JP2013053609A - Variable valve gear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the startability and the idle stability of an engine even under a condition where the advance angle operation of a cam is suppressed.SOLUTION: The variable valve gear controls the phase difference of a plurality of intake valves for introducing air into a cylinder. The variable valve gear includes a cam shaft having an adjustable cam for delaying at least one intake valve among the plurality of the intake valves to bring the at least one intake valve into a delayed closed state. The variable valve gear further includes: an air circulation limiting device for limiting entering or leaving of the air with respect to a cylinder from the intake valve opened and closed through the variable cam; a determination part for determining whether the variable cam can angle-advance from the angle-delayed state or not; and a control part for suppressing the blow back of the air from the cylinder by causing the air circulation limiting device to operate when it is determined by the determination part that the variable cam can not angle-advance from the angle-delayed state.

Description

  The present invention relates to a variable valve gear.

  Conventionally, a plurality of intake valves are provided per cylinder, and the phases of the intake valves may be varied depending on the load state of the engine. For example, the intake air amount is adjusted by fixing the phase of one intake valve and opening and closing the intake valve by retarding the phase of the other intake valve. When starting an engine equipped with a mechanism that varies the phase of the intake valve, it is possible to reduce the phase difference of the intake valve to secure the intake air amount, improve the startability, and further ensure the idle stability. . For example, the engine control device disclosed in Patent Document 1 advances the variable phase cam that can be controlled to the slow closing side by the balance between the hydraulic pressure and the elastic force of the spring when the engine is started. As a result, the phase difference between the two intake valves is reduced, and the intake air amount at the time of starting the engine is secured.

JP-A-8-303265

  However, it is assumed that the engine control device disclosed in Patent Document 1 cannot immediately advance the cam that can be controlled to the late closing side that determines the intake closing timing. For example, it is assumed that the cam cannot be advanced immediately when the supply amount of lubricating oil is insufficient or when the temperature is extremely low. Further, even when the mechanism (VVT) for changing the cam phase fails, the cam cannot be immediately advanced. If the cam cannot be advanced immediately at the start of the engine, it is assumed that it is difficult to improve engine startability and idle stability.

  Therefore, the variable valve operating apparatus disclosed in the present specification has an object to improve engine startability and idle stability even in a situation where the advance operation of the cam is suppressed.

  In order to solve the above-described problem, a variable valve apparatus disclosed in the present specification is a variable valve apparatus that controls a phase difference between a plurality of intake valves that introduce air into a cylinder. A camshaft having a variable cam capable of retarding and closing at least one intake valve, and air flowing into and out of the cylinder from the intake valve opened and closed via the variable cam An air flow restriction device for limiting, a determination unit for determining whether or not the variable cam can be advanced from the retarded state, and the determination unit that the variable cam is advanced from the retarded state And a control unit that operates the air flow restriction device to suppress the blow back of air from the cylinder when it is determined that the air flow cannot be performed.

  By operating the air flow restricting device, air blow-back from the cylinder is suppressed even in a situation where the advance operation of the cam is suppressed. As a result, the amount of air remaining in the cylinder can be maintained, and the engine startability and idle stability can be improved.

  According to the variable valve operating apparatus disclosed in the present specification, it is possible to improve engine startability and idle stability even in a situation where the cam advance operation is suppressed.

