JPS6318014B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an engine idle rotation speed control device, and more particularly to an idle rotation speed control device that is automatically adjusted as appropriate depending on the operating state of the engine.

[Conventional technology]

In recent years, there has been an increasing demand for lower fuel consumption in vehicles, and one way to achieve this goal is to improve fuel efficiency by lowering the idle rotation speed. However, if the engine's idle speed is set too low, the engine will suddenly be put under strain when the air conditioner compressor operates while the engine is idling, or when the steering wheel is suddenly operated in a vehicle with power steering, resulting in a so-called There was a fear that the engine would stall. In order to prevent this, a valve 4 is provided in the bypass line 3 that bypasses the throttle valve 1 provided in the intake pipe 2, as shown in FIG. An idle rotational speed control device that controls the idle rotational speed by controlling the opening and closing of an actuator 5 to change the flow rate of air passing through the bypass pipe 3 is well known. This is done by detecting the idle speed by the engine speed sensor 7 and comparing it with the target idle speed by the control circuit 6.
Based on the deviation, the actuator is driven to perform closed-loop control of the idle rotation speed to a constant target value.

[Problem that the invention seeks to solve]

The conventional idle speed control device as described above is useful in preventing engine stalling when the air conditioner is activated or when power steering is operated, but during closed loop control, the engine speed may vary by a few Hz as shown in Figure 2b. There was a problem with pulsation.
If this pulsation is severe, it may cause a surge in the engine speed and seriously impair the driving sensation.

The reason why pulsations as shown in FIG. 2b may occur when closed loop control is performed is as follows.

Taking as an example a case where the engine speed drops for some reason during closed-loop control, in such a case, the actuator 5 slightly opens the valve 4, increasing the amount of air intake into the engine. This will eventually lead to an increase in engine speed, but there are three steps before that happens.

The first step is when the valve 4 is opened and air flows into the intake manifold (not shown) until the internal pressure of the intake manifold rises above the internal pressure of the cylinder.

The second step is the step from when air flows into the combustion chamber until the fuel is combusted, where air flows into the combustion chamber due to the pressure difference.

The third step is until the fuel is combusted, torque is generated, and the engine speed increases. Even when torque is generated, the engine speed does not increase immediately because the crankshaft has a moment of inertia.

As described above, there is a slight time delay (response delay) between when a decrease in engine speed is detected and valve 4 is opened until the engine speed increases, so the engine speed reaches the target value. Even if the valve 4 is returned to its original state at about the same time, the engine speed will always rise above the target value due to the above-mentioned time delay. Since the engine speed has increased above the target value, even if the opening degree of the valve 4 is reduced, by the time the effect appears, the engine speed will fall slightly below the target value. This is the mechanism by which pulsation occurs.

Of course, if you always use open loop control instead of closed loop control, such pulsations will not occur, but
Instead, the engine speed gradually deviates from the target value due to changes over time.

However, as mentioned above, if the control is always closed loop control, pulsation may occur due to response delay.

In view of this situation, the present invention provides an improved idle rotation speed control device that can appropriately automatically adjust the idle rotation speed without causing a surge by performing closed loop control only occasionally without always performing closed loop control. is intended to provide.

[Means for solving problems]

According to the present invention, such an object includes an air flow rate control means for controlling the idle rotation speed by controlling the air flow rate supplied to the engine;
A driving means for driving the air flow rate control means, an engine rotational speed detection means for detecting the engine rotational speed, a driving state detection means for detecting the driving state of the vehicle, and a driving state detected by the driving state detection means. target value setting means for setting a value corresponding to a target idle rotation speed of the engine based on the engine rotation speed; a value corresponding to the current idle rotation speed detected by the engine rotation speed detection means; and a value corresponding to the target value. and a closed-loop control means for causing the drive means to drive the air flow rate control means based on the deviation to perform closed-loop control so that the idle rotation speed becomes the target idle rotation speed. In the idle rotation speed control device, the closed-loop control is performed at predetermined time intervals longer than the time at which a change in the air flow rate changed by the air flow rate control means appears as a change in the actual engine rotation speed. This is achieved by an idle rotation speed control device characterized by:

[Effect]

