injection control device includes a drive control unit that controls a lift speed of the nozzle needle (31) in a variable manner, on the basis of a drive signal. In at least one of a lift increasing period during which the lift amount of the nozzle needle (31) is changed to an increasing side in response to a valve opening command for the fuel injection valve (20) and a lift decreasing period during which the lift amount of the nozzle needle (31) is changed to a decreasing side in response to a valve closing command for the fuel injection valve (20), the drive control unit performs speed change control in which the lift speed of the nozzle needle (31) is controlled at a lower speed in a period during which the nozzle needle (31) is located in a first lift region close to a full lift position than in a period during which the nozzle needle (31) is located in a second lift region in which the lift amount is less than in the first lift region.

Description

Injection control device for internal combustion engine

Cross-reference of related applications

This application is based on Japanese Patent Application No. 2018-228190 filed on December 5, 2018, the content of which is incorporated herein by reference.

The present disclosure relates to an injection control device for an internal combustion engine.

As a fuel injection valve for a diesel engine, a nozzle needle is moved in the opening direction and the closing direction of the fuel injection valve by controlling the fuel pressure inside a control chamber arranged above the nozzle needle with an orifice. Is generally known (for example, refer to Patent Document 1). Patent Document 1 discloses that the valve opening speed and the valve closing speed of the nozzle needle are improved by increasing the out-orifice flow rate.

JP, 2016-53354, A

However, if the opening speed and closing speed of the nozzle needle are simply increased, the nozzle needle will reach the maximum lift position or the closing position in a short time after the drive command. In this case, there is a concern that the amount of fuel that can be injected by the fuel injection valve will decrease.

The present disclosure has been made in view of the above problems, and increases the amount of fuel injected from the fuel injection valve by one fuel injection while ensuring the responsiveness of the nozzle needle to the drive command of the fuel injection valve. A main object of the present invention is to provide an injection control device for an internal combustion engine that is capable of performing the above.

The following means have been adopted to solve the above problems.

The present disclosure relates to an injection control device for an internal combustion engine that controls a fuel injection amount by the fuel injection valve by changing a lift amount of a nozzle needle that opens and closes the fuel injection valve. The disclosure according to claim 1 includes a drive control unit that variably controls a lift speed of the nozzle needle based on a drive signal, and the drive control unit includes the nozzle needle in response to a valve opening command of the fuel injection valve. In at least one of a lift increasing period for changing the lift amount of the nozzle needle to the increasing side and a lift decreasing period for changing the lift amount of the nozzle needle to the decreasing side in response to a valve closing command of the fuel injection valve, the nozzle needle is fully lifted. A speed change for controlling the lift speed of the nozzle needle at a lower speed in a period in the first lift region closer to the position than in a period in the second lift region on the smaller lift amount side with respect to the first lift region. Take control.

In the above configuration, the lift speed of the nozzle needle is controlled to be slower in a period in which the lift amount of the nozzle needle is large at least at one of the injection start and the injection end of the fuel injection than in the period in which the lift amount is small. Thereby, the timing at which the nozzle needle reaches the maximum lift position or the valve closing position can be delayed, and the valve opening period of the fuel injection valve can be made as long as possible. Therefore, according to the above configuration, it is possible to increase the amount of fuel injected from the fuel injection valve by one fuel injection while ensuring the responsiveness of the nozzle needle to the drive command of the fuel injection valve.

The above and other objects, features and advantages of the present disclosure will become more apparent by the following detailed description with reference to the accompanying drawings. The drawing is
FIG. 1 is a diagram showing a schematic configuration of a fuel injection system, FIG. 2 is a diagram showing an example of an injection rate pattern of the fuel injection valve, FIG. 3 is a diagram showing a fuel injection valve when the valve is closed, FIG. 4 is a diagram for explaining the operation of the fuel injection valve in the high speed valve opening mode, FIG. 5 is a diagram for explaining the operation of the fuel injection valve when shifting from the high speed valve opening mode to the high speed valve closing mode, FIG. 6 is a diagram for explaining the operation of the fuel injection valve in the high speed valve closing mode, FIG. 7 is a diagram for explaining the operation of the fuel injection valve in the low speed valve opening mode, FIG. 8 is a diagram for explaining the operation of the fuel injection valve when shifting from the low speed valve opening mode to the low speed valve closing mode, FIG. 9 is a diagram for explaining the operation of the fuel injection valve in the low speed valve closing mode, FIG. 10 is a diagram showing a pressure reducing operation by the second opening/closing valve, FIG. 11 is a diagram showing a specific mode of lift speed control at the start of injection and at the end of injection. FIG. 12 is a diagram for explaining the lift speed control according to the injection pressure, FIG. 13 is a diagram for explaining the lift speed control according to the fuel temperature, FIG. 14 is a diagram for explaining the lift speed control according to the individual difference of the fuel injection valve, FIG. 15 is a diagram for explaining lift speed control according to the injection interval, FIG. 16 is a flowchart showing a processing procedure of lift speed control, FIG. 17 is a functional block diagram showing the calculation processing of the speed switching time.

Embodiments will be described below with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other are given the same reference numerals in the drawings, and the description of the portions having the same reference numerals is cited.

The present embodiment is embodied in a fuel injection system applied to an in-vehicle multi-cylinder diesel engine which is an internal combustion engine. In this fuel injection system, an electronic control unit (hereinafter, referred to as "ECU") is the center for controlling the fuel injection of the engine. As shown in FIG. 1, the fuel injection system 10 includes a common rail 11, a fuel injection valve 20, and an ECU 90.

In FIG. 1, the common rail 11 is connected to the downstream side of a high-pressure pump (not shown), and fuel pressurized by the high-pressure pump (hereinafter referred to as “high-pressure fuel”) is supplied. Inside the common rail 11, the high-pressure fuel pumped from the high-pressure pump is held in a high pressure state. A rail pressure sensor 73 that detects the fuel pressure inside the common rail 11 (hereinafter referred to as “rail pressure”) is attached to the common rail 11. The detection signal of the rail pressure sensor 73 is input to the ECU 90.

A fuel injection valve 20 is connected to the common rail 11 via a high-pressure pipe 12. The fuel injection valve 20 is a direct injection type that directly injects fuel into the combustion chamber of the engine 70, and one fuel injection valve is attached to each of a plurality of cylinders (four cylinders in this embodiment). It should be noted that FIG. 1 shows only the fuel injection valve 20 of one cylinder, and the description of the fuel injection valve 20 is omitted for the remaining cylinders.

The ECU 90 is a microcomputer including a CPU, ROM, RAM, drive circuit, input/output interface, and the like. Detection signals are sequentially input to the ECU 90 from various sensors such as a crank angle sensor that detects a rotation speed of the engine 70 and an accelerator sensor that detects an accelerator operation amount. The ECU 90 calculates an optimum fuel injection amount and injection timing based on engine operation information such as engine rotation speed and accelerator operation amount, and outputs a corresponding energization pulse (injection signal) to the fuel injection valve 20. As a result, fuel injection by the fuel injection valve 20 is controlled in each cylinder.

Next, the configuration of the fuel injection valve 20 will be described in detail. The fuel injection valve 20 includes first to fourth main body portions 21 to 24, and the first to fourth main body portions 21 to 24 are integrated to form an injection valve main body. The first to fourth main body portions 21 to 24 are arranged in this order in the axial direction of the fuel injection valve 20, and the fuel supplied from the common rail 11 to the first main body portion 21 is provided in the fourth main body portion 24. It injects from the injection hole 34. In the following description, the axial direction of the fuel injection valve 20 will be referred to as “vertical direction”, the first body portion 21 side of the fuel injection valve 20 will be referred to as “upward direction”, and the fourth body portion 24 side will be referred to as “downward direction”. ..

