DISENGAGEABLE VALVE DRIVE MEANS

Abstract: A disengageable valve drive means which may be employed in internal combustion engines having a retarding mode of the compression-release type additionally to the normal powering mode consists of at least two tubular members (258,288) which are engaged to each other in the normal powering mode and which are disengaged in the retarding mode so that the inner tubular member (280) may slide in the other tubular member (258) in order to disable or modify the normal valve motion. The disengageable valve drive means may be incorporated into the valve pushtube, the rocker arm adjustings crew, rocker arm, rocker arm shaft or crosshead.

Description: This invention relates to a unitary slave piston and crosshead mechanism which is employed to modify a motion of exhaust valves in internal combustion engines which may be switched from the normal powering mode to a retarding mode of the compression-release type. 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. 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. 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. 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 fulcrunm 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. 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 cylin­ ders 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 push­ tube, the two parts being telescopically sidable with respect to each other and having locking means to pre­ vent telescopic sliding in the normal powering mode of the engine. The locking means are controlled by means of a hydraulically actuated piston accomodated 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. 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, rocker arm shaft or crosshead. According to the present invention this problem is solved by a unitary and crosshead mechanism for internal combustion engine equipped with a compression release engine retarder, comprising crosshead means characterized in that the crosshead means is integrally formed with slave piston means adapted to reciprocate within a slave cylinder formed in the compression release retarder, and in that the slave piston and crosshead mechanism comprises an internal bore formed in the crosshead means and the slave piston means, a first circumferential raceway formed in the internal bore, a plurality of first transverse radial ports, and first transverse windows communicating between the bore and the outer surface of the integral slave piston means, tubular slider means positioned within the internal bore for reciprocating movement therein, second transverse window means in the slider means adapted to register with the first transverse windows, contact means associated with a first end of the slider means, a plurality of second transverse radial ports and a transverse wall formed adjacent the end of the tubular slider means, retainer means located within the first and second transverse windows and affixed to the slave cylinder, biasing means positioned between the retainer means and a first side of the transverse wall, piston means positioned for reciprocation within the tubular slider means in the region between the transverse wall and the second end of the tubular slider means, the piston means having a second circumferential raceway formed thereon, biasing means adapted to bias the piston away from the transverse wall, and locking means loosely located in the radial ports of the tubular slider means and adapted in their locking mode to register with the first circumferential raceway, whereby the tubular slider means is locked to the crosshead means, and in their unlocked mode to register with the second circumferential raceway to permit the tubular slider means to reciprocate within the internal bore of the crosshead. 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 combined slave piston and cross-head mechanism capable of disabling the exhaust valve and showing the mechanism in the positive powering mode. Fig. 1B is a cross-sectional view of the mechanism of Fig. 1 in the retarding mode of operation. A mechanism in accordance with the invention for disabling the exhaust valves is shown in Figs. 1A and 1B which comprises a unitary slave piston and crosshead 258. The unitary slave piston and crosshead 258 is mounted for reciprocating motion in the slave cylinder 104. The slave piston portion is generally tubular in shape but open at the lower end which comprises the crosshead portion. For convenience of lubrication, a series of annular grooves 260 may be formed in the circumferential surface of the slave piston portion of the unitary slave piston and crosshead 258. A circumferential annular channel 262 may also be formed in the slave cylinder 104 which communicates with a lubricating oil duct 264 and the low pressure oil supply duct. A series of radial ports 266 is formed through the skirt of the slave piston portion of the unitary structure 258 near the head of the piston portion When the unitary structure 258 is in its rest. position against the adjustable stop 110, the radial ports 266 register with a circumferential channel 268 that communicates through duct 270 with the low pressure feed duct for the control valve. A circum­ ferential raceway 272 is formed on the inner surface of the slave piston portion of the unitary slave piston and crosshead 258 adjacent the radial ports 266. Win­ dows 274 are formed through the slave piston portion of the unitary structure to clear retainer 276 which is positioned in the windows and located by a retainer ring 278 seated in a groove formed in the slave cylin­ der 104. A slider 280, generally tubular in shape, is sized to reciprocate within the slave piston portion of the unitary slave piston and crosshead 258 when duct 270 ist pressurized. Windows 282 are formed in the slider 280 to register with the windows 274. A rocker arm 284 is affixed to the lower portion of the slider 280 by a screw 286 and locking cap 288. The rocker arm contact 284 should be provided with an appropriately hardened surface suitable for activation by the exhaust rocker arm 50. A transverse wall 290 is formed in the slider 290 near the upper end thereof. Slave piston return springs 292 are positioned between the retainer 276 and the transverse wall 290 of the slider 280 to bias the slider 280 upwardly and, in turn, bias the slave piston and crosshead 258 against the adjustable stop 110. A series of radial ports 294 are formed in the upper end of the slider 280 above the transverse wall 290 so as to register with the raceway 272 when the slider 280 is in its uppermost position. A piston 296 is located within the slider 280 above the transverse wall 290. The piston 296 is provided with an axial shaft 298 to guide spring 302 which bi­ ases the piston 296 away from the transverse wall 290. The lower circumferential portion of the piston 296 has substantially the same diameter as the inside of the slider 280 within which it can be reciprocated. The upper circumferential portion of the piston 296 is relieved to form a raceway 304. A plurality of balls 306, which may, for example, be ball bearings, is positioned in the series of radial ports 294. The balls 306 have a diameter greater than the wall thickness of the slider 280 so that the balls 306 extend into the raceway 272 and lock the slider 280 and the unitary slave piston and crosshead 258 together. When the slider 280 and the slave piston and crosshead 258 are locked together, oscillation of the rocker arm 50 will result in reciprocation of the crosshead so as to activate the exhaust valves 38. However, when duct 270 is pressurized, piston 296 is forced downwardly against the bias of spring 302 so that the raceway 304 comes into registry with the ra­ dial ports 294 and the balls 306 are cammed out of raceway 272 and toward raceway 304. This action unlocks the slider 280 from the unitary slave piston and cross­ head 258 so that actuation of the slider 280 by the exhaust rocker arm 50 will not result in opening the exhaust valves. However, when duct 102 is pressurized the unitary slave piston and crosshead 258 will be activated and the exhaust valves opened. Fig. 1B illustrates the mechanism of Fig. 1A during the retarding mode of operation wherein the exhaust valves have been disabled by unlocking the slider 280 from the unitary slave piston and crosshead 258. It will be appreciated from Fig. 1B that when the exhaust valves have been disabled by this mechanism the exhaust valve springs have, in effect been removed from the remainder of the exhaust valve train. If the slave piston return spring 292 exerts insufficient force to avoid play in the valve train and maintain contact among the rocker arm, pushtube, cam follower and cam, a supplemental spring mechanism may be provided. In the event that it is desired to employ separate crossheads and slave pistons in accordance with conventional practice, an alternative exhaust valve disabling mechanism according to the present invention may be used in place of the rocker arm adjusting screw and locknut. 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.

