JP4218630B2 - Fuel injection device for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel injection device for an internal combustion engine, particularly a diesel engine.

  A common rail system is known as a fuel injection device for an internal combustion engine. This common rail system includes a pressure accumulator (common rail) that stores fuel in a predetermined pressure state, and injects high pressure fuel supplied from the pressure accumulator into a cylinder of an internal combustion engine from an injector. It has excellent performance such as being able to be controlled independently. In recent years, there has been a demand for higher performance from such a common rail system in terms of exhaust gas purification and fuel consumption reduction, and it is necessary to increase the injection pressure. A known technique that can easily realize this has been proposed (see Patent Document 1).

  The fuel injection device described in Patent Literature 1 includes a “mechanism for controlling the opening / closing operation of the nozzle by hydraulic pressure”, which is an advantage of the common rail system, and a pressure increasing mechanism for increasing the pressure in the accumulator. By providing this pressure increasing mechanism, not only can injection be performed at a higher pressure, but both pressure increasing and injection can be controlled. As a result, it is possible to change the injection pressure in one injection cycle, and it is possible to realize a fine injection at a low pressure and a main injection at an ultra-high pressure, and an injection rate pattern can be optimized. Can be optimized.

However, in the above known technique (Patent Document 1), it is necessary to control two operations, that is, a pressure increasing operation and an injection operation independently, so that at least two actuators are required. There is a problem that the configuration of the system becomes complicated and the cost increases accordingly.
On the other hand, another system has been proposed that can more easily realize the same function as the above-described known technique (Patent Document 1) (see Patent Document 2).

FIG. 9 is a hydraulic circuit diagram of the fuel injection device described in Patent Document 2.
This fuel injection device has a control valve 100 driven by one actuator, and this control valve 100 is connected to a pressure intensifier 110 and a nozzle 120 by fuel passages 130 and 140, respectively. To the pressure accumulator 160. The control valve 100 is provided with a hydraulic port 101 connected to the fuel passages 130 and 140 and a low-pressure port 102 connected to the low-pressure side drain passage 170, and the valve body 103 is connected between the hydraulic port 101 and the low-pressure port 102. The valve is driven between a valve closing position where the gap is closed (the state shown in FIG. 9) and a valve opening position where the hydraulic port 101 and the low pressure port 102 communicate with each other.

  When the valve body 103 is driven to the valve closing position, the fuel pressure of the pressure accumulator 160 is supplied to the control chamber 111 of the pressure intensifier 110 and the back pressure chamber 121 of the nozzle 120. At this time, in the pressure booster 110, the hydraulic pressure on both the upper and lower sides is balanced with respect to the built-in hydraulic piston 112, so that the fuel supplied from the pressure accumulator 160 to the pressurizing chamber 113 through the fuel passage 180 is increased. There is no. On the other hand, the nozzle 120 receives the fuel pressure in the back pressure chamber 121, and a built-in needle (not shown) maintains a valve-closed state, so that injection is not performed.

Next, when the valve body 103 is driven to the valve open position, the hydraulic port 101 and the low pressure port 102 of the control valve 100 communicate with each other, so that the fuel pressure in the control chamber 111 and the back pressure chamber 121 passes through the control valve 100. Open to the low pressure side. Thereby, in the pressure intensifier 110, the pressure balance between the upper and lower sides of the hydraulic piston 112 is lost, and the hydraulic piston 112 moves downward in the figure, whereby the fuel in the pressurizing chamber 113 is increased and supplied to the nozzle 120. . Further, in the nozzle 120, the fuel pressure in the back pressure chamber 121 is lowered and the needle is lifted, so that the ultra-high pressure fuel supplied from the pressure intensifier 110 is injected.
Japanese Patent No. 2885076 JP 2003-106235 A

  However, in the fuel injection device described in Patent Document 2, the control chamber 111 of the pressure intensifier 110 and the back pressure chamber 121 of the nozzle 120 are always connected to the pressure accumulator 160. That is, regardless of whether the control valve 100 is open or closed, the control chamber 111 and the back pressure chamber 121 are always in communication with the pressure accumulator 160. For this reason, throttles 190, 200, 210 are provided in the fuel passages 130, 140, 150, respectively. However, even if these three throttles 190-210 are used, the throttles 190-210 affect each other. It is difficult to optimally control the operation of the intensifier 110 and the operation of the nozzle 120.

  The present invention has been made based on the above circumstances, and its purpose is to control the pressure increase operation of the pressure intensifier and the nozzle injection operation with high accuracy by a control valve driven by one actuator. It is an object of the present invention to provide a fuel injection device for an internal combustion engine that can prevent a decrease in the degree of freedom of control due to the fact that the number is made one.

