JP5056636B2 - Variable compression ratio internal combustion engine and variable compression ratio mechanism abnormality determination method - Google Patents

Description

  The present invention relates to a variable compression ratio internal combustion engine including a variable compression ratio mechanism that controls a compression ratio in an internal combustion engine, and an abnormality determination method for the variable compression ratio mechanism.

  In recent years, a technique has been proposed that includes a variable compression ratio mechanism that makes the compression ratio of an internal combustion engine variable for the purpose of improving the fuel efficiency performance and output performance of the internal combustion engine. As this type of technology, the cylinder block and the crankcase are connected so as to be relatively movable, and a camshaft is provided at the connecting portion, and the camshaft is rotated to connect the cylinder block and the crankcase in the axial direction of the cylinder. A technique for changing the volume of the combustion chamber by relatively moving the internal combustion engine and thus changing the compression ratio of the internal combustion engine is known (see, for example, Patent Document 1).

  As another variable compression ratio mechanism, the connecting rod is divided into two, and a connecting member connected to the crankshaft is connected to a swinging member that can swing around a predetermined swinging center. Has also proposed a mechanism for changing the compression ratio of the internal combustion engine by changing the volume of the combustion chamber and the stroke of the piston by moving by rotating the camshaft (see, for example, Patent Document 2). ).

  However, in the variable compression ratio internal combustion engine as described above, if the variable compression ratio mechanism does not operate normally for some reason, the compression ratio becomes excessively low and combustion becomes unstable, or the compression ratio is excessive. The combustion state may become abnormal, for example, knocking may occur. Therefore, it is necessary to confirm in a timely manner that the variable compression ratio mechanism is operating normally.

  In this regard, an air-fuel ratio control means for controlling the air-fuel ratio to a predetermined air-fuel ratio and a compression ratio variable mechanism are provided, a pressure sensor for detecting the combustion pressure of the engine, and a combustion for detecting the combustion speed from a change in the combustion pressure. A speed detection means, a reference value setting means for setting a reference value for the combustion speed in accordance with the engine operating conditions, and an abnormality determination means for comparing the reference value with the actual combustion speed to determine an abnormality in the compression ratio. The technology provided is known (see, for example, Patent Document 3).

However, the above-mentioned failure detection requires a special pressure sensor, its drive circuit and signal processing circuit, which may cause problems such as an increase in cost and a decrease in durability of the internal combustion engine due to the provision of the sensor. .
JP 2003-206871 A JP 2001-317383 A No. 6-4049 JP 2003-161175 A JP 2003-148230 A

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a technique capable of determining abnormality of the variable compression ratio mechanism with a simpler configuration or processing. .

In order to achieve the above object, the present invention acquires the temperature of the exhaust gas of an internal combustion engine, and performs variable compression based on whether the acquired temperature is a reasonable temperature with respect to the compression ratio set by the variable compression ratio mechanism. The greatest feature is to perform abnormality determination of the ratio mechanism.

More specifically, a variable compression ratio mechanism capable of changing the compression ratio of the internal combustion engine,
Compression ratio control means for setting the compression ratio to a target compression ratio by the variable compression ratio mechanism;
Temperature acquisition means for acquiring the temperature of the exhaust from the internal combustion engine;
The target compression ratio set by the compression ratio control means or an index value related to the target compression ratio, and the exhaust temperature acquired by the temperature acquisition means in a state where the compression ratio is set to the target compression ratio, An abnormality determining means for determining an abnormality of the variable compression ratio mechanism;
It is characterized by providing.

  Here, when the compression ratio of the internal combustion engine is high, since the combustion efficiency is high, more of the energy that the fuel has becomes engine output, and the temperature of the exhaust gas becomes relatively low. On the other hand, when the compression ratio is low, since the combustion efficiency is low, the portion of the energy that the fuel has becomes the engine output decreases, and on the other hand, the energy that did not become the engine output is given to the exhaust. Rises relatively.

  Therefore, the temperature of the exhaust gas of the internal combustion engine has a high correlation with the compression ratio of the internal combustion engine. The present invention focuses on the correlation between the exhaust gas temperature of the internal combustion engine and the compression ratio. That is, it is determined whether or not the exhaust temperature is appropriate for the target compression ratio set by the compression ratio control means, and the exhaust temperature is not appropriate for the target compression ratio set by the compression ratio control means. Determines that the operation of the variable compression ratio mechanism is abnormal. The abnormality determination may use the target compression ratio value itself set by the compression ratio control means, or may use an index value related to the target compression ratio. The index value related to the target compression ratio may be a value that can be an alternative amount of the target compression ratio, such as a control instruction amount for the variable compression ratio mechanism. Moreover, the value etc. which converted the target compression ratio into the temperature of the exhaust gas corresponding to the compression ratio may be used.

  According to this, abnormality determination of the variable compression ratio mechanism can be performed with a simple configuration.

In the present invention, air-fuel ratio switching means for changing the air-fuel ratio of the exhaust from the internal combustion engine,
An exhaust purification catalyst that is provided in an exhaust passage through which exhaust from the internal combustion engine flows, and purifies exhaust that passes through the exhaust passage;
An upstream air-fuel ratio sensor that detects an upstream air-fuel ratio that is an air-fuel ratio of the exhaust gas upstream of the exhaust purification catalyst in the exhaust passage;
A downstream air-fuel ratio sensor that detects a downstream air-fuel ratio that is an air-fuel ratio of the exhaust gas on the downstream side of the exhaust purification catalyst in the exhaust passage,
The temperature acquisition means includes
The temperature of the exhaust gas is acquired by the difference between the change timing of the upstream air-fuel ratio and the change timing of the downstream air-fuel ratio when the air-fuel ratio switching means changes the air-fuel ratio of the exhaust gas. Also good.

Here, the exhaust passage of the internal combustion engine is provided with an exhaust purification catalyst such as a three-way catalyst or a NOx storage reduction catalyst, and further, the upstream side for detecting the upstream air-fuel ratio (upstream air-fuel ratio) of the exhaust purification catalyst. An air-fuel ratio sensor and a downstream air-fuel ratio sensor for detecting an air-fuel ratio downstream of the exhaust purification catalyst (downstream air-fuel ratio) are provided. Further, for example, an air-fuel ratio switching means for controlling the air-fuel ratio of the exhaust by increasing the fuel injection amount of the internal combustion engine or performing sub-injection is provided.

