CA1236495A

CA1236495A - Shock absorber having a controlled damping rate

Info

Publication number: CA1236495A
Application number: CA000478307A
Authority: CA
Inventors: Kenth Ohlin
Original assignee: Individual
Current assignee: Individual
Priority date: 1984-04-04
Filing date: 1985-04-03
Publication date: 1988-05-10
Also published as: JP2736866B2; IT1184377B; DE3563557D1; JP2591707B2; SE443622B; JPH07248039A; US4732408A; EP0175747B2; IT8520217A0; SE8401874L; JP2544106B2; JPS61502067A; EP0175747B1; JPH07110046A; EP0175747A1; AU4115285A; WO1985004698A1; SE8401874D0

Abstract

ABSTRACT OF THE DISCLOSURE:

A shock absorber is designed to be used in particular with a motor cycle or a motor car. The shock absorber is so arranged as to permit the variation of the shock absorbing capacity or the resistance of the shock absorber by means of control impulses from an external unit in the form of a computer. The shock absorber is of the kind which comprises a cylinder operating with a fluid or with fluid/gas. Inside the cylinder is a fixed piston which is provided with at least one passageway. In this passage-way fluid is able to flow from one side of the piston to its other side, and vice versa. The piston has built into it an organ capable of being controlled by the control unit and so arranged as to vary depending on the control impulses received from the control unit the cross-sectional area of the passageway, in so doing causing a variation in the aforementioned shock absorbing capacity.

Description

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TECHNICAL FIELD

The present ;nvent;on reLates to a means ;ntended for a shock-absorber ;n order to perm;t the variation of the shock--absorbing capacity of the shock-absorber by means of control ;mpulses from an external controL unit, for example in the form of or incorporat;ng a computer. The shock-absorber ;n th;s case ;s of the kind which comprises a cyl;nder operat;ng w;th flu;d or fluid/gas and arranged inside the cylinder 3 piston provided with at least one passageway via which fluid is capable of being transferred from one s;de of the p;ston to ;ts other s;de, and v;ce versa.

DESCRIPTION OF THE PRIOR ART
~ . _ Shock-absorbers are encountered in a var;ety of applications where the requirement exists to absorb forces from a mov;ng mass~ Oy way of example, ment;on may be made of shock-absorbers for motor veh;cles, for example motor cycles and motor cars, where the shock-absorber ;s f;tted between a wheel and the chass;s for the 2û purpose of contributing to the optimum jolt-free movement of the chassis, ;n spite of any ;rregular;t;es ;n the surface over wh;ch the veh;cle is be;ng dr;ven. Another example ;s prov;ded by the case ;n wh;ch rotat;ng masses wh;ch are also subject to centr;fugal forces requ;re to be prov;ded w;th shock-absorpt;on ;n relation to a sol;d surface.

Prev;ously d;sclosed ;s the f;tment of shock-absorbers w;th constant res;stance or shock-absorb;ng capac;ty. Also previously d;sclosed ;s the execut;on of the shock-absorber with replaceable or additional component parts to prov;de the opt;mum result w;th regard to the shock-absorb;ng capac;ty on each occas;on on which the Yeh;cle is driven~

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2 --Also previously disclosed is the provision of a variation in the shock absorbing capacity with the asistance of an external control unit which may take the form of or may incorporate a computer unit or calculator, etc. The aforementioned control unit can be supplied in this case with information rela-ting to the behaviour of the vehicle, which in turn is controlled by the actions of the driver.
Thus, for example, the control unit may be supplied with information in respect of the speed of the vehicle, the torque being transmitted by the engine, and any changes in speed and inclination, etc. With the help of this informa-tion, the control unit is able to calculate the optimum shock absorbing func-tion for the shock absorber at any given time and -to control the shock absorber in such a way that i-t will provide the shock absorption determined by calculation.