(Invention of Claim 1)
The present invention relates to a hydraulic circuit having a fuel passage for supplying the fuel pressure of the accumulator to the control chamber and the back pressure chamber, and a fuel passage for opening the fuel pressure in the control chamber and the back pressure chamber to the low pressure side. , Built-in valve body driven by one two-position actuator, which selectively connects one of the high pressure side leading to the accumulator and the low pressure side leading to the fuel tank to connect to the hydraulic circuit Thus, the fuel injection device for an internal combustion engine includes a pressure intensifier and a control valve for controlling the operation of the nozzle, and the hydraulic circuit is connected in parallel between the control valve and the back pressure chamber of the nozzle. A fuel passage is provided, one of the fuel passages is provided with a check valve that allows the flow of fuel from the control valve toward the back pressure chamber and prevents the reverse flow, and the other fuel passage includes Allow fuel flow from back pressure chamber to control valve And, wherein the check valve or pressure valve is provided to prevent the backflow.

  According to the above configuration, when the fuel pressure of the accumulator is supplied to the back pressure chamber of the nozzle, the fuel flows through one fuel passage, and when the fuel pressure in the back pressure chamber is released to the low pressure side, Fuel flows in the other fuel passage. That is, since the fuel flows in different fuel passages when the fuel pressure is supplied to the back pressure chamber and when the fuel pressure in the back pressure chamber is released, the needle valve is closed as the pressure in the back pressure chamber increases. The speed and the valve opening speed of the needle accompanying the pressure release of the back pressure chamber can be set independently, and the injection rate pattern can be changed.

(Invention of Claim 2)
2. The fuel injection device for an internal combustion engine according to claim 1, wherein the control valve includes a switching port connected to the hydraulic circuit, an input port leading to the pressure accumulator, and a low pressure port connected to the low pressure side drain passage. The valve body cuts off between the low pressure port and the switching port and communicates between the input port and the switching port, and the valve body cuts off between the input port and the switching port. A two-position three-way valve that selectively switches between a hydraulic release mode that communicates between the low-pressure port and the switching port.

  According to the above configuration, the switching port selectively communicates with either the input port or the low-pressure port, and does not communicate with both ports (the input port and the low-pressure port) at the same time. Therefore, the pressure accumulator and the control chamber of the intensifier and the back pressure chamber of the nozzle do not always communicate with each other. When the hydraulic release mode is selected, that is, the fuel pressure in the control chamber and the back pressure chamber is released to the low pressure side. When this is done, the input port leading to the pressure accumulator is blocked by the valve body between the switching port and the low pressure port. Thereby, when the hydraulic pressure release mode is selected, the fuel in the pressure accumulator is not allowed to flow down to the low pressure side, and energy loss can be suppressed, so that a reduction in fuel consumption of the internal combustion engine can be prevented.

(Invention of Claim 3)
The fuel injection device for an internal combustion engine according to claim 1 or 2, wherein the hydraulic valve is switched to one of a valve closing mode for closing the other fuel passage and a valve opening mode for opening the other fuel passage. It is a two-way valve.
Since the hydraulic valve of the present invention only opens and closes the other fuel passage and does not need to switch the fuel flow direction, it can be configured as a simple two-position two-way valve and can be manufactured at low cost.

(Invention of Claim 4)
4. The fuel injection device for an internal combustion engine according to claim 1, wherein a fuel pressure that is switched to a low pressure side or a high pressure side by a control valve is introduced into the hydraulic valve, and the fuel pressure and the fuel pressure of the accumulator It is characterized by operating with a differential pressure between
When the control valve connects the hydraulic circuit to the high pressure side (set to the hydraulic pressure supply mode described in claim 2), high pressure is introduced into the hydraulic valve, so that the differential pressure from the fuel pressure of the accumulator is small, Or they become equal and the hydraulic valve closes. On the other hand, when the control valve connects the hydraulic circuit to the low pressure side (set to the hydraulic release mode described in claim 2), a low pressure is introduced into the hydraulic valve, so that the differential pressure from the fuel pressure of the accumulator is The hydraulic valve opens when it becomes larger.

