Valve disabling mechanism for an internal combustion engine

Abstract

 A valve disabling mechanism, which may be employed in internal combustion engines having a retarding mode of the compression-release type additionally to the normal powering mode, includes a tubular adjusting screw (310) affixed to a valve train mechanism (50), a tubular drive pin (324) coaxially disposed within the tubular screw (310) having radial ports (334) and an actuator pin (348) disposed in the tubular drive pin (324) and reciprocated in the drive pin. Locking balls (362) are disposed within the radial ports (334), which are moveable to engage the tubular driven screw (310) and the tubular drive pin (324) for conjoint movement in the normal powering mode and to disengage the tubular screw from the tubular drive pin to permit a reciprocating motion of the tubular screw relative to the tubular drive pin in order to disable or modify the normal motion of the exhaust valves in the retarding mode.

Description

[0001] This invention relates to a valve disabling mechanism employed in internal combustion engines which may be switched from the normal powering mode to a retarding mode of the compression-release type.

[0002] In internal combustion engines which may be switched from a powering mode to a retarding mode of the compression release-type, the normal motion of at least one exhaust valve has to be substituted by a modified valve motion. An improved engine retarding method of the named type with an advantageous valve motion in the retarding mode has been disclosed in the European Patent Application 86 107 117.3 which is the parent application to this divisional application.

[0003] While known engine retarding methods of the compression release type (eg. US-PS 32 20 392) merely provide an additional exhaust valve opening event at the end of the stroke corresponding to the compression stroke in the powering mode, said additional opening event not interfering with the normal exhaust valve motion, in an improved engine retarding method according to the parent application to this application (EP-A 0 211 170) the normal valve motion has to be modified in the retarding mode.

[0004] Thus it is necessary to disable the exhaust valves from the opening at the time they would normally open during the positive power mode of engine operation. Two mechanisms which accomplish this result are disclosed in U.S. Patent 4 572 114 which is owned by the assignee of the present invention. One of these mechanisms involves a modification of the exhaust valve crosshead to temporarily prevent its actuation by a rocker arm while enabling actuation by the slave piston. The other mechanism involves a modification of the rocker arm wherein the portion of the rocker arm which contacts the crosshead is temporarily disconnected from the portion of the rocker arm actuated by a pushtube.

[0005] A further alternative way to disable the exhaust valve is to provide an eccentric bushing in the rocker arm pivot so as to raise the pivot or fulcrum and thereby introduce a lost motion in the valve train. Such a device is shown, for example in U.S. Patent 3 367 312. As noted above, other lost motion mechanisms may also be used; see for example U.S. Patent 3 786 792.

[0006] A further device for disabling the normal valve motion is known from EP-A 0 037 269 which concerns engine cylinder cutout systems in which for the cutout cylinders the exhaust valves are kept open while the intake valves are kept closed. The disengageability of the intake valve train is accomplished by a two-part pushtube, the two parts being telescopically slidable with respect to each other and having locking means to prevent telescopic sliding in the normal powering mode of the engine. The locking means are controlled by means of a hydraulically actuated piston accommodated between the outer portion of the two-part pushtube and a housing. A very high accuracy is necessary in the production of this assembly, since three separate chambers for control-fluid are required for operation. The high-precision production, however, result in high production cost.

[0007] It is the object of this invention to provide a reliable and simple mechanism for disabling the normal valve motion which may be incorporated into the valve pushtube, the rocker arm adjusting screw, rocker arm or rocker arm shaft.

[0008] According to the present invention this problem is solved by a valve disabling mechanism for an internal combustion engine having a valve train mechanism, characterized by tubular driven means affixed to the valve train mechanism and having first and second shoulder means, tubular drive pin means coaxially disposed within the tubular driven means and communicating at one end with the valve train mechanism, the tubular drive pin means having third and fourth shoulder means and a plurality of transverse radial ports, actuating pin means coaxially disposed within the tubular drive pin means and adapted to reciprocate between first and second positions within the tubular drive pin means, the actuating pin means having fifth and sixth shoulder means, first biasing means interposed between the actuating pin means and the tubular drive pin means and adapted to bias the drive pin means towards said first position, second biasing means disposed between the second and third shoulder means, and locking means loosely disposed within the transverse radial ports and being moveable between a first position in engagement with the first shoulder for conjoint movement of the tubular driven means and the tubular drive pin means and a second position in engagement with the fifth shoulder for enabling reciprocating motion of the tubular driven means relative to the tubular drive pin means.

[0009] Further objects and advantages of the invention will become apparent from the following detailed description of the invention and the accompanying drawings in which:

Fig. 1A is a cross-sectional view of a mechanism for disabling the exhaust valve for an internal combustion engine with separate crossheads and slave pistons and showing the mechanism in the positive powering mode.

