JP2963871B2 - Internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an internal combustion engine.
In particular, the present invention relates to an internal combustion engine having an oxygen detection cell or a lambda cell in an exhaust duct from the engine.

[0002]

BACKGROUND OF THE INVENTION Internal combustion engines are used in combined heat and power systems or to drive vehicles. The engine may be a reciprocating engine. The fuel for starting the engine may be a fuel gas, for example natural gas. It is known to provide a catalytic converter device, for example a three-way catalytic converter, in the exhaust duct to reduce harmful emissions. An oxygen sensing cell or lambda cell with zirconia is provided in the duct to provide an electrical output signal that is a function of the amount of oxygen in the exhaust gas. The amount of oxygen in the exhaust gas is a function of the ratio of combustion air to fuel supplied to the engine (hereinafter referred to as the air / fuel ratio). The ratio of combustion air (supplied to the engine) to the normal composition air demand is defined as lambda ratio or lambda. It is desirable to maintain the air / fuel ratio substantially at a predetermined value such that the value of lambda is substantially equal to one so that the nature of the combustion products of the exhaust duct internal combustion type is not detrimental to the performance of the catalytic converter device. Thus, it is known to provide a controller for changing the fuel supply to maintain the air / fuel ratio substantially at a desired value in response to changes in the output signal from the lambda cell.

[0003] Alternatively, it is known to operate internal combustion engines at high levels of excess combustion air, known as fuel efficient operation, to reduce harmful emissions. However, if the excess air exceeds a certain level, poor combustion may occur, resulting in misfire of the fuel mixture, reduction in engine power, and damage to the engine and equipment driven by the engine. Thus, it is necessary to maintain the air / fuel ratio substantially at a predetermined value to ensure the required emission levels in the exhaust gas without causing misfire. The lambda cell is used for this purpose and supplies a signal to a controller that controls the air / fuel ratio. Lambda cells with zirconia do not work at ambient temperature. Lambda cells comprise a heating device, for example a metal heating coil, which is electrically operated and has a resistance which increases with temperature. The metal is preferably platinum. The ideal is to maintain the lambda cell at an operating temperature that is relatively high and cannot be relied on by the temperature of the exhaust gas passing through the sensing element of the lambda cell. Thus, the temperature of the lambda cell can be kept high regardless of the exhaust gas temperature. This was attempted by electrically operating the heating device. Unfortunately, manufacturing tolerances are slightly different for each lambda cell, and uncontrolled power supply is not suitable to produce adequate heating of all cells. This creates difficulty when mass producing internal combustion engines or when lambda cells need to be replaced. This is because the electrical output signal from the zirconia lambda cell depends on temperature,
Also, it changes again for each cell (see FIG. 5). A change in cell temperature will cause a change in the millivolt electrical output signal, even though the cell is observing exactly the same amount of oxygen. Thus, if the lambda cell is operated at the wrong temperature, or if a different cell is operated at the same temperature, the controller will receive an electrical output signal representing an amount of oxygen that is different from the amount of oxygen that the cell is actually exposed to. As a result, the controller adjusts the air / fuel ratio to an incorrect value that may reduce the effectiveness of the harmful emission reducing means, whether the harmful emission reducing means comprises a catalytic converter or fuel efficient operation. will do. Even with good fuel economy, unacceptable engine operation may occur.

It is an object of the present invention to provide any lambda cell (having an electric heating device consisting of an electric heating resistor having a resistance value that varies as a function of temperature) used in the exhaust duct, the cell being observed by the cell. It is an object of the present invention to provide an internal combustion engine that can be automatically heated to a correct temperature so as to generate an electric output having a value that accurately reflects the amount of oxygen generated.

[0005]

According to the present invention, an oxygen sensing cell or lambda cell having an exhaust duct and an electrical heating device provided in the duct and having a resistance value that varies as a function of temperature, comprises: A control device for powering the heating device so as to maintain the heating device at a substantially constant desired operating temperature having a predetermined operating resistance value RH1, wherein the control device comprises a resistance value of the heating device. And at least one reference value, and for changing power in response to the comparison to maintain the cell at the desired operating temperature, the reference value comprising: An internal combustion engine which is obtained from the operation of the lambda cell while the cell is emitting an electrical signal having a value which is substantially a predetermined reference value. To provide. The reference gas may be ambient atmospheric air. The present invention will now be further described, by way of example, with reference to the accompanying drawings.

