Hybrid vehicle engine misfire detection device

Abstract

To provide a device capable of determining or identifying cylinders having misfires when at least two cylinders have the misfires in an engine having a plurality of cylinders.SOLUTION: A hybrid vehicle engine misfire determination device comprises: plural misfire detection means (Step S2) which detects misfires in a plurality of cylinders of an engine; and misfire cylinder determination means (Steps S7-1 to S7-6) which determines the cylinders having the misfires. The misfire cylinder determination means is adapted to: sequentially switch the cylinder for which fuel supply is terminated; perform torque assist using a motor in accordance with termination of fuel supply; compare a rotation speed fluctuation pattern of the engine obtained through engine operation with the termination of the fuel supply and the torque assist with the motor with a rotation speed fluctuation pattern of the engine when a plurality of cylinders has misfires; and determine the cylinders having the misfires on the basis of a comparison result and the cylinders for which the fuel supply was terminated when the comparison result was obtained.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a misfire detection device for detecting misfire in an engine which constitutes a driving force source together with a motor in a hybrid vehicle, and more particularly to a misfire detection device for identifying a cylinder in which a misfire occurs. [Background technology]

[0002] In an engine having multiple cylinders, if a misfire occurs in any of the cylinders, unburned fuel is sent to the exhaust gas purification catalyst and combusted, which may result in deterioration or damage to the exhaust gas purification catalyst. In addition, the fluctuation of the torque output by the engine may increase, which may deteriorate the noise and vibration characteristics (NV characteristics) of the vehicle. Patent Document 1 describes a device for eliminating such inconveniences associated with misfire.

[0003] The device described in Patent Document 1 detects the presence or absence of misfires using a misfire detection means, and discriminates which cylinder is misfiring using a misfire cylinder discrimination means, and cuts fuel to the cylinder corresponding to the misfiring cylinder. In other words, if a misfire occurs in any one cylinder, the combustion interval becomes irregular, so the cylinder for which fuel is cut is selected so that the combustion interval becomes equal. As a result, combustion is no longer performed in multiple cylinders, and engine torque decreases. To compensate for this, the device in Patent Document 1 uses a motor to supplement the driving torque. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2007-069860 A Summary of the Invention [Problem to be solved by the invention]

[0005] The device described in Patent Document 1 is said to be able to identify misfiring cylinders based on the fluctuation in rotation speed during the expansion stroke of each cylinder, and when a misfire occurs in #1 cylinder, it selects #4 cylinder as the corresponding cylinder and cuts fuel to #4 cylinder, and when a misfire occurs in #2 cylinder, it selects #3 cylinder as the corresponding cylinder and cuts fuel to #3 cylinder. This type of determination of the misfiring cylinder and selection of the corresponding cylinder is possible when a misfire occurs in any one cylinder, but when a misfire occurs in, for example, any two cylinders, it is not possible to identify the misfiring cylinder.

[0006] That is, as described in Patent Document 1, the combinations of cylinders that perform fuel cut due to misfire include the combination of #1 cylinder - #4 cylinder and the combination of #2 cylinder - #3 cylinder, and in any of these combinations, combustion occurs at equal intervals, and when rotation fluctuations, for example, are detected as the operating state of the engine, the detection result is approximately the same. In other words, when a misfire occurs in each of the cylinders in the above combinations, the detectable operating state of the engine is approximately the same, so it is not possible to determine which two cylinders are misfiring based on the detection result.

[0007] Conventionally, when a misfire occurs in two or more cylinders as described above, it is difficult to determine or identify the cylinder in which the misfire occurs, making it difficult to take appropriate measures against such an abnormality. In addition, when a misfire occurs in two cylinders, there is a possibility that the system will not be able to comply with legal regulations for OBD (On-Board Diagnosis), which require a diagnostic function to identify the cylinder in which the misfire occurs.