In this case, when the temperature of the exhaust gas is low, the temperature of the exhaust gas purification catalyst is also low, so that the moving speed of O ₂ in the exhaust gas purification catalyst becomes slow. Then, for example, immediately after the air-fuel ratio changes (reverses) from lean to rich, unburned components of fuel such as HC and CO hardly react with O ₂ when passing through the exhaust purification catalyst. It becomes easy to be discharged without being oxidized. As a result, the downstream air-fuel ratio detected by the downstream air-fuel ratio sensor changes relatively quickly and steeply.

On the other hand, when the exhaust gas temperature is high, the moving speed of O ₂ in the exhaust gas purification catalyst becomes faster. Then, immediately after the air-fuel ratio changes (reverses) from lean to rich, unburned components of fuel such as HC and CO easily react with O ₂ when passing through the exhaust purification catalyst, and conversely, the exhaust purification catalyst. It becomes difficult to be discharged from unoxidized. Then, O ₂ in the catalyst is consumed, and after the reaction between HC, CO, etc. and O ₂ is collected, HC, CO, etc. pass through the exhaust purification catalyst and are discharged downstream. As a result, the value of the downstream air-fuel ratio detected by the downstream air-fuel ratio sensor changes relatively slowly, and the change also becomes gradual.

  In the present invention, focusing on this, the difference between the change timing of the upstream air-fuel ratio detected by the upstream air-fuel ratio sensor and the change timing of the downstream air-fuel ratio detected by the downstream air-fuel ratio sensor is described above. We decided to acquire the temperature of the exhaust. According to this, it is not necessary to provide a new sensor or the like for temperature acquisition, the exhaust temperature can be acquired with a simple configuration, and abnormality determination of the variable compression ratio mechanism is performed using this temperature. be able to. As a result, the cost reduction of the apparatus can be promoted, the necessity of performing new sensor deterioration detection can be eliminated, and the control of the apparatus can be simplified.

  In the present invention, the abnormality determination means derives an actual compression ratio from the exhaust gas temperature acquired by the temperature acquisition means in a state where the compression ratio is set to the target compression ratio, and the target compression ratio When the difference between the actual compression ratio and the actual compression ratio is larger than a predetermined value, the variable compression ratio mechanism may be determined to be abnormal.

  Here, as described above, there is a high correlation between the compression ratio of the internal combustion engine and the exhaust temperature. Therefore, in the present invention, the abnormality determination means derives the actual compression ratio from the exhaust temperature acquired by the temperature acquisition means in a state where the compression ratio is set to the target compression ratio, and the derived actual compression ratio. And the target compression ratio are compared, and if the difference is greater than a predetermined value, the variable compression ratio mechanism is determined to be abnormal. Here, the predetermined value is a threshold value that allows the variable compression ratio mechanism to be determined to be abnormal when the actual compression ratio obtained from the exhaust gas temperature and the target compression ratio are larger than this, such as an experiment in advance. Is a value obtained by.

  According to this, it is possible to detect an abnormality of the variable compression ratio mechanism with a simple configuration and technique with higher accuracy.

  Further, in the present invention, the abnormality determination means is a first actual ratio that is an actual compression ratio from an exhaust gas temperature acquired by the temperature acquisition means in a state where the compression ratio is set to a predetermined first target compression ratio. Deriving a compression ratio, deriving a second actual compression ratio that is an actual compression ratio from the temperature of the exhaust gas acquired by the temperature acquisition means in a state where the compression ratio is set to a predetermined second target compression ratio, When the difference between the first target compression ratio and the second target compression ratio and the difference between the first actual compression ratio and the second actual compression ratio are larger than a predetermined value, the variable compression ratio mechanism is abnormal. You may make it determine.

  According to this, since it is possible to determine the abnormality of the variable compression ratio mechanism based on whether or not the actual change in the compression ratio is sufficiently close to the change in the target compression ratio, the actual compression ratio can be determined. Since the error factor of the absolute value at the time of deriving the ratio can be canceled, the abnormality of the variable compression ratio mechanism can be detected with higher accuracy.

  Further, in the present invention, the operation of the exhaust purification catalyst may be confirmed before the abnormality determination means performs abnormality determination of the variable compression ratio mechanism. In addition, before the abnormality determination unit performs abnormality determination of the variable compression ratio mechanism, the operation of the upstream air-fuel ratio sensor and / or the downstream air-fuel ratio sensor may be confirmed.

  Thus, after confirming that the exhaust purification catalyst operates normally or that the air-fuel ratio sensor operates normally, the difference between the change timing of the upstream air-fuel ratio and the change timing of the downstream air-fuel ratio is calculated. To obtain the temperature of the exhaust. Therefore, the abnormality determination of the variable compression ratio mechanism can be performed more accurately.

The present invention also provides a variable compression ratio mechanism capable of changing the compression ratio of the internal combustion engine,
Compression ratio control means for setting the compression ratio to a target compression ratio by the variable compression ratio mechanism;
Air-fuel ratio switching means for changing the air-fuel ratio of the exhaust from the internal combustion engine;
An exhaust purification catalyst that is provided in an exhaust passage through which exhaust from the internal combustion engine flows, and purifies the exhaust;
An abnormality determination method for a variable compression ratio mechanism in a variable compression ratio internal combustion engine comprising:
When the air-fuel ratio switching means changes the air-fuel ratio of the exhaust gas, the timing of change of the air-fuel ratio upstream of the exhaust purification catalyst and the timing of change of the air-fuel ratio downstream of the exhaust purification catalyst An abnormality determination method for a variable compression ratio mechanism, wherein abnormality determination for the variable compression ratio mechanism is performed based on a time difference and the target compression ratio.

  According to this, abnormality determination of the variable compression ratio mechanism can be performed by simpler processing.

The abnormality determination method for the variable compression ratio mechanism includes a compression ratio setting step of setting a compression ratio to a target compression ratio by the variable compression ratio mechanism,
An air-fuel ratio switching step in which the air-fuel ratio switching means changes the air-fuel ratio of the exhaust;
A time difference detecting step of detecting a time difference between a change timing of the air-fuel ratio upstream of the exhaust purification catalyst when the air-fuel ratio is changed and a change timing of the air-fuel ratio downstream of the exhaust purification catalyst;
An actual compression ratio derivation step for deriving an actual compression ratio from the time difference detected in the time difference detection step;
The target compression ratio set in the compression ratio setting step is compared with the actual compression ratio derived in the actual compression ratio derivation step. If the difference between the two is larger than a predetermined value, the variable compression ratio mechanism is abnormal. An abnormality determination step for determining
You may make it have.

