JP2000186609A - Combustion pressure detecting device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the occurrence of combustion pressure and knocking and an injector operating state detectable on the basis of an output signal out of a combustion sensor. SOLUTION: An electronic control unit 8 is provided with an LPF 82, a BPF 84, an HPF 86 and a CPU 88. An output signal of a combustion pressure sensor 72 consisting of a piezoelectric element installed in the mounting part of a glow plug is processed by those of LPF 82, BPF 84 and HPF 86 in the electronic control unit 8. The central processing unit 88 senses the extent of combustion pressure in a combustion chamber on the basis of the output signal of the LPF 82, and also the occurrence of knocking on the basis of the output signal of the BPF 84. In addition, the central processing unit 88 diagnoses the operation of each injector and the normality of fuel injection pressure on the basis of the output signal of the HPF 86.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a combustion pressure detecting device for an internal combustion engine, and more particularly to a combustion pressure detecting device for an internal combustion engine that detects a knock signal and an injector operating state signal in addition to the combustion pressure.

[0002]

2. Description of the Related Art With the development of electronic technology in recent years, various electronic control technologies have been used for internal combustion engines. The electronic control technology is applied to ignition timing control, knock control, fuel injection control, diagnosis, and the like of an internal combustion engine. In knock control, the ignition timing and the fuel injection timing are adjusted according to the degree of knock detected by a knock sensor provided in the internal combustion engine. For example, in a gasoline engine, when knock is detected, a retard is performed in accordance with the knock intensity, and if no knock continues, the ignition timing is gradually advanced to the knock limit. By appropriately performing knock control, improvement in combustion efficiency and output performance of the internal combustion engine and the like are achieved.

In diagnosis, an ECU (Ele) is used.
Based on the input signal to the ctronic control unit), the presence / absence of a failure of a sensor, an actuator or the like is diagnosed. For example, in diagnosis related to an injector, the operation of the injector and the normality of the fuel injection pressure value are diagnosed based on an injector operation state signal that conveys the operation state of the injector.

Further, as a fuel injection control method, conventionally, a combustion pressure in a cylinder is detected based on a signal generated by a combustion pressure sensor provided in a mounting portion such as an injector or a glow plug in an internal combustion engine. There is widely known a method of controlling the amount of fuel injected by an injector according to the combustion pressure of a fuel. For example, Japanese Patent Application Laid-Open No. 9-68082 discloses a fuel injection amount control device in which a washer-like combustion pressure sensor made of a piezoelectric element is provided on a screw-in type mounting portion of a glow plug of a diesel engine.

A control unit constituting the fuel injection amount control device calculates the actual torque of the diesel engine based on the combustion pressure detected by the combustion pressure sensor, and further calculates the required torque of the diesel engine from the accelerator pedal depression amount and the engine speed. Is calculated. Then, the control unit increases or decreases the fuel injection amount from the injector until the calculated actual torque of the diesel engine is equal to the required torque. In a diesel engine provided with such a fuel injection amount control device, a required torque can always be obtained, so that it is possible to improve drivability and fuel efficiency, reduce exhaust gas, and the like.

[0006]

However, in the above-described conventional fuel injection amount control device, knock control based on the signal output from the combustion pressure sensor and diagnosis regarding the injector cannot be realized. Further, in addition to the configuration of the above-described conventional fuel injection amount control device, a component such as a knock sensor is newly provided in the vicinity of the combustion chamber so that knock control and diagnosis regarding the injector can be performed. This leads to an increase in the density of the vicinity of the chamber, which leads to an increase in cost and weight of the internal combustion engine.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and provides an internal combustion engine capable of detecting not only combustion pressure, but also occurrence of knock and injector operating state, based on an output signal of a combustion pressure sensor. It is an object to provide a combustion pressure detecting device.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a combustion pressure sensor for outputting a signal including information on a combustion pressure in an internal combustion engine and a combustion pressure sensor different from an output signal of the combustion pressure sensor. First, second, and third filters for extracting first, second, and third frequency components, respectively; combustion pressure detecting means for detecting a combustion pressure based on the first frequency component; This is achieved by a combustion pressure detection device for an internal combustion engine having knock detection means for detecting occurrence of knock based on a frequency component and injector operation state detection means for detecting an injector operation state based on the third frequency component. .