(Invention of Claim 5)
5. The fuel injection device for an internal combustion engine according to claim 4, wherein the fuel pressure in the back pressure chamber is indirectly controlled via a hydraulic valve in contrast to the operation of the pressure intensifier that operates by controlling the fuel pressure in the control chamber directly by the control valve. The valve opening pressure of the hydraulic valve is set so as to cause a delay in the operation of the nozzle that is controlled and operated.
According to said structure, the timing which a hydraulic valve opens can be delayed. In other words, since the fuel pressure in the control chamber is directly controlled by the control valve and the fuel pressure in the back pressure chamber is indirectly controlled via the hydraulic valve, the operation of the pressure intensifier is increased by the delay in the opening timing of the hydraulic valve. In contrast, the operation of the nozzle (injection start timing) is delayed. In this case, since the injection is performed in a state where the pressure increase has progressed by the pressure intensifier, ultra-high pressure injection can be realized from the initial stage of the injection.

  The best mode for carrying out the present invention will be described in detail with reference to the following examples.

FIG. 1 is a hydraulic circuit diagram of the fuel injection device according to the first embodiment, and FIGS. 2 to 4 are hydraulic circuit diagrams including specific configurations of a control valve and a hydraulic valve used in the fuel injection device.
A fuel injection device 1 according to the present invention is employed in, for example, a common rail system of a diesel engine for a vehicle. As shown in FIG. 1, a pressure accumulator 2 that stores fuel in a predetermined pressure state, and a pressure accumulator 2 The pressure intensifier 3 for increasing the supplied fuel, the nozzle 4 for injecting the fuel supplied from the pressure accumulator 2 or the fuel increased by the pressure intensifier 3, the operation of the pressure intensifier 3 and the operation of the nozzle 4 are controlled. A control valve 5 and the like are provided. Note that the pressure intensifier 3, excluding the pressure accumulator 2, the nozzle 4, the control valve 5, and the like are configured as a fuel injection valve 6 as shown in FIG.

The pressure accumulator 2 is connected to the fuel injection valve 6 by a fuel pipe 7, and the fuel accumulated in the pressure accumulator 2 is supplied to the fuel injection valve 6 through the fuel pipe 7.
The intensifier 3 has a hydraulic piston 8 in which a large-diameter piston 8a and a small-diameter plunger 8b are provided concentrically. The hydraulic piston 8 has a large-diameter bore and a small-diameter bore formed in a body 9 (see FIG. 5). And is slidably accommodated. A drive chamber 10 is formed above the upper end surface of the large diameter piston 8a and a control chamber 11 is formed below the lower end surface of the large diameter piston 8a. . On the other hand, a pressurizing chamber 12 is formed below the lower end surface of the small diameter plunger 8b in the small diameter bore in which the small diameter plunger 8b is accommodated.

The drive chamber 10 is connected to the fuel pipe 7 through the fuel passage 13, and the fuel pressure of the pressure accumulator 2 is supplied through the fuel pipe 7 and the fuel passage 13. The fuel pressure in the drive chamber 10 acts on the upper end surface of the hydraulic piston 8 and urges the hydraulic piston 8 downward.
The control chamber 11 is connected to a switching port 16 (described later) of the control valve 5 via a fuel passage 15 having a throttle 14 (a part of the hydraulic circuit of the present invention). The pressure is controlled. In the control chamber 11, as shown in FIG. 5, a spring 17 that biases the hydraulic piston 8 upward is shown.

  The pressurizing chamber 12 is connected to the fuel pipe 7 through a fuel passage 19 having a check valve 18 and communicates with an oil sump 4 a (see FIG. 5) provided in the nozzle 4 through the fuel passage 20. . The check valve 18 allows the flow of fuel (fuel supplied from the pressure accumulator 2) toward the pressurizing chamber 12 through the fuel passage 19, and prevents the reverse flow (flow toward the pressure accumulator 2). As a result, the fuel pressure of the pressure accumulator 2 is supplied to the pressurizing chamber 12 and further supplied to the oil sump 4 a of the nozzle 4 via the fuel passage 20.

As shown in FIG. 5, the nozzle 4 includes a nozzle body 22 having a nozzle hole 21 formed at the tip, a needle 23 accommodated in the nozzle body 22, and a back pressure chamber at the upper portion of the needle 23 in the figure. The nozzle holder 25 and the like that form a member 24 are disposed below the body 9 and fixed to the body 9 by a retainer 26.
In the nozzle body 22, an annular fuel passage 27 is formed around the needle 23, and the oil reservoir 4 a is formed at the upstream end of the fuel passage 27. A conical seat surface (not shown) is formed between the fuel passage 27 and the injection hole 21.

