EP4647610A1

EP4647610A1 - Control system for an actuator cylinder

Info

Publication number: EP4647610A1
Application number: EP25173459.6A
Authority: EP
Inventors: Massimo Baraldi; Pierre Luigi Zaccarelli; Alberto PEDRAZZI
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2024-05-06
Filing date: 2025-04-30
Publication date: 2025-11-12

Abstract

The present invention relates to a system for actuating an actuator cylinder (10) of a working machine, said actuator cylinder having a first and a second chamber (11, 12), a piston (13) separating said first chamber (11) from said second chamber (12) configured to move an element connected thereto, said system comprising a first supply duct (20) of said first chamber (11) of said cylinder (10), a second supply duct (21) of said second chamber (12) of said cylinder (10), wherein said first supply duct (20) and said second supply duct (21) are connectable to a distribution valve (100) configured to control a supply operation and an exhaust operation of said first supply duct (20) and said second supply duct (21), wherein said first supply duct (20) is connectable to said second supply duct (21) by means of a regeneration duct (22) configured to a first valve (31) is positioned along said regeneration duct (22) configured to regulate the passage of fluid from said second supply duct (21) towards said first supply duct (20) based on a pilot pressure coming from said first supply duct (20) said system being characterised in that said system further comprises an exhaust duct positioned parallel to said second supply duct (21), wherein a second valve (34) is positioned along said exhaust duct configured to regulate a flow of fluid coming from said second chamber (12) and directed towards an exhaust, wherein said first and said second valve are configured to ensure that during the exit phase of said cylinder said second valve opens before said first valve.

Description

TECHNICAL FIELD

The present invention relates to the field of a control system for controlling an actuator cylinder in a hydraulic application.

BACKGROUND

Control systems for hydraulic cylinders for the movement of booms of machines such as telescopic handlers and cranes have evolved more and more over the years and require an ever-increasing number of functions to be fulfilled. Firstly, they require high safety so that, in the event of a duct breakage, the system is able to control the actuator cylinder and stop it, preventing a possible fall of the load. Secondly, high system stability is required so as to ensure that the user can control the system without generating sudden jerks, which could cause a sense of discomfort in the user. Furthermore, last but not least, it is required that such systems are efficient in terms of consumption, so as to avoid waste such as bottlenecks, and that the costs of manufacturing such systems are contained in terms of prices.
To enable this reduction in consumption and at the same time increase the speed of movement of the actuator cylinder, control systems with a regenerative function are normally used. An example of such a system is shown in figure 1.
As will be seen from the description below, valves with a regenerative function are used to increase the supply flow of a hydraulic cylinder and, consequently, its output speed. In this figure, one can see the cylinder comprising a first chamber 11 and a second chamber 12 separated by a piston 13, which is configured to move an element, such as for example a terminal portion of a crane, in correspondence with which a load can be connected. The system shown in the figure comprises a first supply duct 20 of said first chamber 11 of said cylinder 10, a second supply duct 21 of said second chamber 12 of said cylinder 10. Said first supply duct 20 and said second supply duct 21 are connectable to a distribution valve 100 configured to control a supply operation and an exhaust operation of said first supply duct 20 and said second supply duct 21. Said first supply duct 20 is connected to said second supply duct 21 by means of a regeneration duct 22 configured to allow a flow of fluid from said second chamber 12 to said first chamber 11 via said first and said second supply ducts 20, 21. A balancing valve 31 is positioned along said regeneration duct 22 which is configured to regulate the flow of fluid along said regeneration duct thanks to the pilot ducts which, as shown in the figure, allow it to "see" the pressure is present in both the first and second supply ducts. Furthermore, the one-way valve 32 allows to ensure a flow of fluid from the second to the first supply duct and to prevent reverse flow. The one-way valve 33 instead allows to ensure that all the fluid exiting the second chamber 12 is conveyed towards the first chamber and does not go towards the discharge of the distribution valve 100.
As can be seen from the diagram shown in the figure, which represents the state of the art, regeneration (regeneration flow rate Q _R) occurs using the fluid exiting from the "rod side" (i.e. from the second chamber 12) which is sent to the bottom side (first chamber 11) in addition to the flow rate Q _P supplied by the machine's supply system.
Specifying that Qp is the flow rate supplied by the distribution valve 100, Qr is the regenerated flow rate and Qt is the supply flow rate to the first chamber 11, the following flow rate balancing equation results: $Q_{T} = Q_{P} + Q_{R} .$
Where $Q_{T} = D^{2} \partial x .$ $Q_{R} = (D^{2} - d^{2}) \partial x$
Where, as shown in the figure, D represents the diameter of the piston on the bottom side and D represents the diameter of the rod and D ∂x represents the infinitesimal displacement of the piston.
By solving the three equations listed above, ∂x we will obtain that $\partial x = \frac{Q_{P}}{d^{2}}$
Therefore, rewriting the first equation we will get that $Q_{T} = Q_{P} \frac{D^{2}}{d^{2}}$
This equation was obtained by assuming that in the regenerative phase all the fluid coming from the second chamber 12 is conveyed towards the first chamber 11 through the regeneration duct 22, given that the one-way valve 33 is present on the duct 21.
The problem often encountered in the field is the lack of precision when fine output movements are required. Currently the solution used to mitigate this problem is given by the variable constriction that allows the slow piloting of the valve 31 that opens the regeneration duct. In particular, in an initial phase the valve 31 goes to constrict the pilot duct in such a way that the flow arriving towards the first chamber 11 is slightly constricted. This constriction is a purely temporal function.
However, this solution is often inadequate both due to the lack of variability in the delay setting and the variability of the oil temperature (which implies a different behavior of the machine depending on the operating conditions).
Another problem is the so-called "jump forward" which is widely known in the crane industry. The problem occurs after the cylinder has returned to the end of its stroke and the limiter on the distributor is activated. Subsequently, when an extension operation is started, a sudden advancement of the first extension occurs. Typically, this advancement is about 20-30 cm, but it occurs extremely quickly and is difficult to control. This happens because, after the cylinder has returned, a large amount of energy accumulates inside the volume of oil in the flexible hoses (which can be tens of meters long) due to the pressure set by the limiter. Consequently, it becomes necessary to discharge this accumulation before activating the regeneration system and starting the movement.
In the past, a new function has been developed which allows to solve these problems and which has been described in the patent application IT 10 2023 00000 9951 . This solution, while on the one hand has the advantage of solving the problems described above, on the other hand has the disadvantage that it requires an electronic regulation system, which may be too sophisticated for many applications and therefore the aim of the present invention is to develop a hydraulic solution capable of guaranteeing results similar to those described in the specified patent application.

