JP2004108217A - Four-cycle engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an auxiliary engine brake mechanism of two-cycle compressor type for obtaining a large braking force while suppressing complication of the structure in a four-cycle engine. <P>SOLUTION: The direction of magnetizing poles of electromagnetic coils 34 and 34' is inverted by inverting the direction of the current running in the electromagnetic coils 34 and 34' of a cam shaft side housing 32 connected to an exhaust valve side cam shaft, and the phase difference from permanent magnets 35 and 35' of a gear side housing connected to a timing gear is changed from θ1 to θ2. The exhaust valve side cam shaft is advanced by the phase difference θ (=θ2-θ1), and the regular running mode (Fig. (a)) as a four-cycle engine is switched to the braking mode (Fig. (b)) of two-cycle compressor type. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a four-stroke engine, and more particularly, to an improvement in an engine auxiliary brake mechanism for obtaining a braking force by releasing a compression pressure.
[0002]
[Prior art]
As is well known, a four-stroke engine mounted on an automobile or the like supplies fuel such as gasoline or light oil to a cylinder or a sub-combustion chamber and repeats four strokes of an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. To generate engine driving force.
[0003]
When an automobile goes down a long downhill, a so-called engine brake is used. This engine brake stops the supply of fuel to reduce the generation of driving force in the expansion stroke, and also reduces the compression work in the compression stroke. Thus, the kinetic energy is absorbed on the engine side.
[0004]
By the way, in this engine brake, since the reaction force of the air compressed in the compression stroke becomes a pressure for pressing the piston, a driving force is generated in a stroke subsequent to the compression stroke.
[0005]
Therefore, a third valve for releasing the compressed air is provided, and the third valve is opened near the top dead center of the compression stroke to release the compression pressure, thereby suppressing the generation of the driving force in the subsequent stroke. Has been developed (for example, see Patent Document 1).
[0006]
According to this engine auxiliary brake mechanism, since a large braking force can be obtained, it has already been put to practical use under a trade name such as an engine retarder or a power tard especially in a large truck.
[0007]
In the above-described engine assist brake mechanism, the compression pressure is released only near the top dead center of the compression stroke of the four strokes, and braking is performed once every two rotations of the crankshaft. However, in order to further improve the braking performance, a technique of changing the operation timing of the intake / exhaust valve for each rotation of the crankshaft to release the compression pressure (two-cycle compressor) has been proposed (for example, a two-cycle compressor). And Patent Document 2.).
[0008]
[Patent Document 1]
JP-A-8-158902 (page 2, etc.)
[Patent Document 2]
JP-A-2001-123812 (pages 4 to 5, FIGS. 4 and 6)
[0009]
[Problems to be solved by the invention]
By the way, in the technique according to Patent Document 2, when a braking action is obtained (braking mode), not only the exhaust valve but also the intake valve are set to open / close timing different from the operating state as a normal engine (normal operating mode). You need to control.
[0010]
That is, in the normal operation mode, both the intake valve and the exhaust valve open and close once every two rotations of the crankshaft, but in the braking mode, they open and close once every rotation of the crankshaft.
[0011]
In order to realize such a change in the opening / closing timing and the number of times of opening / closing, a brake rocker arm is provided between the rocker arm for operating the intake / exhaust valve and the intake / exhaust valve, and the normal operation mode and the braking are provided inside the brake rocker arm. A structure in which two hydraulic pistons for switching between the modes are provided is employed.
[0012]
In addition, since the structure of the brake rocker arm needs to be provided for each valve, for example, when the engine has six cylinders and four valves, a total of 24 complicated structures need to be provided.
[0013]
Then, as the structure becomes more complicated, the adjustment of the head of each hydraulic piston is also complicated, which leads to a significant increase in manufacturing cost and deterioration in maintainability.
[0014]
The present invention has been made in view of the above circumstances, and a two-cycle compressor engine assist brake capable of obtaining a strong braking force while suppressing the complexity of the structure while keeping the opening and closing timing of the intake valve in the normal operation mode. It is an object of the present invention to provide a four-stroke engine that can be switched to another engine.
[0015]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, a four-stroke engine according to claim 1 of the present invention is a four-stroke engine having an engine auxiliary brake mechanism for obtaining a braking force by releasing a compression pressure near a top dead center of a compression stroke. The engine auxiliary brake mechanism opens the exhaust valve from near the top dead center of the compression stroke to an expansion stroke, and closes the exhaust valve from near the bottom dead center of the exhaust stroke to the exhaust stroke. Further, there is provided an exhaust valve opening / closing timing changing means for shifting the entire opening / closing timing of only the exhaust valve.
[0016]
Here, “to shift the entire opening / closing timing of the exhaust valve” means that the opening / closing pattern (the ratio between the open period and the closed period and the number of times of opening / closing) of the exhaust valve set for the normal operation mode is determined. This means that only the opening / closing timing for the rotation angle (phase) of the crankshaft is changed without changing.
