WO1997047858A1

WO1997047858A1 - Method and arrangement for controlling a rock drilling unit driven by a diesel-hydraulic power source

Info

Publication number: WO1997047858A1
Application number: PCT/FI1997/000360
Authority: WO
Inventors: Tapani PÖYSTI; Pentti Enlund; Kalle Tuohimaa
Original assignee: Tamrock Oy
Priority date: 1996-06-10
Filing date: 1997-06-09
Publication date: 1997-12-18
Also published as: AU3176897A; FI962402A; FI962402A0

Abstract

A method and an arrangement for controlling the operation of a rock drilling unit driven by a diesel-hydraulic power source. In the invention, the hydraulic fluid flow supplied by a diesel engine (3) driven pressure controlled volume flow pump (5) to the hydraulic motor (8) of a compressor (9) is controlled in proportion to the speed of rotation of the diesel engine (3), so that when the speed of rotation drops owing to the load caused by the rock drill (1), the volume flow of the hydraulic fluid supplied by the volume flow pump (5) decreases in order to decrease the load.

Description

METHOD AND ARRANGEMENT FOR CONTROLLING A ROCK DRILLING UNIT DRIVEN BY A DIESEL-HYDRAULIC POWER SOURCE

The invention relates to a method for controlling a rock drilling unit driven by a diesel-hydraulic power source, wherein air is supplied to the rock drill by a compressor driven by a hydraulic motor operated by a separate pres¬ sure controlled volume flow pump driven by a diesel engine.

The invention also relates to an arrangement for controlling a rock drilling unit driven by a diesel-hydraulic power source, the arrangement com¬ prising a diesel engine, a compressor for supplying air to the rock drill, a hy- drauiic motor for rotating the compressor, and at least one hydraulic pump for supplying hydraulic fluid to the rock drill, and a pressure controlled volume flow pump for supplying hydraulic fluid to the hydraulic motor of the compressor.

It is typical in a diesel engine driven hydraulic power unit, where the output of diesel engine driven hydraulic pumps is used both for operating vari- ous devices, such as a rock drill, and for providing air blowing, that either the power, and thus the weight and measurements of the diesel engine have to be dimensioned in accordance with the maximum load on the whole equipment, or alternatively take the risk of the diesel engine becoming overloaded during operation of the equipment, leading to shorter service life and increased maintenance costs.

The operation of hydraulic motor driven compressors in such de¬ vices has typically been realized by what is known as open loop hydraulics without any automatic control. In these cases performance is usually low and requires, besides separate cooling, also quite a voluminous oil tank. Since the operation and power consumption of the compressor cannot be controlled, the diesel engine may become overloaded as the power consumption of other de¬ vices increases. As a result of overloading, the speed of rotation of the diesel engine usually drops leading to a decrease in the capacity and performance of the entire equipment. Fl 87830 shows a solution wherein the air supply of a rock drill is controlled inversely proportionally to the impact pressure of the percussion unit by using a volume flow pump as the hydraulic fluid pump of the hydraulic mo¬ tor. Although in this solution other power demand loading the diesel engine is taken into account to some degree, it is likely to be insufficient as the load can change for other reasons than owing to the impact pressure.

It is the object of the present invention to provide a method and an arrangement which allow the diesel engine to be designed according to the real power demand, and by which overloading the diesel engine can be elimi¬ nated without impairing equipment performance. The method of the invention in characterized in that the operation is controlled on the basis of the speed of rotation of the diesel engine so that when the speed of rotation of the diesel engine drops from a set value, the volume flow of the hydraulic fluid supplied to the hydraulic motor of the compressor decreases.

The arrangement of the invention is characterized in that it com¬ prises a separate control pump for supplying control pressure to the pressure controlled volume flow pump, and that it comprises means for controlling said control pressure in proportion to the speed of rotation of the diesel engine so that with the speed of rotation of the diesel engine dropping, said control pres¬ sure is reduced in order to decrease the volume flow of the hydraulic fluid supplied by the volume flow pump. It is an essential idea of the invention that the power, i.e. the hy¬ draulic fluid flow, supplied to the air compressor, is controlled on the basis of the load on the diesel engine. It is a further essential idea of the invention that the load is monitored by observing the speed of rotation of the diesel engine and once the speed of rotation starts to drop due to overload, the liquid output of the hydraulic pump of the compressor is reduced in order to reduce the load so that the capacity of the diesel engine is not exceeded.