SUMMARY

The present invention relates to a method of regulating an actuator cylinder according to the characteristics listed in claim 1.
The aim of the invention is achieved through a hydraulic system that allows to guarantee a variable regeneration ratio depending on the flow rate sent by the distributor and, therefore, on the required output speed. This solution allows to have a great definition and control in the slow movement phase and to exploit the maximum regeneration in the steady (fast) movement phase.

BRIEF DESCRIPTION OF THE FIGURES

The present invention will be described with reference to the attached figures in which the same numbers and/or reference signs indicate the same parts and/or similar and/or corresponding parts of the system.

Figure 1 shows a hydraulic circuit diagram of a state-of-the-art control system for an actuator cylinder with regeneration duct ;
Figure 2 shows a flow rate trend in a regeneration condition according to the state of the art;
Figure 3 shows a hydraulic circuit diagram of a control system for an actuator cylinder with regeneration conduit according to an embodiment of the present invention;
Figure 4 shows a flow rate trend in a regeneration condition according to an embodiment of the present invention.

DETAILED DESCRIPTION

Hereinafter, the present invention is described with reference to particular embodiments, as illustrated in the accompanying drawings. However, the present invention is not limited to the particular embodiments described in the following detailed description and depicted in the figures, but rather the embodiments described merely exemplify the various aspects of the present invention, the scope of which is defined by the claims. Further modifications and variations of the present invention will be apparent to one skilled in the art.
As will be clear from the remainder of this description, Figure 3 shows an example in which the present invention may be used. However, there are other examples of systems in which this invention may be used. It is therefore clear that the present invention is not limited to the particular application examples shown in the figures.
Figure 3 shows a diagram of a control system for an actuator cylinder 10 according to an embodiment of the present invention. The cylinder 10 is the same as shown in Figure 1 and therefore comprises a first and a second chamber 11, 12 and a piston 13 that separates said first chamber 11 from said second chamber 10. Said actuator cylinder is configured to allow the direct or indirect movement of an element, to which a load can be connected. In fact, such an actuator cylinder can be configured to move a mechanical arm such as the lifting arm of a telescopic handler or the arm of a crane, which is configured to be able to move loads (it is clear, however, that the load can be represented by the weight of the mechanical arm itself which is moved when empty and does not require the presence of an external body).
The first and second chambers 11, 12 are fed respectively by the first and second supply ducts 20, 21, which are connected to each other by means of the regeneration duct 22.
Along the first supply duct 20 is positioned a balancing valve 30 which is completely analogous to the one shown in figure 1. In particular, the balancing valve 30 comprises a one-way valve placed parallel to a balancing valve itself. We have spoken generically of a balancing valve since the one-way valve can be positioned inside the balancing valve itself. Therefore, two distinct and separate elements are not necessary but the two elements can be integrated into the same element.
Along the second supply duct 21 is positioned a one-way valve 33, which is configured so as to allow a flow of fluid coming from the distribution valve (not shown in the figure) to reach the second chamber 12 and likewise to prevent the flow of fluid in the opposite direction.
A balancing valve 31 is positioned along the regeneration duct 22, which is configured to regulate a flow of regeneration fluid coming from said second chamber 12 and directed towards said first chamber 11 through said regeneration duct 22. To prevent flow in the opposite direction, a one-way valve 32 is positioned. The elements described so far are already contained in the state of the art (as shown in figure 1).
The system according to the present invention further comprises a valve 34, which may be for example a balancing valve, which, as will be clear from the continuation of the description, allows the quantity of regeneration fluid flow to be regulated in the initial phase. This valve 34 is positioned along a discharge duct 23, which is configured so as to bypass the valve 33, thus also allowing a flow of fluid coming from the second chamber 12 to be conveyed to discharge towards the distribution valve 100. In the particular example shown in the figure, the balancing valve 34 is a two-position valve which is normally closed, thus obstructing a passage of fluid along the discharge duct 23, and which opens if piloted to open.
In the particular example shown in the figure, the discharge duct 23 connects a portion of the regeneration duct 22 between the second supply duct 21 and the balancing valve 31 with a portion of the second supply duct 21 between the one-way valve 33 and the distribution valve (not shown in the figure). However, this configuration is not binding and both ends of the discharge duct 23 could be directly connected to the second supply duct 21 and/or the discharge duct 23 could directly discharge to a tank and not necessarily to the second supply duct 21.
The system comprises a first pilot conduit 40, which comprises a first branch 41 and a second branch 42, and is configured to provide a first pilot pressure to valves 34 and 31 through first branch 41 and second branch 42, respectively. The first pilot pressure is collected along first supply conduit 20, preferably at a portion between valve 30 and the distribution valve (not shown).
The system shown in the figure further includes a second pilot conduit 43 configured to provide a second pilot pressure to valve 34. This second pilot conduit 43 collects a second pilot pressure along regeneration conduit 22 between valve 31 and first supply conduit 20.
