JP2004176692A - Exhaust brake device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust brake device which is high in brake force even in a low speed area. <P>SOLUTION: The invention provides the exhaust brake device featured that a cam profile for an exhaust valve is formed such that a valve system capable of applying a given lift amount on an exhaust valve during operation of an exhaust brake is provided, and at a suction stroke, a compression stroke, and an expansion stroke when the exhaust brake is operated by the valve system, the exhaust valve is opened only at a compression top dead center, and in other region, the exhaust valve is closed, and the exhaust valve is closed in all the regions of suction, compression, and expansion strokes during normal operation. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an exhaust brake device that generates a braking force by increasing negative work of an engine using an exhaust valve.
[0002]
[Prior art]
In general, in a large vehicle, an exhaust brake, which is one of auxiliary brakes, plays a large role in safely traveling on a long downhill or the like.
[0003]
In this exhaust brake, exhaust resistance of exhaust gas exhausted from an exhaust port during an exhaust stroke of an engine is increased by restricting an exhaust throttle valve provided in an exhaust pipe or the like, thereby obtaining a braking force.
[0004]
As an effective means for increasing the engine braking force in this way, in addition to the exhaust brake, a hydraulic actuator is provided in the rocker cover of the cylinder head, and the hydraulic actuator is driven when the brake is operated, so that the exhaust valve or the third valve 2. Description of the Related Art A decompression brake for a diesel engine for a vehicle, which increases a negative work of the engine by opening the engine, is known.
[0005]
As a method of opening the exhaust valve in the engine compression step, Japanese Utility Model Laid-Open No. 6-34104 discloses a method in which an eccentric rocker shaft is used, the rocker shaft is rotated down, and the exhaust valve is opened. Further, Japanese Patent Application Laid-Open No. 8-15836 discloses a method in which an eccentric bush provided on a rocker arm and a lever and an actuator for rotating the eccentric bush lower the rocker arm and open an exhaust valve.
[0006]
However, in these means, there is a case where the braking force is still insufficient, and there is a problem that a sufficient braking force cannot be obtained particularly in a low speed range.
[0007]
[Problems to be solved by the invention]
The present invention has been made in view of such circumstances, and has as its main object to provide an exhaust brake device having a large braking force even in a low speed range.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has a valve operating mechanism capable of applying a predetermined lift amount to an exhaust valve when an exhaust brake is actuated. In the intake, compression, and expansion strokes when the exhaust brake is actuated by the valve mechanism, the exhaust valve opens only at the compression top dead center, the exhaust valve closes in other areas, and intake, compression, and normal operation during normal operation. An exhaust brake device characterized in that a cam profile for the exhaust valve is formed so that the exhaust valve is closed in all regions of the expansion stroke.
[0009]
In the present invention, a predetermined lift amount is added to the exhaust valve by using a valve operating mechanism, so that the exhaust valve is opened only at the compression top dead center during the intake, compression, and expansion strokes during the operation of the exhaust brake. A profile has been formed. Therefore, at this time, since the air in the cylinder flows into the exhaust pipe, the pressure in the cylinder can be reduced, so that the negative work of the engine in the subsequent expansion stroke can be increased, and as a result, the braking force Can be increased. Further, in a state where a predetermined lift amount is not added to the exhaust valve by the valve operating mechanism, that is, in a normal operation state, the cam profile is designed so that the exhaust valve does not open at the compression top dead center. The engine efficiency does not decrease during normal operation.
[0010]
Further, in the present invention, as described in claim 2, a valve operating mechanism capable of applying a predetermined lift amount to the exhaust valve at the time of operating the exhaust brake is provided, and the exhaust brake is operated by the valve operating mechanism. In the intake, compression, and expansion strokes when activated, the exhaust valve opens only immediately after the intake stroke, the exhaust valve closes in other areas, and in all areas of the intake, compression, and expansion strokes during normal operation. An exhaust brake device is provided, wherein a cam profile for the exhaust valve is formed so as to close the exhaust valve. In the present invention, the cam profile is formed by adding a predetermined lift amount to the exhaust valve by the valve operating mechanism so that the exhaust valve opens only immediately after the intake stroke in the intake, compression, and expansion strokes during the operation of the exhaust brake. Have been. Therefore, at this time, since the air in the exhaust pipe flows into the cylinder, the negative work of the engine in the subsequent compression stroke can be increased, and as a result, the braking force can be increased. Further, in a state where a predetermined lift amount is not applied to the exhaust valve by the valve operating mechanism, that is, in a normal operation state, the cam profile is designed so that the exhaust valve does not open immediately after the intake stroke. Efficiency does not decrease during operation.