  According to this, it is possible to determine the abnormality of the variable compression ratio mechanism more easily without using a special sensor or the like.

The abnormality determination method for the variable compression ratio mechanism includes a compression ratio setting step of setting a compression ratio to a predetermined target compression ratio by the variable compression ratio mechanism;
An air-fuel ratio switching step in which the air-fuel ratio switching means changes the air-fuel ratio of the exhaust;
A time difference detecting step of detecting a time difference between a change timing of the air-fuel ratio upstream of the exhaust purification catalyst when the air-fuel ratio is changed and a change timing of the air-fuel ratio downstream of the exhaust purification catalyst;
An actual compression ratio derivation step for deriving an actual compression ratio from the time difference detected in the time difference detection step;
An abnormality determination step of determining an abnormality of the variable compression ratio mechanism from the target compression ratio set in the compression ratio setting step and the actual compression ratio derived in the actual compression ratio derivation step;
A first actual compression ratio which is an actual compression ratio when the target compression ratio is a predetermined first target compression ratio, and an actual compression ratio when the target compression ratio is a predetermined second target compression ratio. A second actual compression ratio is derived,
In the abnormality determination step, when a difference between the difference between the first target compression ratio and the second target compression ratio and a difference between the first actual compression ratio and the second actual compression ratio are larger than a predetermined value, The variable compression ratio mechanism may be determined to be abnormal.

  According to this, the error factor of the absolute value at the time of deriving the actual compression ratio can be canceled, so that the abnormality of the variable compression ratio mechanism can be detected with higher accuracy.

  The means for solving the above-described problems of the present invention can be used in combination as much as possible.

  In the present invention, the abnormality of the variable compression ratio mechanism can be determined with a simpler configuration or process.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of a variable compression ratio internal combustion engine (hereinafter also simply referred to as “internal combustion engine”) 1 in which the compression ratio is variable. In the present embodiment, in order to display the internal combustion engine 1 simply, some components are not shown. An intake pipe 19 is connected to the combustion chamber in the cylinder 2 via an intake port 18 provided in the cylinder head 10. The intake of the intake air into the cylinder 2 is controlled by the intake valve 5. Opening and closing of the intake valve 5 is controlled by rotational driving of the intake side cam 7.

  An exhaust pipe 21 is connected to the combustion chamber in the cylinder 2 via an exhaust port 20 provided in the cylinder head 10. Exhaust discharge to the outside of the cylinder 2 is controlled by an exhaust valve 6. Opening and closing of the exhaust valve 6 is controlled by rotational driving of the exhaust side cam 8. Further, a fuel injection valve 17 is provided in the intake port 18, and a throttle valve 22 is provided in the intake pipe 19.

The exhaust pipe 21 is provided with a catalytic converter 25 having a three-way catalyst for purifying HC, NOx, CO, etc. in the exhaust gas flowing through the exhaust pipe 21. Further, an A / F sensor 27 for detecting the air-fuel ratio of the exhaust gas passing through the upstream side of the catalytic converter 25 is arranged as an upstream air-fuel ratio sensor on the upstream side of the catalytic converter 25 in the exhaust pipe 21. Further, an O ₂ sensor 29 for detecting the oxygen concentration of the exhaust gas passing through the downstream side of the catalytic converter 25 is arranged as a downstream air-fuel ratio sensor on the exhaust pipe 21 downstream of the catalytic converter 25. Further, a spark plug 16 is provided at the top of the cylinder 2. The piston 15 connected to the crankshaft 13 of the internal combustion engine 1 via the connecting rod 14 reciprocates in the cylinder 2.

Here, in the internal combustion engine 1, the mechanical compression ratio of the internal combustion engine 1 is changed by moving the cylinder block 3 relative to the crankcase 4 in the axial direction of the cylinder 2 by the variable compression ratio mechanism 9. That is, the variable compression ratio mechanism 9 is constituted by the cylinder block 3, the cylinder head 10 and the piston 15 by moving the cylinder head 10 together with the cylinder block 3 relative to the crankcase 4 in the axial direction of the cylinder 2. The volume of the combustion chamber is changed, and as a result, the mechanical compression ratio of the internal combustion engine 1 is variably controlled. For example, when the cylinder block 3 is relatively moved away from the crankcase 4, the combustion chamber volume increases and the mechanical compression ratio decreases.

  The variable compression ratio mechanism 9 includes the shaft portion 9a, a cam portion 9b having a circular cam profile fixed to the shaft portion 9a while being eccentric with respect to the central axis of the shaft portion 9a, and the cam portion 9b. A movable bearing portion 9c having an outer shape and rotatable relative to the shaft portion 9a and attached in an eccentric state like the cam portion 9b, a worm wheel 9d provided concentrically with the shaft portion 9a, and a worm wheel 9d And a worm drive motor 9f that rotationally drives the worm 9e. The cam portion 9 b is installed in a storage hole provided in the cylinder block 3, the movable bearing portion 9 c is installed in a storage hole provided in the crankcase 4, and the worm drive motor 9 f is connected to the cylinder block 3. And move integrally with the cylinder block 3. Here, the driving force from the worm drive motor 9f is transmitted to the shaft portion 9a via the worm 9e and the worm wheel 9d. Then, the cam block 9 b and the movable bearing portion 9 d in an eccentric state are driven, so that the cylinder block 3 is moved relative to the crankcase 4 in the axial direction of the cylinder 2.

  The internal combustion engine 1 is also provided with an electronic control unit (hereinafter referred to as “ECU”) 90 for controlling the internal combustion engine 1. The ECU 90 includes a CPU, a ROM, a RAM, and the like for storing various programs and maps to be described later, and controls the operating conditions of the internal combustion engine 1 according to the operating conditions of the internal combustion engine 1 and the driver's request. Unit. The ECU 90 corresponds to the compression ratio control means in this embodiment.