The first main body 21 is provided with a first high pressure passage 13 and a low pressure chamber 57. The first high-pressure passage 13 is formed across the first body portion 21, the second body portion 22, and the third body portion 23, and penetrates the first to third body portions 21 to 23. The first high-pressure passage 13 is connected to the high-pressure pipe 12 at the end opposite to the second main body 22 side. As a result, the high-pressure fuel from the common rail 11 is supplied to the first high-pressure passage 13 via the high-pressure pipe 12. A fuel temperature sensor 74 that detects the temperature of the fuel in the first high pressure passage 13 and a fuel pressure sensor 75 that detects the fuel pressure are attached to the first high pressure passage 13. The detection signals of the fuel temperature sensor 74 and the fuel pressure sensor 75 are input to the ECU 90. The pressure of the high-pressure fuel supplied to the fuel injection valve 20 (hereinafter, also referred to as “injection pressure”) is detected by the fuel pressure sensor 75.

The low-pressure chamber 57 is formed at the boundary between the first main body 21 and the second main body 22 by denting the surface facing the second main body 22 upward. The high-pressure fuel in the first high-pressure passage 13 passes through the second main body portion 22, the third main body portion 23, and the fourth main body portion 24, and the low-pressure chamber 57 stores the fuel whose pressure has been reduced. The low pressure chamber 57 is connected to the return pipe 65 via the low pressure passage 58, and further connected to the fuel tank 61. As a result, part of the high pressure fuel supplied to the fuel injection valve 20 is returned from the low pressure chamber 57 to the fuel tank 61 through the return pipe 65. An opening/closing valve 50 that controls the fuel injection state of the fuel injection valve 20 is provided inside the low pressure chamber 57. The on-off valve 50 is of an electromagnetic drive type, and the opening and closing of the valve is controlled by the ECU 90.

The second main body 22 is provided with a second high pressure passage 14, an intermediate chamber 26, a first passage 25, and a second passage 27. The second high-pressure passage 14 is a branch passage that branches from the first high-pressure passage 13, and is a fuel passage to which the high-pressure fuel from the common rail 11 is supplied. The second high pressure passage 14 is provided with a pressure rising orifice 14a. The boost orifice 14a limits the flow rate of the fuel flowing through the second high pressure passage 14. In the second high pressure passage 14, an annular chamber 14b is formed at the end portion on the side opposite to the first high pressure passage 13. The annular chamber 14b is a fuel passage portion formed in an annular shape in the boundary portion of the second main body portion 22 with the third main body portion 23. The high pressure fuel from the first high pressure passage 13 is introduced into the annular chamber 14b through the second high pressure passage 14.

The intermediate chamber 26 is a cylindrical chamber, and is formed at the boundary between the second main body 22 and the third main body 23. The first passage 25 extends in the axial direction (vertical direction) of the fuel injection valve 20 inside the second main body portion 22 and penetrates the second main body portion 22. The first passage 25 has one end communicating with the low pressure chamber 57 and the other end communicating with the intermediate chamber 26. As a result, the intermediate chamber 26 communicates with the low pressure chamber 57 via the first passage 25.

The second passage 27 is formed inside the second main body portion 22 and extends in the same direction (vertical direction) as the first passage 25. The second passage 27 penetrates through the second main body 22, one end of which communicates with the low-pressure chamber 57, and the other end of which communicates with the first control chamber 46 of the third main body 23. .. A decompression orifice 27 a is provided in the second passage 27 at a position close to the first main body portion 21. The pressure reducing orifice 27a limits the flow rate of the fuel flowing through the second passage 27.

The first body 23 is provided with a first control chamber 46 and a connection passage 47. The first control chamber 46 is a chamber formed inside the injection valve body by denting the surface facing the second body portion 22 downward, and is in communication with the annular chamber 14b. The high pressure fuel from the first high pressure passage 13 is supplied to the first control chamber 46 via the second high pressure passage 14.

Inside the first control chamber 46, a driven valve 41 which is displaceable in the axial direction (vertical direction) of the fuel injection valve 20 is arranged. The driven valve 41 has a cylindrical shape, and has a third passage 42 formed in the center thereof so as to penetrate therethrough in the axial direction. The third passage 42 has an opening on the side of the second main body 22 that is open to the intermediate chamber 26, and an opening on the side of the fourth main body 24 that is open to the inside of the first control chamber 46. The third passage 42 is provided with a decompression orifice 42a. The flow rate of the fuel flowing through the third passage 42 is limited by the pressure reducing orifice 42a. The fuel flow rate on the outlet side of the pressure reducing orifice 27a included in the second passage 27 is set to be smaller than the fuel flow rate on the outlet side of the pressure reducing orifice 42a.

A spring 45 is attached to the driven valve 41 to bias the driven valve 41 toward the second main body portion 22 (upward). The driven valve 41 is in contact with the lower surface of the second main body portion 22 by the upward force due to the fuel pressure inside the first control chamber 46 and the biasing force of the spring 45. In this contact state, the driven valve 41 blocks the communication between the annular chamber 14b and the first control chamber 46, while the intermediate chamber 26 communicates with the first control chamber 46 through the third passage 42. Become. In this state, the fuel in the first control chamber 46 can flow into the low pressure chamber 57 via the third passage 42, the intermediate chamber 26 and the first passage 25.

In the state where the driven valve 41 is in contact with the lower surface of the second body portion 22, the fuel pressure inside the first control chamber 46 decreases, and the upward force due to the fuel pressure inside the first control chamber 46 and When the biasing force of the spring 45 falls below the downward force due to the fuel pressure inside the annular chamber 14b and the intermediate chamber 26, the driven valve 41 is displaced in the direction away from the lower surface of the second main body portion 22. As a result, the intermediate chamber 26 communicates with the first control chamber 46 without passing through the third passage 42, and the annular chamber 14b communicates with the first control chamber 46.

The second passage 27 directly connects the low pressure chamber 57 and the first control chamber 46. That is, the first control chamber 46 communicates with the low pressure chamber 57 via the second passage 27 regardless of the position (lifted state) of the driven valve 41. Further, a connection passage 47 extending from the first control chamber 46 to the fourth body portion 24 is formed in the third body portion 23. The connection passage 47 is provided with an orifice 47a, and the orifice 47a limits the flow rate of the fuel flowing through the connection passage 47.

The fourth body 24 is provided with a cylinder 35, a nozzle needle 31, a high pressure chamber 33, and a second control chamber 36. A plurality of injection holes 34 for injecting fuel toward the outside are formed at the tip of the cylinder 35. The nozzle needle 31 is housed inside the cylinder 35 so as to be capable of reciprocating in the vertical direction. A spring 32 that biases the nozzle needle 31 downward is attached to the upper surface of the nozzle needle 31.

The high pressure chamber 33 is provided in the middle of the passage that connects the first high pressure passage 13 and the injection hole 34. Inside the high pressure chamber 33, the tip of the nozzle needle 31 is arranged. The second control chamber 36 is provided inside the cylinder 35 on the side opposite to the injection hole 34 (above the nozzle needle 31). The second control chamber 36 communicates with the first control chamber 46 via a connection passage 47. As a result, the high-pressure fuel from the first high-pressure passage 13 is supplied to the second control chamber 36 via the first control chamber 46 and the connection passage 47. The fuel pressure inside the second control chamber 36 and the urging force of the spring 32 attached to the nozzle needle 31 act on the nozzle needle 31, whereby the nozzle needle 31 is displaced downward, and fuel is injected from the injection hole 34. The fuel is not injected, that is, the fuel injection valve 20 is closed.

Further, when the fuel pressure inside the high pressure chamber 33 becomes larger than the total force of the fuel pressure inside the second control chamber 36 and the urging force of the spring 32, the nozzle needle 31 is displaced upward and the fuel injection valve 20 is opened. When the fuel injection valve 20 is opened, the high pressure fuel in the high pressure chamber 33 is injected from the injection hole 34.

