JP4920092B2 - Knock sensor device - Google Patents

Description

  The present invention relates to a knock sensor device that detects a knock (knock) generated in an internal combustion engine, and more particularly to a knock sensor device having a failure determination function.

  2. Description of the Related Art Conventionally, a method of detecting a knock phenomenon that occurs in an engine with a vibration sensor (hereinafter referred to as a knock sensor) directly attached to the engine block is known. It is known that when a knock occurs during engine operation, vibration in a specific frequency band is generated according to the vibration mode of the engine or the knock, and the knock is measured by measuring the vibration intensity of this natural frequency. The detection is performed.

  By the way, if any abnormality occurs in the knock sensor for detecting the knock, the knock cannot be detected normally. Therefore, it is necessary to detect abnormality (failure detection) of the knock sensor. As a method, a bias voltage is applied to the knock sensor, and the bias voltage is monitored to determine whether there is an abnormality such as disconnection in the knock sensor path (for example, Patent Document 1). A method (for example, Patent Documents 1, 2, and 3) for determining whether there is an abnormality in the output characteristics of the knock sensor by detecting the vibration level has been proposed.

JP-A-4-331329 Japanese Patent No. 3322219 Japanese Patent No. 2562960

  In Patent Document 1, with respect to the method of applying a bias voltage, on / off diagnosis such as a knock sensor disconnection or short-circuit can be performed, but a decrease in output level due to deterioration of the piezoelectric element can be accurately diagnosed. It has been pointed out that there is no. Therefore, Patent Document 1 discloses a method for determining a failure when the vibration level corresponding to the engine rotation speed is equal to or lower than a predetermined value so that a decrease in output level due to deterioration of the piezoelectric element can also be detected.

  However, in Patent Document 2, in the determination based on the vibration level as described above, the vibration level in the low rotation region is smaller than the noise level superimposed when the knock sensor path is disconnected, so that a certain high rotation region (for example, 3000 [r / Min] or more), it is disclosed that a failure cannot be correctly determined. Therefore, in Patent Document 2, it is noted that the vibration level of the engine has a large difference between the strokes, and the comparison is made by detecting the failure based on the difference between the maximum value and the minimum value of the vibration level between the predetermined strokes. A method has been proposed in which a knock sensor failure can be determined even in a low rotational range (for example, about 2000 [r / min]).

  More specifically, the difference between the maximum / minimum vibration level between the engine's predetermined strokes during normal operation depends on the electrical noise level superimposed when the knock sensor path is disconnected or the vibration level of the engine when sensor characteristics deteriorate. It can be said that a knock sensor failure can be correctly determined if the rotation range is larger than the difference between the maximum value and the minimum value between the predetermined strokes. However, since the engine vibration level is very small at extremely low revolutions (for example, 1000 [r / min] or less) such as when idling, the difference between the maximum and minimum values of the vibration level between predetermined strokes is also small. Even if the method according to Patent Document 2 is used, it is difficult to determine whether the knock sensor is normal or abnormal, and if the vehicle does not travel while maintaining a certain rotational speed (for example, 2000 [r / min] or more), There was a problem that failure could not be judged.

  Further, in Patent Document 3, a knock gate is provided in a period in which the vibration level is large when knocking occurs during one stroke, a sensor fail noise gate is provided in a period in which the vibration level is large when knocking is not occurring, It describes that a noise gate is set during a period in which normal vibration occurs regardless of the presence or absence of knock, knock detection is performed by the knock gate and the noise gate, and failure of the knock sensor is determined by the noise gate for sensor failure. . However, even in this method, based on the contents shown in Patent Document 2, the vibration level at the low-speed sensor fail noise gate is smaller than the noise level superimposed when the knock sensor path is disconnected. It has been difficult to detect a knock sensor failure at extremely low rotation times.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a knock sensor device that can detect a failure even at an extremely low rotation such as when idling.

  A knock sensor device according to the present invention is a knock sensor for detecting vibration caused by knock of an internal combustion engine, and A / D-converts the output signal of the knock sensor every predetermined time in a crank angle period in which vibration caused by knock occurs. First A / D conversion means, second A / D conversion means for A / D converting the output signal of the knock sensor every predetermined time in a crank angle period in which mechanical noise is constantly generated, and the first The deviation between the amplitude level of the data A / D converted by the second A / D conversion means and the amplitude level of the data A / D converted by the first A / D conversion means is calculated, and a plurality of processes are continued. And a knock sensor failure determining means for determining that the knock sensor has failed when the deviation falls below a failure determination level.

  A knock sensor device according to the present invention includes a knock sensor for detecting vibration caused by knocking of an internal combustion engine, and an output signal of the knock sensor at a predetermined time in a crank angle period in which vibration caused by knock occurs. A first A / D conversion means for converting; a second A / D conversion means for A / D converting the output signal of the knock sensor every predetermined time in a crank angle period in which mechanical noise is constantly generated; The first amplitude level which is the amplitude level of the data A / D converted by the first A / D conversion means and the first amplitude level which is the amplitude level of the data A / D converted by the second A / D conversion means. Two amplitude levels are stored for each stroke over a plurality of strokes, and the maximum of the plurality of strokes of the second amplitude level and the minimum of the plurality of strokes of the first amplitude level are stored. Calculating a deviation between, in which the deviation is continuously multiple times with a knock sensor failure determining means determines that the failure of the knock sensor if it falls below the fault determination level.

