Apparatus and a method for detecting the valve timing of electromagnetic engine valves

Abstract: In an apparatus and method for detecting the valve timing of an electromagnetic valve assembly (1) a vibration sensor (20) is provided to sense a vibration generated by the valve assembly as it reaches the fully open or fully seated position. The data generated are transmitted to a comparator device (32, 42) for comparison with a threshold value which may be fixed or varied according to vibration data having a value which, when it exceeds a threshold value, indicates that the valve is fully open or seated.

Description: The present invention relates to an electromagnetically operated valve for an internal combustion engine and more particularly to an apparatus and a method of detecting opening and closing time of the electromagnetically operated valve. Techniques whereby intake and exhaust valves of internal combustion engines are electromagnetically operated and their opening and closure timings are electronically controlled, have been developed. The electromagnetically operated valve has an advantage in that valve opening and closure timings can be established over a wide range and can be selected properly in accordance with engine operating conditions, however, it has a disadvantage in that the valve is accelerated by the electromagnetic force of solenoids and the biasing force of the spring and as a result a large impact occurs when the valve seats on a valve seat or when the valve opens fully. To overcome this disadvantage, techniques such as retarding the valve speed immediately before the valve is seated on the valve seat or fully open, have been developed. For example, Japanese Patent Application Laid-open No. TokuKai-Hei 7-332044 discloses a technique wherein a piezoelectric element is fixedly disposed at a position receiving pressure from an armature or an interconnecting member integrally moving with the armature to detect a valve position based on the change of an output characteristic of the piezoelectric element. In this technique, the valve position is detected by applying pressure directly on the piezoelectric element. There is a problem of endurance of the piezoelectric element. To improve endurance over the piezoelectric sensor a contactless sensor such as an eddy current position sensor has been proposed. However, contactless sensors can detect a relative displacement of the valve but have a disadvantage that it is difficult, due to the effect of noise contained in output signals of the sensors, to accurately detect an instant when the valve is completely closed or when the valve is fully open. With the above described problem in mind, it is an object of the present invention to provide an improved valve opening and closing time detecting apparatus for an electromagnetically operated valve capable of accurately detecting a time of a valve fully open or completely closed. By detecting an accurate time, it becomes possible to control more correctly the velocity of the valve when the valve is seated on the valve seat or is fully open. The reader is referred to US-A-4544 986 at column 3 line 26 to column 4 line 30. Accordingly the present invention provides apparatus according to claim 1. The threshold value may be a predetermined fixed value, or varied in accordance with a magnitude of said vibration, or updated every specified revolution number of said engine. The magnitude of said vibration may be taken as a peak value of said vibration, or a mean value of magnitudes of said vibration when said valve is away from said open position or said seated position. According to a second aspect of the invention there is provided a method of detecting the timing of an electromagnetically operated valve in an internal combustion engine according to claim 9. An apparatus and method for detecting valve timing in an electromagnetically operated valve mechanism will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a schematic block diagram showing a valve opening and closing time detecting circuit according to a first embodiment; Fig. 2 is a sectional side elevation of an electromagnetically operated valve mechanism; Fig. 3 is an explanatory view showing a relationship between an output of a lift sensor and an output of a vibration sensor; and Fig. 4 is a block diagram showing a valve opening and closing time detecting circuit according to a second embodiment of the present invention. An electromagnetically operated valve 1 is mounted on a cylinder head 2 of an engine. A valve 4 (intake or exhaust valve) has a valve stem 4b supported to reciprocate in a valve stem guide 3 in the cylinder head 2. A valve opening solenoid 5 and a valve closing solenoid 6 are provided. The valve opening solenoid 5 and the valve closing solenoid 6 are disposed to act in opposition. In the electromagnetically operated valve 1, the valve opening solenoid 5 is accommodated in a yoke 7 which is mounted on the cylinder head 2. A lift adjuster 8 is mounted on the yoke 7 to adjust the amount of lift of valve 4. A yoke 9 is connected with the lift adjuster 8 and accommodates the valve closing solenoid 6. The yoke 9 is connected at an upper portion with a case 11 that serves to guide an armature 17 in the axial (vertical) direction and at the same time accommodates an eddy