[0017]
Therefore, even after the opening / closing timing is shifted in this manner, the exhaust valve is only opened once every two rotations of the crankshaft, and the relative timing between the open period and the closed period is reduced. The ratio does not change.
[0018]
According to the four-stroke engine according to claim 1, the exhaust valve opening / closing timing changing means provided in the engine auxiliary brake mechanism causes the exhaust valve to move the exhaust valve from near the top dead center of the compression stroke to the expansion stroke. The entire opening / closing timing of the exhaust valve is shifted, and the opening / closing timing of the intake valve is not changed so that the exhaust valve is opened and the exhaust valve is closed from near the bottom dead center of the exhaust stroke to the exhaust stroke.
[0019]
Therefore, the opening / closing timing of the exhaust valve in the braking mode changed by the exhaust valve opening / closing timing changing means is generally closed in the intake stroke and the compression stroke, opened from near the top dead center of the compression stroke in the expansion stroke, and closed in the exhaust stroke.
[0020]
On the other hand, since the opening / closing timing of the intake valve is not changed, the intake valve remains in the normal operation mode. The intake valve opens during the intake stroke, closes during the compression stroke, the expansion stroke, and the exhaust stroke, and opens near the top dead center of the exhaust stroke during the intake stroke.
[0021]
As a result, the outline of the flow of air into and out of the cylinder is as follows.
(1) In the intake stroke, air is supplied from the intake valve side into the cylinder.
(2) In the compression stroke, the air in the cylinder is compressed and discharged from the exhaust valve side near the top dead center.
(3) In the expansion stroke (corresponding to the second intake stroke in the braking mode of the present invention), air is supplied into the cylinder from the exhaust valve side.
(4) In the exhaust stroke (corresponding to the second compression stroke in the braking mode of the present invention), the air in the cylinder is compressed and discharged from the intake valve near the top dead center. Hereinafter, returning to (1), (1) to (4) are repeated.
[0022]
Therefore, according to the four-stroke engine according to the first aspect, only the entire opening / closing timing of the exhaust valve is shifted. It is possible to realize a two-cycle compressor-based braking mode with a simple structure and capable of obtaining a strong braking force.
[0023]
In the description of the opening / closing operation of the intake / exhaust valves in the above (1) to (4), the rotation angle at which the intake / exhaust valve is opened is approximately 180 ° (converted to the rotation angle of the camshaft) for easy understanding. In this case, the rotation angle of the crankshaft is 1/2, which is about 90 °), and the opening of the intake / exhaust valve of the four-stroke cycle engine of the present invention is not limited to 180 °. .
[0024]
That is, generally, in a normal four-stroke engine, in the normal operation mode, there is a period in which the intake valve and the exhaust valve are overlapped and open, and the intake valve is opened before passing through the top dead center of the intake stroke. Since the exhaust valve opens and closes after passing through the bottom dead center, and the exhaust valve also opens before passing through the bottom dead center and closes after passing through the top dead center, the four-stroke engine of the present invention has the exhaust valve in such a real four-stroke engine. Irrespective of the opening / closing timing, any change may be made so as to shift the entire opening / closing timing.
[0025]
A four-stroke engine according to a second aspect of the present invention is the four-stroke engine according to the first aspect, wherein the exhaust valve opening / closing timing changing means advances the camshaft on the exhaust valve side by a predetermined angle. Means.
[0026]
According to the four-stroke engine according to the second aspect, the camshaft advancing means only advances the phase of the camshaft on the exhaust valve side. The entire opening / closing timing can be changed without changing the relative relationship between the period during which the valve is open and the period during which the valve is closed, and a simple structure can be achieved.
[0027]
The camshaft advancing means includes a means for advancing only the cam portion of the camshaft, in addition to a means for advancing the entire camshaft.
[0028]
Therefore, in a four-cycle engine in which the camshafts are separately provided corresponding to the intake valve side and the exhaust valve side, the entire camshaft on the exhaust valve side may be advanced, and the intake / exhaust valve may be used. In a four-cycle engine driven by a single camshaft, only the cam on the exhaust valve side may be advanced, not the entire camshaft.
[0029]
In order to advance only the cam on the exhaust valve side in this way, for example, the camshaft has a double cylinder structure including an inner cylinder and an outer cylinder, and the intake valve lift cam is mounted on the shaft on the outer cylinder side (or the inner cylinder side). The exhaust valve lifting cam may be provided on the shaft on the inner cylinder side (or the outer cylinder side) to advance the inner cylinder provided with the exhaust valve lifting cam.
