JP2564285B2 - Step-out adjustment device for step motor for internal combustion engine - Google Patents

Description

The present invention relates to a step-out adjustment device for a step motor in an internal combustion engine.

[Conventional technology]

In an internal combustion engine in which the amount of fuel or air supplied to the engine cylinder is controlled by using a step motor, the engine speed or intake pipe is usually set as described in, for example, JP-A-61-126364. The required step position of the step motor is obtained from the negative pressure or the like, and the step motor is drive-controlled so that the step position of the step motor becomes the required step position. However, with such a step motor, it is difficult to directly detect the step position at which the step motor is actually located at present. Therefore, normally, as described in JP-A-57-26238, a storage means for storing the step position of the step motor is provided,
Every time the engine is stopped or the engine is started, the step motor is driven to the maximum step position or the minimum step position to match the actual step position of the step motor with the step position of the step motor stored in the storage means, and then the storage means. The step position stored in 1 is regarded as the actual step position, and the step motor is driven and controlled.

[Problems to be solved by the invention]

However, in reality, the actual step position of the step motor and the step position stored in the storage means may be deviated during engine operation, that is, the step motor may be out of step. If the step motor is driven and controlled based on the stored step position, the amount of fuel or air cannot be accurately controlled. Conventionally, the step-out is adjusted every time the engine is stopped or the engine is started as described above, but this has a problem that the step-out that occurs during engine operation cannot be adjusted.

[Means for solving problems]

In order to solve the above problems, according to the present invention, as shown in the block diagram of the invention of FIG. 1, a means 100 for obtaining a required step position according to the operating state of the engine and a current step position of the step motor are shown. In the internal combustion engine, which comprises a storage means 101 for storing, and which controls the drive of the step motor 17 so that the step position of the step motor 17 becomes the required step position based on the step position stored in the storage means 101. A determining means 102 for determining whether or not the required step position has reached a predetermined upper limit position or a lower limit position for a predetermined time or more, and a required step position continues for the upper limit position or the lower limit position for a predetermined time or more. Then, the step motor 17 is driven to the maximum step position or the minimum step position and the actual step position of the step motor 17 and the storage means 101 Drive control means to match the stored step position of the step motor 17 10
It has 3 and.

〔Example〕

Referring to FIG. 2, 1 is an engine body, 2 is a piston,
Reference numeral 3 is a combustion chamber, 4 is an intake valve, 5 is an intake port, 6 is an intake manifold, 7 and 8 are exhaust ducts, 9 is an exhaust valve, 10 is an exhaust port, and 11 is an exhaust manifold. A venturi portion 12 is formed in the intake duct 8, and a fuel outlet 13 is opened in the venturi portion 12. Fuel outlet 13 is LPG gas supply pipe 1
A flow rate control valve 16 that is connected to the LPG gas regulator 15 via 4 and controls the flow rate of the LPG gas is arranged in the LPG gas supply pipe 14. The flow control valve 16 is drive-controlled by a step motor 17. On the other hand, a throttle valve 18 is arranged in the intake duct, and a bypass pipe that bypasses the throttle valve 18 is provided.
19 is attached to the intake duct 7. An idling speed control valve 20 for controlling the idling rotation speed is arranged in the bypass pipe 19, and the idling speed control valve 20 is drive-controlled by a step motor 21. The step motors 17 and 21 are controlled by the output signals of the electronic control unit 30, respectively.

The electronic control unit 30 is composed of a digital computer, and has a ROM (read only memory) 32, a RAM (random access memory) 33, a CPU (microprocessor) 34, and an input port 35 which are mutually connected by a bidirectional bus 31.
And an output port 36. A backup ram 37, which is a non-volatile memory, is connected to the CPU 34. A negative pressure sensor 22 that generates an output voltage proportional to the negative pressure in the intake manifold 6 is attached to the intake manifold 6, and the negative pressure sensor 22 is connected to an input port 35 via an AD converter 38. An oxygen concentration detector 23 is attached inside the exhaust manifold 11, and the oxygen concentration detector 23 is connected to an input port 35 via a comparator 39. In addition, input port 35
A rotation speed sensor 40, which generates an output pulse each time the engine crankshaft rotates by a predetermined crank angle, is connected to. The output port 36 is connected to the step motors 17 and 21 via the corresponding drive circuits 41 and 42, respectively.

During engine operation, an amount of LPG gas that is almost proportional to the intake air amount is supplied from the fuel outlet 13 into the venturi section 12,
The LPG gas amount is corrected by the flow rate control valve 16 driven by the step motor 17. That is, the oxygen concentration detector 23 generates an output voltage of about 0.1 volt when the exhaust gas is in an oxidizing atmosphere, that is, when the air-fuel ratio of the mixture of LPG gas supplied into the engine cylinder is larger than the theoretical air-fuel ratio. However, when the exhaust gas is in a reducing atmosphere, that is, when the air-fuel ratio of the air-fuel mixture supplied into the engine cylinder is smaller than the stoichiometric air-fuel ratio, an output voltage of about 0.9 V is generated. Therefore, based on the output signal of the oxygen concentration detector 23, the amount of LPG gas flowing out from the fuel outlet 13 can be feedback-controlled so that the air-fuel ratio becomes the stoichiometric air-fuel ratio.

