Engine diagnostic equipment

Abstract

To allow abnormal combustion of an engine to be appropriately determined according to a degree of deterioration of the engine.SOLUTION: An ignition timing retard amount-RET when a knock is detected is read on the basis of a signal from a knock sensor 21 (S3), a retard amount integration value-SRET integrating the ignition timing retard amount RET is calculated (S5), an accumulation retard amount integration value-TSRET is calculated by accumulating the retard amount integration values-SRET calculated at the time of knock detection (S6), the accumulation retard amount integration value-TSRET and a deterioration determination threshold value-TSREO set beforehand are compared to each other, and in the case of -TSRET>-TSREO, an abnormal combustion determination threshold value-SREO is set with a standard level determination value-SRES (S8). In the case of -TSRET≤-TSREO and -SRET>-SERO, an abnormal combustion determination threshold value-SREO is set with a high level determination value-SREH (S10).SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an engine diagnostic device that can appropriately determine abnormal combustion in an engine according to the degree of deterioration. [Background technology]

[0002] The engine ignition timing is optimally set by executing trace knock control, MBT (Minimum advance for the Best Torque) control, etc. according to the engine load. If the engine ignition timing is advanced beyond the knock limit, knocking is more likely to occur inside the combustion chamber (cylinder), so when the knock sensor detects knocking, the ignition timing must be immediately retarded to avoid knocking.

[0003] If combustion in the cylinder is normal, when the knock sensor detects a knock, the knock can be avoided and normal combustion can be restored immediately by retarding the ignition timing by a few degrees.

[0004] However, if the fuel quality is poor, if there is a malfunction in the ignition system (such as a momentary current interruption due to wear on the ignition coil terminals), or if the air-fuel ratio sensor degrades and the actual air-fuel ratio deviates from the measured value, the ignition timing will not be controlled properly. As a result, when the knock sensor detects knock caused by abnormal combustion, it is difficult to effectively prevent the occurrence of knock even if the ignition timing is retarded by several degrees. Furthermore, the retardation of the ignition timing can lead to continuous afterburning, which can cause problems such as an abnormal rise in the exhaust temperature.

[0005] As a countermeasure to this problem, for example, Patent Document 1 (Patent Publication No. 4262260) discloses a technology in which the amount of retardation of the ignition timing is accumulated and compared with a preset threshold value. If the accumulated value of the retardation amount exceeds the threshold value, it is determined that an abnormality has occurred that causes a deterioration in engine fuel efficiency, and abnormality recovery processing is performed. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 4262260 Summary of the Invention [Problem to be solved by the invention]

[0007] However, as engine deterioration progresses, the probability of engine failure due to knocking increases. However, the technology disclosed in the above-mentioned document compares the integrated value of the retard amount with a preset threshold value to uniquely determine an abnormality regardless of the degree of engine deterioration, which is inconvenient in that it may be difficult to properly determine an abnormality according to the degree of engine deterioration.

[0008] SUMMARY OF THE PRESENT INVETION The present invention has been made in consideration of the above circumstances, and has an object to provide an engine diagnostic device that can appropriately determine abnormal combustion in an engine according to the degree of deterioration of the engine. [Means for solving the problem]

[0009] The present invention includes a knock detection unit that detects a knock based on a signal from a knock detection sensor; The amount of retard of the ignition timing when the knock is detected by the knock detection unit is read, and a retard amount integral value, which is an integral value of the amount of retard of the ignition timing, is calculated. If no knock is detected by the knock detection unit, the retard amount integral value is cleared. an abnormal combustion judgment threshold setting unit that sets an abnormal combustion judgment threshold based on the accumulated parameter calculated by the accumulated parameter calculation unit; and an abnormal combustion judgment unit that judges whether or not combustion in the engine is abnormal by comparing the retard amount integral calculated by the retard amount integral calculation unit with the abnormal combustion judgment threshold set by the abnormal combustion judgment threshold setting unit. compares the cumulative parameter with a preset deterioration determination threshold value, and if the cumulative parameter does not exceed the deterioration determination threshold value, sets the abnormal combustion determination threshold value to a preset reference value;When the cumulative parameter exceeds the deterioration judgment threshold value and the retard amount integral value calculated by the retard amount integral value calculation unit does not exceed the abnormal combustion judgment threshold value set by the abnormal combustion judgment threshold value setting unit, Absolute value higher than the reference value Set it to a high value. Effect of the Invention