Next, the structure of the on-off valve 50 will be described. The on-off valve 50 is arranged inside the low pressure chamber 57 in the fuel passage that connects the first control chamber 46 and the low pressure chamber 57. The on-off valve 50 regulates the fuel pressure inside the first control chamber 46 by allowing and blocking the outflow of fuel from the first control chamber 46 to the low pressure chamber 57 under drive control by the ECU 90.

The opening/closing valve 50 has a first opening/closing valve 51 and a second opening/closing valve 52. The first opening/closing valve 51 is arranged on the first passage 25, and the open/close state thereof is controlled to switch between communication and cutoff between the low pressure chamber 57 and the first passage 25. The second opening/closing valve 52 is arranged on the second passage 27, and the open/close state of the second opening/closing valve 52 is controlled to switch the communication between the low pressure chamber 57 and the second passage 27 and the disconnection thereof. The ECU 90 independently controls the open/closed state of the first open/close valve 51 and the open/closed state of the second open/close valve 52 by energizing the first solenoid 53 and the second solenoid 54 independently of each other.

Specifically, when the first solenoid 53 is not energized, the first opening/closing valve 51 is in contact with the second body portion 22 by the urging force of the first spring 55. In this abutting state, the first on-off valve 51 blocks the communication between the low pressure chamber 57 and the first passage 25 (valve closed state). When the first solenoid 53 is energized while the first opening/closing valve 51 is closed, the first opening/closing valve 51 moves upward against the biasing force of the first spring 55 and is separated from the second main body portion 22. To do. In this state, the low pressure chamber 57 and the first passage 25 are in communication with each other (valve open state), and the fuel is allowed to flow from the first passage 25 into the low pressure chamber 57.

Further, when the second solenoid 54 is not energized, the second opening/closing valve 52 is in contact with the second body portion 22 by the urging force of the second spring 56. In this abutting state, the communication between the low pressure chamber 57 and the second passage 27 is blocked by the second opening/closing valve 52 (valve closed state). Further, when the second solenoid 54 is energized in the closed state of the second opening/closing valve 52, the second opening/closing valve 52 moves upward against the biasing force of the second spring 56 and is separated from the second main body portion 22. To do. In this state, the low pressure chamber 57 and the second passage 27 are in communication with each other (valve open state), and the inflow of fuel from the second passage 27 into the low pressure chamber 57 is allowed.

In the fuel injection control, the ECU 90 moves the nozzle needle 31 to the valve opening position and valve closing position by switching the valve opening and closing of the first opening/closing valve 51. As a result, in the fuel injection valve 20, the injection operation of injecting the fuel from the injection hole 34 and the injection stop operation of stopping the injection of the fuel are switched. Further, the ECU 90 variably controls the speed at which the nozzle needle 31 moves in the axial direction, that is, the needle speed, by switching the open/closed state of the second open/close valve 52 in accordance with the drive control of the first open/close valve 51. The ECU 90 independently controls the opening/closing of the first opening/closing valve 51 and the second opening/closing valve 52 to control the inclination of the fuel injection rate, more specifically, the rising speed and the falling speed of the injection rate, respectively. To do.

FIG. 2 shows an example of the injection rate pattern of the fuel injection valve 20. In any of the injection rate patterns, the first opening/closing valve 51 is opened at the start of fuel injection by the fuel injection valve 20, and the first opening/closing valve 51 is closed at the end of fuel injection. The open/close state of the second on-off valve 52 is controlled according to the rising speed and the falling speed of the injection rate.

Specifically, in the high-speed valve opening mode in which the rising rate of the injection rate at the start of fuel injection is made steep, the second opening/closing valve 52 is opened (see FIGS. 2A and 2C), and the injection rate In the low speed valve opening mode in which the rising speed is slow, the second opening/closing valve 52 is closed (see FIGS. 2B and 2D). Further, in the high-speed valve closing mode in which the falling rate of the injection rate at the end of fuel injection is made steep, the second opening/closing valve 52 is closed (see FIGS. 2A and 2B), and the injection rate falls. In the low speed valve closing mode in which the speed is slowed, the second opening/closing valve 52 is opened (see FIGS. 2C and 2D).

The relationship between the open/closed states of the first opening/closing valve 51 and the second opening/closing valve 52 and the operation of the fuel injection valve 20 will be described with reference to FIGS. 3 to 8. Before the start of injection, by deenergizing the first solenoid 53 and the second solenoid 54, both the first opening/closing valve 51 and the second opening/closing valve 52 are closed as shown in FIG. The communication between the high pressure chamber 33 and the injection hole 34 is blocked.

The case of the injection pattern in the high speed valve opening mode and the high speed valve closing mode (see FIG. 2A) will be described with reference to FIGS. Before the start of injection, when the first on-off valve 51 and the second on-off valve 52 are closed, high-pressure fuel is introduced from the first high-pressure passage 13 to the second to fourth body portions 22 to 24. The formed fuel storage portion (annular chamber 14b, intermediate chamber 26, first control chamber 46, second control chamber 36, high pressure chamber 33) and fuel passage (first passage 25, second passage 27, third passage 42, The connection passage 47) is maintained at a high pressure state equivalent to the fuel pressure in the first high pressure passage 13 (see FIG. 3).

When the first opening/closing valve 51 and the second opening/closing valve 52 are both closed by energizing the first solenoid 53 and the second solenoid 54 in the state where the first opening/closing valve 51 and the second opening/closing valve 52 are closed, as shown in FIG. As shown in, the first control chamber 46 communicates with the low pressure chamber 57 via the first passage 25, the third passage 42, and the second passage 27. As a result, the fuel inside the first control chamber 46 and the second control chamber 36 passes through two routes, a route passing through the first passage 25 and the third passage 42 and a route passing through the second passage 27. Flow into the low pressure chamber 57. Therefore, the fuel pressure inside the first control chamber 46 and the second control chamber 36 decreases at high speed, and the nozzle needle 31 is displaced at high speed in the valve opening direction (upward direction). As a result, fuel is injected from the injection hole 34. In this case, the injection rate rises at a high speed as shown in FIG.

A differential pressure is generated before and after the decompression orifice 42a, and the sum of the upward force due to the fuel pressure inside the first control chamber 46 and the biasing force of the spring 45 is the inside of the intermediate chamber 26 and the annular chamber 14b. It is higher than the downward force due to fuel pressure. Therefore, the driven valve 41 is kept in contact with the second main body portion 22 when both the first opening/closing valve 51 and the second opening/closing valve 52 are open (see FIG. 4 ).

When the first opening/closing valve 51 is closed after the injection rate reaches the maximum, the fuel in the first control chamber 46 flows into the intermediate chamber 26 via the third passage 42, so that the inside of the intermediate chamber 26 The fuel pressure rises (see FIG. 5). Further, by closing the second opening/closing valve 52, the communication between the low pressure chamber 57 and the first control chamber 46 is cut off. In this case, the downward force due to the fuel pressure inside the intermediate chamber 26 and the annular chamber 14b becomes larger than the total of the upward force due to the fuel pressure inside the first control chamber 46 and the biasing force of the spring 45. As a result, the driven valve 41 moves downward (see FIG. 6). The downward movement of the driven valve 41 causes the high-pressure fuel in the first high-pressure passage 13 to flow into the first control chamber 46.

At this time, since the first opening/closing valve 51 and the second opening/closing valve 52 are both closed, the fuel pressure inside the first control chamber 46 rises at a high speed. When the fuel flows from the first control chamber 46 into the second control chamber 36 through the connection passage 47 and the fuel pressure inside the second control chamber 36 becomes higher than a predetermined pressure, the nozzle needle 31 starts to descend and the valve is closed. The operation shifts (see FIG. 6). In this case, as shown in FIG. 2A, the injection rate falls at a high speed. Thereafter, the nozzle needle 31 is seated on the seat portion (not shown), so that the fuel injection by the fuel injection valve 20 is stopped.