In general, a signal indicating knock of the internal combustion engine and a signal indicating the operating state of the injector are superimposed on a signal corresponding to the combustion pressure in the output signal of the combustion pressure sensor. These signals have different frequency components from each other.
Therefore, according to the present invention, the first filter extracts the first frequency component corresponding to the combustion pressure signal, the second filter extracts the second frequency component corresponding to the knock signal, and the third filter extracts the second frequency component corresponding to the knock signal. By extracting the third frequency component corresponding to the injector operation state signal, it is possible to detect the combustion pressure in the internal combustion engine, the occurrence of knock, and the injector operation state.

[0010]

FIG. 1 is a diagram showing the main components of a combustion pressure detecting device provided in an internal combustion engine 1. Internal combustion engine 1
Is a four-cylinder diesel engine. As shown in FIG. 1, the internal combustion engine 1 includes an internal combustion engine main body 2. The internal combustion engine body 2 has four cylinders 10, 20, 30, 40
Having. In the cylinders 10, 20, 30, 40, injectors 12, 22, 32, 42 and glow plugs 14, 24, 34, 44 are disposed, respectively.

The fuel pump 4 is connected to the injectors 12, 22, 32, 42 via the delivery pipe 3, respectively. Further, a low-pressure pump 6 is connected to the fuel pump 4 via a fuel supply pipe 5. The low-pressure pump 6 pumps up the fuel stored in the fuel tank 7 during operation of the internal combustion engine 1 and supplies the fuel to the fuel pump 4 at a predetermined pressure. The fuel pump 4 pressurizes the fuel supplied from the low-pressure pump 6 and sends it to the internal combustion engine body 2 side. The high-pressure fuel pumped by the fuel pump 4 is
Cylinders 10, 20, 30, through the delivery pipe 3
The fuel is supplied to the injectors 12, 22, 32, and 42 in 40.

The fuel pump 4, the injectors 12, 22,
32, 42 and glow plugs 14, 24, 34, 44
Are electrically connected to an electronic control unit 8 (hereinafter, referred to as ECU 8). In addition, various sensors (not shown) that detect the operating state of the internal combustion engine 1 such as a rotation speed sensor and an accelerator opening sensor are connected to the ECU 8.
The ECU 8 detects the operating state of the internal combustion engine 1 based on the output signals of these sensors, and calculates the optimum fuel injection pressure according to the detected operating state. And ECU
8 is the calculated optimum fuel injection pressure and injector 12,
A drive signal is supplied to the fuel pump 4 by comparing the fuel injection pressure of the fuel actually injected from the fuel injection pump 22, 22, 32, 42. The fuel pump 4 increases / decreases the amount of fuel pumped in accordance with the drive signal supplied from the ECU 8. As a result, during operation of the internal combustion engine 1, the pressure of the fuel injected from the injectors 12, 22, 32, 42 is always maintained at an optimum pressure for the operation.

The ECU 8 includes injectors 12, 2
2, 32 and 42 are supplied with drive signals. Injector 1
When a drive signal is supplied from the ECU 8, the fuel injection holes 2, 22, 32, and 42 open fuel injection holes provided at their ends. As described above, the injectors 12, 22, 3
High-pressure fuel is supplied to the fuel tanks 2 and 42 from the fuel pump 4 via the delivery pipe 3. Therefore, when the fuel injection holes of the injectors 12, 22, 32, and 42 are opened, the high-pressure fuel is supplied to the cylinders 10, 20, 30, 40.
Injected into.

