WO2008115113A1

WO2008115113A1 - Method and device for the control of a rock drilling machine and a rock drilling machine

Info

Publication number: WO2008115113A1
Application number: PCT/SE2008/000168
Authority: WO
Inventors: Jonas Sinnerstad
Original assignee: Atlas Copco Rock Drills AB
Current assignee: Epiroc Rock Drills AB
Priority date: 2007-03-16
Filing date: 2008-02-29
Publication date: 2008-09-25
Anticipated expiration: 2009-09-16
Also published as: JP2010521603A; JP5393490B2; EP2122125A4; EP2122125B1; SE0700662L; SE530984C2; EP2122125A1

Abstract

A method and a device for controlling the feeding on a feed beam (3) of a to and fro movable rock drilling machine (2), which includes a percussive device and a rotation motor providing a rotation moment, wherein a parameter related to the rotation moment is monitored and the feeding is controlled by flow control as a response to variation of the value of the parameter, wherein a feed flow to a fluid motor means providing the feed is reduced as a function of a change of the parameter value corresponding to an increase of the rotation moment over a first level. For parameter values corresponding to the rotation moment being below the first level, feeding is controlled by pressure control as a response to the variation of the value of the parameter, wherein a feed pressure for said fluid motor means is reduced as a function of a change of the parameter value corresponding to an increase of the rotation moment. The invention also concerns a rock drilling machine and a drilling rig.

Description

Method and device for the control of a rock drilling machine and a rock drilling machine

FIELD OF THE INVENTION

The invention concerns a method and a device for controlling the feeding of a rock drilling machine according to the preambles of the respective independent claims.

BACKGROUND OF THE INVENTION

During percussive rock drilling, a shock-wave is generated which propagates through the shank adapter and the drill string down to the drill bit. When the shock-wave meets the drill bit, its hard metal studs are pressed into the rock, which generates such a high force that the rock is crushed. In order for the hard metal pins to come into contact with uncrushed rock after a strike, the drill steel is rotated by means of a rotator including a rotation motor (often hydraulic driven) and a transmission.

The drilling machine itself is mounted on a slide, which in turn is movable to and fro on a feed beam. The drilling machine and the slide are driven against the rock, along the feed beam by a feed motor in the form of e.g. a hydraulic cylinder or a chain feeder.

In connection with the drilling there is always risk for a drill to get stuck. This results in difficulties in loosening the drill string, causing reduced production because of loss of production time or loss of the drill string. Having to leave a drill string in a drill hole is, besides the costs of the string and drill bit, also problematic in connection with loading crushed rock and there is also a risk that a lost and loaded drill bit can damage the crusher.

According to the background art, the rotation pressure to the rotation motor is increased when the rock drilling machine is tending to get stuck, since a higher moment is required to rotate the drill bit.

When drilling is started the rotation pressure is increased and in the normal case the pressure level lies between an "idle rotation pressure" and a "desired value for rotation pressure". If the drilling machine tends to get stuck during drilling, the rotation pressure will increase. When it passes the level "desired value for rotation pressure" the feed pressure is reduced in proportion to the rotation pressure to the level or "minimum feed pressure for drilling". This pressure level is as a rule exactly as great as to overcome the friction and moving the drilling machine. This is done in order to reduce the pressure between the rock and the drill bit and to reduce the risk for the drilling machine to get stuck.

Should the rotation pressure in spite of this continue to rise to a level corresponding to "limit drill stuck", a protection-against-drilling-stuck function will be initiated, meaning that the drill slide is fed backwards until the rotation pressure goes below a level corresponding to "limit after drill stuck". During the backward movement, the pressure in the percussive device is reduced to "pressure when initiating drilling". The drill slide is reversed a set "time for reverse feed at drill stuck" (t_f) . If drill stuck does not cease within the set time (t_f) , all drill functions are terminated.

WO 1997/49895 can be mentioned as being a representative of the back ground art.

A problem with older technology is that the drilling can be experience as being jerky. When the rotation pressure rises above the "limit drill stuck" and the protection-against- drilling-stuck function takes over, the drilling machine will be abruptly pulled backwards, which is often experienced as negative and can be harmful for the drilling machine.

