JP2014105584A - Compression pressure release type engine brake - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compression pressure release type engine brake in which a service life does not decrease even without making operation delay large.SOLUTION: In a compression pressure release type engine brake in which a master piston 15 is actuated in a valve opening oil flow passage 14, in which oil flows, to apply pressure to the oil, and a sleeve piston 16 is actuated by the pressure of the oil to open an exhaust valve 4, the valve opening oil flow passage 14 is connected to an oil supply flow passage 13 in which oil is supplied through an electromagnetic valve 17. The valve opening oil flow passage 14 and the oil supply flow passage 13 are connected with an oil release flow passage 23. In the oil release flow passage 23, a release valve 24 is disposed.

Description

  The present invention relates to a compression pressure release type engine brake that is a kind of engine brake using a compression stroke of a cylinder of a diesel engine.

A vehicle having a large weight difference between empty and loaded requires a large braking force when loaded. For this reason, the above-mentioned vehicle is equipped with a compression pressure release type engine brake as an auxiliary. In this compression pressure release type engine brake, a braking force is generated when a predetermined time elapses after the accelerator is turned off.
Specifically, the exhaust valve is forcibly opened near the compression top dead center of the engine to release the compression pressure, thereby reducing the generation of the force that pushes down the piston in the next expansion stroke. Effective braking force.

  FIG. 3 is a cross-sectional view schematically showing an example of a conventional compression pressure release type engine brake. In FIG. 3, 1 is a cylinder, 2 is a combustion chamber, 3 is a piston, 4 is an exhaust valve, 5 is an intake passage, and 6 is an exhaust passage. In the exhaust process, the rocker arm 8 swings with the base end pushed up by the exhaust cam 7 via the roller 8a. When the rocker arm 8 swings, the tip of the rocker arm 8 pushes down both the exhaust valves 4 via the valve bridge 10 to open the rocker arm 8. When the exhaust valve 4 is opened, exhaust gas is scavenged from the combustion chamber 2 to the exhaust passage 6 in the cylinder 1.

  Here, a hydraulic unit 11 is disposed above the cylinder 1. The hydraulic unit 11 has an oil passage 12 through which oil flows. The oil passage 12 includes an oil supply passage 13 into which oil is fed and a valve opening oil passage 14 that serves as a passage for opening the exhaust valve 4.

  The oil supply passage 13 includes a passage 13a through which oil is sent from an oil pump (not shown), a passage 13b through which oil is sent to an actuator (not shown), and a passage 13c connected to the valve opening oil passage 14. doing. The valve opening oil passage 14 has a passage into which the master piston 15 is inserted so as to be able to advance and retreat, a passage into which the slave piston 16 is inserted so as to be able to advance and retract, and a passage connected to the oil supply passage 13. doing.

  An electromagnetic valve (valve) 17 is disposed between the oil supply passage 13 and the valve opening oil passage 14. The electromagnetic valve 17 is opened and closed by a control signal 18 a from an ECU (engine control unit) 18 to supply or shut off oil from the oil supply passage 13 to the valve opening oil passage 14. The electromagnetic valve 17 holds the hydraulic pressure of the valve opening oil passage 14 when closed, and releases the hydraulic pressure of the valve opening oil passage 14 when opened.

  When the ECU 18 receives the signal indicating that the accelerator has been turned off and the predetermined time has elapsed, the ECU 18 operates the compression pressure release type engine brake. The ECU 18 controls the cam 20 at the timing when the piston 3 is positioned at the compression top dead center, and pushes up the base end of the rocker arm 21 via the roller 21a to swing it. When the base end is pushed up, the rocker arm 21 swings so that the tip pushes the master piston 15. When the master piston 15 is pushed, it is pushed into the valve opening oil passage 14 and applies pressure to the oil inside the valve opening oil passage 14. The oil given pressure moves the slave piston 16, opens the exhaust valve 4 via the actuator pin 22, and releases the compressed air in the cylinder 1. When the piston 3 passes through the compression top dead center, the exhaust valve 4 is closed by operating the cam 20 for the compression pressure release type engine brake.

  As prior art document information related to this type of compression pressure release type engine brake, for example, there is the following Patent Document 1.