  Here, the accelerator opening sensor 92 is electrically connected to the ECU 90, and the ECU 90 receives a signal corresponding to the accelerator opening, and calculates an engine load required for the internal combustion engine 1 based on the signal. A crank position sensor 91 is electrically connected to the ECU 90. The ECU 90 receives a signal corresponding to the rotational angle of the output shaft of the internal combustion engine 1, and the engine rotational speed of the internal combustion engine 1, the engine rotational speed and the gears. The vehicle speed or the like of the vehicle on which the internal combustion engine 1 is mounted is calculated from the ratio or the like. Further, the throttle valve 22 in the intake pipe 19 and the spark plug 16 and the fuel injection valve 17 in the cylinder head 10 are also electrically connected to the ECU 90 and operate based on a command signal from the ECU 90.

  Further, a worm drive motor 9f constituting the variable compression ratio mechanism 9 is electrically connected to the ECU 90. Then, the worm drive motor 9 f is driven by a command from the ECU 90, and the mechanical compression ratio of the internal combustion engine 1 is changed by the variable compression ratio mechanism 9. The change in the mechanical compression ratio of the internal combustion engine 1 is performed based on the operating state of the internal combustion engine 1 during normal operation after the warm-up. For example, when the operating state of the internal combustion engine 1 is expressed by an engine load and an engine speed, the cylinder block 3 is connected to the crankcase 4 as the engine speed changes from a low engine load to a high engine load or from a low engine speed to a high engine speed. The worm drive motor 9f is driven in a direction away from the engine to shift the mechanical compression ratio of the internal combustion engine 1 from a high compression ratio to a low compression ratio.

  Here, if any abnormality occurs in the variable compression ratio mechanism 9 described above, for example, if the compression ratio becomes excessively low in an operating state with a low engine load or a low engine speed, combustion will not occur. There is a risk of misfire and worsening of emissions. On the other hand, knocking may occur when the compression ratio becomes excessively high when the engine is operating at a high engine load or high engine speed. Further, the internal combustion engine 1 may be damaged due to the collision between the piston 15 and the intake valve 5 or the exhaust valve 6.

Therefore, in the internal combustion engine 1, it is necessary to determine in a timely manner whether or not the variable compression ratio mechanism 9 is operating normally. As an abnormality determination method of the variable compression ratio mechanism 9, there is a method of detecting the combustion pressure at the time of combustion in each cylinder 2 and detecting whether the combustion pressure is a normal value. However, in order to measure the combustion pressure in a vehicle, it is necessary to provide a pressure sensor and an arithmetic device for processing the signal, which is not an optimal method in terms of cost and durability.

Therefore, in this embodiment, the air-fuel ratio of the exhaust gas passing through the exhaust pipe 21 is changed (reversed) from lean to rich by post injection, and the output signal of the A / F sensor 27 at that time and the O ₂ sensor 29 The temperature of the exhaust gas passing through the exhaust pipe 21 is detected from the time difference of the output signal change.

Next, referring to FIG. 2, the air-fuel ratio of the exhaust gas passing through the exhaust pipe 21 is changed (reversed) from lean to rich by post-injection, the output signal of the A / F sensor 27 at that time, and the O ₂ sensor 29 The principle of acquiring the temperature of the exhaust gas passing through the exhaust pipe 21 by detecting the time difference between the output signal changes will be described.

When the air-fuel ratio of the exhaust gas changes from lean to rich by post-injection (inversion), the output of the A / F sensor 27 arranged upstream of the catalytic converter 25 is the air-fuel ratio as shown in the upper graph of FIG. Changes immediately after switching. Thereafter, HC, CO, etc., which are unburned components of the fuel, reach the catalytic converter 25. At that time, when the temperature of the exhaust gas is low, the bed temperature of the catalyst is also low, and the speed at which O ₂ moves in the three-way catalyst provided in the catalytic converter 25 is slow. Therefore, immediately after the change (inversion) of the air-fuel ratio, the HC and CO in the exhaust gas that has reached the catalytic converter 25 cannot react with the O ₂ in the three-way catalyst. It is discharged directly downstream without being oxidized. Accordingly, since the output of the O ₂ sensor 29 changes relatively early, when the exhaust gas temperature is low, as shown in the middle graph of FIG. 2, the A / F sensor at the time of air-fuel ratio change (reversal). The time difference between the output change of 27 and the output change of the O ₂ sensor 29 is shortened.

On the other hand, when the temperature of the exhaust gas is high, the temperature of the catalyst is also high, and the speed at which O ₂ moves in the three-way catalyst provided in the catalytic converter 25 increases. Therefore, immediately after the change (inversion) of the air-fuel ratio, HC, CO, etc. in the exhaust and O ₂ in the three-way catalyst can react. Then, immediately after the change (inversion) of the air-fuel ratio, HC, CO, etc. that have reached the catalytic converter 25 react with the O ₂ in the three-way catalyst and are consumed, so that they are not discharged downstream of the catalytic converter 25. Then, after O ₂ in the three-way catalyst is consumed and the reaction of HC, CO and the like converges with O ₂ in the three-way catalyst, HC, CO and the like start to be discharged to the downstream side of the catalytic converter 25. As a result, a delay occurs in the time when the output of the O ₂ sensor 29 changes. Therefore, when the temperature of the exhaust gas is low, as shown in the lower graph of FIG. 2, the output change of the A / F sensor 27 and the output change of the O ₂ sensor 29 when the air-fuel ratio changes (inverts). The time difference becomes longer.

Therefore, it is possible to estimate the exhaust temperature from the time difference between the output change of the A / F sensor 27 and the output change of the O ₂ sensor 29 when the air-fuel ratio changes (reverses). FIG. 3 is a graph showing the relationship between the time difference between the output change of the A / F sensor 27 and the output change of the O ₂ sensor 29 at the time of air-fuel ratio change (reversal) and the exhaust gas temperature.

  On the other hand, there is also a high correlation between the compression ratio of the internal combustion engine 1 and the exhaust temperature. That is, when the compression ratio is high, the in-cylinder combustion efficiency is high, so that much of the energy of the fuel is used for engine output, so the exhaust temperature is relatively low. On the other hand, when the compression ratio is low, the combustion efficiency is low, so the portion of the fuel energy that is engine output is relatively small, and the energy that did not become the engine output is given to the exhaust, and the temperature of the exhaust To rise. FIG. 4 shows a graph of the relationship between the mechanical compression ratio and the exhaust temperature.

Therefore, by acquiring the time difference between the output change of the A / F sensor 27 and the output change of the O ₂ sensor 29 at the time of air-fuel ratio change (inversion), the actual compression ratio value at that time can be acquired. it can. When the acquired actual compression ratio value deviates significantly from the target compression ratio value, it is possible to determine that the variable compression ratio mechanism 9 is abnormal.