[0008] This invention has been made in response to the above-mentioned technical problems, and has as its object to provide a device that is capable of identifying or identifying the cylinders in which misfires occur when misfires occur in at least two cylinders of a multi-cylinder engine. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, the present invention provides a misfire detection device for a hybrid vehicle which is equipped with a motor that compensates for a decrease in engine output torque and which determines whether a cylinder in the engine has misfired and which cylinder has experienced the misfire, and which includes a multiple misfire detection means for detecting misfires in multiple cylinders in the engine, and a misfiring cylinder determination means for determining which cylinder is experiencing a misfire when a misfire in the multiple cylinders is detected by the multiple misfire detection means, and which is characterized in that the misfiring cylinder determination means is configured to sequentially switch between the cylinders to which fuel supply is stopped, perform torque assist by the motor in response to the stopping of the fuel supply, compare the engine speed fluctuation pattern obtained by operating the engine with the stopping of the fuel supply and torque assist by the motor with the engine speed fluctuation pattern when a misfire has occurred in the multiple cylinders, and determine which cylinder is experiencing a misfire based on the result of the comparison and the cylinder to which the fuel supply is stopped when the result of the comparison is obtained. Effect of the Invention

[0010] According to this invention, misfire is detected in multiple cylinders. The determination can be made, for example, based on the engine speed fluctuation pattern. That is, when misfire occurs in multiple cylinders, the engine speed fluctuation pattern is different from when no misfire occurs and is a specific pattern according to the number of misfiring cylinders, so that misfire in multiple cylinders can be determined based on the engine speed fluctuation pattern. A misfire in a cylinder is a state in which no combustion of the mixture occurs in the cylinder, and is therefore similar to a state in which no fuel is supplied to the cylinder. Therefore, if the cylinder to which fuel supply is stopped is the cylinder in which misfire occurs, the rotation speed fluctuation pattern when the engine is operated with fuel supply stopped and torque assisted by the motor will be the same as the pattern in a state in which misfire occurs and fuel supply is not stopped.

[0011] In the device of the present invention, the fuel supply to each cylinder is stopped in sequence and the engine is operated to find and detect or identify the misfiring cylinder, so that if misfires occur in multiple cylinders, the cylinder in which the misfire occurred can be identified. In addition, by storing the identification results as data, misfire diagnosis by OBD becomes possible. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic diagram showing an example of a hybrid drive device in a hybrid vehicle to which the present invention is applied; [Diagram 2] 2 is a nomographic diagram of the power split mechanism. [Diagram 3] 4 is a flowchart for explaining an example of control performed by the engine misfire determination device of the present invention. [Figure 4] FIG. 1 shows engine torque and rotation speed fluctuation patterns, as well as motor assist torque, to explain the method (procedure) of this invention for determining which cylinders are misfiring. (A) shows a case where no misfire is occurring in any cylinder, (B) shows a case where misfire is occurring in cylinders #2 and #4, (C) shows a case where fuel is cut off in cylinder #1 when misfire is occurring in cylinders #2 and #4, and (D) shows a case where fuel is cut off in cylinder #2 when misfire is occurring in cylinders #2 and #4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Next, an embodiment of the present invention will be described with reference to the drawings. Note that the embodiment described below is merely one example of the case where the present invention is implemented, and is not intended to limit the present invention.

[0014] The vehicle in the embodiment of the present invention is a hybrid vehicle in which a reduction in engine output torque can be assisted by a motor, and an example of such a hybrid drive device is shown typically in Fig. 1. Engine 1 is a gasoline engine or diesel engine having multiple cylinders, such as four or six, and a power split mechanism 4 is connected to its output side via a damper 2 and a clutch 3. In the example shown here, power split mechanism 4 is configured with a single-pinion type planetary gear mechanism, and therefore power split mechanism 4 has a sun gear S as a reaction element, a ring gear R as an output element, and a carrier C as an input element that holds a pinion gear meshed with the sun gear S and the ring gear R.