FIG. 1 is an explanatory diagram illustrating a schematic configuration of a variable valve operating apparatus according to a first embodiment. FIG. 2 is a schematic diagram showing an example of the arrangement of intake ports and exhaust ports for one cylinder of the engine. FIG. 3A is a schematic diagram showing a state in which the second roller arm and the extending member are coupled by a coupling pin. FIG. 3B is a schematic view showing an idle driving state of the second roller arm in which the coupling pin is pulled out from the second roller arm. FIG. 4A is an explanatory view showing an open / close state of the intake valve of the comparative example. FIG. 4B is an explanatory diagram illustrating an open / close state of the intake valve according to the first embodiment. FIG. 5A is a graph showing the phase of the comparative example. FIG. 5B is a graph showing the phase of the first embodiment. FIG. 5C is a graph showing changes in the in-cylinder air amount of the comparative example and the first embodiment. FIG. 5D is a graph showing changes in the in-cylinder temperature of the comparative example and the example 1. FIG. 6 is a graph showing the amount of compressed end air in the comparative example and Example 1. FIG. 7 is a graph showing the compression end temperatures of the comparative example and Example 1. FIG. 8 is a flowchart illustrating an example of control of the variable valve operating apparatus according to the first embodiment. FIG. 9 is an explanatory diagram showing a schematic configuration of the variable valve operating apparatus according to the second embodiment. FIG. 10A is a schematic diagram showing the arrangement of shut-off valves in the second embodiment. FIG. 10B is a cross-sectional view taken along line AA in FIG.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. However, in the drawings, the dimensions, ratios, and the like of each part may not be shown so as to completely match the actual ones.

  First, a schematic configuration of the variable valve operating apparatus 1 according to the first embodiment will be described with reference to FIG. The variable valve operating apparatus 1 controls the phase difference between a plurality of intake valves that introduce air into the cylinder. The variable valve operating apparatus 1 of the first embodiment shown in FIG. 1 controls the phase difference between the first intake valve 2 and the second intake valve 3. The first intake valve 2 and the second intake valve 3 introduce air into one cylinder. FIG. 2 is a schematic diagram showing an example of the arrangement of intake ports and exhaust ports for one cylinder of the engine. The engine includes a first intake port 31 and a second intake port 32 for each cylinder. The engine also includes a first exhaust port 33 and a second exhaust port 34 for each cylinder. The first intake valve 2 is arranged corresponding to the first intake port 31. The second intake valve 3 is arranged corresponding to the second intake port 32. The first intake port 31 is on the early closing side, and the second intake port 32 is on the late closing side. Thereby, an ultra-high expansion ratio cycle can be realized.

  The variable valve operating apparatus 1 disclosed in this specification can be applied to other types of engines having a plurality of intake valves for each cylinder. FIG. 1 shows only one cylinder.

  The variable valve operating apparatus 1 includes a camshaft 4. The camshaft 4 includes an outer shaft 4a and an inner shaft 4b. The outer shaft 4a includes a first cam 4a1. The first cam 4a1 is integrally provided on the outer peripheral portion of the outer shaft 4a. The inner shaft 4b includes a second cam 4b1. The second cam 4b1 is exposed to the outside of the outer shaft 4a through a groove provided in the outer shaft 4a.

  A VVC (Variable Valve Timing) 5 having an OCV (Oil control valve) 6 is connected to the end of the inner shaft 4b. When the VVC 5 operates, the inner shaft 4b rotates relative to the outer shaft 4a, and a phase difference is provided between the first cam 4a1 and the second cam 4b1. In other words, the second cam 4b1 corresponds to a variable cam and can be advanced and retarded by the VVC 5. The second cam 4b1 can retard the second intake valve 3 to be in a late closed state. Thus, the variable valve apparatus 1 can provide a phase difference between the first cam 4a1 and the second cam 4b1.

  The first cam 4 a 1 opens and closes the first intake valve 2 via the first roller arm 7. On the other hand, the second cam 4 b 1 opens and closes the second intake valve 3 via the second roller arm 8 and the extending member 9. As shown in FIG. 3A, the extending member 9 is coupled to the second roller arm 8 by inserting the coupling pin 10 into the coupling groove 8 a provided in the second roller arm 8. The coupling pin 9 is driven in and out by the actuator 11. The second roller arm 8, the extending member 9, the coupling pin 10 and the actuator 11 form an air flow restriction device. That is, as shown in FIG. 3B, when the coupling between the coupling pin 10 driven by the actuator 11 and the second roller arm is released, the second roller arm 8 is in an idle state. As a result, the second intake valve 3 cannot be opened, so that the flow of air from the second intake valve 3 into the cylinder is restricted.