[0010] According to the present invention, an abnormal combustion judgment threshold is set based on an accumulated parameter calculated by accumulating parameters which are factors of the degree of engine deterioration, and this abnormal combustion judgment threshold is compared with an integrated retard amount value which is the integrated value of the ignition timing retard amount read when knock is detected to determine whether engine combustion is abnormal or not. The accumulated parameter is compared with a preset deterioration judgment threshold, and if the accumulated parameter exceeds the deterioration judgment threshold value and the integrated retard amount value does not exceed the abnormal combustion judgment threshold value, the abnormal combustion judgment threshold is set to a high value, so that abnormal combustion in the engine can be appropriately judged according to the degree of engine deterioration. [Brief description of the drawings]

[0011] [Figure 1] Schematic diagram of diagnostic device [Diagram 2] Flowchart showing deterioration diagnosis routine [Diagram 3] A time chart showing the relationship between the knock sensor output value and the knock determination threshold value. [Figure 4] (a) is a time chart showing the change in engine speed at full load, (b) is a time chart showing the change in the amount of ignition timing retard when knock is detected, (c) is a time chart showing the change in the integral value of the retard amount and the integral value of the accumulated retard amount, (d) is a time chart showing the switching of the check engine flag, and (e) is a time chart showing the change in the ignition advance angle. [Diagram 5] A flowchart showing a deterioration diagnosis routine according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] An embodiment of the present invention will be described below with reference to the drawings. An engine diagnostic device 1 shown in Fig. 1 has an abnormal combustion diagnostic unit 11. This abnormal combustion diagnostic unit 11 is composed of a microcomputer having a known CPU, ROM, RAM, non-volatile memory such as a flash memory, and peripheral devices thereof.

[0013] A knock sensor 21 serving as a knock detector is connected to the input side of the abnormal combustion diagnosis section 11, and ignition timing retard amount data obtained by an ignition control unit (not shown) and accumulated mileage data obtained by a combination meter control unit and displayed on an odometer are input to the input side of the abnormal combustion diagnosis section 11. A fuel injection device 31, a check engine lamp 32, and an external connector 33 are connected to the output side of the abnormal combustion diagnosis section 11. The knock sensor 21 is also used by the ignition timing control unit.

[0014] When a knock is detected by the knock sensor 21, the abnormal combustion diagnosis section 11 reads the negative ignition timing retard amount -RET calculated by an ignition timing control unit (not shown) and integrates it over a calculation period to calculate a negative retard amount integral value -SRET (-SRET←-SRET-RET). This retard amount integral value -SRET is compared with the abnormal combustion determination threshold value -SREO every time a knock is detected in step S9 of a deterioration diagnosis routine (described later).

[0015] Incidentally, the ignition timing control unit performs so-called trace knock control, in which the ignition timing is feedforward controlled to the advance side within a range in which the intensity and frequency of knocks are within a preset knock judgment threshold based on a signal from a knock sensor 21 as shown in Fig. 3, and the ignition timing is retarded as much as possible by a predetermined angle when a knock exceeding the knock judgment threshold is detected, as will be described later. Therefore, the abnormal combustion diagnosis unit 11 may obtain information on the occurrence of knocks from the ignition timing control unit.

[0016] On the other hand, if no knock is detected by the knock sensor 21 during calculation, the retard amount integral value -SRET is cleared (-SRET←0). If this retard amount integral value -SRET exceeds the deterioration determination threshold value -SREO (-SRET≦-SREO), it is determined that abnormal combustion is occurring due to engine deterioration.

[0017] If the abnormal combustion diagnosis unit 11 judges that abnormal combustion is due to engine deterioration, it sends a fuel increase signal to the fuel injection device 31 to temporarily increase the amount of fuel injected into the target cylinder and cool the fuel inside the cylinder with the heat of vaporization. Then, it lights or blinks a check engine lamp 32 arranged on a combination meter or the like to notify the driver of abnormal combustion, and stores a trouble code indicating abnormal combustion due to engine deterioration in non-volatile memory.

[0018] On the other hand, a fault diagnosis device 34 at the dealer is connected to the external connection connector 33, and reads the trouble codes stored in the non-volatile memory of the abnormal combustion diagnosis unit 11, thereby allowing an operator to ascertain the cause of the malfunction.