[0015] Torque from the engine 1 is input to the carrier C. A brake 11 is provided to selectively stop rotation of the carrier C. A first motor (MG1) 5 is connected to the sun gear S. The ring gear R is connected to a differential gear 7, which is a final reduction gear, via an output shaft 6, and is configured to transmit driving torque from the differential gear 7 to left and right driving wheels 8. A second motor (MG2) 9 is connected to the ring gear R or the output shaft 6. The first motor 5 and second motor 9 described above are configured as motor generators that function as a motor that outputs driving torque and as a generator that generates electric power, and these motors 5 and 9 are electrically connected to each other via an inverter and an electric storage device (not shown), and are configured to send electric power generated by the first motor 5 to the second motor 9, for example, to cause the second motor 9 to output driving torque.

[0016] The operating state of the hybrid drive system shown in Fig. 1 will be explained in terms of the operating state of the power split mechanism 4. Fig. 2 is a collinear diagram of the planetary gear mechanism constituting the power split mechanism 4, in which the straight line HV indicates the operating state in hybrid mode, and the straight line EV indicates the operating state in electric driving mode. The collinear diagram shows each rotating element in the planetary gear mechanism as parallel straight lines spaced apart according to the gear ratio (the ratio between the number of teeth of the sun gear S and the number of teeth of the ring gear R), and is configured so that the dimension from a base line perpendicular to these straight lines indicates the rotation speed or torque. In the collinear diagram shown in Fig. 2, the leftmost line indicates the sun gear S and the first motor (MG1) connected thereto, the center line indicates the carrier C and the engine 1 connected thereto, and the rightmost line indicates the ring gear R and the second motor (MG2) 9 connected thereto.

[0017] In the hybrid mode, the engine 1 outputs torque in the upward direction in FIG. 2, and the rotation direction of the engine 1 is the so-called forward direction. Since the ring gear R is subjected to a running resistance in the downward direction in FIG. 2, it is necessary to output torque to overcome this resistance, and therefore the first motor 5 outputs torque in the downward direction in FIG. 2 while rotating in the forward direction. That is, the first motor 5 functions as a generator. The second motor 9 connected to the ring gear R outputs torque in the upward direction in FIG. 2 while rotating in the forward direction. That is, the second motor 9 functions as a motor, and uses the power generated by the first motor 5 as its electric power. In this way, in the hybrid mode, a part of the power output by the engine 1 is directly output from the power split mechanism 4 to the output shaft 6, and the other part is converted into electric power and then output from the second motor 9 to the output shaft 6. In the process, the first motor 5 controls the rotation speed of the engine 1 to a rotation speed at which fuel consumption or energy efficiency is good.

[0018] On the other hand, in the electric travel mode, the engine 1 is stopped and the vehicle travels with the torque of each of the motors 5, 9. That is, the first motor 5 rotates downward in FIG. 2 and outputs torque, and the reaction force acts on the ring gear R as a torque in the positive direction. That is, the first motor 5 functions as a motor. In this case, as can be seen from FIG. 2, the carrier C or the engine 1 connected thereto serves as a fulcrum to support the reaction force, so it is preferable to fix the carrier C, for example, by the above-mentioned brake 11. Also, the second motor 9 rotates upward in FIG. 2 and outputs an upward torque. That is, the second motor 9 functions as a motor. In this way, in the electric travel mode, the motors 5, 9 function as motors, and therefore, power is supplied to these motors 5, 9 from a power storage device (not shown).

[0019] In the above hybrid drive system, the torque of each motor 5, 9 can be added to or subtracted from the torque output by the engine 1, so that when the engine torque pulsates, a torque of the opposite phase to the engine torque is added to the output torque to suppress the pulsation of the drive torque and enable smooth driving. Also, when the engine torque is insufficient or decreases due to some factor, the decrease in torque can be compensated for by the torque of one of the motors 5, 9, thereby performing so-called torque assist.

