JP3758312B2 - Engine fuel injector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel injection device including a fuel injection device for an engine that operates a needle valve by changing a fuel pressure before and after the needle valve via an electromagnetic strain actuator.
[0002]
[Prior art]
2. Description of the Related Art Some fuel injection valves and the like provided in automobile engines include a piezo actuator (piezoelectric element) that expands according to an applied voltage, and a needle valve (valve element) is opened via the piezo actuator. By driving the needle valve with a piezo actuator, the high-speed response of the fuel injection valve is enhanced, and the ratio of the maximum injection amount to the minimum injection amount (dynamic range) can be expanded to cope with higher engine output. In addition, since a small amount of fuel can be stably injected, the fuel consumption of the engine can be reduced.
[0003]
As this type of fuel injection valve, there is known a valve in which a needle valve is opened based on a differential pressure across it. A fuel pressure chamber and a differential pressure chamber are defined before and after the needle valve. Fuel is introduced into the fuel pressure chamber at a predetermined pressure, and the differential pressure chamber communicates with the fuel pressure chamber through an orifice. A piezo actuator is provided in the differential pressure chamber behind the needle valve, and the opening and closing operation of the needle valve is controlled by the expansion and contraction of the piezo actuator. That is, the pressure in the fuel pressure chamber and the differential pressure chamber before and after the needle valve is equalized through the orifice in a state where the piezoelectric actuator is extended by applying a voltage. At this time, the needle valve is held closed by the tension of the return spring. If both terminals of the piezo actuator are short-circuited from this state and the piezo actuator is instantaneously contracted, the volume of the differential pressure chamber behind the needle valve increases. At this time, since the differential pressure chamber communicates with the fuel pressure chamber in front of the needle valve via the orifice, the internal pressure of the differential pressure chamber temporarily decreases and a pressure difference in the valve opening direction is generated before and after the needle valve. To do. As a result, the needle valve is opened against the return spring, and the nozzle is opened to inject fuel. (For a known example of this type of fuel injection valve, see, for example, JP-A-6-280711.)
[0006]
[Problems to be solved by the invention]
By the way, in the conventional fuel injection apparatus using such a piezo actuator, the piezo actuator is driven so as to constantly change the contraction amount of the piezo actuator, so that the fuel pressure is low at the time of engine start-up. Sometimes, a predetermined fuel injection amount cannot be injected. That is, when the fuel pressure is low, it is necessary to ensure a predetermined fuel injection amount by extending the needle valve opening period, but the fuel in the fuel pressure chamber passes through the orifice while the fuel injection valve is open. Therefore, if the needle valve is opened for a long time, the drive differential pressure generated before and after the needle valve decreases, and eventually the holding required to open the needle valve against the spring is maintained. Power cannot be obtained.
[0007]
The present invention has been made in view of the above-described problems, and an object of the present invention is to ensure a sufficient fuel injection amount at the time of engine start or the like in an engine fuel injection device.
[0008]
[Means for Solving the Problems]
The engine fuel injection device according to claim 1 comprises: Stretches when a voltage or magnetic field is applied, Applied voltage or magnetic field Contracted by being blocked Electromagnetic strain actuators and electromagnetic strain actuators The volume expands and the pressure decreases with contraction, and the volume decreases and the pressure increases with expansion of the electromagnetic strain actuator. A differential pressure chamber, a fuel pressure chamber through which pressurized fuel is guided, a throttle passage communicating the fuel pressure chamber and the differential pressure chamber, a needle valve that is displaced according to a pressure difference between the fuel pressure chamber and the differential pressure chamber, and a needle valve In a fuel injection device for an engine comprising a spring that biases the valve in a valve closing direction and an injection hole that is opened and closed by a needle valve, Yield The pressure difference generated between the differential pressure chamber and the fuel pressure chamber is changed by changing the amount of contraction as the needle valve opens. More than the holding force required to open the valve Control means to maintain was provided.
[0009]
The engine fuel injection device according to claim 2 is the control means according to claim 1, wherein Yield The contraction amount is changed stepwise as the valve opening time of the needle valve elapses.
[0010]
According to a third aspect of the present invention, there is provided a fuel injection device for an engine according to the first aspect, wherein the electrostrictive actuator is a Yield The amount of contraction is continuously changed as the needle valve opening time elapses.
