WO2024003932A1

WO2024003932A1 - Control of fluid flow in suspension dampers

Info

Publication number: WO2024003932A1
Application number: PCT/IN2023/050519
Authority: WO
Inventors: Saurabh Ramchandra Kulkarni; Darshan Vijay Wale
Original assignee: Tata Motors Passenger Vehicles Limited
Priority date: 2022-06-29
Filing date: 2023-06-02
Publication date: 2024-01-04

Abstract

A suspension damper (110) for a vehicle includes an inner tube (208), an outer tube (206), and a valve assembly (216) to allow flow of a fluid between the inner tube (208) and the outer tube (206). The valve assembly (216) includes a valve (302) having a channel (314) for flow of the fluid from the inner tube (208) to the outer tube (206). The valve assembly (216) also includes a pin (312) extending through an opening (602) in the valve (302). The pin (312) is hollow and has a fluid port (324) on a wall (322) thereof. The fluid may enter the pin (312) through the fluid port (324) and may flow from the inner tube (208) to the outer tube (206). A control mechanism (326) controls opening of the fluid port (324) based on a fluid pressure exerted on the valve assembly (216) by the fluid.

Description

CONTROL OF FLUID FLOW IN SUSPENSION DAMPERS

FIELD OF INVENTION

[0001] The present invention relates to suspension dampers, and more specifically related to controlling amount of flow of a fluid within a suspension damper.

BACKGROUND

[0002] A suspension system of a vehicle includes a resilient member, such as a spring, that couples a body of the vehicle with a wheel of the vehicle. The resilient member oscillates when the wheel travels on a bump, to minimize the impact felt on the body. An amplitude of oscillation of the resilient member depends on a bumpiness of the terrain on which the wheel travels. The suspension system also includes a suspension damper that serves to dampen the oscillations of the resilient member and to bring the resilient member to rest quickly by exerting a damping force. An amount of damping force exerted by the suspension damper is directly proportional to the rate of damping of oscillations of the resilient member. A high rate of damping of oscillations implies that the resilient member reverts to a rest state quickly, thereby forcing the wheel to quickly stop oscillating in a vertical direction quickly. Thus, the wheel travel in vertical direction is less for a high damping force. The amount of wheel travel is inversely proportional to the impact felt on the body.

[0003] The suspension damper includes an inner tube filled with a fluid (e.g., hydraulic oil), an outer tube, a piston disposed in the inner tube, and a piston rod partially disposed in the inner tube. When the resilient member oscillates, the inner tube and the outer tube reciprocate relative to the piston rod and the piston. The reciprocation causes movement of the fluid within the inner tube and movement of the fluid between the inner tube and the outer tube. The movement of the fluid progressively reduces amplitude of oscillations of the resilient member and brings the resilient member to rest. A damping force exerted by the suspension damper depends on an amount of resistance offered to the movement of the inner tube and the outer tube. The resistance to the movement of the inner tube and the outer tube, in turn, depends on the resistance offered to the movement of the fluid between the inner tube and the outer tube.

[0004] Generally, the resistance offered to the movement of the fluid between the inner tube and the outer tube, and consequently the damping force, cannot be varied. However, it may be preferrable to vary the damping force based on the bumpiness of the terrain. For example, when the vehicle is travelling on a relatively plain terrain at a high speed, a high damping force is preferred, as a high damping force ensures that the wheel travel is minimal. The minimal wheel travel increases ride stability, which may be necessary during travel at a high speed. Conversely, when the vehicle is travelling on a bumpy terrain, a low damping force is preferred. This is because the large wheel travel caused by the low damping force ensures that the impact felt on the body of the vehicle is minimal.

SUMMARY

[0005] A suspension damper for a vehicle includes an inner tube, an outer tube enclosing the inner tube, and a valve assembly to allow flow of a hydraulic fluid between the inner tube and the outer tube. The valve assembly includes a valve having a first channel through which the hydraulic fluid may flow from the inner tube to the outer tube. The valve assembly also includes a pin extending through a central opening in the valve. The pin is hollow and has at least one fluid port on a wall of the pin. The hydraulic fluid may enter the pin through the at least one fluid port and may flow from the inner tube to the outer tube. A control mechanism controls opening of the fluid port based on a fluid pressure exerted on the valve assembly by the hydraulic fluid.

BRIEF DESCRIPTION OF FIGURES [0006] The features, aspects, and advantages of the subject matter will be better understood with regard to the following description, and accompanying figures. The use of the same reference number in different figures indicates similar or identical features and components.