Claims: 1. A unitary slave piston and crosshead mechanism for an internal combustion engine equipped with a com­ pression release engine retarder comprising cross­ head means adapted to contact the stems of dual exhaust valves, characterized in that said crosshead means is integrally formed with slave piston means (258) adapted to reciprocate within a slave cylinder (104) formed in said compression release retarder; and in that said slave piston and crosshead mechanism comprises an internal bore formed in said crosshead means and said slave piston means, a first circumferential raceway (272) formed in said internal bore, a plurality of first transverse radial ports (266), and first transverse windows (274) communicating between said bore and the outer surface of said integral slave piston means, tubular slider means (280) positioned within said internal bore for reciprocating movement therein, second transverse window means (282) in said slider means adapted to register with said first transverse windows, contact means (284) associated with a first end of said slider means, a plurality of second transverse radial ports (294) and a transverse wall (290) formed adjacent the second end of said tubular slider means, retainer means (276) located within said first and second transverse windows and affixed to said slave cylinder, biasing means (292) positioned between said retainer means and a first side of said transverse wall, piston means (296) positioned for reciprocation within said tubular slider means in the region between said transverse wall and said second end of said tubular slider means, said piston means having a second circumferential raceway - (304) formed thereon, biasing means (302) adapted to bias said piston away from said transverse wall, and locking means (306) loosely located in said radial ports of said tubular slider means and adapted in their locking mode to register with said first circumferential raceway, whereby said tubular slider means is locked to said crosshead means, and in their unlocked mode to register with said second circumferential raceway (304) to permit said tubular slider means to reciprocate within said internal bore of said crosshead.

Inventors: MEISTRICK, ZDENEK SIDONIUS
Applicants: THE JACOBS MANUFACTURING COMPANY
Application year: 1986
Main classification: F01L13
IPC codes: F01L13