JP5556637B2 - engine - Google Patents

Description

  The present invention relates to an engine.

  Of the first and second mechanical valves that are the same type of engine valve provided for the combustion chamber, the valve that can change the opening / closing timing of the second mechanical valve relative to the opening / closing timing of the first mechanical valve Engines with devices are known. Patent Document 1 discloses a valve operating device that changes valve timings of first and second engine valves that are the same type of engine valves provided for one combustion chamber.

  Patent Document 2 discloses an intake cam device for an engine including a setting for an ascending ramp among cam profiles of an intake cam that lifts an intake valve.

JP 2009-144521 A JP 2004-176668 A

  By setting a buffer part (lamp part) in the valve characteristic of the mechanical valve, even if the valve clearance changes due to thermal expansion, it is possible to suppress the jumping of the mechanical valve and the occurrence of seating noise. In this regard, the slower the change rate of the valve lift amount of the mechanical valve in the buffer portion, the lower the operating speed of the mechanical valve that is to be opened or seated, and as a result, the degree of jumping and the seating noise can be further reduced. .

  When the change rate of the valve lift amount in the buffer portion is set to be slow, the characteristics of the intermediate portion connected to the buffer portion among the valve characteristics can be made steep. This is because the operation speed of the mechanical valve that is to be opened or seated is suppressed. When the engine valve is an intake valve, this can improve volumetric efficiency and reduce pump loss. As a result, engine performance can be improved and fuel consumption can be reduced.

  However, there is a limit in setting a slow rate of change of the valve lift amount in the buffer portion. This is because if the change speed is set too low, the amount of change in valve timing corresponding to the amount of change in valve clearance increases, resulting in a large deviation in valve timing.

  In this regard, for example, if the valve timing of the intake valve deviates to the retard side, the volumetric efficiency may be deteriorated due to the blow-back of the in-cylinder gas. In addition, as a result of the delay of the compression start time, a pressure drop at the compression end is caused, which may cause poor ignition and deterioration of exhaust emission. That is, there is such a restriction regarding the setting of the buffer unit.

  In view of the above problems, the present invention relates to the opening and closing timing of the second mechanical valve among the first and second mechanical valves that are the same type of engine valve provided to the combustion chamber. In the case of providing a valve operating device that can be changed, an object is to provide an engine capable of setting a suitable buffer portion and further capable of setting a suitable valve characteristic.

Of the first engine valve and the second mechanical valve, which are the same kind of engine valves provided for the combustion chamber, the present invention uses the opening / closing timing of the second mechanical valve as the opening / closing timing of the first mechanical valve. Among the first valve characteristics of the first mechanical valve, the second mechanical valve has a change rate of the valve lift amount in the first buffer portion. Among the second valve characteristics , the first and second mechanical valves are set to be slower than the rate of change of the valve lift amount in the second buffer unit which is the same type of buffer unit as the first buffer unit. Is the intake valve, and the first and second buffering portions are descending buffering portions, and the first buffering portion starts from the position where the valve lift amount is maximum among the first valve characteristics. The valve lift amount up to the position is the second valve characteristic. Of an engine which is set larger than the valve lift amount between the position where the valve lift amount is maximum from which to begin the second buffer portion.

  According to the present invention, among the first and second mechanical valves that are the same type of engine valve provided for the combustion chamber, the opening / closing timing of the second mechanical valve is set to the opening / closing timing of the first mechanical valve. When a variable valve operating device is provided, a suitable buffer portion can be set, and further, a suitable valve characteristic can be set.

It is a schematic block diagram of an engine. It is a figure which shows the valve mechanism of an engine. It is a figure which shows the principal part of the valve characteristic of the intake valve of Example 1. FIG. It is a figure which shows the example of a change of the valve timing of Example 1. FIG. It is a figure which shows the valve characteristic of the intake valve of Example 2. FIG. It is a figure which shows the principal part of the valve characteristic of the intake valve of Example 2. FIG.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of the engine 50A. The engine 50A includes a cylinder block 51, a cylinder head 52, a piston 53, an intake valve 54, an exhaust valve 55, a fuel injection valve 56, and a VVT (Variable Valve Timing) 57. A cylinder 51 a is formed in the cylinder block 51. A piston 53 is accommodated in the cylinder 51a. A cylinder head 52 is fixed to the upper surface of the cylinder block 51. The combustion chamber E is formed as a space surrounded by the cylinder block 51, the cylinder head 52 and the piston 53.