WO 2006/108918 concerns a method for controlling a rock drilling process, including control of the feed of a rock drilling machine by means of a pressure difference over a rotation motor such that when the rotation resistance increases such that said pressure difference exceeds a threshold value, the feeding is switched over to a reverse movement. Distinguishing for this method is that at increasing pressure below the threshold value, a feed control valve, being controlled by a separate feed regulating valve, is arranged to correspondingly reduce the feed motor flow. The drawback with this arrangement is indefinite control by the system, in particular during the start of a control process.

AIM AND MOST IMPORTANT FEATURE FOR THE INVENTION

The aim of the present invention is to provide a method and a device, wherein the drawbacks of the background art are set aside or at least reduced. This aim is obtained in a method and a device as mentioned above through the characterizing features of the respective independent claims .

The basic idea with the invention is to provide a combination of pressure and flow control of the feeding to the feed motor, in order to obtain a more gentle and more flexible control when the drilling machine is on the way to get drilled stuck, i.e. the rotation pressure increases above the first level, which can be an empirically determined value for the parameter when the rotation moment (torque) and thereby the rotator resistant increases above values that can be considered to correspond to normal rock drilling. By the pressure control at the starting of the control process is achieved that a direct effect of the system is obtained with reduced play and reduced delay as a great advantage. The inventive combination of these different principles results in the properties that are unexpected for the person skilled in the art, in that the advantages of the respective control principle can be used and the drawbacks thereof can be avoided.

More in detail, the advantages with this control principle are that with parameter values below the first level, the bearing force of the drill bit against the rock can be regulated, which is achieved through the pressure control. By, when exceeding the first level, thereafter switch over to flow control, it is made possible to control the speed of the drilling machine but with still the same maximal bearing force during the whole process. It is preferred that the feed pressure and the feed flow respectively are reduced respectively increased in proportion to a change of the parameter value corresponding to rotation moment in the respective region, which can be realised with reliable and simple components. It is also preferred that the feed flow is reduced for assuming negative values, corresponding to reverse feed, for parameter values corresponding to a rotation moment above a second level. Because of the switched direction, the drilling machine will thus move backwards with increased speed at further increased rotation resistance. This will result in that the requirement for a drill stuck function will be reduced.

According to an embodiment of the invention, the drill stuck function is included with preset drill machine parameters that are initiated at parameter values corresponding to rotation moment above a third level. Compared to the known background art, it is achieved with the invention that advantage that this function will be initiated at considerable fewer occasions during drilling, which gives an increased productivity and altogether enhanced operational economy. Further, in case the drill stuck function has to be initiated after all, this transition will be considerably gentler, since the drilling machine has already started its backward movement when this function is initiated. This will be experienced by the operator as less straining and also result in reduced loads on the drilling machine and the drill steel. Another advantage is that "limit drill stuck" can be raised, since the drilling machine starts to move backwards already before the function is initiated and this way has been handling the less serious drill stuck situations.

It is preferred that said parameter relating to the rotation moment is any one from the group: rotation pressure, detected moment in a rotator transmission, rotational speed. In particular it is preferred that the parameter is the rotation pressure, since this is easy to measure and monitor and it has a direct and predictable connection with the rotation resistance. In general it is true that during drilling it is not desired to limit the forward feed of the drilling machine. For that reason the corresponding valves are regulated such that they do not give any flow limitation for the feed flow. The feed flow which will prevail will be determined by the feed motor, and this flow is normally significantly lower than the flow being possible through the valve. During transition from pressure control to flow control there is therefore a risk that, if transition is carried out such that the pressure control ends at the same time as the flow control is initiated, the flow controlling valve will experience a dead band, or a play, wherein the controlling will be indefinite.

By inside an interval of the value of said parameter in the area of the first level, flow control and pressure control of the feeding overlap each other, this problem is avoided, and it is achieved that possible play and dead band in the system can be further reduced and even be entirely eliminated. In practice the overlap can be achieved by the valve starting to be controlled in the direction of closing, such that when the transition occurs between the control principles, the valve setting is more adapted to actual flow and has thus not affected the system during the overlap. The length of the overlap can be determined through an empirically determined value or be based on a measured value for actual flow, drilling rate or any other suitable parameter. Adjustment of the value can be made manually or automatically.