The back pressure chamber 24 is connected to the switching port 16 of the control valve 5 through a reciprocating passage (described later) that forms part of the hydraulic circuit of the present invention, and the fuel pressure in the back pressure chamber 24 is controlled by the control valve 5. Be controlled.
When the fuel pressure of the accumulator 2 is supplied to the back pressure chamber 24, the needle 23 generates the fuel pressure of the accumulator 2 and the urging force of the spring 28 (see FIG. 5) disposed in the back pressure chamber 24. The seat line (not shown) provided at the tip of the needle 23 is seated on the seat surface and pressed between the fuel passage 27 and the injection hole 21. Cut off. On the other hand, when the fuel pressure in the back pressure chamber 24 is released via the control valve 5, the needle 23 lifts and opens between the fuel passage 27 and the injection hole 21, so that the fuel supplied to the oil sump 4 a is increased. Is injected from the injection hole 21 through the fuel passage 27.

  As shown in FIG. 1, the reciprocating passage is formed by two fuel passages 29 and 30 that connect the switching port 16 of the control valve 5 and the back pressure chamber 24 of the nozzle 4 in parallel. One fuel passage 29 is provided with a check valve 31 that allows the flow of fuel from the control valve 5 toward the back pressure chamber 24 and prevents the reverse flow, and the other fuel passage 30 has a throttle 32 and a hydraulic pressure. A valve 33 (described below) is provided. The two fuel passages 29 and 30 can be provided completely independently from one end connected to the switching port 16 of the control valve 5 to the other end connected to the back pressure chamber 24. As shown in FIG. 1, one end side and the other end side of both passages 29 and 30 can be provided in common.

As shown in FIG. 2, the hydraulic valve 33 includes a valve chamber 33a, a valve body 33b accommodated in the valve chamber 33a, a spring 33c that urges the valve body 33b, and the like.
The valve chamber 33 a is provided with an inlet port 34 that communicates with the back pressure chamber 24 of the nozzle 4 and an outlet port 35 that communicates with the switching port 16 of the control valve 5.
The valve body 33b has a valve closing mode (a position shown in FIGS. 1, 2, 3, and 5) for blocking between the inlet side port 34 and the outlet side port 35, and the inlet side port 34 and the outlet side port 35. Can be switched to the valve opening mode (position shown in FIG. 4).
The spring 33c is accommodated in a working chamber 33d that is recessed below the valve chamber 33a and urges the valve body 33b in the valve closing direction (upward in FIG. 2).

  The hydraulic pressure of the accumulator 2 is always introduced into the hydraulic valve 33 via the fuel passage 36 communicating with the accumulator 2, and the fuel pressure urges the valve body 33b in the valve opening direction (downward in FIG. 2). ing. On the other hand, fuel pressure corresponding to the operation mode of the control valve 5 is introduced into the working chamber 33d through a pressure introduction path 37 (see FIG. 1) connected to the switching port 16 of the control valve 5. That is, when the control valve 5 is set to the hydraulic pressure supply mode, the fuel pressure of the pressure accumulator 2 is introduced into the working chamber 33d via the pressure introduction path 37, and the force for urging the valve body 33b in the valve opening direction; Since the difference from the force that urges the valve body 33b in the valve closing direction is small or equal, the valve body 33b is urged in the valve closing direction by the reaction force of the spring 33c, and the valve closing mode is set.

In addition, when the control valve 5 is set to the hydraulic release mode, the differential pressure applied to the valve body 33b increases due to the working chamber 33d leading to the low pressure side (the force for urging the valve body 33b in the valve opening direction). Therefore, the valve element 33b is urged in the valve opening direction against the reaction force of the spring 33c, and the valve opening mode is set. That is, the hydraulic valve 33 is configured as a two-position two-way valve that opens and closes the fuel passage 30 according to the operation mode.
However, in the first embodiment, when the control valve 5 is switched from the hydraulic pressure supply mode to the hydraulic pressure release mode, the pressure introduction passage 37 is throttled so that the timing at which the hydraulic valve 33 is switched from the valve closing mode to the valve opening mode is delayed. 38 (see FIG. 1) is provided, and a delay time is set by the diaphragm 38.

  As shown in FIG. 5, the control valve 5 has a valve chamber 5a formed in the body 39, a valve body 5b accommodated in the valve chamber 5a, and a two-position actuator 40 for driving the valve body 5b. The retainer 41 is disposed on the body 9 and is fixed to the body 9. As shown in FIG. 2, the valve chamber 5 a has an input port 43 to which the fuel pressure of the accumulator 2 is supplied via a fuel passage 42 connected to the fuel pipe 7, and a fuel tank 45 via a drain passage 44. A low pressure port 46 communicating with the first pressure port, a first switching port connected to the back pressure chamber 24 of the nozzle 4 via the reciprocating passage (fuel passages 29, 30), and a control chamber of the pressure booster 3 via the fuel passage 15. 11 is connected to the second switching port. Hereinafter, the first switching port and the second switching port will be described as the switching port 16 described above.

