JPH0647961B2 - Maximum injection amount control device for diesel engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a maximum injection amount control device for a diesel engine, which corrects and controls the maximum fuel injection amount of the diesel engine by an oxygen concentration detection device in exhaust gas.

[Conventional technology]

Conventionally, in a diesel engine, it is known that a sensor for detecting an oxygen concentration is provided in an exhaust passage to reduce a maximum injection amount when an excess air ratio becomes smaller than a smoke generation level.

For example, Japanese Utility Model Laid-Open No. 56-79633 discloses that the maximum injection amount is decreased when the oxygen concentration is low, and the maximum injection amount is increased to the original value when the oxygen concentration is high. Has been done.

Further, JP-A-58-178830 discloses that when the carbon dioxide concentration is high, the maximum injection amount is decreased, and when the oxygen concentration is high, the maximum injection amount is increased to the original value. It is shown.

[Problems to be solved by the invention]

Generally, as a problem peculiar to diesel engines, there is a conflicting requirement that the smoke should not be generated and that the fuel injection amount should be increased as much as possible in order to improve the output. Since it is set mechanically, it is possible to reduce the maximum injection amount when smoke occurs, but once the maximum injection amount that is mechanically set, unless smoke comes out, It was not considered to increase the output, so there was an operating condition in which the maximum output was insufficient even though the output could be increased even more.

The present invention is intended to realize a system capable of further increasing the maximum output as long as smoke is not generated and preventing the generation of smoke due to aging.

[Means for solving problems]

Therefore, in the present invention, an oxygen concentration detection means provided in the exhaust passage of the engine to detect the oxygen concentration in the exhaust gas,
Maximum injection amount variable control means for variably controlling the maximum injection amount of the fuel injection pump, and when the excess air ratio corresponding to the oxygen concentration detected by the oxygen concentration detecting means is larger than the set excess air ratio, increase it by a small amount. , When it is smaller than the set excess air ratio, the maximum injection amount correction amount obtained by slightly reducing the
And a storage unit that stores the address at the address corresponding to the engine state at that time, and corrects the maximum injection amount by the maximum injection amount correction amount read from the storage unit and stored at the address corresponding to the current engine state. A maximum injection amount control device for a diesel engine is provided.

[Action]

According to the configuration of the present invention, the oxygen concentration in the exhaust gas, which is the result of thermal calcination, is directly detected, and the actual excess air ratio can be obtained. Since the maximum injection amount is corrected based on the value of the detected excess air ratio, the maximum injection amount cannot be endured by the excess air ratio value and is fed back.
It is possible to control the maximum injection amount so that the excess air ratio immediately before the smoke is generated can be produced in response to changes in environmental conditions or changes in characteristics of the nozzle and the like with time.

Further, the optimum maximum injection correction amount learned in each engine state is stored in the storage means, preferably in the non-volatile memory and updated, and the stored maximum injection amount correction amount is changed according to the engine state changing every moment. By correcting the read maximum injection amount in accordance with the above, it is possible to control the optimum maximum injection amount in response to changes in the engine state.

Embodiments Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 schematically shows the structure of a 4-cylinder diesel engine to which the present invention is applied. A well-known four-cylinder diesel engine 1 is equipped with an injection amount electronic control unit (so-called electronic governor), for example, a Bosch VE type distribution injection pump 2
Is mounted, and is driven and rotated by the engine 1 at a speed of ½ of the engine speed by a gear, a belt, etc. not shown. Each cylinder of the engine 1 has an injection nozzle 3
Nos. 1 to 34 are attached, and the nozzles 31 to 34 and the distribution type injection pump 2 are connected by injection steel pipes 41 to 44. Combustion pumped by the pump 2 at a predetermined timing causes the nozzles 31 to 31. From ~ 34, a predetermined amount is injected into the combustion chamber (or the sub chamber) of each cylinder of the engine 1.
A disk 6 having a large number of protrusions on its outer periphery is attached to the crankshaft of the engine 1, and is configured to generate one pulse signal every time the protrusion crosses the vicinity of a known electromagnetic big-up 8. , The disk 6, and the electromagnetic pickup 8 form an engine speed detector that obtains a frequency signal proportional to the speed of the engine 1.