[0020] The engine 1 is configured so that the supply and stop of fuel, the supply amount, the ignition timing, etc. can be electrically controlled. In addition, the operating state of each motor 5, 9, such as the torque and the direction of rotation, can be electrically controlled. An electronic control device (controller) 10 capable of performing these controls is provided. The controller 10 is mainly configured with a so-called microcomputer, and is configured to perform calculations using input data and pre-stored data, and to output the results of the calculations as control command signals. In particular, the controller 10 in the embodiment of the present invention is configured to detect misfire in any cylinder of the engine 1, compensate for the output torque associated with the misfire by the motors 5, 9, and identify or specify the cylinder in which the misfire has occurred. Therefore, the controller 10 is functionally configured to include a multiple cylinder misfire detection means 10a for detecting the occurrence of misfire in multiple cylinders, and a misfiring cylinder determination means 10b.

[0021] Next, an example of control for identifying (specifying) the cylinder in which a misfire has occurred when a misfire occurs in multiple cylinders in the engine 1 will be described. Figure 3 shows a flowchart for explaining this control example, and the control shown here is executed by the above-mentioned controller 10, which also functions as an OBD by outputting an appropriate code depending on the detected item.

[0022] In the example shown in FIG. 3, first, it is determined whether or not a misfire has been detected (step S1). This determination can be made, for example, based on the rotational fluctuation pattern of the engine 1. FIG. 4A shows the engine generated torque, a pattern indicating the rotational fluctuation, and the assist torque by the first motor 5 when normal combustion occurs in all cylinders of a six-cylinder engine. In a so-called normal operating state in which no misfire occurs, the fluctuation pattern of the engine speed (hereinafter, sometimes referred to as the speed fluctuation pattern) has a waveform with a nearly constant period and amplitude, but if a misfire occurs in any cylinder, the speed fluctuation pattern differs from that in the normal operating state. Therefore, it is possible to determine whether or not a misfire has occurred based on the detected speed fluctuation pattern.

[0023] If the determination in step S1 is negative, i.e., if no misfire has occurred, the process returns without carrying out any particular control. Conversely, if the determination in step S1 is positive, it is determined whether or not misfire has occurred in multiple cylinders (step S2). The functional means for executing this step S2 corresponds to the multiple misfire detection means in this invention. As described above, if a misfire occurs in any cylinder, the rotation speed fluctuation pattern differs from that in the case of normal operation, and the rotation speed fluctuation pattern depends on the cylinders in which misfires have occurred and the number of cylinders, etc., so the determination in step S2 can be made based on the rotation speed fluctuation pattern.

[0024] Fig. 4(B) shows the torque generated by the engine, a pattern indicating the rotational fluctuation, and the assist torque by the first motor 5 when misfires occur in the second cylinder (hereinafter referred to as the #2 cylinder) and the fourth cylinder (hereinafter referred to as the #4 cylinder) in the appropriately assigned combustion order. As can be seen from Fig. 4(B), the rotational fluctuation during the period until combustion occurs in the cylinder next to the misfiring cylinder is larger than in the case of normal operation shown in Fig. 4(A), and misfires in multiple cylinders can be determined from the difference in the rotational fluctuation pattern.

[0025] If the result of step S2 is negative, i.e., if a misfire is occurring in a single cylinder, the misfire code (single cylinder misfire code) is output (step S3), and a command is issued to stop the supply of fuel (fuel cut: F / C) to the cylinder in which the misfire is occurring (step S4), and the process returns. In the case of a misfire in a single cylinder, the cylinder in which the misfire is occurring can be identified based on the rotation fluctuation or output torque fluctuation and the crank angle. In step S4, a command is issued to cut fuel for the cylinder in which the misfire is identified.

