Friction testing apparatus and method

Abstract

The invention relates to a test device (1) for measuring frictional properties of a fluid or of a sample immersed in the fluid, and comprising a first sample holder (10) holding a first sample (13) in the fluid being tested such that the first sample (13) is in contact with a surface of a second sample (14) in a second sample holder (15). Means are provided for applying a measurable load between the two samples, and oscillation drive means oscillate the first sample holder relative to the second sample holder in a first direction, and force measurement means (24) measure a frictional force between the two samples. The sample holders (10, 15) are located in a sealed pressure chamber (4) such that the test can be carried out at a selectable pressure, and wherein a push rod (9) is provided which provides an oscillating movement of the first sample holder (10) within the pressure chamber (4) so as to maintain the pressure during the test. The pressure chamber is removable and maintains pressure or vacuum even when removed from the remainder of the test device (1).

Description

Technical Field

[0001] The present invention relates to an apparatus and method for testing the lubrication properties of liquids, gases, or other fluids and / or the friction and wear properties of materials. Such an apparatus simulates the operating conditions of a mechanical device (e.g., a fuel pump or gearbox) having moving parts and a fluid lubricant. During the test, the condition of the lubricant or other fluid being tested, the condition of the moving parts, and the forces acting on the moving parts can be measured. These measurements often enable testing of new materials and lubricants or other fluids before they are sold as new products or incorporated as components into new products. Background Art

[0002] An important feature of such testers is that they produce reproducible, reliable results for a range of test fluids under varying circumstances. The results depend on the reliability of the wear of the test specimen, which needs to accurately correlate with the properties of the test fluid under the conditions that the test fluid will experience during its intended use.

[0003] Previously disclosed UK Patent No 2270387 describes an apparatus for testing lubricity using a rigid push rod.

[0004] It is an object of the present invention to provide an improved testing apparatus that tests fluids and / or materials under conditions that more closely resemble the real conditions that the fluids or materials would experience. Summary of the Invention

[0005] According to the present invention, there is provided a testing apparatus and method according to the accompanying claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The invention is illustrated by way of example only in the accompanying drawings in which:

[0007] Figure 1 is a perspective view of a test device according to a first embodiment of the present invention,

[0008] Figure 2 yes Figure 1 A side view of the front of the test apparatus with the test component engaged,

[0009] Figure 3 yes Figure 1 Front view of the test equipment,

[0010] Figure 4 yes Figure 1 An enlarged perspective view of the front of the test equipment,

[0011] Figure 5 yes Figure 1 a schematic side cross-sectional view of the front of the test apparatus, and

[0012] Figure 6 is a perspective view of the front of the test device separated from the test device. DETAILED DESCRIPTION

[0013] With reference to the accompanying drawings, there is shown a main embodiment of a test apparatus 1 according to the present invention, comprising a housing 2 and a front part 3 in which an upper sample 13 and a lower sample 14 can be mounted. The upper sample 13 is releasably retained in an upper sample holder 10 by a grub screw 12. The upper sample 13 comprises a ball of material to be tested. It will be appreciated that in other embodiments the lower sample may be the material to be tested and / or a fluid in contact with the upper and lower samples 13, 14. The upper sample holder 10 is attached by a support block 11 to a push rod 9 which in turn is connected to an electromagnetic vibrator (not shown) and is located inside the housing 2. The test consists of oscillating the test ball (which is the upper sample 13) against the lower sample 14 in the form of a test disc under load.

[0014] After each test, the width, length and depth dimensions of the wear signs or wear marks on either or both of the upper and lower samples 13 and 14 are measured and correlated to the wear properties of either sample and / or the friction properties of the fluid being tested.

[0015] In this embodiment, a completely sealed pressure chamber 4 is provided around the contact area of the lower sample 13 and the upper sample 14, which enables testing to be performed under high pressure or vacuum. The front portion 3 of the device is detachable and includes the pressure chamber 4, which can maintain pressure or vacuum even when removed from the test apparatus 1 to another location, so that the test blends can be kept away from the rest of the test apparatus 1. Figure 6 The separated front part 3 is shown in a position for pressurization.

[0016] The fuel or lubricant can be tested under the same pressure and temperature conditions as they will be experienced during use, thus allowing for a fast, reliable and inexpensive method of testing fuels and lubricants or components that come into contact with the fuel or lubricant.