  According to the knock sensor device of the present invention, since the failure determination is performed based on the deviation between the vibration level during the period when the vibration due to the noise occurs and the vibration level during the period when the vibration due to the knock occurs, Since the deviation is small and the deviation becomes large even at extremely low revolutions such as when idling during normal operation, it is possible to detect a failure of the knock sensor even at extremely low revolutions.

According to the knock sensor device of the present invention, a plurality of first amplitude levels that are amplitude levels during a period in which vibration due to knock occurs and second amplitude levels that are vibration levels in a period in which vibration due to noise occurs are provided for each stroke. Each of the strokes is stored, and a deviation between the maximum of the plurality of strokes of the second amplitude level and the minimum of the plurality of strokes of the first amplitude level is calculated, and is continued a plurality of times. Since the knock sensor failure determination means for determining that the knock sensor has failed when the deviation falls below the failure determination level is provided, the deviation becomes even greater even at extremely low speeds such as idling when the knock sensor is normal. For this reason, it is possible to improve the failure detection accuracy of the knock sensor even at extremely low rotations.

It is a block diagram which shows roughly the engine provided with the knock sensor apparatus of this invention, and an engine control part. It is a block diagram which shows roughly the engine provided with the knock sensor apparatus of this invention, and an engine control part. It is a block diagram which shows the structure of the whole knock control in the knock sensor apparatus of Embodiment 1 of this invention. It is a figure which shows roughly the vibration level at the time of normal and a failure of a knock sensor apparatus. 3 is a flowchart showing a failure detection process in the knock sensor device of the first embodiment. It is a figure which shows roughly the difference of Max_ns and Max_knk at the time of normality and a failure of a knock sensor apparatus.

It is a figure which shows roughly the case where dispersion | variation arises in the vibration level at the time of normality and a failure of a knock sensor apparatus. 6 is a flowchart showing a part of a failure detection process in the knock sensor device of the second embodiment. 6 is a flowchart showing a part of a failure detection process in the knock sensor device of the second embodiment. FIG. 10 is a diagram schematically showing the generation timing of noise caused by the drive of an injector relating to the third embodiment. FIG. 10 is a diagram schematically showing the generation timing of noise caused by driving of an intake valve according to the fourth embodiment. 10 is a flowchart showing a part of failure detection processing in the knock sensor device of the fifth embodiment. 20 is a flowchart showing a part of failure detection processing in the knock sensor device of the seventh embodiment.

Embodiment 1 FIG.
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a configuration diagram schematically showing an engine and an engine control unit including a knock sensor device of the present invention. FIG. 2 is a block diagram schematically showing an engine provided with the knock sensor device of the present invention and an engine control unit.

  In FIG. 1, an electronically controlled throttle valve 2 that is electronically controlled to adjust the intake air flow rate is provided upstream of the intake system of the engine 1. In order to measure the opening degree of the electronically controlled throttle valve 2, a throttle opening degree sensor 3 is provided. Instead of the electronically controlled throttle valve 2, a mechanical throttle valve connected directly to an accelerator pedal (not shown) with a wire may be used. Further, an air flow sensor 4 for measuring the intake air flow rate is provided upstream of the electronically controlled throttle valve 2, and the pressure in the surge tank 5 is measured on the engine 1 side downstream of the electronically controlled throttle valve 2. An intake manifold pressure sensor 6 is provided. Note that both the airflow sensor 4 and the intake manifold pressure sensor 6 may be provided, or only one of them may be provided.

  A variable dynamic intake valve mechanism 7 capable of variably controlling the opening / closing timing of the intake valve is attached to the intake valve provided in the intake port downstream of the surge tank 5, and an injector 8 for injecting fuel is provided in the intake port. Is provided. In addition, a variable dynamic exhaust valve mechanism 31 capable of variably controlling the opening / closing timing of the exhaust valve is attached to the exhaust valve provided in the exhaust port. The injector 8 may be provided so that it can be directly injected into the cylinder of the engine 1. Further, an ignition coil 9 and a spark plug 10 for igniting the air-fuel mixture in the cylinder of the engine 1, and a crank for detecting the edge of a plate provided on the crankshaft for detecting the rotational speed and crank angle of the engine. The engine 1 is provided with an angle sensor 11 and a knock sensor 12 for detecting engine vibration.

  In FIG. 2, the intake air flow rate measured by the airflow sensor 4, the intake manifold pressure measured by the intake manifold pressure sensor 6, the opening degree of the electronically controlled throttle valve 2 measured by the throttle opening degree sensor 3, the crank The pulse synchronized with the edge of the plate provided on the crankshaft provided from the angle sensor 11 and the vibration waveform of the engine 1 measured by the knock sensor 12 are sent to an electronic control unit (hereinafter referred to as “ECU”) 13. Entered. Measurement values are also input to the ECU 13 from various sensors other than those described above, and signals from other controllers (for example, control systems such as automatic transmission control, brake control, and traction control) are also input.

  The ECU 13 controls the electronically controlled throttle valve 2 by calculating the target throttle opening based on the accelerator opening and the engine operating state. Further, the variable dynamic intake valve mechanism 7 that variably controls the opening / closing timing of the intake valve is controlled according to the operation state at that time, and the injector 8 is driven so as to achieve the target air-fuel ratio so as to achieve the target ignition timing. The ignition coil 9 is energized. In addition, when knock is detected by an apparatus described later, control for suppressing the occurrence of knock is also performed by setting the target ignition timing to the retard side (retard side). Further, command values for various actuators other than those described above are also calculated.