FIG. 3 shows a flow chart for calculating the required step position of the step motor 17. Referring to FIG. 3, first, at step 50, it is judged if the operating conditions are such that the air-fuel ratio should be feedback-controlled.
If it is the operating state for feedback control, step 51.
In step 52, the output signal of the oxygen concentration detector 23 is taken into the CPU 34, and in step 52, the required step position S is calculated from the output signal of the oxygen concentration detector 23. On the other hand, when it is not the feedback condition, the routine proceeds to step 53, where the output signal of the negative pressure sensor 22 and the output signal of the rotation speed sensor 40 are output.
The required step position S is calculated from the engine speed, negative pressure, etc. in step 54, after being taken into the CPU 34. The relationship between engine speed, negative pressure, etc. and the required step position S is RO
It is stored in M32, and therefore, in step 54, the required step position S is obtained from these relationships stored in ROM32.

FIG. 4 shows the change in the required step position S calculated in step 52 of FIG. Step motor 17
When the step position becomes larger, the flow control valve 16 operates in the direction to open, so that the supply amount of LPG gas increases. On the other hand, when the step position of the step motor 17 becomes smaller, the flow rate control valve 16 operates in the direction of closing the valve, so that the LPG gas supply amount decreases. In the curve P of FIG. 3, sections t ₁ , t ₃ ,
t ₅ shows the time when the air-fuel mixture richer than the stoichiometric air-fuel ratio is being supplied into the engine cylinder, at which time the required step position S is gradually decreased. That is, the flow control valve 16 is moved in the valve closing direction to reduce the supply amount of LPG gas. On the other hand, in the curve P of FIG. 3, sections t ₂ , t ₄ ,
t ₆ shows the time when the air-fuel mixture that is thinner than the stoichiometric air-fuel ratio is being supplied into the engine cylinder, at which time the required step position S is gradually increased. That is, the flow control valve 16 is moved in the opening direction to increase the supply amount of LPG gas.

The step motor 17 can take each step position from step position 0 to step position 125, but the actual use range of the step position is, for example, step position 30 to step position 90. That is, the step motor 17 is preset so that the air-fuel ratio becomes the stoichiometric air-fuel ratio when the step position is, for example, 60, that is, when the flow control valve 16 is half-open, and the step position is, for example, 60 even during the feedback control. It only moves up and down a few steps around.
Therefore, normally, the required step position S moves up and down around 60 as shown by the curve P in FIG. That is, normally, the required step position does not reach 30 or 90, and when the required step position becomes 30 or 90, it means that some abnormality has occurred. Therefore, the required step position 30 is set to the lower limit position MIN, the required step position 90 is set to the upper limit position MAX, and the required step position S is not made smaller than the lower limit position MIN and is not made larger than the upper limit position MAX. That is, for example, when the required step position S exceeds MAX, the required step position S is set to MAX.

On the other hand, the current step position of the step motor 17 is set in advance.
It is stored in the RAM 37, and normally the actual step position of the step motor 17 and the step position stored in the RAM 37 are the same. Therefore, if the required step position S changes from 60 to 61, for example, the step motor 17 moves from the step position 60 based on the step position stored in the RAM 37.
Only one step in 61 is driven to rotate following the change in the required step position S.

However, for some reason, the actual step position of the step motor 17 may deviate from the step position stored in the RAM 37, that is, the step motor 17 may lose step. For example, in an extreme example, when the actual step position of the step motor 17 and the position stored in the RAM 37 are deviated by 30 steps and the actual step position of the step motor 17 is 60, the step stored in the RAM 37 This is the case when the position is 90. In such a case, the CPU 34 determines that the step motor 17 is in the step position 90 even though the step motor 17 is actually in the step position 60, and the air-fuel ratio supplied to the engine cylinder is low. If so, the CPU 34 operates to increase the step position of the step motor 17 above 90, that is, to increase the required step position above 90, in order to increase the air-fuel ratio. However, as described above, the required step position S cannot be larger than the maximum value of 90, so that the required step position S fluctuates around 90 as shown by the curve Q in FIG. That is, in other words, the fact that the step position S fluctuates near MAX indicates that the step motor 17 may be out of step. On the other hand, when the actual step position of the step motor 17 is 60 and the step position stored in the RAM 37 is 30, the required step position S is the MIN of the required step position S. It will fluctuate around 30. That is, the fact that the required step position S fluctuates near MIN indicates that the step motor 17 may be out of step.