[0006]

1 to 3 and in particular with reference to FIG. 1, a reciprocating internal combustion engine 2 has an engine unit 4 with an exhaust duct or exhaust pipe 6 having a catalytic converter 8. The exhaust pipe 6 is fitted with an oxygen sensor or lambda cell 10 upstream of the catalytic converter 8, which sends a voltage signal via a signal path 12 to a control device 14 with an electronic circuit. Lambda cell 10 is of the zirconia (zirconium oxide) type and includes an electric heater or coil 16, for example, a platinum coil having an electrical resistance that increases with increasing temperature. The lambda cell is preferably of the type available from Bosch. Electric heater 1
The power that energizes 6 as shown in FIG.
1, 182. The engine 2 also has a combustion air and fuel mixing regulator or carburetor 20, the combustion air is supplied to the carburetor 20 as indicated by the arrow 22, and a fuel gas, for example natural gas, is supplied to the duct 24 from a suitable supply. To the carburetor 20 and the duct 24 converts the signal, for example, an electrical signal on a signal path 28 generated by the controller 14 in response to a signal received by the controller 14 from the path 12 from the lambda cell 10. It has a gas pressure control valve 26 that is electrically opened and closed in response. In response to the signal from the cell 10, the controller operates the valve 26 in a known manner to maintain the combustion air to fuel gas ratio supplied to the engine unit 4 at a substantially predetermined desired constant value.

With particular reference now to FIGS. 2 and 3, the controller 14 comprises a controller 30 having an electrical bridge 32, one of the arms of the electrical bridge having a cell heater 16 attached thereto.
There is. The bridge 32 is grounded, for example, by being connected to the exhaust pipe 6 at 34. On the other arm of the bridge is a constant resistor 36 and a control resistor 40 which is variable and has a value which is set to a predetermined value by a microcontroller 42 with a computer device. If the resistance values of the constant resistors 36 and 38 are RA and RB, respectively, the bridge 32

[0008]

[Outside 1] Is zero. Here, RC1 (controllability) is the control resistance 40
RH1 is the operating resistance value of the electric heater 16 when the bridge is zero.

[0009]

[Outside 2] Is found to be at zero. A heater / control circuit 44 outputs a control signal to a signal path 46.

[0010] Until the resistance of the heater reaches the operating value RH1, a DC electrical output is generated which activates the heater 16 having a resistance which increases as the temperature of the heater increases. When the microcontroller 42 observes the zero point, the power output from the heater control circuit 44 is maintained substantially constant, causing the heater 16 to operate at the desired operating temperature at which the resistance of the heater 16 reaches the operating value RH1. T
1 (this passes through the sensing element of lambda cell 10, exhaust pipe 6
The temperature of the exhaust gas inside is kept above). Now, if the temperature of the heater 16 changes from the desired operation value T1,
If the resistance is increased or decreased, then a departure from zero is observed by the microcontroller 42, which causes the control circuit 44 to decrease or increase its power output to change the power output. Let the heater 1
The resistance of 6 is restored to the operating value RH1 (and thus the zero point is restored), so that the temperature of the cell 10 returns to the desired operating value T1. The DC power output from the heater control circuit 44 can be changed by changing the DC voltage or by generating a power output or current in the form of a square wave and changing the mark / space ratio. .