D CRIPTION OF' TIIE PRESENT INVENTION

TECHNICAL PROBLEM
In systems with an external control unit it is desirable to be able to achieve a technically simple construction for the shock absorber in which the variation function of the shock absorber is integrated wi-th the construction of the shock absorber as a whole. In the case oE motor cycles, for instance, it~is desirable to be able to avoid external components which must ~orm part of or must be connected to the shock absorber. Thus, the aim is to achieve a construction for the shock absorber which requires no external additions or other design changes because of the requirement for it to be provided with the aforementioned variation facility for its shock absorbing capacity.
According to -the present invention, there is provided a shock absorber including means for controlling "' .

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~.~3~'~95 the damping rate of said shock absorber in dependence on ex-ternal control signals applied to the shock absorbar, and comprising a cylinder, a piston arranged within the cylinder and provided with a passageway of variable area for controlling flow of a working fluid from one side of the piston to the other side thereof, and a controllable member incorporated within the piston and controlled by said external control signals to vary -the area of said passageway, said external control signals being supplied by a control unit which receives as inputs signals from a sensor associated with the shock absorber, said input signals being related to the instantaneous parameter information obtained from the piston, the value of said external control signals varying during the s-troke oE the piston at least in part as a function of said input signals.

SOLUTION

The object of the present invention is to propose a means which will solve this technical problem amongs-t others, and what may primarily be regarded as being charac-teristic of the novel means is that the piston is provided with an organ capable of being controlled from the afore-mentioned control unit and so arranged as -to vary depending on the control impulses received frorn the control unit the cross-sectional area of the passageway referred to by way of introduction, in so doing causing a variation to occur in the aforementioned shock absorbing capacity.
Further developments of the idea of inven-tion are based on, amongst other things, the construction of the contro~lable organ.
Preferrably, this is intended in an embodiment to be included in or to forrn an electrically controlled servo valve. 5aid valve receives an electrical control signal , .
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.~236'~5 - 3a -from the external control unit and initiates a force-exerting flow of fluid dependent upon the control signal, said fluid flow acting upon an organ for determining the size of the cross-sectional area oE the passageway.
The aforementioned further dev~elopments are also based on the manner in which a check valve arrangement mus-t be executed in order to comply with the fundamental concept outlined above.
Preferably, each direction of flow through the piston must be provided with its own pair of check valves.
Furthermore, in each of the directions of flow, fluid is capable of being conducted via two parallel channels. Thus, a valve in the controllable organ determines the flow oE a control fluid in the first channeL for the purpose of deter-mining the position of a membrane which is utili~.ed there.
Th~ membrano i8 in turn connected to a va:lve wh:ich determines -the flow of a master fluid in the other channel.
Preferably, the controllable organ is controlled from the external control unit via electrical connecting oxgans which in this case may incorporate one or more electrical conductors which extend between said piston and the outside of the shock absorber. The shock absorber is provided with sensor organs which ;transmit the necessary parameter information to the control unit. The afore-mentioned parameter information may consist of information relating to position, movemen~ and/or the direction of movement of the piston.
The control unit consists in the present case preferably of a -.

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computer unit. In the event of the shock-absorber being fitted to a mo~or vehicle, the computer unit is supplied ~ith information relating to the gas supply, the vehicle gearbox and/or the veh;cle brakes, etc.

ADVANTAGES

~y means of what i5 proposed above the shoc~-absorber is able to retain its neat construction with its comparatively small external volume, in spite of the introduction of the aforementioned fac;lity to vary the shock-absorbing capacity. Furthermore, it is poss;ble to achieve a reliable variation function in return for comparatively little power consumption, which ;s of great ;mportance above all for motor vehicles.

DESCRIPTION OF THE DRAWINGS
_, , A preferred embod;ment of a means exh;b;ting the s;gn;f;cant characteristic features of the invention is described below with simultaneous reference to the accompanying drawings, in which:

Figure 1 shows in side view a shock-absorber which operates with fluid/gas;

Figure 1a shows a sectional view on an enlarged scale ;n relat;on to Figure 1 the construction of a piston in the shock--absorber in accordance with Figure 1 and a first flu;d flow from the f;rst s;de of the p;ston to ;ts second s;de;

Figure 1b shows the construction of the p;ston in accordance w;th F;gure 1, but with a second fluid flow fro~ the second side to the first side of the piston; and Figure 2 shows ir, the form of a basic di3gram the construction of the electronic component for the shock-absorber in accordance with Figure 1.
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s ~EST MODE OF CARRYING OUT THE INV~NTION