  FIG. 5 shows a variable compression ratio mechanism abnormality determination routine in the present embodiment. This routine is a program stored in the ROM of the ECU 90, and is a routine that is executed at predetermined intervals while the internal combustion engine 1 is operating.

When this routine is executed, first, in S101, it is determined whether or not the failure diagnosis of the A / F sensor 27 and the O ₂ sensor 29 has been completed and the operation is determined to be normal. The failure diagnosis of the A / F sensor 27 and the O ₂ sensor 29 is a process executed every predetermined period by another routine. For example, the failure diagnosis of the A / F sensor 27 includes a fuel in the internal combustion engine 1. A diagnosis is made by increasing or decreasing the injection amount and checking whether the output of the A / F sensor 27 follows the air-fuel ratio change at that time. Further, as the failure diagnosis of the O ₂ sensor 29, for example, when the fuel cut operation is started, the diagnosis is made based on whether or not the output of the O ₂ sensor 29 becomes lean within a predetermined period.

Here, the A / F sensor 27 and by the last failure diagnosis, the failure diagnosis flag in the A / F sensor 27 which operates the O ₂ sensor 29 are respectively ON when it is determined that the normal and failure of the O ₂ sensor 29 The determination may be made by reading each value of the diagnostic flag. If it is determined that the A / F sensor 27 and the O ₂ sensor 29 are operating normally, the process proceeds to S102. On the other hand, when it is determined that the operation of the A / F sensor 27 or the O ₂ sensor 29 is abnormal, the routine is temporarily ended as it is.

In S102, it is determined whether or not the failure diagnosis of the three-way catalyst provided in the catalytic converter 25 has been completed and the operation is determined to be normal. This failure diagnosis of the three-way catalyst is also a process executed at predetermined intervals by another routine. For example, the rich / lean of the air-fuel ratio of the exhaust gas is continuously reversed, and the output of the O ₂ sensor 29 at that time The determination may be made based on the fact that the waveform does not change significantly from the waveform when the catalyst is normal. Here, the determination may be made by reading the value of the catalyst failure diagnosis flag that is turned on when the three-way catalyst is determined to be normal by the latest catalyst failure diagnosis. If it is determined that the operation of the three-way catalyst is normal, the process proceeds to S103. On the other hand, if it is determined that the operation of the three-way catalyst is abnormal, this routine is once terminated.

  In S103, it is determined whether a precondition for abnormality determination of the variable compression ratio mechanism is satisfied. Here, the precondition for the abnormality determination of the variable compression ratio mechanism is a range in which there is no problem in operation performance even when the operation state of the internal combustion engine 1 is set to an abnormality determination compression ratio described later. Belongs to. Further, the cooling water temperature or the oil temperature is sufficiently high, and the warm-up of the internal combustion engine 1 has been completed. If a positive determination is made in S103, the process proceeds to S104. On the other hand, if a negative determination is made, this routine is temporarily terminated.

  In S104, a compression ratio change command is output to the variable compression ratio mechanism 9 (worm drive motor 9f). Here, the compression ratio is changed to an abnormality determination compression ratio predetermined for abnormality determination. Further, post-injection is executed in the internal combustion engine 1, and the air-fuel ratio of the exhaust gas is changed (reversed) from lean to rich. Here, the fuel injection valve 17 and the ECU 90 that perform post-injection correspond to air-fuel ratio switching means. The abnormality determination compression ratio corresponds to the target compression ratio. The process of S104 corresponds to a compression ratio setting process and an air-fuel ratio switching process. When the process of S104 ends, the process proceeds to S105.

In S105, first, the time difference between the output change of the A / F sensor 27 and the output change of the O ₂ sensor 29 is acquired, and the exhaust temperature is derived from this time difference. Specifically, it is derived by reading the value of the exhaust gas temperature corresponding to the detected time difference from the time difference-temperature map in which the contents of the graph shown in FIG. 3 are mapped. Further, from the temperature-compression ratio map obtained by mapping the contents of the graph showing the relationship between the exhaust temperature and the compression ratio shown in FIG. 4, the compression ratio value corresponding to the obtained exhaust temperature is obtained. By reading, the actual compression ratio value is finally obtained. Here, the ECU 90 that obtains the time difference between the output change of the A / F sensor 27 and the output change of the O ₂ sensor 29 and derives the exhaust gas temperature from this time difference constitutes a temperature acquisition means. The processing of S105 corresponds to a time difference detection step and an actual compression ratio derivation step. When the process of S105 ends, the process proceeds to S106.

  In S106, it is determined whether or not the difference between the actual compression ratio value obtained in S105 and the abnormality determination compression ratio according to the command from the ECU 90 is equal to or less than an allowable value. Here, the allowable value is a threshold value that determines that the variable compression ratio mechanism 9 is not abnormal when the difference between the actual compression ratio and the abnormality determination compression ratio is equal to or smaller than this value. Is required. This allowable value corresponds to a predetermined value in this embodiment. If a positive determination is made here, the process proceeds to S107. On the other hand, if a negative determination is made, the process proceeds to S108.

  In S107, it is determined that the variable compression ratio mechanism 9 is normal. In S108, the variable compression ratio mechanism 9 is determined to be abnormal. When the process of S107 or S108 ends, this routine is temporarily ended. In the present embodiment, the ECU 90 that executes the processes of S106 to S108 corresponds to an abnormality determination unit. Moreover, the process of S106-S108 is corresponded to an abnormality determination process.

As described above, in this embodiment, the time difference between the output change of the A / F sensor 27 and the output change of the O ₂ sensor 29 is acquired, and the exhaust gas temperature is derived from this time difference. Also, the value of the actual compression ratio is obtained from the derived exhaust temperature, and if the difference between the abnormality determination compression ratio and the actual compression ratio is greater than the allowable value, the variable compression ratio mechanism is determined to be abnormal. It was.

  According to this, an actual compression ratio can be acquired using an existing member without providing a new sensor or the like, and abnormality determination of the variable compression ratio mechanism can be performed with a simple configuration and processing.

Next, a second embodiment of the present invention will be described. In the present embodiment, the processing for obtaining the actual compression ratio value from the time difference between the output change of the A / F sensor 27 and the output change of the O ₂ sensor 29 is executed at two different abnormality determination compression ratios. An example will be described in which an abnormality of the variable compression ratio mechanism is determined based on the difference between the difference between the two abnormality determination compression ratios and the difference between the actual compression ratios acquired for each.