[0030]
The four-stroke engine according to a third aspect of the present invention is the four-stroke engine according to the second aspect, wherein the camshaft advancing means is connected to a timing gear that rotates in synchronization with the rotation of the engine. A gear-side housing that rotates integrally, a camshaft-side housing that is connected to the camshaft and rotates integrally with the camshaft, a first phase difference between the timing gear and the camshaft, and a second Selective connection means for integrally connecting the gear-side housing and the camshaft-side housing in one of the phase differences selected from the phase differences; a normal operation mode in which the engine generates a driving force or the braking force; And a mode switching means for switching to a braking mode for obtaining the normal operation mode. Corresponding to timing, the second phase difference, characterized in that it is set corresponding to the opening and closing timing of the braking mode.
[0031]
According to the four-stroke engine according to the third aspect, when the mode selected by the mode switching means is the normal operation mode, the selective connection means is connected to the gear housing by the timing gear. And the camshaft-side housing connected to the exhaust-valve-side camshaft are connected with a first phase difference corresponding to the normal operation mode, so that the opening / closing timing of the exhaust valve becomes the normal operating state of the four-cycle engine. In the case where the mode selected by the mode switching means is the braking mode, the selective connection means connects the gear-side housing and the camshaft-side housing with a second phase difference corresponding to the braking mode. The opening / closing timing of the valve is converted into a two-cycle compressor to exert a strong braking force.
[0032]
Here, the selective connection means selects the first phase difference or the second phase difference by connecting the gear-side housing and the camshaft-side housing by switching the direction of the current flowing through the electromagnetic coil. The connection may be made, or the connection may be made by hydraulic pressure or other mechanical connection means.
[0033]
However, in the actual 4-cycle engine, when switching from the normal operation mode to the braking mode, the engine is driven, and the camshaft is moving at a high speed. The one used is more reliable.
[0034]
Therefore, according to the four-stroke engine of the third aspect of the present invention, the intake valve camshaft and the exhaust valve camshaft are provided without changing the existing exhaust valve and intake valve. In such a case, the phase of the opening / closing timing of the exhaust valve can be easily changed without making a major modification to these existing camshafts.
[0035]
Also, in the four-stroke engine according to claim 4 of the present invention, in the four-stroke engine according to claim 3, the selective connection means is fixed to one of the gear housing and the camshaft housing. An electromagnetic coil, and a permanent magnet fixedly provided on the other side, wherein the mode switching means switches a direction of a current flowing through the electromagnetic coil, and the mode switching means switches the direction of the current flowing through the electromagnetic coil and the direction of the current flowing through the electromagnetic coil. The gear-side housing and the camshaft-side housing are connected at the first phase difference or the second phase difference by relative rotation with a permanent magnet.
[0036]
According to the four-cycle engine according to the fourth aspect, the direction of the electric current to be supplied is reversed, so that the direction of the magnetic force of the electromagnetic coil is reversed.
[0037]
Then, due to the magnetic force of the electromagnetic coil, the electromagnetic coil and the permanent magnet whose one ends are connected to each other in the first phase difference (normal operation mode) are repelled by the reversal of the current direction, and the two are relatively moved. The other ends of the electromagnetic coil and the permanent magnet are connected to each other by the attractive force caused by the rotation and the reversed magnetic force of the electromagnetic coil.
[0038]
Since the phase difference between the two ends when they are connected to each other is the second phase difference (braking mode), the gear-side housing and the cam can be operated only by a simple operation of reversing the direction of the energizing current by the switching means. The shaft side housing, that is, the timing gear and the exhaust side camshaft are connected in a braking mode.
[0039]
Then, by reversing the direction of the current again, the other ends are separated from each other and the one ends are connected to each other, so that they are connected in the normal operation mode.
[0040]
Therefore, according to the four-cycle engine of the fourth aspect of the present invention, the exhaust-side camshaft can be advanced only by reversing the direction of the current to be supplied, and the gear-side housing and the camshaft-side housing are Selective connection can be easily performed between the first phase difference and the second phase difference.
[0041]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, specific embodiments of a four-cycle engine according to the present invention will be described with reference to the drawings.
[0042]
FIG. 1 is a sectional view of a main part of a four-stroke engine according to one embodiment of the present invention. In the illustrated four-cycle engine 100, an intake valve-side camshaft (not shown) and an exhaust valve-side camshaft 63 that drive an intake valve 75 and an exhaust valve 65 provided on an engine head above a cylinder 81 are respectively provided. This is a so-called twin camshaft reciprocating engine provided separately.
[0043]
Here, the exhaust valve 65 is opened when the rocker arm 62 which is in contact with the peripheral surface of the cam formed on the exhaust valve side camshaft 63 and is supported by the rocker shaft 61 presses the upper tappet of the exhaust valve 65.