The ECU 8 includes glow plugs 14, 2
4, 34 and 44 are supplied with drive signals. Glow plug 1
4, 24, 34 and 44 heat the combustion chamber in order to enhance the combustibility of fuel when the internal combustion engine 1 is started. ECU8
Indicates that after the ignition switch of the internal combustion engine 1 is switched from the off state to the on state, the glow plugs 14, 2
A predetermined current is allowed to flow through 4, 34 and 44 for a predetermined time. The glow plug 14,
The heating wires provided inside the distal ends of 24, 34 and 44 generate heat, and the combustion chamber is heated. The ignitability of the fuel is improved by heating the fuel chamber. Further, a combustion pressure sensor, which will be described later, is provided at a mounting portion of the cylinder 10 for the glow plug 14.

Next, the structure of the cylinder 10 and its surroundings will be described. FIG. 2 is a diagram showing the structure of the cylinder 10 provided in the internal combustion engine main body 2 and its surroundings. As shown in FIG. 2, the internal combustion engine main body 2 includes a cylinder block 50 and a cylinder head 52. A piston 54 is provided in the cylinder 10 provided inside the cylinder block 50. The piston 54 reciprocates in the cylinder 10 in the axial direction. Piston 5
The compression rings 56 and 58 and the oil ring 60 are mounted around the periphery of the compression ring 4. The cylinder 10
A combustion chamber 62 is formed in a portion surrounded by the inner peripheral surface of the piston, the upper surface of the piston 54, and the bottom surface of the cylinder head 52. A cylindrical main combustion chamber 64 is formed above the piston 54, as shown by a broken line in FIG. The main combustion chamber 64 forms a part of the combustion chamber 62.

The compression rings 56 and 58 close a gap between the inner peripheral surface of the cylinder 10 and the piston 54. As a result, the airtightness of the combustion chamber 62 is improved.
When the piston 54 descends, the oil ring 60 collects excess lubricating oil attached to the inner peripheral surface of the cylinder 10 and returns the collected lubricating oil to an oil pan (not shown). The compression rings 56 and 58 and the oil ring 60 further transfer heat of the piston 54 to the cylinder 1.
It also has the function of radiating heat to the zero side.

The cylinder head 52 has an injector 1
2 are provided. The injector 12 is disposed such that its tip is exposed to the combustion chamber 62. A fuel injection hole 66 for injecting fuel into the combustion chamber 62 is provided at the tip of the injector 12. The glow plug 14 is also provided on the cylinder head 52. The glow plug 14 has a heating section 68 and a shaft section 70. The shaft part 70 of the glow plug 14 is fitted into the cylinder head 52 such that the heat generating part 68 is exposed to the combustion chamber 32. The heat generating portion 68 includes a built-in nichrome wire that generates heat in accordance with the amount of supplied power. The shaft 70 has a built-in power transmission line that is electrically connected to the nichrome wire in the heating section 68.

A washer-shaped combustion pressure sensor 72 is provided at a portion where the glow plug 14 is attached to the cylinder head 52. The combustion pressure sensor 72 is formed of a piezoelectric element, and outputs a signal corresponding to a pressure detected by the piezoelectric element by a piezoresistance effect. The output signal of the combustion pressure sensor 72 includes a combustion pressure signal (about 5 kHz) having a predetermined frequency different from each other, a knock signal (about 1 to 3 kHz), and an injector operation state signal (about 10 kHz).
Then, the output signal of the combustion pressure sensor 72 is supplied to the ECU 8. In the ECU 8, the output signal of the combustion pressure sensor 72 is processed by a filter described later,
The combustion pressure signal, the knock signal, and the injector operating state signal are separately detected.

The ECU 8 detects the combustion pressure in the combustion chamber 62 based on the combustion pressure signal and adjusts the amount of fuel injected from the injector 12. Further, the ECU 8 detects whether knock has occurred based on the knock signal, and adjusts the timing at which fuel is injected from the injector 12. Further, the ECU 8 performs the following based on the injector operation state signal.
Diagnosing the operation of the injector and the normality of the fuel injection pressure value.

