JPH04350337A - Vehicle body vibration reducing method - Google Patents

Abstract

PURPOSE:To reduce vibration of a vehicle body positively by detecting the combustion state of each cylinder, and performing the control of changing engine load at the timing of suppressing the vibration of the vehicle body in case a specific cylinder is changed exceeding the specified value compared to the average combustion value of other cylinders. CONSTITUTION:There is provided a crank angle signal generating device 2 for generating two block pulses and cylinder discrimination signals within + or -720 deg./4n (n: the number of cylinders) with an angle for the maximum combustion torque placed in between, synchronously with a crank angle. Engine speed is detected by an engine speed detecting device 3 using these block pulses, and the combustion state cylinder by cylinder is judged by an arithmetic processing unit 4 from the fluctuation of the engine speed to control a load torque generating device 5 such as an alternator. In case there is a cylinder of strong combustion, an alternator field current is changed in the direction and timing of weakening the explosion torque of this cylinder so as to generate load torque to a crankshaft and thereby to reduce the vibration of a vehicle body caused by uneven combustion.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reducing vehicle body vibration of an automobile, and in particular, the 1/2-order vibrations (0.
The present invention relates to a vehicle body vibration reduction method for reducing 5th-order vibration).

0002

2. Description of the Related Art No prior art has been proposed that discloses a technical means for reducing the 0.5th order vibration of engine rotation. Furthermore, as a similar technology, there is an engine torque control device (Japanese Unexamined Patent Application Publication No. 63-212723) previously proposed by the present applicant.
No.). This torque control device reduces torque fluctuation itself caused by combustion pressure fluctuation for each cylinder of the engine.

0003

The former method of the prior art mentioned above deals only with irregular and relatively large drop in combustion due to irregular combustion. However, as will be discussed in detail later, even if combustion is normal, due to uneven fuel supply to each cylinder, combustion may be stronger in one cylinder than in the other cylinders, or the combustion state may be constantly different. Therefore, combustion variations occur, with one combustion cycle being one cycle. Therefore, when the engine vibrations generated coincide with the period of the engine's natural vibrations, resonance occurs, causing constant vehicle body vibrations that cause discomfort to the operator.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for reducing vehicle body vibrations that can reliably reduce vehicle body vibrations caused by non-uniform combustion that occurs regularly.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention detects the rotational speed of the engine from the output of a crank angle sensor, and further detects the combustion state of each cylinder based on fluctuations in the rotational speed. Find out. If there is a cylinder with weak combustion, the alternator field is adjusted so that the load on the alternator increases after 1/2 period of the engine roll natural period or 1/2 period of the carb roll natural period from the explosion top dead center of that cylinder. Either by controlling the magnetic current or by controlling the alternator field current to weaken the explosion torque of the cylinder that explodes 360 degrees after the cylinder with weak combustion, and if there is a cylinder with strong combustion, The alternator field current is changed in a direction and timing that weakens the explosive torque. Furthermore, the timing for applying the engine load may be a combination of any of the above timings.

[0006]

[Operation] When the alternator load is increased after 1/2 period of the engine roll natural period from the explosion top dead center of the cylinder with weak combustion, the generated 1/2-order vibration of the engine is directly suppressed by the increase in the alternator load. In addition, by weakening the explosion torque of the cylinder with weak combustion and the cylinder whose top dead center of combustion is shifted by 360 degrees, the engine vibration is driven at the cycle of the primary vibration, so resonance is suppressed by shifting from the 1/2 vibration. It will be done. Furthermore, if the alternator load is controlled to weaken the explosion torque of the cylinder with strong combustion, the occurrence of vibration itself can be suppressed.