[0017] The pressure chamber 4 is enclosed by three parts: a removable cover 5 with a glass window 6 , an upper chamber part 7 and a lower chamber part 8 .

[0018] The lower sample holder 14 includes an upstanding wall 16 which can contain a test fluid 17 if desired.

[0019] The upper sample holder 10 is located in an upper support block 11, which is attached to two metal bellows 18a, 18b that extend from each side of the support block 11 and are attached to the inner wall 19 of the upper chamber portion 7. The bellows 18a, 18b are flexible to allow lateral vibration and load to be applied to the spherical upper sample 13 and to the disc-shaped lower sample 14 via the push rod 9, and to maintain a sealed pressure chamber 4 so that pressurized gas or vacuum is maintained in the chamber 4. The push rod 9 is coupled to an external vibrator (not shown) located within the housing 2 by a detachable push rod coupling 9a, which enables the spherical upper sample 13 to be driven into reciprocating motion.

[0020] The push rod 9 is attached to diametrically opposed load-bearing supports 25a, 25b by means of a support ring 25, so that weights can be suspended from the load-bearing supports 25a, 25b depending on the load that is desired to be maintained between the samples 13, 14 during testing.

[0021] The lower sample holder 15 is attached to a lower support block 20, which forms part of the lower chamber portion 8. Two thin disks 21a, 21b are attached to each of the corresponding block ends 22a, 22b at the center of the disks 21a, 21b, and the disks 21a, 21b are fixed to the inner surface of the lower chamber portion 8 at their circumferences. The disks 21a, 21b are axially flexible but radially rigid. The disks 21a, 21b act as flexible seals, allowing pressurized gas or vacuum to be maintained inside the chamber 4 on the inside of the disks 21a, 21b, while ambient pressure is maintained outside the chamber 4 on the outside of the disks 21a, 21b. The lower support block 20 is also attached to a high-rigidity force sensor 24 via a push rod 23. The relative stiffness of the force sensor 24 and the flexible disks 21a, 21b means that a significant proportion of the frictional force is applied to the force sensor. Since the combined configuration of disks 21a, 21b and force sensor 24 is completely elastic, the signal from the force sensor 24 is proportional to the frictional force applied to the lower sample 14. As described above, the lower sample holder 15 is supported at either end by two flexible disks 21a, 21b. Aside from the contact between the two samples 13, 14, there is no physical contact, so any frictional forces are transmitted through the two disks 21a, 21b. Compared to the force sensor 24 to which the lower sample holder 15 is coupled, the disks 21a, 21b have relatively low stiffness in the axial direction. The disks 21a, 21b serve as a means of sealing the pressure chamber 4, enabling pressures up to 10 bar or a vacuum to be maintained within the pressure chamber. If there is a vacuum in the pressure chamber 4 and no test fluid, heat can only be transferred to the lower sample holder 15 via the disks 21a, 22b and their spacers 26a, 26b (which act as supports requiring electrical insulation). Preferably, the disks 21a, 21b are made of nickel-plated beryllium copper (BeCu) and the spacer supports 26a, 26b are made of anodized aluminum—both are very good thermal conductors, and the anodization of the aluminum provides electrical insulation.

[0022] refer to Figure 5 8 , the lower chamber portion 8 includes a pressure bore 34 into which pressure lines 35 are fitted, enabling fluid under positive or negative pressure to be introduced into or removed from the pressure chamber 4. There are three pressure lines 35a, 35b, and 35c, which are arranged diametrically around the lower chamber portion 8. Pressure line 35a includes a pressure gauge 36 and a proportional relief valve 39. Pressure lines 35a and 35b include an actuated valve 37 for controlling the introduction or removal of fluid, and also include a safety relief valve 38.

[0023] The disks 21a, 21b are electrically insulated from the inner wall, for example, by spacers 26a, 26b, and an electrically insulating coupling 1 is provided between the push rod 23 and the force sensor 24, so that the entire sensor arrangement is electrically insulated. This allows current to be applied across the contact point between the samples to measure its resistance or to study the effect of different voltages or currents on the contact behavior.

[0024] The lower sample holder support block 20 includes a bore 28 to facilitate insertion of a temperature measurement probe 29 .