[0011]
Further, in the present invention, as described in claim 3, a valve operating mechanism capable of applying a predetermined lift amount to the exhaust valve at the time of operating the exhaust brake is provided, and the exhaust brake is operated by the valve operating mechanism. During the intake, compression, and expansion strokes during operation, the exhaust valve opens only at the compression top dead center and immediately after the intake stroke, the exhaust valve closes in other regions, and the intake, compression, and expansion strokes during normal operation. A cam profile for the exhaust valve is formed such that the exhaust valve is closed in all the regions.
[0012]
In the present invention, by adding a predetermined lift amount to the exhaust valve by the valve operating mechanism, in the intake, compression, and expansion strokes during the operation of the exhaust brake, the exhaust valve is opened only immediately after the compression top dead center and immediately after the intake stroke. , A cam profile is formed. Therefore, by opening the exhaust valve immediately after the intake stroke, the air in the exhaust pipe flows into the cylinder, increasing the negative work of the engine in the subsequent compression stroke, and further opening the exhaust valve at the compression top dead center. Since the air in the cylinder flows into the exhaust pipe, the negative work of the engine in the subsequent expansion stroke can be increased. Therefore, the braking force of the exhaust brake can be greatly improved. Further, in a state where a predetermined lift amount is not applied to the exhaust valve by the valve operating mechanism, that is, in a normal operation state, the cam profile is designed so that the exhaust valve does not open immediately after the above-described compression top dead center and the intake stroke. Therefore, the efficiency does not decrease during normal operation.
[0013]
Still further, according to the present invention, there is provided a valve operating mechanism capable of applying a predetermined lift amount to the exhaust valve at the time of operating the exhaust brake. In the intake, compression, and expansion strokes when the valve operates, the exhaust valve opens from immediately after the intake stroke to the compression top dead center, the exhaust valve closes in other regions, and the intake, compression, and expansion strokes during normal operation. A cam profile for the exhaust valve is formed such that the exhaust valve is closed in all the regions.
[0014]
In the present invention, by adding a predetermined lift amount to the exhaust valve by the valve operating mechanism, in the intake, compression, and expansion strokes during the operation of the exhaust brake, the exhaust valve is opened from immediately after the intake stroke to the compression top dead center, A cam profile is formed. Therefore, by opening the exhaust valve immediately after the intake stroke, the air in the exhaust pipe flows into the cylinder, and the negative work of the engine in the subsequent compression stroke can be increased, greatly improving the braking force of the exhaust brake. Can be done. Further, in the case of opening the valve while maintaining a predetermined lift amount by the valve operating mechanism at the compression top dead center, a large stress is applied to the valve operating mechanism. In this case, such an operation is performed. Since there is no valve operating mechanism, the valve operating mechanism may have a structure that can withstand relatively small stress, and the valve operating mechanism can be simplified.
[0015]
In the first or third aspect of the present invention, as described in the fifth aspect, when the exhaust valve opens at the compression top dead center, the peak of the cam profile becomes 540 ° ± 10 °. Is preferably formed. This is because the most effective timing for opening the exhaust valve at the compression top dead center is within the above range.
[0016]
In the invention described in claim 4, as described in claim 6, when the exhaust valve opens from immediately after the intake stroke to the compression top dead center, the closing timing of the exhaust valve is 540 ° ± 45 °. It is preferable that the cam profile is formed so as to fall within the range. By setting the timing at which the exhaust valve closes within the above range, the balance between the exhaust braking force and the load applied to the valve system can be balanced, and the valve system can be balanced with the effect on the valve reinforcement cost. Further, since the optimum and effective valve timing differs depending on the speed of the engine, it is desirable to select within the above range.