Next, the case of the injection pattern in the low speed valve opening mode and the high speed valve closing mode (see FIG. 2B) will be described. Before the start of injection, in the state where the first opening/closing valve 51 and the second opening/closing valve 52 are closed (see FIG. 3 ), the second opening/closing valve 52 is maintained in the closed state as shown in FIG. When the on-off valve 51 is opened, the fuel inside the first control chamber 46 flows into the intermediate chamber 26 via the third passage 42 and the first passage 25. At this time, a differential pressure is generated before and after the decompression orifice 42a, and the sum of the upward force due to the fuel pressure inside the first control chamber 46 and the urging force of the spring 45 is the intermediate chamber 26 and the annular chamber 14b. It is higher than the downward force due to the internal fuel pressure. Therefore, the driven valve 41 is maintained in a state of being in contact with the second main body portion 22.

When the second opening/closing valve 52 is closed, the flow of fuel through the second passage 27 is not permitted, so the fuel pressure inside the first control chamber 46 decreases at a low speed, and the nozzle needle 31 moves at a low speed. Displaces in the valve opening direction. In this case, as shown in FIG. 2B, the injection rate rises at a low speed. That is, the rate of increase (inclination) of the injection rate when the first opening/closing valve 51 is open and the second opening/closing valve 52 is closed is the injection rate when the first opening/closing valve 51 and the second opening/closing valve 52 are both open. Is smaller than the rising speed (slope) of. After the injection rate reaches the maximum, the operation is the same as the operation at the time of high speed fall shown in FIG.

Next, the case of the injection pattern in the high speed valve opening mode and the low speed valve closing mode (see FIG. 2C) will be described. First, the operation at high speed startup is similar to the operation at high speed startup shown in FIG. After the injection rate reaches the maximum, as shown in FIG. 8, when the second opening/closing valve 52 is maintained in the open state and the first opening/closing valve 51 is closed, the fuel in the first control chamber 46 passes through the third passage. It flows into the intermediate chamber 26 via 42, and the fuel pressure inside the intermediate chamber 26 rises. Further, since the second opening/closing valve 52 is in the open state, the fuel inside the first control chamber 46 flows into the low pressure chamber 57 via the second passage 27. The fuel pressure inside the intermediate chamber 26 rises, and the downward force due to the fuel pressure inside the intermediate chamber 26 and the annular chamber 14b increases the upward force due to the fuel pressure inside the first control chamber 46 and the spring 45. When it becomes larger than the total of the urging forces, the driven valve 41 moves downward (see FIG. 9). The downward movement of the driven valve 41 causes the high-pressure fuel in the first high-pressure passage 13 to flow into the first control chamber 46.

At this time, since the second opening/closing valve 52 is maintained in the open state, the fuel pressure inside the first control chamber 46 rises at a low speed. When the fuel flows from the first control chamber 46 into the second control chamber 36 through the connection passage 47 and the fuel pressure inside the second control chamber 36 becomes higher than a predetermined pressure, the nozzle needle 31 starts to descend and the valve is closed. The operation shifts (see FIG. 9). In this case, as shown in FIG. 2C, the injection rate falls at a low speed. That is, the rate of decrease (inclination) of the injection rate when the first opening/closing valve 51 is closed and the second opening/closing valve 52 is open is the injection rate when both the first opening/closing valve 51 and the second opening/closing valve 52 are closed. Is smaller than the decreasing speed (slope) of. After that, the nozzle needle 31 is seated on the seat portion, so that fuel is not injected from the injection hole 34.

FIG. 10 is a diagram showing an operation in the pressure reducing valve mode in which the second on-off valve 52 reduces the fuel pressure in the common rail 11 without injecting fuel from the fuel injection valve 20.

As described above, when both the first on-off valve 51 and the second on-off valve 52 are closed, the fuel pressure inside the second control chamber 36, the first control chamber 46, and the intermediate chamber 26 is equal to that of the first high-pressure passage 13. The fuel pressure is equal to the internal fuel pressure, and the driven valve 41 is in contact with the second body portion 22 (see FIG. 3 ). In the pressure reducing operation, the second opening/closing valve 52 is opened from this state. As a result, as shown in FIG. 10, the fuel in the first control chamber 46 is discharged to the low pressure chamber 57 via the second passage 27, and the driven valve 41 is lowered as the pressure inside the first control chamber 46 decreases. Move in the direction.

In the fuel injection valve 20, in the state where the first opening/closing valve 51 is closed and the second opening/closing valve 52 is opened, the flow rate of fuel through the pressure increasing orifice 14a is larger than the flow rate of fuel through the pressure reducing orifice 27a. It is set. Therefore, when the first opening/closing valve 51 is closed and the second opening/closing valve 52 is opened, the pressure loss of the fuel discharged from the inside of the first control chamber 46 through the second passage 27 in the second passage 27 is reduced. In this case, the pressure loss of the fuel flowing from the second high pressure passage 14 into the first control chamber 46 becomes larger than the pressure loss in the second high pressure passage 14. As a result, when the first opening/closing valve 51 is closed and the second opening/closing valve 52 is opened, the nozzle needle 31 blocks the high pressure chamber 33 from the injection hole 34, that is, the fuel is injected from the injection hole 34. The state that is not done is maintained.

In addition, fuel flows from the common rail 11 into the first control chamber 46 via the first high pressure passage 13 and the second high pressure passage 14, and the inflow fuel is discharged from the first control chamber 46 to the low pressure chamber 57 to inject fuel. By returning to the upstream side (low pressure side) of the system, the fuel pressure inside the common rail 11 decreases. That is, the fuel pressure in the common rail 11 is reduced in a state where fuel is not injected from the fuel injection valve 20. Therefore, the fuel injection valve 20 has a function as a pressure reducing valve that reduces the fuel pressure in the common rail 11.

In the fuel injection valve 20, when the first passage 25 and the low pressure chamber 57 communicate with each other by the first opening/closing valve 51, the driven valve 41 blocks communication between the annular chamber 14b and the first control chamber 46. As described above, the flow passage area of the decompression orifice 42a, the opening area of the intermediate chamber 26 on the side of the third main body portion 23 (first control chamber 46), and the side of the third main body portion 23 (first control chamber 46) of the annular chamber 14b. The opening area and the biasing force of the spring 45 are set. That is, when the first passage 25 and the low pressure chamber 57 are communicated with each other by the first opening/closing valve 51, the first control chamber 46 and the intermediate chamber 26 are communicated with each other by the driven valve 41 via the third passage 42. This is achieved by limiting the fuel flow rate by the decompression orifice 42a, the exposed area of the driven valve 41 to the intermediate chamber 26, the exposed area of the driven valve 41 to the first high pressure passage 13, and the biasing force set by the spring 45. ing.

The ECU 90 controls the fuel injection rate of the fuel injection valve 20 based on the operating state of the engine 70 in which the fuel injection valve 20 is mounted (for example, engine speed, engine load, etc.) and rail pressure. Specifically, the ECU 90 selects one of the high-speed valve opening mode and the low-speed valve opening mode as the injection rate pattern at the start of injection, and selects the high-speed valve closing mode and the low-speed valve closing mode as the injection rate pattern at the time of injection end. Select one (see FIG. 2). Then, the open/closed states of the first opening/closing valve 51 and the second opening/closing valve 52 are controlled according to the selected modes. Alternatively, the ECU 90 causes the injection rate at the start of fuel injection (that is, the rising rate of the injection rate) and the injection rate at the end of fuel injection (that is, the fall of the injection rate) according to the engine operating state and the rail pressure. Injection control is performed in which at least one of (speed) is changed during the time until the injection rate becomes maximum.