[0007]

[Examples] The present invention will be explained below with reference to Examples. FIG. 2 is a block diagram showing the overall configuration of a device to which the present invention is applied, in which the 0.5-order vibration detection section is synchronized with the crank angle, and the angle at which the combustion torque is maximum is ±720/4n degrees (however, It consists of a crank angle signal generator 2 that generates two interval pulses and a cylinder discrimination signal (n is the number of cylinders), and a rotational speed detector 3 that detects the rotational speed from the interval pulses, and further detects fluctuations in the rotational speed. It consists of an arithmetic processing unit 4 that determines combustion for each cylinder, and a load torque generator 5 that generates a load torque to the crankshaft of the engine 1 in synchronization with a control signal from the processor 4. Here, the engine 1 may be a diesel engine or a gasoline engine. It is assumed that the load torque generating device 5 is an alternator. In this case, load torque control can be performed by controlling the field current or generated current, but here we will control the field current, which has a small current, and its configuration is shown in Figure 9, with the inductance of the field coil The deterioration of the response due to the large voltage will be dealt with by increasing the applied voltage and flowing a current of about 4 A for about 20 ms.

The operation will be explained below. Normally, when engine speed is plotted against the time axis, it is accelerated each time each cylinder explodes, so m is calculated by dividing the crank angle of 720 degrees by the number of cylinders n.
The vibration waveform has a peak every =720/n degrees. If there is no variation in the combustion state among the cylinders and there is no load variation, the height of each peak will be the same.

However, fuel, which is one of the factors that determines combustion, is not always distributed in the same amount to all cylinders, and in gasoline engine carburetors, the shape of the intake manifold may result in less fuel in a particular cylinder. . Further, even when distributing fuel by injection, variations in the initial characteristics of the injector and the flow characteristics depending on changes over time occur, and the amount of fuel in a particular cylinder may decrease. Even in diesel engines, there are variations in the flow characteristics of the injection pump and injector, so the amount of fuel in a particular cylinder may become low. These problems can be addressed to some extent in gasoline engines by controlling the injection amount for each cylinder, but in diesel engines, electronic control is difficult, so fuel adjustment is done by combining an injection pump and injector. The problem has been that the only way to deal with the problem is to repeat the process of looking at the flow characteristics, changing the combination, and readjusting.

[0010] As described above, variations in fuel cause variations in combustion, and a phenomenon occurs in which combustion is always strong or weak in only a particular cylinder. In this case, since the torque generated in the engine varies, the engine is vibrated in the roll direction, and the rotational speed also fluctuates irregularly. This situation is shown in FIGS. 3(a) to 3(c) as changes in engine rotational speed over time. Engine speed is 750r with 4 cylinders
pm (period 80ms, frequency 12.5Hz),
Since one cylinder explodes once in two cycles, the excitation cycle for specific cylinders with different explosive forces is 160 ms, and the frequency is 6.
It becomes 25Hz. This frequency is exactly close to the engine's roll eigenvalue, so the engine resonates in the roll direction. Furthermore, if it is an FR vehicle, the resonance will also occur in the vehicle body roll direction, resulting in the worst ride comfort for the driver. Even if resonance is eliminated by increasing the number of cylinders n or changing the engine mounting method, the ride quality will still deteriorate due to periodic vibrations of the engine in the roll direction.

In the present invention, in order to suppress this vibration,
The arithmetic processing unit 4 executes the processing shown in FIG. This process is
When the number of cylinders is n, it is activated every m=720/n degrees. The rotational speed detection device 3 detects the instantaneous speed at that time from the output pulse width of the crank angle signal generator 2 generated every m degrees, so in step 101, the detected speed every m degrees is taken in and the adjacent values are Let be NT and NB. In step 102, the change in velocity for each m degree α=NT−
NB is calculated, and in step 103, the cylinder discrimination signal output from the crank angle signal generator 2 is taken in. Then, in step 104, the results of steps 102 and 103 are stored in a table for each cylinder in the backup memory 6. Once the above steps 101 to 104 have been executed a specified number of times for all cylinders (steps 105 and 106)
, proceed to step 107. Here, the purpose of performing the specified number of times is to remove the influence of primary fluctuations by measuring the rotational speed variation α several times and finding the average. In step 107, it is checked whether vibration reduction control is already being performed at that time. If it is, in step 108, the rotation speed change α before and after the main control is checked, and in step 109, the effect of the control is If it is determined that the pulse width Pw of the control signal described later is insufficient, control is continued by increasing the pulse width Pw of the control signal, which will be described later, by a constant value ΔPw within the range of Pw≦[maximum value of Pw that has been set].

