JP2002180879A - Method of protecting internal combustion engine from excessive pressure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely protect an internal combustion engine from the excessive pressure in a cylinder while reducing the manufacturing cost, and to reduce the difference in output among the engines of the same type. SOLUTION: The internal pressure of at least one cylinder 1 of the internal combustion engine is continuously monitored in this device and this method of protecting the internal combustion engine from the excess pressure. When the internal pressure is over a predetermined threshold value Pth, the operation of pressure peak controllers C, C', C", C"' is started, and an introduction amount of the fuel and/or the combustion of the fuel are adjusted to prevent the internal pressure from being over the allowable maximum value Pmax.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for protecting an internal combustion engine when excessive pressure is measured in at least one cylinder of the internal combustion engine. In addition, the invention relates to an apparatus for performing such a method.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for improved output and improved fuel consumption efficiency.
utput) was continually improving. The specific output is defined as a ratio between the output of the internal combustion engine and the weight. As a result of this improvement, the pressure in the cylinder has increased significantly and the mechanical load has reached a level where the material limits are reached. Therefore, it is important to design the internal combustion engine such that it remains within the safe limits even when the pressure generated in the cylinder of the internal combustion engine is severest.

[0003] This is usually achieved by careful standardization of the fueling method. Such common pressure peak control methods must incorporate significant safety factors. One of the reasons for doing this is that the tolerances that occur during engine production
In the case of an engine, this can lead to a considerable variation, which can be a difference of 20 bar in the maximum cylinder pressure. Such variations, which vary from engine to engine, are generally the result of the following factors: That is, 1. Due to the inaccurate flywheel installation,
1. Error at top dead center 2. Difference in the internal space of each cylinder head This is the tolerance of the fuel injection system.

[0004] Differences in engine-to-engine pressure of up to 20 bar have various undesirable consequences. Engine design technicians who must achieve the target output need to use a higher or more expensive material because it needs to set a safety limit for the pressure peak at 20 bar. It drives up costs. For consumers, a difference of 20 bar can lead to a huge difference in engine power. That is, there is a consumer who is provided with a vehicle whose performance is clearly lower than that of an engine of the same type.

[0005]

Under these circumstances, it is an object of the present invention to ensure that the internal combustion engine is protected from excessive pressure in the cylinder while reducing manufacturing costs. And to reduce the difference in output between engines of the same type.

[0006]

The object of the invention is achieved with a method having the features of claim 1 and an apparatus having the features of claim 7. The dependent claims have a configuration that provides a further advantageous effect.

The above method protects the internal combustion engine from excessive pressure measured in at least one cylinder of the internal combustion engine,
Works. Here, methods for measuring the pressure in the cylinder for various purposes are known. For example, the measured pressure can be measured in U.S. Patents 4,397,285, 4,549,513, 4,846,128, 4,06
Nos. 3,238 and 5,676,113 are used to control the ignition timing to increase the maximum output of the engine.
U.S. Pat. ing. Finally, U.S. Pat. Nos. 4,516,401 and 4,483,146 disclose how the compressor of a turbocharged engine is controlled by feeding back cylinder pressure.

[0008] The method according to the invention comprises the step of: when the pressure peak in one of the cylinders of the internal combustion engine exceeds a predetermined threshold value;
It is characterized in that the introduction of fuel and / or the combustion of fuel are adjusted so as to depart from a predetermined value by an engine controller, and the adjustment is performed such that the pressure peak does not exceed a maximum value. Here, the pressure peak refers to one engine
This is the maximum in-cylinder pressure generated during the cycle.

In this method, the pressure peak of at least one cylinder is continuously monitored and when a predetermined threshold value is exceeded,
The introduction of fuel predetermined by the engine controller and / or
Alternatively, since the combustion of the fuel is appropriately regulated by the pressure peak, it is ensured that the maximum value of the cylinder pressure which is regarded as the load limit of the internal combustion engine is not exceeded. The threshold at which this method starts working is usually 5
~ 20%, preferably about 10%, which is still below the maximum allowable cylinder pressure.

Specifically, the introduction of fuel and / or the combustion of fuel are controlled by adjusting the amount of fuel supplied to the internal combustion engine, the ignition timing of the air-fuel mixture, and / or the fuel injection timing.
Can be adjusted. By using the above control variables, it is possible to selectively influence the rise in the pressure in the space of the cylinder. For example, when reducing the fuel supply,
The pressure peak in the corresponding cylinder is correspondingly reduced.

