Hydraulic Adjusting Arrangement for an Injection Pump

The present invention relates generally to a timing device, more particularly to a timely adjustment device for the control of the fuel injection start for a motor vehicle internal-combustion engine. Preferred embodiments of the invention relate to an arrangement for controlling the fuel injection start, wherein a connection; having one section fixed to move with a primary part of the transmission and another section positioned to move with a secondary part of the transmission, effects a circumferential rotation of the secondary part with respect to the primary part.

Based on U.S. Pat. No. 3,973,540, a hydraulic adjusting device is known where the rotating movement between the primary part and the secondary part is forced as a function of the admission of pressure medium to the piston via diagonally extending slot guiding means.

Also, a hydraulic adjusting device is known from U.S. Pat. No. 3,685,499 where the axially acting piston is connected with the primary part by an expensive toothing. In this case, the toothing is to permit a rotationally stable connection as well as a relative movement in an axial direction between the primary part and the piston. For the relative rotational movement between the primary and the secondary part, balls are provided as transfer members which are guided in diagonally extending guide grooves.

The invention is based on the objective of creating, in view of the embodiment according to U.S. Pat. No. 3,685,499, a hydraulic adjusting device where a rotation of the secondary part relative to the primary part can take place with little or no hydraulic pressure adjusting angles.

This objective is achieved by the effective direction of the piston as well as the arrangement and development of the transfer members connected with this piston. In the particular embodiment shown in FIGS. 1-3, the flexible connector, which effects circumferential rotation of the second any part with respect to the primary part is comprised of a chain linkage attached to the primary part of the transmission by means of a bolt through one link and positioned with respect to the secondary part of the transmission in such a way that the linkage rests on a lever which is pivotally attached to the secondary part. By these arrangements, operation of the hydraulic timing adjustment arrangement is achieved at a low pressure, such as the engine oil pressure, because the radial movement of the piston as well as the swivel movement of the lever is supported by the centrifugal forces occurring at an increasing speed of the internal-combustion engine.

Further, objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawing(s) which show, for purposes of illustration only, an embodiment constructed in accordance with the invention.

FIG. 1 is a cross section view of the hydraulic timing adjustment arrangement according to the invention, taken at the Line I--I in FIG. 2, where the upper radial pistin is shown in position where pressure is admitted to it, but the lower left radial piston is shown in a position without pressure.

FIG. 2 is a longitudinal sectional view of the hydraulic timing arrangement where the upper radial piston is shown in a position where pressure is admitted to it.

FIG. 3 is a top view of the hydraulic timing adjustment arrangement.

As shown in FIG. 1, a hydraulic timing adjustment arrangement 1 in the embodiment of a radial-piston timing injection mechanism for the control of the fuel injection start for a motor vehicle internal-combustion engine is mounted on the camshaft 2 of a conventional injection pump that is not shown. The arrangmeent consists of a primary part 3 on the drive side and a secondary part 4 on the side of the injection pump.

As shown in FIGS. 1 and 2, the secondary part 4 is composed of a bearing sleeve 6 connected with the injection pump shaft 2 by means of spline 5, and a cylinder housing having three cylinders 7a, 7b, 7c evenly distributed in a circumferential direction. Crowned radial pistions 8 are guided within the cylinders, and move in a direction perpendicular to or approximately perpendicular to the axis of the shaft 2.

A lever 9 extending in circumferential direction is pivotally attached to the secondary part by swivel shaft 10 and to a respective radial piston 8. In the close area of the swivel shaft 10, a flexible connector 11 illustrated as a chain piece is rotably fastened to the lever 9. The chain links 11a of the flexibile connector 11 complete or partially rest on the arched back 9a of the lever 9, depending on the position of the radial piston 8. The free driving arm 11b of the flexible connector 11 is fixed to the primary part 3 by means at a bearing bolt 12. The primary part 3 is equipped with a drive toothing 3a and is pivoted on a part of the bearing sleeve 6 that projects from the end. The primary part 3 has projections 13 at which pull-back springs 14 support themselves. The pull-back springs 14 are connected with the secondary part 4 and are developed as torsion springs.

The hydraulic timing adjustment arrangement operates as follows.

The three radial pistons 8 are hydraulically operated by hydraulic oil which, via an arrangement 16 of bores, namely a radial bore 16a and an axial bore 16b in the injection pump shaft 2, and an oil bore 17 in the bearing sleeve 7, is fed to the respective pressure spaces 18 that are defined by the radial pistons 8 and the wall surfaces of the cylinders 7a, 7b and 7c. The radial movement of the radial piston 8 causes a swivel movement of the lever 9 which is pivotally attached to the pistons and to the secondary part. Additionally, the radial movement of the piston 8 and the subsequent movement of the lever 9 due to the hydraulic pressure is supported on the centrifugal forces occurring at an increased speed of the internal combustion engine. In the process, the flexible connectors 11 are forced outward and deformed changing the spacing in the circumferential direction of the bearing points on the primary and the secondary side. The rotation of the primary part and the secondary part with respect to one another causes a rotation of the injection pump shaft 2 which corresponds to a change of the injection start. In the case of a pressure relief of the piston 8, the torsion springs 14, which act against the force of the upward moving radial pistons 8, cause the readjustment of the secondary part relative to the primary part back into the starting position.

The inflow or the outflow of the hydraulic oil to the radial piston is controlled via a servo valve that is controlled by an electronic regulating system which is connected to the motor oil circulating system (not shown). Thus, the actual value of the adjusting angle corresponds to the desired value determined by the electronic regulating system according to speed, load and temperature.