In Figure 1 a shock-absorber is indir.ated by the reference designation 1 . The basic construction of the shock-absorber may be of a previously disclosed nature. An example of such a shock--absorber is the ~hlins 'Gas Shocks' shoc~-absorber sold on the open market. A shock-absorber of this kind may incorporate a cylinder 2 and arranged inside it a piston 3 with ;ts associated piston rod 4 . Both the sylinder 2 and the piston rod 4 are proYided with seatings 5 and 6 for a coil spring 7 . The cylinder 0 i5 provided with attachment organs 8 for securing it to a chassis, indicated here symbolically by the reference designation 9 . The piston rod is provided at its free end with a corresponding attachment 10 for securing it to an organ, for example a wheel, indicated here symbolically by the reference designation 11 .
The seating 6 follows the movement of the piston rod.

In addition to the fixed p1ston 3 the shock-absorber illustrated in Figure 1 is provided ~ith a moving piston 12 , which has one of its sides 12a facing towards a fluid 13 present inside the cylinder and its other side 12b facing towards a gas 14 present ins;de the cylinder. The gas side of the operating cylinder is connected to an accu~ulator 15 via a connection 16 .

Since the basic function of the shock-absorber is in itself already very familiar, it is not proposed to describe it in any greater detail here. All that need be established is that the fixed piston

3 in accordance uith Figure 1 is provided with transcurrent passageways which make it possible for a fluid on one side 3a of the piston to pass ~hrough the piston to its other side 3b , and vice versa. The shock-absorption effect provided by the shock--absorber occurs, amongst other things, because of the presence of the aforementioned fluid passageway which acts as a constriction between the sides 3a and 3b of the piston~

In accordance with the idea of invention, the aforementioned ~LZ3~ 95i fLuid passage~ay must be variabLe. For this purpose a controLlabLe organ is so arranged as to vary clepending on controL i~puLses received from an external control unit not shown in Figure 1 the cross-sectionaL area of the passageway between said s;des 3a and 3b of the piston. The controL organ in the typical embodiment sho~n here is o-F the kind which is capabLe of being controlLed by means of electrical signals from said control unit. ~he controLlable organ aLso operates with a servo function so that smaLL controL
signaLs are abLe to cause and actuate the variation in the passageway. In the typical embodiment the controllable organ incLudes a control vaLve 17 , preferably in the form of a convent;onal soLenoid vaLve. The winding 18 in said solenoid valve is connected to said control unit via wires 1~ , being two in number in the typical embodiment shown.

Each direction of flow from one side to the other of the piston 3 is provided with ;ts own pair of check valves. Thus the d;rection of flow from side 3a to side 3b is provided with the check valves 20 and 21 . The other direction of flow is provided with the pair of check valves 22, 23 . Two parallel flow channeLs 24, 25 and 26, 27 are arranged in said pairs of check vaLves.
In addition the piston is provided with an internal space 28 , inside which is arranged a membrane 29 . To the membrane there is preferabLy secureLy attached a valve 30 . Said valve is arranged in the flow channel 24, 25 which forms part of the main passageway between the sides 3a and 3b of the piston. A needle 31 in the solenoid valve is arranged in the flow channel 26, 27 which forms a control passageway for the servo function of the controlLable organ.

If, for exampLe, the fluid pressure on side 3a exceeds the fLuid 3û pressure on side 3b of the piston, fluid will flow from the check valve 20 via said passageways 24, 25 and 26, 27 as far as and then out through the check valve 21 depending upon the manner in which the needle 31 is regulated. A fluid flow corresponding to ; the setting of the needle w;ll be formed in the channel 26, 27 .