  FIG. 6 shows a flowchart of the variable compression ratio mechanism abnormality determination routine 2 in the present embodiment. The difference between this routine and the variable compression ratio mechanism abnormality determination routine described in the first embodiment is that in this routine, the processing of S201 to S205 is executed instead of the processing of S104 to S106. Hereinafter, only differences between this routine and the variable compression ratio mechanism abnormality determination routine will be described.

  When the process of S103 is completed in this routine, the process proceeds to S201. In S201, a compression ratio change command is output to the variable compression ratio mechanism 9 (worm drive motor 9f). Here, it is changed to the first abnormality determination compression ratio predetermined for abnormality determination. Further, post-injection is executed in the internal combustion engine 1, and the air-fuel ratio is changed (reversed) from lean to rich. Here, the first abnormality determination compression ratio corresponds to the first target compression ratio. When the process of S201 ends, the process proceeds to S202.

In S202, first, the time difference between the output change of the A / F sensor 27 and the output change of the O ₂ sensor 29 is acquired, and the time difference obtained by mapping the contents of the graph shown in FIG. The temperature of the exhaust is derived from the temperature map. Further, the actual first compression ratio value is obtained from the temperature-compression ratio map obtained by mapping the contents of the graph showing the relationship between the exhaust gas temperature and the compression ratio shown in FIG. This actual first compression ratio corresponds to the first actual compression ratio in this embodiment. When the process of S202 ends, the process proceeds to S203.

  In S203, a compression ratio change command is output to the variable compression ratio mechanism 9 (worm drive motor 9f). Here, the second abnormality determination compression ratio is determined separately from the first abnormality determination compression ratio for abnormality determination. Further, post-injection is executed in the internal combustion engine 1, and the air-fuel ratio is changed (reversed) from lean to rich. Here, the second abnormality determination compression ratio corresponds to the second target compression ratio. When the process of S203 ends, the process proceeds to S204.

In S204, first, the time difference between the output change of the A / F sensor 27 and the output change of the O ₂ sensor 29 is acquired, and the time difference obtained by mapping the contents of the graph shown in FIG. From the temperature map, the exhaust temperature is derived. Further, from the temperature-compression ratio map obtained by mapping the contents of the graph showing the relationship between the exhaust gas temperature and the compression ratio shown in FIG.
The actual value of the second compression ratio is obtained. Here, the actual second compression ratio corresponds to the second actual compression ratio in the present embodiment. When the process of S204 ends, the process proceeds to S205.

  In S205, the difference between the actual first compression ratio value obtained in S202 and the actual second compression ratio obtained in S204, and the first target compression ratio and the second target compression ratio based on a command from the ECU 90. It is determined whether or not the difference from the difference is less than the allowable value. Here, the allowable value corresponds to a predetermined value in this embodiment. If a positive determination is made here, the process proceeds to S107. On the other hand, if a negative determination is made, the process proceeds to S108.

  In the variable compression ratio mechanism abnormality determination routine 2 described above, the actual first compression ratio and the actual second compression ratio are derived in S202 and S204, respectively, but either one is derived in the past. For example, a value derived in the previous trip (ignition ON to ignition OFF) may be used. Then, the abnormality determination process of the variable compression ratio mechanism can be further simplified.

As described above, in this embodiment, the actual compression ratio is obtained for each of two different abnormality determination compression ratios from the time difference between the output change of the A / F sensor 27 and the output change of the O ₂ sensor 29. It was. If the difference between the difference between the two abnormality determination compression ratios and the difference between the two actual compression ratios derived for each is equal to or less than the allowable value, it is determined that the variable compression ratio mechanism 9 is normal.

  According to this, since the abnormality determination is performed by comparing the change of the abnormality determination compression ratio with the change of the actual compression ratio, the error factor of the absolute value of the measured value in the process of deriving the actual compression ratio is canceled. Therefore, the abnormality determination of the variable compression ratio mechanism 9 can be performed more accurately.

In any of the above-described embodiments, the time acquisition between obtaining the time difference between the output change of the A / F sensor 27 and the output change of the O ₂ sensor 29 and deriving the exhaust gas temperature from this time difference is obtained. An example of the means has been described. However, the temperature acquisition means in the present invention is not limited to this. For example, a temperature sensor may be provided in the exhaust pipe 21 or the catalytic converter 25.

Further, the variable compression ratio mechanism in the present invention is not limited to that shown in FIG. 1, for example, the connecting rod is divided into two and the connecting rod connected to the crankshaft is centered on a predetermined swing center. A swingable swing member is connected, and the swing center moves by rotating the camshaft, thereby changing the volume of the combustion chamber and the stroke of the piston, thereby changing the compression ratio of the internal combustion engine. It is also possible to apply the present invention to mechanisms and other variable compression ratio mechanisms.

Further, the exhaust purification catalyst in the present invention is not limited to a three-way catalyst. The present invention can be applied to other types of catalysts such as NOx storage reduction catalysts. Furthermore, the combination of the upstream air-fuel ratio sensor and the downstream air-fuel ratio sensor may be a combination other than the combination in which the A / F sensor is disposed on the upstream side and O ₂ is disposed on the downstream side. For example, A / F sensors may be provided on both the upstream side and the downstream side.

Further, in the process of S105 of the above embodiment, for example, first, a time difference between the output change of the A / F sensor 27 and the output change of the O ₂ sensor 29 is acquired, and the time difference is shown in FIG. The temperature of the exhaust was derived using a time difference-temperature map that maps the contents of the graph. Then, using the temperature-compression ratio map obtained by mapping the contents of the graph showing the relationship between the exhaust temperature and the compression ratio shown in FIG. Was derived. However, for example, by using a map that combines the time difference-temperature map and the temperature-compression ratio map, the time difference between the output change of the A / F sensor 27 and the output change of the O ₂ sensor 29 is actually calculated. The compression ratio value may be derived directly.