  The valve body 5b shuts off the low pressure port 46 and the switching port 16 and communicates between the input port 43 and the switching port 16 (position shown in FIGS. 1, 2 and 5). The oil pressure release mode (the position shown in FIGS. 3 and 4) in which the input port 43 and the switching port 16 are blocked and the low pressure port 46 and the switching port 16 communicate with each other can be switched. That is, the control valve 5 is configured as a two-position three-way valve that switches the fuel flow direction according to the operation mode.

  As shown in FIG. 2, the actuator 40 includes a disk-shaped armature 47 connected to the valve body 5b, an electromagnetic coil 49 that is energized and controlled by an electronic control device (hereinafter referred to as ECU 48) mounted on the vehicle, The armature 47 includes a return spring 50 that urges the armature 47 downward in the figure. When a magnetic force is generated by energizing the electromagnetic coil 49, the actuator 40 receives the magnetic force to attract the armature 47, and moves upward in the figure against the reaction force of the return spring 50 to generate a driving force. . When the energization of the electromagnetic coil 49 is stopped, the armature 47 is pushed back by the reaction force of the return spring 50 due to the disappearance of the magnetic force, and returns to the initial state shown in FIG. In the hydraulic circuit diagram shown in FIG. 2, the operating direction of the armature 47 is shown in the opposite direction to FIG. That is, in FIG. 5, when the electromagnetic coil 49 is energized, the armature 47 moves downward in the figure due to the magnetic force, but in FIG. 2, the armature 47 is shown to move upward in the figure.

Next, the operation of the fuel injection device 1 will be described based on the time charts shown in FIGS. 2 to 4 and 6. Note that (1), (2), and (3) in FIG. 6 correspond to the states shown in FIGS. 2, 3, and 4, respectively.
When the electromagnetic coil 49 of the actuator 40 is in the OFF state, the control valve 5 is set to the hydraulic pressure supply mode as shown in FIG. In this hydraulic pressure supply mode, the switching port 16 and the low pressure port 46 are disconnected, and the input port 43 and the switching port 16 communicate with each other, so that the fuel pressure of the pressure accumulator 2 is supplied to the switching port 16. The hydraulic valve 33 is in the valve closing mode because the fuel pressure of the accumulator 2 is introduced into the working chamber 33d through the pressure introduction path 37.

  As a result, the fuel pressure of the pressure accumulator 2 is supplied to the control chamber 11 of the pressure booster 3 via the fuel passage 15, and the back pressure chamber 24 of the nozzle 4 via one fuel passage 29 having the check valve 31. Also supplied. At this time, in the pressure booster 3, the fuel pressure of the pressure accumulator 2 is also supplied to the drive chamber 10 and the pressurizing chamber 12, so that the fuel pressure acting on the upper and lower end surfaces of the hydraulic piston 8 is balanced. As a result, the hydraulic piston 8 is urged by the spring 17 (see FIG. 5) and moves upward in the figure, and the pressurizing chamber 12 is filled with fuel as the volume of the pressurizing chamber 12 increases. In this state, the back pressure chamber 24 of the nozzle 4 has the same fuel pressure as that of the pressure accumulator 2, so that the needle 23 does not lift and the fuel passage 27 in the nozzle 4 and the injection hole 21 are blocked. As a result, fuel is not injected.

  Next, when a drive signal is output from the ECU 48 to the actuator 40 and the electromagnetic coil 49 is energized, the control valve 5 is switched from the hydraulic pressure supply mode to the hydraulic pressure release mode as shown in FIG. As a result, the control chamber 11 of the intensifier 3 communicates with the drain passage 44, so that the fuel pressure in the control chamber 11 is released to the low pressure side. As a result, the pressure balance between the upper side and the lower side acting on the hydraulic piston 8 is lost, and the hydraulic piston 8 is pressed by the fuel pressure in the drive chamber 10 and pushed downward in the figure.