[0017]
Further, in the invention described in claim 2, claim 3, claim 4, or claim 6, as described in claim 7, when the exhaust valve is opened immediately after the intake stroke, the exhaust valve is closed. It is preferable that the cam profile is formed so that the opening starts within a range from 10 ° before the intake valve closes to 10 ° after the intake valve closes. This is because the most effective timing for opening the exhaust valve immediately after the intake stroke is within the above range.
[0018]
In the invention described in any one of the first to seventh aspects, as described in the eighth aspect, the valve operating mechanism supports the rocker arm of the exhaust valve on the eccentric portion of the rocker shaft. It is preferable that the valve mechanism be configured to lower the rocker arm of the eccentric portion by rotating the rocker shaft to thereby apply a predetermined lift amount to the exhaust valve. This is because a predetermined amount of lift can be given to the exhaust valve with a simple configuration, which is advantageous in terms of reliability and cost.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the exhaust brake device of the present invention will be described. The exhaust brake device of the present invention can have four embodiments depending on the timing of opening the exhaust valve when the exhaust brake is operated. Hereinafter, each embodiment will be described.
[0020]
A. First embodiment
The first embodiment of the exhaust brake device of the present invention has a valve operating mechanism that can apply a predetermined lift amount to the exhaust valve when the exhaust brake is operated,
In the intake, compression, and expansion strokes when the exhaust brake is actuated by the valve operating mechanism, the exhaust valve opens only at the compression top dead center, the exhaust valve closes in other regions, and intake and compression during normal operation. , And a cam profile for the exhaust valve such that the exhaust valve is closed in all regions of the expansion stroke.
[0021]
FIG. 1 shows the movement of a stem pressing portion for pressing the stem of the exhaust valve of the rocker arm in the present embodiment, and FIG. 2 shows the movement of the exhaust valve at that time. The solid line indicates a state in which the valve operating mechanism is not operating in the normal operation state, and the broken line indicates a state in which a predetermined lift amount is added to the exhaust valve by the valve operating mechanism.
[0022]
In a state where the valve operating mechanism is not operated, that is, in a normal operation state, the stem pressing portion is located at a minus position, that is, a position separated by a predetermined lift amount from the stem of the exhaust valve in the intake, compression, and expansion strokes. Will do. Also, even near 540 °, that is, near the compression top dead center, the stem of the exhaust valve is not pressed down.
[0023]
Then, in a state where the valve operating mechanism is operated and a predetermined lift amount is added, that is, in a state where the exhaust brake device is operated, the stem of the exhaust valve is pressed only around 540 °, that is, near the compression top dead center, and The exhaust valve is opened by the amount of the lift, and the exhaust valve is closed during the other intake, compression, and expansion strokes.
[0024]
In this embodiment, by operating the valve operating mechanism in this manner, the exhaust valve can be temporarily opened near the compression top dead center, so that the compressed air in the cylinder is released into the exhaust pipe. Can be. Therefore, in the subsequent expansion stroke, the negative work load on the engine can be increased, and as a result, a strong braking force can be applied.
[0025]
On the other hand, when the normal operation is performed without operating the valve operating mechanism, the exhaust valve does not open near the compression top dead center. Therefore, there is no problem such as loss of engine output.
[0026]
In this embodiment, as shown in FIG. 1, the cam profile is determined so that the stem pressing portion moves in response to a change in the crank angle. FIG. 3 schematically shows the shape of a cam having such a cam profile.
[0027]
The cam 2 has a convex portion 2A for pushing down an exhaust valve in an exhaust stroke, and a small convex portion 2B formed in a portion corresponding to the vicinity of a compression top dead center. Here, the small convex portion 2B needs to be smaller than the lift amount to be applied to the exhaust valve when the valve operating mechanism operates. If the lift amount is larger than the upper limit, the exhaust valve is opened near the compression top dead center during the normal operation, and the efficiency of the engine is greatly reduced. Further, the cam profile of the cam 2 is such that, except for the convex portion 2A and the small convex portion 2B, the amount of lift applied to the exhaust valve by the amount of lift applied to the exhaust valve when the valve operating mechanism operates during normal operation is equal to that of the rocker arm. A stem pressing portion for pressing the stem is formed so as to be away from a position for pressing the stem of the exhaust valve.
[0028]
In this embodiment, it is preferable that the peak value in the vicinity of the top dead center is within a range of 540 ° ± 10 °. By opening the exhaust valve within this range, the force of the exhaust brake can be further increased.