[0011]
According to a fourth aspect of the present invention, there is provided a fuel injection device for an engine according to any one of the first to third aspects, wherein the determination means determines an operating condition in which a required valve opening period of the needle valve is a predetermined value or more. The control means includes an electromagnetic strain actuator under operating conditions where the required valve opening period of the needle valve is a predetermined value or more. Yield While the amount of contraction is changed as the needle valve opening time elapses, the electromagnetic strain actuator is operated under the operating conditions where the required valve opening period is shorter than the predetermined value. Yield The reduction amount is uniformly changed.
[0012]
According to a fifth aspect of the present invention, there is provided a fuel injection device for an engine according to any one of the first to fourth aspects, further comprising fuel viscosity detecting means for detecting the viscosity of the fuel, wherein the control means is a fuel viscosity. Of the electrostrictive actuator as the Yield The rate of change of shrinkage big It was set as the structure to do.
[0013]
According to a sixth aspect of the present invention, there is provided a fuel injection device for an engine according to the first aspect of the invention, further comprising pressure detecting means for detecting the pressure in the differential pressure chamber, wherein the control means is an electromagnetic strain actuator. Yield Reduce pressure to differential pressure chamber And fuel pressure chamber Pressure difference But Below the specified value As it falls increase It was set as the structure made to do.
[0014]
Operation and effect of the invention
In the first aspect of the invention, when the electromagnetic strain actuator is extended, the pressure in the fuel pressure chamber and the differential pressure chamber generated before and after the needle valve is equalized by the throttle passage. At this time, the needle valve is held closed by the elastic restoring force of the spring.
[0015]
Electrostrictive actuator Yield As it shrinks, the volume of the differential pressure chamber increases and its pressure decreases. Since the pressure drop is delayed and transmitted to the fuel pressure chamber by the throttle passage, a pressure difference is temporarily generated between the pressure difference chamber and the fuel pressure chamber. Due to this pressure difference, the needle valve opens the nozzle hole against the spring, and fuel is injected from the nozzle hole.
[0016]
By the way, the electromagnetic strain actuator Yield If driving is performed so that the amount of contraction changes uniformly, if the required valve opening period of the needle valve becomes longer when the fuel pressure is low, such as when the engine is started, the drive differential pressure generated before and after the needle valve decreases, and eventually the needle valve is The holding force necessary for opening the valve against the spring cannot be obtained, and there is a possibility that a predetermined fuel injection amount cannot be injected.
[0017]
The present invention copes with this by using an electromagnetic strain actuator. Yield By controlling the amount of contraction stepwise or continuously as the needle valve opening time elapses, the pressure difference generated between the differential pressure chamber and the fuel pressure chamber is reduced. More than the holding force required to open the valve The time for the needle valve to open against the spring is maintained and the fuel injection amount is increased. As a result, the required fuel injection amount can be ensured even when the fuel pressure is low, such as when the engine is started.
[0018]
In the invention of claim 2, the electromagnetic strain actuator Yield The needle valve opens against the spring when the fuel pressure is low, for example, when the engine is started, by controlling the amount of contraction stepwise as the valve opening time elapses. The required fuel injection amount can be secured by extending the time to perform.
[0019]
In the invention of claim 3, the electromagnetic strain actuator Yield The valve opening period of the needle valve can be effectively extended by controlling the amount of contraction to change continuously as the valve opening time elapses.
[0020]
In the invention according to claim 4, the electromagnetic strain actuator is operated under an operating condition in which the required valve opening period of the needle valve is a predetermined value or more. Yield By controlling the amount of contraction stepwise or continuously as the needle valve opening time elapses, the needle valve resists the spring when the fuel pressure is low, for example, when the engine is started. The required time for fuel injection can be secured by extending the valve opening time. As a result, the required fuel injection amount can be ensured even when the fuel pressure is low, such as when the engine is started.
[0021]
On the other hand, when the required opening period of the needle valve is shorter than the predetermined value, Yield By performing control to uniformly change the amount of contraction, the maximum value of the pressure difference generated between the differential pressure chamber and the fuel pressure chamber is increased, and the responsiveness that the needle valve opens against the spring can be enhanced. As a result, the setting range of the fuel injection amount can be expanded to cope with high engine output.
[0022]
In the invention according to claim 5, in response to the rate of change of the fuel pressure in the differential pressure chamber increasing as the fuel viscosity decreases, Yield The rate of change of shrinkage big With this configuration, it is possible to effectively extend the valve opening period of the needle valve.
