JP3968846B2 - Fuel injection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel injection device suitable for a direct injection type spark ignition type internal combustion engine.
[0002]
[Prior art and problems to be solved]
In a spark ignition type internal combustion engine, one that improves fuel efficiency, output, and exhaust emission performance by stratified combustion by injecting and supplying fuel directly into a cylinder mainly after the compression stroke is known. In order to fully exhibit the characteristics of such a direct injection engine, it is desirable to appropriately control the fuel particles injected and supplied into the cylinder in accordance with the operating state. For this purpose, for example, disclosed in JP-A-7-166927 As described above, there has been proposed an apparatus in which the degree of atomization of fuel is controlled by variably controlling the pressure of fuel supplied to the fuel injection valve. .
[0003]
By the way, since the combustion stability at the time of stratification operation is strongly influenced by the degree of stratification, the applicant of the present application has an appropriate fuel injection rate (fuel injection amount per unit time) even in the same stratification operation. Was confirmed by experiments. If the fuel pressure is changed, not only the fuel atomization but also the fuel injection rate changes. However, since the above prior art focuses only on the fuel atomization, the fuel pressure is uniformly applied during stratified combustion. It only increased. In addition, if an appropriate fuel injection rate is obtained only by the fuel pressure, a high-capacity fuel pump is required to cope with a very wide range of fuel pressure and high fuel pressure. The problem arises that fuel consumption deteriorates due to the increase.
[0004]
In addition to the above-described prior art, a technique for controlling the fuel injection rate by variably controlling the stroke amount of the valve body of the fuel injection valve is disclosed in Japanese Patent Laid-Open No. 5-321786. The fuel injection rate is variably controlled when switching between two types of fuels having different heat generation amounts per hit, and there is no disclosure of application to a direct injection internal combustion engine that performs stratified combustion.
[0005]
The present invention has been made paying attention to such conventional problems, and in a direct injection type spark ignition engine, at least during the stratified combustion operation, the stroke amount of the valve body of the fuel injection valve is variably controlled with high accuracy. An object of the present invention is to provide a fuel injection valve and a fuel injection device capable of optimal fuel injection in a wide range of engine operation.
[0006]
[Means for Solving the Problems]
In order to solve the above problem, the invention of claim 1 includes means for detecting an engine operating state, fuel injection control means for controlling a valve opening period and a valve opening timing of the fuel injection valve in accordance with the engine operating state, and The fuel injection control means performs stratified combustion by mainly injecting fuel in the latter half of the compression stroke when the engine is in a predetermined operating range, and injecting fuel mainly in the intake stroke when in an operating state other than the above. In a fuel injection control device for a direct injection spark ignition engine configured to perform homogeneous combustion, a variable stroke mechanism that changes the maximum stroke amount of the fuel injection valve, and at least the engine operating state during stratified combustion Stroke amount control means for controlling the maximum stroke amount of the fuel injection valve and making the maximum stroke amount smaller in the high load region during the stratified operation than in the low load region .
[0008]
According to a second aspect of the present invention, in the first aspect of the present invention, the maximum stroke amount of the fuel injection valve is made larger in the high rotation range during the stratified operation than in the low rotation range.
[0009]
According to a third aspect of the present invention, in the first or second aspect of the present invention, the maximum stroke amount of the fuel injection valve is set to be larger than that of the low rotation or low load region in a high rotation and high load region during homogeneous operation.
[0010]
According to a fourth aspect of the present invention, in the first to third aspects of the present invention, the maximum stroke amount of the fuel injection valve is reduced in an idle state during stratified operation.
[0011]
According to a fifth aspect of the present invention, in the first to fourth aspects of the present invention, there is provided pressure control means for controlling the pressure of the fuel supplied to the fuel injection valve in accordance with the engine operating state, and the pressure is low in the high rotation range during the stratified operation. The fuel pressure was increased above the rotation range.
[0012]
According to a sixth aspect of the present invention, in the fifth aspect of the present invention, the fuel pressure is increased in a high rotation and high load range during homogeneous operation than in a low rotation or low load range.
[0013]
The invention of claim 7 is the invention of claim 5 or 6, wherein the fuel pressure is reduced in an idle state during stratified operation.