  Next, an overview of knock control performed in the ECU 13 will be described with reference to FIG. FIG. 3 is a block diagram showing the overall configuration of knock control in the knock sensor device according to the first embodiment of the present invention. In FIG. 3, 12 and 13 are the knock sensor and ECU shown in FIGS. The configuration of the knock control unit in the ECU 13 will be described. The ECU 13 includes various I / F circuits and a microcomputer. The microcomputer is an A / D converter that converts an analog signal into a digital signal, a ROM area that stores a control program and control constants, and a variable when the program is executed. It is comprised from the RAM area etc. which memorize | stores.

  Reference numeral 14 denotes an I / F circuit for knock control, which is a low-pass filter (LPF) for removing high frequency components of the signal output of the knock sensor. Reference numeral 15 denotes an A / D conversion means of the microcomputer, and the A / D conversion performed thereby is executed at regular time intervals (for example, set 10 μs or 20 μs). In the LPF 14, in order to capture all vibration components by the A / D conversion means 15, for example, a bias is set to 2.5V (the center of the vibration component is set to 2.5V), and 0 to Also included is a gain conversion function that amplifies around 2.5V when the vibration component is small and reduces it around 2.5V when the vibration component is small, so that the vibration component falls within the range of 5V.

This A / D conversion is always performed, and a knock generation period (for example, TDC to ATDC 50 ° CA (abbreviated as A50), hereinafter referred to as a knock detection period) TDC: Top Death Center, ATDC: After Only the data of Top Death Center) may be sent to 16 or later, or A / D conversion may be performed only during the knock detection period and sent to 16 or later (in the figure, the period sent after 16 is A / D). D window). The knock detection period will be described with reference to FIG. FIG. 4 (1) In the knock detection period when there is no knock, the vibration component appearing in the knock sensor signal is small, and abnormal vibration due to knock does not occur. However, when there is a knock in FIG. 4 (2), the vibration component appearing in the knock sensor signal is large, and abnormal vibration due to the knock occurs. As described above, the period in which the magnitude of the vibration component changes according to the presence or absence of knocking is set as the knock detection period.

  In subsequent 16a and 16b, time-frequency analysis by digital signal processing is performed. As this digital signal processing, for example, spectral sequences of different knock natural frequency components are calculated by a process called discrete Fourier transform (DFT) or short-time Fourier transform (STFT). As digital signal processing, the knock natural frequency component may be extracted using an IIR (infinite impulse response) filter or FIR (finite impulse response) filter.

In 17a and 17b, the peak hold value of the spectrum sequence calculated in 16a and 16b is calculated. Reference numerals 18a and 18b denote averaging units, which perform averaging on the peak hold value calculated for each stroke by using the following equation.
VBGLa, b (n) = K1 * VBGLa, b (n-1) + (1-K1) * VPa, b (n) (1)
(VBGL (n): filter value, VP (n): peak hold value, K1: averaging factor, n: number of strokes)
In subsequent 19a and 19b, a threshold value for knock determination is obtained by the following equation.
VTHa, b (n) = VBGLa, b (n) × Ktha, b + Vofs a, b (2)
(VTH (n): threshold value, Kth: threshold coefficient, Vofs: threshold offset)

Reference numerals 20a and 20b denote comparison operation units which compare the peak hold value and the threshold value, determine the presence / absence of knock by the following equation, and output a signal corresponding to the knock intensity.
VKa, b (n) = max {VPa, b (n) −VTHa, b (n), 0} (3)
(VK (n): Knock strength (determined that knock is present when VK (n)> 0))
Reference numerals 21a and 21b denote retard amount calculation units for each ignition, which calculate a retard amount corresponding to the knock intensity for each ignition from the knock determination results of the comparison calculation units 20a and 20b according to the following equation.
ΔθRa, b (n) = VKa, b (n) / VTHa, b (n) × Kga, b (4)
(ΔθR (n): retard amount per ignition, Kg: retard amount reflection coefficient)

Reference numeral 22 denotes a knock retard amount calculation unit which integrates the larger retard amount for each ignition of 21a and 21b, and calculates the knock correction amount of the ignition timing. To do. This is calculated by the following equation.
θR (n) = θR (n-1) + max {ΔθRa (n), ΔθRb (n)} − Ka (5)
(ΘR (n): knock correction amount, Ka: advance return constant)
The final ignition timing is calculated by the following equation using the knock correction amount θR calculated in this way.
θIG = θB−θR (n) (6)
(ΘIG: final ignition timing, θB: basic ignition timing)
In the above, the processing method which implement | achieves the knock control which suppresses knock by retarding the knock detection and ignition timing using the frequency analysis result by digital signal processing by 16-22 was demonstrated.

  Next, a failure determination processing method for the knock sensor device shown in FIGS. 23 to 25 will be described. In the process of calculating the maximum amplitude of the knock detection period 23, the difference between the maximum value and the minimum value of the A / D conversion value in the knock detection period is set as the maximum amplitude of the knock detection period. In the maximum amplitude calculation process of 24 noise detection periods, the difference between the maximum value and the minimum value of the A / D conversion value in the noise detection period is set as the maximum amplitude of the noise detection period. Here, the acquisition method of the A / D conversion value during the noise detection period is, as described above, A / D conversion means for performing A / D conversion at regular time intervals (for example, set 10 μs, 20 μs, etc.). 15, the A / D conversion is always performed, and only data in a period in which mechanical noise is generated (for example, ATDC 80 ° CA to ATDC 120 ° CA, etc., hereinafter referred to as a noise detection period) is sent to 24. Alternatively, A / D conversion may be performed only during the noise detection period and sent to 24.