  As the hydraulic piston 8 increases in pressure, the fuel pressure in the pressurizing chamber 12 starts to increase, and finally the pressure is increased according to the cross-sectional area ratio between the large diameter piston 8a and the small diameter plunger 8b. For example, when the fuel pressure of the pressure accumulator 2 is 50 MPa and the cross-sectional area ratio between the large diameter piston 8a and the small diameter plunger 8b is set to 4: 1, the fuel pressure in the pressurizing chamber 12 is 4 × 50 = 200 MPa. . Here, even if the control valve 5 is switched to the hydraulic release mode, the hydraulic valve 33 remains in the closed mode until the pressure in the control chamber 11 leading to the switching port 16 of the control valve 5 drops to a predetermined pressure. Yes. Therefore, the fuel does not flow out from the back pressure chamber 24 of the nozzle 4 and is not injected from the nozzle 4 until the hydraulic valve 33 is switched to the valve opening mode.

  After that, when the fuel pressure in the control chamber 11 is further released and falls to a predetermined pressure, the hydraulic valve 33 is switched from the valve closing mode to the valve opening mode after a delay time set by the throttle 38 of the pressure introduction path 37. (See FIG. 4). As a result, the back pressure chamber 24 of the nozzle 4 communicates with the drain passage 44 and the fuel pressure in the back pressure chamber 24 is released to the low pressure side, so that the needle 23 is lifted and the fuel supplied to the oil sump 4a. (Ultra-high pressure fuel increased in pressure by the pressure intensifier 3) is injected from the injection hole 21.

  Thereafter, when energization to the electromagnetic coil 49 is stopped at a predetermined timing (for example, when a predetermined injection amount is reached), the control valve 5 is switched from the hydraulic pressure release mode to the hydraulic pressure supply mode. Is supplied to the back pressure chamber 24 of the nozzle 4 and the control chamber 11 of the pressure intensifier 3. Thereby, in the nozzle 4, the fuel pressure in the back pressure chamber 24 rises and the needle 23 is pushed back, thereby terminating the injection. In the pressure booster 3, the hydraulic piston 8 immediately stops the pressure increasing operation due to the pressure increase in the control chamber 11, and starts the return stroke.

(Effect of Example 1)
In the fuel injection device 1 described in the first embodiment, the switching port 16 of the control valve 5 and the back pressure chamber 24 of the nozzle 4 are connected in parallel by two fuel passages 29 and 30. Different passages can be used for releasing the pressure of 24 and for applying pressure. That is, when pressure is applied to the back pressure chamber 24, the fuel pressure of the accumulator 2 can be supplied to the back pressure chamber 24 through one fuel passage 29 provided with the check valve 31. When the pressure 24 is released, the pressure can be released from the back pressure chamber 24 to the low pressure side through the other fuel passage 30 provided with the hydraulic valve 33.

  According to the above configuration, the valve opening speed of the needle 23 at the start of injection can be changed by the pressure release speed of the back pressure chamber 24. Alternatively, the valve closing speed of the needle 23 at the end of injection can be changed by the pressurization speed of the back pressure chamber 24. Furthermore, since the throttle 38 is provided in the pressure introduction path 37 leading to the working chamber 33d of the hydraulic valve 33, the timing at which the hydraulic valve 33 is switched from the valve closing mode to the valve opening mode can be delayed. As a result, as shown by the broken line in FIG. 6, the operation of the needle 23 (back pressure release timing) can be delayed.

  As described above, the injection rate pattern can be optimized by changing the valve opening speed of the needle 23, the valve closing speed of the needle 23, and the back pressure release timing of the nozzle 4. In particular, the initial stage of injection can be made high, and the pressure can be changed by the delay time of the hydraulic valve 33. As is well known, the optimization of the injection rate pattern is effective in improving the output of the internal combustion engine. In addition, by changing the valve closing speed of the needle 23, it is possible to make settings such that the end of injection can be made sharper without affecting other characteristics. Furthermore, since the back pressure of the nozzle 4 can be increased through the fuel passage 29 regardless of the delay of the hydraulic valve 33 at the end of injection, a reliable and sharp valve closing is possible.

Further, in the fuel injection device 1 according to the first embodiment, since no fuel dripping occurs except for a slight switching leak that occurs when the operation mode of the control valve 5 is switched, energy loss can be suppressed and fuel consumption reduction of the internal combustion engine can be prevented. it can.
Further, the switching port 16 of the control valve 5 and the back pressure chamber 24 of the nozzle 4 are connected in parallel by two fuel passages 29 and 30, and when the injection is completed, the fuel passage 29 is independent of the delay of the hydraulic valve 33. Since the back pressure of the nozzle 4 can be raised through the end, the end of the pressure increasing stroke can be completed simultaneously with the end of the injection. For this reason, it is not necessary to operate the intensifier 3 wastefully, and waste of driving energy can be eliminated.