[0044]
Further, the exhaust valve 65 is urged upward, that is, in a closing direction by a valve spring 66, and the rocker arm 62 continues to abut on the cam of the exhaust valve side camshaft 63 by this urging force, and has a stroke according to the cam profile. The exhaust valve 65 is pressed.
[0045]
The camshaft and the like on the intake valve 75 side have the same configuration as the exhaust valve 65 side, but the intake valve 75 side is omitted from the drawing because it is provided on the near side in the drawing with respect to the cross section in the drawing. I have.
[0046]
A normal operation mode M1 in which the engine 100 performs a normal operation as a four-stroke engine and an engine brake (engine auxiliary brake) is operated without performing fuel injection on a peripheral surface of a longitudinal end portion of the exhaust valve side camshaft 63. There is provided a camshaft advance timer (camshaft advance means) 30 which is an exhaust valve opening / closing timing changing means for switching the braking mode M2 to be switched.
[0047]
The camshaft advance timer 30 is provided only on the exhaust valve 65 side to open the exhaust valve 65 from near the top dead center (TDC) of the compression stroke to the entire expansion stroke, and to lower the exhaust stroke of the exhaust stroke. The opening / closing timing of the exhaust valve 65 is uniformly shifted so as to close the exhaust valve 65 from the vicinity of (BDC) over the entire exhaust stroke.
[0048]
Here, the detailed configuration of the camshaft advance timer 30 is shown in FIGS. FIG. 2B is a cross-sectional view of a main part similar to FIG. 1, FIG. 2A is a diagram showing a right view of FIG. 2B, and FIG. FIG. 2D is a cross-sectional view showing a cross section taken along line AA of FIG.
[0049]
The camshaft advance timer 30 includes a gear-side housing 31 that rotates integrally with a timing gear 64 that rotates at half the number of revolutions of a crankshaft (not shown) in synchronization with the rotation of the engine 100; A camshaft side housing 32 connected to the exhaust valve side camshaft 63 and rotating integrally with the camshaft 63, a cap 40 fixed to the camshaft side housing 32, a timing gear 64 and a camshaft 63. Selective connecting means 33 for integrally connecting the gear-side housing 31 and the camshaft-side housing 32 at one phase difference θ1 selected from the one phase difference θ1 (see FIG. 3) and the second phase difference θ2. And a mode switching switch (mode switching means) for switching the engine 100 to the normal operation mode M1 or the braking mode M2. 39 and a configuration in which a.
[0050]
Here, the selective connection means 33 is composed of two permanent magnets 35 and 35 ′ fixed to the gear housing 31 symmetrically with respect to the rotation axis, and two electromagnetic magnets fixed to the camshaft housing 32 symmetrically with respect to the rotation axis. The electromagnetic coils 34 and 34 'each have an iron core 34c.
[0051]
The clockwise end face 35a of the permanent magnet 35 is magnetized so as to have an S pole, the counterclockwise end face 35b is magnetized so as to have an N pole, and the clockwise end face 35a 'of the permanent magnet 35' is an N pole. The counterclockwise end face 35b 'is magnetized so as to be an S pole.
[0052]
On the other hand, the windings of the electromagnetic coil 34 and the electromagnetic coil 34 'are wound in opposite directions.
[0053]
The mode changeover switch 39 switches the direction of the current flowing through the electromagnetic coils 34 and 34 '. For example, when the mode is switched to the side indicated by the solid line in FIG. 3A, the brush rotors 41a and 41b of the cap 40 are switched. A current flows from one of the two electric wires 39a and 39b passing through the electromagnetic coils 34 and 34 'to the other electric wire 39b through the windings of the electromagnetic coils 34 and 34'. When the switch is made to the side shown in FIG. 3B, the current flows from the other electric wire 39b to the one electric wire 39a through the windings of the electromagnetic coils 34 and 34 '. .
[0054]
Since the winding directions of the windings of the two electromagnetic coils 34 and 34 'are opposite to each other, the clockwise end face 34a of the electromagnetic coil 34 is magnetized to the S pole, and the counterclockwise end face 34b is magnetized to the N pole. Then, the clockwise end face 34a 'of the other electromagnetic coil 34' is magnetized to the N pole, and the counterclockwise end face 34b 'is magnetized to the S pole.
[0055]
In addition, in the case shown in FIG. 3A and the case shown in FIG. 3B, the directions of the currents flowing through the respective electromagnetic coils 34 and 34 'are opposite to each other. The magnetic poles S and N generated at 34b and the magnetic poles N and S generated at both end surfaces 34a 'and 34b' of the electromagnetic coil 34 'are reversed.
[0056]
Therefore, for example, when the mode changeover switch 39 is switched to the side shown in FIG. 3A, the clockwise end face 34a (S pole) of the electromagnetic coil 34 and the counterclockwise end face of the permanent magnet 35 35b (N pole) is attracted and connected by magnetic force, and the clockwise end face 34a '(N pole) of the electromagnetic coil 34' and the counterclockwise end face 35b '(S pole) of the permanent magnet 35' are connected. Are attracted and connected by magnetic force.