[0029]
The valve operating mechanism used in the present embodiment is not particularly limited as long as it can provide a predetermined lift amount to the exhaust valve. For example, an apparatus disclosed in JP-A-6-34104 can be mentioned. This mechanism will be briefly described below.
[0030]
First, as shown in FIG. 4, the rotational movement of the cam 2 rotating in synchronization with the crankshaft is converted into the reciprocating movement of the push rod 4 via the valve lifter 3, and the rocker arm 5 swings accordingly. The exhaust valve 1 is opened and closed. Note that the end of the rocker arm 5 on the exhaust valve 1 side is the above-described stem pressing portion 5a.
[0031]
A rocker shaft 6 swingably supports the rocker arm 5, and as shown in FIGS. 5 and 6, arm support shafts 6a and 6b for an exhaust valve and an intake valve are alternately arranged, and the rocker arm 5 is used for an exhaust valve. The arm support shaft 6a is formed eccentric by a predetermined amount with respect to the center X of the shaft rotation.
[0032]
The rocker shaft 6 is rotatably supported by a bearing on the cylinder head side. When the shaft 6 is rotated, the arm support shaft 6a for the exhaust valve is lowered, and the fulcrum of the rocker arm is rotated from Y before rotation as shown in FIG. To Z. Therefore, a predetermined lift amount is provided to the exhaust valve 1. An actuator (not shown) for rotating the rocker shaft 6 within a predetermined angle range is provided.
[0033]
B. Second embodiment
The exhaust brake device according to the second embodiment of the present invention has a valve operating mechanism that can apply a predetermined lift amount to the exhaust valve when the exhaust brake operates,
In the intake, compression, and expansion strokes when the exhaust brake is actuated by the valve operating mechanism, the exhaust valve opens only immediately after the intake stroke, the exhaust valve closes in other regions, and intake, compression, A cam profile for the exhaust valve is formed such that the exhaust valve is closed in all regions of the expansion stroke.
[0034]
FIG. 8 shows the movement of the stem pressing portion for pressing the stem of the exhaust valve of the rocker arm according to the present embodiment, and FIG. 9 shows the movement of the exhaust valve at that time. The solid line indicates a state in which the valve operating mechanism is not operating in the normal operation state, and the broken line indicates a state in which a predetermined lift amount is added to the exhaust valve by the valve operating mechanism.
[0035]
In a state where the valve operating mechanism is not operated, that is, in a normal operation state, the stem pressing portion is located at a minus position, that is, a position separated by a predetermined lift amount from the stem of the exhaust valve in the intake, compression, and expansion strokes. Will do. Then, even at a position exceeding 360 °, that is, immediately after the intake stroke, the stem of the exhaust valve is not pressed down.
[0036]
Then, when the valve operating mechanism is operated, that is, when the exhaust brake device is operated, the stem of the exhaust valve is pressed only at a position exceeding 360 °, that is, immediately after the intake stroke, and the exhaust valve is moved by a predetermined lift amount. open.
[0037]
In this embodiment, by operating the valve operating mechanism in this manner, the exhaust valve can be temporarily opened immediately after the intake stroke, so that the air compressed in the exhaust pipe is introduced into the cylinder. Can be. Therefore, in the subsequent compression stroke, the negative workload can be increased for the engine, and as a result, a strong braking force can be applied.
[0038]
On the other hand, when the normal operation is performed without operating the valve operating mechanism, the exhaust valve does not open immediately after the intake stroke. Therefore, there is no problem such as loss of engine output.
[0039]
In the present embodiment, as shown in FIG. 8, the cam profile is determined so that the stem pressing portion moves, and a small convex portion is formed in a portion immediately after the intake stroke. Here, as in the case of the first embodiment, it is necessary that the small convex portion is smaller than the lift amount applied to the exhaust valve when the valve operating mechanism operates. If the lift amount is larger than that, the exhaust valve is opened immediately after the intake stroke during the normal operation, which significantly reduces the efficiency of the engine.
[0040]
In the present embodiment, the cam profile is adjusted so that the opening of the exhaust valve immediately after the intake stroke is within a range from 10 ° before the intake valve closes to 10 ° after the intake valve closes. Is preferred. By opening the exhaust valve within this range, the force of the exhaust brake can be further increased.