[0023]
In the invention of claim 6, the electromagnetic strain actuator Yield Reduce pressure to differential pressure chamber And fuel pressure chamber Pressure difference But Below the specified value As it falls increase With this configuration, it is possible to effectively extend the valve opening period of the needle valve.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the present invention is applied to a fuel injection valve provided in an in-cylinder spark ignition engine will be described with reference to the accompanying drawings.
[0025]
As shown in FIG. 1, the fuel injection valve 7 causes the nozzle body 1 provided at the tip thereof to face a combustion chamber of an engine (not shown). The nozzle body 1 faces the combustion chamber from the ceiling wall of the combustion chamber of the engine, and fuel spray is ejected from a nozzle 1b opened at the tip of the nozzle body 1 toward the crown of the piston.
[0026]
A needle valve 2 is slidably housed inside the nozzle body 1. A fuel pressure chamber 3 is defined around the needle valve 2 inside the nozzle body 1. A nozzle hole 1 b opens at the tip of the nozzle body 1, and the nozzle hole 1 b is opened and closed by a needle valve 2.
[0027]
As shown in FIG. 2, the fuel stored in the fuel tank 59 is sucked up via the first fuel pump 58 driven by the electric motor 54 and is pumped to the second fuel pump 57. Usually, the discharge pressure of the second fuel pump 57 is set higher than the discharge pressure of the first fuel pump 58.
[0028]
The second fuel pump 57 driven by the engine 50 sends further pressurized fuel to the pressure accumulating chamber 56, and pumps the fuel from the pressure accumulating chamber 56 to the fuel injection valve 7 of each cylinder.
[0029]
The second fuel pump 57 driven by the engine 50 sends further pressurized fuel to the pressure accumulating chamber 56, and pumps the fuel from the pressure accumulating chamber 56 to the fuel injection valve 7 of each cylinder. A pressure regulator 55 is provided in the fuel return passage 52, and the fuel pressure guided to the fuel injection valve 7 is kept below a predetermined value by returning the excess fuel in the pressure accumulating chamber 56 to the fuel tank 59. Yes.
[0030]
The fuel pumped from the fuel pump 58 is introduced into the fuel pressure chamber 3 from the fuel inlet passage 6 and is injected from the nozzle 1 b as the needle valve 2 is lifted.
[0031]
The needle valve 2 has a piston portion 2c on the proximal end side. A differential pressure chamber 8 is defined between the nozzle body 1 and the casing 9 and the piston portion 2c. The fuel pressure chamber 3 and the differential pressure chamber 8 communicate with each other via a throttle passage (gap) 5 formed on the outer periphery of the piston portion 2c.
[0032]
A coil spring 4 that urges the needle valve 2 in the valve closing direction is provided. The coil spring 4 is interposed between the piston portion 2 c of the needle valve 2 and the casing 9 in a compressed state, and is disposed coaxially with the needle valve 2.
[0033]
A shim 17 is interposed between the proximal end of the needle valve 2 and the casing 9. The maximum lift amount of the needle valve 2 is determined by the shim 17.
[0034]
Inside the casing 9, a piston 11 defining a differential pressure chamber 8 is slidably interposed. An O-ring 12 is interposed on the outer periphery of the piston 11. When the O-ring 12 is in sliding contact with the cylindrical inner wall surface of the casing 9, the differential pressure chamber 8 is sealed.
[0035]
A piezo actuator 10 that opens and closes the needle valve 2 via a piston 11 is provided. In the piezo actuator 10, a plurality of disk-shaped piezo elements are stacked with an internal electrode that is also disk-shaped in between.
[0036]
An end plate 14 is coupled to the fixed end of the piezo actuator 10. A plate 15 is screwed onto the open end of the casing 9. A disc spring 16 is interposed between the plate 15 and the piston 14.
[0037]
The piezo actuator 10 extends when a voltage is applied to each piezo element from the drive amplifier 18. At this time, the pressure in the differential pressure chamber 8 is increased and the needle valve 2 is closed. The piezoelectric actuator 10 contracts when the voltage applied to each piezoelectric element is cut off and short-circuited. At this time, the pressure in the differential pressure chamber 8 decreases with respect to the fuel pressure chamber 3, and the needle valve 2 moves in the valve opening direction against the coil spring 4.
