AU2017100948B4 - Supercharger clutch - Google Patents

Abstract

1l:\jzc\Interwovn\NRPortbl\DCC\JZC\1517071 [_.doc-[ 07/2017 Abstract A clutch that couples an engine to a supercharger, the clutch having an engaged position wherein the engine and the supercharger are operatively coupled and a disengaged position wherein the engine and the supercharger are not coupled, the clutch being configured to adopt the engaged position after engine start up.

Description

SUPERCHARGER CLUTCH

TECHNICAL FIELD

[0001] The present invention generally relates to clutches and in particular to a clutch for coupling a supercharger to an engine.

BACKGROUND

[0002] Superchargers are commonly used on diesel driven vehicles as a means for increasing the power possible from a given engine displacement. Superchargers pump air into the engine cylinders to increase the total amount of air available and thereby allow more fuel to be burned. They are mechanically connected to the crankshaft of the engine to provide the power necessary to operate.

[0003] Superchargers are traditionally belt driven, however in underground mining operations the belt drives are generally not considered safe, due to their potential to provide an ignition source and therefore lead to an explosion. As such, many underground diesel driven mining vehicles are turbocharged, as a turbocharger is driven by an engine's exhaust gas and does not need to be mechanically driven by the engine.

[0004] A supercharger is preferable to a turbocharger, however, for reasons including that there is no throttle lag. For underground mining, a supercharger can still be used but a direct drive system is preferred, instead of a belt drive, due to the exposure to contamination that significantly reduces the life of the belt drive.

[0005] Traditionally, direct drive for high torque mining vehicle engines has met with limited success due to supercharger or coupling damage resulting from harmonics and high shock loads, particularly during start-up and power down cycles of the engine.

[0006] The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as, an acknowledgement or admission or any form of suggestion that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

BRIEF SUMMARY

[0007] The present invention seeks to provide a clutch for connecting an engine to a supercharger, particularly but not exclusively for a diesel engine used in vehicles for underground mining applications.

[0008] According to one example aspect, there is provided a clutch that couples an engine to a supercharger, the clutch having an engaged position wherein the engine and the supercharger are operatively coupled and a disengaged position wherein the engine and the supercharger are not coupled, wherein the clutch includes a spring that holds the clutch in the disengaged position during engine start up and wherein the clutch is driven against bias of the spring by engine oil pressure to adopt the engaged position after engine start up.

[0009] In another form, the clutch includes: a cylinder with a piston slidably seated therein, wherein the spring is coupled to the piston and movement of the piston actuates the clutch between the engaged and disengaged positions; a piston spring configured to bias the piston towards the disengaged position; a hydraulic circuit configured to actuate the piston to the engaged position; and at least one clutch pressure disk, one clutch reaction disk and one clutch friction assembly configured to engage one another when the clutch is in the engaged position; wherein the hydraulic circuit couples the engine oil pressure and the piston.

[0010] In another form, the clutch is actuated electronically, instead of using engine oil pressure.

[0011] In another form, the clutch is actuated to the engaged position after engine startup and to the disengaged position prior to or at engine shutdown.

[0012] In another form, the supercharger and the engine are operatively connected to the clutch using gears.

[0013] In another form, the hydraulic circuit includes a mechanically or hydraulically operated valve system that provides hysteresis between an engage oil pressure and a disengage oil pressure.

[0014] In another form, the engage oil pressure is at or above about 170 kPa and the disengage oil pressure is at or below about 140 kPa.

[0015] In another form, the clutch is in the engaged position when the oil pressure is at or above 200 kPa.

[0016] In another form, the piston spring provides a force of between 400 N and 600 N, and preferably between 450 N and 550 N, and most preferably about 500 N.

[0017] In another form, during engine startup the clutch engages prior to the engine reaching a speed of 1000 rpm.

[0018] Preferably, the clutch includes no electronic components.

[0019] According to another example aspect, there is provided an engine for an underground mining vehicle, including a supercharger with a clutch to engage the supercharger after engine startup.

[0020] In another form, the clutch is substantially as herein described.

[0021] According to another example aspect, there is provided a mining vehicle for use in an underground mine, including an engine substantially as herein described.

BRIEF DESCRIPTION OF FIGURES

[0022] Example embodiments should become apparent from the following description, which is given by way of example only, of at least one preferred but nonlimiting embodiment, described in connection with the accompanying figures.

[0023] Figure 1 illustrates an exploded view of a supercharger gearbox including a clutch; [0024] Figure 2 illustrates an exploded view from another angle of a supercharger gearbox including a clutch; [0025] Figure 3 illustrates a substantially front view of a supercharger gearbox; [0026] Figure 4 illustrates a rear view of a supercharger gearbox; [0027] Figure 5 illustrates a cross section of a clutch; [0028] Figure 6 illustrates a schematic diagram of a valve used to connect the engine oil to the clutch; [0029] Figure 7 illustrates an exploded view of a valve; and [0030] Figure 8 illustrates an assembled valve.

PREFERRED EMBODIMENTS

[0031] The following modes, given by way of example only, are described in order to provide a more precise understanding of the subject matter of a preferred embodiment or embodiments.