  A method for setting the noise detection period will be described with reference to FIG. Even when there is no knocking in FIG. 4 (1) or when there is knocking in FIG. 4 (2), vibration due to noise that is constantly generated with a large vibration component is generated during the noise detection period. As described above, the period during which noise vibration constantly occurs without changing the magnitude of the vibration component according to the presence or absence of knocking is set as the noise detection period.

  Next, a failure determination method for the knock sensor device shown in 25 will be described. When the knock sensor device is operating normally, as described above, the noise detection period has a large vibration component and is constantly generated even when there is no knock in FIG. 4 (1) and when there is a knock in FIG. 4 (2). On the other hand, in the knock detection period, a large vibration is generated only when the knock occurs, but the vibration component is very small when there is no knock. Further, as described above, when the knock occurs, the ignition timing is corrected to retard the delay, so that the knock does not continue to occur steadily, and it can be considered that there is almost no knock in the normal operation state. Therefore, when the difference between the maximum amplitude Max_ns of the noise detection period and the maximum amplitude Max_knk of the knock detection period is taken, a value that is large to some extent is obtained except when a knock occurs as shown in FIG.

  Next, when a failure such as a disconnection, a power fault, or a ground fault occurs in the knock sensor device, as shown in FIG. 4 (3) when the knock sensor fails, a certain amount of vibration is applied regardless of the knock detection period or the noise detection period. Waveforms are superimposed. This is not the vibration detected by the knock sensor but the electric noise superimposed on the wiring to the knock sensor, or the noise accompanying fluctuations in GND or battery voltage. Such noise has a certain amplitude and is usually larger than the amplitude when the vibration level is low such as when idling, but there is little difference between the knock detection period and the noise detection period. Therefore, when the difference between the maximum amplitude Max_ns of the noise detection period and the maximum amplitude Max_knk of the knock detection period is taken as in the normal state, the difference is always relatively small as shown in FIG. Therefore, it is possible to determine whether the knock sensor device is normal or failure by appropriately setting the failure determination value. Even when the output characteristics of the knock sensor are significantly reduced due to deterioration of the piezoelectric element, the difference between the maximum amplitude Max_ns of the noise detection period and the maximum amplitude Max_knk of the knock detection period is reduced, so that an abnormality in the sensor characteristics can also be prevented. Detection is possible.

  The details of the failure detection process of the knock sensor device in 23 to 25 of FIG. 3 are shown in FIG. Hereinafter, the failure detection process of the knock sensor device will be described in detail with reference to FIG. Note that the failure detection processing of the knock sensor device shown in FIG. 5 ends the A / D conversion of the current knock detection period and the noise detection period, and the knock detection period or the A / D of the noise detection period in the next step. It is performed at the timing until the conversion starts. More specifically, an interrupt processing timing that occurs in synchronization with engine rotation such as BTDC 5 ° CA (however, a timing that does not overlap the knock detection period or the noise detection period), or the knock detection period and the noise detection period This is performed at the timing of interrupt processing that occurs at the end of A / D conversion on the slow side of the. First, in step S101, the maximum amplitude Max_knk of the knock detection period is calculated. As described above, this can be calculated from the difference between the maximum value and the minimum value in the knock detection period. Subsequently, in step S102, the maximum amplitude Max_ns of the noise detection period is calculated. As described above, this can also be calculated by the difference between the maximum value and the minimum value in the noise detection period, similarly to the maximum amplitude Max_knk in the knock detection period. In a succeeding step S103, it is determined whether or not the difference between the maximum amplitude Max_ns of the noise detection period and the maximum amplitude Max_knk of the knock detection period is smaller than a determination value.

  If the difference between the maximum amplitude Max_ns of the noise detection period and the maximum amplitude Max_knk of the knock detection period is smaller than the determination value, it is determined that the knock sensor device has failed, and the normal counter is reset to the initial value (for example, 50 strokes) in step S104. In step S105, the failure counter is counted down. If the difference between the maximum amplitude Max_ns of the noise detection period and the maximum amplitude Max_knk of the knock detection period is equal to or larger than the determination value, the knock sensor device is determined to be normal, and the failure counter is set to an initial value (for example, 100 strokes) in step S106. In step S107, the normal counter is counted down.

  In subsequent step S108, it is determined whether or not the failure counter = 0. If the failure counter = 0, it is determined that the failure determination has continued for a predetermined number of strokes (a plurality of strokes), and the failure determination is performed in step S110. Set the flag. If the failure counter is not 0, it is determined in step S109 whether or not the normal counter is 0. If the normal counter is 0, the normal determination is continued for a predetermined number of strokes (multiple strokes). In step S111, the failure determination flag is cleared. If it is determined in step S109 that the normal counter is not 0, nothing is performed (the state of the failure determination flag is maintained), and the process is terminated.

  In FIG. 5, the difference between the maximum amplitude Max_ns of the noise detection period and the maximum amplitude Max_knk of the knock detection period is compared, but the amplitude level of the noise detection period (in addition to the maximum amplitude, for example, an average value of amplitude, an integrated value of amplitude) A failure may be similarly determined by comparing the difference between the amplitude level of the knock detection period (in addition to the maximum amplitude, for example, an average value of amplitude and an integral value of amplitude). As described above, the knock sensor device failure determination makes it possible to detect the knock sensor device failure by monitoring the vibration amplitude level of the knock sensor even in an extremely low rotation range such as when idling, which has been difficult in the past. Judgment can be performed with high accuracy. Therefore, the failure determination of the knock sensor device can be carried out satisfactorily in the entire engine speed range. In addition, the knock sensor failure determination means determines that the knock sensor is normal when the deviation exceeds the failure determination level continuously for a plurality of strokes. Can be determined.