[0038]
Instead of the piezo actuator 10, a magnetostrictive actuator composed of a giant magnetostrictive element that expands and contracts according to the strength of the applied magnetic field may be used. Here, the piezo actuator and the magnetostrictive actuator are collectively referred to as an electromagnetic strain actuator.
[0039]
Further, in the present embodiment, the fuel is injected by the contracting operation of the piezo actuator 10, but the fuel may be injected by the extending operation of the piezo actuator 10.
[0040]
The controller 19 generates a pulse signal corresponding to the calculated fuel injection amount, and a voltage corresponding to the pulse signal is applied to the piezo actuator 10 via the drive amplifier 18.
[0041]
The controller 19 inputs various signals for detecting engine operating conditions such as the rotational speed of the engine 50 and the intake air amount of the engine 50, and calculates the fuel injection amount in accordance with these engine operating conditions.
[0042]
FIG. 1 shows a state before the engine is started, and each piezo element of the piezo actuator 10 is expanded by applying a voltage, and the pressure in the fuel pressure chamber 3 and the differential pressure chamber 8 generated before and after the piston portion 2c is reduced. It is equalized via the passage 5. At this time, the needle valve 2 is seated on the seat portion of the nozzle body 1 by the elastic restoring force of the coil spring 4. In this state, the first fuel pump 58 is driven by the electric motor 54 to increase the pressure in the fuel pressure chamber 3 and the differential pressure chamber 8.
[0043]
Even when the engine is stopped, the elastic restoring force of the coil spring 4 is seated on the seat portion of the nozzle body 1 of the needle valve 2 to prevent fuel leakage.
[0044]
When the fuel injection valve 7 is opened at the time of starting the engine and after starting, each piezo element contracts by cutting off and short-circuiting the voltage applied in synchronization with the engine rotation. As the piston 11 moves as each piezo element contracts, the volume of the differential pressure chamber 8 increases and its pressure decreases. Since the pressure drop in the fuel pressure chamber 3 is transmitted through the throttle passage 5 with a delay, a pressure difference is immediately generated between the differential pressure chamber 8 and the fuel pressure chamber 3. Due to this pressure difference, the needle valve 2 opens the nozzle hole 1b against the coil spring 4, and high-pressure fuel guided to the fuel pressure chamber 3 is injected into the combustion chamber of the engine 50 through the nozzle hole 1b.
[0045]
When the fuel injection valve 7 is closed, each piezo element expands when a voltage is applied in synchronization with the engine rotation, and when the piston 11 moves, the pressure in the differential pressure chamber 8 immediately recovers. The needle valve 2 is moved by the pressure difference between the chamber 8 and the fuel pressure chamber 3 and the urging force of the coil spring 4 and is seated on the seat portion of the nozzle body 1. When the needle valve 2 is seated on the seat portion, the nozzle hole 1b is closed, and fuel injection is stopped.
[0046]
Since the displacement direction of the piezo actuator 10 and the displacement direction of the needle valve 2 coincide with each other in the fuel injection valve 7, the piezo actuator 10 and the needle valve 2 are arranged in series, thereby simplifying the structure.
[0047]
Incidentally, when the engine is started, the discharge pressure of the first fuel pump 58 driven by the electric motor 54 increases, but the discharge pressure of the second fuel pump 57 driven by the engine 50 does not increase, and the fuel injection valve 7 Since low pressure fuel is supplied, it is necessary to increase the injection pulse width (valve opening period) of the fuel injection valve 7 to ensure a predetermined fuel injection amount.
[0048]
However, since the fuel in the fuel pressure chamber 3 flows into the differential pressure chamber 8 side through the throttle passage 2c while the fuel injection valve 7 is open, if the injection pulse width of the fuel injection valve 7 becomes longer, the needle valve The driving differential pressure generated before and after 2 decreases, and the holding force necessary to open the needle valve 2 against the coil spring 4 is not obtained.
[0049]
Conventionally, since the drive voltage supplied to the piezo actuator 10 is reduced from 400 V to 0 V as indicated by the broken line in FIG. 4, the drive differential pressure of the needle valve 2 is unnecessarily increased at the initial stage. Thus, when the valve opening time becomes long, there is a possibility that the valve opening time may fall in the latter period until it enters the region where the valve opening cannot be maintained as shown by the broken line in FIG. For this reason, even if the injection pulse width of the fuel injection valve is increased, the valve opening period does not correspond and the valve is closed, resulting in a shortage of the fuel injection amount.
