A piston positioning mechanism

Abstract

A piston positioning mechanism includes a resilient retainer disposed in an annular groove on the outside of the piston, the resilient retainer engaging the wall of the bore of the piston to create a resistance to movement of the piston within the bore, the resistance to movement maintaining the piston in a retracted position within the bore, the retracted position being one in which the piston is clear of the engine valves. The embodiment eliminates the need for a conventional piston return spring, reduces the height of the piston mechanism, and reduces the opening oil pressure of the piston.

Description

Technical Field:

[0001] This embodiment relates to the field of mechanics, and more particularly to engines, specifically a positioning mechanism for a piston inside an engine rocker arm. Background technology:

[0002] Cummins Engine Company disclosed a dedicated brake rocker arm in U.S. Patent No. 5,626,116 (1997). The dedicated brake rocker arm incorporates a hydraulic brake drive mechanism, including a hydraulic piston. When engine braking is not required, a return spring biases the hydraulic piston in the retracted position, disconnecting it from the engine valves (no action is taken), and the movement of the dedicated brake cam is skipped (lost), resulting in no braking valve movement. When engine braking is required, oil pressure overcomes the force of the return spring, pushing the hydraulic piston from the retracted position to the extended position, connecting it to the valve, and transmitting the movement of the brake cam to one of the two exhaust valves, generating the valve movement for engine braking.

[0003] In fact, the pistons in the rocker arms of existing engines are biased into the retracted position by a return spring, which increases the height of the piston mechanism (the height of the return spring) and the oil pressure required for the piston to open (extend) (to overcome the preload of the return spring). Summary of the Invention:

[0004] The purpose of this embodiment is to provide a piston positioning mechanism that eliminates the return spring in the piston mechanism of the prior art, and solves the technical problems of large height and high starting oil pressure caused by the return spring.

[0005] This embodiment discloses a piston positioning mechanism, wherein the piston is installed in the piston hole of an engine rocker arm. The piston positioning mechanism includes an elastic retaining ring, which is installed in an annular groove on the outside of the piston. The outer periphery of the elastic retaining ring acts on the hole wall of the piston hole, creating resistance to the piston's up-and-down movement within the piston hole. The movement resistance keeps the piston in a retracted position within the piston hole. In the retracted position, the piston avoids interaction with the engine valve.

[0006] Furthermore, the elastic retaining ring includes a C-shaped steel wire retaining ring, the outer diameter of which is larger than the diameter of the piston hole.

[0007] Furthermore, the width and depth of the outer ring groove of the piston are both slightly larger than the wire diameter of the C-type steel wire retaining ring.

[0008] Furthermore, the engine rocker arm includes an engine brake rocker arm.

[0009] Furthermore, the engine rocker arm includes an engine variable valve drive rocker arm.

[0010] Compared with existing technologies, this embodiment has positive and significant advantages. This embodiment eliminates the return spring in the piston mechanism of existing technologies, solving the technical problems of large height and high starting oil pressure caused by the return spring. It also offers advantages such as convenient installation, high reliability, and low cost. Attached image description:

[0011] Figure 1 This is a schematic diagram of the piston positioning mechanism applied to the engine valve drive mechanism in an embodiment.

[0012] Figure 2 This is a schematic diagram showing the position of the piston positioning mechanism within the piston mechanism (enlarged) in an embodiment.

[0013] Figure 3 This is a schematic diagram of an elastic retaining ring for the piston positioning mechanism in an embodiment. Detailed implementation method:

[0014] Example:

[0015] like Figure 1 As shown, the engine rocker arm 210 (shown here as an independent braking rocker arm) is oscillatingly mounted on a rocker arm shaft (not shown). One end of the rocker arm 210 (here, a roller 235, or a pushrod mechanism) has a cam 230 (shown here as a brake cam), and the other end has an engine valve 301 (the valve stem of valve 301 has a valve stem cap 405, and the valve bridge 400 presses on the valve stem cap 405; a conventional exhaust rocker arm acts on the center of the valve bridge 400, driving the two exhaust valves). A piston mechanism 100 (shown here as an engine braking mechanism) is housed within the rocker arm 210 above the valve 301.