Here, in order to improve the response of the nozzle needle 31 to the drive command of the fuel injection valve 20, it is desirable to increase the rectangularity of the injection rate waveform. However, in order to increase the rectangularity of the injection rate waveform, the nozzle needle 31 is moved at high speed at the start or end of fuel injection. In this case, at the start of injection, the nozzle needle 31 reaches the full lift limit early (see the broken line R in FIG. 11), and at the end of injection, the nozzle needle 31 reaches the valve closing position early. Therefore, there is a concern that the amount of fuel injected from the fuel injection valve 20 by one time of fuel injection will decrease and the degree of freedom of injection will decrease.

Therefore, in the present embodiment, at least one of the start and the end of fuel injection by the fuel injection valve 20, the nozzle needle 31 reaches the maximum lift position from the closed position or the maximum lift position to the closed position. The control for changing the lift speed (speed change control) is to be executed on the way to the point of reaching. Specifically, a lift increasing period in which the lift amount is changed to the increasing side in response to the valve opening command of the fuel injection valve 20 and a lift decreasing period in which the lift amount is changed to the decreasing side in response to the valve closing command of the fuel injection valve 20. In at least one of them, the needle speed is controlled at a high speed during a period in which the lift amount of the nozzle needle 31 is relatively small, thereby ensuring responsiveness to the drive command. Further, during a period in which the lift amount of the nozzle needle 31 is relatively large, the needle speed is controlled at a low speed to realize a large injection amount by the fuel injection valve 20.

The speed change control of the nozzle needle 31 will be described with reference to the time chart of FIG. In FIG. 11, (a) is a transition of the valve opening command and valve closing command (INJ drive command) of the fuel injection valve 20, (b) is a transition of the needle speed command, and (c) is a transition of the lift amount of the nozzle needle 31. , (D) shows the transition of the injection rate, and (e) shows the transition of the pressure detected by the fuel pressure sensor 75.

The microcomputer of the ECU 90 controls the open/closed states of the first opening/closing valve 51 and the second opening/closing valve 52 according to the injection rate mode in response to the valve opening command of the fuel injection valve 20. Here, the high speed valve opening mode and the high speed valve closing mode are selected as the injection rate mode. Therefore, the ECU 90 opens both the first opening/closing valve 51 and the second opening/closing valve 52 according to the valve opening command of the fuel injection valve 20. When both the first opening/closing valve 51 and the second opening/closing valve 52 are opened, the nozzle needle 31 is displaced at the first speed V1 in the direction of increasing the lift amount.

When a predetermined delay time elapses from the valve opening command timing (time t51) of the fuel injection valve 20, the nozzle needle 31 starts to be displaced toward the valve opening side of the injection hole 34 (that is, the direction in which the lift amount is increased). Further, the injection rate gradually increases with the displacement of the nozzle needle 31. Then, at a timing (time t52) when the speed switching time T1 has elapsed from time t51, the second opening/closing valve 52 is closed while the first opening/closing valve 51 is opened. In the state where the first opening/closing valve 51 is opened and the second opening/closing valve 52 is closed, the nozzle needle 31 is displaced in the direction of increasing the lift amount at the second speed V2 lower than the first speed V1. .. Therefore, at time t52, the lift speed of the nozzle needle 31 is switched from the high speed first speed V1 to the low speed second speed V2.

The speed switching time T1 is the time required for the injection rate to change from zero to the maximum injection rate Dmax when both the first opening/closing valve 51 and the second opening/closing valve 52 are opened. The speed switching time T1 is calculated based on the engine operating state (specifically, the engine rotation speed and the engine load) and the injection pressure. At the time when the injection rate reaches the maximum injection rate Dmax (time t52), the nozzle needle 31 is located at the intermediate position LTH between the valve closing position and the full lift limit.

After that, when the needle closing command time T2 has elapsed from the time t51 and the valve closing command of the fuel injection valve 20 is input, the microcomputer of the ECU 90 causes the microcomputer of the first opening/closing valve 51 and the second opening/closing valve 52 to operate according to the injection rate mode. The open/closed state is controlled (time t53). Here, the first opening/closing valve 51 is closed while the second opening/closing valve 52 is open in accordance with the closing command of the fuel injection valve 20. In the state where the first opening/closing valve 51 is closed and the second opening/closing valve 52 is opened, the nozzle needle 31 is displaced at the third speed V3 in the direction of decreasing the lift amount.

The needle closing command time T2 is a value calculated based on the engine operating state (engine speed, engine load) and rail pressure (or injection pressure), and is injected by the fuel injection valve 20 by one fuel injection. It is the time corresponding to the required value of the fuel amount (hereinafter, also referred to as “required injection amount”). The larger the required injection amount, the longer the needle closing valve command time T2 is set.

After that, when the speed switching time T3 has elapsed from the valve opening command timing (time t51) of the fuel injection valve 20 (time t53), the second on-off valve 52 is closed while the first on-off valve 51 is closed. .. In a state where both the first opening/closing valve 51 and the second opening/closing valve 52 are closed, the nozzle needle 31 is displaced in the direction of decreasing the lift amount at the fourth speed V4 which is higher than the third speed V3. Therefore, at time t52, the lift speed of the nozzle needle 31 is switched from the low third speed V3 to the high fourth speed V4. The third speed V3 and the fourth speed V4 represent deceleration, and the third speed V3 is a value on the lower speed side (small deceleration) than the fourth speed V4.

The speed switching time T3 is until the nozzle needle 31 reaches the intermediate position LTH when the first opening/closing valve 51 is closed and the second opening/closing valve 52 is opened in accordance with the closing command of the fuel injection valve 20. Is a total time of the time required for and the needle closing command time T2. The speed switching time T3 is calculated based on the engine operating state (specifically, the engine rotation speed and the engine load) and the injection pressure. After that, the nozzle needle 31 returns to the seat portion (valve closing position), so that the fuel injection from the fuel injection valve 20 is stopped.

It can be said that the flexibility of fuel injection can be improved if the upper limit of the amount of fuel that can be injected by a single fuel injection from the fuel injection valve 20 can be expanded. For that purpose, it is desirable to lengthen the period of the injection hole throttle region in which the injection rate is controlled at the maximum injection rate Dmax as long as possible while the fuel is being injected from the fuel injection valve 20 (see FIG. 11 ). In this respect, according to the above control for switching the lift speed from high speed to low speed at the start of fuel injection or switching the lift speed from low speed to high speed at the end of injection, the period of the injection hole throttle region can be made as long as possible. it can. As a result, it is possible to increase the injection amount by one fuel injection from the fuel injection valve 20. The region where the lift amount is larger than the intermediate position LTH corresponds to the “first lift region”, and the region where the lift amount is smaller than the intermediate position LTH corresponds to the “second lift region”.

Here, the lift speed of the nozzle needle 31 changes according to various parameters. In consideration of this point, further, in the present embodiment, the switching timing TL for switching the lift speed between the high speed and the low speed (that is, the speed switching times T1, T3) based on the correlation parameter that correlates with the lift speed of the nozzle needle 31. ) Is variably controlled. In this embodiment, the following elements (1) and (2) are used as correlation parameters.
(1) Pressure of high-pressure fuel supplied to the fuel injection valve 20 (injection pressure)
(2) Fuel temperature

Further, in the present embodiment, it is noted that the lift speed of the nozzle needle 31 has a variation factor, and the switching timing TL is variably controlled based on the following elements (3) to (5). ..
(3) Velocity variation due to individual difference of fuel injection valve (4) Velocity variation due to difference in injection interval (5) Velocity variation due to deterioration over time and engine operating conditions Below, regarding the relationship between each element and switching timing TL, The injection start time will be described as an example with reference to FIGS. 11 to 15.

(1) Injection pressure The lift speed of the nozzle needle 31 changes according to the injection pressure. Specifically, at the start of fuel injection, the higher the injection pressure, the higher the lift speed. This is because the higher the injection pressure is, the greater the force with which the high pressure fuel supplied from the common rail 11 to the high pressure chamber 33 pushes up the nozzle needle 31, and the easier it is for the nozzle needle 31 to move upward.