As shown in the figure, the first pilot pressure acts towards an opening position of the valve 34, thus allowing a discharge of fluid from said second chamber 12 towards the distribution valve. The second pilot pressure instead acts in the opposite way towards a closing of the valve 34, thus preventing a discharge of fluid from said second chamber 12.
As shown in the figure, the balancing valve 31 also receives, in addition to said first pilot pressure, a third pilot pressure through a third pilot conduit 44. The third pilot conduit 44 receives the third pilot pressure from the second supply conduit 21 at a portion between the one-way valve 33 and the distribution valve. This third pilot pressure acts towards a closed position of the balancing valve 31 while the first pilot pressure acts towards an open position of the balancing valve 31 so as to open the flow of regeneration fluid along the regeneration conduit 22. It is kindly noted that in the particular example shown in the figure, the balancing valve 31, as designed, also receives a fourth pilot pressure from the second chamber 12, which will also tend towards an open position of the valve 31 in the event of an increase in pressure in the second chamber 12. However, this additional pilot pressure is not relevant to the purposes of the present invention.
In the following paragraphs, the operation of the previously described system will be briefly summarized, so as to increase clarity and better outline the advantages provided by the present invention.
In a first step, a request is received to move said element, wherein the movement of said element causes an increase in volume of said first chamber 11 and a consequent decrease in volume of said second chamber 12. This request occurs via the distribution valve (not shown) which sends a flow of fluid along the first supply conduit. The pressure inside the first chamber 11 tends to increase due to the resistance generated by the second chamber 12, due to the fact that a discharge of fluid from the second chamber 12 is at this time obstructed by the one-way valve 33 and the valve 34.
As mentioned, the first pilot conduit 40 receives the first pilot pressure from the first supply conduit 20 which is conveyed to the valves 34 and 31 through the branches 41 and 42 of the first pilot conduit 40 respectively.
When the first pilot pressure reaches a first predetermined value, valve 34 will tend to open, allowing a discharge of pressure and flow from the second chamber 12. At this time, valve 31 is still in the closed position. This is because valve 31 is configured to open at a higher pressure (for example, due to its pilot ratio) and/or because a restriction configured to reduce the first pilot pressure arriving from the first supply duct 20 is positioned along said second branch.
However, valve 34 is sized in such a way that, following its opening, the pressure inside the second chamber 12 tends to increase anyway. This is because the passage area of valve 34 is particularly restricted.
The pressure inside the second chamber 12 will therefore tend to increase further (and consequently the pressure in the first chamber 11 will also increase) causing an increase in the first pilot pressure along the branch 42, which will also tend to bring the valve 31 towards the open position. In the particular example shown in the figure, the fourth pilot pressure of the second chamber 12 will also tend to bring the balancing valve 31 towards the open position.
Thanks to the opening of the valve 31 it will be possible for the fluid contained inside the second chamber 12 to reach the first chamber 11 through the regeneration duct 22 and through the first supply duct 20, thus allowing regeneration.
Due to the fact that there is regeneration, the pressure along the second pilot line 43 will increase. The increase in the second pilot pressure will therefore cause a gradual closing of the valve 34, thus causing full regeneration of the fluid coming from the second chamber 12 towards the first chamber 11 without any discharge through the valve 34.
Thanks to the invention described above and in particular thanks to the presence of the valve 34 on the basis of the flow rate passing through said first duct 20 it is possible, as shown in particular in figure 4, to limit the flow rate in an initial phase. In fact, figure 4 shows, as well as figure 2, the trend of the two flow rates Q _P (dotted) and Q _T, where the dotted line shows the trend of Q _T according to the state of the art while the continuous line shows a possible trend of Q _T according to an embodiment of the present invention. Q _T increases proportionally with the flow rate Q _P arriving from the distribution valve 100. However, the proportionality varies over time and in particular increases with the increase in the flow rate Q _P . In fact, thanks to the valve 34, in an initial phase a part of the flow rate exiting the second chamber, instead of going to regenerate, is sent to discharge. At a second moment, after the opening of valve 31, part of the flow coming out of the second chamber 12 goes to regenerate while a small part is sent to discharge via valve 34. Only at a third moment, when valve 31 is completely open and valve 34 is completely closed again, does complete regeneration take place.
While the present invention has been described with reference to the embodiments described above, it is clear to one skilled in the art that various modifications, variations and improvements of the present invention may be made in light of the teaching described above and within the scope of the appended claims, without departing from the subject matter and scope of the invention.
Finally, those areas which are considered to be known by those skilled in the art have not been described to avoid overshadowing the described invention in an unnecessarily manner.
Accordingly, the invention is not limited to the embodiments described above, but is only limited by the scope of the appended claims.

