DK154449B - CONTROL UNIT FOR PRESSURE FLUID DRIVES - Google Patents

Description

Λ DK 154449 Β

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a control unit for pressure fluid driven devices which is of the type specified in the preamble of claim 1.

Although the invention is equally applicable in any control unit for pressure fluid driven devices, the control unit being based on a device having an internal valve body and a cooperating outer valve body, the invention has particular advantages for use in controllers for power driven control systems of the kind. used in off-road vehicles and the invention will be explained with reference thereto. More particularly, it will be appreciated that while the invention will be explained in connection with pivotal inner and outer valve bodies, it can also be applied to 15000,4.77

DK 154449B

2 valves with inner and outer valve bodies which are controlled by axial movements.

A control unit for a power-driven control system of the kind to which the invention relates is disclosed in United States Reissue Patent No. 25,126. The steering wheel of the vehicle is directly connected to the control unit, and when in the neutral (non-rotating) position, fluid may flow from the inlet opening, through the control valve to the outlet (or "open center system"), or the fluid from the inlet can be prevented from flowing through the valve ("closed center system").

When the steering wheel is turned in one direction from the neutral position, the valve is actuated and the fluid flows from the inlet opening, through the valve, to the fluid meter, and then to one working fluid opening, so that the pressurized fluid-driven device, i.e. the steering cylinder is moved. When the steering wheel is rotated in the opposite direction, the valve is rotated in the opposite direction and the fluid flows from the inlet opening, through the valve, then through the fluid meter in the opposite direction, and then to the second working fluid opening, so that the control force of the cylinder is moved in the opposite direction.

One of the problems that arises in conventional power-driven steering systems and in the control units used herein is that the steering wheel "wanders", i.e., that the steering position corresponding to the neutral position of the steering unit "wanders" or moves slowly in one or the other direction. plant operation. It is believed that the reason for this is primarily imbalance or asymmetry in the fluid flow paths, i.e., the fluid must pass through a longer flow path or be subjected to a greater flow resistance in one direction than in the other, so that internal leakage is primarily between " measured "fluid" and "return fluid" are different for the two control directions. This means that the fluid meter, which is a feedback means for the position of the pressurized fluid-driven device, is not able to continue to accurately display the position of the device, since the asymmetrical leakage causes the meter to get a greater "drift" in one direction than in the other, and hereby the said "walking" of the steering wheel is obtained. As used herein, the term "measured fluid" means fluid that is measured in the fluid meter on its way to or from the control cylinder. Term

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3 "return fluid" simply means fluid which has been displaced during the movement of the control cylinder and which returns to the valve and passes to the outlet opening (or reservoir opening).

In connection with the definitions of "measured fluid" and "return fluid" with respect to any particular control unit, it should be noted that the remainder of the fluid flowing through the valve with the inner and outer rotors has about the same pressure as the high-pressure "measured fluid", but it has not been measured, which is why it can be referred to as "non-measured high-pressure fluid".

In many of the conventional control valves with a device with inner and outer rotors, the openings or gates in the outer rotor which connect to and from working fluid openings and the associated notes or port channels in the inner rotor are designed and arranged in such a way that notes containing measured fluid and notes containing return fluid alternate between the contents, so that the length of the areas that form the boundary between measured fluid and return fluid, and thus the possibility of internal leakage therebetween, is greatly increased (cf. e.g., U.S. Patent No. 3,819,307).

It is therefore an object of the invention to provide the design of a control unit of the type initially indicated, in which the steering of the steering wheel is reduced by an improved design of the valve device with an outer and an inner valve body.

The above object is achieved by designing the control unit as defined in claim 1. Since the length of the flow path of the fluid flow from the inlet opening to the working fluid opening in question is substantially the same for movement of the valve bodies in one or the other direction from the neutral position, the internal leakage with respect to the flow of measured fluid is substantially the same in both directions, thereby reducing steering wheel travel.

Those skilled in the art will be able to find different ways of meeting the flow path lengths criterion set out in claim 1, but in particular the criterion can be met in a simple way by designing the control unit as set forth in claim 2, and such a design also offers production technical advantages.

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4

By designing the control unit as set forth in claim 3, it is achieved that the maximum possible distance, and thus the lowest possible leakage pressure gradient, is obtained between the channels which conduct measured high-pressure fluid and those channels which carry return fluid under low pressure.