[0019] Specifically, the engine deterioration diagnosis executed by the abnormal combustion diagnosis unit 11 described above is performed according to the deterioration diagnosis routine shown in Fig. 2. In this routine, first, in step S1, the output value detected by the knock sensor 21 (knock sensor output value) is read, and in step S2, it is determined whether or not a knock has been detected. Fig. 3 shows the knock sensor output value. The knock sensor 21 is composed of a piezoelectric element or the like, and is attached to the engine block to detect the vibration waveform of the engine block. The abnormal combustion diagnosis unit 11 compares the vibration waveform detected by the knock sensor 21 with a preset knock judgment threshold, and if the amplitude of the vibration waveform exceeds the knock judgment threshold, it judges that a knock has been detected.

[0020] If the abnormal combustion diagnosis unit 11 determines that a knock has been detected, the process proceeds to step S3, where the retard amount -RET calculated by the ignition timing control unit and given a negative sign is read, and the process proceeds to step S5. If the knock sensor output value is within the knock determination threshold, it is determined that a knock has not occurred, and the process branches to step S4, where the retard amount integral value -SRET is cleared (-SRET←0), and the routine ends. Note that this retard amount integral value -SRET is calculated in step S5, which will be described later.

[0021] In step S5, the retard amount -RET read in step S3 is integrated to obtain a retard amount integral value -SRET with a negative sign (-SRET←-SRET-RET), and the process proceeds to step S6. The processes in steps S3 and S5 correspond to the retard amount integral value calculation unit of the present invention. Also, this retard amount -RET corresponds to a parameter that is a factor of the deterioration degree of the engine.

[0022] In step S6, the retard amount integral value -SRET obtained in step S5 is accumulated to obtain an accumulated retard amount integral value -TSRET (-TSRET←-TSRET-SRET). Note that the process in step S6 corresponds to the accumulated parameter calculation unit of the present invention, and the accumulated retard amount integral value -TSRET corresponds to the accumulated parameter.

[0023] Next, the process proceeds to step S7, where the cumulative retard amount integral value -TSRET is compared with a deterioration determination threshold value -TSREO, which is a value for estimating engine deterioration and is previously determined through experiments or the like.

[0024] As the deterioration of the engine progresses, a malfunction due to knocking becomes more likely to occur. Therefore, the abnormal combustion judgment threshold value -SREO, which will be described later, is varied depending on whether the cumulative retard amount integral value -TSRET exceeds the deterioration judgment threshold value -TSREO. In this embodiment, -TSREO is set to a value of about -800 to -1500 [deg·sec].

[0025] Then, if the cumulative retard amount integral value -TSRET does not reach the deterioration judgment threshold value -TSREO (-TSRET>-TSREO), the process branches to step S8, where the abnormal combustion judgment threshold value -SREO is set to the reference level judgment value -SRES (see FIG. 4(c)) (-SREO←-SRES), and the process proceeds to step S9. On the other hand, if the cumulative retard amount integral value -TSRET reaches the deterioration judgment threshold value -TSREO (-TSRET≦-TSREO), the process proceeds to step S9. In this embodiment, the reference level judgment value -SRES is set to approximately -120 [deg·sec].

[0026] Thereafter, when the process proceeds from step S7 or step S8 to step S9, the retard amount integral value -SRET is compared with the abnormal combustion judgment threshold value -SREO. If -SRET>-SREO, the engine combustion state is judged to be normal, and the process proceeds to step S10. If -SRET≦-SREO, the process branches to step S12. The process in step S9 corresponds to the abnormal combustion judgment unit of the present invention.

[0027] When the process proceeds to step S10, the abnormal combustion judgment threshold value -SREO is set to a high level judgment value -SREH (see FIG. 4(c)) that is higher (in absolute value) than the reference level judgment value -SRES (-SREO←-SREH), and the process proceeds to step S11. If the abnormal combustion judgment threshold value -SRES set by the reference level judgment value -SRES is not exceeded even if the deterioration of the engine progresses, it is determined that the possibility of a malfunction due to knock is low, and the abnormal combustion judgment threshold value -SREO is set to a high level judgment value -SREH that is higher than the reference level judgment value -SRES. This makes it possible to properly judge abnormal combustion in the engine according to the degree of deterioration of the engine. In this embodiment, the high level judgment value -SREH is set to about -150 [deg·sec]. Moreover, the processes in steps S7, S8, and S10 correspond to the abnormal combustion judgment threshold value setting unit of the present invention. Moreover, the processes in steps S7, S8, and S10 correspond to the abnormal combustion judgment threshold value setting unit of the present invention.