[0025] The canister lid 5, upper chamber portion 7, and lower chamber portion 8 form a sealed chamber 4, which is locked in place by four long screws 30. The entire assembly is attached to a heater block 31 by four short screws 32. The heater block 31 contains a cartridge heater 33 to allow the chamber 4 to be heated, and the temperature to be controlled by input from the temperature measurement probe 29 to a temperature controller 34.

[0026] By removing the four short screws 32 and loosening the force sensor connector 27 and the push rod connector 9a, the entire pressure chamber test assembly 3 can be removed from the test machine 1 while maintaining the pressure in the chamber 4 so that the test mixture can be within the pressure chamber 4 and away from the rest of the test machine 1.

[0027] The heater cartridge 34 in the temperature regulating block 31 may contain an electric heater or cooling element which, together with the temperature measuring probe 29 and the controller, enables testing at elevated or reduced temperatures. The temperature regulating block 16 is attached to a curved support designed to be rigid in all directions except the vibration direction of the upper sample 13, in which direction deflection is permitted.

[0028] Suitably, the lower sample holder 15 is in the form of a stainless steel trough to contain the test lubricant. The lower sample holder 15 in the form of a trough includes upright walls 16 to which the lower sample is clamped. The lower sample holder 15 can contain a small amount of test fluid or test grease, or can be dry contact, with the remaining volume of the pressure chamber filled with pressurized gas (which can be the test gas) or under vacuum.

[0029] Alternatively, the lower sample holder can be a flat plate onto which the lower sample 14 is clamped. The entire lower half of the pressure chamber 4 can then be filled with a test fluid that submerges the test sample contact points, and the volume above the test fluid is filled with a pressurized gas (which can be the test gas) or is under vacuum. The lower sample 14 can be coated with a test grease or can be dry contact when clamped to the flat plate, and the remaining volume of the pressure chamber is filled with a pressurized gas (which can be the test gas) or is under vacuum.

[0030] The device also allows for the measurement of the contact resistance between two samples. This resistance is determined by the degree of asperity-to-asperity contact between the samples and is a qualitative measure of the effectiveness of the lubricant in separating the samples.

[0031] During these measurements, the parameters of load and sample temperature and pressure can be varied by the methods described above.

[0032] Parts List:

[0033] 1-Test equipment

[0034] 2-Shell

[0035] 3 - Front

[0036] 4-Pressure chamber

[0037] 5-Removable cover

[0038] 6-Glass window

[0039] 7-Upper chamber part

[0040] 8-Lower chamber part

[0041] 9 - Putt

[0042] 9a - Push rod connector

[0043] 10 - Upper sample holder / first sample holder

[0044] 11-Support block

[0045] 12-Flat head screw

[0046] 13 - Upper sample / first sample

[0047] 14 - Lower sample / second sample

[0048] 15 - Lower sample holder / second sample holder

[0049] 16 - Upright Wall

[0050] 17 - Test Fluid

[0051] 18a, 18b - bellows

[0052] 19-Inner wall

[0053] 20-Lower support block

[0054] 21a, 21b - Plate

[0055] 22a, 22b - Block ends

[0056] 23 - Putt

[0057] 24-Force sensor

[0058] 25-Support ring

[0059] 25a, 25b - load-bearing support

[0060] 26a, 26b - Isolation pads

[0061] 27 - Insulating connector

[0062] 28 - Drilling

[0063] 29 - Temperature measurement probe

[0064] 30-long screw

[0065] 31 - Heater block

[0066] 32-Short screw

[0067] 33 - Heater cartridge

[0068] 34-Pressure Drilling

[0069] 35a, 35b, 35c - pressure lines

[0070] 36-Pressure gauge

[0071] 37 - Pressure Actuated Valve

[0072] 38-Pressure safety valve

[0073] 39 - Proportional relief valve

Claims

1. A test device (1) for measuring the friction properties of a fluid or the properties of a sample immersed in a fluid, the test device comprising: a first sample holder (10) adapted to hold a first sample (13) in a fluid being tested such that a first sample surface of the first sample (13) is in contact with a second sample surface of a second sample (14) in a second sample holder (15); Device for applying a measurable load between two samples, the test device (1) also comprising an oscillation drive device for oscillating a first sample holder relative to a second sample holder in a first direction, and a force measuring device (24) for measuring the friction force between the two samples, characterized in that the device (1) comprises a sealed pressure chamber (4), in which the first and second sample holders (10, 15) are located so that the test can be carried out under alternating pressures, and wherein a push rod (9) is provided which connects the oscillation drive device to the first sample holder (10) and provides an oscillating movement of the first sample holder (10) inside the pressure chamber (4) via a sealing device (18a, 18b), thereby maintaining the pressure in the pressure chamber (4) during the test.