  In the fuel injection device 1 described in the first embodiment, an ultrahigh pressure injection without energy loss can be realized with a simple configuration using only one control valve 5 driven by a two-position actuator 40, and a low pressure, an ultrahigh pressure can be realized. Various injection patterns such as a delta type and a rectangular type can be realized by starting high-pressure injection.

(Modification)
In the first embodiment, a throttle 38 is provided in the pressure introduction path 37 to delay the operation of the nozzle 4 (back pressure release timing) by delaying the timing at which the hydraulic valve 33 switches from the valve closing mode to the valve opening mode. However, instead of providing the throttle 38, it is possible to adjust the delay time by appropriately setting the operating pressure of the hydraulic valve 33. For example, the delay time can be set by the load of a spring 33c that biases the valve element 33b of the hydraulic valve 33. Alternatively, the timing at which the hydraulic valve 33 operates can be delayed by the cooperation of the effect of the throttle 38 provided in the pressure introduction path 37 and the operating pressure of the hydraulic valve 33.

In the first embodiment, the throttle 32 is provided in the other fuel passage 30. However, the throttle 32 may be provided in one fuel passage 29, or the throttle 32 may be provided in both the fuel passages 29 and 30. May be.
Furthermore, the fuel flow directions regulated by the check valve 31 and the hydraulic valve 33 described in the first embodiment can be set in opposite directions. In other words, the check valve 31 is configured to allow the flow of fuel from the back pressure chamber 24 of the nozzle 4 toward the control valve 5 and prevent the reverse flow, and the hydraulic valve 33 is configured so that the control valve 5 is in the hydraulic supply mode. It is also possible to configure such that the valve opening mode is set when the control valve 5 is set to, and the valve closing mode is set when the control valve 5 is set to the hydraulic pressure release mode.

FIG. 7 is a hydraulic circuit diagram of the fuel injection device 1 according to the second embodiment.
The fuel injection device 1 shown in the second embodiment is different from the first embodiment in that a check valve 51 is provided instead of the hydraulic valve 33 shown in the first embodiment.
One fuel passage 29 is provided with a check valve 31 that permits the flow of fuel from the control valve 5 toward the back pressure chamber 24 of the nozzle 4 and prevents the reverse flow, as in the first embodiment. The passage 30 is provided with a check valve 51 that allows fuel flow from the back pressure chamber 24 of the nozzle 4 toward the control valve 5 and prevents backflow thereof.

Also in this configuration, as in the first embodiment, the valve opening speed of the needle 23 at the start of injection can be changed by the pressure release speed of the back pressure chamber 24, and the pressure at the end of injection can be changed by the pressurization speed of the back pressure chamber 24. Since the valve closing speed of the needle 23 can be changed, the injection rate pattern can be optimized according to the operating state of the internal combustion engine.
In addition, when the control valve 5 is switched from the hydraulic pressure supply mode to the hydraulic pressure release mode, the valve opening pressure of the check valve 51 is set so that the timing of opening the check valve 51 is delayed. It is also possible to delay the operation (back pressure release timing).
In the fuel injection device 1 shown in the second embodiment, a check valve 51 is provided instead of the hydraulic valve 33 in the first embodiment, so that the hydraulic circuit can be configured more simply than in the first embodiment, and an inexpensive system can be provided .

[Reference example]
FIG. 8 is a hydraulic circuit diagram of the fuel injection device 1 according to the reference example .
In this reference example , as shown in FIG. 8, one of the two fuel passages 29, 30 connecting the switching port 16 of the control valve 5 and the back pressure chamber 24 of the nozzle 4 is one fuel passage 29 ( Alternatively, a check valve 31 is provided only in the other fuel passage 30).
According to the above configuration, when the fuel pressure of the accumulator 2 is supplied to the back pressure chamber 24 of the nozzle 4, that is, when the fuel flows from the control valve 5 toward the back pressure chamber 24, When the fuel pressure is released to the low pressure side, that is, when the fuel flows from the back pressure chamber 24 toward the control valve 5, it is possible to make a difference between the flow rates of the two. As a result, when the fuel pressure is supplied to the back pressure chamber 24 and when the fuel pressure in the back pressure chamber 24 is released, the valve closing speed of the needle 23 as the pressure in the back pressure chamber 24 increases, The valve opening speed of the needle 23 associated with the pressure release of the pressure chamber 24 can be set independently, and the injection rate pattern can be changed.
Further, in the configuration of this reference example , the fuel injection valve 6 (see FIG. 5) can be downsized, and a cheaper system can be realized.