As mentioned earlier, when constant closed-loop control is performed,
Due to the response delay between when the air flow control valve starts operating and when the engine speed changes, pulsation as shown in Fig. 2b occurs, which causes surges, but in the present invention, Since closed-loop control is performed only at that moment at each predetermined time interval, the idle rotation speed is reset to the target value at each predetermined time interval, and pulsation occurs because closed-loop control is not performed during other periods. There's no room for that.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 3 is a sectional view and a block diagram of a control section showing one embodiment of the present invention. In the figure, 1 is a throttle valve, 2 is an intake pipe, 3 is a bypass pipe, 11 is an air flow control valve 12, 14 is an actuator unit using a step motor that drives the air flow control valve, and 15 to 27 are actuator parts thereof. This is a digital control unit for driving the step motor.
Further, the digital control section includes a step motor control circuit 15, a gate circuit 16, a deviation circuit 17, a clock pulse generator 18, a conversion circuit 19, a target value setting circuit 20, a frequency dividing circuit 21, an operating state detection circuit 22 to 25, and an analog Multiplexer 26, A/
It has a D converter (analog-digital converter) 27. In FIG. 3, diagonal lines / in the block diagram indicate that there are a plurality of signal transmission lines. An air flow control valve 11 is provided in the middle of a bypass line 3 that detours from the upstream side (left side in FIG. 3) to the downstream side of the throttle valve 1 provided in the intake pipe 2. The opening degree of the air flow control valve 11 is controlled by converting the rotation angle of a step motor 14 into a linear displacement via a rack gear 12 and a pinion gear 13. The output rotating shaft of the step motor 14 rotates in proportion to the number of pulses of a multiphase control pulse signal outputted from the control circuit 15. To increase the opening degree of the air flow control valve 11, the step motor 14 is rotated. In order to increase the number of control steps and reduce the opening degree, it is sufficient to reduce the number of steps. FIG. 4 shows the flow rate characteristic Qa (l/min) of the air flow rate control valve 11 with respect to the number of steps Ks of the step motor 14.

The rotational speed detector 25 shown in FIG. 3 shapes the waveform of an ignition signal from a distributor (not shown) to generate an engine rotational pulse having a frequency proportional to the engine rotational speed. The terminal 22 is connected to the power supply terminal of the electromagnetic clutch in order to know whether or not the air conditioning cooler compressor is being driven, and a signal "1" appears at the terminal 22 when the compressor is operating. The water temperature sensor 23 is a thermistor that detects the engine cooling water temperature as a change in its resistance value, and detects the warm-up state of the engine. The oil pressure sensor 24 converts oil pressure into voltage using a built-in pressure converter. Conversion circuit 1
9 has a gate and a register, and converts the engine rotation speed into a binary number. Analog multiplexer 26 connects water temperature sensor 23 and oil pressure sensor 2
This is for converting two analog voltages into binary numbers by one A/D converter 27 by alternately switching four output voltages. The target value setting circuit 20 is for setting a target value number for the step motor 14 corresponding to the operating condition of the air conditioner, the cooling water temperature, and the operating condition of the power steering. The control circuit 15 stores the target number of steps set in the target value setting circuit 20 in a single register, and converts it into a control pulse signal for the step motor. Further, the deviation circuit 17 compares the detected engine rotational speed and the target number of steps of the step motor 14, and constantly outputs the deviation. The gate circuit 16 temporarily applies the deviation signal of the deviation circuit 17 to the control circuit 15 in response to a trigger signal from the frequency dividing circuit 21 at predetermined time intervals. The target number of steps is adjusted.

The idle rotation speed control device constructed as described above operates as follows. Assume that the normal idle speed is set to 600 rpm. At this time, a control pulse signal is applied to the step motor 14 from the control circuit to set the target value to 600 rpm. Since this is open loop control, stable and smooth rotation can be obtained as shown in Figure 2a. Even if the idle speed of the engine is initially adjusted to 600 rpm, the idle speed will deviate from the target value over time due to changes in the air flow control valve 11 over time and the condition of the engine itself. By applying a trigger signal from the frequency dividing circuit 21 to the gate circuit 16 at predetermined time intervals, the deviation signal is input to the control circuit 15 and the target step number is determined.
Maintain an idle speed of 600 rpm by modifying Ks. This situation can be seen at 61 and 6 in Figure 5.
It is shown at 71 in the figure. When using the air conditioner, a load is applied to the engine, so as shown in Figure 5, the electromagnetic clutch is energized at the time to, and at the same time the target step number Ks is increased by Ksi, such as 62, to change the idle speed. is prevented. Similarly, when operating the power steering, a load is applied to the engine, so as shown at 70 in FIG. 6, the target step number Ks is increased in accordance with the increase in oil pressure to prevent fluctuations in the rotational speed. Furthermore, as shown in FIGS. 5 and 6, even when the target step number Ks is significantly modified, it is preferable to temporarily perform closed-loop control to modify the idle speed. FIG. 7 shows the target number of steps for setting the first idle rotation speed when the engine is warmed up. The step motor 14 is controlled by adding the target number of steps shown in FIG. 7 to the target number of steps for maintaining 600 rpm.