By designing the controller as set forth in claim 4, it is achieved that the channels conducting unmeasured fluid under high pressure act as a pressure barrier which reduces the leakage pressure gradient of the channels carrying the measured fluid at high pressure to practically zero. the first fluid meter channel with the first working fluid channel when the control valve is in the first control position, and for connecting the second fluid meter channel with the second working fluid channel when the control valve is in the first control position. The first and second working fluid passageways are positioned opposite each other on and at approximately the same distance from the reference plane.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be explained in more detail with reference to the accompanying drawings, in which: FIG. 1 schematically shows a power driven steering system in a vehicle and a control unit in which the invention can be used; FIG. 2 is a larger-scale axial section through the one shown in FIG. 1 shows a schematic control unit; FIG. 3 and 4 are unfolded views of portions of the valve bodies according to the invention, shown on top of each other in their respective right- or left-hand positions, respectively. 3A and 4A are semi-schematic sections along line 3A-3A of FIG. 3 and line 4A-4A in FIG. 4, FIG. 5 is a side view of the control valve rotor used in the control unit; and FIG. 6 is a side view of the follow-up valve rotor used in the control unit.

steering gear

Pig. 1 schematically shows a power driven steering system for vehicles of the kind well known in the art and to which the invention may be applied. Such systems consist essentially of a steering wheel 11 in working communication with a control unit 13, in particular its control valve 15. The control unit 13 has an inlet opening 17, through which the control unit receives the full fluid flow of the system from a control unit.

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fluid source, such as e.g. a pump 19 which is connected to a reservoir 21 by means of a conduit 23. The control unit 13 also has an outlet opening 25 which is connected to the reservoir 21 through a conduit 27. To the control unit 13 there is attached a fluid meter 29, which stands in working connection with the control valve 15 to measure the fluid flow through a control cylinder 39 in response to the movements it performs as a result of the rotary movements of the steering wheel 11 and the control valve 15. The control unit 13 comprises a left-turn opening 31 and a right-turn opening 33, of which left-turn opening 31 fluid through a flow path 35 and the right-hand orifice 33 receive fluid through a flow path 37, the diagram of FIG. 1 shows the system in a right-turn state and the flow path 37 is shown connected to the fluid meter 29. The control cylinder 39 is actuated by the control unit 13 by means of conduits 41 and 43 connected to the left turn opening 31 and right turn opening 33. If desired, the control unit 13 comprise an auxiliary fluid opening 45 from which there is fluid connection to an auxiliary device 47 through a conduit 49. The auxiliary device 47 is also connected to the reservoir 21 through a conduit 51.

The control unit

FIG. 2 shows an axial section through the control unit 13, which section is laid in such a plane that none of the openings 17, 25, 31 or 33 are visible. The control unit 13 comprises a housing 53, an intermediate plate 55, the fluid meter 29, and an end plate 57. These parts are clamped together by a number of bolts 59 which are inserted into threaded holes in the housing 53 not shown.

The fluid meter 29 comprises an internally serrated member 61 which is held in relation to the intermediate plate 55 and the end plate 57 of the bolts 59. Inside the internally serrated member 61 is an eccentrically externally serrated member 63 having a centered manifold opening 65. The housing of the control unit 53 surrounds a generally cylindrical axial bore 67 in which the control valve 15 is pivotally mounted. At the front end of the housing 53 a recess 71 is provided against which rests an end cover 73 which is held in place by a retainer 75.

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The control valve 15 comprises a primary control valve body in the form of a control rotor 77, and a downwardly cooperating follow-up valve body in the form of a hollow follower rotor 79, which encloses the control rotor 77. The control rotor 77 ends at the front of a multifaceted 80 for interconnecting the control rotor 77 with a not shown. longitudinal end shaft which is connected to the steering wheel 11. The follower rotor 79 is deadly coupled to the movable portion of the fluid meter 29, the externally toothed member 63, by means of an intermediate shaft 81, the rear end of which bears a curved longitudinal head 83 which engaging the centered manifold opening in the externally toothed member 63, the axial movements of the intermediate shaft 81 being partially limited by a spacer 84 between the manifold head 83 and the end plate 57. The end of the intermediate shaft 81 opposite the fluid gauge 29 is formed as an end fork 85, through which a transverse pin 87 extends. The transverse pin 87 passes freely through pin slots 91, cf. FIG. 5, in the rotor 77 and engaging the pinhole 89, cf. FIG. 6, in the follower rotor 79 in a manner well known in the art and which is not part of the present invention. Located approximately at a right angle with the transverse pin 87, there are a plurality of leaf springs 88 which are adapted to seek to move the guide rotor 77 and the follower rotor 79 relative to each other toward their neutral position. Certain other details of the design and operation of such controllers, which do not form part of the present invention, can be more easily understood by review of the aforementioned United States Reissue - Patent No. 25,126, assigned to the one to whom the present invention is transferred.