[0050]
In response to this, the present invention extends the period during which the needle valve 2 can be held open as a configuration in which the drive voltage supplied to the piezo actuator 10 is reduced stepwise or continuously when the engine is started.
[0051]
In the present embodiment, as indicated by a solid line in FIG. 4, a configuration in which the engine starting time when the valve opening period of the needle valve 2 is equal to or greater than a predetermined value is determined and the drive voltage supplied to the piezo actuator 10 is decreased in two stages. And
[0052]
In this way, the drive differential pressure of the needle valve 2 is increased stepwise in one injection as shown by the solid line in FIG. That is, by changing the drive voltage from 400 V to 200 V, the piezo actuator 10 contracts by one step, the differential pressure chamber 8 expands, and the pressure decreases. Although the differential pressure decreases with the passage of time, by changing the drive voltage from 200 V to 0 V before the differential pressure falls below the required valve opening holding force, the piezo actuator 10 further contracts and the differential pressure chamber 8 expands. Again, a large differential pressure between the differential pressure chamber 8 and the fuel pressure chamber 3 is secured. The differential pressure between the differential pressure chamber 8 and the fuel pressure chamber 3 is not proportional to the passage of time, but is proportional to the secondary pressure. However, it takes longer for the differential pressure to drop to a predetermined value. As a result, the drive differential pressure generated between the differential pressure chamber 8 and the fuel pressure chamber 3 does not increase until it enters the region where the valve opening cannot be maintained, and the valve opening period of the piezo actuator 10 is extended. At times, a sufficient amount of fuel can be secured.
[0053]
When the second fuel pump 51 functions sufficiently and the fuel pressure increases, the necessary valve opening period of the needle valve 2 becomes shorter than a predetermined value, so that the contraction amount of the piezo actuator 10 is maximized in one step. And Thereby, the maximum value of the drive differential pressure generated between the differential pressure chamber 8 and the fuel pressure chamber 3 is increased, and the responsiveness that the needle valve 2 opens against the coil spring 4 is increased. As a result, the fuel injection amount setting range (dynamic range) can be expanded to cope with higher engine output.
[0054]
The flowchart of FIG. 3 shows a routine for switching the fuel injection pattern, and is executed by the controller 19 at regular intervals.
[0055]
Explaining this, with the drive voltage supplied to the piezo actuator 10 set to 400 V and the needle valve 2 being closed, it is first determined in step 1 whether the required injection pulse width is greater than or equal to a predetermined value.
[0056]
If it is determined that the required injection pulse width is equal to or greater than the predetermined value, the process proceeds to step 2 where the drive voltage supplied to the piezo actuator 10 is reduced to 200V.
[0057]
Then, it progresses to step 3 and it is determined whether 1/2 of the request | requirement injection pulse width has passed.
[0058]
When it is determined that half of the required injection pulse width has elapsed, the process proceeds to step 4 where the drive voltage supplied to the piezo actuator 10 is reduced to OV.
[0059]
Subsequently, the routine proceeds to step 5 where it is determined whether or not the injection is completed when 2/2 of the required injection pulse width has elapsed.
[0060]
When it is determined that the required injection pulse width has passed, the process proceeds to step 6 where the drive voltage supplied to the piezo actuator 10 is increased to 400 V and the needle valve 2 is closed.
[0061]
Note that, in an operation state in which the required injection pulse width is shorter than a predetermined value, control for lowering the drive voltage supplied to the piezo actuator 10 to 0 V is performed by another routine (not shown).
[0062]
As another embodiment, as shown in FIG. 7, the drive voltage supplied to the piezo actuator 10 when the engine is started may be reduced in four stages.
[0063]
In this case, the drive differential pressure of the needle valve 2 is increased by four injections as shown in FIG. As a result, the drive differential pressure does not decrease until it enters the region where the valve opening cannot be maintained, the valve opening period of the piezo actuator 10 is extended, and a sufficient fuel injection amount can be ensured even when the engine is started.
[0064]
The flowchart of FIG. 6 shows a routine for switching the fuel injection pattern, and is executed by the controller 19 at regular intervals.
[0065]
Explaining this, with the drive voltage supplied to the piezo actuator 10 set to 400 V and the needle valve 2 being closed, it is first determined in step 1 whether the required injection pulse width is greater than or equal to a predetermined value.