Fig. 1B is a cross-sectional view of the mechanism of Fig. 1A in the retarding mode of operation.

Fig. 2A is a cross-sectional view of a mechanism for delaying the opening of the intake valve and showing the mechanism in the positive powering mode.

Fig. 2B is a cross-sectional view of the mechanism of Fig. 2A in the retarding mode of operation.

[0010] A valve disabling mechanism in accordance with the invention shown in Fig. 1A and 1B comprises a tubular adjusting screw 310. Fig. 1A shows the valve disabling mechanism during the powering mode of engine operation wherein it performs the function of the adjusting screw of the rocker arm. Fig. 1B shows the same mechanism during the retarding mode of engine operation wherein it disables the rocker arm 50 and, therefore, the exhaust valves.

[0011] Point 308 represents the point about which rocker arm 50 pivots when actuated by a pushtube 52. The tubular adjusting screw 310 which replaces the solid adjusting screw is locked in its adjusted position by a locknut 312. The tubular adjusting screw 310 is provided with three concentric bores. A large bore 314 extends a short distance from the pushtube end of the adjusting screw 310. An intermediate bore 316 extends from the large bore 314 substantially to the top of the adjusting screw 310. A small bore 318 extends through the top of the adjusting screw 310. A sloping shoulder 320 is formed between the large bore 314 and the intermediate bore 316 while a horizontal shoulder 322 is formed between the intermediate bore 316 and the small bore 318.

[0012] A drive pin 324 is positioned within the adjusting screw 310. The maximum diameter of the drive pin 324 is slightly less than the diameter of the intermediate bore 316 to permit reciprocation of the drive pin 324 relative to the adjusting screw 310. One end of the drive pin 324 is adapted to mate with, and be driven by, the pushtube 52. A snap ring 326 limits the downward (as shown in Figs. 1A and 1B) movement of the drive pin 324 relative to the adjusting screw 310. The upper portion of the drive pin 324 has an outside diameter 328 which is slightly smaller than the small bore 318 of the adjusting screw 310 so as to permit relative reciprocation of the drive pin 324 and adjusting screw 310. A shoulder 330 is defined by the diameter 328 of the upper portion of the drive pin 324 and the maximum diameter of the drive pin. A compression spring 332 is located within the adjusting screw 310 between shoulders 322 and 330 so as to bias the drive pin 324 downwardly (as shown in Figs. 1A and 1B) relative to the adjusting screw 310. A plurality of ports 334 are disposed around the circumference of the drive pin 324 in the region of its largest diameter. The ports 334 are directed angularly downwardly (as shown in Figs. 1A and 1B) from the outside of the drive pin 324 toward the axis of the drive pin. A stepped cavity 336 is formed within the drive pin 324. The largest diameter 338 of the stepped cavity 336 communicates at its upper region with the plurality of ports 334, and with an intermediate diameter 340 through a sloping shoulder 342. The intermediate diameter 340 terminates at a shoulder 344 while a smaller diameter section 346 extends from the shoulder 344 through the top of the drive pin 324.

[0013] A stepped actuator pin 348 is mounted for reciprocating motion with respect to the drive pin 324 and includes a large diameter section 350, an intermediate diameter section 352 and a small diameter section 354. A sloping shoulder 356 joins the larger diameter section 350 and the intermediate diameter section 352 while a horizontal shoulder 358 is located between the intermediate and small diameter sections of the actuator pin 348. When the actuator pin 348 is in its uppermost position (as shown in Fig. 1A) the horizontal shoulder 358 in the actuator pin abuts the shoulder 344 of the drive pin 324 and the small diameter section 354 of the actuator pin 348 extends beyond the upper end of the drive pin 324. The actuator pin 348 is biased toward its uppermost position by a compression spring 360 located within the cavity 336. A ball 362 is located in each of the ports 334. The balls 362 are larger in diameter than the wall thickness of the drive pin 324 in the region of the ports 334 so that when the actuator pin 348 is in its uppermost position (as shown in Fig. 1B) the balls 362 extend outside the drive pin 324 and engage the shoulder 320 of the adjusting screw 310. However, whenever the actuator pin 348 is depressed as shown in Fig. 1B, the sloping shoulder 320 cams the balls 362 inwardly so that the balls 362 rest, at least partially, on the sloping shoulder 356 of the actuator pin 348. In this position (Fig. 1B), the balls 362 clear the shoulder 320 and the adjusting screw 310 is free to reciprocate with respect to the drive pin 324 so that no movement is imparted to pushtube 52.