[0028] Thereafter, when the process proceeds from step S10 to step S11, the check engine flag Fw is cleared (Fw←0) and the routine ends.

[0029] Furthermore, when the process proceeds from step S9 to step S12, a fuel increase signal is sent to the fuel injector 31, and the process proceeds to step S13. As a result, the amount of fuel injected from the fuel injector 31 into the cylinder determined to be undergoing abnormal combustion is increased, and the in-cylinder temperature is reduced by cooling the fuel.

[0030] After that, the process proceeds to step S13, where the check engine flag Fw is set (Fw←0), Go to step S14 When the check engine flag Fw is set, the abnormal combustion diagnostic unit 11 notifies the driver of the engine abnormality by turning on or blinking a check engine lamp 32 disposed on a combination meter or the like.

[0031] Next, proceed to step S14. Muto The trouble code corresponding to the abnormal combustion of the engine is stored in the non-volatile memory, and the routine is terminated. The trouble code stored in the non-volatile memory can be read by connecting the fault diagnosis device 34 to the external connection connector 33 at the dealer.

[0032] Next, an example of engine deterioration diagnosis by the deterioration diagnosis routine shown in Fig. 2 will be described with reference to the time chart shown in Fig. 4. As shown in Fig. 4(a), when high load and high revolution are continued for a certain period of time, if the abnormal combustion diagnosis unit 11 detects a knock based on the knock sensor output value, the retard amount -RET calculated by the ignition timing control unit as shown in Fig. 4(b) is read (S3).

[0033] Then, as shown by the thin solid line in Figure 4(c), the retard amount integrated value -SRET obtained by integrating this retard amount -RET is set (S5), and the cumulative retard amount integrated value -TSRET shown by the thick solid line is set (S6). After that, when knock is no longer detected, the retard amount integrated value -SRET is cleared (S4), but the cumulative retard amount integrated value -TSRET is maintained.

[0034] If the retard amount integral value -SRET falls below the deterioration determination threshold value -SREO (S9), it is determined that abnormal combustion has occurred, and the check engine flag Fw is set as shown in FIG. 4(d) (S13), and the check engine lamp 32 is turned on or flashed.

[0035] As shown in Fig. 4(c), the abnormal combustion judgment threshold value -SREO is set to the reference level judgment value -SRES (S8) until the cumulative retard amount integral value -TSRET reaches the deterioration judgment threshold value -TSREO, and when the cumulative retard amount integral value -TSRET exceeds the deterioration judgment threshold value -TSREO, it is set to the high level judgment value -SREH (S10). Note that Fig. 4(e) shows the ignition advance angle [BTDCdeg] synchronized with the ignition timing retard amount -ERT.

[0036] Thus, according to this embodiment, even if the cumulative retard amount integral value -TSRET, which is a factor of the deterioration degree of the engine, exceeds a preset deterioration judgment threshold value -TSREO, if the retard amount integral value -SRET does not exceed the abnormal combustion judgment threshold value -SREO set by the reference level judgment value -SRES, this abnormal combustion judgment threshold value -SREO is set to the high level judgment value -SREH higher than the reference level judgment value -SRES, so that abnormal combustion in the engine can be properly judged even if the deterioration of the engine has progressed. Note that after the abnormal combustion judgment threshold value -SREO is set to the high level judgment value -SREH, this abnormal combustion judgment threshold value -SREO is not returned to the reference level judgment value -SRES. [Variations] FIG. 5 shows a modification of the present embodiment. In the above-described embodiment, the abnormal combustion determination threshold value - SREO is switched according to the integrated retard amount integral value - TSRET, but in the present embodiment, the abnormal combustion determination threshold value - SREO is switched according to the cumulative travel distance TD.

[0037] That is, as shown in the flowchart of FIG. 5, up to steps S1 to S5, the same processing as the flowchart shown in FIG. 2 is executed. When proceeding from step S5 to step S21, the cumulative travel distance TD of the host vehicle calculated on the combination meter control unit side is read. Therefore, the processing in this step S21 corresponds to the cumulative parameter calculation unit of the present invention, and the cumulative travel distance TD corresponds to the cumulative parameter.