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A force corresponding to the flow will act upon the membrane 29 , ~hich in turn will regulate the valve 30 in the channel 24, 25 .
If the needle 31 is actuated by the winding 18 so as to close the passageway 26, 27 fully, no control flo~ ~ill occur and the valve 3û will keep the channel 24, 25 completely closed~ A
small effect ùpon the needle will give rise to a smaLl control flow, which in turn will produce a correspondingly smalL effect on the membrane in a downward sense as shown in the Figure, allowing this to open the valve 30 in the channel 24, 25 . A
maximum effect on the needle 31 will produce a maximum control flow and a correspondingly maximum effect on the membrane and the valve 30 , which will permit a maximum flow in the main channel 24, 25 , and so on.

In the case of positive pressure be;ng exerted on the s;de 3b of the piston ;n relat;on to the s;de 3a , the pa;r of check valves 22, 23 will enter ;nto effect instead. Their fucnt;on w;ll be equ;valent to that descr;bed above, but w;th the d;fference that the d;rection of flow in the main channel 24, 25 will be the opposite. The direction of flow from side 3a to side 3b is indicated by the arrows 32 and 32' in Figure 1a, whereas the opposite direction of flow is indicated by the arrows 33, 331 in Figure 1b. The direction of fiow in the control channel is indicated by the arrows 34, 34' for both the flows referred to above in accordance with Figures 1a and 1b.

The aforementioned membrane 29 is flexibly supported inside the space 28 by means of moving attachments 29a . These attachments may consist of suspension spring mountings of a previously disclosed kind, for example of a plastics material which is sufficiently strong to w;thstand the flu;d in question, which may take the form of hydraul;c o;l. The sprung mount;ng of the membrane 29 is in ; this case so executed that sealing is provided between the lower and upper surfaces of the membrane in such a way that the negative pressure produced by the control pressure is able to act upon the membrane in accordance ~ith what has been stated above. The ~ . .

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aforementioned pairs of check valves 20~ 21 and 22, 23 may take the form of check valves of a previously disclosed kind. The passageways or channels referred to above can be provided by bores in the piston material, said bores being executed in a prev;ously disclosed ~ashion.

The wire or wires 19 in the case illustrated is/are routed inside a central channel 4a in the Piston rod 4 . It is in actual fact also possible to install the conductor or conductors on the outside of ~he piston rod 4 . In Figure 1 the outlet for the condùctors 19 is represented by a side channel 35 . The manner in ~hich the conductors are suspended shall be executed in such a ~ay as to provide sufficient free play to permit the maximum relative movement to take place between the piston rod and the cylinder.
This suspension of the conductors may be executed in a prev;ously disclosed fash;on without wear being caused to the conductors concerned.

In accordance with the above, the shock-absorber shall be capable of transmitting a signal back to the aforementioned external control unit. This signal shall preferably inform the externaL control unit of the posit;on in wh;ch the shock-absorber is situated, that is to say the relative positions of the piston and the operating cylinder. This information is utilized by the external control unit in order to determine the speed of the movements bet~een the chassis 9 and the unit 11 , ahd the length of the suspension travel remaining until the respective end positions are reached, etc. The return signal may suitably be transmitted via add;tional conductors 36 which may be one, two or more in number. In the typical embodiment shown an organ 37 is arranged for this purpose on the end surface 2a of the cylinder 21 . Said organ }7 may be of a previously disclosed kind which provides information in respect of the speed of the relative movements of the piston and the cylinder. The cylinder may also be fitted with end position sensors 38 connected via conductors 38a to the external control unit. Only one end position sensor is shown in the Figure in the interests of clarity.