  The variable valve operating apparatus 1 includes an ECU (Electronic control unit) 20. The ECU 20 includes a microcomputer including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an input / output circuit, and the like. It is configured. The ECU 20 is electrically connected to a cam angle sensor 21, a crank angle sensor 22, an electronic throttle 23, a vehicle speed sensor 24, an accelerator opening sensor 25, an oil temperature sensor 26, a water temperature sensor 27, and other sensors.

  The ECU 20 functions as a determination unit that determines whether or not the second cam 4b1 that is a variable cam can advance from the retarded state. Further, when the ECU 20 determines that the second cam 4b1 cannot advance from the retarded state, the ECU 20 drives the actuator 11 to stop the opening operation of the second intake valve 3, and the air from inside the cylinder It also functions as a control unit that suppresses the blow-back.

  Here, the opening / closing state of the intake valve by the variable valve operating apparatus 10 will be described in comparison with the opening / closing state of the intake valve of the comparative example. FIG. 4A is an explanatory view showing an open / close state of the intake valve of the comparative example. FIG. 4B is an explanatory diagram illustrating an open / close state of the intake valve according to the first embodiment. In the comparative example, no phase difference is provided between the first intake valve 2 and the second intake valve 3. The phase of the comparative example is shown in FIG. As shown in FIGS. 4A and 5A, the valve opening period of the first intake valve and the valve opening period of the second intake valve coincide with each other. The most retarded angle closing time in the comparative example is time T1. In the comparative example, a period from TDC (top dead center) to BDC (bottom dead center) indicated by an arrow X1 is a period during which air is sucked into the cylinder. The period from when the BDC indicated by the arrow X2 is exceeded to the end of the valve opening period is a period during which air is blown back from the cylinder through the intake port. When the first intake valve and the second intake valve are closed, the air in the cylinder is compressed as indicated by an arrow X3.

  Next, a case where the variable valve operating apparatus 1 according to the first embodiment is provided will be described. First, a state where the second roller arm 8 and the extending member 9 are coupled will be described. When the second roller arm 8 and the extending member 9 are coupled, the second intake valve 3 opens and closes behind the first intake valve 2 as shown in FIGS. 4 (B) and 5 (B). To do. In this case, the most retarded angle closing time is time T2. The period during which air is sucked into the cylinder is the period from TDC (top dead center) to BDC (bottom dead center) indicated by arrow X4, as in the comparative example. However, the period during which the cylinder and the intake port communicate with each other is longer than that in the comparative example. For this reason, as shown by the arrow X5, the period in which the blowback is observed is from the time when the BDC is exceeded to the end of the valve opening period of the second intake valve 3. Thereafter, the engine proceeds to the compression stroke.

  On the other hand, the case where the connection between the second roller arm 8 and the extending member 9 is released and the second roller arm 8 is in an idle state will be described. In this case, the second intake valve 3 remains closed. For this reason, the closing timing of the first intake valve 2 is the most retarded closing timing. This time is time T1, which is almost the same as in the comparative example. As a result, as shown by the arrow X7, the blowback period is the same as in the comparative example.

  Blow-back means that the air in the cylinder is discharged out of the cylinder through the intake port as the piston rises. The amount of blowback greatly depends on the second intake valve 3 that determines the closing timing. When the flow of air in the cylinder through the second intake port 32 that opens and closes the second intake valve 3 is restricted, the blowback amount is reduced. As a result, the amount of air in the cylinder is maintained and the actual compression ratio is increased. And the in-cylinder temperature becomes high and combustion is stabilized.