JP 7-42520 A

  Here, the operation of the above-described compression pressure release type engine brake is intentionally further delayed after a predetermined time has elapsed since the accelerator was turned off. This is because when the compression pressure release type engine brake is operated immediately after the full load operation, the internal pressure of the cylinder 1 is very high even after the accelerator is turned off and a predetermined time elapses. When the valve 4 is opened, the hydraulic pressure of the valve opening oil passage 14 momentarily exceeds the pressure limit L of the valve opening oil passage 14, thereby shortening the life of the valve opening oil passage 14. This is because the life of the compression pressure release type engine brake may be shortened.

  With reference to FIG. 4 (A), how the pressure in the valve opening oil passage 14 instantaneously exceeds the pressure limit L will be described. FIG. 4A is a diagram showing the relationship between time (sec), braking force (Nm), and hydraulic pressure (MPa) of the valve opening oil passage 14.

  As shown in FIG. 4A, when the accelerator is turned off at time a in the graph, a braking force is generated by an engine brake or the like. Then, after a predetermined time has elapsed since the accelerator was turned off, the ECU 18 operates the compression pressure release type engine brake with an operation delay D. As shown in FIG. 4A, after the compression pressure release type engine brake is operated, the hydraulic pressure in the valve opening oil passage 14 instantaneously exceeds the pressure limit L of the valve opening oil passage 14 twice. Yes.

  Therefore, after the accelerator is turned off and a predetermined time elapses, it is conceivable that the compression pressure release type engine brake is operated after ensuring a longer operation delay than in the case shown in FIG. In this case, since the engine is sufficiently cooled and the internal pressure of the cylinder 1 is lowered, it is possible to prevent the hydraulic pressure from exceeding the pressure limit L of the valve opening oil passage 14.

  With reference to FIG. 4 (B), a state in which the hydraulic pressure in the valve opening oil passage 14 is prevented from exceeding the pressure resistance limit L by securing a longer operation delay D ′ will be described. FIG. 4B is a diagram showing the relationship between time (sec), braking force (Nm), and hydraulic pressure (MPa) of the valve opening oil passage 14.

  As shown in FIG. 4 (B), when the operation delay D ′ is set longer than that in the case of FIG. 4 (A), the hydraulic pressure in the valve opening oil passage 14 is instantaneous after the compression pressure release type engine brake is operated. Therefore, it is possible to prevent the pressure limit L of the valve opening oil passage 14 from being exceeded.

  However, if the operation delay D ′ is set large, the braking force of the compression pressure release type engine brake acts with a delay, leading to a decrease in performance of the compression pressure release type engine brake. Of course, the compression pressure release type engine brake is preferably operated as soon as possible after the accelerator is turned off and a predetermined time elapses.

  Therefore, in view of such circumstances, the present invention intends to provide a compression pressure release type engine brake that does not cause a decrease in life even if a large operation delay is not taken.

  The present invention relates to a compression pressure release type engine brake that operates a master piston in a valve opening oil passage through which oil flows to apply pressure to the oil, and operates a slave piston by the oil pressure to open an exhaust valve. is there. A relief valve for releasing the hydraulic pressure of the valve opening oil passage is provided so as not to exceed the pressure resistance limit of the valve opening oil passage.

  The valve opening oil passage is connected to an oil supply passage through which oil is supplied via a valve. And it is preferable that the said relief valve is arrange | positioned in the relief oil flow path which connects the said valve opening oil flow path and the said oil supply flow path.

  According to the compression pressure release type engine brake of the present invention, it is possible to prevent a decrease in the life without taking a large operation delay.

It is sectional drawing which showed typically an example of the compression pressure release type engine brake which concerns on this invention. It is the graph which showed the hydraulic pressure which generate | occur | produces in the flow path for valve opening of the compression pressure release type engine brake which concerns on this invention. It is sectional drawing which showed the conventional compression pressure release type engine brake typically. (A) is the graph which showed the hydraulic pressure which generate | occur | produces in the flow path for valve opening, when shortening the operation delay of a compression pressure release type engine brake. (B) is the figure which showed the hydraulic pressure which generate | occur | produces in the flow path for valve opening, when extending the operation delay of a compression pressure release type engine brake.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 3 denote the same components, and the basic configuration is the same as that of the conventional one shown in FIG. It is. As shown in FIG. 1, the feature of this illustrated example is that a relief oil passage 23 for connecting the valve opening oil passage 14 and the oil supply passage 13 is provided, and the relief oil passage 23 is provided with a relief valve. 24 is provided.