The cylinders 20, 30, and 40 have the same configuration as the cylinder 10. In addition, injector 2
2, 32, and 42 have the same configuration as the injector 12. FIG. 3 is a diagram showing a part of a circuit configuration in the ECU 8. As shown in FIG. 3, the ECU 8 controls the LPF (Low Pass
Filter) 82, BPF (BandPass Filter) 84, HPF
(High Pass Filter) 86 and CPU (Central Processin)
g Unit) 88 and the like. The LPF 82 is a filter that extracts a low-frequency signal corresponding to the combustion pressure signal. The BPF 84 is a filter that extracts a signal having a frequency corresponding to the knock signal. Further, the HPF 86 is a filter for extracting a signal having a frequency corresponding to the injector operating state signal.

The combustion pressure signal extracted by the LPF 82 is supplied to the CPU 88. The CPU 88 detects the combustion pressure in the combustion chamber 62 based on the combustion pressure signal. Then, the CPU 88 calculates an optimal fuel injection amount based on the detected combustion pressure, and causes the injector 12 to inject the calculated amount of fuel. In this way, the ECU 8 can control the air-fuel ratio to be as lean as possible to the limit of the allowable torque fluctuation of the internal combustion engine 1 based on the detected combustion pressure. By controlling the air-fuel ratio to be lean, reduction of NOx in the exhaust gas is realized.

FIG. 4 is a diagram showing the operation of the ECU 8 for injecting fuel.
An injection signal given to the injector 12 from
FIG. 7 is a diagram showing a time change of an output signal of the BPF 84. FIG.
, The waveform of the output signal of the BPF 84 after the injection signal is given to the injector 12 indicates that a knock signal of a predetermined frequency (about 2.5 kHz) is included.

As described above, the BPF 84 is a filter for extracting a signal having a frequency corresponding to the knock signal. For this reason, the knock signal included in the output signal of the combustion pressure sensor 72 is extracted by the BPF 84 as shown in FIG. The CPU 88 detects the occurrence of knock in the combustion chamber 62 based on the knock signal. Then, the CPU 88 performs optimal advance control of the fuel injection timing based on the detected knock signal.

As shown in FIG. 2, the combustion pressure sensor 72 is provided immediately above the cylinder 10 of the cylinder head 52. Therefore, according to the combustion pressure detecting device of the present embodiment, the knock signal generated in the cylinder 10 can be detected with high accuracy. The frequency range processed by the BPF 84 is optimally set so that noise components such as seating vibration of a valve included in the output signal of the burning pressure sensor 72 can be removed. Therefore, the knock signal is detected with higher accuracy.

When the knock signal is detected with high accuracy, it is possible to control the advance of the fuel injection timing with high accuracy. As a result,
The output of the internal combustion engine 1 can be taken out more efficiently, so that the output efficiency of the internal combustion engine 1 can be improved, the fuel efficiency can be reduced, and the like. FIG. 5 is a diagram showing a change over time of the injection signal, the output signal of the HPF 86, and the combustion pressure in the combustion chamber 62 given to the injector 12 during one cycle of the operation of the internal combustion engine 1.

FIG. 6 shows the injection signal supplied from the ECU 8 to the injector 12, the drive current flowing through the injector 12, the output signal supplied from the combustion pressure sensor 72 to the HPF 86, and the combustion pressure in the combustion chamber 62. It is a figure showing a time change. The waveform of the injection signal shown in FIG.
FIG. 6 is an enlarged view of the waveform near the peak of the injection signal shown in FIG. 5.

As shown in FIG. 6, the injector 12
The pilot injection for injecting the fuel twice is performed continuously. In this method, after a small amount of fuel is injected first, the fuel injection is interrupted once, and when the first fuel is ignited, full-scale main injection is performed. by this,
Fuel combustion during main injection is ensured, and diesel knock is prevented. Further, NOx in the exhaust gas is reduced by reducing the premixed combustion.