Claims

Actuation system of an actuator cylinder (10) of a working machine, said actuator cylinder having a first and a second chamber (11, 12), a piston (13) separating said first chamber (11) from said second chamber (12) configured to move an element connected thereto, said system comprising a first supply duct (20) of said first chamber (11) of said cylinder (10), a second supply duct (21) of said second chamber (12) of said cylinder (10), wherein said first supply duct (20) and said second supply duct (21) are connectable to a distribution valve (100) configured to control a supply operation and a discharge operation of said first supply duct (20) and said second supply duct (21), wherein said first supply duct (20) is connectable to said second supply duct (21) by means of a regeneration duct (22) configured to allow a flow of fluid from said second chamber (12) to said first chamber (11) via said first and said second supply duct (20, 21), wherein along said regeneration duct (22) a first valve (31) is positioned configured to regulate the passage of fluid from said second supply duct (21) towards said first supply duct (20) based on a pilot pressure coming from said first supply duct (20) said system being characterised in that said system further comprises an exhaust duct (23) positioned parallel to said second supply duct (21), wherein along said exhaust duct (23) a second valve (34) is positioned configured to regulate a flow of fluid coming from said second chamber (12) and directed towards a discharge between a closed position, at which said second valve (34) prevents a passage of fluid along said exhaust duct (23), and an open position, wherein said first and said second valve (31, 34) are configured to ensure that during the regeneration phase the fluid is not exit of said cylinder, which corresponds to a phase in which said first chamber (11) increases its volume, said second valve (34) opens to a passage of fluid along said exhaust duct (23) through said second valve (34) before said first valve (31) opens to a passage of fluid coming from said second chamber (12) and directed towards said first chamber (11).
Actuating cylinder drive system (10) according to claim 1, wherein said system comprises a third valve (33) configured to allow a flow of fluid from said distribution valve (100) to be directed towards said second chamber (12) and to prevent flow in the opposite direction, wherein said exhaust duct (23) is configured to allow a bypass of said third valve (33) so as to allow a flow of fluid from said second chamber (12) to be directed towards said distribution valve (100).
Actuating system for an actuator cylinder (10) according to one of claims 1 to 2, wherein said system comprises a first pilot conduit (40, 41, 42) configured to supply a first pilot pressure to said first and said second valve (31, 34), wherein said first pilot pressure is collected along said first supply conduit (20).
Actuator cylinder drive system (10) according to claim 3, wherein said system further comprises a second pilot conduit (43) configured to provide a second pilot pressure to said second valve (34), wherein said second pilot pressure is collected along said regeneration conduit (22) between said first valve (31) and said first supply conduit (20).
Actuating system for an actuator cylinder (10) according to claim 4, wherein said first pilot pressure acts towards an opening of said second valve (34), thereby allowing a discharge of fluid from said second chamber (12), wherein said second pilot pressure acts towards a closure of said second valve (34), thereby preventing a discharge of fluid from said second chamber (12).