current type lift sensor 10. A valve closing spring 13 is accommodated inside of the valve opening solenoid 5 and is biased to press a valve head 4a of the valve 4 on to a valve seat 12. The valve closing spring 13 is interposed between a retainer 15 which is connected through a cotter pin 14 with the end of the valve stem 4b and a cylindrical spring holder formed around the valve stem guide 3 on the cylinder head 2. A shim 16 is provided for adjusting a clearance at the top of the valve stem 4b. In a space formed on the inner periphery of the lift adjuster 8, there is provided a disk-like armature 17 for actuating the valve 4. Also, an armature stem 17a is formed integrally with the armature 17 in the centre of the armature 17 and the armature stem 17a is mounted for reciprocation in an armature stem guide 18 which is press-fitted to a cylindrical portion projecting down from the case 11. A valve opening spring 19 is located around the outer periphery of the cylindrical portion and is biased to urge the valve head 4a away from the valve seat 12. When both the valve opening solenoid 5 and the valve closing solenoid 6 are deenergised, the armature 17, while it is in contact with the shim 16, is sustained in a middle position where the biasing force of the valve closing spring 13 is balanced with that of the valve opening spring 19. The upper tip of the armature stem 17a tapers to a needle-shape and acts as a moving target 17c of the lift sensor 10. Vertical travel of the target 17c is detected by the lift sensor 10 as indicative of a lift amount of the valve 4. The electromagnetically operated valve 1 is controlled by a control apparatus (not shown). The control apparatus calculates valve opening and closing time of intake or exhaust valves of each engine cylinder based on vehicle operating conditions such as; engine speed, accelerator pedal angle, crank angle indicator pulses, coolant temperature, and other miscellaneous data. The control apparatus then outputs driving signals to the electromagnetically operated valve 1. For example, when intending to operate the valve 4 from a closed position, first the valve closing solenoid 6 is deenergised and then the value opening solenoid 5 is energised at a specified timing. A force is generated in the valve opening solenoid 5 to attract the valve 4 through the armature 17 in the direction of the valve opening solenoid 5. The armature 17 passes the middle position where the biasing force of the valve closing spring 13 is balanced with that of the valve opening spring 19 and then stops in contact with the yoke 7. Thus, the valve 4 reaches a maximum lift position (fully open position) and the valve opening operation finishes. When intending to close the valve 4 from an open position, the valve opening solenoid 5 is deenergised and the valve closing solenoid 6 is energised at a specified timing. An attractive force is generated in the valve closing solenoid 6 to attract the armature 17 in the direction of the valve closing solenoid 6. The armature passes the middle position where the biasing force of the valve closing spring 13 is balanced with that of the valve opening spring 19 and then stops in contact with the yoke 9. At this time, a specified clearance is formed between the armature 17 and the shim 16 and the valve head 4a is therefore pressed on the valve seat 12 by the biasing force of the valve closing spring 13. Generally, in order to alleviate impacts when the armature 17 comes into contact with the yokes 7, 9 or when the valve 4 is seated, the electromagnetically operated valve mechanism is constituted such that the armature velocity is retarded by controlling a current passing through the valve opening solenoid 5 or the valve closing solenoid 6 immediately before reaching the maximum lift position or the seating position. However, if such control relies solely on the output from the lift sensor 10, it is difficult to accurately detect the time at which the valve is fully open or fully closed. This is due to dispersion or aging of related components. Therefore, an effective velocity control of the armature 17 can not be expected. To solve the problem, the electromagnetically operated valve mechanism according to the present invention has introduced a vibration sensor 20 disposed on the cylinder head 2 in the neighbourhood of the valve 4. The vibration sensor 20 is for detecting an accurate time of valve fully open or closed. Output signals of the vibration sensor 20 are processed in a valve opening and closing time judging circuit 30 as shown in Fig. 1, from which signals indicative of valve opening and closing times are output to the control apparatus (not shown). Based on the signals, the control apparatus performs the velocity control of the armature 17 at the next time of control to alleviate impact when the valve is seated or fully open. The valve opening and closing time judging circuit 30 comprises a trigger signal generating circuit 31 and a comparator 32. An output signal from the vibration sensor 20 is compared with a trigger signal indicative of a specified trigger level (threshold value) generated in the trigger signal generating circuit 31 and when the output signal exceeds the trigger level, a valve opening and closing time indicator signal is output from the comparator 32. The trigger