A hydraulic rocker arm for a combustion engine

Abstract

The present disclosure relates to a hydraulic rocker arm (1) for a combustion engine, the rocker arm (1) comprising a valve chamber (2) enclosing a hydraulic valve arrangement (2a) configured to at a first state enable oil to flow to and from an oil supply thereby actuating a piston (20) of said rocker arm (1), and at a second state stopping oil flow between two channels (8, 9) of said rocker arm (1). The rocker arm (1) further comprises a pressure relief valve (10) in hydraulic communication with said valve chamber (2), the relief valve (10) being configured to, upon a exceeding a pre-determined load level, discharge oil from the rocker arm (1). Further, the valve chamber (2) comprises a discharge channel (7) connected to said pressure relief valve (10), wherein a part of an outer surface (6) of said hydraulic rocker arm (1) forms an inner cavity (6b) dimensioned to secure said pressure relief valve (10) to said rocker arm (1).

Description

[0001] A HYDRAULIC ROCKER ARM FOR A COMBUSTION ENGINE

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to a hydraulic rocker arm for a combustion engine of a vehicle.

[0004] BACKGROUND

[0005] The role of the decompression release exhaust brake, hereafter called engine brake, is to convert a power-producing engine into a power-absorbing retarding mechanism and the valve train is a significant part of this mechanism. The engine braking mechanism for e.g., a four- stroke diesel engine comprises several strokes. On the normal intake stroke, the intake valve opens, and air is forced into the cylinder by boost pressure from the turbocharger. Then, in the compression stroke, air is compressed by the engine piston.

[0006] The energy required to compress this air is produced by the driving wheels of the vehicle. Near top dead center, the engine brake opens the exhaust valves, venting high pressure air and dissipating the stored energy through the exhaust system. On the downward stroke, essentially no energy is returned to the piston and to the driving wheels. There is a loss of energy and this loss is how the retarding work is accomplished.

[0007] The timing of the valve opening event is important because the piston at top dead center has done the maximum amount of work. If the valve is opened early, not much power will be absorbed. Similarly, if the valve is opened after top dead center, some power has been returned to the crank by the compressed air. As the valve opening event moves away from top dead center, the engine brake becomes less effective. In practice, it is necessary to use a cam or rocker motion that occurs close to top dead center for timing the valve opening event.

[0008] When the engine brake is activated, the oil supply pressure in the rocker shaft is raised by the solenoid valve in the cylinder head and the control piston moves away from check valve ball enabling it to close against the valve seat. The power piston moves outward and eliminates the valve lash. When the brake lift cam event starts, the check valve closes and creates a hydraulic lock between cam lobe and exhaust valves. The camshaft is now in direct contact with the exhaust valves, and the extra cams provides the engine brake lift events. To deactivate the engine brake, the solenoid valve lowers the rocker shaft oil supply pressure whereby the control piston pin opens the check valve. The hydraulic lock is eliminated, power piston retracts which increases valve lash and there are no brake lift events available. Power piston returns to original position by its integrated return spring.

[0009] However, in certain conditions the oil pressure in the rocker arm may become excessive. Then, a consequence of the movement of the piston towards the valve is that the rocker arm and its mating parts (such as the cam lobe and roller) can be exposed to excessive loads. Such excessive loads may wear and tear the rocker arm and mating parts thereof. A challenge is to handle high oil pressure when it arises without affecting the rocker arm design excessively.

[0010] The rocker arm needs to be compact in form to be able to optimize the space in the combustion engine of a vehicle.

[0011] Hence, there is room for a rocker arm that is able to handle high loads more efficiently. Specifically, there is room for rocker arms that are able to handle high loads more efficiently within limited packaging space.

[0012] SUMMARY

[0013] It is therefore an object of the present disclosure to alleviate at least some of the mentioned drawbacks to provide an improved hydraulic rocker arm that is less sensitive to excessive loads while maintaining compactness.

[0014] This and other objects, which will become apparent in the following, are achieved by a hydraulic rocker arm as defined in the appended claims.

[0015] The present disclosure relates to a hydraulic rocker arm for a combustion engine, the rocker arm comprising a valve chamber enclosing a hydraulic valve arrangement configured to at a first state enable oil to flow to and from an oil supply, thereby actuating a piston of said rocker arm, and at a second state stopping oil flow between two channels of said rocker arm.

[0016] Further, the rocker arm comprise a pressure relief valve (which may in some aspects be referred to as a high pressure relief valve) in hydraulic / fluidic communication with said valve chamber, the relief valve being configured to, upon a exceeding a pre-determined load level, discharge oil from the rocker arm, wherein said valve chamber comprises a discharge channel (in some aspects directly connected) connected to said pressure relief valve, wherein a part of an outer surface of said hydraulic rocker arm forms an inner cavity dimensioned to secure said pressure relief valve.