1 is a hydraulic circuit diagram of a fuel injection device (Example 1). 1 is a hydraulic circuit diagram including specific configurations of a control valve and a hydraulic valve used in a fuel injection device (Example 1). 1 is a hydraulic circuit diagram of a fuel injection device (Example 1). 1 is a hydraulic circuit diagram of a fuel injection device (Example 1). 1 is an overall cross-sectional view showing a structure of a fuel injection valve (Example 1). It is a time chart which concerns on the action | operation of a fuel-injection apparatus (Example 1). (Example 2) which is the hydraulic circuit figure of a fuel-injection apparatus. It is a hydraulic circuit figure of a fuel injection device ( reference example ). 1 is a hydraulic circuit diagram of a fuel injection device (prior art).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel injection device for internal combustion engines 2 Pressure accumulator 3 Pressure booster 4 Nozzle 5 Control valve 5b Valve body (control valve)
8 Hydraulic piston 11 Control chamber of intensifier 15 Fuel passage (hydraulic circuit)
16 switching port (control valve)
23 Needle 24 Nozzle back pressure chamber 29 One fuel passage (hydraulic circuit)
30 Other fuel passage (hydraulic circuit)
31 Check valve 32 Throttle 33 Hydraulic valve 33b Valve body (hydraulic valve)
40 Two-position actuator 43 Input port (control valve)
45 Fuel tank 46 Low pressure port (control valve)

Claims (5)

a) a pressure accumulator for storing fuel in a predetermined pressure state;
b) It has a control chamber in which the oil pressure increases or decreases due to the inflow or outflow of fuel, and a hydraulic piston that moves according to the increase or decrease of the oil pressure in the control chamber, and is supplied from the accumulator by the pressure increasing operation of this hydraulic piston. A pressure intensifier for increasing the pressure of the fuel,
c) It has a back pressure chamber whose hydraulic pressure increases or decreases due to the inflow or outflow of fuel, and a needle that moves according to the increase or decrease of the hydraulic pressure in the back pressure chamber, and is supplied by the fuel supplied from the pressure accumulator or the pressure intensifier A nozzle that injects the pressurized fuel by the valve opening operation of the needle;
d) a fuel passage for supplying fuel pressure of the accumulator to the control chamber and the back pressure chamber, and a fuel passage for opening the fuel pressure of the control chamber and the back pressure chamber to the low pressure side. A hydraulic circuit;
e) A valve body driven by a single two-position actuator is built in, and by this valve body, either one of the high pressure side leading to the accumulator and the low pressure side leading to the fuel tank is selectively switched to switch the hydraulic circuit A fuel injection device for an internal combustion engine provided with a control valve for controlling the operation of the pressure intensifier and the nozzle by connecting to
The hydraulic circuit is provided with two fuel passages connected in parallel between the control valve and the back pressure chamber of the nozzle. One fuel passage is connected to the back pressure chamber from the control valve. A check valve is provided that allows the flow of fuel to flow and prevents its backflow, and the other fuel passage allows a flow of fuel from the back pressure chamber to the control valve and reverses that flow. A fuel injection device for an internal combustion engine, wherein a stop valve or a hydraulic valve is provided. The fuel injection device for an internal combustion engine according to claim 1,
The control valve is provided with a switching port connected to the hydraulic circuit, an input port leading to the pressure accumulator, and a low pressure port connected to a low pressure side drain passage,
The valve body shuts off the low-pressure port and the switching port and communicates between the input port and the switching port; and the valve body includes the input port and the switching port. A fuel injection device for an internal combustion engine, which is a two-position three-way valve that selectively switches between a low pressure port and a hydraulic release mode that communicates between the low pressure port and the switching port. The fuel injection device for an internal combustion engine according to claim 1 or 2,
For the internal combustion engine, the hydraulic valve is a two-position two-way valve that can be switched to one of a valve closing mode for closing the other fuel passage and a valve opening mode for opening the other fuel passage. Fuel injection device. The fuel injection device for an internal combustion engine according to any one of claims 1 to 3,
A fuel for an internal combustion engine, wherein the hydraulic valve is operated with a differential pressure between the fuel pressure switched to the low pressure side or the high pressure side by the control valve and the fuel pressure of the pressure accumulator. Injection device. The fuel injection device for an internal combustion engine according to claim 4,
The nozzle that operates by controlling the fuel pressure in the back pressure chamber indirectly through the hydraulic valve in contrast to the operation of the pressure intensifier that operates by controlling the fuel pressure in the control chamber directly by the control valve. A fuel injection device for an internal combustion engine, wherein the valve opening pressure of the hydraulic valve is set so that a delay occurs in the operation of the engine .

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