[0032] In the figures, incorporated to illustrate features of an example embodiment, like reference numerals are used to identify like parts throughout the figures.

[0033] Referring to Figure 1, a complete supercharger gearbox is shown in exploded form. A clutch 1 is designed to releasably couple an input shaft 2 to an output gear 3. A first primary gear 10 is driven by the engine, which then drives a first secondary gear 11 that is connected to the input shaft 2. On the other side of the clutch 1, the output gear 3 drives a second secondary gear 12, which drives a drive hub 13 that is connected to the supercharger by a coupler 14. The output is supported by a bearing hub 15.

[0034] Various bearings 20, shafts 21, cir-clips 22, washers 23, keys 24, bolts 25, washers 26 and dowels 27 are used, as would be understood by those skilled in the art. The complete assembly is enclosed in a housing 30 with a support bracket 31.

[0035] The oil supply to the clutch is provided by a clutch supply adaptor 90, connected to the housing 30 with the aid of an o-ring 91, straight fitting 88 and nipple 89. Figure 2 shows further fluid connections, including components such as elbow adaptors 85, swivel adaptors 86, restricted adapters 92, reducers 93, caps 94 and straight adapters 95.

[0036] Figure 2 shows the same exploded assembly from a different view, illustrating the output where the coupler 14 connects the supercharger to the drive hub 13. Figures 3 and 4 show external views of the complete supercharger gearbox.

[0037] Referring to Figure 5, a cross section of a clutch 1 according to the present invention is shown. The clutch 1 releasably couples the input shaft 2 to the output gear 3. The clutch itself includes a cylinder 50 in which a piston 51 is slidably fitted. The piston 51 seals with the inside of the cylinder 50 using an inner o-ring 52 and an outer o-ring 53.

[0038] The output gear 3 connects via a square gear key 54 to the clutch cylinder 50, which in turn is coupled to a reaction disk 62 and pressure disks 63. The input shaft 2 connects via a clutch hub 61 to friction assemblies 60. The piston 51 can be forced in the direction towards the clutch disks 60, 62, 63 by oil or another fluid being provided through the clutch supply adapter 90. This causes the friction assemblies 60, the reaction disk 62 and the pressure disks 63 to be forced together and thereby transmit torque.

[0039] When the pressure on the piston 51 is reduced, a piston spring 55 forces the piston 51 back in the opposite direction by applying force between the piston 51 and a spring retainer 56. This reduces the pressure between the clutch disks 60, 62, 63 and decouples the input shaft 2 from the output gear 3.

[0040] Other components shown in Figure 5 include a shim 65, bushing 66, retaining ring 67, thrust bearing assembly 68, housing 69, clutch retaining ring 70, screw 71, seal 72, sealing ring 74, sealing ring 75, retaining ring 76, bushing 77, washer 78 and retaining ring 79.

[0041] In a preferred embodiment, the forcing of the piston 51 as described above is achieved using oil pressure from the engine. The engine oil is connected to a valve 80 at an input 81, as shown in Figure 6. An engine oil feedback 82 applies against the force of the spring. The valve 80 includes an output 83 that connects to the clutch supply adapter 90 of the clutch 1, and a clutch feedback 84.

[0042] When the oil pressure exceeds a predetermined value the hydraulic port to the clutch 1 is open, causing the clutch 1 to engage and connect the input shaft 2 to the output gear 3, or in the present invention transfer power from the engine to the supercharger. When the engine oil pressure reduces the reverse process occurs. Other similar valve designs that achieve a similar purpose are envisaged and fall within the scope of the invention.

[0043] Various fittings are shown in Figure 7 for connecting the valve 80, including elbow adaptors 85, swivel adaptors 86, tee adaptor 87, straight fittings 88 and nipples 89. Figure 8 shows the valve 80 and fittings in assembled form.

[0044] The present invention uses engine oil pressure to activate and release the clutch. The valve 80 is designed to activate the clutch 1 once the engine oil has reached idle pressure. This process of engaging the clutch at startup will typically happen over a period of about 0.5 seconds. Upon engine shutdown the oil pressure is released and the clutch is disengaged. This automatic and controlled engaging and disengaging of the clutch at startup and shutdown of the engine reduces shock loads on the supercharger and significantly extends the life of the supercharger and other associated drive train components.

[0045] A key feature of the invention is the combination of the clutch in the diesel engine to supercharger driveline, together with using engine oil to activate the clutch and a hydraulic valve, without the use of electronics. The lack of electronics is an important feature when employing the invention in underground mining. In such an application, using electronics would require a flameproof enclosure and extensive and expensive validation.

EXAMPLE EMBODIMENT

[0046] In one example embodiment, a wet clutch assembly is used that is based on the principles of a wet clutch in an automatic transmission. The assembly uses a simplistic hydraulic system to engage and/or disengage the clutch. The following design criteria were used in the clutch and hydraulic concept: 101 Nm before the supercharger input gear (41.3 Nm required torque for supercharger output gear);

Engine oil pressure at idle is 205 kPa and engine oil pressure at flight is 345 kPa;

Clutch engagement is achieved using engine oil pressure;

Clutch engagement occurs at a maximum engine speed of 1,000 rpm;

Engine oil and supercharger lubricant circuit fdters are 10 pm filters; and

The overall length can be extended by a maximum of 50 mm; No increase in outside diameter of the housings is possible.