Embodiment 2. FIG.
Next, a second embodiment will be described. Since the second embodiment has the same parts as the first embodiment, the different parts will be described in detail. In the first embodiment, it has been described that the knock sensor is determined to be normal because there is a large difference in vibration components between the knock detection period and the noise detection period in FIG. More specifically, in steps S101 to S103 in FIG. 5, the knock sensor failure determination is performed by comparing the difference between the maximum amplitudes of the knock detection period and the noise detection period between the same strokes with a determination value.

  However, depending on the individual difference of the engine and the engine speed, as shown in FIG. 7 (1) when there is no knock, when the difference between the vibration components in the knock detection period and the noise detection period is large (A in FIG. 7 (1)) A small case (B in FIG. 7A) occurs. In this way, if there is a variation in the difference between the vibration components, the knock sensor failure determination accuracy may be lowered. Therefore, in the second embodiment, the knock detection period between two or more predetermined strokes (a plurality of strokes) is increased. The difference is that the difference between the minimum amplitude and the maximum amplitude of the noise detection period is calculated, and the knock sensor failure is determined according to this difference. Even in such a case, the difference between the noise detection period and the knock detection period is small as shown in FIG.

To realize the second embodiment, steps S101 and S102 of FIG. 5 described in the first embodiment are changed as shown in FIGS. In steps S401 to S403 in FIG. 8 corresponding to step S101 in FIG. 5, Max_knk having the smallest maximum amplitude of the knock detection period between two or more predetermined stroke numbers is calculated. First, in step S401, the maximum stored amplitude value in the knock detection period up to the previous stroke is shifted. In the subsequent step S402, the maximum amplitude of the knock detection period as in the current state is calculated, and this calculation method is calculated by the difference between the maximum value and the minimum value in the knock detection period as in step S101 of FIG. In the following step S403, Max_knk having the smallest maximum amplitude of the knock detection period between the predetermined number of strokes is calculated by the following equation.
Max_knk = min {Max_knk (n), Max_knk (n-1), ..., Max_knk (n- (k-1))}
(Max_knk (n): Maximum amplitude of knock detection period of stroke n, n: current number, k: predetermined number of strokes of 2 or more)

If all Max_knk (n) are set to zero as initial values at the time of starting the engine, only the first stroke after starting is the same as in the first embodiment, but the effects of the second embodiment after the second stroke. Is obtained. Next, in steps S501 to S503 in FIG. 9 corresponding to step S102 in FIG. 5, Max_ns having the maximum maximum amplitude of the noise detection period between two or more predetermined stroke numbers is calculated. First, in step S501, the maximum amplitude stored value in the noise detection period up to the previous process is shifted. In the subsequent step S502, the maximum amplitude of the noise detection period as of the present time is calculated. This calculation method is calculated based on the difference between the maximum value and the minimum value in the noise detection period as in step S102 of FIG. In the subsequent step S503, Max_ns of the maximum amplitude of the noise detection period between the predetermined number of strokes is calculated by the following equation.
Max_ns = max {Max_ns (n), Max_ns (n-1), ..., Max_ns (n- (k-1))}
(Max_ns (n): Maximum amplitude of noise detection period of stroke n, n: current number, k: number of predetermined strokes of 2 or more)

Note that if all Max_ns (n) are set to zero as initial values when the engine is started, only the first stroke after starting is the same as in the first embodiment, but the effects of the second embodiment after the second stroke. Is obtained. After these processes, the processes after step S103 in FIG. 5 are performed. Specifically, in step S103 of FIG. 5, the difference between the maximum Max_ns of the maximum amplitude of the noise detection period and the minimum Max_knk of the maximum amplitude of the knock detection period between the calculated two or more predetermined stroke numbers is calculated. It is determined whether it is smaller than the determination value, and the process proceeds to step S104 or S106 in FIG. 5 depending on the determination result. The subsequent steps are the same as in the first embodiment.

In step S103 of FIG. 5, the difference between the maximum Max_ns of the maximum amplitude of the noise detection period and the minimum Max_knk of the maximum amplitude of the knock detection period between the calculated two or more predetermined stroke numbers is compared. Between the maximum amplitude level of the noise detection period (for example, the average value of amplitude, the integrated value of amplitude) and the amplitude level of knock detection period (other than the maximum amplitude) between two or more predetermined stroke numbers. In addition, for example, a failure may be similarly determined by comparing a difference with the smallest one (for example, an average value of amplitude and an integral value of amplitude).
As described above, the knock sensor vibration is determined in the extremely low rotation range such as when idling even when the difference in the vibration component between the noise detection period and the knock detection period varies due to the failure determination of the knock sensor. The level monitor makes it possible to determine the knock sensor failure.

Embodiment 3 FIG.
Next, Embodiment 3 will be described. The third embodiment is characterized in that, as compared with the first and second embodiments, the machine noise is specialized in noise caused by driving of the direct injection type in-cylinder injector. Since it is the same as 2, the differences will be described in detail. First, the injector 8 shown in FIG. 1 is provided so that it can be directly injected into the cylinder of the engine 1. In addition, the noise detection period has been described as being a fixed value such as ATDC 80 ° CA to ATDC 120 ° CA in FIG. 4, for example, but the third embodiment specializes in noise caused by injector driving. Therefore, the noise detection period is changed as shown in FIGS. 10 (1) and 10 (2) in synchronization with the drive start timing of the injector.