[0017] The cavity may be formed in a protrusion formed at a top surface of said rocker arm.

[0018] An advantage of the rocker arm is that it enables the rocker arm to withstand high oil pressure while maintaining compactness. Previous known solutions with the pressure relief valve integrated in the piston is not possible in combination with piston that has an integrated return spring for deactivation.

[0019] The valve chamber may, along a first direction, be positioned intermediate a piston of said hydraulic rocker arm and said pressure relief valve.

[0020] In other words, the pressure relief valve according to the disclosure herein can be distant / separated from a piston chamber that encloses the piston. Accordingly, the inner cavity is a different cavity compared to the piston chamber.

[0021] This allows for the space in the piston chamber to be optimized so that there is no clashing / disturbance between the relief valve and the piston.

[0022] An axial extension of said relief valve may be perpendicular to an axial extension of said hydraulic valve arrangement. This facilitates further compactness of the rocker arm.

[0023] Further, the cavity may be formed in a protrusion at a top surface of said rocker arm. An advantage of this is that a protrusion extending beyond the height of the top surface allow for easier insertion of parts in said cavity.

[0024] Furthermore, the cavity comprises a relief valve insertion opening configured to, during instalment; receive said pressure relief valve therethrough. The opening may be exposed to ambient environment outside said rocker arm allowing for manual insertion therethrough and easier maintenance of the relief valve.

[0025] The two channels may be a rocker arm channel connected to a piston chamber and a supply channel connected to a rocker arm oil supply.

[0026] Further, the rocker arm channel and said discharge channel jointly traverse said valve chamber. Moreover, at least the piston chamber, the rocker arm channel, the discharge channel and the valve chamber may be f luidica lly connected to have a common pressure level. Le. the piston chamber, the rocker arm channel, the discharge channel and the valve chamber may form a common high pressure chamber. Accordingly, upon pressure levels in the piston chamber are increased, the relief valve can ease said pressure even though its distant from the piston chamber.

[0027] The piston chamber may be referred to as a chamber that is variable in volume based on movement of the piston. The piston herein may be piston comprising a return-spring function. In other words, having a return spring for deactivation. Both piston and piston spring may be located in the piston chamber. The spring may be fully in the chamber.

[0028] The pressure relief valve may comprise: a seat closing said discharge channel a spring arrangement a valve cone intermediate said spring arrangement and said seat wherein upon exceeding said pre-determined load level said valve cone moves away from said seat thereby deforming said spring arrangement and allowing for discharge of oil along an axial extension out from said pressure relief valve.

[0029] The specific combination of features of the relief valve herein allow for compactness while maintaining performance.

[0030] Further, in some aspects, the valve cone comprises axial grooves (extending along the axial direction). The axial grooves provide a space-efficient route for the oil to be discharged efficiently.

[0031] The spring arrangement may comprise a first spring and a second spring, the first spring enclosing the second spring. An advantage of this is that the length of the springs can be minimized.

[0032] The relief valve may be arranged to, upon exceeding said pre-determined load level , discharge oil directly received from said valve chamber by means of said discharge channel. The pre-determined load level as referred to herein may be e.g. 250 -350 bar or 300-400 bar or any other suitable load level. It's very important that the relief valve is leak free below the chosen load level. Generally, all terms used in the description are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / an / the [element, device, component, means, step, etc.]" are to be interpreted openly as referring to at least one instance of said element, device, component, means, step, etc., unless explicitly stated otherwise.

[0033] BRIEF DESCRIPTION OF THE DRAWINGS

[0034] These and other features and advantages of the present disclosure will now be further clarified and described in more detail, with reference to the appended drawings;

[0035] Figure 1A illustrates an objective view of a rocker arm 1 in accordance with aspects herein;

[0036] Figure IB illustrates a side cross-sectional view of a rocker arm 1 in accordance with aspects herein

[0037] Figure 2A illustrates a side cross-sectional view of a relief valve 10 in accordance with aspects herein; and

[0038] Figure 2B illustrates an objective view of a relief valve 10 in accordance with aspects herein;

[0039] DETAILED DESCRIPTION

[0040] In the following detailed description, some embodiments of the present disclosure will be described. However, it is to be understood that features of the different embodiments are exchangeable between the embodiments and may be combined in different ways, unless anything else is specifically indicated. Even though in the following description, numerous specific details are set forth to provide a more thorough understanding of the present disclosure, it will be apparent to one skilled in the art that the present disclosure may be practiced without these specific details. In other instances, well known constructions or functions are not described in detail, so as not to obscure the present disclosure.