FIG. 5 and 6 are side views of the control rotor and the follower rotor, respectively, on approximately the same scale as in FIG. 2. Both in FIG. 5 and in FIG. 6, there is shown a reference plane RP which is perpendicular to the axis of rotation of the control rotor 77 and the follower rotor 79, and which is plotted to facilitate the explanation of the invention.

The follower rotor 79 comprises a pair of diametrically opposite pegs 89 (only one of which is shown in Fig. 6) which is adapted to engage the pivot 87. Similarly, a pair of diametrically opposite peg slots are formed in the guide rotor 77 91 (only one of which is shown in Fig. 5), to allow the transverse pin to pass through guide rotor 77 without engaging with it except at maximum impact.

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In connection with the following description; with reference to FIG. 5 and 6, as well as the effect description with reference to FIGS. 3, 3A, 4 and 4A, it should be noted that many of the openings, gates, ducts, etc. is arranged mirror-symmetrically on both sides of the reference plane RP.

The parts in question will therefore be denoted by a reference number followed by an R or an L, to show that the part lies to the right and to the left of the reference plane, respectively, to the RP.

On the other hand, there are certain parts that are not matched by a part located on the other side of the reference plane, and these parts will be denoted by a reference number alone.

In the outer surface of the follower rotor 79, a centered circumferential groove 93 is formed, in which a number of openings 95 open.

On opposite sides of the plane RP, perimeter notes 97L and 97R are formed, which are connected to two sets of pressure ports 99L and 99R, respectively.

Located at greater distances from the reference plane RP, there are two sets of measuring openings 101L and 101R. Finally, in the follower rotor 79, two sets of working ports 103L and 103R are designed. It should be noted that for each set of gates or apertures in the illustrated embodiment, the distance along the circumference from one port or aperture to the next is substantially the same, and furthermore, although not all ports and apertures are shown, the embodiment shown is six of each, though the number may vary.

The control rotor 77 is formed in its outer surface with a pair of circumferential gauge notes 105L and 105R which are located at the same distance on either side of the reference plane RP. It should be noted that when the follower rotor 79 is positioned outside the guide rotor 77, these two parts in the axial direction will be in the same mutual position as shown in FIG. 5 and 6, with reference planes RP coinciding. Thus, the meter notes 105L and 105R will flow axially and are in fluid communication with the meter openings 101L and 101R, respectively. Axially inward (towards the reference plane RP), there are two sets of mutually spaced circumferential port channels 107L and 107R arranged from the gauge notes 105L and 105R, which are arranged to communicate with the pressure ports 99L and 99R when the control rotor 77 and the follower rotor 79 stand in a particular pivotal position, as will be explained in more detail with reference to FIG. 3 and 4, Axially outward from 8

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In the meter notes 105L and 105R there are two sets of working port channels 109L and 109R, each of which in the illustrated embodiment align axially with one of the gate channels 107L or 107R. The working port channels 109L and 109R are arranged to be connected to the working ports 103L and 103R, respectively, depending on a particular mutual rotational position of the control rotor 77 and the follower rotor 79. As was noted in connection with the follower rotor 79, the individual channels in each of the above sets of ducts preferably spaced apart at equal distances around the circumference, these distances being preferably the same as the distances between the gates and openings in the follow valve 79. Axially between the gauge notes 105L and 105R and tangentially between adjacent gate channels 107L and 107R, two sets are arranged in pairs. auxiliary port channels 111 and 113, the auxiliary port channels 111 being arranged to connect the pressure ports 99L with the auxiliary ports 95, while the auxiliary port channels 113 are arranged to connect the pressure ports 99R with the auxiliary ports 95 when the control rotor 77 and the follower rotor 79 are in their neutral position, as it is is shown and further described in then Norwegian Patent Application No. 4163/75.