[0026] On the other hand, if the determination in step S2 is affirmative because multiple cylinders are misfiring, the misfire code (multiple cylinder misfire code) is output (step S5). Next, it is determined whether or not the identification of the misfiring cylinder has been completed (step S6). If multiple cylinders are misfiring and the misfiring cylinder has not been identified, torque limitation is executed as fail-safe control, so the determination in step S6 can be made depending on whether or not the fail-safe torque limitation is being executed. If the determination in step S6 is negative, that is, if the misfiring cylinder has been identified, the process proceeds to the above-mentioned step S4, and a fuel cut command is issued to the misfiring cylinder.

[0027] If misfires are detected in multiple cylinders for the first time after engine 1 starts operating, the misfiring cylinder identification is not complete, and so an affirmative determination is made in step S6. In this case, active misfiring cylinder identification control is executed (step S7-1) to determine whether or not a misfire has occurred in the first cylinder (hereinafter referred to as the #1 cylinder) in an appropriate sequence assigned to the multiple cylinders. As will be described later, this active misfiring cylinder identification control is executed in sequence for each cylinder until the cylinder in which the misfire is occurring is identified, and the details of this control are as follows:

[0028] First, it is determined whether active detection for the #1 cylinder is incomplete (step S71). This determination can be made based on whether a flag or a control switch is ON. If the result of step S71 is affirmative, control of fuel cut for the #1 cylinder and torque replacement (torque assist) by the first motor (MG1) 5 is executed, and it is determined whether the control is completed (step S72).

[0029] The fuel cut control and torque replacement control will be explained with reference to Fig. 4(C). Fig. 4(C) shows a case where fuel is cut in cylinder #1 while misfires are occurring in cylinders #2 and #4. By cutting fuel in cylinder #1, torque is reduced at the timing of combustion in cylinder #1, so the negative torque by first motor 5 is reduced by a predetermined amount (increased in the positive direction) in order to reduce the negative torque to engine 1. In this state, since no torque is output during the expansion stroke in cylinder #1, the tendency for rotational speed fluctuations to increase continues, and the rotational speed fluctuation pattern remains increased as shown in Fig. 4(C), and continues until combustion occurs in the third cylinder (hereinafter referred to as cylinder #3).

[0030] In this way, by continuing the operation of engine 1 with misfire and fuel cut at a predetermined rotation speed (e.g., 200 rpm) for a predetermined period (e.g., 3 periods), it is possible to obtain the rotation speed fluctuation pattern when fuel is cut. Furthermore, since the rotation speed fluctuation pattern in this case is different from the rotation speed fluctuation pattern when misfire occurs in cylinders #2 and #4 as shown in Fig. 4(B), it is determined that no misfire occurred in cylinder #1.

[0031] In step S72, the fuel cut in the #1 cylinder and the associated torque control of the first motor 5 are executed, and it is determined whether the associated misfire determination for the #1 cylinder has been completed. Since such a misfire determination requires the engine 1 to be operated for the above-mentioned predetermined period, if the period has not elapsed, the result of step S72 is affirmative. In that case, a flag or a control switch for continuing the torque limit request is turned ON (step S8), and the program returns once.

[0032] On the other hand, if the above-mentioned predetermined period has elapsed and the misfire determination for the #1 cylinder has been completed, the answer is affirmative in step S72. In this case, the presence or absence of misfire in the #1 cylinder, i.e., whether or not the #1 cylinder is a misfiring cylinder, is determined (step S73). As described above, if the rotation speed fluctuation pattern when the engine 1 is operated by performing fuel cut for the #1 cylinder is different from the rotation speed fluctuation pattern when misfires occur in the #2 and #4 cylinders, the #1 cylinder is determined not to be a misfiring cylinder, and the answer is negative in step S73. In this case, a flag or a control switch indicating the completion of the positive determination control for the #1 cylinder is turned ON (step S74). After that, it is determined whether or not the value of the cylinder identification counter, which indicates the number of cylinders for which the presence or absence of misfire has been identified (determined), is less than "2 cylinders", in other words, whether or not it has not reached "2 cylinders" (step S76).