If the lift speed of the nozzle needle 31 is kept high, the nozzle needle 31 reaches the full lift limit at an early timing (see the broken line R in FIG. 12). Further, the higher the injection pressure is, the more easily the nozzle needle 31 is displaced upward and the easier it is to reach the full lift limit. Therefore, at the start of fuel injection, the higher the injection pressure, the earlier the lift speed switching timing TL is set. Specifically, as shown in FIG. 12, when there is a command to open the fuel injection valve 20 at time t11, if the injection pressure is relatively low, as shown by the alternate long and short dash line in FIG. Switch the lift speed from high speed to low speed. On the other hand, when the injection pressure is relatively high, as shown by the solid line in FIG. 12, the lift speed is switched from high speed to low speed at a timing earlier than time t13 (time t12). The injection pressure may be detected by either the rail pressure sensor 73 or the fuel pressure sensor 75.

At the end of fuel injection, the lift speed is switched from low speed to high speed at the timing when the nozzle needle 31 reaches the intermediate position LTH. Here, at the end of fuel injection, the higher the injection pressure, the greater the force with which the nozzle needle 31 is pushed up by the high-pressure fuel supplied from the common rail 11 to the high-pressure chamber 33, and the nozzle needle 31 moves downward. It gets harder. That is, the lower the injection pressure is, the easier the nozzle needle 31 is to move downward. In this case, the lower the injection pressure, the earlier the nozzle needle 31 reaches the intermediate position LTH. Therefore, at the end of fuel injection, the lift speed switching timing TL is set such that the lift speed is switched in a shorter time from the valve closing command of the fuel injection valve 20 as the injection pressure is lower. As a result, the valve closing response is ensured while increasing the fuel injection amount that can be injected from the fuel injection valve 20 by one fuel injection.

(2) Fuel Temperature The lift speed of the nozzle needle 31 changes according to the temperature of the fuel supplied to the fuel injection valve 20. Specifically, at the start of fuel injection, the higher the fuel temperature, the lower the fuel viscosity and the higher the lift speed. Focusing on this point, in the present embodiment, the higher the fuel temperature is, the earlier the switching timing TL of the lift speed is set. Specifically, as shown in FIG. 13, when there is a valve opening command for the injection hole 34 at time t31, when the fuel temperature detected by the fuel temperature sensor 74 is relatively low, the chain line in FIG. As shown by, the lift speed is switched from high speed to low speed at time t33. On the other hand, when the fuel temperature detected by the fuel temperature sensor 74 is relatively high, as shown by the solid line in FIG. 13, the lift speed is changed from high speed to low speed at a timing (time t32) earlier than time t33. Switch to.

At the end of fuel injection, the higher the fuel temperature, the faster the nozzle needle 31 is displaced downward. Therefore, at the end of fuel injection, the lift speed switching timing TL is set such that the lift speed is switched in a shorter time from the valve closing command of the fuel injection valve 20 as the fuel temperature becomes higher.

(3) Speed Variation Due to Individual Difference of Fuel Injection Valve 20 The lift speed of the nozzle needle 31 has individual difference, and varies depending on each fuel injection valve 20. When the switching timing TL is set with reference to the fuel injection valve 20 having a slow lift speed, the fuel injection valve 20 having a high lift speed changes the lift position at the start of fuel injection before the lift speed is switched from the high speed to the low speed. There is concern that the full lift limit will be reached. Therefore, in the present embodiment, the injection characteristic information of each fuel injection valve 20 is stored in the storage unit in advance, and the stored injection characteristic information is read out and utilized to meet the individual difference of each fuel injection valve 20. The lift speed variation is corrected.

Specifically, as shown in FIG. 14, when there is a command to open the fuel injection valve 20 at time t21, one point is shown in FIG. 14 for an individual having an injection characteristic in which the lift speed at the start of injection is relatively slow. As indicated by the chain line, the lift speed is switched from high speed to low speed at time t23. On the other hand, as shown by the solid line in FIG. 14, the individual having the injection characteristic with the relatively high lift speed switches the lift speed from the high speed to the low speed at a timing earlier than the time t23 (time t22).

Similarly, at the end of fuel injection, the injection characteristic information of each fuel injection valve 20 is read and the switching timing TL is set according to the individual difference in lift speed. Specifically, for an individual having an injection characteristic with a relatively high lift speed at the end of injection, an individual having an injection characteristic with a relatively low lift speed can be processed in a shorter time from the valve closing command of the fuel injection valve 20. The lift speed switching timing TL is set so that the lift speed can be switched.

(4) Speed variation due to difference in injection interval When fuel injection is performed a plurality of times by the fuel injection valve 20 during one combustion cycle of the engine 70, the injection interval, that is, from the end of the pre-stage injection in the multi-stage injection to the post-stage injection. Due to the difference in the period up to the start, the amplitude of the fuel pressure pulsation at the start of injection differs. Further, the lift speed of the nozzle needle 31 at the time of injection start changes due to the difference in the amplitude of the fuel pressure pulsation at the time of injection start. Specifically, the lift speed becomes higher as the amplitude of the fuel pressure pulsation increases toward the positive side at the start of injection. Therefore, in the present embodiment, the lift timing switching timing TL at the start of injection is corrected to reflect the speed variation due to the difference in injection interval. In the present embodiment, the amplitude of the pressure pulsation at the injection interval is calculated according to the elapsed time from the end timing of the preceding injection, and the larger the calculated amplitude is on the positive side, the more the fuel injection starts and the fuel injection end. The lift speed switching timing TL is set to an early timing.

Specifically, as shown in FIG. 15, when there is a command to open the fuel injection valve 20 at time t41, and when the amplitude of the fuel pressure pulsation at the start of injection is relatively small, as shown by the alternate long and short dash line in FIG. Then, at time t43, the lift speed is switched from high speed to low speed. On the other hand, when the amplitude of the fuel pressure pulsation at the start of injection is relatively large, as shown by the solid line in FIG. 15, the lift speed is switched from high speed to low speed at a timing earlier than time t43 (time t42).

(5) Deterioration with time and speed variation due to engine operating conditions When the lift speed of the nozzle needle 31 is deviated due to deterioration with time or engine operating conditions, the deviation appears in the injection rate. Specifically, when the lift speed becomes slow due to a change with time or the like, the time from when the fuel injection valve 20 is instructed to open the valve until it reaches the injection hole throttle region, and when the fuel injection valve 20 is instructed to close the valve After that, it takes a long time to pass through the injection hole restriction region. Therefore, in the present embodiment, a transition waveform of the injection rate is calculated using the pressure detected by the fuel pressure sensor 75 (see FIG. 11E), and a valve opening command is issued to the fuel injection valve 20 from the calculated transition waveform of the injection rate. After that, the time from when the fuel injection valve 20 reaches the injection hole restriction area and the time from when the fuel injection valve 20 is instructed to close the valve until the fuel injection valve 20 exits the injection hole restriction area are acquired. Then, the obtained value is used to perform feedback correction of the lift speed switching timing TL.

Next, the processing procedure of speed change control of the nozzle needle 31 at the start and end of fuel injection will be described using the flowchart of FIG. This processing is executed by the microcomputer of the ECU 90 every predetermined cycle (for example, every 180°C).

In FIG. 16, in step S101, it is determined based on the engine operating state (engine speed and engine load) whether or not there is a demand for a high rectangle to increase the rectangularity of the injection rate waveform. If there is a high rectangle request, the process proceeds to step S102, and the needle speed command value is set to "high speed".

Next, in step S103, it is determined whether the required injection amount of the fuel injection valve 20 is larger than the first threshold TH1. When the required injection amount is greater than the first threshold TH1, the process proceeds to step S104, and it is determined whether the required injection amount is greater than the second threshold TH2. Here, the second threshold TH2 is set to a value on the side where the required injection amount is larger than the first threshold TH1. In the present embodiment, when the required injection amount is larger than the first threshold value TH1, the lift speed is changed from the high speed to the low speed in the middle of the change of the lift amount from the increasing side to the decreasing side at the time of starting the fuel injection. Switch. Further, when the required injection amount is larger than the second threshold value TH2, the lift speed is switched from the high speed to the low speed during the change of the lift amount not only at the start of injection but also at the end of fuel injection.