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The external unit referred to above m3y take the form of 2 mirrocomputer of a previously disclosed kind. The microcomputer is sho~n in Figure 2 and may be installed in a su;table location - on the vehicLe. An example of the type of computer wh;ch may be used is the microcomputer sold on the open market by Motorola under the reference 6~05. The microcomputer is identified ;n Figure ~ by the reference designation 39 and comprises in a previously disclosed fashion a CPU 40 with its associated memories, for example ROM and RAM memories arranged in the same chip. The program which controls the shock-absorber is entered into the ROM memory. This memory can also contain stored constants holding the information required by the program for the control functions in question. Furthermore, the RAM memory may be used for the random storage of calculation variables. The electronic equipment also ;ncludes a current amplifier 41 of a previously disclosed kind. This amplifier is of the STD type and performs the task of providing the controllable organ 17, 18 referred to above with control signals. The current amplifier may be regarded as an adapter c;rcu;t for matching the power requirement of the shock--absorber to the power output of the microcomputer. The po~er supply to the microcomputer is provided from the electrical generating organ 4Z of the vehicle. The microcomputer is connected to one or more organs which are able to provide ;nformation in respect of the behaviour of the vehicle, as determined by the driver. One example of an organ wh;ch prov;des information ;s a gas supply system 43 which, by means of a valve 44 0 controls the supply of fuel ;n a fuel l;ne 45 .
Another example ;s prov;ded by those organs of the vehicle ~hich give informat;on about ;ts speed; th;s may be the gearbox 46 of the veh;cle, in which case ;nformat;on can be obtained both from the pos;t;on of the gear lever 47 and from rotating units inside the gearbox. A third information-providing organ wh;ch may be of interest ;n this context is one or more of the brakes 48 of the veh;cle. Each of the organs 43, 46 and 48 is fitted with one or more sensors 49, 5û to provide the informat;on in quest;on.
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In the Figure the control signal from the microcomputer 40 to the shock-absorber is indicated by i~ , whilst the return signal from the shock-absorber to the microcomputler ;s indicated by i2 .

With the heLp of the aforementioned sensor, information is supplied S to the microcomputer; on the basis of this information the computer is then abLe to work out, for exampLe, the speed of the vehicLe, the torque being transmitted by the engine, and any change ir, speed (acceLeration or retardation), that is to say the behaviour of the vehicLe occasioned by the infLuence of the driver upon it. With the heLp of the aforementioned quantities or parameters the microcomputer is abLe by controlling the controLLable organ to adjust the resistance or the shock-absorbing capacity of the shock-absorber so as to achieve the optimum function at any given moment. The speed at ~hich information is transmitted between the lS microcomputer and the shock-absorber can be high, and nay, for example, reach 1ûO000 pieces of information per second. The execution and number of the sensors used in various applications may vary ~ithin ~ide Limits. The objective, however, is to provide the microcomputer at aLL times with sufficient information in respect of the actions or intentions of the driver as to be abLe to utilize the avaiLabLe performance of the vehicLe.

Thanks to the means described above it is possible to Link the resistance of the shock-absorber to this performance. The resistance of the shock-absorber need no Longer be a compromise between a number of diFferent factors specified at the time of manufacturing the shock-absorber, but may now be optimized on a continuous basis~ This means that considerabLe improvements can be achieved in road-holding in many different respects, for example one or more, or aLl of the following funct;ons: better braking ability, better acceleration and/or better cornering abiLity, etc.

; The aforementioned sensor organs may incorporate code disc organs38b on the outside of the piston rod 4 . The positions of said code discs can be scanned by means of said organs 37 , for example with the help of photc~transistor organs.

As an alternative to, or in addition to the sen60r organs 37, 38, the sensing of the posl~ion and/or the speed o~ the pistlon in relation to the cylinder 2 csn be performed by monitoring the pressure by means of a pressure-monitoring organ 51 connected to the external control unit via conductors 52, for example two in number. The orgaD 51 can be of a previously disclosed kind. The variations in pressure due to the relative movements between the piston and the cylinder 2 are monitored at very closely-spaced intervals (see above) by the microcomputer~ which is able in this way to calculate the speeds/positions of the piston relative to the cylinder.

The piston 12 is positioned inside the cylinder 2 if the accumulator 15 is not present. If the acc~ulator 15 i9 present, ~hen this will instead constitute the moving piston 12', in which case the piston 12 In the cyllnder may be omltted. The pressure organ 51 is positioned inside the cylinder 2 if the accumulator is not present.

The solenoid valve 17 is positioned in a recess 53 (Figure lb) which is covered by a combined covering and retaining organ 54 (Figure la). The piseon also exhibits a parting plane, and the parts of the piston are held together in a previously disclosed, but not illustrated, fashion, for example by means of bolts.

The control organ has a protected position inside the piston.
It is not exposed for the main fluid between the upper and under sides of the piston. The control organ is able to control the control passage essentially independent of the pressure difference between the upper and under surfaces of the piston, at least in the normal operating conditions.