In FIG. 10, a four-cylinder engine will be described as an example. When the injector drive start timing is set to BTDC 260 ° CA (BTDC: Before Top Death Center) in FIG. 10 (1) by the variable control means for variably controlling the injector drive timing, the mechanical noise due to the injector drive is ATDC 100 °. Since it occurs in the vicinity of CA, for example, the second A / A from ATDC 80 ° CA to ATDC 120 ° CA is selected according to the injector drive timing controlled by the variable control means so as to sufficiently include the noise detection period. Means for setting a crank angle period during which the D conversion means performs A / D conversion is provided.

  Further, in FIG. 10B, when the injector drive start timing is set to BTDC 220 ° CA, mechanical noise due to the drive of the injector is generated in the vicinity of ATDC 140 ° CA. Therefore, this is sufficiently included as a noise detection period. Thus, for example, there is provided means for setting a crank angle period during which the second A / D conversion means performs A / D conversion from ATDC 120 ° CA to ATDC 160 ° CA according to the injector drive timing controlled by the variable control means. It is a thing. Thus, the third embodiment is characterized in that the noise detection period is changed according to the drive timing of the injector.

  As described above, the machine noise is detected more accurately by specializing in the noise caused by the drive of the injector as the machine noise, and further setting the noise detection period according to the drive timing of the injector. By performing knock sensor failure determination, knock sensor failure determination can be performed by monitoring the knock sensor vibration level even in an extremely low rotation range such as during idling.

Embodiment 4 FIG.
Next, a fourth embodiment will be described. The fourth embodiment is different from the first and second embodiments in that it is specialized in noise caused by opening / closing drive of the intake valve or the exhaust valve as mechanical noise. Since it is the same as 2, the differences will be described in detail. As for the noise detection period, it has been described in FIG. 4 that the fixed value is, for example, ATDC 80 ° CA to ATDC 120 ° CA. However, in the fourth embodiment, the noise detection period is characterized by noise caused by opening / closing drive of the intake valve or exhaust valve. Therefore, the noise detection period is changed as shown in FIGS. 11 (1) and 11 (2) in synchronization with the opening / closing timing of the intake valve or the exhaust valve.

  In FIG. 11, a description will be given by taking as an example noise caused by closing the intake valve of a four-cylinder engine. Specifically, when the intake valve closing timing is set to ABDC 70 ° CA (ABDC: After Bottom Death Center) in FIG. 11 (1) by the variable dynamic intake valve mechanism 7 that variably controls the closing timing of the intake valve. Since the mechanical noise due to the intake valve closing drive is generated in the vicinity of ATDC 70 ° CA, the noise detection period is determined in accordance with the closing timing of the intake valve controlled by the variable dynamic intake valve mechanism 7 so as to sufficiently include the noise detection period. For example, a means for setting a crank angle period during which the second A / D conversion means performs A / D conversion from ATDC 70 ° CA to ATDC 120 ° CA is provided. In the third embodiment described above, the generation timing of the mechanical noise is set to approximately the center of the noise detection period. This is because noise caused by the drive of the injector is observed by the knock sensor almost at the drive timing. This is because noise due to opening / closing drive of the intake valve and exhaust valve is often observed with a delay of about 20 to 30 ° CA due to the influence of the cam clearance and the like.

  Further, in FIG. 11 (2), when the intake valve closing timing is set to ABDC 50 ° CA by the variable dynamic intake valve mechanism 7 that variably controls the closing timing of the intake valve, the mechanical noise due to the closing drive of the intake valve becomes ATDC 50. Since it occurs in the vicinity of ° CA, the noise detection period is sufficiently included, for example, from ATDC50 ° CA to ATDC100 ° CA according to the closing timing of the intake valve controlled by the variable intake valve mechanism 7. Further, means for setting a crank angle period during which the second A / D conversion means performs A / D conversion is provided. When the knock detection period and the noise detection period are continuous or overlapped as shown in FIG. 11 (2), the A / D conversion in the knock detection period and the A / D conversion in the noise detection period are performed in common. It is easier to distribute the knock detection period and the noise detection period after the / D conversion.

    In the above, the closing timing of the intake valve has been described as an example, but the same processing can be performed in the case of a variable dynamic intake valve mechanism that variably controls the opening timing of the intake valve. Further, with respect to the variable dynamic exhaust valve mechanism that variably controls the opening / closing timing of the exhaust valve, the second A / D conversion means performs A / D conversion according to the opening / closing timing of the exhaust valve controlled by the variable dynamic exhaust valve mechanism. The same processing can be performed by providing means for setting the crank angle period. As described above, the fourth embodiment is characterized in that the noise detection period is set according to the opening / closing timing of the intake valve or the exhaust valve.

  As described above, the machine noise is specialized as noise caused by the opening / closing drive of the intake valve or exhaust valve, and the noise detection period is set according to the opening / closing timing of the intake valve or exhaust valve. By detecting noise and performing knock sensor failure determination based on this noise, knock sensor failure determination can be performed by monitoring the knock sensor vibration level even in an extremely low rotation range such as when idling. .