[0041] Figure 1A illustrates a hydraulic rocker arm 1 for a combustion engine from an objective view. The rocker arm 1 comprising a hydraulic valve arrangement 2a and a piston 20. The piston 20 being arranged to actuate / open an engine valve of an internal combustion engine. The rocker arm 1 is arranged to rotate about a rocker arm shaft (not shown). Further, the rocker arm 1 comprises a roller 30 arranged to contact a camshaft of the engine. The rocker arm may be a brake rocker arm. Further, the piston 20 may be a hydraulic actuator piston.

[0042] Figure IB illustrates a cross-sectional side view of the rocker arm 1 of Figure 1A. Figure IB illustrates that the rocker arm 1 comprises a valve chamber 2 enclosing a hydraulic valve arrangement 2a configured to at a first state enable oil to flow to and from an oil supply thereby actuating a piston 20 of said rocker arm 1 and at a second state stopping oil flow between two channels 8, 9 of said rocker arm 1.

[0043] Further, the rocker arm 1 further comprise a pressure relief valve 10 in (hydraulic / fluidic) communication with said valve chamber 2, the relief valve 10 being configured to, upon a exceeding a pre-determined load level, discharge oil from the rocker arm 1. The valve chamber 2 comprises a discharge channel 7 connected to said pressure relief valve 10, wherein a part of an outer surface 6 of said hydraulic rocker arm 1 forms an inner cavity 6b dimensioned to secure said pressure relief valve 10 to said rocker arm 1.

[0044] Upon discharge of oil from said rocker arm 1 by said relief valve 10, the piston 20 will be raised (i.e. reducing the volume of the piston chamber 21) and there will be reduced stress to the rocker arm and parts in contact with said rocker arm 1.

[0045] The channels 8 and 7 allow for the relief valve 10 to be separated / distance from the piston chamber 21, thereby increasing space efficiency therein.

[0046] If the relief valve 10 is closed, a hydraulic lock may be present. The relief valve 10 may be configured to actuate when said hydraulic lock is withstanding a pre-determined force. Thereby the rocker arm 1 is protected from excess forces.

[0047] As illustrated in Figure IB, the rocker arm 1 allows for release of pressure in the chambers 2, 21 and channels 8, 7 without affecting rocker arm function and while maintaining compactness. Further, as illustrated in Figure IB, the cavity 6b may be arranged at the top surface 6 so to allow convenient insertion and maintenance of the relief valve 10.

[0048] As illustrated in Figure IB, the valve chamber 2 is, along a first direction xl, positioned intermediate said piston chamber 21 enclosing the piston 20 of said hydraulic rocker arm 1 and said pressure relief valve 10. Referring back to Figure 1A, figure 1A illustrates that an axial extension clO of said relief valve 10 is substantially (i.e. +- 5 degrees) perpendicular to an axial extension c2 of said hydraulic valve arrangement 2a. Thereby, increased compactness is achieved.

[0049] Further, Figure IB illustrates that said cavity 6b is formed in a protrusion 6a at a top surface 6c of said rocker arm 1 arranged to allow manual insertion of said relief valve into said inner cavity 6b. The protrusion may, as illustrated in Figure IB protrude away from said outer surface 6.

[0050] Figure IB further illustrates that the relief valve 10 is arranged to, upon exceeding said predetermined load level, discharge oil directly received from said valve chamber 2 by means of said discharge channel 7. Further, Figure IB illustrates that the valve chamber 2 may be formed between the discharge channel 7 and the rocker arm channel 8. Accordingly, the piston chamber 21 may be connected to one end of the rocker arm channel 8, wherein the other end of the rocker arm channel 8 is connected to the valve chamber 2, wherein a first end of the discharge channel 7 is connected to the valve chamber 2 and a second end thereof is connected to the inner cavity 6b. Thus, the rocker arm channel 8 and said discharge channel 7 extend from the piston chamber 21 to the inner cavity 6b by jointly traversing said valve chamber 2.

[0051] Further, Figure IB illustrates that the inner cavity 6b may comprise a relief valve insertion opening 6c configured to, during instalment, receive said pressure relief valve 10 therethrough e.g. by manual insertion.

[0052] Accordingly, the present disclosure provides a channel configuration that facilitates efficient discharge of oil, while maintaining compactness and allowing for more convenient manufacturing.

[0053] Figure 2A illustrates a side cross-sectional view of the relief valve 10 inserted into said rocker arm. A part of the rocker arm is shown in Figure 2B, specifically the discharge channel 7 and the top surface 6a.