[0066]
When it is determined that the required injection pulse width is equal to or greater than the predetermined value, the process proceeds to step 2 where the drive voltage supplied to the piezo actuator 10 is reduced to 300V.
[0067]
Then, it progresses to step 3 and it is determined whether 1/4 of the request | requirement injection pulse width has passed.
[0068]
If it is determined that ¼ of the required injection pulse width has elapsed, the process proceeds to step 4 where the drive voltage supplied to the piezo actuator 10 is reduced to 200V.
[0069]
Subsequently, the routine proceeds to step 5 where it is determined whether half of the required injection pulse width has elapsed.
[0070]
When it is determined that 1/2 of the required injection pulse width has elapsed, the process proceeds to step 6 where the drive voltage supplied to the piezo actuator 10 is reduced to 100V.
[0071]
Subsequently, the routine proceeds to step 7 where it is determined whether 3/4 of the required injection pulse width has elapsed.
[0072]
If it is determined that 3/4 of the required injection pulse width has elapsed, the routine proceeds to step 7 where the drive voltage supplied to the piezo actuator 10 is reduced to 0V.
[0073]
Subsequently, the routine proceeds to step 9, where it is determined whether or not the injection has ended after the required injection pulse width has elapsed.
[0074]
If it is determined that the required injection pulse width has elapsed, the process proceeds to step 10 where the drive voltage supplied to the piezo actuator 10 is increased to 400 V and the needle valve 2 is closed.
[0075]
Note that, in an operation state in which the required injection pulse width is shorter than a predetermined value, control for lowering the drive voltage supplied to the piezo actuator 10 to 0 V is performed by another routine (not shown).
[0076]
As yet another embodiment, the drive voltage supplied to the piezo actuator 10 may be reduced in multiple stages as the required injection pulse width of the piezo actuator 10 becomes longer.
[0077]
Thus, the valve opening period is effectively extended while ensuring the operation responsiveness of the needle valve 2 by reducing the rate of change in which the amount of contraction of the piezoelectric actuator 10 increases as the required injection pulse width increases. be able to.
[0078]
By the way, the lower the fuel viscosity, the more easily the fuel in the differential pressure chamber 8 leaks into the fuel pressure chamber 3, and the pressure drop in the differential pressure chamber 8 becomes rapid.
[0079]
As yet another embodiment, the driving voltage supplied to the piezo actuator 10 may be reduced in multiple steps as the fuel viscosity is lower when the engine is started.
[0080]
In the present embodiment, the engine coolant temperature is read as a signal representative of the fuel viscosity, and the drive voltage supplied to the piezo actuator 10 when the engine coolant temperature is lower than a predetermined value is low. The drive voltage supplied to the piezo actuator 10 when the engine coolant temperature is lower than a predetermined value is high.
[0081]
Note that the air temperature taken in by the engine may be read as a signal representative of the fuel viscosity.
[0082]
As shown in FIG. 9, the lower the engine coolant temperature, the lower the viscosity of the fuel. While the fuel injection valve 7 is open, the fuel pressure valve 8 passes from the differential pressure chamber 8 to the fuel pressure chamber 3 side through the throttle passage 2c. The amount of fuel that escapes increases.
[0083]
For this reason, as shown in FIG. 10, the higher the engine coolant temperature, the faster the drive differential pressure generated before and after the needle valve 2 decreases.
[0084]
In response to this, the drive voltage supplied to the piezo actuator 10 is lowered in multiple stages as the fuel viscosity is lower when the engine is started, so that the drive differential pressure can be lowered until it enters the region where the valve opening cannot be maintained. It is avoided and a sufficient fuel injection amount can be secured even when the engine is started.
[0085]
In response to the increase in the rate of change in which the fuel pressure in the differential pressure chamber decreases in accordance with the decrease in the viscosity of the fuel, the needle valve is configured to increase the rate of change in which the amount of contraction of the piezoelectric actuator 10 increases. The valve opening period of 2 can be effectively extended.
[0086]
The flowchart of FIG. 8 shows a routine for switching the fuel injection pattern, and is executed by the controller 19 at regular intervals.
[0087]
Explaining this, with the drive voltage supplied to the piezo actuator 10 set to 400 V and the needle valve 2 being closed, it is first determined in step 1 whether the required injection pulse width is greater than or equal to a predetermined value.
[0088]
If it is determined that the required injection pulse width is equal to or greater than the predetermined value, the process proceeds to step 2 to determine whether the engine coolant temperature detected by a water temperature sensor (not shown) is equal to or greater than the predetermined value.