An advantage of the invention is that at low drilling capacities, when the rest of the equipment does not load the diesel engine, the entire capacity of the compressor, including a large amount of air, is available. Further, the total fuel consumption of the equipment is reduced as it becomes possible to use a smaller diesel engine than before. Further, as the diesel engine is not overloaded, the stress and wear on it are reduced leading to a longer service life. The elimination of overload leads to longer service life for the components of the equipment, and as less heat is produced, the need for cooling is also smaller.

The invention will be described in more detail in the following draw¬ ings, wherein

Figure 1 schematically shows an embodiment of the arrangement of the invention, Figure 2 schematically shows another embodiment of the arrange¬ ment of the invention, and Figure 3 schematically shows a third embodiment of the arrange¬ ment of the invention.

The basic components of the equipment are the same in Figs. 1 to 3, and the same reference numerals are used for the same components in the Figs, without any separate specification.

Figure 1 schematically shows an embodiment of the arrangement of the invention. The Figure shows a rock drill 1 for drilling holes into a rock 2. The rock drill is driven by a diesel engine 3, whose shaft 4 is used for rotating hydraulic pumps 5 to 7. A volume adjustable hydraulic pump 5 is used to sup- ply hydraulic fluid to a hydraulic motor 8 which is inserted in a closed circuit with the pump and rotates a compressor 9. The air pumped by the compressor 9 is led to a pressure tank 10 and via a valve 11 to the rock drill 1. The air is led from the rock drill 1 through a thereto coupled drill rod or the like 12 to a drill hole formed into the rock 2 in order to remove the material generated by the drilling.

The hydraulic pump 6 pumps hydraulic fluid from a tank 13 to the rock drill 1 in order to operate it in a manner known per se. Similarly, the hy¬ draulic fluid is led from the rock drill 1 back to the tank 13 in a manner known per se and not presented. A third hydraulic pump, i.e. a control pump 7, oper- ates in this embodiment as a feeder, and adjusts and controls the pressure of the volume adjustable pump 5 operating the hydraulic motor 8 of the compres¬ sor 9. From the control pump 7 the hydraulic fluid is led via a channel 14 to a manual guide 15 which can be used to manually adjust a valve 17 affecting the control of the pump 5 by means of a channel 16. The hydraulic fluid can flow further from the control pump 7 via a non-return valve 18 to a closed cir¬ cuit formed by the pump 5 and the hydraulic motor 8, the control pump 7 oper¬ ating as the filling pump of said circuit. Simultaneously the pressure is trans¬ mitted through a pressure regulating valve 19 via a channel 20 to the valve. The controls of the pump 5 include a controller chamber 21 comprising a pis- ton 22 subject to spring pressure 23 on one side. The pressure of the hydrau¬ lic fluid supplied from the channel 20 further affects the piston 22 of the con¬ troller chamber 21 via a channel 24 on the opposite side relative to the spring. During normal operation of the device and with the motor rotating at its nominal speed of rotation, the pressure provided by the control pump 7 in the controller chamber 21 of the pump 5 is such that the compressor 9 rotates at such a high speed as is set by the normal adjustment of the pump 5. As a result of drilling, the load on the diesel engine increases causing its speed of rotation to drop, and consequently the pressure of the hydraulic fluid supplied by the control pump 7 and the pressure affecting the controller chamber 21 of the pump 5 also decrease. At this point the spring 23 displaces the piston 22 so that it causes a decrease in the supply, i.e. the volume flow of the hydraulic fluid of the pump 5 operating the compressor 9, thus decreasing the load on the diesel engine 3 and allowing its speed of rotation to return towards its nominal value. In practice the speed of rotation of the diesel engine remains slightly below the nominal value because if it would rise to its original value with the loads remaining in the same way, its speed of rotation would again drop because of the load as the pressure supplied by the control pump 7 would rise. As the change in the pressure supplied by the control pump 7 in the adjustment of the pump 5 is quite high, i.e. a small pressure drop signifi¬ cantly reduces the volume flow, the adjustment range of the diesel engine 3 is quite narrow, and it operates almost at its optimal speed of rotation in spite of the great changes in the volume of air supplied by the compressor 9. In the situation shown by the Figure, the output of the pump 5 is at its minimum, and thus the compressor does not supply air. When the controller 15 is used to connect the channel 14 emanating from the control pump 7 via the channel 16 to the valve 17, the valve 17 guides the pressure supplied via the channel 20 to the controller, the hydraulic fluid pressing the piston 22 against the spring 23, increasing the output of the pump 5. Since the valve 17 is a proportional valve, it guides the pressure to the controller chamber 21 in relation to the pressure of the control pump 7, whereby a drop in the pressure of the control pump 7 with a drop in the speed of rotation displaces the valve 17 towards the position shown by the Figure, and the pressure supplied from the control pump