The invention is not restricted to the e~bodiment shown above by way of example, but may undergo modifications within the context of the following Patent Claims and the idea of invention.

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A shock absorber including means for control-ling the damping rate of said shock absorber in dependence on external control signals applied to the shock absorber, and comprising a cylinder, a piston arranged within the cylinder and provided with a passageway of variable area for controlling flow of a working fluid from one side of the piston to the other side thereof, and a controllable member incorporated within the piston and controlled by said external control signals to vary the area of said passage-way, said external control signals being supplied by a control unit which receives as inputs signals from a sensor associated with the shock absorber, said input signals being related to the instantaneous parameter information obtained from the piston, the value of said external control signals varying during the stroke of the piston at least in part as a function of said input signals.

2. Shock absorber as claimed in Patent Claim 1, wherein said controllable member forms part of an electri-cally actuated servo valve and influences a fluid flow which acts upon an organ for determining the size of the cross-sectional area of the passageway.

3. Shock absorber as claimed in Patent Claim 1, wherein each of the directions of flow through the piston is provided with its own pair of check valves.

4. Shock absorber as claimed in Patent Claim 2, wherein each of the directions of flow through the piston is provided with its own pair of check valves.

5. Shock absorber as claimed in Patent Claim 1, wherein in each of the directions of flow through the piston fluid is capable of being conducted via two parallel channels, a valve actuated by said controllable member determining the flow of fluid in a first channel for the purpose of determining the position of a membrane, and a valve connected to the membrane determining the main flow of fluid in the other channel.

6. Shock absorber as claimed in Patent Claim 2 or 3, wherein in each of the directions of flow through the piston fluid is capable of being conducted via two parallel channels, a valve actuated by said controllable member determining the flow of fluid in a first channel for the purpose of determining the position of a membrane, and a valve connected to the membrane determining the main flow of fluid in the other channel.

7. Shock absorber as claimed in Patent Claim 1, wherein the controllable member is connected to the control unit via an electrical connecting organ.

8. Shock absorber as claimed in Patent Claim 2, 3 or 5, wherein the controllable member is connected to the control unit via an electrical connecting organ.

9. Shock absorber as claimed in Patent Claim 7, wherein the electrical connecting organ incorporates at least one electrical conductors which extend between said piston and the outside of the shock absorber.

10. Shock absorber as claimed in Patent Claim 1, wherein said shock absorber is fitted to a motor vehicle, and said control unit receives information from organs capable of influencing the behaviour of the vehicle.

11. Shock absorber as defined in Claim 10, wherein said motor vehicle is a motor cycle.

12. Shock absorber as defined in Claim 10, wherein said motor vehicle is a motor car.

13. Shock absorber as defined in Claim 10, wherein one of said organs capable of influencing is an accelerator.

14. Shock absorber as defined in Claim 10, wherein one of said organs capable of influencing is the gearbox of the vehicle.

15. Shock absorber as defined in Claim 10, wherein one of said organs capable of influencing is at least one brake of the vehicle.

16. Shock absorber as defined in Claim 10, wherein said organs capable of influencing are the gearbox of the vehicle and at least one brake of the vehicle.

17. Shock absorber as claimed in Patent Claim 5, 7 or 9, wherein said shock absorber is fitted to a motor vehicle, and said control unit receives information from organs capable of influencing the behaviour of the vehicle.

18. Shock absorber as claimed in Patent Claim 1, wherein said sensor comprising a pressure-sensing organ is so arranged as to sense any changes in the pressure in the fluid produced by relative movements between the piston and the cylinder.

19. Shock absorber as defined in Claim 18, wherein said fluid comprises gas.

20. Shock absorber as claimed in Patent Claim 1, wherein the control unit monitors said sensor at closely-spaced intervals.

21. Shock absorber as defined in Claim 10, wherein the fregnency of said intervals is 100 000 times per second.

22. Shock absorber as claimed in Patent Claim 9, 10 or 18, wherein the control unit monitors said sensor at closely-spaced intervals.