[0057]
On the other hand, when the mode changeover switch 39 is switched to the side shown in FIG. 3B, the counterclockwise end face 34b (S-pole) of the electromagnetic coil 34 and the clockwise end face 35a of the permanent magnet 35 '. (N-pole) are attracted and connected by magnetic force, and the counterclockwise end face 34b '(N-pole) of the electromagnetic coil 34' and the clockwise end face 35a (S-pole) of the permanent magnet 35 are magnetically attracted. And are connected by
[0058]
When the mode switch 39 is switched from (a) to (b) or from (b) to (a), the relative phase relationship between the permanent magnets 35, 35 'and the electromagnetic coils 34, 34' changes. That is, relative rotation occurs between the two, but since the permanent magnets 35, 35 'are fixed to the gear-side housing 31 integrated with the timing gear 64, the sides of the electromagnetic coils 34, 34' rotate. .
[0059]
Since the electromagnetic coils 34, 34 'are fixed to the camshaft side housing 32 connected to the exhaust valve side camshaft 63, the rotation of the electromagnetic coils 34, 34' rotates the exhaust valve side camshaft 63. That is, it is advanced.
[0060]
Here, the phase difference θ1 between the permanent magnet 35 and the electromagnetic coil 34 (the phase difference between the permanent magnet 35 'and the electromagnetic coil 34') in the state shown in FIG. It is set so as to open and close at a corresponding timing, and in the normal operation mode M1, the intake valve 75 and the exhaust valve 65 are opened only during the period indicated by the thick arrow in FIG.
[0061]
That is, the intake valve 75 opens from 7.5 ° before TDC in the intake stroke (1) to 10 ° after passing BDC in the intake stroke (1), and the exhaust valve 65 opens from 15 ° before BDC in the exhaust stroke (4). Open up to 2.5 ° after passing through TDC in (4).
[0062]
On the other hand, the phase difference θ2 between the permanent magnet 35 and the electromagnetic coil 34 (the phase difference between the permanent magnet 35 'and the electromagnetic coil 34') in the state shown in FIG. 3B indicates that the exhaust valve 65 corresponds to the braking mode M2. It is set to open and close at the timing, and in the braking mode M2, the intake valve 75 and the exhaust valve 65 are opened only during the period indicated by the thick arrow in FIG.
[0063]
That is, the intake valve 75 opens from 7.5 ° before TDC in the intake stroke (1) to 10 ° after passing BDC in the intake stroke (1), and the exhaust valve 65 opens 7 ° before TDC in the second intake stroke (1 ′). It opens from 0.5 ° to 10 ° after passing through the BDC in the second intake stroke (1 ′).
[0064]
Accordingly, the camshaft 63 on the exhaust valve side is advanced by the phase difference θ = 82.5 ° from the opening / closing timing shown in FIG. 4A to the opening / closing timing shown in FIG. 4B.
[0065]
Therefore, the rotation angle (= θ2−θ1) of the electromagnetic coil 34 shown in FIG. 3 is set to 82.5 °.
[0066]
The second intake stroke (1 ') in the braking mode M2 is a stroke corresponding to the explosion-expansion stroke in the normal operation mode M1, and the second compression stroke (2') is a stroke corresponding to the exhaust stroke in the normal operation mode M1. The corresponding process.
[0067]
Next, the operation of the four-stroke engine 100 according to the present embodiment will be described with reference to FIGS. 5 to 8, in which each stroke (intake stroke (1), (1), (2)) in the (a) normal operation mode M1 and (b) the braking mode M2 engine. The operation (opening and closing) of the intake valve 73 and the exhaust valve 63 in the compression stroke (2), the explosion-expansion stroke (3), and the exhaust stroke (4)) and the state of intake and exhaust will be described.
[0068]
First, when an operator such as a driver switches the mode changeover switch 39 to the state shown in FIG. 3A, the clockwise end face 34a (S-pole) of the electromagnetic coil 34 and the counterclockwise The surrounding end face 35b (N pole) attracts by magnetic force, and the clockwise end face 34a '(N pole) of the electromagnetic coil 34' and the counterclockwise end face 35b '(S pole) of the permanent magnet 35' are attracted by magnetic force. The gear-side housing 31 and the camshaft-side housing 32 rotate together with the timing gear 64 in the direction of the thick arrow in the drawing (counterclockwise) while maintaining the connected state.
[0069]
Since the camshaft-side housing 32 is integrally connected to the exhaust-valve-side camshaft 63, the opening / closing timing of the exhaust valve 65 driven to be opened / closed by the exhaust-valve-side camshaft 63 is the normal opening / closing timing shown in FIG. The operation mode is set to M1.