[0007] Fig. 1 illustrates a suspension strut, according to an implementation of the present subject matter.

[0008] Fig. 2 illustrates a suspension damper, according to an implementation of the present subject matter.

[0009] Fig. 3 illustrates a valve assembly, according to an implementation of the present subject matter.

[0010] Fig. 4 illustrates a valve assembly when a port gate is away from a closed position, according to an implementation of the present subject matter.

[0011] Fig. 5 illustrates a perspective view of a valve assembly, according to an implementation of the present subject matter.

[0012] Fig. 6(a) illustrates a perspective view of a valve assembly, according to an implementation of the present subject matter.

[0013] Fig. 6(b) illustrates a bottom view of a valve assembly, according to an implementation of the present subject matter.

DETAILED DESCRIPTION OF INVENTION

[0014] The present subject matter relates to controlling an amount of fluid that flows in a suspension damper. Using techniques of the present subject matter, damping force exerted by the suspension damper can be varied based on a terrain on which a vehicle travels.

[0015] In accordance with an implementation of the present subject matter, the suspension damper includes an inner tube, an outer tube enclosing the inner tube, and a valve assembly to allow a flow of a hydraulic fluid between the inner tube and the outer tube. In an example, the inner tube may be filled with the hydraulic fluid and may have a piston disposed therein. A piston rod coupled to the piston may be partially disposed in the inner tube and may be partially exposed outside of the inner tube. An exposed portion of the piston rod may be coupled to a body of the vehicle. The inner tube and the outer tube may be coupled to a resilient member, such as a spring, that is to oscillate along with a wheel of the vehicle, when the vehicle travels on a bump. The inner tube and the outer tube may reciprocate relative to the piston and the piston rod when the spring oscillates. The reciprocation may cause the hydraulic fluid to flow between the inner tube and the outer tube. For instance, during the reciprocation, when one end of the inner tube moves towards the piston, the hydraulic fluid is pushed towards the valve assembly and moves from the inner tube to the outer tube through the valve assembly. Conversely, when the end of the inner tube moves away from the piston, the hydraulic fluid is pulled towards the piston and moves from the outer tube to the inner tube.

[0016] The valve assembly includes a valve having a first channel through which the hydraulic fluid can flow from the inner tube to the outer tube. The valve assembly also includes a pin. The pin may be, for example, the pin that holds the components of the valve assembly together. The pin extends through a central opening (i.e. , an opening that passes through a centre) of the valve. The pin is hollow and has a fluid port on a wall thereof. The hydraulic fluid may enter the pin through the fluid port and may flow from the inner tube to the outer tube.

[0017] A control mechanism of the valve assembly controls opening of the fluid port based on a fluid pressure exerted on the valve by the hydraulic fluid. For instance, the control mechanism may keep the fluid port closed until a threshold fluid pressure and may progressively increase a degree of opening of the fluid port corresponding to an increase in the fluid pressure. The fluid pressure may be a pressure exerted by the hydraulic fluid on the valve assembly due to the movement of the end of the inner tube towards the piston. The fluid pressure increases with an increase in a piston force with which the end of the inner tube approaches the piston. The piston force increases with an increase in the amplitude of oscillation of the resilient member. That is, the fluid pressure increases with the amplitude of oscillation of the resilient member, which depends on a bumpiness of the terrain on which the vehicle travels. Thus, more hydraulic fluid is allowed to flow from the inner tube to the outer tube for a bumpy terrain, thereby reducing the damping force. In other words, the damping force reduces as the bumpiness of the terrain increases.

[0018] In an implementation, the control mechanism includes a port gate on which the fluid pressure is exerted and a closing member to maintain the port gate at a closed position, in which the port gate closes the fluid port. The closing member maintains the closed position of the port gate by exerting a closing pressure on the port gate. The closing pressure acts against the fluid pressure exerted on the port gate. The port gate moves away from the closed position, causing flow of the hydraulic fluid through the pin, when the fluid pressure exceeds the closing pressure. The closing member may be, for example, a spring.

[0019] The present subject matter adjusts the damping force exerted by the suspension damper in an efficient manner. The adjustment can be achieved without a manual intervention. By making the pin that holds the valve assembly together hollow and by allowing hydraulic oil to flow through the pin, the provision of an additional channel for flow of hydraulic oil is prevented.