[0014]
[Action / Effect]
According to the first aspect of the invention, by using the fuel injection valve having the variable stroke mechanism, high-precision fuel injection control at an optimal injection rate in accordance with the operating state during stratified combustion of the direct injection spark ignition engine. Therefore, it is possible to cause the engine to exhibit good output, operability and exhaust emission performance in a wide operating range. The stroke amount control means is designed to make the maximum stroke amount of the fuel injection valve smaller in the high load range during the stratified operation than in the low load region. The generation of smoke due to excessive concentration of fuel can be avoided.
[0016]
According to the invention of claim 2 , since the stroke amount control means is configured to make the maximum stroke amount of the fuel injection valve larger in the high rotation range during the stratified operation than in the low rotation range, the air flow is active and the fuel Therefore, the required fuel amount can be supplied within a short time in a high rotational speed range in which the fuel is easily diffused to concentrate the fuel to some extent, thereby enabling appropriate stratified combustion. According to the invention of claim 5, since the fuel pressure is increased in the high rotation region during the stratification operation than in the low rotation region, the fuel spray angle from the injection valve nozzle portion is reduced and the fuel is increased. It is possible to increase the penetration force of the particles and further promote the concentration of fuel in the piston cavity portion or the like.
[0017]
According to the invention of claim 3 , since the stroke amount control means is configured to increase the maximum stroke amount of the fuel injection valve in the high rotation and high load range during homogeneous operation, than in the low rotation or low load range, It is possible to suppress the generation of smoke by increasing the injection rate in this operating region where the amount of fuel is large and smoke is likely to be generated. According to the invention of claim 6, the fuel pressure is increased in the high rotation and high load range during the homogeneous operation than in the low rotation or low load range, so that the injection rate can be further increased.
[0018]
According to the invention of claim 4 , since the stroke amount control means is designed to reduce the maximum stroke amount of the fuel injection valve in the idle state during the stratified operation, in the idle operation region where the air flow in the cylinder is weak. By extending the injection period, it is possible to promote appropriate diffusion of fuel and ensure good combustibility. Further, according to the invention of claim 7, since the fuel pressure is reduced in the idling state during the stratified operation, the penetration force of the fuel particles is reduced while the spray angle of the injected fuel is widened, thereby spreading the fuel. Can encourage more.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0020]
FIG. 1 shows a schematic configuration of a direct injection internal combustion engine to which the present invention is applicable. In the figure, 1 is a body (cylinder block) of a direct injection internal combustion engine, 2 is a cylinder head, 3 is a piston, 4 is a spark plug, 5 is a fuel injection valve, 6 is an intake passage, 7 is an exhaust passage, and 8 is a throttle valve. , 9 indicates an intake valve, and 10 indicates an exhaust valve. Reference numeral 11 denotes a control device composed of a microcomputer comprising a CPU, ROM, RAM, I / 0, etc., which constitutes the pressure control means, fuel injection control means, stroke amount control means, etc. of the present invention. The control device 11 controls the fuel injection amount, the injection timing, the fuel pressure, and the valve opening stroke amount of the injection valve based on the following signals from the operating state detecting means.
[0021]
The operating state detection means includes an air flow meter 12 that detects the intake air amount, a crank angle sensor 13 that detects the engine speed, a water temperature sensor 14 that detects the cooling water temperature, an exhaust oxygen sensor 15 that detects the exhaust oxygen concentration, and a throttle valve. A throttle opening sensor 16 for detecting the opening of the vehicle, a vehicle speed sensor 17 for detecting the traveling speed of the vehicle, and a fuel pressure sensor 18 for detecting the pressure of the fuel supplied to the fuel injection valve 5. Reference numeral 20 denotes a fuel pressure control device that variably controls the pressure of the fuel supplied to the fuel injection valve 5 based on a command from the control device.
[0022]
FIG. 2 shows details of the fuel injection valve 5. In the figure, 51 is a housing of the injection valve, 52 is a nozzle part fitted to the tip of the housing 51, and 53 is a core part fitted to the back side of the nozzle part in the housing 51. A solenoid coil 54 is installed in a space formed by the housing 51 and the core portion 53.