The combustion pressure sensor 72 is provided on the internal combustion engine main body 2 having the cylinders 10, 20, 30, and 40. Therefore, the output signal of the combustion pressure sensor 72 includes an injector operation state signal generated in accordance with the fuel injection operation of the injectors 12, 22, 32, and 42 provided in the cylinders 10, 20, 30, and 40, respectively. . Here, the HPF 86 is a filter for extracting a signal having a frequency corresponding to the injector operation state signal. For this reason, the injector operation state signal included in the output signal of the combustion pressure sensor 72 is extracted by the HPF 86,
It is supplied to PU88. Waveforms 16 and 26 in FIG.
36, 46 are injectors 12, 22, 3, respectively.
5 shows waveforms of injector operation state signals corresponding to Nos. 2 and 42. Here, as shown in FIG. 5, the maximum amplitude value of the operating state signal of each injector is Vp.

FIG. 7 is a diagram showing the relationship between the voltage Vp [V] of the injector operating state signal and the injection pressure P [MPa] of the fuel injected from the injector, which have been clarified by experiments. As shown in FIG. 7, the voltage Vp and the injection pressure P are generally in a proportional relationship. Therefore, the CPU 88
Based on the voltage Vp of the injector operating state signal for each of the injectors 12, 22, 32, 42,
It is possible to execute a diagnosis determination process for determining whether or not the actual fuel injection pressure P at 22, 32, 42 has reached a predetermined value.

FIG. 8 is a flowchart showing a routine executed by the CPU 88 in the ECU 8. When the routine shown in FIG. 8 is started, first, in step 100, it is determined whether or not the injector 12 in the cylinder 10 is injecting fuel. The process of step 100 is
For example, the injection is performed in the order of the injectors 12, 22, 32, and 42. The determination process in step 100 is performed based on, for example, whether a fuel injection signal is given to the injector 12 or the like. As a result, the injector 1
If it is determined that 2 is not injecting fuel, then
The process of step 102 is performed. Step 1
At 00, if it is determined that the injector 12 is injecting fuel, then the process of step 104 is executed.

In step 102, the presence / absence of an injector for which a diagnosis determination process has not been performed is searched. Step 1
In 02, when there is an injector for which the diagnosis determination process has not been performed, the process of step 100 is executed for the injector for which the diagnosis determination process has not been performed. On the other hand, if there is no injector for which the diagnosis determination process has not been performed, the current routine ends.

In step 104, based on the output signal of the HPF 86, the voltage V of the operating state signal of the injector 12 is
p is detected. Then, when the processing of step 104 is completed, the processing of step 106 is executed next. In step 106, a correction voltage Vp 'corresponding to the actual fuel injection pressure P of the injector 12 is calculated based on the voltage Vp detected in step 104. The correction voltage Vp ′ is calculated by multiplying the voltage Vp by a correction coefficient K1 preset for the injector 12. Similarly, the correction voltage Vp 'of the injectors 22, 32, 42 is calculated by multiplying the correction coefficients K2, K3, K4 preset for the injectors 22, 32, 42 by the voltage Vp of each injector. . When the process of step 106 ends, the process of step 108 is executed next.

In step 108, it is determined whether or not the injector 12 is operating normally. This determination is based on the correction voltage Vp ′ and the preset operation determination value Kin.
j. In step 108, if Vp '> Kinj is not satisfied, the injector 1
2, the fuel injection pressure P is extremely low, it is determined that the injector 12 is not operating normally, and in the subsequent step 110, the operation of the internal combustion engine 1 is stopped. Then, the current routine ends. On the other hand, if Vp '> Kinj is satisfied in step 108, it is determined that the injector 12 is operating normally, and then the process of step 112 is executed.

In step 112, it is determined whether the fuel injection pressure P of the injector 12 is normal. This determination is made by comparing the correction voltage Vp 'of the injector 12 with a preset injection pressure determination value Kp.
If Vp '> Kp is not satisfied in step 112, it is determined that the injection pressure P of the injector 12 is in an abnormal operation state in which the injection pressure P has not reached the predetermined pressure, and the subsequent step 1
At 10, the operation of the internal combustion engine 1 is stopped. And
This routine ends. On the other hand, if it is determined in step 112 that Vp ′> Kp, it is determined that the injector 12 is injecting fuel at a normal pressure.
Then, for example, the process of step 102 is performed on the injector 22.