[0070]
There is no distinction between the normal operation mode M1 and the braking mode M2 on the intake valve side camshaft, and is always fixed to a state corresponding to the normal operation mode M1 regardless of the mode of the exhaust valve side camshaft 63. .
[0071]
Hereinafter, a description will be given with reference to FIGS. 5A to 8A showing states of intake and exhaust to and from the engine 100 in the normal operation mode M1.
[0072]
The opening and closing timing charts of the intake valve 75 and the exhaust valve 65, which are shown in each figure, are the same as those shown in FIG.
[0073]
Further, the normal operation mode M1 is the same as the operation of a general four-stroke engine, and will be described briefly.
[0074]
First, as shown in FIG. 5A, in the TDC in the intake stroke (1), the exhaust valve 65 closes, and the intake valve 75 starts opening immediately before (7.5 ° before TDC), and after the passage of TDC, At 0.5 °, the exhaust valve 65 closes, and the air-fuel mixture flows into the cylinder 81 from the intake valve 75 due to the negative pressure generated by the lowering of the piston 82.
[0075]
The intake valve 75 closes at 10 ° after the passage of the BDC during the intake stroke, because the air-fuel mixture can be further charged into the cylinder 81 even after the BDC due to the inertia of the intake air.
[0076]
Next, as shown in FIG. 6A, the intake valve 75 closes at 10 ° after passing through the BDC in the compression stroke (2) (the BDC in the intake stroke (1)), and the piston 82 rises, thereby causing The air-fuel mixture is compressed and gradually rises in temperature. The air-fuel mixture is ignited by ignition of a spark plug (not shown) near TDC, and the air-fuel mixture explodes.
[0077]
The above is the case of the gasoline engine. However, in the case of the diesel engine, only air or a mixture having a low fuel ratio is taken in instead of the mixture, and the fuel is supplied to the cylinder near the TDC in the compression stroke (2). It is injected into the inside or into the sub-combustion chamber, causing an explosion by self-ignition.
[0078]
Next, as shown in FIG. 7A, in the explosion compression stroke (3), the exploded air-fuel mixture expands and pushes down the piston 82 to generate a driving force, and the exhaust valve 65 opens from 15 ° before BDC, As shown in FIG. 8A, the gas in the cylinder 81 is exhausted from the exhaust valve 65 as the piston 82 rises, and the exhaust valve 65 closes at 2.5 ° after passing through TDC, while 7.5 before TDC. °, the intake valve 75 starts to open, returns to the intake stroke (1), and the above cycle is repeated to continuously generate a driving force.
[0079]
Next, the operation in the braking mode M2 in which the generation of the driving force is stopped to obtain the braking force as the engine auxiliary brake will be described.
[0080]
First, the operator switches the mode changeover switch 39 from the state shown in FIG. 3A to the state shown in FIG.
[0081]
By the switching of the switch 39, the direction of the current flowing through the electric wires 39a, 39b is reversed, the directions of the magnetic poles of the electromagnetic coils 34, 34 'are respectively reversed, and the clockwise side end surface 34a of the electromagnetic coil 34 becomes the N pole. The counterclockwise end face 34b has an S pole, the clockwise end face 34a 'of the electromagnetic coil 34' has an S pole, and the counterclockwise end face 34b 'has an N pole.
[0082]
As a result, the clockwise end face 34a (N pole) of the electromagnetic coil 34 and the counterclockwise end face 35b (N pole) of the permanent magnet 35 have the same magnetic pole and repel each other, and the clockwise rotation of the electromagnetic coil 34 '. The side end surface 34a '(S-pole) and the counterclockwise end surface 35b' (S-pole) of the permanent magnet 35 'have the same magnetic pole and repel each other, so that the camshaft-side housing 32 rotates counterclockwise.
[0083]
The counterclockwise end face 34b (S-pole) of the electromagnetic coil 34 and the clockwise end face 35b '(N-pole) of the permanent magnet 35' are attracted and connected by magnetic force. The rotation side end surface 34a '(N pole) and the clockwise side end surface 35b (S pole) of the permanent magnet 35 are attracted and connected by magnetic force.
[0084]
Therefore, the camshaft side housing 32 is advanced by the phase difference θ = 82.5 °, and is switched to the braking mode M2. Note that, in the braking mode M2, the supply of fuel (including the case of an air-fuel mixture) into the cylinder 81 is not performed.
[0085]
Hereinafter, a description will be given with reference to FIGS. 5B to 8B showing a state of intake and exhaust to and from the engine 100 in the braking mode M2.
[0086]
First, as shown in FIG. 5B, in the TDC of the intake stroke (1), the intake valve 75 starts to open immediately before (7.5 ° before TDC), and the negative pressure generated by the lowering of the piston 82 causes the intake valve 75 to open. From the air flows into the cylinder 81.