[0041]
Note that the valve operating mechanism in this embodiment is the same as that described in the first embodiment, and a description thereof will be omitted.
[0042]
C. Third embodiment
The exhaust brake device according to the third embodiment of the present invention has a valve operating mechanism that can apply a predetermined lift amount to the exhaust valve when the exhaust brake is operated,
During the intake, compression, and expansion strokes when the exhaust brake is actuated by the valve mechanism, the exhaust valve opens only at the compression top dead center and immediately after the intake stroke, the exhaust valve closes in other areas, and during normal operation. The cam profile for the exhaust valve is formed such that the exhaust valve is closed in all regions of the intake, compression, and expansion strokes.
[0043]
FIG. 10 shows the movement of the stem pressing portion for pressing the stem of the exhaust valve of the rocker arm in the present embodiment, and FIG. 11 shows the movement of the exhaust valve at that time. The solid line indicates a state in which the valve operating mechanism is not operating in the normal operation state, and the broken line indicates a state in which a predetermined lift amount is added to the exhaust valve by the valve operating mechanism.
[0044]
In a state where the valve operating mechanism is not operated, that is, in a normal operation state, the stem pressing portion is located at a minus position, that is, a position separated by a predetermined lift amount from the stem of the exhaust valve in the intake, compression, and expansion strokes. Will do. Further, even at a position exceeding 360 °, that is, immediately after the intake stroke, and near 540 °, that is, near the compression top dead center, the stem of the exhaust valve is not pressed down.
[0045]
Then, in a state in which the valve operating mechanism is operated, that is, in a state in which the exhaust brake device is operated, only at a position exceeding 360 °, that is, immediately after the intake stroke, and near 540 °, that is, only near the compression top dead center, the stem of the exhaust valve. To open the exhaust valve by a predetermined lift amount.
[0046]
In this embodiment, by operating the valve operating mechanism in this manner, the exhaust valve can be temporarily opened immediately after the intake stroke, so that the air compressed in the exhaust pipe is introduced into the cylinder. Can be. Therefore, in the subsequent compression stroke, the negative work load on the engine can be increased. Further, since the exhaust valve can be temporarily opened near the compression top dead center, the compressed air in the cylinder can be released into the exhaust pipe. Therefore, even in the subsequent expansion stroke, it is possible to increase the negative work load on the engine. Therefore, an extremely strong braking force can be applied to the exhaust brake device.
[0047]
On the other hand, when the normal operation is performed without operating the valve operating mechanism, the exhaust valve does not open at the above-mentioned time point, as in the first embodiment and the second embodiment. Therefore, there is no problem such as loss of engine output.
[0048]
In this embodiment, as shown in FIG. 10, the cam profile is determined so that the stem pressing portion moves, and a small convex portion is formed immediately after the intake stroke and in a portion corresponding to the vicinity of the compression top dead center. Here, as in the case of the first embodiment and the second embodiment, the small convex portion needs to be smaller than the lift amount applied to the exhaust valve when the valve operating mechanism operates. If the lift amount is larger than the upper limit, the exhaust valve is opened near the compression top dead center during the normal operation, and the efficiency of the engine is greatly reduced.
[0049]
The opening timing and the like of the exhaust valve in this embodiment are the same as those in the first embodiment and the second embodiment, and thus description thereof will be omitted. Further, the valve operating mechanism in the present embodiment is the same as that described in the above-described first embodiment, and a description thereof will be omitted.
[0050]
D. Fourth embodiment
The exhaust brake device according to the fourth embodiment of the present invention has a valve operating mechanism that can apply a predetermined lift amount to the exhaust valve when the exhaust brake is operated,
In the intake, compression, and expansion strokes when the exhaust brake is actuated by the valve operating mechanism, the exhaust valve opens from immediately after the intake stroke to the compression top dead center, and in other regions the exhaust valve closes, and during normal operation, A cam profile for the exhaust valve is formed so that the exhaust valve is closed in all regions of the intake, compression, and expansion strokes.
[0051]
FIG. 12 shows the movement of the stem pressing portion for pressing the stem of the exhaust valve of the rocker arm in the present embodiment, and FIG. 13 shows the movement of the exhaust valve at that time. The solid line indicates a state in which the valve operating mechanism is not operating in the normal operation state, and the broken line indicates a state in which a predetermined lift amount is added to the exhaust valve by the valve operating mechanism.