[0033] As described above, when the misfire cylinder identification active control has been performed only on the #1 cylinder, the result of step S76 is NO. In this case, the process proceeds to step S8 described above and then returns to perform the misfire cylinder identification active control on the other cylinders.

[0034] On the other hand, as will be explained later regarding misfire in the #2 cylinder, if the rotation speed fluctuation pattern when the engine 1 is operated with fuel cut is the same as when fuel is not cut, then combustion has not occurred in the cylinder where fuel has been cut from the start. In other words, a misfire has occurred in the cylinder where fuel has been cut. If a misfire has occurred in the #1 cylinder, the rotation speed fluctuation pattern when fuel is cut in the #1 cylinder will be the same as when fuel is not cut in the #1 cylinder, so in that case, the answer is YES in step S73. Then, the process proceeds to step S75.

[0035] In step S75, a cylinder misfire code is output, which indicates that the #1 cylinder is a misfiring cylinder. Next, the count value of a specified cylinder counter, which counts the number of times a misfiring cylinder has been specified, is increased by "1" (step S76). That is, the counter is incremented (counted up). Next, the process proceeds to the previously described step S74, where a flag or control switch indicating completion of active determination for the #1 cylinder is turned ON. After that, the process proceeds to the previously described step S76.

[0036] The control of steps S71, S72, S73, S74, S75, and S76 described above in sequence is the misfire cylinder identification active control for cylinder #1, and each time the control is completed, the cylinder identification counter is incremented. At the stage where it is determined whether or not there is a misfire for cylinder #1, the value of the cylinder identification counter has not yet reached "2 cylinders," so the routine in FIG. 3 returns. In this case, it has already been determined in step S2 that misfires have occurred in multiple cylinders, but after the return, the above-mentioned steps S1, S2, S5, and S6 are executed in sequence in the same manner as described above, and then the determination in step S71 is made. In this case, the identification (determination) for cylinder #1 has been completed, so the determination in step S71 after the return is negative.

[0037] If the determination in step S71 after the return is negative, i.e., if the active detection for the #1 cylinder is completed, the misfire cylinder identification active control for the #2 cylinder is executed (step S7-2). The content of the control is the same as the misfire cylinder identification active control for the #1 cylinder described above. Therefore, it is determined whether the active detection for the #2 cylinder is completed or not, and if it is not completed, the control of the fuel cut for the #2 cylinder and the torque replacement (torque assist) by the first motor (MG1) 5 is executed, and if the control is not completed, the process proceeds to step S8 and a flag or a control switch for continuing the torque limit request is turned ON.

[0038] The fuel cut control and torque replacement control for the #2 cylinder will be described with reference to FIG. 4(D). FIG. 4(D) shows a case where fuel is cut in the #2 cylinder when misfires occur in the #2 and #4 cylinders. By cutting fuel in the #2 cylinder, torque is reduced due to the fuel cut at the timing of combustion in the #2 cylinder, so the negative torque by the first motor 5 is reduced by a predetermined amount (increased in the positive direction) in order to reduce the negative torque to the engine 1. In this case, since the #2 cylinder is already misfiring, the rotation speed fluctuation pattern is almost the same as the pattern shown in FIG. 4(B) when fuel cut is not performed. Therefore, it is identified (determined) that a misfire occurs in the #2 cylinder based on the detected rotation speed fluctuation pattern. Note that (D) in Figure 4 is an example of a case where a misfire is occurring in the #2 cylinder as well. However, in a different case where there is no misfire in the #2 cylinder, the rotation speed fluctuation pattern when engine 1 is operated with fuel cut will be as shown in (B) in Figure 4 described above, and therefore #2 cylinder will be identified (determined) as not being a misfiring cylinder.