[0020] The implementations herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting implementations that are illustrated in the accompanying drawings and detailed in the following description. It should be understood, however, that the following descriptions, while indicating preferred implementations and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the implementations herein without departing from the spirit thereof, and the implementations herein include all such modifications. The examples used herein are intended merely to facilitate an understanding of ways in which the implementations herein can be practiced and to further enable those skilled in the art to practice the implementations herein. Accordingly, the examples should not be construed as limiting the scope of the implementations herein.

[0021] Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the implementations herein. Also, the various implementations described herein are not necessarily mutually exclusive, as some implementations can be combined with one or more other implementations to form new implementations.

[0022] Referring now to the drawings, where similar reference characters denote corresponding features consistently throughout the figures, there are shown preferred implementations. Further, for the sake of simplicity, and without limitation, the same numbers are used throughout the drawings to reference like features and components. The implementations herein will be better understood from the following description with reference to the drawings.

[0023] Fig. 1 illustrates a suspension strut 100, according to an implementation of the present subject matter. The suspension strut 100, also referred to as a strut 100, may be used as part of a vehicle (not shown in Fig. 1 ), such as a car. The strut 100 may couple a body of the vehicle (also referred to as the vehicle body) with a wheel 102 of the vehicle. To this end, the strut 100 includes a body fixture 104 to be coupled to the vehicle body and a wheel fixture 106 coupled to the wheel 102. In an example, the body fixture 104 may be a structure on which the vehicle body is mounted and may be referred to as a body mount or a top mount.

[0024] The strut 100 may prevent vibrations occurring due to travel of the wheel 102 on bumps from getting transferred to the vehicle body, thereby improving rider comfort. For instance, when the wheel 104 is travelling over a bump, the wheel 104 may travel in a vertical direction, towards and away from the vehicle body. The strut 100 may prevent or reduce movement of the vehicle body in the vertical direction due to the travel of the wheel 104. To this end, the strut 100 may include a resilient member 108 that oscillates during the travel of the wheel. The resilient member 108 may be, for example, a spring that expands and contracts during the travel of the wheel 104. Hereinafter, the resilient member 108 will be explained with reference to a spring, and will be referred to as the spring 108. The spring 108 may be coupled to the body fixture 104. For example, a top end of the spring 108 may support the body fixture 104.

[0025] The strut 100 may include a suspension damper 110, also referred to as a damper 110, to dampen the oscillations of the spring 108 and to bring the spring 108 to rest quickly. The damper 110 may be coupled to the spring 108, such as a bottom of the spring 108. For example, the spring 108 may be seated on a spring seat 114 of the damper 110. The damper 110 includes a strut housing 112 having a piston (not shown in Fig. 1 ) disposed therein and filled with a hydraulic fluid, such as hydraulic oil. A piston rod (not shown in Fig. 1 ) is coupled to the piston and is partially disposed in the strut housing 112. A portion of the piston rod that is exposed outside of the strut housing 112 is enclosed by the spring 108 and a dust cover 116. The exposed portion of the piston rod may be coupled to the body fixture 104, and therefore, to the vehicle body.

[0026] During a vertical travel of the wheel 102, the spring 108 oscillates (i.e. , expands and contracts), with a top portion of the spring 108 (which is coupled to the body fixture 104) remaining substantially stationary. Further, the strut housing 112, which is coupled to the spring 108, reciprocates. The strut housing 112 may reciprocate relative to the piston rod and the piston. The reciprocation of the strut housing 112 may be resisted by the hydraulic fluid in the strut housing 112. The resistance gradually reduces amplitude of reciprocation of the strut housing 112 (and therefore, reduces the amplitude of oscillations of the spring 108), and eventually brings the spring 108 to rest. Thus, it can be seen that the strut 110 exerts a damping force on the spring 108 and dampens the oscillations of the spring 108. [0027] Fig. 2 illustrates the damper 110, according to an implementation of the present subject matter. The damper 110 includes the strut housing 112. The strut housing 112 may be substantially cylindrical. The strut housing 112 includes a first end 202 and a second end 204 in a height direction of the strut housing 112. The strut housing 112 includes an outer tube 206 and an inner tube 208 enclosed by the outer tube 206. In an example, the outer tube 206 may completely enclose the inner tube 208. The inner tube 208 may be filled with a hydraulic fluid, such as hydraulic oil. Hereinafter, the hydraulic fluid is explained with reference to hydraulic oil. Further, the hydraulic oil will be referred to as ‘oil’.