It is preferred that during normal drilling, between an idle rotation pressure and a desired value rotation pressure, no feed control exists and feed pressure and feed flow are held constant. Hereby the system suitable will go over to pressure control when exceeding desired value rotation pressure .

Corresponding advantages are obtained by the corresponding device claims.

BRIEF DESCRIPTION OF DRAWINGS

The invention will now be described in more detail by way of embodiments and with reference to the drawings, wherein: Fig. 1 diagrammatically shows a drilling rig equipped with a device according to the invention with indicated control system,

Fig. 2 shows a graph over feed pressure as a function of the rotation pressure, Fig. 3 shows a graph showing the feed flow as a function of the rotation pressure,

Fig. 4 diagrammatically shows a method sequence in the form of a flow diagram, and Fig. 5 diagrammatically shows a hydraulic circuit for explanation of the distinction between flow control and pressure control.

DETAILED DESCRIPTION OF EMBODIMENTS

In Fig. 1, reference numeral 1 indicates a drilling rig for rock drilling which carries a feed beam on a drill arm 3. On the feed beam 3 is as conventionally a drilling machine 2 movable to and fro, which acts against a drill string 4 which has a drill bit 5 attached to its distal end.

The rock drilling machine 2 includes in a per se known manner a rotation device (not shown) for the rotation of the drill string 4 during drilling. The rotation motor is thereby hydraulically driven with a rotation flow emanating from the pump 7 over the conduit 8. The pressure in the conduit 8 is the rotation pressure, which is sensed by a pressure sensor 9. The rock drilling machine 2 is driven by of a feed force F in its reciprocating movement by means of a feed motor (not shown) which is hydraulically driven by a feed flow supplied by a pump 10 over a feed conduit 11. The pressure in the feed conduit 11 is the feed pressure, which is sensed by the pressure sensor 12. 6 indicate a central processing unit (CPU) , which receives signals from the sensors 9 and 12 and thus monitors the pressure in these conduits. CPU 6 communicates when it comes to control, with the pumps 7 and 10 as well as with the rock drilling machine 2. Further, the CPU 6 has preferably other functions which, however, are not described here since they are not subjects of the present invention. Fig. 2 shows in the form of a graph, the feed pressure P_M as a function of the rotation pressure P_R. Fig. 3 shows in the form of a graph the feed flow as a function of the rotation pressure P_R. During normal drilling, the rotation pressure is between "idle rotation pressure" Pi and "desired value rotation pressure" P_RB. This gives a "feed pressure drilling" and a "flow drilling".

Should the rotation pressure increase over a limit, which is suitably set to be said "desired value rotation pressure" PRB, the feed pressure will be reduced in proportion to the continued increase of the rotation pressure. The feed pressure is suitable reduced to the level "minimum feed pressure drilling", which preferably can be the pressure which is needed to overcome the friction between the feed beam and the slide but also can be higher.

With the rotation pressure continuous to increase above a first level Pl, the control principle is shifted from pressure control to flow control. At the same time the flow to the drilling machine is reduced in proportion to the increase of the rotation pressure, at the same time as the feed pressure is now held constant on the level "minimum feed pressure drilling".

Should the rotation pressure P_R continue to increase to a second level P2, which corresponds to such a reduction of the flow to the drilling machine feed that this has been regulated down to zero, there occurs a shift of the pressure such that the drilling machine starts to be fed backwards at further increase of P_R. The feed pressure level is then defined as "feed pressure backwards". If an arm with a chain feeder is used, this pressure level will lie approximately as "minimum feed pressure drilling", but if a cylinder feeder is used, it will lie considerably higher, since the drive area rearwards is not as great as the one forwards on the piston. Should now the rotation pressure P_R continue to increase, the flow will increase, but opposite to the previous direction, and the drilling machine will move backwards with increased speed. Should the rotation pressure continue increase still more, a third rotation pressure level P3 is reached: "limit drill stuck". This means that the drill stuck protection function will be launched; whereby certain predetermined drilling machine parameters will be set. The drill slide is then fed backwards until the rotation pressure goes below "limit after drill stuck", which is a value set lower for rotation pressure than "limit drill stuck". During the backward motion, the percussion device pressure will be reduced to collaring pressure. The drill stuck protection function will be active "time feed return" tf. If drill stuck has not ceased yet, all drill functions are terminated.