When the lambda cell 10 is operating at a desired operating temperature T1 corresponding to the heater resistance RH1,
The cell provides an electrical output signal that is substantially accurate for the amount of oxygen observed by the cell, and thus the controller 14 operates the valve 26 to determine the combustion air to fuel ratio supplied to the engine unit 4. It can be maintained at a substantially desired constant predetermined value. It has been found that the present invention allows a lambda cell 10 of the above type to be easily used in the control unit 14 if the control unit 30 is properly calibrated. This is done by operating the lambda cell 10 in ordinary or ambient atmospheric air outside the exhaust pipe 6 and with the microcontroller 42 operating in a calibration mode. The calibration mode may be automatically selected in response to a signal to the microcontroller via signal path 48. The amount of oxygen in ordinary air is assumed to be constant at about 20.9% by volume. Under the control of the microcontroller 42, the heater control circuit 44 is operated to operate the cell heater 16, and the temperature of the lambda cell 10 is increased until the voltage of the output signal from the lambda cell reaches a predetermined reference value OV. When the microcontroller 42 observes the appearance of the voltage of the reference value OV, the microcontroller 4
2 automatically operates to change the value of the control resistor 40 and the power supplied to the bridge 32 by the heater control circuit 44, until the lambda cell continues to output an output voltage signal of the reference value OV. Observes the zero point of the bridge. At that zero point, the control resistor 40 has a resistance value RC2 (calibration value) and the resistance of the heater 16 has a value RH
2, which determines that the lambda cell 10 operates in air at a temperature T2 that produces an output reference voltage OV. The microcontroller 42 can record the calibration value RC2 of the control resistor 40. The microcontroller 42 generates data defining an actuation function or relationship that correlates a particular calibration value RC2 of the control resistor 40 to a particular control value RC1 of the control resistor when the lambda cell is to monitor exhaust gas. Prepare. The actuation function is a linear function of the following type:

RC2 = A × RC1 + C (2) where A and C are constants. Once the specific calibration value RC2 is obtained, the microcontroller 42
When the control signal RC1 is received, the control value RC1 of the correlation function is derived, and the microcontroller is automatically switched to the operation mode. In this operation mode, the microcontroller changes the value of the control resistor 40 to the control value RC1, and When it is positioned to observe the exhaust gas passing along the exhaust pipe 6, it is ready to receive a signal from the lambda cell 10. An example of the above actuation function or relationship is represented graphically in FIG. Correlate the resistance for RC2 with the control resistance for RC1, and
For any calibration value for RC2, there is a specific value for RC1. The microcontroller 42 determines, for any calibration value for RC2,
The control value can be calculated for 1 or the value for RC1 can be obtained from a look-up table previously derived. Referring to equation (2) above, in the actuation function represented in FIG. 7, A is about 0.926 and C is about 1.221.
To determine an actuation function or relationship that correlates the resistance value RC2 with the respective control resistance value RC1, a number of lambda cells 10 are mounted at the same longitudinal position along the same exhaust pipe 6 and each cell is its own respective one. Connect to bridge circuit 32. The engine is operated to send the exhaust gas along the exhaust pipe, and the power supplied to the heater 16 of each cell 10 is changed by changing the value of the control resistor 40, so that the output voltage from the cell is substantially all. The operating temperature of the cell is controlled so as to be the same, that is, the voltage V1. Now, the control resistance 4 of each bridge 32
Observe a value of 0. This is the control value RC for each cell.
Give 1 Then, placing all lambda cells 10 in air, applying power to each cell and reheating the cells, changing the power by changing the respective control resistors 40 until all cells have the same predetermined output voltage OV. . Now, the value of the control resistor 40 of each bridge 32 is set to the control value RC for each cell.
2 and each of the values for RC2 is
By plotting against the corresponding value for RC1, by way of example, a relationship as shown in FIG. 7 can be obtained, which, as described above, is believed to apply to lambda cells.

Cell 1 operating in air (for calibration purposes)
For 0, the predetermined output voltage reference value OV can be determined by trial and error as follows. The procedure described in the previous section may be implemented by arbitrarily choosing a value for the output voltage OV, for example,-
Performed using 10 mV. The correlation values of RC1 and RC2 were plotted and the degree to which a linear relationship could be used for the correlation was recorded. Further select the voltage value for OV,
A test was performed to determine another value for RC2 for each cell. RC for RC2 for each selected output voltage value
1 was further plotted. By examining the degree of correlation and the repetition of the output voltage value OV, a predetermined value OV is obtained for an output voltage at which the completion of a linear correlation between RC1 and RC2 is deemed acceptable. Predetermined output voltage reference value O
We believe that the preferred value for V is substantially -11.1 millivolts (mV). Referring to FIGS. 4 and 6,
The output of the lambda cell is a measure of the oxygen in the exhaust gas when the engine is operating with a rich fuel mixture (lambda less than 1) and a lean fuel mixture (lambda greater than 1). When the fuel mixture is rich, at higher operating temperatures of the lambda cell, the voltage output is smaller for the same value of lambda. But if lambda is equal to or greater than 1,
The situation is reversed: when the fuel mixture is lean, at the higher operating temperature of the lambda cell, the voltage output is larger for the same value of lambda. As described above, by using the output reference voltage OV to calibrate the bridge 32 to work with any given lambda cell 10 of the type described above that measures oxygen in the exhaust gas, Operating temperature is also a desired temperature T appropriate for the cell.
1, the voltage output from the cell accurately reflects the rich or lean mixture of fuel and air supplied to the engine unit to the amount of oxygen present in the exhaust.

