JP3052310B2 - Fuel injection control device for diesel engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel injection control device for a diesel engine.

(Prior Art) As a fuel injection device for a diesel engine, a distribution type fuel injection pump in which the injection timing and injection amount of fuel can be electronically controlled is known.

One example is shown in FIG. To explain this, in the figure, 1 is a pump housing, 2 and 3 are a low pressure side feed pump and a high pressure side plunger pump driven by a drive shaft 4, and fuel sucked by a feed pump 2 from a fuel inlet (not shown) is supplied to the housing 1. It is supplied to the pump chamber 5 in the inside, and is sent to the plunger pump 3 through the suction passage 6 opened to the pump chamber 5.

The plunger 7 of the plunger pump 3 has the same number of suction grooves 8 formed at its tip as the number of cylinders of the engine, and the other end thereof has a face cam 9 having the same number of cam ridges.
Are formed. The face cam 9 reciprocates by a predetermined cam lift over a roller 11 provided on a roller ring 10 while rotating with the drive shaft 4. By the reciprocating motion of the plunger pump 7, the fuel sucked into the plunger chamber 12 from the suction groove 8 is pumped from the distribution port for each cylinder (not shown) communicating with the plunger chamber 12 to the injection nozzle through the delivery valve. You.

A fuel return passage 13 communicates the plunger chamber 12 with the low-pressure pump chamber 5. In the middle of the fuel return passage 13, a signal (drive pulse) from a drive circuit as valve means for controlling fuel injection is provided. ), A high-speed responsive solenoid valve 14 driven according to the operating conditions of the engine is interposed. When the solenoid valve 14 is closed during the compression stroke of the plunger 7, fuel injection is started, and when the solenoid valve 14 is opened, the injection ends. That is, the fuel injection start timing is controlled according to the valve closing timing of the electromagnetic valve 14, and the injection amount is controlled according to the valve closing period.

On the other hand, in order to control the phase (lift timing) of the face cam 9, a phase control means as shown in FIG. 13 is provided. Reference numeral 18 denotes a timer piston connected so as to reciprocate in a tangential direction with respect to the roller ring 10.Basically, a pump chamber pressure acting on a high-pressure chamber 20 defined at one end of the timer piston 10 and The position of the timer piston 10 and the phase of the roller ring 10 are controlled according to the balance with the tension of the timer spring 20 provided in the low-pressure chamber 21 at the other end. However, the high-pressure chamber 20 communicates with the low-pressure chamber 21 via a bypass passage 23 in which a duty control electromagnetic valve 22 is interposed, and the average opening of the electromagnetic valve 23 that opens and closes at a predetermined frequency increases. The more the pressure is released from the high-pressure chamber 20 to the low-pressure chamber 21, the more the movement of the timer piston 18 is suppressed. By rotating the roller ring 10 in this manner, the lift area of the face cam 9 moves with respect to the injection timing of the solenoid valve 14, so that the injection rate changes according to the lift curve of the face cam 9. Become.

Controlling the solenoid valves 14 and 22 is performed by a control unit (not shown) that inputs various operating condition signals.
A microcomputer is used for the control unit. For example, for the solenoid valve 14, the optimal valve closing start timing and the valve closing period corresponding to various engine conditions such as the engine speed, and for the solenoid valve 22, the duty ratio is obtained in advance by experiments or the like, and the values are obtained. It is stored in a storage device in the control unit. At the time of actual operation, one reference pulse per one rotation of the fuel injection pump and 36 scale pulses are input to calculate the engine speed, and the engine speed and the accelerator pedal opening (depression amount) are calculated. ), The injection start timing, the injection period, and the duty ratio are read, and a drive pulse is generated from the read information and output to the solenoid valves 14 and 22.

In addition, as a well-known document of this kind of fuel injection pump,
JP-A-60-132038 and JP-A-61-14448 are examples.

(Problems to be Solved by the Invention) In such a conventional fuel injection pump, for example, when controlling the maximum injection amount, the excess air ratio detected from the oxygen concentration in the exhaust is fed back,
The closing period of the solenoid valve 14 is adjusted so that the excess air ratio does not deviate from a predetermined region mainly determined by the smoke limit. In this case, in order to improve the torque while suppressing the generation of smoke, the optimal closing period of the solenoid valve 14 is mapped in advance for each engine speed so that the average injection rate during the maximum injection amount injection becomes highest. Is stored in a memory, and basically the valve closing period of the solenoid valve 14 is determined with reference to this map, and this is corrected by the excess air ratio as needed.

However, according to such control, the following inconvenience occurs in connection with a problem in the mechanism of the fuel injection device.