The method according to the invention as well as the drill stuck protection function can be entirely software based and all parameters can be set and corrected by the operator or by a service technician.

In Fig. 4 is shown a method sequence in the form a fluid diagram, wherein position 19 indicates the start of the sequence, position 20 indicates normal drilling with the rotation pressure between "idle rotation pressure" and "desired value rotation pressure". This gives a "feed pressure drilling" and a "feed flow drilling", whereby the function is entirely passive and no regulation occurs. During monitoring the rotation pressure it is now examined whether the rotation pressure P_R has increased above P_RB, i.e. desired value rotation pressure. If that is not the case, the system will revert to position 20. If, however, P_R is above P_RB, it switches to position 21. In position 21, the rotation pressure has thus increased above the limit "desired value rotation pressure". The system switches to feed pressure control and with continued monitoring of the rotation pressure P_R. If P_R exceeds Pl, corresponding to an increase of the rotation moment over a first level, it is, according to the invention, switched to position 22.

Position 22 implies transition to flow control of the drilling machine feed, such that increased rotation pressure results in proportional reduction of the flow to the drilling machine feed, at the same time as the feed pressure is held constant on the level "minimum feed pressure drilling", according to the above. At the continued monitoring of the rotation pressure above the first level, it is now examined whether the rotation pressure P_R exceeds P2, i.e. a second level. If that is not the case, the system switches to directly after the position 21. If, however, P_R exceeds P2 it is switched to position 23. In position 23 a shift is made of the feed pressure to the drilling machine feed such that the drilling machine is brought to move backwards. The flow to the drilling machine feed will still be changed in proportion to the change of the rotation pressure. At the continued monitoring of the rotation pressure, it is now examined whether the rotation pressure P_R exceeds P3, which is a third level for the rotation pressure implying a limit for drill stuck. If it is found that that is not the case, it is reverted in the sequence to directly after position 22. If, however, P_R exceeds P3 it is switched to position 24.

Position 24 implies the initiating of a drill stuck protection function meaning initiating of certain preset drilling machine data over a predetermined time: "time feed return" t_f. When the time t_f has passed, it is examined if the rotation pressure P_R still exceeds P3. If that is not the case, it is switched in the sequence to directly after position 23. If, however, P_R still exceeds P3 it is switched to position 25. In position 25 is initiated closing down of the drilling machine when the drill string, with the drill bit, is considered to be drilled stuck to the extend that it can not be loosened through this function of the drilling machine. The drilling then switches over to manual control through the operator.

Position 26 indicates the end of the sequence. The invention can be modified within the scope of the claims and there can be deviations from the above described embodiment. The regulation can thus be undertaken otherwise than through proportional flow control, even if said proportional flow control is preferred. All limits and levels are adjustable after the prevailing situation and existing equipment, for example the flow control can start already with the rotation pressure exceeding "desired value rotation pressure" .

Position 21 can be completed such that within an interval for the value of said parameter below the first level, the feed pressure is reduced at an increase of the value of the parameter. The feed pressure can be reduced in proportion to the increase of the value of the parameter or be reduced momentarily at the increase of the value of the parameter. In Fig. 2 is shown that the feed pressure is reduced proportionally when exceeding "desired value rotation pressure", but is also instead possible to more or less momentarily reduce the feed pressure to "minimum feed pressure drilling", that is the same feed pressure that prevails during the main part of the flow control, as is described in connection with Fig. 3. In that case the graph in Fig. 2 should drop momentarily to "minimum feed pressure drilling" or follow a different path then is shown in the Figure.

Said parameter being monitored respectively measured can besides rotation pressure also be sensed moment in a rotator transmission, for example through per se known torque sensors, or rotational speed, sensed by a rotational speed sensor.