If it is determined in step 107 that control is not in progress, the rotational speed change α for each cylinder is extracted from the α table in the backup memory 6 for the prescribed number of times in step 106, and the average value thereof is determined. In steps 111 and 112, the presence or absence of a cylinder with weak combustion or a cylinder with strong combustion is checked from the value of the rotation speed change α for each cylinder. As a result, if there is a cylinder with weak combustion, control timing t1 or t2, which will be described later, is set in step 113, and if there is a cylinder with strong combustion, control timing t3 is set in step 114,
At that timing, the pulse width Pw is sent to the load torque generator 5.
outputs a control signal.

FIG. 3 shows fluctuations in engine speed and step 1.
The timings of the control signals output at 13 and 114 are shown in comparison. Figure (a) shows that when there is a cylinder in which combustion is determined to be weak, the center of the load torque comes after a time t1 corresponding to 1/2 cycle of the engine roll eigenvalue from the explosion top dead center of that cylinder. This is a case where control is performed as follows. As shown in FIG. 7, this control amount C (pulse width Pw) changes depending on the amount of drop in combustion, engine speed, engine load, fuel temperature, alternator temperature, etc., but this drop is based on the average value in step 110. Since it is detected based on the combustion rate, even if there is occasionally no drop in combustion, if it is on average, the same control amount will be used. This is because when the engine is resonating in the roll direction, it is more effective to control it by always applying the same load, so if control is performed at this timing, the engine will return to its original position even if it vibrates once. When it returns, a force in the opposite direction is applied, which prevents vibration.

FIG. 3(b) shows that when it is determined that combustion in a particular cylinder is weak, a load torque is generated in the direction of weakening the explosion torque of the cylinder after a time t2 corresponding to 360 degrees from that cylinder, and the combustion torque is reduced by 1/2. This is a case where the next-order vibration is changed to the first-order vibration. In this case, the vibration period becomes faster, so the amplitude of vibration becomes smaller, and what used to resonate no longer resonates. Based on this principle, in the case of 4 cylinders or more, 3
As long as the vibration is not limited to 60 degrees and the vibration order is increased, it may be applied any number of times, but it is preferable that the frequency of occurrence of the load torque is as low as possible because the engine load can be reduced. This method is the same as the control method described above in that the control amount is determined depending on the drop amount, engine speed, engine load, fuel temperature, alternator temperature, etc.

FIG. 3(c) shows a case where it is determined that combustion in a certain cylinder is strong. The control timing t3 at this time is determined so as to generate a load torque in accordance with the explosion of the relevant cylinder, thereby directly weakening the explosive force of the strongly combusting cylinder and suppressing the 1/2-order vibration. Learning control is performed by storing the control amount determined in the above method in a backup memory.

[0016] The combustion state was detected by calculating the change α=NT-NB from the rotational speed detected every m degrees, but when the time for rotating m degrees is T, the acceleration is α/T. You can also check the combustion status by looking at the . However, since the present invention deals with vibrations when there is no speed change such as in an idling state, the effect does not change even if the combustion state is viewed by α with T=constant. In addition, the timing of applying the engine load is based on the engine roll natural period described above.
It may be a combination of 1/2 period of the cab roll natural period or 360 degrees at the crank angle.

FIG. 4 shows actual measurements of engine rotational speed, engine vibration, floor vibration, rotational speed fluctuation value, and load torque control signal when the method of FIG. 3(a) is applied when there is a cylinder with weak combustion. Regarding the engine rotational speed and floor vibration, the solid line shows the case where the control according to the method of the present invention is not performed, and the dotted line shows the case where the control is performed. This example also shows that floor vibrations are significantly suppressed.

In this embodiment, a rotational speed sensor synchronized with the crank angle was used as the 0.5th order vibration detection section.
As shown in FIGS. 5 and 6. As the 0.5th order detection means, there is a method of detecting directly from engine vibration as shown in Fig. 5(a), a method of detecting from the average in-cylinder pressure for each cylinder as shown in Fig. 5(b), and a method of detecting from the floor vibration as shown in Fig. 5(c). A method of detecting from the engine rotation speed as shown in Fig. 5(d), a method of detecting from the voltage fluctuation of the generated current terminal (B terminal) of the alternator as shown in Fig. 6(a), and a method of detecting the generated current IL as shown in Fig. 6(b). You can also look at it from the perspective of fluctuations.

Furthermore, although an alternator is used as the load torque generating device, the present invention is not limited to this.
As shown in FIG. 8, the auxiliary equipment may be a power steering motor, a water pump, an oil pump, or an air conditioner compressor as long as it is driven in synchronization with the crankshaft and can generate a load.

[0020]

According to the present invention, it is possible to reduce vehicle body vibrations caused by stationary causes such as combustion variations among engine cylinders.

[Brief explanation of the drawing]

FIG. 1 is a flowchart of a control procedure according to an embodiment of the present invention.

FIG. 2 is a block diagram showing the overall configuration of an apparatus to which the present invention is applied.

FIG. 3 is an explanatory diagram of control signal output timing in the process of FIG. 1;

FIG. 4 is an explanatory diagram of control effects according to the present invention.

FIG. 5 is an embodiment diagram of a 0.5-order detection means.

FIG. 6 is an example diagram of a 0.5-order detection means.

FIG. 7 is a diagram showing an example of calculating the control amount C.

FIG. 8 is a diagram showing torque generated by an auxiliary machine.

FIG. 9 is a field control system diagram.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1...Engine, 2...Crank angle signal generation device, 3...Rotational speed detection device, 4...Arithmetic processing device, 5...Load torque generation device.

Claims (9)

[Claims] 1. A combustion state detection means for detecting the combustion state of each cylinder of an automobile engine, and a control means for controlling the magnitude of a load on the engine;
The control means checks the combustion state of each cylinder detected by the combustion state detection means, and if the combustion in a particular cylinder is weaker or stronger than the average combustion value of other cylinders by a certain value or more, the control means controls the combustion state of the cylinder. A method for reducing vehicle body vibration, characterized by outputting a control signal that changes engine load at a timing that suppresses vehicle body vibration caused by output differences between other cylinders. [Claim 2] When combustion in the specific cylinder is weak,
Claim 1, wherein the control signal is a signal that increases the engine load at a timing 1/2 period after the engine roll natural vibration from the explosion top dead center of the cylinder.
The vehicle body vibration reduction method described. 3. When combustion in the specific cylinder is weak,
2. The vehicle body vibration reduction device according to claim 1, wherein the control signal is a signal that increases the engine load at a timing 1/2 cycle after the cab roll natural vibration. 4. When combustion in the specific cylinder is weak,
2. The vehicle body vibration reduction method according to claim 1, wherein the control signal is a signal that controls the engine load in a direction that weakens the explosion torque of the cylinder that is fired 360 degrees after the cylinder in question. 5. When combustion in the specific cylinder is weak,
A claim characterized in that the control signal is a signal that increases the engine load at a timing that is a combination of any two or three of the timings for controlling the engine load according to claims 2 to 4. 1. The vehicle body vibration reduction method described in 1. 6. When combustion in the specific cylinder is strong,
2. The vehicle body vibration reduction method according to claim 1, wherein the control signal is a signal that controls the engine load in a direction that weakens the explosion torque of the cylinder at the same timing as ignition of the cylinder. 7. The engine load according to claim 1, wherein the engine load is an alternator, and the control signal controls the engine load by changing a field current of the alternator. The vehicle body vibration reduction method described. 8. The vehicle body vibration reduction method according to claim 1, wherein the combustion state detection means detects the combustion state of each cylinder of the engine from fluctuations in engine rotational speed. . 9. The magnitude of the load control by the control signal is changed according to the difference in combustion between the specific cylinder and other cylinders. The vehicle body vibration reduction method described in .