In particular, when LPG gas is used, the supply amount of LPG gas whose stoichiometric air-fuel ratio is the air-fuel ratio varies depending on the composition of LPG gas. That is, when using the reference LPG gas, when the actual step position of the step motor 17 is 60 and the air-fuel ratio is set to the stoichiometric air-fuel ratio, when another LPG gas is used, the step motor In some cases, the air-fuel ratio becomes the stoichiometric air-fuel ratio when the actual step position of 17 is 80, for example. In such a case, when the feedback control is being performed, the actual step position of the step motor 17 fluctuates around 80. Therefore, in such a case, if the step motor 17 loses steps by 10 steps. The required step position S will fluctuate around MAX. Therefore, when LPG gas is used, there are more opportunities for the required step position S to change in the vicinity of MAX, as compared with the case where gasoline whose composition hardly changes.

According to the present invention, the required step position S is thus MAX or MIN.
When it is fluctuating in the vicinity, it is determined that step-out is occurring, and the purpose is to drive-control the step motor 17 so as to adjust the step-out. It may fluctuate around MAX.
That is, for example, when foreign matter adheres to and accumulates on the valve port of the flow control valve 16 due to aging, and the flow area of the valve port decreases. In such a case, in order to obtain the required flow area, the valve opening amount of the flow rate control valve 16 must be increased, and therefore the required step position S becomes large. In extreme cases, the required step position S is MAX.
It will fluctuate around. In such a case, the required step position S will still change around MAX even if the step-out adjustment work is performed. Therefore, in such a case, it is considered that there is a change with time, and the learning coefficient is corrected as will be described later, thereby ensuring good feedback control thereafter.

Next, the drive control method of the step motor according to the present invention will be described with reference to FIG.

Referring to FIG. 5, first, the required step position S obtained in the routine of FIG. 3 is multiplied by the learning coefficient k to obtain the required step position A. This learning coefficient k is used for correction due to changes over time, and normally, it can be considered that k = 1. Therefore, normally, the required step position A
Matches the required step position S. Next, at step 61, it is judged if the required step position A is MAX shown in FIG. 4, and if not MAX, the routine proceeds to step 62. At step 62, it is judged if the required step position A is MIN shown in FIG. 4, and if it is not MIN, the routine proceeds to step 63, where counters C and D are cleared. The required step position A is usually not MAX or MIN, so in most cases step 62
To Step 63. Next, at step 64, the step motor 17 is drive-controlled so that the step position of the step motor 17 becomes the required step position A. At this time, if the feedback control is in progress, the required step position A changes as shown by the curve P in FIG. 4, and if the feedback control is not in progress, the required step position S obtained from the ROM 32 in step 54 in FIG. Based on the above, the step position of the step motor 17 is controlled to be the required step position A.

When the required step position A is MAX or MIN, the routine proceeds from step 61, 62 to step 65, and the counting operation of the counter C is started. Required step position A continues MA
When it is X or MIN, the count value of the counter C gradually increases, and when the count value of the counter C exceeds a constant value Co, that is, when a predetermined time elapses after the required step position A becomes MAX or MIN, from step 66. In step 67, the counter D is incremented by 1. Then step
At 68, it is judged if the count value of the counter D is larger than the constant value Do, and if the count value of the count D is smaller than Do, the routine proceeds to step 69, where the step motor 17 is initialized. The initialization of the step motor 17 is, for example, a constant number of steps required to rotationally drive the step motor 17 to the maximum step position 125, for example,
This is to issue a command to rotate the step motor 17 by this initialization step number by adding 15 steps. When this command is issued, the step motor 17 is rotated in step 64 by the number of initialization steps.
Such initialization processing is performed several times until the count value D becomes Do. Of course, this initialization process may be performed only once. As described above, in the initialization process, the step motor 17 can be driven to rotate more than the number of steps required to drive the rotation to the maximum step position 125, so when the initialization process is completed, the step motor 17 is at the maximum step position, At this time, the step position stored in the RAM 37 is also set to 125 at the same time. Therefore, when initialization is completed, the actual step position of the step motor 17 and the RAM 37
Therefore, the step position stored in the table will match. In the above initialization process, the step motor 17 is driven to rotate up to the maximum step position 125 by the number of steps more than necessary, but the step motor 17 needs to rotate to the minimum step position 0. It is also possible to carry out the initialization process by rotating the motor for several times.

When the initialization process is completed, the position of the step motor 17 is controlled to the required step position A in step 64. When the required step position A is fluctuating around MAX or MIN due to stepping out of the step motor 17, the required step position A is indicated by the curve P in FIG. 4 by performing initialization processing to adjust the step out. It will change as shown. Therefore, the routine then proceeds to steps 61 and 6.
After 2 proceed to step 63.