In addition to the above-mentioned channels formed in the outer surface of the control rotor 77, in this rotor on each side of the reference plane RP a set of reservoir ports 115L and 115R, respectively, are distributed which are distributed along the circumference between the working port channels 109L respectively. 109R. Each of the reservoir ports 115L and 115R is arranged to flush and is in fluid communication with one of the working ports 103L and 103R, respectively.

FIG. 3 and 4, and the semi-schematic sections of FIG. 3A and 4A, show the state of right and left rotation respectively in the control unit 13 and the control valve 15. FIG. 3 and 4 show, unfolded and superimposed on each other, about 180 ° of both the steering rotor 77 and the follower rotor 79, these two parts being shown moved about 10 ° with respect to each other away from the neutral position as it occurs when the vehicle controlled. In general, the fully drawn lines show the gates and openings formed in the follower rotor 79, while the broken lines show the gates and channels formed in the guide rotor 77 and which are covered by the follower rotor 79. As shown schematically in FIG. 3A and 4A, 9 is formed in the control unit housing 53

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a plurality of channels connecting the control valve 15 to various openings in the control unit 13, e.g. pressure inlet opening 17, left and right turn openings 31 and 33, etc. Among the ducts formed in housing 53 there is an auxiliary duct 117 and a pair of pressure ducts 119L and H9R. In the housing 53, meter channels 121L and 121R are located opposite each other as well as working channels 123L and 123R. It is a particular feature of the present invention that not only the gates, apertures and channels formed in the control rotor 77 and in the follower rotor 79 are symmetrically arranged on each side of the reference plane RP, but also the connecting channels formed in the housing 53 can be symmetrically arranged , either in relation to the reference plane RP or the axis of rotation of the control valve 15, and at least such channels should be arranged such that the total flow path for one working direction (ie either a left turn or a right turn) has substantially the same length and flow resistance as the total flow path for the opposite working direction. In this way, the pressure drop along the flow path will be the same in both directions. In connection with FIG. 3 and 4, it should also be noted that for the sake of clarity, circumferential notes 93, 97L and 97R are not shown. However, it will be appreciated that because of the circumferential grooves 97L and 97R, the pressure ports 99L and 99R will always be in fluid communication with the pressure channels 119L and 119R, respectively, regardless of the rotational position between the control rotor 77 and the follower rotor 79.

The operation In the embodiment shown in FIG. 3, the fluid introduced through the inlet opening 17 flows through the pressure channel 119L, around the circumferential groove 97L and into the pressure ports 99L. When the control rotor 77 and the follower rotor 79 are in the position shown in FIG. 3, each of the pressure ports 99L flushes with one of the port channels 107L so that the fluid can flow therethrough, then to the gauge note 105L, through the meter openings 101L, and thence through the gauge channel 121 to the fluid meter 29. After the fluid has been measured by the fluid meter 29, it flows through the meter channel 121R, through the meter openings 101R and into the meter note 105R. From the meter note 105R, the fluid then flows into the working port channels 109,

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10, which now tangentially aligns with the working ports 103R so that the fluid can flow through them, then through the working channel 123R to the right-hand orifice 33 (cf. Fig. 1), from which the fluid flows through the conduit 43 to the steering cylinder 39. The fluid introduced into the cylinder 39 moves the piston. to the left, thereby displacing the fluid on its left side and forcing it back to the control unit 13 through the conduit 41 and into the control unit through the left turn aperture 31, from which it flows through the working channel 123L to the control valve 15. From here the flowing (unmeasured) fluid flows through the working ports 103L, then through the tangentially flushing reservoir ports 115L, then through the interior of the control rotor 77, and finally to the outlet opening 25.

In the embodiment shown in FIG. 4, the control rotor 77 and the follower rotor 79 have been rotated in the opposite direction relative to each other so as to form a flow path which runs essentially opposite of the flow path one for a right rotation and which is substantially the same length as this. The fluid from the inlet opening 17 flows through the pressure channel 119R, the circumferential groove 97R, through the set of pressure ports 99, then through the tangentially escape gate channels 107R to the gauge note 105R. From there, the fluid flows through the meter openings 101R, the meter channel 121R to the fluid meter 29, then to the meter channel 121L, into the meter opening 10IL to the meter note 105L, and then axially into the working port channels 109L. From the working port channels 109L, the fluid flows out through the tangentially flushing working ports 103L, through the working channel 123L to the left turn opening 31, and thence through the line 41 to the steering cylinder 39. The fluid displaced at the opposite end of the cylinder 39 flows through the line 43 back to the right turn opening 33 the working channel 123R to the control valve 15, then through the working ports 103R, and through the reservoir ports 115R to the interior of the control rotor 77, and thence to the outlet opening 25.