[0052]
In a state where the valve operating mechanism is not operated, that is, in a normal operation state, the stem pressing portion is located at a minus position, that is, a position separated by a predetermined lift amount from the stem of the exhaust valve in the intake, compression, and expansion strokes. Will do. Further, even at a position exceeding 360 °, that is, in a region from immediately after the intake stroke to around 540 °, that is, a region near the compression top dead center, the stem of the exhaust valve is not pressed down.
[0053]
Then, when the valve operating mechanism is operated, that is, when the exhaust brake device is operated, the stem of the exhaust valve is pressed to a position exceeding 360 °, that is, to the vicinity of 540 ° immediately after the intake stroke, that is, to the vicinity of the compression top dead center. Then, the exhaust valve is opened by a predetermined lift amount.
[0054]
In this embodiment, by operating the valve operating mechanism in this manner, the exhaust valve can be opened from immediately after the intake stroke to the vicinity of the compression top dead center. Can be introduced within. Therefore, in the subsequent compression stroke, the negative work load on the engine can be increased. Then, by closing the exhaust valve near the compression top dead center, negative work can be performed in the subsequent expansion stroke. Therefore, an extremely strong braking force can be applied to the exhaust brake device.
[0055]
Further, according to this method, at the compression top dead center where the pressure in the cylinder is extremely high, the operation of opening the exhaust valve with the lift amount secured by the valve mechanism is not performed. Therefore, it is not necessary to provide various mechanisms required for opening the exhaust valve under such extremely high pressure in the valve operating mechanism. Therefore, it is possible to make the valve operating mechanism a simple mechanism, and cost reduction can be achieved.
[0056]
On the other hand, when the normal operation is performed without operating the valve operating mechanism, the exhaust valve does not open at the above-mentioned time point, as in the first embodiment and the second embodiment. Therefore, there is no problem such as loss of engine output.
[0057]
In the present embodiment, the cam profile is determined so that the stem pressing portion moves as shown in FIG. . Here, as in the case of the first embodiment and the second embodiment, the convex portion needs to be smaller than the lift amount applied to the exhaust valve when the valve operating mechanism operates. If the lift amount is larger than that, during normal operation, the exhaust valve opens near the compression top dead center, greatly reducing the efficiency of the engine.
[0058]
The opening timing of the exhaust valve in the present embodiment is the same as that in the second embodiment, and a description thereof will be omitted. On the other hand, with regard to the closing timing of the exhaust valve in the present embodiment, it is preferable that the cam profile is formed so that the exhaust valve closes near the top dead center, that is, within the range of 540 ° ± 45 °. By setting the timing at which the exhaust valve closes within the above range, the balance between the exhaust braking force and the load applied to the valve system can be balanced, and the valve system can be balanced with the effect on the valve reinforcement cost. Further, since the optimum and effective valve timing differs depending on the engine speed, it is desirable to select within the above range.
[0059]
Further, the valve operating mechanism in the present embodiment is the same as that described in the above-described first embodiment, and a description thereof will be omitted.
[0060]
Note that the present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and has substantially the same configuration as the technical idea described in the claims of the present specification, and those having the same effects are provided by the present invention. It is included in the technical scope of the invention.
[0061]
【The invention's effect】
As described above, in the present invention, by applying a predetermined lift amount to the exhaust valve by the valve operating mechanism, the exhaust valve is opened only at the compression top dead center in the intake, compression, and expansion strokes during the operation of the exhaust brake. Thus, a cam profile is formed. Therefore, at this time, since the air in the cylinder flows into the exhaust pipe, the pressure in the cylinder can be reduced, so that the negative work of the engine during the expansion stroke can be increased, and as a result, the braking force can be reduced. Can be increased. Further, in a state where a predetermined lift amount is not applied to the exhaust valve by the valve operating mechanism, that is, in a normal operation state, since the cam profile is designed so that the exhaust valve does not open at the compression top dead center, Efficiency does not decrease during normal operation.
[Brief description of the drawings]
FIG. 1 is a graph showing a relationship between a position of a stem pressing portion and a crank angle in a first embodiment of the present invention.