[0028] The inner tube 208 may have a piston 210 disposed therein. The piston 210 may be coupled to a piston rod 212. In an example, the piston 210 and the piston rod 212 may be formed integral to each other, such as manufactured as a single piece. In another example, the piston 210 may be bolted to the piston rod 212. A portion of the piston rod 212 may be disposed in the inner tube 208 and the remainder of the piston rod 212 may be exposed outside the inner tube 208. The piston rod 212 may extend outside the strut housing 112 through the first end 202. An end 214 of the piston rod 208 that is exposed outside the strut housing 112 may be coupled to the body fixture 104 (not shown in Fig. 2), as explained with reference to Fig. 1 . Further, the strut housing 112, and consequently the inner tube 208 and the outer tube 206, may be coupled to the spring 108 (not shown in Fig. 2). For example, as explained earlier, a bottom of the spring 108 may be seated on the spring seat 114 (not shown in Fig. 2) of the damper 110. The strut housing 112, and consequently the inner tube 208 and the outer tube 206, may also be coupled to the wheel fixture 106 (not shown in Fig. 2).

[0029] By virtue of the coupling of the strut housing 112 with the spring 108, the strut housing 112 reciprocates when the spring 108 oscillates. For example, the second end 204 move towards and away from the piston 210 and the piston rod 212. The reciprocation of the strut housing 112 may also be referred to as the reciprocation of the inner tube 208 and the outer tube 206.

[0030] During reciprocation of the inner tube 208, oil from one side of the piston 210 flows to the other side thereof through a piston hole 214. Further, during the reciprocation, when the second end 204 approaches the piston rod 212, a greater length of the piston rod 212 enters the inner tube 208. Accordingly, an oil-bearing capacity of the inner tube 208 reduces. In such a case, some amount of the oil is to be pushed out of the inner tube 208. Conversely, when the second end 208 moves away from the piston rod 212, a length of the piston rod 212 within the inner tube 208 reduces. Accordingly, an oil-bearing capacity of the inner tube 208 increases, and oil pushed out of the inner tube 208 can be accommodated in the inner tube 208. The outer tube 206 acts as a buffer to temporarily store the oil pushed from the inner tube 208. Accordingly, the outer tube 206 may also be referred to as a reserve tube. Further, the inner tube 208 may be referred to as a pressure tube. An upward movement of the strut housing 112 (i.e., the second end 204 approaching the piston 210) may be referred to as a compression stroke and a downward movement of the strut housing 112 may be referred to as a rebound stroke.

[0031] A valve assembly 216 disposed in the strut housing 112 regulates the flow of oil between the inner tube 208 and the outer tube 206. The valve assembly 216 may be disposed near the second end 204 of the strut housing 112. For example, the valve assembly 216 may be disposed between the piston 210 and the second end 204. Since the valve assembly 216 is disposed near a base (i.e., the second end 204) of the strut housing 112, the valve assembly 216 may also be referred to as the base valve assembly 216.

[0032] As will be appreciated, a resistance offered to the flow of the oil between the inner tube 208 and the outer tube 206 resists the reciprocation of the strut housing 112. Accordingly, a greater resistance to the flow of the oil between the inner tube 208 and the outer tube 206 causes a faster damping of reciprocations of the strut housing 1 12 (and consequently, a faster damping of oscillations of the spring 108) and vice-versa. The valve assembly 216 is capable of varying the resistance offered to the flow of the oil from the inner tube 208 to the outer tube 206, as will be explained below. [0033] Fig. 3 illustrates the valve assembly 216, according to an implementation of the present subject matter. The valve assembly 216 includes a valve 302, also referred to as a base valve 302 or a compression valve 302. The valve 302 may be made of, for example, sintered iron. A first valve disc 304 may be disposed between the valve 302 and the inner tube 208 and a second valve disc 306 may be disposed between the valve 302 and the outer tube 206 (not shown in Fig. 3). The first valve disc 304 may be disposed above and in contact with the valve 302. The first valve disc 304 may be biased against the valve 302 by a valve spring 308. The second valve disc 306 may be disposed below and in contact with the valve 302. The second valve disc 306 may be supported by a support washer 310. The valve assembly 216 may be held together by a pin 312 that passes through a central opening (not shown in Fig. 3) provided in the valve 302. The pin 312 may be made of, for example, steel.