[0016] When engine braking is required, the engine braking control mechanism, such as a solenoid valve (not shown), opens the oil supply, and the engine oil flows through the oil passage 130 in the rocker arm 210 and the oil passage 131 in the piston mechanism 100. Figure 2The hydraulic pressure drives the piston 160 to extend downwards through the piston bore 260 at the upper end of the piston 160 and the one-way valve 53. The upper stop surface 161 of the piston 160 rests on the upper surface 106 of the big end 107 of the screw 105 (fixed to the rocker arm 210). The valve 301 is connected to the extended piston 160 through the valve stem cap 405 (or directly through the valve bridge 400). At the same time, the roller 235 is connected to the base circle 229 of the brake cam 230. The movement of the brake boss 231 (which may also have an EGR or BGR boss) on the brake cam 230 is transmitted to the engine valve 301 through the rocker arm 210 and the extended piston 160 inside the rocker arm (the piston bore 260 at the upper end of the piston 160 has a hydraulic connection - high-pressure oil), generating the valve movement required for engine braking. Of course, the engine ignition valve movement (including exhaust valve movement) generated by the conventional valve drive mechanism (not shown) always exists and does not interfere with the braking valve movement (the valve opening phase and height for ignition and braking are different).

[0017] During normal ignition (non-engine braking) operation, the engine braking control mechanism, such as the solenoid valve (not shown), disconnects to discharge oil, and piston 160 is pushed upward by valve 301. Figure 1 and 2 In the retracted position shown, the lower stop surface 162 of the piston 160 rests on the lower surface 108 of the large end 107 of the screw 105 (fixed to the rocker arm 210). A gap 111 is created between the piston 160 and the valve 301, bypassing the movement of the brake boss 231 (or possibly an EGR or BGR boss) on the brake cam 230, and no brake valve movement is generated.

[0018] In practical applications, due to the bumps / vibrations generated by vehicle operation and the influence of gravity, the piston 160 (which is in the retracted position within the piston bore 260 of the rocker arm 210) Figure 1 and Figure 2 It is possible that the piston will extend downwards and collide with valve 301 (valve stem cap 405). To solve this problem, the piston positioning mechanism of this embodiment is provided. The piston positioning mechanism includes a resilient retaining ring 165 ( Figure 3A C-shaped wire retaining ring (165) is placed in an annular groove 163 on the outside of the piston 160 (obviously, the width and depth of the annular groove 163 are slightly larger than the wire diameter of the elastic retaining ring 165). The outer circumference of the elastic retaining ring 165 acts on the wall of the piston bore 260 (the outer diameter of the elastic retaining ring 165 is larger than the diameter of the piston bore 260), creating resistance to the up-and-down movement of the piston 160 within the piston bore 260. This resistance keeps the piston 160 in a retracted position within the piston bore 260, avoiding interaction with the engine valve 301. Note that this resistance is much smaller than the thrust of the engine oil on the piston 160 during braking and does not affect the opening (extension) of the piston 160.

[0019] The examples above are illustrative of this embodiment and not intended to limit it. In fact, those skilled in the art can readily modify and vary this embodiment within its scope and principles. For example, a certain function described or illustrated in one specific mechanism can be used in another specific mechanism, resulting in a new mechanism. The rocker arm in the embodiment can be other types of rocker arms besides engine braking rocker arms, such as EGR rocker arms or rocker arms for engine variable valve actuation. Furthermore, the position and mounting method of the positioning mechanism can be different. In addition, the material, form, and mounting of the elastic retaining ring can also be different. Therefore, this embodiment will include the above modifications and variations, provided they fall within the scope of the appended claims or equivalent claims.

Claims

1. A piston positioning mechanism for a piston disposed in a piston bore of a rocker arm of an engine, the mechanism comprising: The piston positioning mechanism includes an elastic retaining ring, which is placed in an annular groove on the outside of the piston. The outer periphery of the elastic retaining ring acts on the bore wall of the piston bore, creating resistance to the piston's up-and-down movement within the piston bore. This resistance keeps the piston in a retracted position within the piston bore, where it avoids contact with the engine valves.

2. The piston positioning mechanism of claim 1, wherein: The elastic retaining ring includes a C-shaped steel wire retaining ring, the outer diameter of which is larger than the diameter of the piston hole.

3. The piston positioning mechanism of claim 2, wherein: The width and depth of the outer ring groove of the piston are both slightly larger than the wire diameter of the C-type steel wire retaining ring.

4. The piston positioning mechanism of claim 1, wherein: The engine rocker arm includes an engine brake rocker arm.

5. The piston positioning mechanism of claim 1, wherein: The engine rocker arm includes an engine variable valve drive rocker arm.

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