Next, Embodiment 3 of the present invention will be described. In this embodiment, as in the control by the variable compression ratio mechanism abnormality determination routine described in the first embodiment, the final difference is determined from the time difference between the output change of the A / F sensor 27 and the output change of the O ₂ sensor 29. Thus, the actual compression ratio value is derived, and abnormality determination of the variable compression ratio mechanism is not performed based on whether or not the difference between the actual compression ratio and the abnormality determination compression ratio is equal to or less than the allowable value. An example in which abnormality determination is performed based on whether or not the time difference between the output change and the output change of the O ₂ sensor 29 is equal to or less than the allowable time difference will be described.

  FIG. 7 shows a flowchart of the variable compression ratio mechanism abnormality determination routine 3 in the present embodiment. The difference between this routine and the variable compression ratio mechanism abnormality determination routine is that the processing of S301 and S302 is performed instead of the processing of S105 and S106. Only the differences between this routine and the variable compression ratio mechanism abnormality determination routine will be described below.

In S301, the time difference between the output change of the A / F sensor 27 and the output change of the O ₂ sensor 29 is acquired. This is a process equivalent to a part of the process of S105. When the process of S301 ends, the process proceeds to S302.

In S302, it is determined whether or not the time difference between the output change of the A / F sensor 27 acquired in S301 and the output change of the O ₂ sensor 29 is equal to or less than an allowable time difference. Here, the allowable time difference is the time difference-temperature map obtained by mapping the content of the graph shown in FIG. 3 with the allowable value (compression ratio difference) in S106 of the variable compression ratio mechanism abnormality determination routine, and shown in FIG. This is obtained by converting the content of the graph showing the relationship between the exhaust gas temperature and the compression ratio using a temperature-compression ratio map obtained by mapping, and obtaining the difference in the allowable output change timing. The time difference of the output change corresponding to the abnormality determination compression ratio used when obtaining the allowable time difference is an index value related to the target compression ratio in this embodiment.

According to this, by comparing the time difference between the output change of the A / F sensor 27 and the output change of the O ₂ sensor 29 with the allowable time difference, the abnormality determination of the variable compression ratio mechanism can be performed. The determination process can be further simplified.

Next, a fourth embodiment of the present invention will be described. In this embodiment, the control by the variable compression ratio mechanism abnormality determination routine 2 described in the second embodiment is simplified. That is, in the second embodiment, the process for obtaining the actual compression ratio value from the time difference between the output change of the A / F sensor 27 and the output change of the O ₂ sensor 29 is executed at two different abnormality determination compression ratios. The abnormality of the variable compression ratio mechanism was determined based on whether the difference between the difference between the two abnormality determination compression ratios and the difference between the actual compression ratios acquired for each was equal to or less than an allowable value. In contrast, in this embodiment, the time difference between the output change of the A / F sensor 27 and the output change of the O ₂ sensor 29 is acquired at two different abnormality determination compression ratios, and acquired at two abnormality determination compression ratios. The abnormality determination of the variable compression ratio mechanism is performed based on whether or not the difference of the time difference thus made is equal to or less than the allowable difference.

  FIG. 8 shows a flowchart of the variable compression ratio mechanism abnormality determination routine 4 in the present embodiment. The difference between this routine and the variable compression ratio mechanism abnormality determination routine 2 is that the processes of S401, S402, and S403 are performed instead of the processes of S202, S204, and S205. Hereinafter, only differences between this routine and the variable compression ratio mechanism abnormality determination routine 2 will be described.

In S401, a time difference (first time difference) between the output change of the A / F sensor 27 and the output change of the O ₂ sensor 29 is acquired. This is a process equivalent to a part of the process of S202.

Similarly, in S402, a time difference (second time difference) between the output change of the A / F sensor 27 and the output change of the O ₂ sensor 29 is acquired. This is also a process equivalent to a part of the process of S204.

In S403, it is determined whether or not the difference between the first time difference acquired in S401 and the second time difference acquired in S402 is equal to or smaller than an allowable difference. Here, the allowable difference is the time difference-temperature map obtained by mapping the allowable value (difference in compression ratio difference) in S205 of the variable compression ratio mechanism abnormality determination routine 2 with the contents of the graph shown in FIG. The graph shows the relationship between the exhaust temperature and the compression ratio, and is converted using a temperature-compression ratio map that maps the contents of the graph, and the difference in the time difference between the allowable output changes is obtained. The time difference of the output change corresponding to the first abnormality determination compression ratio and the second abnormality determination compression ratio used when obtaining the allowable difference is an index value regarding the target compression ratio in the present embodiment.

According to this, between the output change of the A / F sensor 27 and the output change of the O ₂ sensor 29 acquired at two different compression ratios of the first abnormality determination compression ratio and the second abnormality determination compression ratio. By comparing the difference between the time differences (the first time difference and the second time difference) with an allowable difference as a threshold, it is possible to perform abnormality determination of the variable compression ratio mechanism, and to further simplify the abnormality determination process. .

  In the variable compression ratio mechanism abnormality determination routine 4 described above, the first time difference and the second time difference are acquired in S401 and S402, respectively, but one of the values is acquired in the past, for example, the previous time difference. You may make it use the value acquired in the trip (ignition ON-ignition OFF). Then, the abnormality determination process of the variable compression ratio mechanism can be further simplified.

It is sectional drawing which shows schematic structure of the internal combustion engine which concerns on the Example of this invention. In an embodiment of the present invention, when changing the air-fuel ratio is a graph showing the change of the A / F sensor and the O ₂ sensor output signal. In the embodiment of the present invention, it is a graph showing the relationship between the temperature of the exhaust gas and the difference between the change timing of the A / F sensor and the O ₂ sensor output signal. It is a graph which shows the relationship between the mechanical compression ratio and the temperature of exhaust_gas | exhaustion in the Example of this invention. It is a flowchart which shows the variable compression ratio mechanism abnormality determination routine which concerns on Example 1 of this invention. It is a flowchart which shows the variable compression ratio mechanism abnormality determination routine 2 which concerns on Example 2 of this invention. It is a flowchart which shows the variable compression ratio mechanism abnormality determination routine 3 which concerns on Example 3 of this invention. It is a flowchart which shows the variable compression ratio mechanism abnormality determination routine 4 which concerns on Example 4 of this invention.