[0087]
Next, as shown in FIG. 6B, the intake valve 75 closes at 10 ° after the passage of the BDC in the compression stroke (2), the air in the cylinder 81 is compressed by the rise of the piston 82, and the engine 100 performs this compression. Drive energy is consumed by work.
[0088]
Then, the exhaust valve 65 starts opening from 7.5 ° before TDC, and the compressed air in the cylinder is exhausted from the exhaust valve 65 to the outside.
[0089]
When this compressed air is not discharged from the cylinder 81, the piston 82 is pushed down after passing through the TDC and becomes an energy source for generating the driving force of the engine 100. It functions as an engine auxiliary brake of the compression pressure release type without generating any compression.
[0090]
Further, the exhaust valve 65 continues to open as shown in FIG. 7B even after passing through the TDC, and as the piston 82 descends, air is drawn into the cylinder 81 from the exhaust valve 65 by the negative pressure in the cylinder 81. You.
[0091]
Therefore, this stroke is an explosion-expansion stroke (3) in the normal operation mode M1, but is an intake stroke in which the exhaust valve is opened in the braking mode M2, similarly to the intake stroke (1) in which the intake valve 75 is opened (No. Second intake stroke (1 ')).
[0092]
Air is sucked into the cylinder 81 by the second intake stroke (1 '), and as shown in FIG. 8B, the exhaust valve is set at 10 [deg.] After passing through the BDC in the subsequent second compression stroke (2'). When the piston 65 rises, the air in the cylinder 81 is compressed, and the engine 100 consumes driving energy by this compression work.
[0093]
Then, the intake valve 75 starts to open from 7.5 ° before TDC, and the compressed air in the cylinder 81 is exhausted from the intake valve 75 to the outside.
[0094]
When this compressed air is not discharged from the cylinder 81, the piston 82 is pushed down after passing through the TDC and becomes an energy source for generating the driving force of the engine 100. It functions as an engine auxiliary brake of the compression pressure release type without generating any compression.
[0095]
Then, the process returns to the subsequent intake stroke (1), and the above cycle is repeated.
[0096]
As described above, the four-cycle engine 100 according to the present embodiment functions as a conventional four-cycle engine with two rotations of the crankshaft in the normal operation mode M1. Since compression and compression pressure release can be performed, it is possible to obtain an engine auxiliary brake having a larger braking force than before.
[0097]
Further, in the braking mode M2, compared to the normal operation mode M1, only the opening / closing timing of the exhaust valve 65 is changed without changing the intake valve 75 side. An engine auxiliary brake mechanism can be configured.
[0098]
Furthermore, since the ratio between the open period and the closed period of the exhaust valve 65 is not changed between the normal operation mode M1 and the braking mode M2, the phase of the exhaust valve side camshaft 63 (strictly, the cam) is changed. In this regard, the structure can be further simplified.
[0099]
A simple mode switching operation can be achieved by applying a combination of the permanent magnets 35 and 35 'and the electromagnetic coils 34 and 34' whose magnetic poles are reversed by switching the direction of the energizing current as the advancing means of the camshaft 63. And can be retrofitted to existing 4-stroke engines with only minor modifications.
[0100]
The four-stroke engine 100 according to the present embodiment has a configuration in which the open period of the intake valve 75 and the open period of the exhaust valve 65 are the same (both are 107.5 ° in terms of the camshaft rotation angle). Therefore, the opening / closing timing of the intake valve 75 and the exhaust valve 65 with respect to TDC and BDC in the braking mode M2 can be set to be the same, but the four-stroke engine of the present invention is not limited to such a mode. .
[0101]
That is, since the opening period of the intake valve 75 and the opening period of the exhaust valve 65 are set for each engine so as to obtain optimal intake and exhaust in the normal operation mode M1, respectively, the opening period of both valves 75 and 65 is set. Are not always the same.
[0102]
Even in such a case, in the four-cycle engine of the present invention, in the braking mode M2, the opening and closing timing of the intake valve 75 and the opening and closing timing of the exhaust valve 65 may be set to be substantially the same, and the compression stroke (2 The exhaust valve 65 may be opened near the TDC, and the opening / closing timing of the exhaust valve 65 may be changed so that the compression pressure of the compression stroke (2) is released from the exhaust valve 65.
[0103]
The specific numerical values related to the opening and closing timings of the intake valve 75 and the exhaust valve 65 are merely examples in the embodiment, and the four-stroke engine of the present invention opens and closes at such specific numerical values. Needless to say, the invention is not limited to those having an exhaust valve.