[0038] Then, in step S22, the cumulative travel distance TD is compared with a preset deterioration determination threshold value DO. This deterioration determination threshold value DO is a value for estimating the deterioration of the engine and is obtained and set in advance through experiments or the like. Incidentally, in the present embodiment, it is set to a distance of about DO = 40000 to 60000 [Km]. The degree of engine deterioration can be roughly estimated from the cumulative travel distance TD, and as the deterioration progresses, a failure due to knocking is likely to occur. In this case, conversely, even if the cumulative travel distance TD exceeds the deterioration determination threshold value DO, if the retard amount integral value - SRET does not exceed the abnormal combustion determination threshold value - SREO set by the reference level determination value - SRES, it can be determined that the possibility of a failure due to knocking is low.

[0039] When the cumulative travel distance TD has not reached the deterioration determination threshold value DO (TD < DO), the process proceeds to step S8. When the cumulative travel distance TD has reached the deterioration determination threshold value DO (TD ≧ DO), the process branches to step S9. Subsequently, in steps S8, S9 and later, the same processing as the processing in FIG. 2 described above is executed. Note that the processing in steps S22, S8, and S10 corresponds to the abnormal combustion determination threshold value setting unit of the present invention.

[0040] In this manner, in the above-described modified example, the degree of engine deterioration is estimated based on the cumulative mileage TD, so that the degree of engine deterioration can be estimated relatively easily compared to the above-described embodiment.

[0041] The present invention is not limited to the above-described embodiment and modified examples. For example, the abnormal combustion determination threshold value -SREO may be variably set to a more finely divided value in accordance with the integrated value -TSRET of the accumulated retard amount or the accumulated mileage TD. [Explanation of symbols]

[0042] 1...Diagnostic equipment, 11…Abnormal combustion diagnosis section, 21...Knock sensor, 31...fuel injection device, 32…Check engine light, 33…External connection connector, DO: Deterioration judgment threshold, Fw…Check engine flag, -RET: Amount of ignition timing retard, -SREH: high level judgment value, -SREO: Abnormal combustion judgment threshold, -SRES: Reference level judgment value, -SRET: Retard amount integral value, -TSREO: Deterioration judgment threshold value, -TSRET: Accumulated retard amount integral value, TD: cumulative distance traveled

Claims

1. A knock detection unit that detects a knock based on a signal from a knock detection sensor; a retard amount integral value calculation unit that reads an ignition timing retard amount when a knock is detected by the knock detection unit, calculates a retard amount integral value that is an integral value of the ignition timing retard amount, and clears the retard amount integral value when a knock is not detected by the knock detection unit; an accumulated parameter calculation unit that accumulates parameters that are factors of the deterioration degree of the engine to calculate an accumulated parameter; an abnormal combustion determination threshold setting unit that sets an abnormal combustion determination threshold based on the cumulative parameters calculated by the cumulative parameter calculation unit; an abnormal combustion determination unit that compares the retard amount integral value calculated by the retard amount integral value calculation unit with the abnormal combustion determination threshold value set by the abnormal combustion determination threshold value setting unit to determine whether or not engine combustion is abnormal; An engine diagnostic device comprising: The abnormal combustion judgment threshold setting unit compares the cumulative parameter with a preset deterioration judgment threshold, and if the cumulative parameter does not exceed the deterioration judgment threshold, sets the abnormal combustion judgment threshold to a preset reference value, and if the cumulative parameter exceeds the deterioration judgment threshold and the retard amount integral value calculated by the retard amount integral value calculation unit does not exceed the abnormal combustion judgment threshold value set by the abnormal combustion judgment threshold setting unit, sets the abnormal combustion judgment threshold to a value higher in absolute value than the reference value. An engine diagnostic device comprising:

2. The cumulative parameter calculated by the cumulative parameter calculation unit is a cumulative retard amount integral value obtained by accumulating the retard amount integral value calculated by the retard amount integral value calculation unit when a knock is detected.

2. The engine diagnostic device according to claim 1.

3. The cumulative parameter calculated by the cumulative parameter calculation unit is a cumulative travel distance.

2. The engine diagnostic device according to claim 1.

4. The retard amount integral value calculated by the retard amount integral value calculation unit is cleared when no knock is detected by the knock detection unit.

4. The engine diagnostic device according to claim 1, wherein the engine diagnostic device is a diagnostic device for an engine.

5. When the abnormal combustion determination unit determines that the engine combustion is abnormal, the amount of fuel supplied to the abnormal combustion cylinder is increased.

5. The engine diagnostic device according to claim 1, wherein the engine diagnostic device is a diagnostic device for an engine.

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