2. The test device (1) according to claim 1, characterized in that The front portion (3) of the apparatus is arranged to contain the pressure chamber (4), and the front portion (3) is removable so that the pressure or vacuum is maintained when removed from the apparatus to another location away from the rest of the test apparatus (1).

3. The test device (1) according to claim 1, characterized in that The pressure chamber (4) comprises a removable cover (5) having a glass window (6).

4. The test device (1) according to claim 1, characterized in that The pressure chamber (4) comprises an upper chamber portion (7) and a lower chamber portion (8).

5. The test device (1) according to claim 1, characterized in that The second sample holder (14) includes an upstanding wall (16) which, if desired, receives a test fluid (17).

6. The test device (1) according to claim 1, characterized in that The first sample holder (10) is located in an upper support block (11) which is attached to a sealing device in the form of two metal bellows (18a, 18b) extending from each side of the support block (11) and attached to the inner wall (19) of the upper chamber part (7).

7. The test device (1) according to claim 1, characterized in that The push rod (9) is connected to an external vibrator (not shown) located in the housing (2) through a detachable push rod coupling (9a), and the external vibrator enables the first sample (13) to be driven to reciprocate.

8. The test device (1) according to claim 1, characterized in that The lower sample holder (15) is attached to a lower support block (20) which forms part of the lower chamber portion (8).

9. The test device (1) according to claim 1, characterized in that Two thin disks (21a, 21b) are attached to each of the corresponding block ends (22a, 22b) at the central area of the disks (21a, 21b), and the disks (21a, 21b) are fixed to the inner surface of the lower chamber part (8) in the circumferential area of the disks (21a, 21b).

10. The test device (1) according to claim 9, characterized in that The discs (21a, 21b) are axially flexible but rigid in the radial direction.

11. The test device (1) according to claim 9, characterized in that The disks (21a, 21b) act as flexible seals to allow pressurized gas or vacuum to be maintained inside the chamber (4) on the inside of the disks (21a, 21b) while ambient pressure is maintained outside the chamber (4) on the outside of the disks (21a, 21b).

12. The test device (1) according to claim 8, characterized in that The lower support block (20) is attached to a force sensor (24) via a push rod (23).

13. The test device (1) according to claim 12, characterized in that The relatively high stiffness of the force sensor (24) relative to the flexible discs (21a, 21b) causes a high proportion of the frictional force between the samples to be applied to the force sensor, and because the configuration of the combined discs (21a, 21b) and force sensor (24) is completely elastic, the signal from the force sensor (24) is proportional to the frictional force applied to the lower sample (14).

14. The test device (1) according to claim 10, characterized in that The disks (21a, 22b) are electrically insulated from the inner wall of the lower chamber portion (8).

15. The test device (1) according to claim 1, characterized in that An electrically insulating coupling (27) is provided between the push rod (23) and the force sensor (24), so that the entire sensor arrangement is electrically insulated.

16. The test device (1) according to claim 8, characterized in that The lower sample holder support block (20) includes a bore (28) to facilitate insertion of a temperature measurement probe (29).

17. The test device (1) according to claim 16, characterized in that The heater block (31) is provided to contain a cartridge heater (33) to allow the chamber (4) to be heated and the temperature to be controlled by input from the temperature measurement probe (29) to the temperature controller 34.

18. Testing device (1) according to claims 7 and 15, characterized in that The force sensor connector (27) and the push rod connector (9a), the entire pressure chamber test assembly (3) can be removed from the testing machine (1) while maintaining the pressure in the chamber (4), so that the test mixture can be in the pressurized chamber (4), away from the rest of the testing machine (1).

19. The test device (1) according to claim 4, characterized in that The lower chamber part (8) comprises at least one pressure borehole (34) in which a pressure line (35a, 35b, 35c) is installed.

20. The test device (1) according to claim 19, characterized in that An actuating valve (37) is contained in the pressure line (35a, 35b, 35c).

21. The test device (1) according to claim 19, characterized in that A pressure gauge (36) is included in the pressure lines (35a, 35b, 35c).

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