If the required injection amount is greater than the second threshold TH2, an affirmative decision is made in step S104 and the operation proceeds to step S105. In step S105, the needle closing valve command time T2 is calculated based on the required injection amount and the rail pressure. As the needle closing command time T2, a longer time is set as the required injection amount is larger, and a shorter time is set as the rail pressure is higher.

In step S106, speed switching times T1 and T3 are calculated. FIG. 17 is a functional block diagram showing the calculation process of the speed switching times T1 and T3. The microcomputer of the ECU 90 first calculates the base time Tb as the basic amount of the speed switching times T1 and T3 based on the required injection amount and the injection pressure. Here, the base period setting map stored in advance is used to calculate the base time Tb by reading the time corresponding to the injection pressure detected by the fuel pressure sensor 75 and the required injection amount from the base period setting map. As the base time Tb, a base time Tb1 at the start of injection and a base time Tb3 at the end of injection are calculated.

Subsequently, the microcomputer of the ECU 90 corrects the base times Tb1 and Tb3 based on the injection characteristic information indicating the individual difference of each fuel injection valve 20, the fuel temperature, and the injection interval. Specifically, the correction value Ka of the speed switching time read from the injection characteristic information of each fuel injection valve 20, the correction value Kb read from the fuel temperature correction map using the fuel temperature detected by the fuel temperature sensor 74, and The base times Tb1 and Tb3 are corrected by the correction value Kc read from the injection interval correction map. Further, the microcomputer of the ECU 90 acquires the actual values of the speed switching times T1 and T3 from the detected injection rate waveform, and corrects the base times Tb1 and Tb3 with the feedback correction value Kd calculated based on the acquired actual values. Then, the values after correction by these correction values are set as speed switching times T1 and T3.

Returning to the description of FIG. 16, in step S107, a valve opening command is output to the fuel injection valve 20 at a predetermined injection start timing. The injection start timing is calculated based on the engine operating state each time. By this valve opening command, energization of the first solenoid 53 is started and the first opening/closing valve 51 is opened, and energization of the second solenoid 54 is started and the second opening/closing valve 52 is opened. It will be in the state of doing. As a result, the nozzle needle 31 is displaced at the first speed V1 toward the direction of opening the injection hole 34.

Next, in step S108, it is determined whether or not the speed switching time T1 has elapsed from the valve opening command of the fuel injection valve 20. On the condition that it is determined that the speed switching time T1 has elapsed from the valve opening command of the fuel injection valve 20, the process proceeds to step S109, and the command value of the needle speed is set to "low speed". As a result, the second opening/closing valve 52 is closed, and the needle speed is switched from the first speed V1 to the second speed V2.

In step S110, it is determined whether or not the needle closing command time T2 has elapsed from the valve opening command of the fuel injection valve 20, and the process proceeds to step S111 on the condition that the affirmative judgment is made in step S110. In step S111, the command value of the needle speed is set to "low speed", and in step S112, a command to close the fuel injection valve 20 is output. In accordance with this valve closing command, energization of the first solenoid 53 is stopped and energization of the first opening/closing valve 51 is closed while continuing energization of the second solenoid 54 (that is, with the second opening/closing valve 52 open). Be done. As a result, the nozzle needle 31 is displaced at the third speed V3 toward the direction of closing the injection hole 34.

Next, in step S113, it is determined whether or not the speed switching time T3 has elapsed from the opening command of the fuel injection valve 20. On the condition that the speed switching time T3 has elapsed from the valve opening command of the fuel injection valve 20, the process proceeds to step S114, and the command value of the needle speed is set to "high speed". As a result, the second opening/closing valve 52 is closed and the needle speed is switched from the third speed V3 to the fourth speed V4. When the nozzle needle 31 moves to the valve closing position, the fuel injection from the fuel injection valve 20 is stopped.

If the required injection amount is greater than the first threshold TH1 and less than or equal to the second threshold TH2, a negative determination is made in step S104 and the process proceeds to step S115. In this case, the control for switching the needle speed from the high speed to the low speed on the way is performed only at the time of starting the fuel injection among the start and end of the fuel injection.

That is, in step S115, the needle closing command time T2 is calculated based on the required injection amount and the rail pressure. In the following step S116, the speed switching time T1 is calculated in the same manner as the processing of step S106. Then, in steps S117 to S120, the same processing as steps S107 to S110 is executed. In the following step S121, the command value of the needle speed is set to "high speed", and the valve closing command of the fuel injection valve 20 is output in step S122. Then, this routine is finished.

If the required injection amount is less than or equal to the first threshold value TH1, a negative determination is made in step S103 and the process proceeds to step S123. In this case, the speed change control is not executed at the time of starting and ending the fuel injection, and the needle speed is controlled at a high speed.

That is, in step S123, the needle closing command time T2 is calculated based on the required injection amount and the rail pressure. In subsequent step S124, a valve opening command is output to the fuel injection valve 20 at a predetermined injection start timing. Thereafter, in step S125, it is determined whether or not the needle closing command time T2 has elapsed from the valve opening command of the fuel injection valve 20, and the process proceeds to step S126 on the condition that the affirmative judgment is made in step S125. In step S126, the command value of the needle speed is set to "high speed", and when the predetermined injection end timing is reached, the valve closing command of the fuel injection valve 20 is output in step S127. As a result, the energization of the first opening/closing valve 51 and the second opening/closing valve 52 is stopped.

When there is no request for a high rectangular injection rate, a negative determination is made in step S101 and the process proceeds to step S128. In step S128, the needle speed command value is set to "low speed". In step S129, the needle valve closing command time T2 is calculated based on the required injection amount and the rail pressure, and when the predetermined injection start timing is reached, the valve opening command of the fuel injection valve 20 is output in step S130. As a result, the first opening/closing valve 51 is opened while the second opening/closing valve 52 is closed. In subsequent steps S131 to S133, the same processing as steps S125 to S127 is executed, and this routine is finished.

According to this embodiment described in detail above, the following excellent effects can be obtained.

At least at one of the start and end of the fuel injection, during the period when the lift amount of the nozzle needle 31 is large, the lift speed of the nozzle needle 31 is controlled to be slower than during the period when the lift amount is small. As a result, the timing at which the nozzle needle 31 reaches the maximum lift position or the valve closing position can be delayed, and the valve opening period of the fuel injection valve 20 can be made as long as possible. Therefore, according to the above configuration, it is possible to increase the amount of fuel injected from the fuel injection valve 20 by one fuel injection while ensuring the responsiveness of the nozzle needle 31 to the drive command of the fuel injection valve 20.

Further, according to the above configuration, it is possible to increase the amount of fuel per fuel injection injected from the fuel injection valve 20 without increasing the size of the fuel injection valve 20.

Based on the required injection amount, speed change control is performed to switch the lift speed from high speed to low speed at least at one of injection start and injection end. Specifically, when the required injection amount is larger than the first threshold value TH1, the lift speed is switched from the high speed to the low speed during the injection start. Accordingly, when the required injection amount is relatively large, the fuel injection control can be performed so as to satisfy the required injection amount. On the other hand, when the required injection amount is less than or equal to the first threshold TH1, the control for switching the lift speed during the injection start and the injection end is not performed. Therefore, when the required injection amount is not so large and it is not necessary to increase the injection amount, the valve opening response and the valve closing response of the nozzle needle 31 can be prioritized.

Further, when the required injection amount is larger than the second threshold value TH2, the lift speed is switched midway at both the injection start and the injection end. Fuel injection can be performed so as to satisfy the injection amount.