[0054] Figure 2A illustrates that the pressure relief valve 10 comprises a seat 12 closing / in contact with said discharge channel 7, a spring arrangement 11, a valve cone 13 intermediate said spring arrangement 11 and said seat 12. Upon exceeding said pre-determined load level said valve cone 13 moves away from said seat 12 thereby biasing said spring arrangement 11 and allowing for discharge of oil along an axial extension clO out from said pressure relief valve 10. Thus, when the cone 13 is closed against the seat 12 oil is prevented from being discharged. Upon reaching a load level the cone moves away and the pressure within the piston chamber 21 (see Fig. IB) will be reduced. Accordingly, the relief valve 10 can reduce pressure within the piston chamber 21 even though it's not positioned therein.

[0055] Figure 2A further illustrates that the spring arrangement 11 may comprise a first spring 11a and a second spring lib, the first spring 11a enclosing the second spring lib.

[0056] Figure 2B illustrates an objective view of said relief valve 10. Figure 2B illustrates that the cone 13 may comprise axial grooves 13'. The axial grooves 13' allow for the rocker arm 1 to maintain a compactness while being able to efficiently discharge oil. When the cone 13 moves away from the seat 12, the oil can be discharged from within the cone 13 by being transferred through the axial grooves 13' past the spring arrangement 11 and out from the opening (see ref. 6c in Figure IB) of the rocker arm 1.

Claims

CLAIMS1. A hydraulic rocker arm (1) for a combustion engine, the rocker arm (1) comprising a valve chamber (2) enclosing a hydraulic valve arrangement (2a) configured to: at a first state enable oil to flow to and from an oil supply thereby actuating a piston (20) of said rocker arm (1), and; at a second state stopping oil flow between two channels (8, 9) of said rocker arm (1); wherein the rocker arm (1) further comprise a pressure relief valve (10) in hydraulic communication with said valve chamber (2), the relief valve (10) being configured to, upon exceeding a pre-determined load level, discharge oil from the rocker arm (1), wherein said valve chamber (2) comprises a discharge channel (7) connected to said pressure relief valve (10), wherein a part of an outer surface (6) of said hydraulic rocker arm (1) forms an inner cavity (6b) dimensioned to secure said pressure relief valve (10) to said rocker arm (1).

2. The hydraulic rocker arm (1) according to claim 1, wherein the valve chamber (2) is, along a first direction (xl), positioned intermediate a piston chamber (21) enclosing the piston (20) of said hydraulic rocker arm (1) and said pressure relief valve (10).

3. The hydraulic rocker arm (1) according to any one of the preceding claims, wherein an axial extension (clO) of said relief valve (10) is perpendicular to an axial extension (c2) of said hydraulic valve arrangement (2a).

4. The hydraulic rocker arm (1) according to any one of the preceding claims, wherein said inner cavity (6b) is formed in a protrusion (6a) at a top surface (6c) of said rocker arm (1).

5. The hydraulic rocker arm (1) according to claim 4, wherein said inner cavity (6b) comprises a relief valve insertion opening (6c) configured to, during instalment, receive said pressure relief valve (10) therethrough.

6. The hydraulic rocker arm (1) according to any one of the preceding claims, wherein said two channels (8, 9) are a rocker arm channel (8) connected to a piston chamber (21) and a supply channel (9) connected to a rocker arm oil supply.

7. The hydraulic rocker arm (1) according to claim 5, wherein said rocker arm channel (8) and said discharge channel (7) jointly traverse said valve chamber (2).

8. The hydraulic rocker arm (1) according to any one of the preceding claims, wherein said pressure relief valve (10) comprises: a seat (12) connected to said discharge channel (7) a spring arrangement (11) a valve cone (13) intermediate said spring arrangement (11) and said seat (12) wherein upon exceeding said pre-determined load level said valve cone (13) moves away from said seat (12) thereby biasing said spring arrangement (11) and allowing for discharge of oil along an axial extension (clO) out from said pressure relief valve (10).

9. The hydraulic rocker arm (1) according to claim 7, wherein said valve cone (13) comprises axial grooves.

10. The hydraulic rocker arm (1) according to claim 7 or 8, wherein the spring arrangement (11) comprises a first spring (11a) and a second spring (lib), the first spring (11a) enclosing the second spring(llb).

11. The hydraulic rocker arm (1) according to any one of the preceding claims, wherein the relief valve (10) is arranged to, upon exceeding said pre-determined load level, discharge oil directly received from said valve chamber (2) by means of said discharge channel (7).

Images