The means in the device according to the invention that provide the inventive functions are per se conventional regulating and control devices:

The means for monitoring a parameter related to the rotation moment and to control a feed force as a response to the variation of value of the parameter are suitably on the one hand the CPU in combination with sensors, on the other hand the CPU in combination with fluid control devices.

The means for reducing respectively increasing the feed force by altering a feed flow to a fluid motor means providing the feed in relation to a change of the parameter value, is suitably the CPU in combination with fluid regulating devices. The means for initiating a drill stuck function with preset drill machine parameters are suitably realised through the CPU in combination with mechanical setting means.

An alternative to the above described drill stuck function is that the drilling machine simply is quickly fed backwards without further auxiliary functions. The invention in its most general scope does not presuppose any drill stuck function at all.

It is advantageous if within an interval of the value of said parameter in the region of the first level, the fluid control and the pressure control of the feed overlap each other. In particular, a valve regulating the feed flow can start to be regulated in the direction of closing before the pressure control has ended as a response to any from the group: an empiric flow value, measured feed flow, measured or estimated drilling rate. Through the overlap it is achieved that possible play and dead band in the system can be reduced further and even be entirely eliminated. In practice the overlap can be achieved by the valve being regulated in the closing direction, such that when switching occurs between the control principles, the valve setting is more adapted to actual flow.

The adjustment of the value can be made manually or automatically. With reference to Fig. 3, the irregular graph indicates the actual flow during drilling in practice. 39 indicates the progress of the flow during flow control. By adapting the overlap principle according to the above, instead the flow control starts already before the pressure control is ended, and then following graph 40. A dead band, represented by the section 41, where the control otherwise would be insecure, can through this variant of the invention be avoided, and the control be made coherent and more exact over the entire control field and in particular at the transition between the control principles. Related to "the first level" the principle of overlap can be explained such that the pressure control will continue somewhat above this when the flow control has started, or vice versa, that the fluid control has started somewhat before "the first level". It is now referred to Fig. 5 for the explanation of the distinction between flow control and pressure control. For the flow control can be used a pressure compensated valve, which means that a pressure difference over the inside and the outside of a main valve 27 of a feed motor 29 is regulated by a valve 28. The aim of the regulation is to keep the pressure difference as constant as possible. Since:

Flow = opening area x Vpressure difference

the flow will only be dependent on the setting of the valve, which gives the opening area.

For pressure control is used a pressure limiter 30, for example one that is electronically controlled. When the For pressure control is used a pressure limiter 30, for example one that is electronically controlled. When the pressure exceeds the certain level, the valve opens to tank and the pressure is reduced in the conduit, which results in that the valve 28 closes.

An alternative solution for flow control would be to regulate the flow from the pump 31 either with a rotation speed controlled hydraulic pump or with a hydraulic pump with controllable displacement. Fig. 5 should be seen free-standing from Fig. 1, but the pump 31 in Fig. 5 corresponds to the pump 10 in Fig. 1.

Claims

C L A I M S

1. Method for controlling the feeding on a feed beam (3) of a to and fro movable rock drilling machine (2), which includes a percussive device and a rotation motor providing a rotation moment, wherein a parameter related to the rotation moment is monitored and the feeding is controlled by flow control as a response to variation of the value of the parameter, wherein a feed flow to a fluid motor means providing the feed is reduced as a function of a change of the parameter value corresponding to an increase of the rotation moment over a first level, c h a r a c t e r i z e d in that for parameter values corresponding to the rotation moment being below the first level, feeding is controlled by pressure control as a response to the variation of the value of the parameter, wherein a feed pressure for said fluid motor means is reduced as a function of a change of the parameter value corresponding to an increase of the rotation moment.

2. Method according to claim 1, c h a r a c t e r i z e d in that the feed pressure is reduced respectively increased in proportion to a change of the parameter value corresponding to rotation moment below the first level.

3. Method according to any one of the previous claims, c h a r a c t e r i z e d in that the feed flow is reduced respectively increased in proportion to a change of the parameter value corresponding to rotation moment above the first level.

4. Method according to any one of the previous claims, c h a r a c t e r i z e d in that the feed flow is reduced for assuming negative values, corresponding to feeding backwards, for parameter values corresponding to a rotation moment above a second level.