Adjusting the fuel quantity involves only reducing the quantity of fuel to be supplied as calculated by the engine controller.
This means that the method according to the invention can, if necessary, reduce the amount of fuel "normally" supplied by the engine controller, but never increase it. Such a reduction in fuel quantity achieves the targeted goal of limiting excessive pressure in the cylinder space.

In the simplest form of the method, the pressure is measured in only one cylinder of a multi-cylinder internal combustion engine, and it is assumed that it is representative of all cylinders. However, one improvement of this method may be to measure the pressure in a plurality of cylinders, in particular in each cylinder bank of the internal combustion engine and / or in each cylinder of the internal combustion engine. As a result, the accuracy and reliability of protection from overpressure can be increased.

Further, the method of the present invention includes the step of introducing fuel and / or
Alternatively, the adjustment of fuel combustion may be different between cylinders. In the simplest case, the introduction of fuel and / or the combustion of fuel are adjusted in the same way for all engine cylinders. Preferably, however, the variables mentioned above are adjusted individually for each cylinder bank and / or each cylinder of the internal combustion engine. In this way, the pressure, which is only a problem for a particular cylinder, can be reduced without undesirably adversely affecting the output of the unaffected cylinders.
It can be selectively adjusted in such a cylinder.

According to one preferred embodiment of the present invention, the fuel introduction and / or the combustion of the fuel are performed unless the pressure peak in the cylinder has set a relatively low pressure value by the engine controller. It is adjusted so as to approach the maximum value as much as possible. The method according to the invention basically only intervenes when the engine controller is making settings for the introduction of combustion and / or for the combustion of fuel which lead to pressures above a predetermined threshold. When the threshold value is exceeded, the method according to the invention starts operating, affecting the introduction of fuel and / or the combustion of fuel until an effect of reducing the pressure value is obtained. Nevertheless, it is advantageous to attempt to bring the pressure peak in the cylinder as close as possible to the maximum allowable maximum in order to get as close as possible to the state that the engine controller is aiming for.
However, as soon as the engine controller makes settings for fuel introduction and / or fuel combustion, which can lead to relatively low pressure values, this new setting will take effect immediately.

The present invention also provides that at least one pressure sensor arranged in a cylinder of the internal combustion engine is connected to an input terminal thereof, and a control device for fuel introduction and / or combustion of fuel is connected to an output terminal thereof. An apparatus for performing the above method, further comprising a pressure peak controller. The pressure peak controller may also adjust fuel introduction and / or fuel combustion such that when the pressure peak in the cylinder exceeds a predetermined threshold, the pressure peak in the cylinder is less than a maximum value. ,
It is configured. This device makes it possible to carry out the advantageous effects of the method according to the invention described above.

[0016]

FIG. 1 is a schematic diagram of a control system for an internal combustion engine according to the present invention. The internal combustion engine may be either a spark ignition engine or a diesel engine. Specifically, the method according to the present invention can achieve a greater effect with a diesel engine. Diesel engines
This is because the pressure in the cylinder fluctuates at a relatively high pressure and the maximum pressure peak is much higher than that of the gasoline engine.

FIG. 1 shows four cylinders 1 of an internal combustion engine arranged side by side in a known manner. pressure sensor
3 are arranged in each cylinder 1, the pressure in the cylinder is measured via the pressure sensor, and the signal is transmitted to the pressure peak controller C. Such pressure peak controllers C, C ', C'',
C '''is individually provided for all cylinders of the engine.

The output of controller C acts on the actuator of the fuel injection system. This actuator also includes the injection valve 2 and, if appropriate, a fuel pump. The main controlled variable is the amount of fuel injected into each cylinder
F _q . This variable may be controlled independently for each cylinder, may be commonly controlled for a plurality of cylinders, or may be commonly controlled for all cylinders. Alternatively, the injection timing F _tim (for diesel engines) or ignition timing (for gasoline engines) can be controlled instead of or together with the fuel injection quantity.

The sensor used by the controller may be of any type as long as it can display the pressure P _cyl in a plurality of cylinders or all cylinders. Therefore, such a sensor is hereinafter referred to as an in-cylinder pressure sensor. Typical sensors include direct in-cylinder pressure sensors, such as piezoelectric or optical sensors, mounted directly inside the combustion chamber, and piezoelectric sensors mounted inside spark or glow plugs, or mounted outside the combustion chamber. There is an indirect cylinder pressure sensor such as an accelerometer that is used. After appropriate pre-processing and standardization, the output of the sensor is converted into a pressure signal in a known manner. The higher the accuracy of such a pressure signal, the better the control according to the invention can be performed and the better the invention can be used.