  The compression pressure release type engine brake according to the present invention includes an oil passage 12 through which oil flows. The oil passage 12 includes an oil supply passage 13 into which oil is fed, a valve opening passage 14 serving as a passage for opening the exhaust valve 4, a valve opening passage 14, and an oil supply passage 13. And a relief oil passage 23 connecting the two. The relief oil passage 23 is provided with a relief valve 24 for releasing the hydraulic pressure of the valve opening oil passage 14 so as not to exceed the pressure limit L of the valve opening oil passage 14.

  Here, the relief oil passage 23 may be omitted. In this case, a relief valve 24 is disposed in the valve opening oil passage 14. The released oil is configured to be ejected into the cylinder head. The relief valve 24 is, for example, a spring type. The relief valve 24 is not limited to this as long as the hydraulic pressure is allowed to escape so as not to exceed the pressure resistance limit L of the valve opening oil passage 14. For example, an electromagnetic relief valve may be used.

  With reference to FIG. 2, a description will be given of how the hydraulic pressure generated in the valve opening flow path 14 of the compression pressure release type engine brake according to the present invention acts so as not to exceed the pressure limit L by the relief valve 24. FIG. 2 is a diagram showing the relationship between time (sec), braking force (Nm), and hydraulic pressure (MPa) of the valve opening oil passage 14 in the compression pressure release type engine brake according to the present invention.

  In the compression pressure release type engine brake according to the present invention, the operation delay D is set to the same time as shown in FIG. Further, the pressure limit of the valve opening oil passage 14 is indicated by L, and the relief pressure of the relief valve 24 is indicated by R. That is, the relief valve 24 is set to release the hydraulic pressure when the hydraulic pressure exceeds R.

  As shown in FIG. 2, in the graph, the accelerator is turned off at a, and after a predetermined time has elapsed, the compression pressure release type engine brake is operated with an operation delay D. After the compression pressure release type engine brake is operated, a hydraulic pressure exceeding the pressure limit L is instantaneously generated in the valve opening oil passage 14. In FIG. 4A under the same conditions, a hydraulic pressure that exceeds the pressure resistance limit L is momentarily generated twice. However, since the hydraulic pressure is released from the relief valve 24, the compression pressure release type engine brake according to the present invention can prevent the hydraulic pressure exceeding the pressure limit L from being generated in the valve opening oil passage 14. For this reason, the lifetime reduction of the compression pressure release type engine brake can be suppressed. The oil released from the relief valve 24 flows through the relief oil passage 23 and into the oil supply passage 13 having a low pressure.

  Further, as shown in FIG. 4B, in order to prevent the hydraulic pressure from exceeding the pressure limit L by taking a long operation delay, the operation delay time D 'is required. However, in the compression pressure release type engine brake according to the present invention, the operation delay time is D, and the valve opening oil flow path 14 is shorter by about one third than the case of FIG. 4B. It is possible to prevent hydraulic pressure exceeding the pressure limit L from being generated.

  As described above, according to the compression pressure release type engine brake according to the present embodiment, it is possible to prevent a reduction in the life of the compression pressure release type engine brake without taking a large operation delay. Further, the released oil is returned to the oil supply passage 13 through the escape oil passage 23, which is economical.

  It should be noted that the compression pressure release type engine brake of the present invention is not limited to the above-described embodiment, and it is needless to say that various changes can be made without departing from the gist of the present invention.

4 Exhaust valve 13 Oil supply passage 14 Valve opening oil passage 15 Master piston 16 Slave piston 17 Solenoid valve (valve)
23 Relief oil flow path 24 Relief valve L Pressure resistance limit

Claims (2)

A compression pressure release type engine brake that operates a master piston in a valve opening oil passage through which oil flows to apply pressure to the oil, and operates a slave piston by the pressure of the oil to open an exhaust valve,
A compression pressure release type engine brake comprising a relief valve for releasing the hydraulic pressure of the valve opening oil passage so as not to exceed a pressure resistance limit of the valve opening oil passage. The valve opening oil passage is connected to an oil supply passage through which oil is supplied via a valve,
2. The compression pressure release type engine brake according to claim 1, wherein the relief valve is disposed in a relief oil passage that connects the valve opening oil passage and the oil supply passage. 3.

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