If desired, control unit 30 of FIGS.
Alternatively, the control device 52 of FIG. 8 may be used. The heater resistor 16 has a specific operating value RH1 at the desired operating temperature T1 of the lambda cell. To maintain the lambda cell at the operating temperature T1, the resistance of the heater is maintained at the operating resistance RH1. Microcontroller 42 controls heater control circuit 44 so that the power supplied to heater 16 is sufficient to maintain the heater resistance substantially at operating value RH1. The heater control circuit 44 can observe the value of the DC voltage before and after the heater 16 and the value of the current supplied to the heater, and can determine these values by the signals of the signal paths 54 and 56 by the microcontroller. 42, so that the microcontroller can calculate the resistance of the heater 16 according to Ohm's law. If the value changes from the desired operation value RH1, the power supplied to the heater 16 is changed to restore the heater resistance to the desired value RH1.

Controller 52 responds to the signal on path 48
When calibrated and the lambda cell is in air, the microcontroller 42 controls the operation of the heater control circuit 44 so that a voltage signal having a predetermined reference value OV appears on the signal path 12 from the lambda cell. Change the DC voltage supplied to the heater control circuit until observed by the microcontroller. at the time,
Microcontroller 42 calculates the resistance RH2 of heater 16 using the values of the voltage and current signals on paths 54 and 56 from heater control circuit 44. The microcontroller 42 records the calibration resistance value RH2, and when switched to the operating mode by the signal on path 50,
The microcontroller refers to an actuation function or relationship, for example as represented in FIG. 9, which determines a particular actuation resistance value RH1 for the heater resistance correlated with the recorded value RH2. Provided for Thus, when the lambda cell is observing the exhaust gas, the microcontroller 42 compares the resistance of the heater 16 with the desired operating value RH1, activates the heater control circuit 44, and the heater 16 It has a resistance value RH1. When the controller 52 is used for the controller 14 (FIG. 1), a controller similar to the controller 30 with the bridge 32 is used to initially find the predetermined reference voltage value OV as described above. Is also good. The controller 30 with the bridge 32 is also used to determine the actuation function or relationship represented in FIG. 9, so that when the relationship of FIG. 7 is determined as described above, instead of RC2. The calibration value RH2 can simply be used (since these values are the same) and also the operating value RH instead of the value RC1
One can be used (since these values are also the same), and hence the working relationship represented by the graph of FIG. 9 can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an internal combustion engine formed according to the present invention.

2 schematically shows a control device included in the engine of FIG. 1 for maintaining a lambda cell at a predetermined temperature.

3 shows the engine of FIG. 1 visually representing the control device of FIG. 2;

FIG. 4 shows that the cells were heated at 540 ° C., 563 ° C., 608 ° C., 6
Operating at 65 ° C. and 715 ° C., when the combustion air-fuel mixture supplied to the engine is rich, a number showing the typical change in lambda cell output (millivolt) plotted against lambda ratio or lambda change. It is a graph of.

FIG. 5 is a number of graphs showing a graph for a constant air / fuel ratio in a rich region (lambda less than or equal to 1) showing different zirconia lambda cells (of similar construction) observing exhaust gas at the same location in the exhaust duct. ) Produces different output voltages over a similar temperature range.

6 is a representative change in lambda cell output (millivolt) plotted against lambda change when the cell is operated at the same temperature as in FIG. 4 and the air-fuel mixture supplied to the engine is lean. FIG.

FIG. 7: A lambda cell observes oxygen in atmospheric air, and after the heating device measures the resistance of the heating device while the cell is at a temperature at which a predetermined reference voltage output is obtained, the cell detects the oxygen in the exhaust gas. FIG. 5 is a graph showing the relationship used to determine at what resistance the heating device of the lambda cell should be operated when observing.