  As described above, by releasing the coupling between the second roller arm 8 and the extending member 9, that is, by setting the second intake valve 3 to the valve stop state, the blowback from the cylinder can be suppressed. As a result, as shown in FIG. 5C, the in-cylinder air amount can be maintained as compared to the case where the valve is not stopped and the coupling between the second roller arm 8 and the extending member 9 is maintained. . The amount of air that is maintained is equivalent to that in the comparative example in which there is no phase difference between the first intake valve and the second intake valve. Further, the in-cylinder temperature when the valve is stopped is also maintained at a high temperature equivalent to that of the comparative example as compared with the case where the valve is not stopped.

  FIG. 6 is a graph showing the compression end air amount of the comparative example and the example 1 at a certain engine speed. In FIG. 6, A shows the result of the comparative example, and B shows the result of “no valve stop” in which the second roller arm 8 and the extending member 9 are coupled in the example. C shows the result of “with valve stop” in which the connection between the second roller arm 8 and the extending member 9 is released in the embodiment. Compared with A, the compressed end air amount of B is greatly reduced. On the other hand, C is able to ensure a compression end air amount substantially the same as A.

  FIG. 7 is a graph showing the compression end temperatures of the comparative example and Example 1 at a certain engine speed. In FIG. 7, A indicates the result of the comparative example, and B indicates the result of “no valve stop” in which the second roller arm 8 and the extending member 9 are coupled in the example. C shows the result of “with valve stop” in which the connection between the second roller arm 8 and the extending member 9 is released in the embodiment. The compression end temperature of B is significantly lower than that of A. On the other hand, C can ensure the compression end temperature almost the same as A.

  As described above, since the compressed end air amount and the compressed end temperature can be maintained, the cam advance angle operation is suppressed, and even under circumstances where it is difficult to advance the engine, The startability and idle stability of the can be improved.

  Next, an example of the control of the variable valve operating apparatus 1 that operates as described above will be described with reference to the flowchart shown in FIG.

  First, in step S1, it is determined whether or not the VVT failure flag is ON. If the VVT 5 fails, the second cam 4b1 in the retarded state cannot be advanced. If the second cam 4b1 cannot be advanced, it is difficult to suppress blowback. Therefore, the second roller arm 8 is idled to suppress air blowback from the cylinder. Whether or not the VVT 5 is out of order is determined by comparing information obtained from the cam angle sensor 21 and the crank angle sensor 22 with the contents of the VVT drive command issued by the ECU 20 itself. That is, it is determined whether or not the cam angle relative to the crank angle is in accordance with the drive command issued by the realization ECU 20 itself. Note that at the timing of step S1, it is only necessary to determine whether or not the VVT failure flag is ON, and it is not necessary to determine the failure of the VVT 5 at this timing. Further, the VVT failure flag is turned ON not only when the advance angle and retard angle by VVT 5 are not completely performed but also when a malfunction of VVT 5 is assumed.

  When it is determined Yes in step S1, the process proceeds to step S2. In step S2, air circulation restriction is performed. Specifically, the actuator 11 is driven, and the coupling pin 10 is pulled out from the coupling groove 8 a provided in the second roller arm 8. Thereby, the coupling between the second roller arm 8 and the extending member 9 is released. As a result, the second roller arm 8 driven by the second cam 4b1 is idled, and the second intake valve 3 is maintained in the closed state. When the closed state of the second intake valve 3 is maintained, blowback is suppressed. The amount of air in the cylinder and the temperature in the cylinder are maintained.

  When it is determined No in step S1, the process proceeds to step S3. In step S3, it is determined whether the lubricating oil temperature To1 acquired by the oil temperature sensor 26 is lower than the lubricating oil temperature To0 that is a threshold value. The same determination can be made by employing a cooling water temperature having a correlation with the lubricating oil temperature. In this case, the cooling water temperature is acquired by the water temperature sensor 27. When the lubricating oil temperature is low, the viscosity of the lubricating oil increases. As a result, when the oil temperature is low, the flow rate of the lubricating oil decreases. For this reason, even if a predetermined oil pressure is maintained, the operating speed of the VVT 5 may be slow. When the operation of the VVT 5 is delayed, a period in which blowback occurs is generated, and it is assumed that the engine startability expected by the driver cannot be obtained. Therefore, when the lubricating oil temperature To1 is lower than the threshold value To1, it is determined as Yes and the process proceeds to Step S2. In step S2, blowback is suppressed as described above. As a result, the amount of air in the cylinder and the temperature in the cylinder are maintained.