[0034] The valve 302 may have a plurality of channels extending therethrough, through which the oil can flow between the inner tube 208 and the outer tube 206. For example, a first channel 314 is provided for oil to flow from the inner tube 208 to the outer tube 206 and a second channel 316 is provided for oil to flow from the outer tube 206 to the inner tube 208. Oil can enter the first channel 314 from the inner tube 208 through a first disc channel 318 in the first valve disc 304 and exit the first channel 314 through a second disc channel 320 in the second valve disc 306. Further, oil from the outer tube 206 can enter the second channel 316, push the first valve disc 304 upwards against the biasing force exerted by the valve spring 308, and flow to the inner tube 208.

[0035] The amount of oil that can flow from the inner tube 208 to the outer tube 206 through the first channel 314 is independent of the amplitude of reciprocations of the strut housing 112 (not shown in Fig. 3), and the amplitude of oscillations of the spring 108. Accordingly, the damping force exerted on the spring 108 cannot be varied using the first channel 314. To vary the damping force, another channel is provided for oil flow from the inner tube 208 to the outer tube 206, and the amount of oil that flows through this channel can be varied depending on the amplitude of oscillations of the spring 108. The other channel is formed in the pin 312 and the amount of oil flowing through this channel is controlled by a control mechanism, as will be explained below.

[0036] The pin 312 is made hollow, thereby providing a channel for the oil to flow in the body 321 of the pin 312. Further, on a wall 322 of the pin 312, which is in contact with an inner surface of the valve 302, a fluid port 324 is provided. The fluid port 324 will be hereinafter referred to as the oil port 324, as the fluid is explained with reference to oil. Through the oil port 324, oil can enter the body 321 and flow therethrough. A bottom of the pin 312 may be left open to the outer tube 206. Thus, oil flowing through the body 321 may exit the pin 312 from the bottom of the pin 312 and may enter the outer tube 206. The control mechanism 326 controls opening of the oil port 324 based on a pressure exerted on the valve assembly 216 by the oil, as will be explained below:

[0037] The opening of the oil port 324 may be controlled by a port gate 328 of the control mechanism 326. The port gate 328 may be, for example, a ball. The port gate 328 may be in a position at which it prevents oil from entering the oil port 324 and from flowing through the body 321. For example, the port gate 328 may cover the oil port 324. Such a position of the port gate 328 is referred to as a closed position of the port gate 328. When the port gate 328 moves away from the closed position, oil is allowed to flow through the oil port 324 and the body 321 . When the port gate 328 moves away from the closed position, it may be in a partially open position (in which a part of the oil port 324 is exposed for receiving the oil) or in a completely open position (in which whole of the oil port 324 is exposed. [0038] The port gate 328 may be disposed in a gate bore 330 in the valve 302. The gate bore 330 may be drilled in a portion of the valve 302 that is adjacent to the wall 322. The gate bore 330 may extend along the pin 312. Further, the gate bore 330 may be open to the inner tube 208 and may be in fluid communication with the inner tube 208. The gate bore 330 may include portions of different diameters - a first portion 332 in which the port gate 328 is disposed may have a larger diameter than a second portion 334 between the first portion 332 and the inner tube 208. Accordingly, the oil from the inner tube 208 first flows through the narrow second portion 334 and then reaches the port gate 328, which is disposed in the wider second portion 332. The first portion 332 may have a diameter substantially equal to that of the port gate 328, thereby preventing a lateral movement of the port gate 328 in the first portion 332. The oil arriving from the inner tube 208 may come in contact with a top of the port gate 328 and may pressurize the port gate 328, for example, to move downwards. That is, the oil pressurizes the port gate 328 to move away from its closed position. The pressure exerted by the oil on the port gate 328 may also be referred to as oil pressure or, more generally, as fluid pressure.

[0039] The control mechanism 326 includes a closing member 336 that strives to maintain a closed position of the port gate 328 by exerting a closing pressure on the port gate 328. The closing member 336 may be, for example, a spring and may be referred to as a closing spring. The closing member 336 may be disposed in the gate bore 330 and may surround the pin 312. The closing member 336 may be disposed in the first portion 332 and farther from the second portion 334 as compared to the port gate 328. That is, the port gate 328 may be disposed between the second portion 334 and the closing member 336. In an implementation, the closing member 336 may support a gate seat 338 and the port gate 328 may be seated on the gate seat 338. The gate seat 338 may be disposed in the first portion 332. The gate seat 338 may be ring-shaped and may surround the pin 312. [0040] The closing pressure exerted by the closing member 336 may act on the port gate 328 in a direction opposite the oil pressure, which is exerted by the oil coming from the inner tube 208. For example, the closing pressure may be a biasing pressure that biases the port gate 328 in an upward direction. Thus, the closing pressure tries to keep the port gate 328 in the closed position. In an example, when in the closed position, the port gate 328 may block the oil coming from the second portion 334 from proceeding to the first portion 332 and the oil port 324.