FIG. 8 schematically shows another embodiment of a control device used instead of the control device shown in FIGS. 2 and 3;

FIG. 9 shows the relationship used by the control device of FIG. 7;
It is a graph similar to.

[Explanation of symbols]

 2 Internal combustion engine 4 Engine unit 6 Exhaust duct 10 Oxygen sensor or lambda cell 14 Control device 16 Heater 20 Carburetor 32 Bridge circuit 36 Constant resistance 38 Constant resistance 40 Control resistance 42 Microcontroller 44 Superheater control circuit

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F02D 35/00 F02B 43/00 F02D 41/14 F02D 45/00

Claims (15)

(57) [Claims] 1. An oxygen sensing cell lambda cell having an exhaust duct, an electrical heating device provided in the duct, and having a resistance value that varies as a function of temperature, and wherein the electrical heating device has an operating resistance value. A controller for providing power to the electric heater to maintain the lambda cell at a desired operating temperature, the controller comparing the resistance of the electric heater with at least one reference value. And controlling the power supplied to the electric heating device in response to the comparison to maintain the lambda cell at the desired operating temperature, the controller comprising: Being exposed to the gas and being configured to determine the reference value while the lambda cell is producing an electrical output signal having a value that is approximately a predetermined reference value, Internal combustion engine. 2. The internal combustion engine of claim 1, wherein the reference gas comprises ambient atmospheric air. 3. The internal combustion engine according to claim 1, wherein the lambda cell comprises sirconia and the electric heating device comprises a platinum heater. 4. The internal combustion engine according to claim 2, wherein said predetermined reference value is approximately -11.1 millivolts. 5. The control device has a controllable electrical control resistor on one arm of the electrical bridge circuit and a heating device on the other arm, the control device comprising: exposing the lambda cell to a reference gas; The calibration control value of the electric control resistor is configured to measure the calibration resistance value of the electric control resistor by operating the lambda cell while the lambda cell is outputting the electric output signal at the substantially predetermined reference value, and the control resistance value of the correlation that provides the reference value is:
The controller is configured to perform an actuation function derived from the measured calibration resistance, wherein the controller is configured to cause the electrical control resistor to select a correlated control resistance, wherein at a zero point of the bridge circuit, a heater is provided. The internal combustion engine according to any one of claims 1 to 4, wherein K is a constant. 6. The control device as claimed in claim 1, wherein the power supplied to the control device is changed so that the resistance of the heating device obtains a value substantially equal to the operating resistance value of the heating device. 6. The internal combustion engine of claim 5, wherein the engine is configured to automatically change the electrical control resistance to obtain a point. 7. The internal combustion system according to claim 5, wherein the control device comprises a microcontroller configured to control a change in the electric control resistance and a change in the power supplied to the heating device. engine. 8. The internal combustion system according to claim 5, wherein the actuation function is a substantially linear function of a change in the control resistance value correlated with the change in the measured calibration resistance value. engine. 9. The controller is configured to expose a lambda cell to the reference gas and to calculate a calibration resistance value while the lambda cell outputs an electrical output signal having a value that is substantially a predetermined reference value. 5. The controller of claim 1, wherein the controller is configured to perform an actuation function that derives the correlated operating resistance from the calibration resistance, wherein the correlated operating resistance provides the reference value. 6. An internal combustion engine according to any one of the preceding claims. 10. The control device is configured to store the reference value, the control device is configured to automatically change the power supplied to the heating device, the voltage before and after the heating device and the heating. In response to data representing the current supplied to the device, the controller calculates a resistance of the heating device and is provided in response to a difference between the calculated resistance of the heating device and the reference value. The internal combustion engine of claim 9, wherein the internal combustion engine is configured to vary power, such that a resistance of the heating device is obtained to be substantially equal to the operating resistance value of the correlation. 11. The internal combustion engine of claim 1, wherein the operating function is a substantially linear function of a change in a working resistance value of the correlation and a change in the calibration resistance. 12. The internal combustion engine according to claim 1, wherein a fuel gas is used as a fuel. 13. The fuel gas according to claim 1, wherein the fuel gas is natural gas.
An internal combustion engine according to any one of claims 1 to 12. 14. A combined heating and power plant comprising the internal combustion engine according to claim 1. 15. A vehicle comprising the internal combustion engine according to claim 1. Description: