Automotive vehicle vibration control arrangement and method

Abstract: In order to suppress vibrations which are produced by engine misfiring during idling, the load on an alternator is momentarily increased with a given time after the detection of a misfire.

Description: The present invention relates to automotive engines and more specifically to an arrangement and method which reduces vibration produced by sudden fluctuations in the engine output torque as set forth in the preamble parts of claims 1 and 7. In previously proposed engine torque output control arrangements, the torque fluctuations have been sensed at the crank shaft and in response to this the amount of current which passes through a field coil of an alternator associated with the engine, has been varied in a manner to vary the reverse torque which is applied to the engine crank shaft in an attempt to reduce the vibration producing effect of the output torque fluctuations. In this type of arrangement, the amount of current which flows through the field coil is related to the level of the voltage which is produced. However, with this arrangement as the variation in the inductance component of the alternator field occurs after a finite delay, it has been very difficult to actually establish the appropriate voltage and adequately control the torque fluctuations. Another proposal disclosed in JP-A-61-200333 has made use of a generator/motor arrangement which is directly connected to the engine crankshaft. In this arrangement the angular speed of the crankshaft has been sensed and the direct current (DC) supplied from the battery is converted into a multi-phase alternating current (AC) and supplied to the armature coil of the generator/motor device. In the armature coil the alternating current is converted to direct current and used to charge the battery. During this process, in the event that the angular speed of the crank shaft is sensed as being less than a predetermined reference value, the phase of the multi-phase current which is supplied to the armature coil is advance in accordance with the amount of difference between the instant angular speed of the crank shaft and the above mentioned reference value. On the other hand, in the event that the angular speed of the crank shaft is found to be greater than the reference value, the supply of multi-phase alternating current to the armature coil is controlled by a shut-off device. This arrangement is such that while sudden strong reversals in torque can be controlled, its effect is limited to situations wherein momentary increases in torque occur. Accordingly, in the case of a misfire wherein a momentary reduction in torque takes place, adequate control of the fluctuation cannot be expected and as a result, vibration containing a given frequency which tends to have a disturbing influence on the passengers of the vehicle; tends to transmitted to the vehicle chassis. From JP-A-63-70136, a system is known which can precisely detect the combustion condition of the engine. JP-A-61 256 042 shows an arrangement in which an electric motor is connected to a crank shaft of an engine to produce a torque in a direction to reduce an undesired engine vibration. The object of the present invention is to provide a simple and effective arrangement and method which can detect misfiring and counter the effect which tends to be produced by the vibration generated by the improper combustion. This object is solved by an arrangement having the features of claim 1 and by a method comprising the steps set forth in claim 7. The present invention, its advantages and details become even more clearly from the description of the preferred embodiment which are described under reference of the accompanied drawings in which: Fig. 1 is a schematic block diagram showing the basic arrangement of a first embodiment of the present invention; Figs. 2 and 3 are graphs showing in terms of engine torque and time, two examples of engine torque output characteristics; Fig. 4 is a timing chart showing a control pulse which is produced in accordance with the present invention; Fig. 5 is a graph showing an example of the operation of the present invention, in terms of engine output and time; Fig. 6 - 9 are examples of various vibrational wave forms; Fig. 10 is a schematic block diagram showing the basic arrangement of a second embodiment of the present invention; and Fig. 11 is a model showing an arrangement wherein an engine is mounted on a vehicle chassis. Fig. 1 shows a first embodiment of the present invention. In this arrangement an engine block 1 supports an alternator 2. A drive connection is established between a crank pulley 3 and an alternator pulley 4 by way of suitable belt 5. A crank angle sensor 6 is arranged to sense the rotational characteristics of the engine crank shaft. The alternator 2 includes three rotatable armature coils L1 to L3 and a field coil L4. The field coil L4 is connected to a battery 7. A controller 10 is operatively connected with switches 14 - 16 which are in turn arranged to selectively connected output terminals 11 - 13 of the above mentioned armature coils L1 - L3, with a three phase inverter 20. The controller 10 is further connected with the battery 7 and crank angle sensor 6 by signal lines 18 and 19, respectively. A three phase flow rectifier 21, an accumulator 22, and a step-up booster 23 are connected in the illustrated manner. A signal line 17 provides an operative connection between the controller 10 and the switches 14 - 16; a signal line 25 connects the three phase inverter 20 with the controller 10; and a signal line 26 provide a connection between the controller 10 and accumulator 22. A switch 28 enables a selective connection between the three phase rectifier 21 and the accumulator 22. A switch 29 provides a selective connection between the three phase inverter 20 and the step-up booster 23. The switches 28, 29 are operatively connected with the controller 10 via signal line 27. A combustion pressure sensor 31 is operatively arranged with the combustion chamber 30 of the engine and arranged to output a signal along line 32 to the controller 10. It should be noted that in the case of a multi-cylinder engine, each cylinder is provided with a combustion pressure sensor to enable the detection of any abnormal combustion and the introduction of a momentary reduction in engine output torque a predetermined short time after such a detection. By way of example, the pressure sensor 31 may take the form of piezoelectric element which is sandwiched between the cylinder head and a spark plug and thus subject to changes in stress which vary with the pressure which develops within the combustion chamber 30. The basic operation of the above described arrangement is such that when the engine is running properly, the belt 5 transfers rotational energy from the engine crank shaft pulley 3 to the alternator pulley 4 and the electrical power which is produced by the alternator 2 and which has a predetermined voltage, is supplied to the battery 7. During the above operation, the air/fuel charges in the combustion chamber are ignited and resulting torque is applied to the engine crankshaft. Fig. 2 shows the pulse-like nature with which torque is generated under such circumstances. Viz., when the engine is running normally and without the occurrence of an abnormal combustion, there is very little cycle to cycle variation in the torque impulse generation. However, in the case that a misfire, partial misfire or the like type of improper combustion occurs, the peak pressure which develops in the combustion chamber in question is greatly reduced. By way of example, as shown in Fig. 3 at a time T, a misfire takes place and the engine torque M which is produced in response to this abnormal combustion, assumes a negligible value and creates a relatively large gap between impulse peaks. This gives rise to vibration having a frequency which tends to be close to the natural frequency of one of the arrangement which suspends the engine on the chassis or the chassis suspension arrangement. Merely by way of example, assume that, as shown in Fig. 11, when a four cylinder engine is idling it produces a frequency in the region of 20Hz; the predominant frequency produced by the engine is so called secondary vibration; engine suspension arrangement in this instance has a natural frequency of about 14Hz while the chassis suspension system a natural frequency of about 5Hz. In the event that one of the cylinders (merely by way of example) begins to misfire due to plug failure or the like, the frequency with which the misfires occur tends to be about 5Hz. The vibration which results from the misfiring therefore has a frequency which is close to the natural frequency of the chassis/vehicle suspension system. This frequency tends to undergo little attenuation by the engine suspension arrangement and thus is transmitted to the chassis. Generally speaking, the vehicle suspension system exhibits the weakest resistance to motion in the roll direction. Accordingly, in the above mentioned case, as the frequency with which the impulses produced by this "rough idling" vibration tends to coincide with the natural frequency of the vehicle suspension arrangement, rolling of the vehicle tends to be excited by the same. Of course misfiring is not limited to one or more specific cylinders and in the event of poor air-fuel ratio control which permits excessively lean mixtures to be fed to the cylinders of the engine, sporadic misfiring can occur. However, the possibility that the vibrations produced by such misfiring will exhibit a frequency in the 5 - 7Hz region which is close to one of the natural frequencies of the engine and/or vehicle suspension arrangements, the chances of the same inducing a somewhat amplified unpleasant result exists. In accordance with the instant embodiment, in response to the output of the pressure sensor 31 indicative of the misfire and the signal from the crank angle sensor 6, the controller 10 responds by determining the degree of the combustion abnormality and momentarily increases the amount of current which is supplied through line 18 to field coil L4 from the battery 7. As shown in Fig. 4, the timing of this current flow increase is such that it is induced to occur a predetermined time T1 after time T. The time T1 is selected to coincide with half a cycle of the natural frequency of the engine suspension system. This therefore tends to produce a vibration which exhibits a phase which is the reverse of that which tends to be produced by the misfire(s). As shown in Fig. 5, at time T1 following the misfire, an engine torque S having a phase which is essentially the reverse of that produced by the misfire, is generated. The torque S is such as to cancel the vibration which tends to be transmitted to the vehicle chassis and induce the aforementioned rolling. The above described control is used only during engine idling and is not executed when the vehicle is running (viz., being accelerated. decelerated, undergoing cruising or the like). With the instant embodiment, the power which is produced by the rotation of armature coils L1, L2 and L3 is, under the conditions illustrated in Fig. 1, temporarily supplied from the 3 phase rectifier 21 via the switch 28 to the accumulator 22. Following this, switches 14, 15, 16 and 29 are closed (ON) while switch 28 is opened (OFF). Under these conditions the power which is stored in the accumulator 22 is fed via the booster 23 to the 3 phase inverter and returned to the armature coils L1, L2 & L3. In accordance with the operation described above, the power loss is reduced to zero and the detrimental effect on the fuel economy of the engine totally negated. Figs 6 and 7 show experimental data which depicts two examples of vibration generation which are produced under identical engine operating conditions, and the effect of the present invention thereon. The engine in this case is a four cylinder engine. As will be appreciated Fig. 6 shows an example wherein the vibration acceleration amplitude P1 which is produced by normal engine operation is large (in the above mentioned roll direction) and is interrupted by a misfire induced change P3. On the other hand, Fig. 7 shows the situation wherein a small amplitude P2 is interrupted by a misfire at P4. As shown, after time T1 the effect of the invention is such as to suppress any notable fluctuations and negate the effect of the misfires. Figs. 8 and 9 show similar data. As will be noted, in all of the above instances suppression of vibrational influence on the rolling of the vehicle occurs following the expiry of time T1. It will be noted that with the disclosed embodiment, by increasing the amount of electrical power produced one engine revolution after a misfire, it is possible to achieve a 5db reduction in vehicle vibration. A second embodiment of the present invention is shown in Fig. 10. In this arrangement the alternator 2 is connected with a load 35 (in this instance a rear window de-fogger heating wire arrangement) by way of transistor TR1. Controller 10 is arranged to be responsive to the engine crank angle and to render the transistor TR1 conductive with a predetermined rotational angular delay with respect to the ignition timing in the event that a misfire is detected. As will be noted, the load which is used in the second embodiment is not limited to the above mentioned de-fogger and can take the form of any suitable load which is available. For further disclosure relating to the manner in which the presence or absence of a misfire can be detected, reference may be made to JP-A-63 070 136. This document discloses a technique of sampling the pressure in the combustion chamber and determining a crank angle at which the total effect of the sampled pressures could be deemed have instantly acted (analogous to the center of gravity of a mass). This technique permits the discrimination between the motoring pressure and combustion induced pressure and thus enables misfiring to be accurately identified during idling.

Claims: A vibration control arrangement for an automotive vehicle which has an engine (1) including a combustion chamber (30), comprising first means (31) for sensing the combustion pressure in the combustion chamber and second means (10) for detecting an improper combustion in the combustion chamber by monitoring the sensed combustion pressure, said improper combustion being caused by misfire in the combustion chamber and causing variation of the engine output torque and thus vibration of the vehicle, WHICH IS CHARACTERIZED IN THAT third means (2, 7, 10, 18) is provided which momentarily reduces the engine output torque at a predetermined time (T1) after said second means has detected the improper combustion, said predetermined time being selected with respect to the phase of vibration of the vehicle caused by the misfire. A vibration control arrangement as claimed in Claim 1, further CHARACTERIZED IN THAT said predetermined time (T1) is selected to coincide with half a cycle of the natural frequency of the vehicle. A vibration control arrangement as claimed in Claim 1, further CHARACTERIZED IN THAT said predetermined time is the time when the engine (1) has made one revolution after the misfire. A vibration control arrangement as claimed in Claim 1, further CHARACTERIZED IN THAT said third means comprises: an alternator (2) driven by said engine (1); and fourth means for causing said alternator to produce a large electric power at said predetermined time. A vibration control arrangement as claimed in Claim 4, further CHARACTERIZED IN THAT said fourth means comprises: an electrical load; and switch means (TR1) for temporarily connecting said alternator (2) to said electric load at said predetermined time in a manner which increases the load applied to said engine. A vibration control arrangement as claimed in Claim 4, further CHARACTERIZED IN THAT said fourth means comprises: a crank angle sensor (6); a controller (10) operatively connected with said crank angle sensor and a battery (7) which is operatively connected with said alternator; a three phase inverter (20); a three phase rectifier (21), said three phase rectifier and said three phase inverter being selectively and alternatively connectable to armature coils (L1, L2, L3) of said alternator via a plurality of first switches (14, 15, 16), said first switches being operatively connected with said controller; an accumulator (22) for storing electrical energy; and a booster circuit (23) for increasing the voltage of the electrical energy supplied thereto, said booster circuit being serially connected with said accumulator, said accumulator being operatively connected with said three phase rectifier by way of a second switch (28), said booster circuit being operatively connected with said three phase inverter by way of a third switch (29), said second and third switches being operatively connected with said controller to be selectively opened and closed thereby. A method of negating the vibration inducing effect of engine misfiring on the vibration of a vehicle, comprising the steps of: sensing the pressure in a combustion chamber of said engine during engine idling; detecting a misfire in said combustion chamber; characterized by momentarily increasing the load on the engine in a manner to reduce the amount of torque which is produced a predetermined time after the detection of the misfire, said predetermined time being selected with respect to the phase of vibration of the vehicle caused by the misfire.

Inventors: KADOMUKAI YUZO TSUKUBA-HAUSU -, MAEDA RYOICHI, YAMAKADO MAKOTO NIIHARI-RYO NO, KADOMUKAI, YUZO, TSUKUBA-HAUSU 1-407 NO. 2625-3, MAEDA, RYOICHI, YAMAKADO, MAKOTO, NIIHARI-RYO, NO. 3602
Applicants: HITACHI LTD, NISSAN MOTOR, HITACHI, LTD., NISSAN MOTOR CO., LTD.
Application year: 1990
Main classification: F02P11
IPC codes: F16F15, F02B77, F02D29, F02D45, B60G17