(Other embodiments)
The present disclosure is not limited to the above embodiment and may be implemented as follows, for example.

In the above embodiment, the transition waveform of the injection rate is calculated using the pressure detected by the fuel pressure sensor 75, and the lift speed switching timing TL is feedback-corrected based on the calculated transition waveform of the injection rate. A lift sensor that detects the lift amount of the nozzle needle 31 is attached, and from the lift amount detected by the lift sensor, the time from when the fuel injection valve 20 is instructed to open the valve until it actually reaches the injection hole throttle region, and the fuel The time from when the injection valve 20 is instructed to close the valve to when it actually passes through the injection hole restriction region may be acquired, and the lift timing switching timing TL may be feedback-corrected using the acquired value.

In the above embodiment, (1) injection pressure, (2) fuel temperature, (3) speed variation due to individual difference of the fuel injection valve 20, (4) speed variation due to difference in injection interval, and (5) deterioration with time, Although the switching timing TL is variably controlled based on the speed variation due to the engine operating conditions, the switching timing TL may be variably controlled based on some of these (1) to (5).

The configuration of the fuel injection valve 20 is not limited to the configuration shown in FIG. For example, in the fuel injection valve 20 of FIG. 1, when the driven valve 41 blocks the first high pressure passage 13 and the first control chamber 46, the second passage 27 is formed inside the driven valve 41 and the third passage 27 is formed. It may be configured to communicate with the first control chamber 46 via a passage different from the passage 42. Alternatively, when the second passage 27 communicates with the intermediate chamber 26 and the driven valve 41 blocks the first high pressure passage 13 and the first control chamber 46, the second passage 27 connects the intermediate chamber 26 and the third passage 42. It may be configured to communicate with the first control chamber 46 via the.

Further, in the fuel injection valve 20 of FIG. 1, two or more opening/closing valves are provided as the second opening/closing valve 52 for adjusting the moving speed of the nozzle needle 31, and opening/closing of these two or more opening/closing valves are individually controlled. Thus, the moving speed of the nozzle needle 31 may be adjusted with higher accuracy. In this case, the flow rate of fuel through the pressure increasing orifice 14a is set to be larger than the total flow rate of fuel through the pressure reducing orifices provided in the fuel passages of the two or more on-off valves.

The fuel injection valve 20 may be any fuel injection valve capable of variably controlling the lift speed of the nozzle needle 31 based on the drive signal. Therefore, as a fuel injection system to which the present disclosure can be applied, a fuel including a plurality of valves (first opening/closing valve 51 and second opening/closing valve 52) as a pressure adjusting valve for adjusting the fuel pressure inside the first control chamber 46. It is not limited to the case of using the injection valve 20. For example, instead of the first opening/closing valve 51 and the second opening/closing valve 52, an opening/closing valve whose opening/closing state is controlled by energization control for the piezo actuator is provided, and the lift amount of the opening/closing valve is continuously controlled by energization control for the piezo actuator. By adjusting the fuel pressure in the control chamber, the lift speed of the nozzle needle 31 may be variably controlled. Alternatively, in the piezo injector, a plurality of discharge orifices are provided, and the fuel pressure in the control chamber is adjusted by switching the discharge of the fuel through the plurality of discharge orifices, whereby the lift speed of the nozzle needle 31 is variably controlled. It may be one.

The control unit and the method described in the present disclosure are provided by a dedicated computer provided by configuring a processor and a memory programmed to execute one or more functions embodied by a computer program, May be realized. Alternatively, the control unit and the method described in the present disclosure may be realized by a dedicated computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the control unit and the method thereof described in the present disclosure are based on a combination of a processor and a memory programmed to execute one or a plurality of functions and a processor configured by one or more hardware logic circuits. It may be realized by one or more configured dedicated computers. Further, the computer program may be stored in a computer-readable non-transition tangible recording medium as an instruction executed by a computer.

Although the present disclosure has been described according to the embodiments, it is understood that the present disclosure is not limited to the embodiments and the structure. The present disclosure also includes various modifications and modifications within an equivalent range. In addition, various combinations and forms, and other combinations and forms including only one element, more, or less than those, also fall within the scope and spirit of the present disclosure.

Claims

An injection control device for an internal combustion engine (70), which controls a fuel injection amount of a fuel injection valve (20) by changing a lift amount of a nozzle needle (31) for opening and closing the fuel injection valve (20). hand,
A drive control unit that variably controls the lift speed of the nozzle needle based on a drive signal,
The drive control unit changes the lift amount of the nozzle needle according to a valve opening command of the fuel injection valve and a lift increasing period in which the lift amount of the nozzle needle is changed to an increasing side, and the lift amount of the nozzle needle with a valve closing command of the fuel injection valve. In at least one of the lift reduction periods to be changed to the reduction side, in the period in which the nozzle needle is in the first lift region on the side closer to the full lift position, the second lift region on the side where the lift amount is smaller than the first lift region. An injection control device for an internal combustion engine, which performs speed change control for controlling the lift speed of the nozzle needle at a lower speed than during a certain period.
An injection amount calculation unit that calculates the required injection amount of the fuel injection valve based on the operating state of the internal combustion engine;
An injection amount determination unit that determines whether the required injection amount is greater than a predetermined injection amount,
Equipped with
The injection control device for an internal combustion engine according to claim 1, wherein the drive control unit executes the speed change control when the injection amount determination unit determines that the required injection amount is larger than the predetermined injection amount. ..
As the predetermined injection amount, a first threshold value and a second threshold value larger than the first threshold value,
The drive control unit determines whether the required injection amount is greater than the first threshold value and less than the second threshold value by the injection amount determination unit, among the lift increase period and the lift decrease period. In the lift increasing period and the lift decreasing period, when the speed change control is performed in the lift increasing period and the injection amount determining unit determines that the required injection amount is larger than the second threshold value. The injection control device for an internal combustion engine according to claim 2, which performs the speed change control.
A correlation detector that detects a correlation parameter that correlates to the lift speed,
The internal combustion engine according to any one of claims 1 to 3, wherein the drive control unit variably controls a timing of changing a lift speed of the nozzle needle in the speed change control based on the correlation parameter. Injection control device.
The fuel injection valve includes a control chamber (33, 36, 46) into which fuel is introduced,
The nozzle needle is displaced in a direction in which the fuel injection valve is opened and closed using the pressure of fuel in the control chamber,
The injection control device for an internal combustion engine according to claim 4, wherein a pressure of fuel introduced into the control chamber is included as the correlation parameter.
The fuel injection valve includes a control chamber (33, 36, 46) into which fuel is introduced,
The nozzle needle is displaced in a direction for opening and closing the fuel injection valve by utilizing the pressure of fuel in the control chamber,
The injection control device for an internal combustion engine according to claim 4, wherein the correlation parameter includes a temperature of fuel introduced into the control chamber.
Performing a plurality of fuel injections by the fuel injection valve during one combustion cycle of the internal combustion engine,
7. The drive control unit variably controls the timing of changing the lift speed of the nozzle needle in the speed change control based on the intervals of the plurality of fuel injections. An injection control device for an internal combustion engine as described.
A storage unit for storing injection characteristic information which is information relating to the injection characteristic of the fuel injection valve,
The internal combustion engine according to any one of claims 1 to 7, wherein the drive control unit variably controls a timing of changing a lift speed of the nozzle needle in the speed change control based on the injection characteristic information. Injection control device.
An injection rate detection unit for detecting an injection rate of the fuel injection valve is provided,
9. The drive control unit variably controls the timing of changing the lift speed of the nozzle needle in the speed change control, based on the injection rate detected by the injection rate detection unit. An injection control device for an internal combustion engine according to item.
A lift amount detector for detecting the lift amount of the nozzle needle,
10. The drive control unit variably controls the timing of changing the lift speed of the nozzle needle in the speed change control based on the lift amount detected by the lift amount detection unit. An injection control device for an internal combustion engine according to item.