FIG. 1 shows that there is one in-cylinder pressure sensor 3 for each cylinder, and one pressure peak controller C,
Although a system where C ', C ", C'" is present is shown, the invention is also applicable to engines where not all cylinders have sensors. For example, it is possible to provide sensors in only one cylinder per engine or, in a V-type engine, only in one cylinder per cylinder bank. An arrangement of various embodiments is illustrated in FIG. 2 and the following embodiments are possible. a) One sensor per cylinder, one controller per cylinder b) One sensor per cylinder, one controller per cylinder bank c) One sensor per cylinder, per engine control D) One sensor per cylinder bank, one controller per cylinder bank e) One sensor per cylinder bank, one controller per engine f) Sensor per engine One, one controller per engine.

Here, if one sensor is attached to each cylinder, a better output can be obtained. Table 1 shows that manufacturing tolerances can be offset as a result of the choice of sensor arrangement.

[Table 1]

FIG. 3 is a flowchart of a control algorithm that can be used. In process block 17, the base fuel amount is calculated by the engine controller based on the accelerator pedal depression amount determined by the driver and the signal 10 of another sensor. The result of this calculation is the amount F _q ^d of fuel to be injected into the cylinder.

At the same time, the pressure peak P _peak is detected by the pressure peak detector 13 which receives the data 12 of the cylinder pressure P _cyl . This pressure peak P _peak is determined to be the maximum pressure in one engine cycle. This is determined to be once per engine cycle. Pressure peak P
_peak remains in buffer 14 until overwritten with the new value. This can be done once per cycle or at a desired rate depending on the location of the pressure sensors and the number of pressure peak controllers.

In the first branch of the algorithm, the pressure peak P _peak is sent to an adder, where it is the maximum allowable pressure P _{max in the} cylinder stored in block 15
Is subtracted from the value of The difference formed in this way is
It is supplied to the P _max cascade controller 16. The purpose of this controller is to calculate the amount of fuel to be injected such that the pressure peak _Ppeak is adjusted to the maximum allowable pressure _Pmax . This controller provides a proportional integral (PI) with "anti-windup" properties to ensure a smooth transition from and to the original fueling method (blocks 18 and 19). ) Controller or proportional integral difference (PI
D) A controller is generally used. The controller should be standardized to eliminate any excessive pressure. The output of the controller 16 is composed of the values F _q ^c for introducing the fuel.

At decision block 18, the pressure peak P
_peak is compared to a predetermined threshold value _Pth which is selected as a reference value below the maximum pressure _Pmax . When the pressure peak is below the pressure threshold, the original engine control method is not corrected. This is in accordance with block 20, the fuel amount F is means that is set equal to a predetermined fuel amount F _q ^d by the engine controller. The engine thus operates reliably with much less than the maximum pressure _Pmax, so that the pressure limiter can remain inactive.

On the other hand, when the pressure peak P _peak exceeds the predetermined pressure threshold P _th in the decision block 18, the engine approaches the maximum pressure P _max . According to block 19,
Various approaches can be taken in response to this. P
_peak is compared with the P _th, avoidance reasons not be compared directly with P _max, the pressure peak controller, leave plan ahead the control operation, the excess pressure that may be the large time lag is inevitable correspondingly Should be able to
That's why.

[0027] Already in the block 19 described, the value of the fuel quantity F _q ^d which is predetermined by the engine control unit is compared with the fuel amount F _q ^c which is predetermined by the cascade controller 16. P _peak approaches P _max (that is, P _peak
P _th), when an F _q ^d> F _q ^c, is necessary to protect the engine from excessive pressure, engine operates in accordance with block 21. At that time, the amount of fuel is equal to the amount F _q ^c calculated by P _max cascade controller. However, when the driver applies the brake, F _q ^d drops below F _q ^c ,
Driver regain full control (F · = · F _q ^d in block 20). This is a safety criterion because the amount of fuel injected can never exceed the original fuel supply control fuel amount. In other words, the driver is always controlling the maximum fuel supply.

In block 19, the branch condition can be evaluated using any torque-related variable instead of fuel quantity.

The method of controlling pressure peaks in a cylinder shown in FIG. 3 was tested on a typical 4-cylinder 2 liter diesel engine. The maximum pressure P _max was set to 120 bar and the pressure threshold P _th was set 10 bar below the maximum pressure (ie 110 bar). For comparison, the engine was initially run with the pressure peak controller turned off.