As described above, the combustion pressure detecting device of the present invention provides the correction coefficients K1, K2, K3, K4 for each injector.
And an operation determination value Ki and an injection pressure determination value Kp. Then, the injector operation state signal detected by the combustion pressure sensor 72, the correction coefficients K1, K2, K3, K4,
Based on the operation determination value Ki and the injection pressure determination value Kp, the diagnosis determination process of all the injectors 12, 22, 32, and 42 can be performed. Therefore, in the present combustion pressure detection device, for example, only one combustion pressure sensor 72 may be disposed on the cylinder 10. As a result, overcrowding near the combustion chamber due to the provision of extra parts is prevented, and the cost and weight of the internal combustion engine 1 can be reduced.

The internal combustion engine 1 is not limited to a four-cylinder diesel engine, but may be a six-cylinder diesel engine, for example. Further, the principle of the present invention is not limited to a diesel engine but may be applied to a gasoline engine. When the combustion pressure detecting device of the present invention is applied to a gasoline engine, 6
Combustion pressure sensor 72 by BPF processing of about 9 kHz
A knock signal can be detected from the output signal of.

In the above embodiment, the "combustion pressure signal"
The “knock signal” and the “injector operating state signal” correspond to the “first frequency component”, the “second frequency component”, and the “third frequency component”, respectively, in the claims. “LPF82”, “BPF8”
"4" and "HPF86" correspond to the "first filter", the "second filter", and the "third filter" in the claims, respectively. Further, the processing in which the CPU 88 detects the combustion pressure based on the output signal of the LPF 82 corresponds to “combustion pressure detecting means” described in the claims.
The processing in which the CPU 88 detects the occurrence of knocking based on the output signal of the CPU 84 corresponds to “knock detecting means” described in the claims.
The process of detecting the injector operation state signal by the device 8 corresponds to “injector operation state detection means” described in the claims.

[0038]

As described above, according to the first aspect of the present invention, the provision of new components such as a sensor does not cause overcrowding in the vicinity of the combustion chamber or increase in cost and weight of the internal combustion engine. Based on the output signal of the pressure sensor, it is possible to detect the combustion pressure of the internal combustion engine, the occurrence of knock, and the operating state of the injector.

[Brief description of the drawings]

FIG. 1 is a diagram showing main components of a combustion pressure detecting device according to the present invention.

FIG. 2 is a diagram showing a cylinder provided in the internal combustion engine body and a structure around the cylinder.

FIG. 3 is a diagram showing a part of a circuit configuration in an ECU.

FIG. 4 shows the injection signal and BP given to the injector.
FIG. 7 is a diagram showing a time change of an output signal of F.

FIG. 5 is a diagram showing a time change of an injection signal, an HPF output signal, and a combustion pressure in a combustion chamber given to an injector during one cycle of operation of the internal combustion engine.

FIG. 6 is a diagram showing an injection signal given to an injector, a drive current given to the injector, an output signal of a fuel HPF, and a time change of a combustion pressure in a combustion chamber.

FIG. 7 is a diagram showing a relationship between a voltage Vp of an injector operation state signal and an injection pressure P of fuel injected from the injector.

FIG. 8 is a flowchart illustrating a routine executed by a CPU.

[Explanation of symbols]

 Reference Signs List 1 internal combustion engine 2 internal combustion engine main body 8 ECU 10, 20, 30, 40 cylinder 12, 22, 32, 42 injector 14, 24, 34, 44 glow plug 50 cylinder block 52 cylinder head 62 combustion chamber 72 combustion pressure sensor 82 LPF 84 BPF 86 HPF 88 CPU

Claims (1)

[Claims] 1. A combustion pressure sensor for outputting a signal containing information on combustion pressure in an internal combustion engine, and a first, second and third frequency component different from each other extracted from an output signal of the combustion pressure sensor. , Second
And a third filter; a combustion pressure detection means for detecting a combustion pressure based on the first frequency component; a knock detection means for detecting the occurrence of knock based on the second frequency component; And an injector operating state detecting means for detecting an injector operating state based on a frequency component of the combustion pressure.