  The cylinder head 52 is formed with an intake port 52a and an exhaust port 52b. The intake port 52 a guides intake air to the combustion chamber E, and the exhaust port 52 b exhausts gas from the combustion chamber E. The cylinder head 52 is provided with an intake valve 54 and an exhaust valve 55. The intake valve 54 opens and closes the intake port 52a, and the exhaust valve 55 opens and closes the exhaust port 52b. The cylinder head 52 is provided with a fuel injection valve 56. A VVT 57 is also provided.

  FIG. 2 is a view showing a valve mechanism of the engine 50A. The engine 50A has a two-valve structure for both intake and exhaust. In this regard, for convenience of explanation, the two intake valves 54 are hereinafter referred to as the intake valves 54A and 54B. The engine 50A includes first and second camshafts 10A and 20. The first camshaft 10A is provided on the intake valves 54A and 54B side, and the second camshaft 20 is provided on the exhaust valve 55 side.

  The first camshaft 10A is a camshaft having a double structure, and includes an external camshaft 11A, an internal camshaft 12, an external cam 13A, and an internal cam 14. The second camshaft 20 includes an exhaust cam 21. The exhaust cam 21 is provided corresponding to the exhaust valve 55 and operates the exhaust valve 55.

  The external camshaft 11A has a hollow structure. The internal camshaft 12 is inserted into the external camshaft 11A so as to be relatively rotatable. The external cam 13A is provided on the external cam shaft 11A. The external cam 13A is provided corresponding to the intake valve 54A, and operates the intake valve 54A. The phase of the intake valve 54A is not variable but fixed.

  The internal cam 14 is provided so as to be slidable in the circumferential direction on the external camshaft 11A. The internal cam 14 is coupled to the internal camshaft 12. The internal cam 14 is coupled to the internal camshaft 12 by a coupling pin through a long hole provided in the outer camshaft 11A along the circumferential direction. The internal cam 14 is provided corresponding to the intake valve 54B, and operates the intake valve 54B.

  VVT 57 changes the phase of internal camshaft 12 with respect to external camshaft 11A. This makes it possible to change the opening / closing timing of the intake valve 54B relative to the opening / closing timing of the intake valve 54A among the intake valves 54A, 54B, which are the same kind of engine valves provided for the combustion chamber E. The VVT 57 corresponds to a valve gear. The intake valve 54A corresponds to a first engine valve, and the intake valve 54B corresponds to a second engine valve.

  FIG. 3 is a diagram showing the main parts of the valve characteristics F1, F2 of the intake valves 54A, 54B in the engine 50A. The intake valve 54A has a first valve characteristic F1, and the intake valve 54B has a second valve characteristic F2. The first valve characteristic F1 is set by the cam profile of the external cam 13A, and the second valve characteristic F2 is set by the cam profile of the internal cam 14.

  A first buffer part A1 is set for the first valve characteristic F1, and a second buffer part A2 is set for the second valve characteristic F2. The buffer units A1 and A2 are the same type of buffer unit, and specifically are the down buffer units. The buffer portions A1 and A2 make the operation speed of the intake valves 54A and 54B substantially constant.

  Of the first valve characteristic F1, the changing speed of the valve lift amount in the first buffer part A1 is set slower than the changing speed of the valve lift amount in the second buffer part A2 of the second valve characteristic F2. Has been. In the first buffer A1 set in this way, the period required for the same amount of change in the valve lift amount is longer than that of the second buffer A2. Then, the operating speed of the intake valve 54A is made smaller than the operating speed of the intake valve 54B.

  Of the intake valves 54A, 54B, in order to change the opening / closing timing of the intake valve 54B, one that can set the opening / closing timing of the intake valves 54A, 54B independently of each other may be applied. As the VVT 57, for example, the valve gear disclosed in Patent Document 1 described above can be applied. For example, the VVT 57 can also be realized as a configuration having each electromagnetic drive device when the intake valves 54A and 54B are driven electromagnetically. In this case, the valve characteristics F1 and F2 may be set by the VVT 57, for example.

  Next, the function and effect of the engine 50A will be described. FIG. 4 is a diagram showing an example of changing the valve timings of the intake valves 54A and 54B in the engine 50A. As shown in FIG. 4, in the engine 50A having the VVT 57 that can change the opening / closing timing of the intake valve 54B among the intake valves 54A, 54B, the opening / closing timing of the intake valve 54B is retarded from the opening / closing timing of the intake valve 54A. Can be made. Further, fuel consumption can be improved by setting the closing timing of the intake valve 54B to the retard side with respect to the intake bottom dead center and increasing the expansion ratio more than the actual compression ratio.