The N signal is output to the control computer 20 as a rotation speed signal, and the computer 20 further receives a signal α from an accelerator opening sensor 10, which is, for example, a potentiometer, which obtains a voltage signal corresponding to the accelerator pedal depression amount by the driver, and the timing is changed every moment. The optimum fuel injection amount is calculated and determined for the changing engine operating state. Then, in order to realize the output injection amount, a drive signal is output to the injection amount control actuator 11 such as a linear solenoid attached to the injection pump 2.

An air-fuel ratio sensor 13 that detects the oxygen concentration of the exhaust gas is attached to the exhaust pipe 7. The air-fuel ratio sensor 13 is a known oxygen concentration detector that produces an output current corresponding to the oxygen concentration in the atmosphere by applying a constant voltage.
That is, by applying an appropriate constant voltage (for example, 0.8 V) to the air-fuel ratio sensor 13, as shown in FIG. 7, it has a linear characteristic within a certain range with respect to the excess air ratio in the exhaust gas. Output current is generated. This output current is output to the control computer 20.

Next, the detailed configuration of the distribution type injection pump 2 will be described with reference to FIG. The base of the injection pump is a known Bosch VE injection pump, and description of fuel suction, pressure feeding, distribution, and injection timing control member and its operation is the same as that of the known VE injection pump, and therefore description thereof is omitted. To do. The feature of this pump is that the axial displacement of the plunger 22 of the spill ring 21, which is a fuel overflow adjusting member, is controlled by the actuator 11 using a linear solenoid.
The injection amount is electronically controlled by the computer 20. When the control current output from the computer 20 is applied to the coil 23 of the actuator 11, a magnetic force having a strength corresponding to the control current is generated between the stator 24 and the moving core 25, and the moving core 25 causes the spring 30 to move. It is pulled to the left side in the figure due to the reaction force of. Along with the movement of the core 25 to the left, the lever 26, which is in contact with the core 25 at one end, rotates counterclockwise in the drawing around the fulcrum 27 by the tension of the spring 31. The lever 26 is connected to the spill ring 21 at the other end,
Along with the above operation, the spill ring 21 is moved to the right side in the figure. In the VE type injection pump, the spill ring 21
Is shifted to the right in the figure, the fuel overflow time, that is, the injection end time is delayed, and as a result, the injection amount is increased. As described above, the injection amount increases when the energizing current to the actuator 11 increases, and the injection amount decreases when the current decreases. Therefore, if the energizing current value is controlled by the computer 20, the injection amount can be controlled. Is.

In addition, in order to improve control accuracy, the moving core 2
5, the position sensor 12 is coaxially attached to the actuator 11 so as to correct the current supplied to the actuator 11 by detecting the actual position of the position sensor 5 and the position sensor 12 is coaxial with the moving core 25. The probe 28 and the position detection coil 29 are made of ferrite or the like. The normal injection amount control is performed by the rotation speed detector 8 by the configuration of FIGS. 1 and 2 described above.
Based on the N signal from the accelerator and the signal α from the accelerator opening sensor 10, the computer 20 commands the optimum spill ring position, that is, the position of the moving core 25 of the actuator 11 to control the energizing current to the actuator. To get the injection amount of. In this embodiment, the maximum injection amount variable control means is realized by internal processing of the computer 20, and the command value for instructing the position of the actuator 11 is limited based on the maximum injection amount.

FIG. 3 shows a detailed configuration of the control computer 20.

The control computer 20 has two power supply circuits 105,
With 106. The power supply circuit 105 is directly connected to the battery 17 without passing through the key switch 18, and supplies power to the temporary storage memory (RAM) 107. Therefore R
Power is always applied to the AM 107 regardless of the key switch 18. The other power supply circuit 106 is connected to the battery 17 through the key switch 18, and supplies power to parts other than the RAM 107. RAM1
Reference numeral 07 is a temporary storage memory (RAM) temporarily used during the program operation. However, as described above, the stored contents are kept irrespective of the key switch 18 even if the power is always applied and the key switch 18 is turned off to stop the feedback operation. Is a non-volatile memory. The correction amount ΔQ of the maximum injection amount, which will be described later, is also stored in the RAM 107. 108
Is a read-only memory (ROM) for storing programs and various constants.