[0023]
A spring seat 57 is screwed into the cylinder at the center of the core portion 53, and one end of the spring 58 is fixed to the spring seat 57, and the other end of the spring 58 is accommodated in the nozzle portion 52. The valve body (needle valve) 59 abuts from behind.
[0024]
When the solenoid coil 54 is not energized, the needle valve 59 is pressed against the inner side of the nozzle hole 63 provided at the tip of the nozzle portion 52 by the urging force of the spring 58 and maintains the valve closed state. On the other hand, when the solenoid coil 54 is energized, a magnetic circuit is formed by the core portion 53 and the surrounding magnetic body, the valve body 59 rises against the tension of the spring 58, and the nozzle hole 63 is opened.
[0025]
The fuel passes from the fuel inlet portion 55 provided at the end portion of the core portion 53 through the spring seat 57 and the hollow portion of the spring 8, and further passes through a gap or a groove portion provided between the valve body 59 and the nozzle portion 52. Then, it is guided to the nozzle hole 63 portion.
[0026]
An intermediate portion of the valve body 59 is provided with a locking portion 64 in a flange shape, and an annular regulating portion 65 made of a piezo element is installed at a position facing the locking portion 64 with a predetermined gap. Thus, a variable stroke mechanism that changes the maximum stroke amount from the valve closing position of the valve body 59 is configured. That is, the amount of displacement of the valve body 59 when a current flows through the coil 4 is regulated by contact between the locking portion 64 and the regulating portion 65. At this time, a control current is applied to the regulating portion 65 made of a piezo element. By increasing the length in the axial direction, the stroke amount of the valve body 59 is reduced by this increase, and the injection valve has a small flow rate characteristic. On the other hand, when the control current is not applied to the restricting portion 65 or when the control current in the opposite direction is applied, the length of the restricting portion 65 in the axial direction is small, and the stroke amount of the valve body 59 is accordingly increased. Since it becomes large, the injection valve has a large flow rate characteristic.
[0027]
FIG. 3 is a flowchart showing an outline of the operation of the control device 11. First, upon receiving a signal from the operating state detecting means (12 to 18), the control device 11 determines the current engine operating state (steps 301 to 302). Here, for example, whether to perform stratified combustion or homogeneous combustion is first determined based on the operating range setting as shown in FIG. 4, and the injection valve stroke amount (control to the restricting portion 65 is controlled) according to each operating state. Voltage), fuel pressure, injection timing, and injection amount (injection pulse width) are determined (steps 303 to 306, 308 to 311). The various control amounts are set by previously forming a map for assigning settings as shown in FIG. 4 according to the engine speed and load, and searching for the map. The control amounts thus set are finally output to the fuel injection valve 5 or the fuel pressure control device 20 (step 307). Such a control loop is repeatedly executed at a predetermined cycle, whereby the fuel injection amount and the like are always controlled to an appropriate amount according to the engine operating state.
[0028]
FIG. 4 shows a setting example of the stratified combustion and homogeneous combustion region, fuel pressure, and injection valve stroke of the present embodiment. In the figure, stratified combustion is performed in a relatively low load and low rotational speed region, which is shaded, and homogeneous fuel is set in a higher load or rotational speed region. Further, the fuel pressure and the injection valve stroke amount are controlled in the operation state set in advance in each region.
[0029]
In FIG. 4, (1) is a region with a relatively high load in the stratified combustion region. In this region, the amount of fuel injection is large. Therefore, if the injection rate is high, the fuel is excessively concentrated and the generation of smoke increases and the combustion is stabilized. Tend to decrease. Therefore, in this region, the injection time is lengthened by reducing the injection valve stroke amount to provide low flow characteristics.
[0030]
(2) is a region with a relatively high rotational speed in the stratified combustion region. In this region, the air flow in the cylinder becomes active and the fuel tends to diffuse, so the injection rate is increased and the fuel tends to concentrate. Better. Therefore, the stroke amount of the injection valve is increased to obtain a large flow rate characteristic so that necessary fuel can be injected and supplied for a short time. Further, by increasing the fuel pressure, the spray angle from the injection valve nozzle portion is reduced and the penetration force of the injected fuel particles is also increased, so that the fuel can be more concentrated in the piston cavity portion.
