Method and device for controlling at least one drilling parameter for rock drilling

1. Method for controlling at least one drill parameter when drilling rock with a drilling machine, in which method, during drilling, an impulse-generating device by means of an impact means induce shock waves in a tool working against the rock, wherein a pressure level for a shock-wave-generating pressure is controlled during the drilling, said drilling machine including a damping chamber that can be pressurized, and the control of the contact of the drilling machine against the rock is affected at least partially by the pressure prevailing in said damping chamber, characterized by the step in which, when the pressure in said damping chamber exceeds a first level and is below a second level, the percussion pressure is controlled as a function of a pressure in said damping chamber.

2. Method according to claim 1 , characterized in that said control involves the percussion pressure being controlled between a first level, which substantially corresponds to a start-up drilling level, and a second level, which substantially corresponds to a normal drilling level.

3. Method according to claim 1 , characterized in that it further includes the step of, during said control, increasing the percussion pressure when the pressure in said damping chamber increases, and decreasing the percussion pressure when the pressure in said damping chamber decreases.

4. Method according to claim 1 , characterized in that a percussion pressure increase is controlled in such a way that the percussion pressure increase per unit of time is kept below a threshold value.

5. Device for controlling at least one drill parameter when drilling in rock with a drilling machine, where, during drilling, an impulse-generating device, by means of an impact means induce shock waves in a tool working against the rock, wherein a pressure level for a shock-wave-generating pressure is controlled during the drilling, said drilling machine including a damping chamber that can be pressurized, and the control of the contact of the drilling machine against the rock being affected at least partially by the pressure prevailing in said damping chamber, characterized in that the device includes means for, when the pressure in said damping chamber exceeds a first level and is below a second level, controlling a percussion pressure as a function of the pressure in said damping chamber.

6. Device according to claim 5 , characterized in that, during said control, the said means are arranged to control the percussion pressure between a first level, which substantially corresponds to a start-up

7. Device according to claim 6 , characterized in that said means is arranged to control the percussion pressure in such a way that the control reflects changes in the pressure in said damping chamber.

8. Device according to claim 6 , characterized in that it further includes means for, when the pressure in said damping chamber exceeds said second level, controlling the percussion pressure in such a way that it is maintained substantially at a pressure corresponding to the percussion pressure for said second level.

9. Device according to claim 6 , characterized in that said means are arranged to determine said pressure in said damping chamber by determining a parameter value representing a mean value of a damping pressure in the damping chamber.

10. Device according to claim 5 , characterized in that said means is arranged to control the percussion pressure in such a way that the control reflects changes in the pressure in said damping chamber.

11. Device according to claim 10 , characterized in that it further includes means for, when the pressure in said damping chamber exceeds said second level, controlling the percussion pressure in such a way that it is maintained substantially at a pressure corresponding to the percussion pressure for said second level.

12. Device according to claim 7 , characterized in that said means are arranged to determine said pressure in said damping chamber by determining a parameter value representing a mean value of the damping pressure in the damping chamber.

13. Device according to claim 5 , characterized in that it further includes means for, during said control, increasing the percussion pressure with an increase of the pressure in said damping chamber, and decreasing the percussion pressure with a decrease of the pressure in said damping chamber.

14. Device according to claim 5 , characterized in that it further includes means for, when the pressure in said damping chamber exceeds said second level, controlling the percussion pressure in such a way that it is maintained substantially at the pressure corresponding to the percussion pressure for said second level.

15. Device according to claim 5 , characterized in that said means are arranged to control a percussion pressure increase in such a way that the percussion pressure increase per unit of time is maintained below a threshold value.

16. Device according to claim 5 , characterized in that said means are arranged to determine said pressure in said damping chamber by determining a parameter value representing a mean value of a damping pressure in the damping chamber.

17. Device according to claim 16 , in which said means are arranged to determine said mean value based on a number of impulse cycles.

18. Device according to claim 5 , characterized in that it further includes means for, when the pressure in said damping chamber exceeds a third level higher than said second level, controlling the percussion pressure as a function of the pressure in said damping chamber, with said percussion pressure exceeding a second percussion pressure level.

19. Device according to claim 5 , characterized in that it further includes means for controlling the percussion pressure in such a way that the time for an increase of said percussion pressure from a first level to a second level exceeds a threshold value.

20. Rock-drilling rig, characterized in that it includes a device According to claim 5 .