100 is a microprocessor (M
PU). A rotation speed counter 101 is a rotation speed counter that counts the engine rotation speed from a signal from the rotation speed (number) sensor 8. In addition, this revolution counter 1
01 sends an interrupt command signal to the interrupt control unit 102 in synchronization with the engine rotation. Upon receiving this signal, the interrupt control unit 102 outputs an interrupt signal to the microprocessor 100 via the common bus 150. Reference numeral 104 denotes an analog input port composed of an analog multiplexer and an A / D converter, which has a function of A / D converting the signals from the accelerator opening sensor 10 and the air-fuel ratio sensor 13 and sequentially reading them into the microprocessor 100. The output information of each of these units 101, 102, 104 is transmitted to the microprocessor 100 through the common bus 150. 109 is an output port for setting the control current to the actuator 11, which is calculated and determined by the MPU 100, 1
Reference numeral 10 denotes a drive circuit that converts the output signal into an actual operating current, and the linear solenoid actuator 11
It is connected to the. 111 is a timer, which measures the elapsed time and transmits it to the MPU 100.

4 and 5 show flowcharts of the processing in the microprocessor 100.

Steps 200 and below are routines showing the calculation processing of the fuel injection amount. First, in step 201, a basic injection amount Q ₀ as a fuel injection amount according to a load state of the engine is calculated from signals from the engine speed sensor 8 and the accelerator opening sensor 10. Next, at step 202, the basic maximum injection amount QFull ₀ is calculated from the engine speed Ne using the engine speed as a parameter to limit the upper limit of the injection amount. As an example, QFull ₀ can be determined using the engine speed Ne as a parameter as shown in FIG. Next, at step 203, the correction amount ΔQn is added to the basic maximum injection amount QFull ₀ determined at step 202.
Then, the final maximum injection amount QFull is determined.
That is, in step 203, ΔQn for QFull ₀
The maximum injection amount can be corrected like QFull ₁ or QFull ₂ shown in FIG. Next, at step 204, the basic injection amount Q ₀ determined at step 201 is compared with the maximum injection amount QFull obtained at step 203. If Q ₀ <QFull, the routine proceeds to step 205, where the basic injection amount Q ₀ is the final injection amount QFi
Let N. On the other hand, if Q ₀ ≧ QFull, the routine proceeds to step 206, where the learning correction calculation of the correction amount ΔQn of the maximum injection amount is performed. Details of step 206 will be described later. Next, at step 207, the maximum injection amount QFull is changed to the final injection amount QFi.
N, and then proceeds to step 208 to move the output port 109 to displace the actuator 11 according to QFiN.
Output to.

The learning correction calculation of the maximum injection amount correction amount ΔQ executed in step 206 described above will be described with reference to FIG.

At step 209, the air-fuel ratio sensor 13 described in FIG.
Determine the output of. The air-fuel ratio sensor 13 has a detection characteristic as shown in FIG. That is, by applying a constant voltage (for example, 0.8 V) to the air-fuel ratio sensor 13, it has a characteristic that a linear current is generated with respect to the excess air ratio in a certain range of exhaust gas. Utilizing this characteristic,
For example, the generated current i (λ = 1.2) for the excess air ratio λ = 1.2 as the limit of smoke generation in the exhaust gas is used as the criterion.

Therefore, if the output of the air-fuel ratio sensor 13 is λ> 1.2, the routine proceeds to step 210, where the correction amount ΔQn of the maximum injection amount is added and corrected by a minute correction amount Δq (for example, 0.1 mm ³ / st equivalent amount). On the other hand, if the output of the air-fuel ratio sensor 13 is λ <1.2 in step 209, the process proceeds to step 211 and Δ
Subtract Δq from Qn. If λ = 1.2, ΔQn is not corrected. The ΔQn corrected as described above is stored in the RAM 108 which is the nonvolatile memory described above in step 212. In the RAM 107, there is secured a memory space for storing data of the correction amount ΔQn (ΔQ ₁ ... ΔQn) for each appropriately divided engine speed range, and in step 212, the engine speed at that time is stored. The correction amount ΔQn is stored in the memory address corresponding to. That is, as shown in FIG. 8, the optimum correction amount ΔQn of the maximum injection amount is learned and stored for each engine speed. Therefore, it is possible to control the maximum injection amount corresponding to the change in the engine state.