That is, the average injection rate of the fuel injection device is affected not only by the fluctuation of the atmospheric pressure, but also by the fluctuation of the valve opening pressure due to the deterioration of the spring of the injection nozzle and the like, thereby maximizing the average injection rate in advance. The stored value of the valve closing period that is determined to be different from the optimal value. This means that the average injection rate decreases, which results in an increase in smoke emission and a decrease in torque.

It should be noted that the injection rate is not always the maximum, and for example, depending on the operating conditions and required performance of the engine,
In order to reduce NOx, the injection rate may be set to a value smaller than the maximum value.In that case, a deviation from the initial set optimal value occurs for the same reason as above,
This causes emission and driving deterioration.

The present invention has been made in view of such conventional problems, and provides an injection control device that can always maintain an optimum average injection rate regardless of a change in atmospheric pressure or a change in characteristics of a mechanism of the injection device. It is intended to be.

(Means for Solving the Problems) In order to achieve the above object, according to the present invention, there are provided a valve means for controlling a fuel injection start timing and an injection period as described above, and a phase control means for controlling a phase of a face cam. the control apparatus for a distributor type fuel injection pump equipped with a rotational speed detecting means 31 for detecting the engine rotational speed N as shown in FIG. 1, the load detecting means for detecting an engine load a _CC from the accelerator opening degree 32, and a basic control amount determination for determining a basic injection amount A _VM (valve closing period of the valve means) and a basic injection timing I _TM (valve closing start timing) based on the outputs of the respective detecting means 31 and 32. Means 33, phase determining means 34 for determining the basic phase _VTM (position of the timer piston) of the face cam based on the outputs of the respective detecting means 31 and 32, and excess air ratio V _AF (actual air-fuel ratio γ) of the engine. _T ) means for detecting excess air ratio
35, a basic control amount correction means 36 for correcting at least the basic injection amount based on the output of the excess air ratio detection means 35, and a basic correction of the basic phase of the face cam also based on the output of the excess air rate detection means 35. And a phase correction unit 37.
When the excess air ratio exceeds the smoke limit, the basic phase correcting means 37 outputs the basic phase _{VTM of the} face cam.
And the basic control amount correction means 36 is configured to correct the basic injection amount _AVM so as to obtain a desired fuel injection amount corresponding to the injection rate increase correction. . Incidentally, A _V, I _T, respectively V _T injection amount in the first diagram, the injection timing is a correction value of the face cam phase.

(Operation) At the beginning of use of the engine, the rotational speed N and load A
_An appropriate average injection rate is given by the basic phase _{VTM of the} face cam determined based on the engine operating state represented by _CC . However, as described above, the injection rate fluctuates even at the same cam phase due to a change over time or the atmospheric pressure, and a deviation from the optimum value occurs. This deviation is detected as a change in the excess air ratio V _AF , and based on this, the face cam phase V _TM , that is, the injection rate is corrected in the direction in which the excess air ratio V _AF approaches the target value. Specifically, for example, at the time of maximum injection amount control, the phase is corrected so that the average injection rate becomes maximum as long as the excess air ratio does not exceed the smoke limit. On the other hand, when the injection rate changes for the same injection period, the fuel injection amount also changes, but this is compensated by correcting the basic injection amount _AVM and the basic injection timing _ITM as necessary.

The cam profile of the face cam is generally set so that the required injection rate can be obtained at the time of maximum injection amount control without using the maximum injection rate area on the cam mechanism, and the cam profile or lift curve is known. Therefore, as described above, it is possible to increase the injection rate by a desired amount as needed.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

The configuration of the fuel injection pump directly controlled by the present invention is the same as that shown in FIG. 12, that is, while controlling the fuel injection timing and injection amount by the closing timing of the solenoid valve 14 corresponding to the valve means, The phase of the face cam 9 is controlled by the duty ratio of the solenoid valve 22, which is a control means. The phase of the face cam 9 is, as described above, the roller ring 10 which rotates relatively to face cam 9.
The angle around the pump shaft is changed by controlling the position of the timer piston 18.

FIG. 2 shows the details of a control unit for outputting control signals to the solenoid valves 14 and 22. The control unit comprises a microcomputer comprising an input / output circuit (I / O) 41, a ROM 42, a RAM 43, a CPU 44 and the like. Each means 3 shown in FIG.
It has 3,34,36,37 functions.