FIG. 2 is a graph showing a relationship between a position of an exhaust valve and a crank angle according to the first embodiment of the present invention.
FIG. 3 is a schematic plan view showing a cam profile in the first embodiment of the present invention.
FIG. 4 is an explanatory diagram showing an example of a valve operating mechanism used in the present invention.
FIG. 5 is a schematic plan view showing an example of a rocker shaft used in the present invention.
6 is a view as viewed in the direction of arrow A in FIG. 5;
FIG. 7 is an operation explanatory view of a rocker shaft.
FIG. 8 is a graph showing a relationship between a position of a stem pressing portion and a crank angle in a second embodiment of the present invention.
FIG. 9 is a graph showing a relationship between a position of an exhaust valve and a crank angle in a second embodiment of the present invention.
FIG. 10 is a graph showing a relationship between a position of a stem pressing portion and a crank angle in a third embodiment of the present invention.
FIG. 11 is a graph showing a relationship between a position of an exhaust valve and a crank angle according to a third embodiment of the present invention.
FIG. 12 is a graph showing a relationship between a position of a stem pressing portion and a crank angle in a fourth embodiment of the present invention.
FIG. 13 is a graph showing a relationship between a position of an exhaust valve and a crank angle according to a fourth embodiment of the present invention.
[Explanation of symbols]
1 ... exhaust valve
2 ... cam
4 ... Bush rod
5 ... Rocker arm
5a: Stem pressing part
6 ... Rocker shaft

Claims (8)

When the exhaust brake is activated, it has a valve operating mechanism that can apply a predetermined lift amount to the exhaust valve,
In the intake, compression, and expansion strokes when the exhaust brake is actuated by the valve mechanism, the exhaust valve opens only at the compression top dead center, the exhaust valve closes in other areas, and intake and compression during normal operation. And a cam profile for the exhaust valve such that the exhaust valve is closed in all regions of the expansion stroke. When the exhaust brake is activated, it has a valve operating mechanism that can apply a predetermined lift amount to the exhaust valve,
In the intake, compression, and expansion strokes when the exhaust brake is actuated by the valve mechanism, the exhaust valve opens only immediately after the intake stroke, the exhaust valve closes in other regions, and intake, compression, An exhaust brake device characterized in that a cam profile for the exhaust valve is formed such that the exhaust valve is closed in all regions of the expansion stroke. When the exhaust brake is activated, it has a valve operating mechanism that can apply a predetermined lift amount to the exhaust valve,
In the intake, compression, and expansion strokes when the exhaust brake is actuated by the valve mechanism, the exhaust valve opens only immediately after the compression top dead center and immediately after the intake stroke, the exhaust valve closes in other regions, and during normal operation. An exhaust valve device characterized in that an exhaust valve cam profile is formed such that the exhaust valve is closed in all regions of the intake, compression, and expansion strokes. When the exhaust brake is activated, it has a valve operating mechanism that can apply a predetermined lift amount to the exhaust valve,
In the intake, compression, and expansion strokes when the exhaust brake is actuated by the valve mechanism, the exhaust valve opens from immediately after the intake stroke to the compression top dead center, and in other regions the exhaust valve closes, and during normal operation, An exhaust brake device, wherein a cam profile for an exhaust valve is formed such that the exhaust valve is closed in all regions of the intake, compression, and expansion strokes. 4. The exhaust brake device according to claim 1, wherein a cam profile is formed such that when the exhaust valve opens at the compression top dead center, the peak is 540 ° ± 10 °. 5. The cam profile is formed such that when the exhaust valve opens from immediately after the intake stroke to the compression top dead center, the exhaust valve closes within a range of 540 ° ± 45 °. An exhaust brake device according to item 1. The cam profile is formed such that when the exhaust valve is opened immediately after the intake stroke, the opening of the exhaust valve is within a range from 10 ° before the intake valve closes to 10 ° after the intake valve closes. The exhaust brake device according to claim 2, 3, 4, or 6, wherein: A valve operating mechanism for supporting the rocker arm of the exhaust valve on the eccentric portion of the rocker shaft and lowering the rocker arm of the eccentric portion by rotating the rocker shaft, thereby applying a predetermined lift amount to the exhaust valve. The exhaust brake device according to any one of claims 1 to 7, wherein:

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