[0089]
When it is determined that the temperature of the engine coolant is low or greater than the predetermined value, the process proceeds to step 4 where the drive voltage supplied to the piezo actuator 10 is decreased in four stages. On the other hand, when it is determined that the temperature of the engine coolant is lower than the predetermined value, the process proceeds to step 3 where the drive voltage supplied to the piezo actuator 10 is decreased in two stages.
[0090]
As another embodiment, as shown in FIG. 12, the driving voltage supplied to the piezo actuator 10 at the time of engine start may be gradually reduced as the valve opening time becomes longer.
[0091]
In this case, the drive differential pressure of the needle valve 2 is continuously increased during one injection period. As a result, the drive differential pressure does not decrease until it enters the region where the valve opening cannot be maintained, the valve opening period of the piezo actuator 10 is extended, and a sufficient fuel injection amount can be ensured even when the engine is started.
[0092]
The flowchart of FIG. 11 shows a routine for switching the fuel injection pattern, and is executed by the controller 19 at regular intervals.
[0093]
Explaining this, with the drive voltage supplied to the piezo actuator 10 set to 400 V and the needle valve 2 being closed, it is first determined in step 1 whether the required injection pulse width is greater than or equal to a predetermined value.
[0094]
When it is determined that the required injection pulse width is equal to or greater than the predetermined value, the process proceeds to step 2 where the drive voltage supplied to the piezo actuator 10 is reduced to 300V.
[0095]
Subsequently, the process proceeds to step 3 where the voltage drop is calculated as initial boost / injection pulse width = 300− / injection pulse width, and the drive voltage supplied to the piezo actuator 10 is gradually increased as the valve opening time becomes longer. Reduce.
[0096]
Subsequently, the routine proceeds to step 4, where it is determined whether or not the injection is completed when 2/2 of the required injection pulse width has elapsed.
[0097]
When it is determined that the injection is completed when 2/2 of the required injection pulse width has elapsed, the routine proceeds to step 5 where the drive voltage supplied to the piezo actuator 10 is increased to 400 V and the needle valve 2 is closed.
[0098]
Note that, in an operation state in which the required injection pulse width is shorter than a predetermined value, control for lowering the drive voltage supplied to the piezo actuator 10 to 0 V is performed by another routine (not shown).
[0099]
As yet another embodiment, as shown in FIG. 13, a pressure sensor 20 that detects the pressure in the differential pressure chamber 8 is provided. And fuel pressure chamber 3 Pressure Difference A configuration may be adopted in which the drive voltage supplied to the piezo actuator 10 is lowered as the voltage drops below a predetermined value.
[0100]
As a result, it is possible to avoid a decrease in the drive differential pressure until it enters the region where the valve opening cannot be maintained, the valve opening period of the piezoelectric actuator 10 is extended, and a sufficient fuel injection amount can be ensured even when the engine is started.
[0101]
The flowchart of FIG. 14 shows a routine for switching the fuel injection pattern, and is executed by the controller 19 at regular intervals.
[0102]
Explaining this, with the drive voltage supplied to the piezo actuator 10 set to 400 V and the needle valve 2 being closed, it is first determined in step 1 whether the required injection pulse width is greater than or equal to a predetermined value.
[0103]
If it is determined that the required injection pulse width is equal to or greater than the predetermined value, the process proceeds to step 2 to determine whether or not the initial voltage application is present.
[0104]
If it is determined that the initial voltage is applied, the process proceeds to step 5 where the drive voltage supplied to the piezoelectric actuator 10 is reduced to 300V.
[0105]
When it is determined that it is not at the time of initial voltage application, the process proceeds to step 3 to determine whether or not the required injection pulse width has elapsed.
[0106]
When it is determined that the required injection pulse width has passed, the process proceeds to step 6 where the drive voltage supplied to the piezo actuator 10 is increased to 400 V and the needle valve 2 is closed.
[0107]
When it is determined that the required injection pulse width has not elapsed, the process proceeds to step 4 where the differential pressure chamber 8 is based on the detection value from the pressure sensor 20. And fuel pressure chamber 3 Pressure difference It is determined whether or not the value falls below a predetermined value.