[0031]
(3) is the idle rotation region in the stratified combustion region. In this region, the air flow in the cylinder is weak and the fuel tends to concentrate too much. By reducing the injection valve stroke amount and extending the injection period, It is preferable to diffuse the fuel to some extent. Further, by doing so, the dynamic range of the fuel injection valve is expanded in the small flow rate direction, and the injection amount control accuracy in the small flow rate region is enhanced. In this idling region, simultaneously reducing the fuel pressure increases the fuel spray angle from the injection nozzle and the penetration force of the injected fuel particles is weakened, so that the diffusion of fuel can be promoted.
[0032]
(4) is a region where the load and rotation speed are relatively high in the homogeneous combustion region, and in such a region where the absolute amount of fuel is large, smoke tends to be generated if the fuel injection period is long. To increase the fuel injection rate. Moreover, the dynamic range of the fuel injection valve can be expanded in the large flow rate direction by increasing the stroke amount. If the fuel pressure is further increased in this operating range, it is possible to increase the injection rate and obtain good combustibility.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an embodiment of a direct injection engine to which the present invention is applicable.
FIG. 2 is a longitudinal sectional view showing an embodiment of a fuel injection valve.
FIG. 3 is a flowchart showing an outline of a control operation according to the embodiment of the present invention.
4 is an explanatory diagram showing the relationship between the engine operating state, fuel pressure, and fuel injection valve stroke amount in the embodiment. FIG.
[Explanation of symbols]
1. Body of a direct injection internal combustion engine (cylinder block)
2 Cylinder head 3 Piston 4 Spark plug 5 Fuel injection valve 6 Intake passage 7 Exhaust passage 8 Throttle valve 9 Intake valve 10 Exhaust valve 11 Control device 12 Air flow meter 13 Crank angle sensor 14 Water temperature sensor 15 Exhaust oxygen sensor 16 Throttle opening sensor 17 Vehicle speed sensor 18 Fuel pressure sensor 20 Fuel pressure control device 51 Fuel injection valve housing 52 Nozzle part 53 Core part 54 Solenoid coil 55 Fuel inlet part 57 Spring seat 58 Spring 59 Valve body 62 Nozzle part 63 Injection hole 64 Locking part 65 Restriction part

Claims (7)

A means for detecting an engine operating state; and a fuel injection control means for controlling a valve opening period and a valve opening timing of the fuel injection valve according to the engine operating state. In some cases, the direct injection type spark ignition engine in which fuel is mainly injected in the latter half of the compression stroke to perform stratified combustion, and in other operating states, fuel is mainly injected into the intake stroke to perform homogeneous combustion. In the fuel injection device,
A variable stroke mechanism for changing the maximum stroke amount of the fuel injection valve ;
Stroke amount control means for controlling the maximum stroke amount of the fuel injection valve according to at least the engine operating state at the time of stratified combustion , and making the maximum stroke amount smaller than the low load region in the high load region during stratified operation ,
Fuel injection system, characterized in that it comprises a.   2. The fuel injection device according to claim 1, wherein the stroke amount control means makes the maximum stroke amount of the fuel injection valve larger than that in the low rotation region in the high rotation region during the stratified operation. 3. The fuel injection according to claim 1 , wherein the stroke amount control means makes the maximum stroke amount of the fuel injection valve larger in the high rotation and high load range during the homogeneous operation than in the low rotation or low load range. apparatus. The fuel injection device according to any one of claims 1 to 3, wherein the stroke amount control means reduces the maximum stroke amount of the fuel injection valve in an idle state during stratified operation. Pressure control means for controlling the pressure of the fuel supplied to the fuel injection valve according to the engine operating state;
The fuel injection device according to any one of claims 1 to 4, wherein the pressure control means is configured to increase the fuel pressure in a high rotation range during stratified operation than in a low rotation range. . 6. The fuel injection device according to claim 5, wherein the pressure control means is configured to increase the fuel pressure in a high rotation and high load range during homogeneous operation than in a low rotation or low load range. The fuel injection device according to claim 5 or 6, wherein the pressure control means is configured to reduce the fuel pressure in an idle state during stratified operation .

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