The input / output circuit 41 includes a reference signal and a scale pulse of the engine rotation speed representing the basic operation state amount of the engine, and a rotation speed signal from each of the sensors 51 and 52. An accelerator opening signal and a fuel temperature signal, a water temperature signal, and an idle signal from the fuel temperature sensor 54, the water temperature sensor 55, and the idle switch 56 are input. Further, the input / output circuit 41 receives an air-fuel ratio signal from an air-fuel ratio sensor 57 that detects an excess air ratio from the oxygen concentration in the engine exhaust. 58 is a DVC sensor that detects the actual valve-closing start timing and the valve-closing period of the solenoid valve 14, that is, the injection start timing and the injection amount, and 59 is a timer piston position sensor that detects the timer piston position corresponding to the face cam phase. These are provided as needed for the purpose of improving the control accuracy by feeding back the results of controlling the fuel injection amount / injection timing and the timer piston position.

The CPU 44 fetches various signals from the input / output circuit 41 according to a program stored in the ROM 42, performs predetermined arithmetic processing, and data for controlling the solenoid valves 14 and 22, that is, the closing of the solenoid valve 14 is started. Timing and closing period,
For the solenoid valve 22, the duty ratio of the drive pulse is determined and these are set in the input / output circuit 41. Along with this,
The input / output circuit 41 outputs a control signal to the solenoid valves 14 and 22.

Next, an example of the operation of the CPU 44 will be described with reference to the flowchart of FIG.

First, at step 61, the engine speed N and the accelerator opening
A _CC , cooling water temperature T _W , fuel temperature T _F , timer piston position V
Each signal of _T is read, and subsequently, in step 62, the N, A
_The basic injection amount A _VM , the basic injection timing I _TM , and the basic timer piston position V _TM are determined based on the characteristics illustrated in FIGS. 4 to 6 based on the _CC signals. At this time, the control amounts are corrected as necessary according to the cooling water temperature _TW or the fuel temperature _TF . The data shown in FIGS. 4 to 6 are previously processed by RO processing so that data corresponding to each characteristic can be obtained by arithmetic processing, search, interpolation calculation, etc. based on a predetermined input signal.
It is obtained by executing the processing stored in M42.
This applies to FIGS. 7 to 11 described below.

Next, in step 63, the output voltage V of the air-fuel ratio sensor 57
_AF is read, and the actual air-fuel ratio λ _T on the characteristic illustrated in FIG. 7 is calculated as a function of the _AF . And step 64
In order to feed back the actual injection amount, the DVC sensor 58
After the valve-closing period of the solenoid valve 14 is detected based on the output of the ECU, in step 65, it is determined whether or not the current actual air-fuel ratio γ _T is within the smoke limit.

Determination of smoke limit, the relationship between the accelerator opening A _CC and the engine speed N at that time as illustrated in FIG. 8, and the cooling water temperature T _W which optionally fuel temperature T _F
Target air-fuel ratio λ _MAP and actual air-fuel ratio λ _T
Is compared with, for example, the accelerator opening
Actual air-fuel ratio λ _T compared to target air-fuel ratio λ _MAP when A _CC is 100%
Is smaller than the smoke limit at the time of full opening. If it is determined that the actual air-fuel ratio λ _T exceeds the smoke limit, the routine proceeds to step 66, and if it is determined that the actual air-fuel ratio is within the smoke limit, the routine proceeds to step 67.

Each step 66 and 67, as follows and the injection quantity correction .DELTA.A _V injection timing correction amount [Delta] I _T, and a timer piston position correction amount [Delta] V _T is determined. First, the maximum variation width Δλ of the air-fuel ratio is calculated from the relationship between the engine speed N and the accelerator opening _ACC with the characteristics illustrated in FIG. 9, and is calculated based on the target air-fuel ratio λ _MAP and the actual air-fuel ratio λ _T When it is determined that the air-fuel ratio difference is smaller than Δλ in comparison with the above-described condition, it is sufficient to correct only the injection amount under this condition, so that the injection timing correction amount ΔI _T = 0 and , Injection amount correction amount ΔA _V
Is determined on the basis of the air-fuel ratio difference on the characteristics exemplified in FIG. On the other hand, when it is determined that the air-fuel ratio difference is larger than Δλ, not only the injection amount correction amount ΔA _V but also the injection amount correction amount ΔA _V so that the actual air-fuel ratio λ _T approaches the target air-fuel ratio λ _MAP quickly. based on the air-fuel ratio difference also determines the eleventh injection timing on the illustrated characteristic in Figure correction amount [Delta] I _T. The injection amount correction amount ΔA _V and the injection timing correction amount ΔI _T determined in this way are added to the basic injection amount A _VM and the basic injection timing ΔI _TM respectively in the next step 68, and the final control amount Injection amount A
_V and the injection timing _IT are obtained. Because when the air-fuel ratio difference is smaller than Δλ is ΔI _T = 0, so that the basic injection timing I _TM is set as it is as I _T.