signal generating circuit 31 is for outputting a trigger signal having a threshold value which will be described hereinafter for judging a valve opening or closing time. In this embodiment, the trigger signal generating circuit 31 is constituted by a gradual discharge type peak hold circuit for holding a peak value of the output from the vibration sensor 20 by means of a holding condenser and the like, and a circuit for outputting a trigger signal having a 1/X (X; optional value) times level of the peak value held in the peak hold circuit to the comparator 32. In this case, the 1/X times level of the peak value becomes a threshold value for judging a valve opening and closing time. Further, this trigger signal is updated by resetting the peak value by discharging the holding condenser based on a signal issued from a crank angle sensor 21 every specified number of rotation of the engine. Alternatively, the trigger signal generating circuit 31 may be constituted so as to output as a trigger signal a predetermined voltage, for example, a 1/X times voltage of a blueprint peak value of the output from the vibration sensor 20 or a 1/X times voltage of an experimentally obtained magnitude of vibration generated when the valve is fully open or when the valve is seated. Fig. 3 shows a wave shape of vibration generated when the valve closing solenoid 5 is energised to attract the armature 17 and the valve head 4a of the valve 4 comes into contact with the valve seat 12. The vibration transmitted through the valve seat 12 is detected by the vibration sensor 20 and is inputted to the valve opening and closing time judging circuit 30. The trigger signal generating circuit 31 holds the peak value of the magnitude of the wave shape which is output from the vibration sensor 20 and outputs as a trigger signal a 1/X times signal of the peak value to the comparator 32. The comparator 32 compares the output from the vibration sensor 20 with the trigger signal and outputs the valve opening and closing time indicative signal, when the output level of the vibration sensor 20 exceeds the trigger level, i.e., the threshold value of the trigger signal. Thus, it is possible to detect a time when the valve is fully open or seated on the valve seat correctly and speedily by using the vibration sensor. It is thereby possible to enhance control in the velocity control of the electromagnetically operated valve. By changing the trigger level for judging the opening and closing time according to an actually detected magnitude level of vibration, or by updating the trigger level into a newest value every specified number of rotations of the crank shaft, it is possible to delete (filter) the effect of dispersion or age deterioration of components. Fig. 4 shows a valve opening and closing time judging circuit 40 according to a second embodiment of the present invention. In this embodiment, signals output from the vibration sensor 20 are subjected to an analogue to digital (A/D) conversion and the digitised data are processed in a micro-computer to obtain valve opening or closing times. The valve opening and closing time judging circuit 40 comprises an A/D converter 41 and a micro-computer 42. The micro-computer 42 sends a trigger signal to the A/D converter 41 at a short interval of time to receive sampled-digital data of the output of the vibration sensor 20 and compares these sampled data with a specified threshold value to judge a valve opening or closing time. The threshold value is established to be a value calculated from the output of the vibration sensor 20, in this embodiment, an X times value of the mean value of the background output of the vibration sensor 20 at the time when the valve is away from the positions, valve fully open and valve fully closed. In this case, the threshold level established based on the output of the vibration sensor 20 is updated by a signal from the crank angle sensor 21 every specified number of rotations of the crank shaft. The sampled-data from the vibration sensor 20 are compared with thus established threshold level. In cases where the sampled-data exceed consecutively the threshold level at larger than specified frequency or more than a specified period of time, it is judged that the valve has reached a valve fully open or fully closed position. On the other hand, in a case where those sampled-data exceed the threshold value at smaller than specified frequency or less than a specified time, those data are judged to be noise. As an alternative way of establishing the threshold value, the threshold value may be stored in the micro-computer 42 in a form of fixed data, for example, a 1/X times value of a blueprint output value of the vibration sensor 20. Further, the threshold level may be established to be a 1/X times value of the peak output value of the vibration sensor 20, or an X times value of the mean value of magnitudes detected by the vibration sensor 20. In this embodiment, the sampled-data are employed for the comparison data as they are, however, the comparison data may be a calculated value, for example, an absolute value of the difference between the sample-data and the mean value of magnitudes. The second embodiment is able to delete (filter) noise from the sampled-data more effectively, improving the reliability of the apparatus.