  When it is determined No in step S3, the process proceeds to step S4. In step S4, it is determined whether an idle condition is satisfied. During idling, it is easily affected by a reduction in the amount of air in the cylinder due to blowback. For this reason, when idle conditions are satisfied, air flow restriction is performed to suppress blowback. When the vehicle speed acquired by the vehicle speed sensor 24 is zero and the accelerator opening acquired by the accelerator opening sensor 25 is zero, it is determined that the idle condition is satisfied. When it is determined Yes in step S4, the process proceeds to step S2. In step S2, blowback is suppressed as described above. As a result, the amount of air in the cylinder and the temperature in the cylinder are maintained.

  When it is determined No in step S4, the process proceeds to step S5. In step S5, it is determined whether or not air circulation is being restricted. After step S2, the measure is a return. For this reason, when the determination of step S5 is performed after the processing of step S2 is performed once, it is determined Yes. When it is determined Yes in step S5, the process proceeds to step S6.

  In step S6, the ECU 20 issues a command to advance the VVT 5 until the target closing time. During the air flow restriction, the VVT 5 is operated to shift to the adjustment of the air amount by the VVT 5.

  In step S7, which is performed subsequent to step S6, the ECU 20 determines whether or not the VVT 5 is operating properly. Whether the VVT 5 is operating properly is determined by whether the operating speed of the VVT 5 is equal to or higher than a predetermined value. Specifically, when the differential value of the cam angle sensor is lower than the specified value with respect to the duty of the OCV 6, it is determined as No because the VVT 5 is not operating properly. If the value acquired by the cam angle sensor 21 does not change despite the VVT 5 operation command being issued, it can be determined that the VVT 5 is not operating properly. When it is determined No, the process returns. If processing returns, measures to restrict air flow will continue. On the other hand, if it is determined Yes in step 7, the process proceeds to step S8, where it is confirmed that the target closing time has been reached, and the target closing time reaching flag is set to ON. And it progresses to step S9 continuously.

  In step S9, the ECU 20 adjusts the air amount to the target air amount while performing throttling. Throttling is performed by controlling the electronic throttle 23. The adjustment of the air amount by the throttling is a measure for returning from the air flow restriction state, and the torque shock can be reduced as much as possible when returning from the air flow restriction state.

  When step S9 is performed, the second intake valve 3 is in a closed state. Even if the VVT 5 is operated in this state, the change in the amount of air in the cylinder is small. For this reason, first, in step S8, the angle is advanced to the target closing timing, and then the air amount is adjusted by throttling. Thereby, torque shock can be reduced. After step S9, the process proceeds to step S10.

  In step S10, air circulation is started. Specifically, the coupling pin 10 is actuated by the actuator 11 and inserted into the coupling groove 8 a provided in the second roller arm 8. As a result, the second roller arm 8 and the extending member 9 are coupled. As a result, the opening / closing drive of the second intake valve 3 is started. After step S10, the process returns.

  When it is determined No in step S5, the process proceeds to step S11. In step S11, it is determined whether or not the target closing time is reached. Specifically, it is determined whether or not the target closing time flag is ON. If the flag is ON, it is determined Yes and the process returns. On the other hand, when it is determined No in step S11, the process proceeds to step S12.