By the process described above, the maximum injection amount QFull is set so that the excess air ratio λ is near the smoke generation limit, so that the generation of smoke during high load operation of the engine is suppressed and the maximum injection amount QFull is unnecessarily small. And, it does not limit the output performance of the engine.

Another embodiment of the learning correction calculation processing of the maximum injection amount correction amount ΔQn executed in step 206 described above
Description will be made with reference to the drawings.

First, in step 213, the output of the air-fuel ratio sensor 13 that detects the excess air ratio λ is fetched. Then step 214
Then, the correction amount Δq of ΔQ corresponding to the excess air ratio λ is RO
The correspondence table (map) stored in advance in M108 is searched. As shown in FIG. 10, the correction amount Δq is such that when the excess air ratio λ = 1.2, Δq = 0, and the excess air ratio λ corresponds to the correction amount Δq. The relationship between λ and Δq may be linear as shown in FIG. 10A or nonlinear as shown in B according to the characteristics of the engine. In the above embodiment, the Bosch VE type injection pump in which the injection amount is controlled by the linear solenoid actuator is described as the injection pump, but the present invention can be easily implemented even if various other diesel injection pumps are used. Is.

〔The invention's effect〕

As described above, according to the present invention, the maximum injection amount can be set so that the oxygen concentration in the exhaust gas is detected by the oxygen concentration detector (air-fuel ratio sensor) and the set excess air ratio is achieved. There is an excellent effect that the generation of smoke during high-load operation of the engine can be effectively suppressed and the output performance is not deteriorated regardless of changes in environmental conditions and changes in characteristics of valves and the like.

Furthermore, it can quickly respond to changes in the engine state, further increasing the maximum injection amount when smoke does not occur,
There is an excellent effect that a high output can be obtained.

[Brief description of drawings]

1 is an overall configuration diagram showing an embodiment of the present invention, FIG. 2 is a partial sectional configuration diagram of the fuel injection pump in FIG. 1, and FIG. 3 is a detailed configuration diagram of a control computer in FIG. 4 and 5 are flowcharts showing the processing procedure in the control computer, FIG. 6 is a characteristic diagram showing an example of the maximum injection amount,
FIG. 7 is a characteristic diagram of the output of the air-fuel ratio sensor in the exhaust gas, FIG. 8 is an explanatory diagram showing an example of the correction amount ΔQ of the maximum injection amount, and FIGS. 9 and 10 are flow charts in other examples. It is a characteristic diagram. 1 ... Diesel engine, 2 ... Fuel injection pump, 7
... Exhaust pipe, 8 ... Electromagnetic pickup, 10 ... Accelerator opening sensor, 11 ... Injection amount control actuator, 1
3 ... Oxygen concentration sensor (air-fuel ratio sensor), 20 ... Control computer, 31, 32, 33, 34 ... Injection nozzle, 100 ... Microprocessor, 107 ... Temporary storage memory (RAM), 108 ... Readout Dedicated memory (R
OM).

Claims (2)

[Claims] 1. An oxygen concentration detecting means provided in an exhaust passage of an engine for detecting an oxygen concentration in exhaust gas, a maximum injection amount variable control means for variably controlling a maximum injection amount of a fuel injection pump, and the oxygen concentration. When the excess air ratio corresponding to the oxygen concentration detected by the detection means is larger than the set excess air ratio, a minute amount is increased, and when it is smaller than the set excess air ratio, a small amount is decreased to obtain the maximum injection amount correction amount. A maximum injection amount according to the maximum injection amount correction amount stored in the address corresponding to the current engine state read from the storage unit. A maximum injection amount control device for a diesel engine, which is modified. 2. The maximum injection amount control device for a diesel engine according to claim 1, wherein said storage means is a non-volatile memory.