[0041] Until the oil pressure is less than the closing pressure, the port gate 328 remains in the closed position, thereby preventing the oil from entering the body 321 . Once the oil pressure exceeds the closing pressure, the port gate 328, the gate seat 338, and the closing member 336 are pushed downwards. That is, the port gate 328 moves away from the closed position and oil flows from the inner tube 208 through the second portion 334, the first portion 332, and the oil port 324 into the body 321 . Through the bottom of the pin 312, the oil leaves the pin 312 and enters the outer tube 206.

[0042] A degree of movement of the port gate 328 away from its closed position may depend on an amount by which the oil pressure exceeds the closing pressure - higher is the amount, greater is the movement of the port gate 328 away from its closed position. That is, a distance of the port gate 328 from the bottom of the second portion 334 increases with an increase in the oil pressure. Accordingly, the amount of oil that enters the body 321 increases with an increase in the oil pressure.

[0043] The oil pressure, which tends to move the port gate 328 away from the closed position, may be a function of the amount of oil reaching the valve assembly 216 from the inner tube 208. The amount of oil may, in turn, depend on an amplitude of oscillation of the strut housing 112 (and the spring 108). Further, the amplitude of oscillation may be higher when the vehicle travels on a bumpy terrain. Thus, the oil pressure increases with an increase in the bumpiness of the terrain on which the vehicle travels. Thus, oil flows through the body 321 when the vehicle travels on a bumpy terrain. Further, the amount of oil flowing through the body 321 increases with an increase in bumpiness of the terrain. In contrast, when the vehicle travels on a relatively plain terrain, the oil pressure tends to be less, and therefore, oil does not flow through the body 321 .

[0044] As explained above, oil may flow through the first channel 314 from the inner tube 208 to the outer tube 206 regardless of the oil pressure. Thus, a certain amount of oil flows from the inner tube 208 to the outer tube 206 regardless of the bumpiness of the terrain. Further, additional oil begins to flow through the pin 312 when the oil pressure increases beyond a threshold level. Thus, the amount of fluid flowing from the inner tube 208 to the outer tube 206 increases with an increase in the bumpiness. That is, the damping force produced by the damper 110 reduces with increase in the bumpiness of the terrain. Therefore, when the vehicle is travelling on a relatively plain terrain, a high damping force is produced, thereby providing ride stability and comfort, and when the vehicle is travelling on a bumpy terrain, a low damping force is produced, thereby minimizing impact of the bumps on the occupants of the vehicle.

[0045] Fig. 4 illustrates the valve assembly 216 when the port gate 328 is away from the closed position, according to an implementation of the present subject matter. The oil from the inner tube 208 (not shown in Fig. 4) can flow through the first channel 314, as illustrated by the oil flow 402. Such a flow may happen regardless of the oil pressure, as explained earlier. The oil may flow through the gate bore 330, press the port gate 328, and then flow through the oil port 324 and the body 321 , as illustrated by the oil flow 404. The oil flow 404 happens when the oil pressure exceeds the closing pressure exerted on the port gate 328 by the closing member 336, as explained earlier.

[0046] By making the pin 312 hollow and by allowing the oil to flow through the body 321 , the use of an additional component for carrying the oil is avoided. Further, the use of the pin 312 for transfer of additional oil ensures that the components required for regulating the transfer, such as the closing member 336 and the gate seat 338, are to have dimensions corresponding to that of the pin 312. For example, the closing member 336 and the gate seat 338 are to have diameters slightly larger than that of the pin 312, so as to surround the pin 312. Thus, the components required for regulating the transfer are compact. Still further, since a port gate of a small size can be used for closing the oil port 324, the biasing force to be exerted to keep the port gate at the closed position is small. Accordingly, a spring of minimal stiffness can be used for exerting the biasing force. Overall, the control mechanism 326 may be a compact and a cost-effective one.

[0047] Fig. 5 illustrates a perspective view of the valve assembly 216, according to an implementation of the present subject matter. The valve assembly 216 includes the pin 312 that extends axially through a centre of the valve 302. The first valve disc 304 is disposed between a top of the pin 312 and a top of the valve 302. The valve 302 may have a plurality of cutouts 502-1 , 502-2, 502-3, and 502-4 provided on a radial outer side thereof. The cut-outs allow exchange of fluid between a bottom of the outer tube 206 and a side of the outer tube 206.