Claims: An apparatus for detecting the timing of an electromagnetically operated valve (1) in an internal combustion engine, comprising: vibration detecting means (20) for detecting a vibration generated when said valve (4) reaches an open position or when said valve (4) reaches a seated position; and for generating a data of said detected vibration, and judging means (30,40) for comparing a comparison data communicated based on said data of said vibration communicated from said vibration detecting means (20) with a threshold value, characterised in that said judging means (30, 40) judges that said valve (4) has reached said open position or said seated position when said comparison data value consecutively exceeds said threshold value. Apparatus according to claim 1 wherein said comparison data exceeds said threshold value for more than a specified time. Apparatus according to claim 1or claim 2 wherein said comparison data is a value at larger than a specified frequency of said data communicated from said vibration detecting means (20). Apparatus according to any one of claims 1-3 wherein said threshold value is a predetermined fixed value according to a blue print peak value of the output from said vibration detecting means (20). The apparatus according to any one of claims 1-3 wherein said threshold value is varied in accordance with the magnitude of said vibration. The apparatus according to any one of claims 1-3 wherein said threshold value is updated every specified number of revolutions of said engine. The apparatus according to claim 5 wherein said magnitude is a peak value of said vibration. The apparatus according to claim 5 wherein said magnitude isa mean value of said magnitudes of said vibrationwhen said valve (4) is away from said open position or said seated position. A method of detecting the timing of an electromagnetically operated valve (1) in an internal combustion engine, comprising the steps of: detecting a vibration generated when said valve (4) reaches an open position or when said valve (4) reaches a seated position to generate data of said detected vibration; generating a comparison data based on said generated vibration data; and comparing said comparison data value with a threshold value; characterised by judging that said valve (4) has reached said open position or said seated position when said comparison data value consecutively exceeds said threshold value. The method according to claim 9 wherein said comparison data exceeds said threshold value for more than a specified time. The method according to claim 9 or claim 10 wherein said comparison data is a value at larger than a specified frequency of said data communicated from said vibration detecting means (20). The metho according to any one of claims 9-11 wherein said threshold value is a predetermined fixed value according to a blue print peak value of the output from said vibration detecting means (20). The method according to any one of claims 9-11wherein said threshold value is varied in accordance with a magnitude of said vibration. The method according to any one of claims 9-11 wherein said threshold value is updated every specified number of revolutions of said engine. The method according to claim 13 wherein said magnitude is a peak value of said vibration. The method according to claim 13 wherein said magnitude is a mean value of magnitudes of said vibration when said valve (4) is away from said open position or said seated position.

Inventors: ISHII MITSUNORI, KAMIMARU SHINJI, ISHII, MITSUNORI, KAMIMARU, SHINJI
Applicants: FUJI HEAVY IND LTD, FUJI JUKOGYO KABUSHIKI KAISHA
Application year: 1998
Main classification: F01L9
IPC codes: F02D13, F01L1, F01L9, F16K37, F01L3