Incidentally, the timer piston position V _T, step
When the actual air-fuel ratio lambda _T is determined to exceed the smoke limit at 65, the timer piston position correction amount [Delta] V _T is calculated in step 66. As already described, since it is when the temporal change or the like cause to the injection rate on the mechanism from exceeding the smoke limit control according to the basic control amount is lower than the appropriate value, the correction amount [Delta] V _T Is added to the basic timer piston position _VTM to advance the face cam phase and correct the injection rate in the increasing direction. Current phase of the face cam 9 is known from the control signal V _T of the timer piston position, and because the data of the cam profile are known, the appropriate correction amount, that the timer piston position correction amount [Delta] V _T of the injection rate, these known amount Can be easily calculated from the relationship. On the other hand, if the injection rate is changed while the injection period is fixed, the injection amount also changes.Therefore, in step 66, the injection amount correction amount is adjusted so that the desired fuel injection amount is obtained with the control of the injection rate. ΔA _V is determined. In this way, when the air-fuel ratio exceeds the smoke limit, the timer piston position V _T is increased until the injection rate becomes maximum.
Is corrected, the required fuel injection amount and the appropriate injection rate are maintained irrespective of the deterioration of the mechanical parts of the fuel injection pump and fluctuations in the atmospheric pressure, so that the required engine torque is secured and the smoke is increased. Can be suppressed.

On the other hand, when it is determined in step 65 that the actual air-fuel ratio λ _T is within the smoke limit, in step 67, the timer piston position correction amount V _T = 0 is set. In this case, the basic timer piston position V _TM is directly set as a timer piston position V _T at the next step 68. As a result, an unnecessary increase in the injection rate within the smoke limit is avoided, and proper emission performance is maintained.

In step 69, the injection amount A _V as the control amount determined as described above, the injection timing I _T , the timer piston position
A process of storing V _T to RAM43 of a predetermined address, the solenoid valve via the respective control amount output circuit 41 along with this
Output to 14 and 22.

(Effects of the Invention) As described above, according to the present invention, the excess air ratio is fed back to correct and control not only the fuel injection amount but also the phase of the face cam. Irrespective of fluctuations, it is possible to always obtain the optimum injection rate, and therefore maximize the performance of diesel engines under any operating conditions without deteriorating exhaust performance such as smoke be able to.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration concept of the present invention, FIG. 2 is a block diagram of a control unit according to one embodiment of the present invention, FIG. 3 is a flowchart showing an example of a control operation of the embodiment, and FIGS. FIG. 11 is a characteristic diagram showing the contents of various data used in the control operation of FIG. FIG. 12 is a longitudinal sectional view of an example of the fuel injection pump controlled by the embodiment, and FIG. 13 is a plan sectional view of the timer piston portion. 1 ... Pump housing, 3 ... Plunger pump, 5
…… Pump room, 7 …… Plunger, 9 …… Face cam, 12 …… Plunger room, 13 …… Fuel return passage, 14 ……
Solenoid valve, 18 Timer piston, 22 Solenoid valve, 41
Input / output circuit, 42 ROM, 43 RAM, 44 CPU, 51
... Reference pulse generation sensor, 52 ... Scale pulse generation sensor, 53 ... Accelerator opening degree sensor, 57 ... Air-fuel ratio sensor, 58 ... DVC sensor. 59 …… Timer piston position sensor.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F02D 1/00-41/40 F02M 41/12

Claims (1)

(57) [Claims] 1. A plunger pump that reciprocates based on the relative rotation of a roller ring and a face cam, and a valve means located in the middle of a fuel return passage of the plunger pump for controlling fuel injection start timing and injection period. And a phase control means for controlling the phase of the face cam by driving the roller ring. In the control device for a distribution type fuel injection pump, a rotation speed detection means for detecting an engine rotation speed, and an engine load are detected. Load detecting means, basic control amount determining means for determining the basic fuel injection amount and basic injection timing based on the output of each detecting means, and similarly determining the basic phase of the face cam based on the output of each detecting means. Phase determining means, excess air rate detecting means for detecting an excess air rate of the engine, and at least a basic injection amount based on an output of the excess air rate detecting means. And a basic phase correction means for correcting the basic phase of the face cam based on the output of the excess air ratio detection means, wherein the excess air ratio has a smoke limit. When it exceeds, the basic phase of the face cam is corrected in the direction in which the injection rate increases, and the basic control amount correction means adjusts the injection amount so that the expected fuel injection amount is obtained in accordance with the injection rate increase correction. A fuel injection control device for a diesel engine, wherein the fuel injection control device is configured to make a correction.