On the other hand, the required step position A is
If it continues to be MAX, the required step position A continues to be MAX even after the initialization processing. Therefore, at this time, the routine proceeds from step 68 to step 70, and the learning coefficient k is corrected.

FIG. 6 shows the correction processing of the learning coefficient k. Referring to FIG. 6, first, at step 80, the average step position is set.
S ₀ is loaded into CPU 34. This average step position S ₀
Is calculated in another routine shown in FIG. Referring to FIG. 7, first, at step 90, it is judged if the feedback control is being executed, and if the feedback control is not being executed, the processing routine is completed. On the other hand, if feedback control is in progress, the routine proceeds to step 91, where the average step position S ₀ of the required step position S during feedback control over a long time is calculated, and then the step
At 92, the average step position S ₀ is stored in a predetermined address of the RAM 37. During the feedback control, normally the required step position S moves up and down around 60 as shown by the curve P in FIG. 4, so the average step position S ₀ is almost 60. After that, when the required step position S starts to move up and down around 70 due to changes with time, for example, the average step position S ₀
Gradually approaches 70 and finally reaches 70. This average step position S ₀ represents the step position of the step motor 17 where the air-fuel ratio becomes the stoichiometric air-fuel ratio.Therefore, in the above case, when the step position of the step motor 17 becomes 70, the air-fuel ratio becomes equal to the stoichiometric air-fuel ratio. Become.

However, when the feedback control is not being performed, the required step position S is RO as shown in step 54 of FIG.
The value stored in M32 is used, and this value is determined on the assumption that the air-fuel ratio becomes the stoichiometric air-fuel ratio when the required step position S is 60, for example. Therefore, even if the required step position S is set to 60 so that the air-fuel ratio becomes the stoichiometric air-fuel ratio when the feedback control is not performed, the air-fuel ratio is no longer the stoichiometric air-fuel ratio when the average step position S ₀ is 70. Even in such a case, the learning coefficient k is corrected so that the air-fuel ratio becomes the stoichiometric air-fuel ratio when the required step position S is 60. That is, as shown in step 81 of FIG. 6, the learning coefficient k is obtained from the average step position S _0/60 , and this learning coefficient k is used in step 60 of FIG. That is, when the required step position S is set to 60 so that the air-fuel ratio becomes the stoichiometric air-fuel ratio when the feedback control is not being performed, step 60 in FIG.
Expressed as 60. Now, assuming that the average step position S ₀ is 70, k = 70/60 from step 81 in FIG. 6, so the required step position A is A = k · 60 = (70/60) · 60 = 7.
It becomes 0 and the air-fuel ratio becomes the theoretical air-fuel ratio. As described above, the learning coefficient k is provided so that the air-fuel ratio can be obtained in advance from the required step position S stored in the ROM 32 even if the flow rate characteristic of the flow rate control valve 16 changes with time.

When the learning coefficient k is corrected to a new learning coefficient k in step 70 of FIG. 5, the process proceeds to step 71 and the counters C, D
Is reset, and then in step 64, the step position of the step motor 17 is drive-controlled so as to reach the required step position A.

[Effects of the Invention] As described above, according to the present invention, when the step motor is out of step during engine operation, the out-of-step is immediately adjusted, so that good engine operation can be ensured. In this case, the present invention detects that the step motor is out of step without providing a special detecting means for detecting that the step motor is out of step, and further detects the actual position of the step motor. Since the position of the step motor is adjusted to the normal position without providing a special detecting means for doing so, the structure of the step-out adjusting device can be simplified.

[Brief description of drawings]

FIG. 1 is a block diagram of the invention, FIG. 2 is an overall view of an internal combustion engine, FIG. 3 is a flow chart for calculating a required step position, and FIG. 4 is a diagram showing changes in the required step position.
FIG. 6 is a flowchart for driving and controlling the step motor, FIG. 6 is a flowchart for correcting the learning coefficient k, and FIG. 7 is a flowchart for calculating the average step position. 14 …… fuel outlet, 14 …… LPG gas supply pipe, 16 …… flow control valve, 17,21 …… step motor, 19 …… bypass pipe, 20 …… idling speed control valve.

Claims (1)

(57) [Claims] 1. A means for obtaining a required step position according to an operating state of an engine, and a storage means for storing a current step position of a step motor, and a step based on the step position stored in the storage means. In an internal combustion engine in which the step motor is driven and controlled so that the step position of the motor becomes the required step position, the required step position is kept at a predetermined upper limit position or a lower limit position for a predetermined time or more. And the actual step of the step motor by driving the step motor to the maximum step position or the minimum step position when the required step position continues at the upper limit position or the lower limit position for a certain period of time or more. And a drive control means for matching the position with the step position of the step motor stored in the storage means. Out-adjusting device of the stepping motor for combustion engine.