[0048] Fig. 6(a) illustrates another perspective view of the valve assembly 216, according to an implementation of the present subject matter. Here, some components of the valve assembly 216, such as the pin 312 and the first valve disc 304, are not shown, to illustrate some other components of the valve assembly 216. The valve 302 includes a central opening 602 through which the pin 312 is to pass. A top of the valve 302 includes a gate bore opening 604 through which oil can be received in the gate bore 330 (not shown in Fig. 6(a)). The oil received from the gate bore opening 604 flows through the gate bore 330 and the top of the port gate 328, and enters the oil port 324 (if the port gate 328 is away from the closed position) through an inner wall opening 606. The inner wall opening 606 is provided on an inner wall 608, which is to be in contact with the pin 312.

[0049] In addition to the gate bore opening 604, a plurality of other gate bore openings 610-1 , 610-2, and 610-3 may be provided at the top of the valve 302, each of which is usable to receive oil into a corresponding gate bore (not shown in Fig. 6(a)). The oil received in a gate bore may be supplied to a corresponding fluid port of the pin 312. Each gate bore may have a port gate disposed therein to regulate flow of the oil into a corresponding fluid port of the pin 312. Accordingly, the control mechanism 326 pin may include a plurality of port gates and the pin 312 may include a plurality of fluid ports. [0050] At the top of the valve 302, a plurality of first channel openings 612- 1 , 612-2, ... , 612-8 may be provided for receiving oil from the inner tube 208 and supplying the oil to a corresponding first channel, such as the first channel 314 (not shown in Fig. 6(a)). The first channel openings 612 may be radially outside the gate bore openings 604 and 610. At the top of the valve 302, a plurality of second channel openings 614-1 , 614-2, ... may also be provided, for supplying oil to the inner tube 208 from a corresponding second channel, such as the second channel 316 (not shown in Fig. 6(a)). The second channel openings 614 may be radially outside the first channel openings 612.

[0051] Fig. 6(b) illustrates a bottom view of the valve assembly 216, according to an implementation of the present subject matter. Here, some components of the valve assembly 216, such as the pin 312, are not shown. The valve assembly 216 includes a plurality of gate bores, each having a port gate disposed therein. The port gates include the port gate 328 and port gates 650-1 , 650-2, and 650-3. The plurality of gate bores and the plurality of port gates are uniformly distributed around the circumference of the pin 312 (not shown in Fig. 6(b)). Each port gate is seated on the gate seat 338 (not shown in Fig. 6(b)), which surrounds the pin 312. By providing a plurality of gate bores for receiving oil for supplying to the body 321 of the pin 312, the amount of oil that can be allowed to pass through the body 321 can be increased.

[0052] Although the suspension strut 100 is explained with reference to a spring suspension (in which the resilient member 108 is a spring), the techniques of the present subject matter can also be utilized in an air suspension. In case of air suspension, the resilient member 108 may be a bellows.

[0053] The present subject matter enables adjusting damping force of a suspension damper based on bumpiness of a terrain on which a vehicle travels. The present subject matter achieves the adjustment of the damping force by adjusting a resistance to the movement of the strut housing during a compression stroke of the damper. The present subject matter allows continuous changes in the damping force for changes in the oil pressure, rather than discrete changes.

[0054] By using a pin of a valve assembly for carrying additional oil, the usage of an additional component for this purpose is avoided. Further, since the diameter of the pin is less, the components that are to be used for regulating flow of oil through the pin, such as resilient member and gate seat, may be made compact. Still further, by using small-sized port gates for regulating opening of the fluid ports, the stiffness of the spring to be used to exert closing pressure on the port gates can be made small. Therefore, small and inexpensive springs can be used.

[0055] The foregoing description of the specific implementations will so fully reveal the general nature of the implementations herein that others can, by applying current knowledge, readily modify and/or adapt for various applications without departing from the generic concept, and, therefore, such modifications and adaptations should and are intended to be comprehended within the meaning and range of equivalents of the disclosed implementations. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the implementations herein have been described in terms of preferred implementations, those skilled in the art will recognize that the implementations herein can be practiced with modification within the spirit and scope of the implementations as described herein.