[0039] When the presence or absence of misfire is identified (determined) for cylinder #2 in this manner, the cylinder identification counter is counted up or not counted up, and the active determination completion flag or control switch for cylinder #2 is turned ON, just as in the case of cylinder #1 described above, and then the determination in step S9 described above is made. At the stage where the presence or absence of misfire for cylinder #2 has been determined, the value of the cylinder identification counter has not reached "2 cylinders," so the determination in step S9 is affirmative, and the process proceeds to step S8 and then returns, just as described above.

[0040] When the control returns after the misfire cylinder identification active control for the #2 cylinder (step S7-2) is completed, the determination of whether the active detection is not yet completed (step S71) in the misfire cylinder identification active control for the #1 cylinder (step S7-1) described above is negative, and the determination of whether the active detection is not yet completed in the misfire cylinder identification active control for the #2 cylinder (step S7-2) is also negative. In this case, the misfire cylinder identification active control for the #3 cylinder is executed (step S7-3). The content of the control is the same as the misfire cylinder identification active control for the #1 and #2 cylinders described above. Thereafter, the misfire cylinder identification active control is executed for each cylinder from the #4 cylinder onwards (steps S7-4 to S7-6) until the determination in step S9 is negative, that is, until the number of cylinders for which the determination of the occurrence of misfire is established reaches "2 cylinders".

[0041] In the example shown in Fig. 4, misfires occur in cylinders #2 and #4, so a negative determination is made in step S9 when the misfiring cylinder identification active control for cylinder #4 is completed. If a negative determination is made in step S9, that is, if misfires occur in two cylinders and the identification of the misfiring cylinders is completed, the process proceeds to step S4 described above, where a fuel cut command is issued for the misfiring cylinder, and the process returns. Therefore, the functional means for executing steps S7-1 to S7-6 described above corresponds to the misfiring cylinder determination means in this invention.

[0042] As described above, in the embodiment of the present invention, when misfires are detected in multiple cylinders, fuel is cut off for each cylinder in turn, and the cylinder whose rotation speed fluctuation pattern when fuel is cut off is the same as that when fuel is not cut off is detected, so that the misfiring cylinder can be identified (determined) reliably. Then, the result of the determination is output as a code, making it possible to diagnose misfires by OBD.

[0043] It should be noted that the present invention is not limited to the above-described embodiment, and the engine to which the present invention is applied may be any engine having multiple cylinders, and may be an engine other than a six-cylinder engine. Also, the hybrid vehicle to which the present invention is applied is not limited to a vehicle equipped with a hybrid drive device having the configuration shown in Fig. 1, and in short, may be any hybrid vehicle equipped with a hybrid drive device configured to assist the drive torque by a motor. [Explanation of symbols]

[0044] 1 Engine 2 Damper 3. Clutch 4 Power split mechanism 5. First motor (MG1) 6 Output shaft 7 Differential Gear 8 Drive wheels 9 Second motor (MG2) 10 Controller 10a Multiple cylinder misfire detection means 10b Misfiring cylinder determination means 11. Brakes C Carrier R ring gear S Sun gear

Claims

1. A misfire determination device for a hybrid vehicle, comprising: a motor that compensates for a decrease in an output torque of an engine; and the device determines whether a misfire has occurred in a cylinder of the engine and which cylinder has the misfire, a multiple misfire detection means for detecting misfires in multiple cylinders of the engine; a misfire cylinder determination means for determining a cylinder in which a misfire is occurring when the misfire is detected in the plurality of cylinders by the plurality of misfire detection means, The misfire cylinder determination means Switching the cylinders to which fuel supply is to be stopped in sequence; performing torque assist by the motor in response to the stop of the supply of the fuel; comparing a rotation speed fluctuation pattern of the engine obtained by operating the engine by stopping the supply of fuel and performing torque assist by the motor with a rotation speed fluctuation pattern of the engine when a misfire occurs in the plurality of cylinders; The cylinder in which the misfire is occurring is determined based on the result of the comparison and the cylinder to which the fuel supply is stopped when the result of the comparison is obtained.

1. A hybrid vehicle engine misfire detection device comprising:

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