Embodiment 5 FIG.
Next, a fifth embodiment of the present invention will be described. The fifth embodiment is characterized in that the third and fourth embodiments are switched according to the operating state of the engine. Specifically, the noise caused by the drive of the injector is constant regardless of the engine speed, but the noise caused by the opening / closing drive of the intake valve or the exhaust valve tends to increase as the engine speed increases. is there. Therefore, when the engine rotation speed at which the noise due to the drive of the intake valve or the exhaust valve becomes larger than the noise due to the drive of the injector is stored in advance as a set value, and the engine rotation speed is lower than the set value, The noise caused by the drive of the injector is switched over by selecting and switching the noise caused by the opening / closing drive of the intake valve or exhaust valve when the engine speed is higher than the set value. Thus, the knock sensor failure can be determined satisfactorily.

  Details of the fifth embodiment will be described with reference to FIG. First, in step S201, the current engine speed ne is calculated. This can be calculated based on the edge interval for each predetermined crank angle detected by the crank angle sensor 11 of FIG. In a succeeding step S202, it is determined whether or not the engine speed ne is smaller than a set value. As the set value, an engine rotation speed (for example, 2000 [r / min]) at which noise caused by opening / closing drive of the intake valve or exhaust valve becomes larger than noise caused by driving of the injector as described above is set. Keep it.

  If it is determined that the engine speed ne is smaller than the set value, the process proceeds to step S203, and the second A / D conversion means performs A / D conversion according to the injector drive timing as in the third embodiment. When the crank angle period (noise detection period) is set and it is determined that the engine speed ne is equal to or greater than the predetermined value, the process proceeds to step S204, and the second timing is set according to the opening / closing timing of the intake valve, as in the fourth embodiment. Means is provided for setting a crank angle period (noise detection period) during which the A / D conversion means performs A / D conversion. Thereby, when the engine speed is lower than the set value, the noise caused by the drive of the injector is selected and when the engine speed is higher than the set value, the noise caused by the opening / closing drive of the intake valve is selected and switched. It becomes possible.

  In addition, although the case where it originates in the opening / closing drive of an intake valve was demonstrated here, the case where it originates in the opening / closing drive of an exhaust valve similarly sets a noise detection period according to the opening / closing timing of an exhaust valve in step S204. Can be realized. After the above process, the knock sensor failure detection process shown in FIG. 5 described in the first and second embodiments is performed so that the knock sensor failure can be satisfactorily determined in the entire engine speed range. Become. Further, even when the influence level of noise causes changes according to the engine speed, it is possible to accurately detect a knock sensor failure.

Embodiment 6 FIG.
Next, a sixth embodiment will be described. The sixth embodiment is characterized in that the first embodiment is applied to an operation region where the engine speed is low. That is, in the region where the engine rotational speed is high, the knock sensor failure determination is possible with the conventional technology. Therefore, the first embodiment is applied to the operation region where the engine rotational speed is low, For example, the failure determination of the knock sensor is performed by a method of determining a failure when the vibration level according to the engine rotation speed described in Patent Document 1 is a predetermined value or less.

Specifically, when the rotational speed at which the vibration level in the normal state is greater than the vibration level due to noise superimposed when the knock sensor path is disconnected is stored in advance as a set value, and the engine rotational speed is lower than the set value Therefore, in the first embodiment, when the engine speed is higher than the set value, the conventional technique is selected and switched so that the knock sensor failure can be satisfactorily determined in the entire engine speed range. become. Note that although the method of Patent Document 1 is given as an example of the prior art, other methods may be used. By doing so, it becomes possible to perform failure determination in the low rotation range, which was not possible with the conventional technology, while performing failure determination with a technology that has been proven in the past in the high rotation range, and engine rotation The knock sensor failure can be satisfactorily determined in the entire speed range. Further, even when the influence level of noise causes changes according to the engine speed, it is possible to accurately detect a knock sensor failure.

Embodiment 7 FIG.
Next, a seventh embodiment will be described. The seventh embodiment is characterized in that the second and third embodiments are applied to an operation region where the engine speed is low. In other words, in the region where the engine speed is high, the knock sensor failure can be determined by the conventional technology. Therefore, the second and third embodiments are applied to the operating region where the engine speed is low, and the engine speed is high. In the area, knock sensor failure determination is performed by the prior art. Specifically, the noise caused by the drive of the injector is constant regardless of the engine speed, and when the engine speed is low, it is greater than the noise level during the knock detection period when there is no knock, but the engine speed As the speed increases, the noise level due to vibration of the engine itself tends to increase.

Therefore, the engine speed at which the noise due to the vibration of the engine itself is larger than the noise caused by the drive of the injector is stored in advance as a set value, and when the engine speed is lower than the set value, two or more Failure detection is performed based on the difference between the maximum noise caused by the drive of the injector measured during the noise detection period between the predetermined number of strokes and the minimum noise measured during the knock detection period, and the engine speed is set to the set value. If it is higher, the knock detection period is set as the noise detection period, and failure detection is performed by the difference between the maximum and minimum noises measured during the knock detection period between two or more predetermined strokes. Therefore, the knock sensor failure can be determined satisfactorily in the entire engine speed range. If the knock detection period is the noise detection period when the engine speed is higher than the set value, the method is the same as the method disclosed in Patent Document 2. However, when the engine speed is higher than the set value, the conventional technique is used for knocking. Since the failure determination of the sensor can be performed, the method of Patent Document 2 is given as an example, but other methods may be used.