  In step S12, in step S12, the ECU 20 issues a command to advance the VVT 5 until the target closing time, operates the VVT 5, and shifts to adjustment of the air amount by the VVT 5. In step S13 that is performed subsequent to step S12, it is determined whether or not the VVT 5 is operating appropriately, as in step S7. If YES is determined in step 13, the process proceeds to step S14, where it is confirmed that the target closing time has been reached, and the target closing time reaching flag is turned ON. Thereafter, the process returns. On the other hand, when it is determined No in step S13, no action is taken thereafter, and the process returns.

  The variable valve gear 1 repeats the above measures. In the above description, the processes of step S1 and step S3 are measures for determining whether or not the second intake valve 3 that is a variable cam can advance from the retarded state. Here, when it is not possible to advance, it is possible to include a case where it is difficult to advance. In particular, in step S3, the case where the lubricating oil temperature is low and the operating speed of the VVT 5 is slow can be included when the advance cannot be made.

  In this way, when it is determined that the advance cannot be made, the second roller arm 8 is idled and the second intake valve 3 is closed, thereby suppressing air blowback from the cylinder. can do.

  Next, Example 2 will be described with reference to FIGS. The difference between the second embodiment and the first embodiment is as follows. The variable valve operating apparatus 100 according to the second embodiment includes an actuator 41 and a cutoff valve 42 instead of the extending member 9, the coupling pin 10, and the actuator 11 according to the first embodiment. That is, the variable valve operating apparatus 100 according to the second embodiment includes the actuator 41 and the shutoff valve 42 as an air flow restriction device. The actuator 41 drives the shut-off valve 42 to open and close. In the second embodiment, since the coupling pin 10 is not used, the coupling groove 8 a is eliminated from the second roller arm 8.

  As shown in FIG. 10, the shut-off valve 32 is provided so as to cover the intake port 32 provided with the second intake valve 3 which is a variable cam. Thereby, the blowback of the air from the inside of the cylinder can be suppressed.

  The variable valve operating apparatus 100 is controlled in the same manner as the variable valve operating apparatus 1 of the first embodiment. Specifically, the shutoff valve 42 shuts off the intake port 32 in step S2 in the flowchart shown in FIG. 8 and restricts the air flow. Thereby, the blowback from the cylinder is suppressed, and the amount of air in the cylinder is maintained.

  As described above, the variable valve operating apparatus according to the second embodiment is similar to the variable valve operating apparatus according to the first embodiment even in a situation where the cam advance operation is suppressed. Can be improved.

  The form of the shutoff valve is not limited. A butterfly valve, a slide valve, or the like can be employed as the shut-off valve.

  The above embodiments are merely examples for carrying out the present invention. Therefore, the present invention is not limited to these, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims.

DESCRIPTION OF SYMBOLS 1,100 Variable valve apparatus 2 1st intake valve 3 2nd intake valve 4 Cam shaft 4a Inner shaft 4a1 First cam 4b Outer shaft 4b1 Second cam 5 VVC (Variable Valve Timing)
6 OCV (Oil control valve)
7 First roller arm 8 Second roller arm 9 Extension member 10 Connecting pin 11 Actuator 20 ECU
21 Cam angle sensor 22 Crank angle sensor 23 Electronic throttle 24 Vehicle speed sensor 25 Accelerator opening sensor 26 Oil temperature sensor 27 Water temperature sensor 31 First intake port 32 Second intake port 41 Actuator 42 Shut-off valve

Claims (1)

A variable valve operating device for controlling a phase difference between a plurality of intake valves for introducing air into a cylinder,
A camshaft provided with a variable cam capable of delaying at least one of the plurality of intake valves to be in a delayed closed state;
An air flow restricting device that restricts the flow of air into and from the cylinder from the intake valve that is opened and closed via the variable cam;
A determination unit that determines whether or not the variable cam can advance from a retarded state;
A controller that operates the air flow restricting device to suppress air blowback from the cylinder when the determining unit determines that the variable cam cannot advance from the retarded state;
A variable valve gear.

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