In connection with both the aforementioned working directions (i.e., both the right and left-turn modes), it is noted that not only are the flow paths symmetrical and therefore "balanced" with respect to the path length, but additionally, they are maintained through fluid flow.

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11, the fluid flowing and measuring fluid therein is axially separated from the flowing fluid. In FIG. 3 and 3A, it can be seen that the measuring note 105R, the port channels 107R and the working port channels 109R contain measured fluid, while the flowing fluid passes through the working ports 103L and the reservoir ports 115L at the valve and follower rotor. Virtually in between, the working port channels 109L, the gate channels 107L, the gauge note 105L, the measuring openings 10IL, the pressure ports 99L, the openings 95 and the pressure ports 99R, all of which contain non-measured high pressure fluid, which serves as a buffer between the measured fluid and the flowing fluid for the to reduce the tendency for leakage between them. A similar, but opposite, device for measured fluid, backflowing fluid and non-measured high pressure fluid is shown in FIG. 4 and 4A.

Claims (4)

1, Pressure fluid operated control unit with a) a housing (53), b) a control valve (15) disposed in the housing comprising a primary, rotatable control valve body (77) and a co-operating and rotatable follow-up valve body (79), which valve bodies can assume a neutral position relative to each other and have substantially coincident rotational axes; c) a fluid meter (29) comprising a movable measuring means (63) adapted to measure it through its motions through a pressurized fluid driven device (39) the volume of flowing fluid, and d) means (83, 81, 87, 89) for interconnecting the measuring means (63) with the follower valve body (79) so as to impart a sequential movement depending on the movement of the measuring means (63), e) the control unit comprises a pressure inlet opening (17), an outlet opening (25), and a first (31) and a second (33) working fluid opening for connecting to the pressure fluid driven device (39), the control valve body (77) and foals the valve body (79) interacts with the housing to form a first set of fluid channels (119R, 99R, 107R, 105R, 121R, 121L, 101L, 105L, 109L, 103L, 123L, see FIG. 4 and 4A) which fluidly pressurize the inlet opening (17) with the first working fluid opening (31) through the fluid meter (29) when the valve bodies are rotated relative to one another toward a first working position (Figures 4 and 4A) in one direction away from the neutral position, as well as a second set of fluid channels (119L, 99L, 107L, 105L, 101L, 121L, 121R, 101R, 105R, 109R, 123R, see Figures 3 and 3A), which puts the pressure inlet opening (17) in fluid communication with the second working fluid aperture (33) through the fluid meter (29) when the valve bodies are rotated relative to one another towards a second working position (Figs. 3 and 3A) in the opposite direction away from the neutral position, characterized by, f) the first and the second set of fluid channels is designed and arranged so that the length of the fluid flow path from the inlet opening to the working fluid openings is the same, regardless of the direction in which the valve bodies have been moved relative to each other away from the neutral one another. position. DK 154449B A control unit according to claim 1, characterized in that the first and second sets of fluid channels are arranged and configured so that, apart from the angle difference between the first and second working positions, they represent mirror images of each other in relation to an imagined plane (RP). ) which are perpendicular to the axis of rotation of the valve bodies (77, 79). A control unit according to claim 2, wherein certain of fluid channels in the first and second sets of fluid channels, respectively, can be caused to put the second (.33) or the first (31) working fluid opening in fluid communication with an outlet opening (25) when the valve ] the retainers have been rotated relative to each other toward the first and second working positions, respectively, characterized in that the fluid channels connecting the second and first working fluid openings respectively to the outlet opening (25) and the fluid channels connecting the fluid meter (29 ), with the first and second working fluid apertures, respectively, being disposed on opposite sides of the imagined plane (RP). Control unit according to claim 3, characterized in that the fluid channels connecting the pressure inlet opening (17) to the first and second working fluid openings, respectively, are substantially between the fluid channels connecting the second and first working fluid opening to the outlet opening ( 25), and the fluid channels connecting the fluid meter (29) to the first and second working fluid apertures, respectively.