Claims

CLAIMS:

1. A suspension damper for a vehicle, the suspension damper comprising: an inner tube; an outer tube enclosing the inner tube; and a valve assembly to allow flow of a hydraulic fluid between the inner tube and the outer tube, the valve assembly comprising: a valve having a first channel extending through the valve, wherein the first channel allows the hydraulic fluid to flow from the inner tube to the outer tube; a pin extending through a central opening in the valve, the pin being hollow and having at least one fluid port on a wall thereof, wherein the hydraulic fluid is to enter the pin through the at least one fluid port and is to flow from the inner tube to the outer tube; and a control mechanism to control opening of the fluid port based on a fluid pressure exerted on the valve assembly by the hydraulic fluid.

2. The suspension damper as claimed in claim 1 , wherein the control mechanism comprises: at least one port gate on which the fluid pressure is exerted; and a closing member to maintain the at least one port gate at a closed position in which the at least one port gate closes the at least one fluid port, to prevent flow of the hydraulic fluid through the pin, wherein the closing member maintains the closed position of the at least one port gate by exerting a closing pressure on the at least one port gate and wherein the at least one port gate moves away from the closed position, causing flow of the hydraulic fluid through the pin, when the fluid pressure exerted on the at least one port gate by the hydraulic fluid exceeds the closing pressure.

3. The suspension damper as claimed in claim 2, wherein the at least one port gate is disposed in a gate bore in the valve and wherein the gate bore is open to the inner tube, to receive the hydraulic fluid from the inner tube and supply the hydraulic fluid to the at least one port gate.

4. The suspension damper as claimed in claim 2, wherein the at least one port gate comprises a plurality of port gates circumferentially distributed around the pin, and wherein the suspension damper comprises: a gate seat on which the plurality of port gates is seated, wherein the gate seat surrounds and is in contact with the pin.

5. The suspension damper as claimed in claim 4, wherein the closing member is a spring supporting the gate seat.

6. The suspension damper as claimed in claim 2, wherein the at least one port gate is a ball.

7. The suspension damper as claimed in claim 1 , wherein the inner tube and the outer tube are part of a strut housing, the strut housing having a first end and a second end, and wherein the suspension damper comprises: a piston rod extending outside of the strut housing through the first end to be coupled to a body of the vehicle; and a piston disposed in the inner tube and coupled to the piston rod, wherein the valve assembly is disposed between the piston and the second end, and wherein the hydraulic fluid flows from the inner tube to the outer tube through the valve assembly in response to movement of the second end towards the piston.

8. A suspension strut for a vehicle, the suspension strut comprising: a suspension damper comprising: an inner tube; an outer tube enclosing the inner tube; a piston disposed in the inner tube, wherein the inner tube is to reciprocate relative to the piston, the reciprocation causing flow of a hydraulic fluid between the inner tube and the outer tube; a valve assembly to allow flow of the hydraulic fluid between the inner tube and the outer tube, the valve assembly comprising: a valve having a first channel extending therethrough, wherein the first channel allows the hydraulic fluid to flow from the inner tube to the outer tube; a pin extending through a central opening of the valve, the pin being hollow and having at least one fluid port on a wall thereof, wherein the hydraulic fluid is to enter the pin through the at least one fluid port and is to flow from the inner tube to the outer tube; and a control mechanism to control opening of the fluid port based on a fluid pressure exerted on the valve assembly by the hydraulic fluid; and a piston rod coupled to the piston and extending outside of the inner tube; a resilient member coupled to the inner tube; a body fixture coupled to the resilient member and to be coupled to a body of the vehicle; and a wheel fixture to be coupled to a wheel of the vehicle and coupled to the inner tube. A vehicle comprising: a body; a wheel; and a suspension strut coupling the body with the wheel, the strut comprising: an inner tube; an outer tube enclosing the inner tube; a piston disposed in the inner tube, wherein the inner tube is to reciprocate relative to the piston, the reciprocation causing flow of a hydraulic fluid between the inner tube and the outer tube; a valve assembly to allow flow of the hydraulic fluid between the inner tube and the outer tube, the valve assembly comprising: a valve having a first channel extending through the valve, wherein the first channel allows the hydraulic fluid to flow from the inner tube to the outer tube; a pin extending through a central opening in the valve, the pin being hollow and having at least one fluid port on a wall thereof, wherein the hydraulic fluid is to enter the pin through the at least one fluid port and is to flow from the inner tube to the outer tube; and a control mechanism to control opening of the fluid port based on a fluid pressure exerted on the valve assembly by the hydraulic fluid.