  The details of the seventh embodiment will be described with reference to FIG. First, in step S301, the current engine speed ne is calculated. This can be calculated based on the edge interval for each predetermined crank angle detected by the crank angle sensor 11 of FIG. In a succeeding step S302, it is determined whether or not the engine speed ne is smaller than a set value. As the set value, an engine rotation speed (for example, 2000 [r / min]) at which the vibration level of noise caused by the vibration of the engine itself is larger than the vibration level of noise caused by driving the injector as described above. Keep it. If it is determined that the engine speed ne is smaller than the set value, the process proceeds to step S303, and the crank angle period (noise detection period) corresponding to the injector drive timing is set as in the third embodiment. If it is determined that the rotational speed ne is equal to or higher than the set value, the process proceeds to step S304, where the knock detection period is set as the noise detection period. Thereafter, the knock sensor failure detection process shown in FIG. 5 described in the second embodiment is performed. As described above, when the engine speed is lower than the set value, the knock sensor failure determination is performed based on the noise caused by the drive of the injector, and when the engine speed is higher than the set value, the knock sensor due to the vibration noise of the engine itself. The failure determination of the knock sensor can be satisfactorily performed in the entire region of the engine rotation speed by performing the failure determination (for example, the method of Patent Document 2; other conventional technology may be used).

DESCRIPTION OF SYMBOLS 1 Engine 2 Throttle valve 3 Throttle opening sensor 4 Airflow sensor 5 Surge tank 6 In manifold pressure sensor 7 Variable intake valve mechanism 8 Injector 9 Ignition coil 10 Spark plug 11 Crank angle sensor 12 Knock sensor 13 ECU

Claims (9)

A knock sensor for detecting vibration caused by knock of the internal combustion engine;
First A / D conversion means for A / D converting the output signal of the knock sensor every predetermined time in a crank angle period in which vibration due to knock occurs;
Second A / D conversion means for A / D converting the output signal of the knock sensor every predetermined time in a crank angle period in which mechanical noise is constantly generated;
A deviation between the amplitude level of the data A / D converted by the second A / D conversion means and the amplitude level of the data A / D converted by the first A / D conversion means is calculated, and a plurality of strokes are calculated. A knock sensor device comprising knock sensor failure determination means for determining a failure of the knock sensor when the deviation continues below a failure determination level.   The maximum amplitude is taken to represent the amplitude level of the data A / D converted by the second A / D conversion means, and the amplitude level of the data A / D converted by the first A / D conversion means is taken. Taking the maximum amplitude as a representation, the maximum amplitude of the data A / D converted by the second A / D converter and the maximum amplitude of the data A / D converted by the first A / D converter The knock sensor according to claim 1, further comprising knock sensor failure determination means for determining a failure of the knock sensor when the deviation is less than a failure determination level by continuously calculating a plurality of strokes. apparatus. A knock sensor for detecting vibration caused by knock of the internal combustion engine;
First A / D conversion means for A / D converting the output signal of the knock sensor every predetermined time in a crank angle period in which vibration due to knock occurs;
Second A / D conversion means for A / D converting the output signal of the knock sensor every predetermined time in a crank angle period in which mechanical noise is constantly generated;
The first amplitude level which is the amplitude level of the data A / D converted by the first A / D conversion means and the first amplitude level which is the amplitude level of the data A / D converted by the second A / D conversion means. 2 amplitude levels are stored for each stroke over a plurality of strokes,
The deviation between the largest one of the plurality of strokes of the second amplitude level and the smallest one of the plurality of strokes of the first amplitude level is calculated, and the deviation is less than the failure determination level continuously for a plurality of times. A knock sensor device comprising knock sensor failure determination means for determining that the knock sensor has failed. Data that takes the first maximum amplitude as representing the first amplitude level of the data that has been A / D converted by the first A / D conversion means, and has been A / D converted by the second A / D conversion means Taking the second maximum amplitude as the second amplitude level, and storing the first maximum amplitude and the second maximum amplitude over a plurality of strokes for each stroke,
A deviation between a maximum one of the plurality of strokes of the second maximum amplitude and a minimum one of the plurality of strokes of the first maximum amplitude is calculated, and the deviation continuously reaches a failure determination level several times. 4. The knock sensor device according to claim 3, further comprising knock sensor failure determination means for determining that the knock sensor has failed when it falls below.   The knock sensor failure determination means determines that the knock sensor is normal when the deviation exceeds a failure determination level continuously for a plurality of strokes or a plurality of times. The knock sensor device according to claim 1.   The knock sensor device according to any one of claims 1 to 5, wherein a failure determination by the knock sensor failure determination means is performed in an operation region where the engine rotation speed is lower than a set value. A variable control means for variably controlling the injector drive timing is provided,
2. A device according to claim 1, further comprising means for setting a crank angle period during which the second A / D conversion means performs A / D conversion in accordance with an injector drive timing controlled by the variable control means. The knock sensor device according to claim 6. With a variable valve mechanism that variably controls the opening and closing timing of the intake valve or exhaust valve,
The second A / D conversion means includes means for setting a crank angle period during which A / D conversion is performed in accordance with the opening / closing timing of the intake valve or the exhaust valve controlled by the variable valve mechanism. The knock sensor device according to any one of claims 1 to 6. Variable control means for variably controlling injector drive timing;
A variable valve mechanism that variably controls the opening and closing timing of the intake valve or exhaust valve,
In an operating region where the engine speed is lower than a set value, a crank angle period during which the second A / D conversion means performs A / D conversion is set according to the injector drive timing controlled by the variable control means,
In an operating region where the engine speed is higher than the set value, the crank angle at which the second A / D conversion means performs A / D conversion in accordance with the opening / closing timing of the intake valve or exhaust valve controlled by the variable valve mechanism. The knock sensor device according to any one of claims 1 to 5, further comprising means for setting a period.

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