7 via the pressure limit 19 is allowed to be discharged directly to the hydraulic fluid tank 13 as the fluid output of the pump 5 drops to its set minimum value.

The manual control 15 is useful and necessary when drilling takes place under circumstances requiring low capacity and wherein the compressor supplies an unnecessarily large amount of air. In these cases the pump 5 can be controlled by the manual controller so that it supplies the hydraulic motor 8 of the compressor 9 with less hydraulic fluid. In this way the amount of air in¬ put by the compressor can be reduced below the maximum amount allowed by available capacity. This is a way of saving fuel consumption as the entire capacity of the diesel engine does not have to be used. Simultaneously the stress on the diesel engine is reduced, as are its maintenance and operating costs. In addition, the diesel engine is left with a capacity reserve that can be used for drilling at unexpected drilling points requiring more capacity e.g. be¬ cause of change of rock type or rock structure. Figure 2 shows in principle a solution conforming with that of Figure

1 , but with the hydraulic control being realized by utilizing a detector rotating with a flywheel 3a on the shaft of the diesel engine 3. An electric probe 26, controlled by an electric control unit 15' measures the speed of rotation of the diesel engine 3. The control unit in turn electrically controls a valve 17' and manual control can be realized by e.g. an adjustable resistance 15a'. In this case no separate pressure limit 19 is used, instead pump output goes directly through a throttle 27 to the valve 17'.

Figure 3 shows a coupling corresponding to that of Figure 1 , except that the hydraulic control is realized by an open circuit. In Figure 3, the control pump T used in connection with the open circuit may be either a completely separate control pump, or another pump, e.g. one intended for operating a device, can be used for supplying control pressure. In this case the hydraulic fluid for the device can be taken at some point of the hydraulic fluid circuit of the pump 7', shown as an example in the Figure by a dashed line 33. In the foregoing description and drawings the invention has been described only by way of example, and it is by no means to be so restricted. The coupling corresponding to Figure 3 can be realized by using electric con¬ trol in the manner shown in Figure 2. It is essential that the speed of rotation of the diesel engine causes a change in the hydraulic fluid flow supplied to the hydraulic motor of the compressor, so that with the speed of rotation of the diesel engine dropping, the input of hydraulic fluid to the hydraulic motor of the compressor decreases causing the speed of rotation of the diesel engine to remain approximately at its nominal value. Similarly, with the load decreasing and the speed of rotation of the diesel engine reaching its nominal value or exceeding it, the hydraulic fluid flow supplied to the hydraulic motor of the compressor increases until it reaches its set maximum value. Further, the ro¬ tation of the compressor, i.e. the hydraulic fluid flow to the compressor, can be manually controlled, and can be set at a low value irrespective of the control. In this case the control can be carried out either steplessly or by switching off the control of the valves 17 or 17', whereby the output of the pump 5 drops to the minimum.