As mentioned earlier, when constant closed-loop control is performed,
Due to the response delay between when the air flow control valve 11 starts operating and when the engine speed changes, pulsation as shown in FIG. 2b occurs, which causes a surge, but in this example Since closed-loop control is performed only at predetermined time intervals and open-loop control is performed at other times, pulsation does not occur. In other words, in this embodiment, closed loop control is performed only at that moment at each predetermined time interval, so the engine speed is reset to the target value at each predetermined time interval, and during the period when closed loop control is not performed, the engine speed is reset to the target value at each predetermined time interval. Since everything is under open-loop control, there is no room for pulsation.

Of course, while open-loop control is being performed, there will be slight changes in the engine speed due to changes over time, but as long as the predetermined time intervals are set to appropriate values, no problems will actually occur.

Since the predetermined time interval is the time between the moments of closed-loop control and the moments of closed-loop control, setting it to a too short value will result in constant closed-loop control, which will result in pulsation. If you set the time too long, you will always be in open-loop control, and if you control the engine speed to the target value, the original aim will not be achieved, so it is necessary to choose an appropriate value that satisfies both. be. It is sufficient to set the appropriate value in a time longer than the time required for the change in air flow rate changed by the air flow rate control valve to appear as an actual change in engine speed.

In the above-mentioned embodiment, the control section was configured with a digital circuit, but the present invention is not limited to this. For example, it may be configured with an analog circuit, or it may be configured with an analog circuit for air-fuel ratio control or ignition timing control. It may be configured as part of a microcomputer system.

Note that the air flow control valve 11 corresponds to the air flow control means in the present invention, the step motor 14 corresponds to the drive means in the present invention, and the rotation speed detector 2 corresponds to the air flow control means in the present invention.
Reference numeral 5 corresponds to engine speed detection means in the present invention, electromagnetic clutch terminal 22, water temperature sensor 23, oil pressure sensor 24, etc. correspond to operating state detection means in the present invention, and target value setting circuit 20 corresponds to the engine rotation speed detection means in the present invention. The deviation circuit 17 corresponds to the deviation detection means in the present invention, and the frequency dividing circuit 21, gate circuit 16, control circuit 15, etc. correspond to the closed loop control means in the present invention.

Although the present invention has been described in detail with respect to specific embodiments above, it is clear to those skilled in the art that the present invention is not limited thereto, and that various embodiments are possible within the scope of the present invention. Will.

〔Effect of the invention〕

According to the present invention, there is no pulsation in the engine speed due to closed loop control, and a stable and smooth idle speed can be obtained.

Furthermore, since the air flow control means does not operate frequently, the durability of the air flow control means and the driving means for driving the air flow control means is improved.

[Brief explanation of the drawing]

Figure 1 is a diagram illustrating the configuration of a conventional idle rotation speed control device, Figure 2 a is a diagram showing temporal changes in idle rotation speed during open loop control, and Figure 2 b is a diagram showing idle rotation speed during closed loop control. FIG. 3 is a sectional view and block diagram showing the configuration of an embodiment of the present invention. FIG. 4 is a diagram showing the flow rate characteristics of an air flow control valve driven by a step motor. FIG. Figure 6 shows the change in the target step number when using the air conditioner, Figure 6 shows the change in the target number of steps when operating the power steering, and Figure 7 shows the target number of steps to obtain the first idle rotation speed. It is a diagram. 11... Air flow control valve, 14... Step motor, 15... Control circuit, 17... Deviation circuit, 2
0... Target value setting circuit, 22... Electromagnetic clutch terminal, 23... Water temperature sensor, 24... Oil pressure sensor,
25...Rotation speed detector.

Claims (1)

[Scope of Claims] 1. Air flow control means for controlling idle rotation speed by controlling the flow rate of air supplied to the engine, driving means for driving the air flow control means, and detecting the engine rotation speed. An engine rotation speed detection means, a driving state detection means for detecting the driving state of the vehicle, and a target value setting for setting a value corresponding to a target idle rotation speed of the engine based on the driving state detected by the driving state detection means. means, deviation detection means for detecting a deviation between a value corresponding to the current idle rotation speed detected by the engine rotation speed detection means and a value corresponding to the target value, and the drive means based on the deviation. An idle rotation speed control device having a closed loop control means for driving the air flow rate control means and performing closed loop control so that the idle rotation speed becomes the target idle rotation speed, the idle rotation speed being changed by the air flow rate control means. An idle rotation speed control device characterized in that the closed loop control is performed at predetermined time intervals that are longer than the time during which a change in air flow rate appears as an actual change in engine rotation speed.