FIG. 4 shows the result of this comparison, in which the pressure peak P _peak exceeds the limit value P _max of 120 bar several times by more than 10 bar. In the upper graph of FIG. 4, the pressure peak in the cylinder is plotted along the vertical axis, and the test time is plotted along the horizontal axis. At the same time, in the lower graph of FIG. 4, the amount of fuel introduced into the cylinder is plotted on the same time axis.

FIG. 5 illustrates the result when the pressure peak controller is switched on and the driver performs the same operation on the engine (same accelerator pedal position). The pressure peak P _peak of the in-cylinder pressure shown in the uppermost graph never exceeds the limit value P _max of 120 bar.

The limit on the amount of fuel introduced by the pressure peak controller, which is for the control performed by the engine controller (see the lower graph of FIG. 4), is shown in the middle of FIG. You can see it in the graph. In addition, the pressure peak controller is deactivated as soon as the driver's demand for fuel is equal to the amount set by the pressure peak controller. Due to the "anti-windup" property,
The value of the fuel quantity set by the pressure peak controller will never be less than the originally intended fuel quantity. The lower graph of FIG. 5 shows the mode in which the fuel supply is controlled (0 is the original engine controller, 1 is the pressure peak controller) on the same time axis as the upper two graphs. I have.

[0033]

As described above, according to the present invention, it is ensured that the internal combustion engine is protected from excessive pressure in the cylinder while reducing the manufacturing cost, Output difference can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic view of a four-cylinder engine to which the method according to the present invention is applied.

FIG. 2 shows six different arrangements of sensors and controllers in which the method according to the invention can be implemented.

FIG. 3 is a flowchart of a method according to the present invention.

FIG. 4 is a graph showing the amount of fuel and the corresponding pressure in a cylinder according to the prior art.

FIG. 5 is a graph showing the fuel quantity, the corresponding pressure in the cylinder and the control mode when the method according to the invention is carried out.

[Explanation of symbols]

 1 Cylinder of internal combustion engine 2 Injection valve 3 Pressure sensor C, C ', C' ', C' '' Pressure peak controller

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 45/00368 F02D 45/00 368T F02P 5/152 F02P 5/15 D 5/153 (72) Inventor Heather Lee, United States 48350, Michigan, Davisburg Ormond Road 5828 F-term (reference) 3G022 DA02 EA00 FA07 GA15 3G084 AA01 BA13 BA15 BA17 DA19 DA24 EA11 FA21 3G301 HA01 HA02 LA00 MA11 MA18 NA03 NA04 NA08 PB03Z PC01Z

Claims (7)

[Claims] At least one cylinder (1) of an internal combustion engine
In the excess pressure measured, a method of protecting an internal combustion engine, when the pressure peak in the cylinder (P _peak) exceeds a predetermined threshold value (P _th), pressure peaks is less than a maximum value (P _max) A method of regulating the introduction of fuel and / or combustion of fuel, as in some embodiments. 2. The method according to claim 1, wherein the amount of fuel supplied, the ignition timing and / or the fuel injection timing are adjusted. 3. The method according to claim 1, wherein adjusting the supplied fuel amount comprises only reducing the fuel amount to be supplied (F _q ^d ) calculated by the engine controller. 4. The method according to claim 1, wherein the pressure is measured for each cylinder bank and / or cylinder of the internal combustion engine. 5. The method according to claim 1, wherein the introduction of fuel and / or the combustion of fuel are separately regulated for each cylinder bank and / or each cylinder of the internal combustion engine. . 6. The introduction of fuel and / or the combustion of fuel is such that the pressure peak in the cylinder (1) will reach the maximum value ( _Pmax ) unless the engine controller sets a relatively low pressure value. A method according to any of the preceding claims, wherein the method is adjusted to be as close as possible. 7. At least one pressure sensor (3) arranged in a cylinder (1) of the internal combustion engine is connected to an input end, and a control device (2) for fuel introduction and / or fuel combustion is provided. Connected to the output end, the pressure peak in the cylinder (P
When _{the peak)} exceeds a predetermined threshold value (P _th), as the pressure peak does not exceed the maximum value (P _max), which is configured to adjust the combustion of the introduction of the fuel and / or fuel, the pressure peak control Apparatus for performing the method according to any of claims 1 to 6, comprising a vessel (C, C ', C ", C"").