[0108]
Differential pressure chamber 8 And fuel pressure chamber 3 Pressure difference When it is determined that the value has decreased below the predetermined value, the process proceeds to step 7 where the drive voltage supplied to the piezoelectric actuator 10 is changed to the previous drive voltage. From Predetermined value Subtracted value and The configuration is as follows.
[0109]
Note that, in an operation state in which the required injection pulse width is shorter than a predetermined value, control for lowering the drive voltage supplied to the piezo actuator 10 to 0 V is performed by another routine (not shown).
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a fuel injection valve showing an embodiment of the present invention.
FIG. 2 is a system diagram of a fuel supply system.
FIG. 3 is a flowchart showing the same control content.
FIG. 4 is a characteristic diagram showing the relationship between the ejection pulse width and the drive voltage.
FIG. 5 is a characteristic diagram showing the relationship between the injection pulse width and the needle valve drive differential pressure.
FIG. 6 is a flowchart showing the contents of control in another embodiment.
FIG. 7 is a characteristic diagram that similarly shows the relationship between the injection pulse width, the drive voltage, and the needle valve drive differential pressure.
FIG. 8 is a flowchart showing control contents in still another embodiment.
FIG. 9 is a characteristic diagram showing the relationship between fuel viscosity and engine coolant temperature.
FIG. 10 is a characteristic diagram showing the relationship between the valve opening time of the needle valve and the drive differential pressure.
FIG. 11 is a flowchart showing control contents in still another embodiment.
FIG. 12 is a characteristic diagram that similarly shows the relationship between the injection pulse width, the drive voltage, and the needle valve drive differential pressure.
FIG. 13 is a cross-sectional view of a fuel injection valve showing still another embodiment.
FIG. 14 is a flowchart showing the same control content.
[Explanation of symbols]
1 Nozzle body
1b nozzle
2 Needle valve
2c Piston part
3 Fuel pressure chamber
4 Coil spring
5 Restricted passage
6 Fuel inlet
7 Fuel injection valve
8 Differential pressure chamber
9 Casing
10 Piezo actuator
11 Piston
19 Controller
20 Pressure sensor

Claims (6)

An electrostrictive actuator that expands when a voltage or magnetic field is applied and contracts when the applied voltage or magnetic field is interrupted ;
A differential pressure chamber in which the volume increases and the pressure decreases as the electrostrictive actuator contracts, and the volume decreases and the pressure increases as the electrostrictive actuator extends ,
A fuel pressure chamber through which pressurized fuel is guided;
A throttle passage communicating the fuel pressure chamber and the differential pressure chamber;
A needle valve that is displaced according to the pressure difference between the fuel pressure chamber and the differential pressure chamber;
A spring that urges the needle valve in the closing direction;
A nozzle opening and closing by a needle valve;
An engine fuel injection device comprising:
Maintaining the contraction amount of electro-magnetostrictive actuator pressure difference generated between the differential room and the fuel pressure chamber by changing along with the lapse valve opening time of the needle valve, the higher retaining force required to open An engine fuel injection apparatus comprising a control means. It said control means fuel injection device for an engine according to claim 1, characterized in that it has a configuration in which stepwise vary with to elapse needle valve opening time of the contraction amount of electro-magnetostrictive actuator. It said control means fuel injection device for an engine according to claim 1, characterized in that where the structure is changed continuously with the to elapse needle valve opening time of the contraction amount of electro-magnetostrictive actuator. A determination means for determining an operation condition in which a required valve opening period of the needle valve is a predetermined value or more;
The control means while changing with the to elapse needle valve opening time of the contraction of the electro-magnetostrictive actuator in the operating conditions required valve opening period of the needle valve is equal to or greater than a predetermined value, a request for the needle valve open fuel injection device for an engine according to any one of claims 1, characterized in that the valve period has a structure for changing the contraction amount of electro-magnetostrictive actuator uniformly in a shorter operating conditions than a predetermined value 3. Comprising a fuel viscosity detecting means for detecting the viscosity of the fuel;
The control means of the engine according to any one of claims 1 to 4, characterized in that it has a structure to increase the contraction rate of change of the electromagnetic strain actuator according to decrease the viscosity of the fuel Fuel injection device. Pressure detecting means for detecting the pressure in the differential pressure chamber;
The control means of the engine according to claim 1, characterized in that where the structure is increased in response to the pressure difference between the contraction amounts differential compartment and the fuel pressure chamber of the electro-magnetostrictive actuator drops below a predetermined value Fuel injection device.

Images