Explanation of symbols

1. Variable compression ratio internal combustion engine (internal combustion engine)
2 ... Cylinder 3 ... Cylinder block 4 ... Crankcase 5 ... Intake valve 6 ... Exhaust valve 7 ... Intake side cam 8 ... Exhaust side cam 9 ... Variable compression ratio mechanism 13 ... Crankshaft 15 ... Piston 16 ... Ignition valve 17 ... Fuel injection valve 18 ... Intake port 19 ... Intake air tube 20 .... exhaust port 21 ... exhaust pipe 22 ... throttle valve 25 ... catalytic converter 27 .... A / F sensor 29 .... _{O 2} sensor 90..・ ECU
91 ... Crank position sensor 92 ... Accelerator position sensor

Claims (8)

A variable compression ratio mechanism capable of changing the compression ratio of the internal combustion engine;
Compression ratio control means for setting the compression ratio to a target compression ratio by the variable compression ratio mechanism;
Temperature acquisition means for acquiring the temperature of the exhaust from the internal combustion engine;
The target compression ratio set by the compression ratio control means or an index value related to the target compression ratio, and the exhaust temperature acquired by the temperature acquisition means in a state where the compression ratio is set to the target compression ratio, An abnormality determining means for determining an abnormality of the variable compression ratio mechanism;
Air-fuel ratio switching means for changing the air-fuel ratio of the exhaust from the internal combustion engine;
An exhaust purification catalyst that is provided in an exhaust passage through which exhaust from the internal combustion engine flows, and purifies exhaust that passes through the exhaust passage;
An upstream air-fuel ratio sensor that detects an upstream air-fuel ratio that is an air-fuel ratio of the exhaust gas upstream of the exhaust purification catalyst in the exhaust passage;
A downstream air-fuel ratio sensor that detects a downstream air-fuel ratio that is an air-fuel ratio of the exhaust gas on the downstream side of the exhaust purification catalyst in the exhaust passage,
The temperature acquisition means includes
The temperature of the exhaust gas is acquired by the difference between the change timing of the upstream air-fuel ratio and the change timing of the downstream air-fuel ratio when the air-fuel ratio switching means changes the air-fuel ratio of the exhaust gas. A variable compression ratio internal combustion engine. The abnormality determination means derives an actual compression ratio from the temperature of the exhaust gas acquired by the temperature acquisition means in a state where the compression ratio is set to the target compression ratio, and calculates the target compression ratio and the actual compression ratio. 2. The variable compression ratio internal combustion engine according to claim 1 , wherein the variable compression ratio mechanism is determined to be abnormal when the difference is greater than a predetermined value. The abnormality determination means derives a first actual compression ratio that is an actual compression ratio from the temperature of the exhaust gas acquired by the temperature acquisition means in a state where the compression ratio is set to a predetermined first target compression ratio, and compression A second actual compression ratio that is an actual compression ratio is derived from the temperature of the exhaust gas acquired by the temperature acquisition means in a state where the ratio is set to a predetermined second target compression ratio, and the first target compression ratio and the The variable compression ratio mechanism is determined to be abnormal when a difference between a second target compression ratio and a difference between the first actual compression ratio and the second actual compression ratio is greater than a predetermined value. The variable compression ratio internal combustion engine according to claim 1 . 2. The variable compression ratio internal combustion engine according to claim 1 , wherein the operation of the exhaust purification catalyst is confirmed before the abnormality determination unit performs abnormality determination of the variable compression ratio mechanism. 2. The variable according to claim 1, wherein the abnormality determination unit confirms the operation of the upstream air-fuel ratio sensor and / or the downstream air-fuel ratio sensor before making an abnormality determination of the variable compression ratio mechanism. Compression ratio internal combustion engine. A variable compression ratio mechanism capable of changing the compression ratio of the internal combustion engine;
Compression ratio control means for setting the compression ratio to a target compression ratio by the variable compression ratio mechanism;
Air-fuel ratio switching means for changing the air-fuel ratio of the exhaust from the internal combustion engine;
An exhaust purification catalyst that is provided in an exhaust passage through which exhaust from the internal combustion engine flows, and purifies the exhaust;
An abnormality determination method for a variable compression ratio mechanism in a variable compression ratio internal combustion engine comprising:
When the air-fuel ratio switching means changes the air-fuel ratio of the exhaust gas, the timing of change of the air-fuel ratio upstream of the exhaust purification catalyst and the timing of change of the air-fuel ratio downstream of the exhaust purification catalyst Time difference,
An abnormality determination method for a variable compression ratio mechanism, wherein abnormality determination for the variable compression ratio mechanism is performed based on the target compression ratio. A compression ratio setting step of setting a compression ratio to a target compression ratio by the variable compression ratio mechanism;
An air-fuel ratio switching step in which the air-fuel ratio switching means changes the air-fuel ratio of the exhaust;
A time difference detecting step of detecting a time difference between a change timing of the air-fuel ratio upstream of the exhaust purification catalyst when the air-fuel ratio is changed and a change timing of the air-fuel ratio downstream of the exhaust purification catalyst;
An actual compression ratio derivation step for deriving an actual compression ratio from the time difference detected in the time difference detection step;
The target compression ratio set in the compression ratio setting step is compared with the actual compression ratio derived in the actual compression ratio derivation step. If the difference between the two is larger than a predetermined value, the variable compression ratio mechanism is abnormal. An abnormality determination step for determining
The abnormality determination method for a variable compression ratio mechanism according to claim 6 , wherein: A compression ratio setting step of setting the compression ratio to a predetermined target compression ratio by the variable compression ratio mechanism;
An air-fuel ratio switching step in which the air-fuel ratio switching means changes the air-fuel ratio of the exhaust;
A time difference detecting step of detecting a time difference between a change timing of the air-fuel ratio upstream of the exhaust purification catalyst when the air-fuel ratio is changed and a change timing of the air-fuel ratio downstream of the exhaust purification catalyst;
An actual compression ratio derivation step for deriving an actual compression ratio from the time difference detected in the time difference detection step;
An abnormality determination step of determining an abnormality of the variable compression ratio mechanism from the target compression ratio set in the compression ratio setting step and the actual compression ratio derived in the actual compression ratio derivation step;
A first actual compression ratio which is an actual compression ratio when the target compression ratio is a predetermined first target compression ratio, and an actual compression ratio when the target compression ratio is a predetermined second target compression ratio. A second actual compression ratio is derived,
In the abnormality determination step, when a difference between the difference between the first target compression ratio and the second target compression ratio and a difference between the first actual compression ratio and the second actual compression ratio are larger than a predetermined value, The abnormality determination method for a variable compression ratio mechanism according to claim 6 , wherein the variable compression ratio mechanism is determined to be abnormal.

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