[0047] In relation to the friction plate design, the clutch sizing is based on available bronze friction plates and mating steels. Alternatively, paper lined friction plates could be used, although paper lined plates are sensitive to water and delamination and are generally used as shifting clutches.

[0048] The return spring force in an automatic transmission is generally designed to provide 1 atmosphere (100 kPa) when the clutch apply pressure is between 1200 and 2400 kPa. This is to allow quick disengagement of the clutch, particularly during shifting. However, using the above guideline and the desirable 175 kPa clutch apply pressure does not lead to a reasonable design. This is because the engagement pressure of 175 kPa less the return spring force (equivalent pressure of 100 kPa) yields an effective apply pressure of only 75 kPa. This would require more friction plates (in the proposed design 10 friction plates are used) or a larger mean diameter.

[0049] Hence, to reduce the number of plates or size of the clutch, the return spring load needs to be also reduced. However, the clutch return spring must at minimum overcome the drag of the piston seals which is estimated to be up to 150 N (depending on the squeeze on the seals). Given this, the recommended return spring force should be approximately 500 N. In the proposed design, this is an equivalent pressure of 50 kPa.

[0050] This design trade-off, however, does introduce some risk if the seal drag is higher than expected. This means the piston may not fully retract and the clutch drags.

[0051] The return spring can be a single helical spring, a helical spring pack, a Belleville/wave spring, or any other suitable biasing means. A single helical spring has been sized in the design as it is simple to manufacture and low in cost.

[0052] The static friction coefficient used in sizing the clutch is based on experience, using bronze friction plates and industrial synthetic gear oil. The static friction coefficient used in the design is 0.14. It is recommended that a trial is conducted to ensure that the combination of the proposed engine oil and the clutch pack can transmit the required torque for a particular design and application. Axial space for an additional friction plate and steel should be allowed for in the design of the clutch housing.

[0053] Traditionally, the control of the clutch would be through the use of an electro-hydraulic solenoid. However, this is not appropriate in some situations, such as in underground mines, where electronic components create an explosion risk as they are a potential ignition source. Instead, in the present invention, a hydraulic valve based on the supply of engine oil is used to engage the clutch at 175 kPa and disengage at 140 kPa. The valve design has two areas which provide the needed hysteresis to achieve this mechanism. In alternative embodiments, with different component designs, these engage and disengage pressures will change accordingly.

[0054] In one embodiment the piston seal uses an o-ring design. O-rings are simple, low in cost and easily available. Preferably the o-ring squeeze is minimised (5-10% maximum) since the clutch apply pressure and the return spring load are low.

[0055] The clutch assembly in the present embodiment can float in either direction. The clutch assembly can be fixed using one of the following methods: A snap ring can be fitted to the left of the clutch on the main shaft and next to the clutch hub; A retaining ring fitted internally under the clutch hub on the main shaft; and The main shaft extends outwardly behind the clutch hub.

[0056] The valve will be designed such that the clutch will be engaged when the engine oil pressure reaches 175 kPa. To determine the engine speed at which the clutch will engage, the engine pump pressure versus engine speed is required.

[0057] Preferably, the clutch seals on the main shaft are a scarf cut design in a material that is compatible with the engine oil. Also preferably, the components are manufactured from steel to minimise cost. However, the assembly may have a weight penalty. It is recommended that a 100 pm filter is added before the clutch control valve to entrap any swarf or other large material that may be introduced into the circuit.

[0058] Many modifications will be apparent to those skilled in the art without departing from the scope of the present invention.

Claims (4)

1. The claims defining the invention are as follows:

   1. A clutch that couples an engine to a supercharger, the clutch having an engaged position wherein the engine and the supercharger are operatively coupled and a disengaged position wherein the engine and the supercharger are not coupled, wherein the clutch includes a spring that holds the clutch in the disengaged position during engine start up and wherein the clutch is driven against bias of the spring by engine oil pressure to adopt the engaged position after engine start up.
2. 2. The clutch according to claim 1, wherein the clutch includes: a cylinder with a piston slidably seated therein, wherein the spring is coupled to the piston and movement of the piston actuates the clutch between the engaged and disengaged positions; a hydraulic circuit configured to actuate the piston to the engaged position; and at least one clutch pressure disk, one clutch reaction disk and one clutch friction assembly configured to engage one another when the clutch is in the engaged position; wherein the hydraulic circuit couples engine oil pressure to the piston.
3. 3. The clutch according to claim 2, wherein the hydraulic circuit includes a mechanically operated valve system that provides hysteresis between an engage oil pressure and a disengage oil pressure.
4. 4. An engine for an underground mining vehicle, with the clutch of any one of claims 1 to 3 to engage a supercharger.