Claims

1. A method for controlling a rock drilling unit driven by a diesel- hydraulic power source, wherein air is supplied to the rock drill by a compres¬ sor driven by a hydraulic motor operated by a separate pressure controlled volume flow pump driven by a diesel engine, characterized in that the operation is controlled on the basis of the speed of rotation of the diesel en¬ gine so that when the speed of rotation of the diesel engine drops from a set value, the volume flow of the hydraulic fluid supplied to the hydraulic motor of the compressor decreases.

2. A method as claimed in claim 1, characterized in that the control is effected by using a separate control pump (7, 7') rotated by the die¬ sel engine (3) and producing a hydraulic liquid pressure for controlling the vol¬ ume flow pump (5), and that the control pressure of the volume flow pump is controlled by a separate proportional control valve whose operation is con- trolled on the basis of the speed of rotation of the diesel engine (3).

3. A method as claimed in claim 2, characterized in that the control pressure of the volume flow pump (5) is controlled by a proportional control valve (17) controlled by means of the hydraulic fluid pressure, and that the pressure of the hydraulic fluid supplied by the control pump (7, 7') is used to control the control valve (17).

4. A method as claimed in claim 1, characterized in that the speed of rotation of the diesel engine (3) is measured electrically and that the control pressure of the volume flow pump (5) is controlled by means of a thus obtained electric signal by using an electrically controlled proportional control valve (17').

5. A method as claimed in any one of claims 1 to 3, charac¬ terized in that a closed circuit formed by the pump (5) and the hydraulic motor (8) of the compressor (9) is used for controlling the compressor, and that a completely separate control pump (7) for supplying control pressure is used for the control.

6. An arrangement for controlling a rock drilling unit driven by a die¬ sel-hydraulic power source, the arrangement comprising a diesel engine, a compressor for supplying air to the rock drill, a hydraulic motor for rotating the compressor, and at least one hydraulic pump for supplying hydraulic fluid to the rock drill and a pressure controlled volume flow pump for supplying hy- drauiic fluid to the hydraulic motor of the compressor, characterized in that it comprises a separate control pump for supplying control pressure to the pressure controlled volume flow pump, and that it comprises means for con¬ trolling said control pressure in proportion to the speed of rotation ofthe diesel engine so that with the speed of rotation of the diesel engine dropping, said control pressure is reduced in order for the volume flow of the hydraulic fluid supplied by the volume flow pump to decrease.

7. An arrangement as claimed in claim 6, characterized in that the means for supplying control pressure include a pressure controlled proportional control valve (17) and means for leading the pressure of the hy¬ draulic fluid supplied by the control pump (7, 7') to the valve (17), so that with the pressure of the hydraulic fluid supplied by the control pump (7, 7') de¬ creasing as the speed of rotation of the diesel engine (3) drops, the control valve (17) decreases the control pressure supplied to the pump (5) so that the volume flow of the hydraulic fluid fed by it to the hydraulic motor (8) decreases.

8. An arrangement as claimed in claim 6, characterized in that the means for controlling control pressure to the pressure controlled vol¬ ume flow pump (5) include an electrically controlled proportional control valve (17'), and that it comprises means for measuring the speed of rotation of the diesel engine (3) electrically, and an electrically operating control unit (15') controlling the control valve (17') in proportion to the speed of rotation of the diesel engine (3), so that with the speed of rotation dropping, the control valve (17') decreases the control pressure supplied to the pump (5), leading to a corresponding decrease in the volume flow of the hydraulic fluid supplied by the pump (5) to the hydraulic motor (8).

9. An arrangement as claimed in claim 6 or 7, characterized in that the pressure controlled volume flow pump (5) and the hydraulic motor (8) of the compressor are coupled to form a closed circuit, and that the control pump (7) is a separate pump intended solely to supply control pressure.

10. An arrangement as claimed in any one of claims 6 to 9, characterized in that it comprises a manual guide (15; 15', 15a') for reducing the amount of hydraulic fluid supplied by the pump (5) to the hydrau¬ lic motor (8) of the compressor (9) and thus the amount of air supplied by the compressor (9) below the maximum amount of air output permitted by the ca- pacity available.