  On the other hand, when the opening / closing timing of the intake valve 54B is retarded from the opening / closing timing of the intake valve 54A, the intake valve 54B is in a lifting state when the intake valve 54A is closed. Since the restriction on the closing timing of the intake valves 54A and 54B as a whole is received by the closing timing of the intake valve 54B on the late closing side, the first buffering portion A1 that is a buffering portion of the intake valve 54A on the early closing side. Even if the change speed of the valve lift amount at is set to be slow, the restriction due to the slow speed of the buffer A1 is relaxed.

  For this reason, in the engine 50A, the changing speed of the valve lift amount in the first buffer portion A1 is set slower than the changing speed of the valve lift amount in the second buffer portion A2. As a result, the engine 50A including the VVT 57 sets the shock absorbers A1 and A2 that can reduce seating noise when performing the operation of delaying the opening / closing timing of the intake valve 54B from the opening / closing timing of the intake valve 54A. it can.

  The engine 50B according to the present embodiment is substantially the same as the engine 50A except that the first camshaft 10B is provided instead of the first camshaft 10A. The first camshaft 10B is substantially the same as the first camshaft 10A except that the external camshaft 11B is provided instead of the external camshaft 11A. The external camshaft 11B is substantially the same as the external camshaft 11A except that an external cam 13B is provided instead of the external cam 13A. For this reason, the illustration of the engine 50B is omitted.

  FIG. 5 is a diagram showing valve characteristics F1 ′ and F2 of the intake valves 54A and 54B in the engine 50B. The external cam 13B is substantially the same as the external cam 13A except that it has a cam profile that sets the first valve characteristic F1 ′ instead of the first valve characteristic F1. Compared with the first valve characteristic F1, the first valve characteristic F1 ′ has a valve lift amount between a position where the valve lift amount is maximum and a position where the first buffer portion A1 starts. Among the two valve characteristics F2, it is set to be larger than the valve lift amount between the position where the valve lift amount becomes maximum and the position where the second buffer portion A2 starts.

  Next, the function and effect of the engine 50B will be described. FIG. 6 is a diagram showing the main parts of the valve characteristics F1 ′ and F2 of the intake valves 54A and 54B in the engine 50B. The engine 50B sets the first valve characteristic F1 ′ as described above to make the characteristic of the intermediate part M connected to the first buffer part A1 out of the first valve characteristic F1 ′ steep. be able to. As a result, the engine 50B can improve volumetric efficiency and reduce pump loss. As a result, compared with the engine 50A, it is possible to set the valve characteristics F1 ′ and F2 that are preferable in terms of further improving engine performance and reducing fuel consumption.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.
For example, the buffer unit may be an up buffer unit. In this case, the degree of jumping of the engine valve can be reduced. The engine valve may be an exhaust valve. Also in this case, the degree of jumping of the engine valve and the seating sound can be reduced. The engine may be, for example, a spark ignition type internal combustion engine or a compression ignition type internal combustion engine.

First camshaft 10A, 10B
External camshaft 11A, 11B
Internal camshaft 12
External cam 13A, 13B
Internal cam 14
Second camshaft 20
Exhaust cam 21
Engine 50A, 50B
Intake valve 54, 54A, 54B
Exhaust valve 55
VVT 57

Claims (1)

Of the first engine valve and the second mechanical valve that are the same type of engine valve provided for the combustion chamber, the opening / closing timing of the second mechanical valve is set to the opening / closing timing of the first mechanical valve. With variable valve gear,
Of the first valve characteristics of the first mechanical valve, the change rate of the valve lift amount in the first buffer portion is the first valve characteristic of the second mechanical valve of the second mechanical valve. It is set slower than the rate of change of the valve lift amount in the second buffer part, which is the same kind of buffer part as the buffer part ,
The first and second mechanical valves are intake valves, and the first and second buffer parts are descending buffer parts,
Among the first valve characteristics, the valve lift amount between the position where the valve lift amount is maximum and the position where the first buffer portion starts is the valve lift amount among the second valve characteristics. An engine set to be larger than a valve lift amount between a maximum position and a position at which the second buffer portion starts .

Images