5. Method according to any one of the previous claims, c h a r a c t e r i z e d in that a drill stuck protection function with preset drilling machine parameters is initiated at parameter values corresponding to rotation moment above a third level.

6. Method according to any one of the previous claims, c h a r c t e r i z e d in that said parameter related to the rotation moment is any one from the group: rotation pressure, sense moment in a rotator transmission, rotational speed.

7. Method according to any one of the previous claims, c h a r a c t e r i z e d in that within an interval of the value of said parameter in the area of the first level, flow control and pressure control of the feed overlap each other.

8. Method according to claim 7, c h a r a c t e r i z e d in that a feed flow regulating valve is started to be regulated in the direction of closing before the pressure control has stopped as a response to any one of the group; an empiric value of the flow; measured feed flow, measured or estimated drilling rate.

9. Method according to claim 1, c h a r a c t e r i z e d in that the feed pressure is reduced momentarily during increase of the value of the parameter.

10 Method according to any one of the previous claims, wherein the parameter is rotation pressure, c h a r a c t e r i z e d in that for values of the rotation pressure corresponding to normal drilling, between an idle rotation pressure and a desired value rotation pressure, no feed control exist and feed pressure and feed flow are held constant.

11. Method according to claim 10, c h a r a c t e r i z e d in that the system switches to pressure control when exceeding desired value rotation pressure.

12. Device for controlling the feeding on a feed beam (3) of the to and fro movable rock drilling machine (2), which includes a percussive device and a rotation motor providing a rotation moment, including monitoring means for monitoring a parameter related to the rotation moment and flow control means for controlling the feeding as a response to variation of the value of the parameter, by reducing a feed flow to a fluid motor device providing the feeding as a function of a change of the parameter value corresponding to an increase of the rotation moment above a first level, c h a r a c t e r i z e d by pressure control means for controlling the feeding as a response to the variation of the value for the parameter for parameter values corresponding to the rotation moment being below the first level, wherein a feed pressure to said fluid motor means is reduced as a function of a change of the parameter value corresponding to an increase of the rotation moment.

13. Device according to claim 12, c h a r a c t e r i z e d in that said pressure control means are arranged to reduced respectively increase the feed pressure in proportion to a change of the parameter value corresponding to rotation moment below the first level.

14. Device according to claim 12 or 13, c h a r a c t e r i z e d in that said fluid control means is arranged to reduced respectively increase the feed flow in proportion to a change of the parameter value corresponding to rotation moment above the first level.

15. Device according to any one of the claims 12 - 14, c h a r a c t e r i z e d in that said flow control means is arranged to reduce the feed flow for assuming negative value, corresponding to feeding backwards, for parameter values corresponding to a rotation moment above a second level.

16. Device according to any one of the claims 12 - 15, c h a r a c t e r i z e d by a drill stuck protection function with preset drilling machine parameters, which is arranged to be launched at parameter values corresponding to rotation moment above a third level.

17. Device according to any one of the claims 12 - 16, wherein said parameter relating to the rotation moment is anyone from the group: rotation pressure, sensed moment in a rotator transmission, rotation speed.

18. Device according to any one of the claims 12 - 17, c h a r a c t e r i z e d in that said flow control means and said pressure control means are arranged, inside an interval of the value of said parameter in the area of the first level, to provide overlap of flow control and pressure control.

19. Device according to claim 18, c h a r a c t e r i z e d by means for starting to control a valve regulating the feed flow in the direction of closing before the pressure control has ended as the response to any one from the group: an empiric value for the flow, measured feed flow, measured or estimated drilling rate.

20. Device according to any one of the claims 12 - 19, wherein the parameter is rotation pressure, c h a r a c t e r i z e d by means for holding feed pressure and feed flow constant, unregulated, for values of the rotation pressure corresponding to normal drilling, between an idle rotation pressure and a desired value rotation pressure.

21. Device according to claim 20, c h a r a c t e r i z e d by means for switching the system to pressure control when exceeding desired value rotation pressure.

22. Rock drilling machine including a device according to any one of the claims 12 - 21.

23. Rock drilling rig including a rock drilling machine according to claim 22.