[0014] Point 364 (Fig. 1B) represents the maximum upward excursion of the drive pin 324 as a result of the upward movement of the exhaust valve pushtube 52. The distance 366 (Fig. 1B) represents a clearance (which should be a minimum of about 0.100˝) between point 364 and the rest position of the master piston 66˝ (or 224 shown in Fig. 2A).

[0015] The master piston 66˝ (or 224) is biased toward its rest position by the leaf spring 120˝ (or 236 shown in Figs. 2A and 2B). Whenever the engine retarder is turned on, the hydraulic circuit will be pressurized by the low pressure pump and the master piston 66˝ will be driven downwardly (as viewed in Figs. 1A and 1B) until it contacts the end of the drive pin.324 against the bias of leaf spring 120˝ and compression spring 360. Under these conditions, the motion of the pushtube 52 will be transmitted through the drive pin 324 to the master piston 66˝ but the rocker arm 50 will remain at rest since the drive pin 324 will be disengaged from the adjusting screw 310. However, the bias of compression spring 332 will maintain the rocker arm 50 in contact with the exhaust valve crosshead (not shown). It will be seen, therefore, that the exhaust valves are automatically disabled by the mechanism of Fig. 1A and 1B whenever the engine retarder is switched on.

[0016] Figs. 2A and 2B illustrate a mechanism which is very similar to the mechanism shown in Figs. 1A and 1B but which is designed to delay but not entirely disable the motion of the intake valve. For purposes of clarity and brevity, parts which are common to both mechanisms carry the same designators. It will be understood, however, that the rocker arm 232 is an intake valve rocker arm, the pushtube 228 is an intake valve pushtube and the master piston 224 is located in alignment with the intake valve pushtube 228 within a master cylinder 226 located in the retarder housing.

[0017] The only significant difference in the mechanisms shown in Figs. 2A and 2B over the mechanisms shown in Figs. 1A and 1B is that an extra step is provided between the intermediate bore 316 and the small bore 318 so as to form a shoulder 364 between the intermediate bore 316 and an intervening bore 366. The diameter of the intervening bore 366 is smaller than the maximum diameter 328 of the drive pin 324. The distance 368 between shoulders 330 and 364 is directly proportional to the delay introduced into the motion of the rocker arm and valve associated therewith. It will be appreciated that any desired delay may be built into the mechanism. When the distance 368 is equal to or greater than the travel of the pushtube 228, the mechanism of Figs. 2A and 2B will function exactly like the mechanism of Figs. 1A and 1B.

[0018] Although the mechanism of Figs. 2A and 2B is intended principally to provide the intake valve delay, it will be appreciated that this mechanism may be used whenever a delay in the intake or exhaust valve motion is required. Similarly, the mechanism of Figs. 1A and 1B may be used whenever the intake or exhaust valves are required to be disabled.

[0019] The terms and expressions which have been employed are used as terms of description and not of limitation and there is no intention in the use of such terms and expressions of excluding any equivalent of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed.

Claims

1. A valve disabling mechanism for an internal combustion engine having a valve train mechanism, characterized by tubular driven means (310) affixed to the valve train mechanism (50) and having first - (320) and second (322) shoulder means, tubular drive pin means (324) coaxially disposed within said tubular driven means and communicating at one end with said valve train mechanism, said tubular drive pin means having third (330) and fourth (342) shoulder means and a plurality of transverse radial ports (334), actuating pin means (348) coaxially disposed within said tubular drive pin means and adapted to reciprocate between first and second positions within said tubular drive pin means, said actuating pin means having fifth (356) and sixth shoulder means (358), first biasing means (360) interposed between said actuating pin means (348) and said tubular drive pin means (324) and adapted to bias said drive pin means towards said first position, second biasing means (332) disposed between said second (322) and third (330) shoulder means, and locking means (362) loosely disposed within said transverse radial ports and being moveable between a first position in engagement with said first shoulder means for conjoint movement of said tubular driven means and said tubular drive pin means (324) and a second position in engagement with said fifth shoulder means for enabling reciprocating motion of said tubular driven means relative to said tubular drive pin means.

2. The mechanism of claim 1, characterized in that said tubular driven means includes a seventh shoulder means (364) intermediate said first (320) and second (322) shoulder means engageable with said third shoulder means (330).

3. The mechanism of claim 1 or 2, characterized in that said tubular driven means is adjustable with respect to said valve train mechanism.

4. The mechanism of claim 1 or 2, characterized in that said first (320) and fifth (356) shoulder means are sloped in a direction to cam said locking means away from whichever one of said first and fifth shoulder means said locking means may be in engagement with.

Drawing