[0104]
【The invention's effect】
As described above, according to the four-stroke engine according to the first aspect of the present invention, only the entire opening / closing timing of the exhaust valve is shifted, and the conventional method of changing the opening / closing timing and the number of opening / closing of each intake / exhaust valve is used. As compared with the engine auxiliary brake mechanism, it is possible to realize a two-cycle compressor-based braking mode that can obtain a strong braking force with a simple structure.
[0105]
According to the four-stroke engine according to the second aspect of the present invention, in addition to the effect exhibited by the four-stroke engine according to the first aspect, the camshaft advancing means adjusts the phase of the camshaft on the exhaust valve side. Because it only advances, it is possible to change the entire opening and closing timing between the normal operation mode and the braking mode without changing the relative relationship between the period when the exhaust valve is open and the period when the exhaust valve is closed. Structure.
[0106]
According to the four-stroke engine of the third aspect of the present invention, the existing exhaust valve and intake valve are not changed, and the intake valve camshaft and the exhaust valve camshaft are provided. In such a case, the phase of the opening / closing timing of the exhaust valve can be easily changed without making a major modification to these existing camshafts.
[0107]
Further, according to the four-stroke engine of the fourth aspect of the present invention, the exhaust-side camshaft can be advanced only by reversing the direction of the current to be supplied, and the gear-side housing and the camshaft-side housing are Selective connection can be easily performed between the first phase difference and the second phase difference.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a cross-sectional view of a main part of a four-cycle engine according to an embodiment of the present invention.
FIG. 2 is a diagram showing a specific configuration of a camshaft advance timer.
FIG. 3 is a diagram illustrating the operation of a camshaft advance timer.
FIG. 4 is a diagram showing an opening / closing chart of an intake valve and an exhaust valve in a normal operation mode and a braking mode.
FIG. 5 is a diagram illustrating a ventilation state in an intake stroke (1) in a normal operation mode and a braking mode.
FIG. 6 is a diagram illustrating a ventilation state in a compression stroke (2) in a normal operation mode and a braking mode.
FIG. 7 is a diagram illustrating a ventilation state of an explosion-expansion stroke (3) and a second intake stroke (1 ′) in a normal operation mode and a braking mode.
FIG. 8 is a diagram for explaining a ventilation state in an exhaust stroke (4) and a second compression stroke (2 ′) in a normal operation mode and a braking mode.
[Explanation of symbols]
30 Camshaft advance timer
31 Gear side housing
32 Camshaft side housing
33 Selective connection means
34, 34 'electromagnetic coil
34a, 34a 'clockwise end face
34b, 34b 'counterclockwise end face
34c iron core
35,35 'permanent magnet
35a, 35a 'clockwise end face
35b, 35b 'counterclockwise end face
39 Mode switch
39a, 39b electric wire
40 cap
41a, 41b brush rotor
61 Rocker shaft
62 rocker arm
63 Exhaust valve side camshaft
64 timing gear
65 exhaust valve
66 Valve spring
73 Intake valve side camshaft
75 Intake valve
81 cylinder
82 piston
100 4 cycle engine
θ, θ1, θ2 phase difference

Claims (4)

In a four-stroke engine equipped with an engine auxiliary brake mechanism that releases a compression pressure near the top dead center of the compression stroke to obtain a braking force,
The engine auxiliary brake mechanism opens the exhaust valve from near the top dead center of the compression stroke to an expansion stroke, and closes the exhaust valve from near the bottom dead center of the exhaust stroke to the exhaust stroke. A four-stroke engine comprising exhaust valve opening / closing timing changing means for shifting the entire opening / closing timing of only the exhaust valve. The four-stroke engine according to claim 1, wherein the exhaust valve opening / closing timing changing means is a camshaft advance means for advancing a camshaft on the exhaust valve side by a predetermined angle. The camshaft advancing means is connected to a timing gear that rotates in synchronization with rotation of the engine and is connected to the timing gear. The gear-side housing is connected to the camshaft and integrated with the camshaft. And the camshaft-side housing, and the gear-side housing and the camshaft-side housing at one phase difference selected from a first phase difference and a second phase difference between the timing gear and the camshaft. And a mode switching means for switching to a normal operation mode in which the engine generates driving force or a braking mode in which the braking force is obtained, wherein the first phase difference is equal to the normal phase. Corresponding to the opening / closing timing of the operation mode, the second phase difference is set corresponding to the opening / closing timing of the braking mode. 4-cycle engine according to claim 2, characterized in that there. The selective connection means includes an electromagnetic coil fixed to one of the gear-side housing and the camshaft-side housing, and a permanent magnet fixed to the other, and the mode switching means includes the electromagnetic coil. The gear-side housing and the camshaft-side housing are connected to each other by the relative rotation of the electromagnetic coil and the permanent magnet according to the direction of the current flow. The four-stroke engine according to claim 3, wherein the four-stroke engine is connected at one phase difference or the second phase difference.

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