CN101903134B - Hand-held machine tool - Google Patents

Abstract

The invention relates to a hand-held machine tool (10) having a machine chamber (12), an impacting mechanism unit (14) and a control hole (22), which are arranged in the machine chamber (12); the impacting mechanism unit includes a hammer member unit (16) which is driven by a gas volume (20) via a piston unit (18); and the control hole enables the gas volume (20) to be coupled with the machine chamber (12). The hand-held machine tool (10) has at least a device (24) which is configured for increasing the pressure intensity (pM) in the machine chamber (12).

Description

hand tool machine

technical field

The invention relates to a hand-held power tool according to the preamble of claim 1 .

Background technique

A hand-held power tool of the aforementioned type with a machine compartment is known from DE 19810088 C1. Arranged in the machine compartment is a striking mechanism unit comprising a hammer unit which can be driven by means of the piston unit through the gas volume. This gas volume is coupled to the machine chamber via the control bore in the idle position of the hammer mechanism unit or in the expansion phase of the hammer mechanism unit.

Contents of the invention

The invention relates to a hand-held power tool with a machine chamber, a hammer mechanism unit arranged in the machine chamber, and a control opening, the hammer mechanism unit comprising a hammer unit through which a gas volume can be passed by means of a piston unit Driven, the control orifice couples the gas volume to the machine chamber. In this context, "gas" is to be understood in particular as air. Furthermore, a "control hole" in this context is to be understood in particular as an element which is specially configured and/or arranged especially for controlling the gas volume. Furthermore, “coupling” in this context is to be understood in particular as fluid-technical coupling such that the gas of the gas volume flows through the control opening into the machine chamber and/or the gas volume can be fed with gas from the machine chamber. Furthermore, "machine room" is to be understood in particular as a "gear room", "lubricating oil room", "motor room" etc. and/or in particular a room which is at least viewed outwardly, that is to say The surroundings of the hand-held power tool are isolated and connected to the surroundings of the hand-held power tool, for example, at least substantially only via the pressure compensation device. Through a corresponding configuration, at least a direct gas exchange between the gas volume and the surroundings of the hand-held power tool and the resulting impairment of comfort and environmental stress can be avoided.

The invention proposes that the hand-held power tool has at least one device provided for increasing the pressure in the machine compartment. In this context, "provided" is to be understood in particular as being specially equipped and/or arranged. During operation of the hand power tool, the piston unit performs an oscillating movement in the guide tube of the hand power tool. By means of the compression of the gas volume, ie in the compression phase, the translational energy of the piston unit is transferred via the gas volume to the hammer unit and accelerates the hammer unit in translation to approximately twice the speed of the piston unit. This is followed by the striking process of the hammer unit on the striking pin or the knife. During each compression, a small amount of gas leaks from the compression chamber into the machine chamber of the hand tool machine. In the usual construction of the striking mechanism unit, there are always leakage losses of the gas volume, which arise in particular due to the high compression of the gas volume. For a cost-effective construction of the percussion mechanism unit, leakage losses of the gas volume are unavoidable, since small manufacturing tolerances make the percussion mechanism unit expensive and higher sealing of the components can lead to higher wear and/or seizure of the components live. In this case, therefore, leakage losses of the striking mechanism unit cannot be completely suppressed. In order to compensate leakage losses, control holes are provided which couple the gas volume with the machine chamber, wherein the size and position of the control holes are determined by the effect of the gas compensation. During the backward movement of the piston unit, ie during the expansion phase, a small negative pressure, ie a pressure lower than the pressure in the machine chamber, is generated in the compression chamber, which pulls the hammer unit backwards. For the backward movement of the piston unit, on the one hand, the reflection of the hammer unit on the impact pin or the tool is used, and on the other hand, the negative pressure generated by the piston unit or the suction force of the piston unit is used, so that the hammer unit It is transported again into the initial position or into the subsequent retracted position. The piston unit and the striker unit are coupled axially reciprocatingly via the gas volume and thus form an oscillatable system. This oscillating system is strongly influenced by the friction of the hammer unit. The suction force of the piston unit acting on the hammer unit is determined by the cross-section of the hammer unit multiplied by the pressure difference on both sides of the hammer unit or by the pressure p _M in the machine chamber and the gas volume or in the compression chamber It is composed of the product of the pressure difference between negative pressures. In this oscillating system, negative pressure cannot be effectively reduced. However, the resultant force on the hammer unit can be increased by increasing the machine chamber pressure p _M. The result is that the hammer unit returns earlier in time to the rear folded position, which can be braked longer and more smoothly by the forwardly moving piston unit. The maximum pressure drop is less and the hammer unit is accelerated to a higher impact speed earlier. Subsequent impacts of the hammer unit then deliver higher impact energy. This advantageously results in an increase in the velocity of the hammer unit and thus an increase in the impact energy of the hammer unit. Furthermore, the configuration of the striking mechanism unit according to the invention reduces the pressure of the gas volume compared to known hand-held power tools, which leads to a reduced load on the striking mechanism unit. As a result, vibrations of the hand-held power tool are additionally reduced.

In order to achieve a high pulse and energy transfer from the hammer unit to the tool, the velocity reached by the hammer unit during impact must be as high as possible. The acceleration of the striker unit required for this purpose can advantageously be achieved in that the device is provided for feeding gas into the machine chamber. This results in a structurally simple possibility for increasing the pressure in the machine room by, for example, introducing ambient air into the machine room. An increase in pressure leads to an increase in the resultant force on the hammer unit. As a result, the hammer unit returns to the folded-back position earlier, so that the maximum pressure drop is smaller and the hammer unit is accelerated to a higher impact or impact speed earlier. Consequently, subsequent impacts of the hammer unit deliver higher impact energy.

Furthermore, it is proposed that the device can be switched on and off. The free choice of pressure increase enables precise tuning of the vibration system. This results in a purposeful increase in the impact energy during operation of the hand-held power tool.

Furthermore, it is proposed that the device can be driven electrically or mechanically. This results in a particularly cost-effective solution, since a simple drive type can be used.

Furthermore, it is proposed that the device is at least partially driven by a drive of the hammer mechanism unit, whereby the hand-held power tool can be produced in a structurally simple and particularly cost-effective manner, since components already present in the hand-held power tool are used to drive the device.

In another configuration, it is provided that the drive of the hammer mechanism unit is designed as an eccentric mechanism. This results in a structurally simple and therefore cost-effective configuration of the drive.

If the hand power tool has a filter unit which is connected to the device and is arranged upstream of the machine compartment in the input direction, contamination of the hammer mechanism unit of the hand power tool is avoided and thus wear and tear is reduced and the hammer mechanism unit is prevented. failure.

An increase in the velocity and impact energy of the hammer unit is achieved in particular when the device generates a pressure in the machine compartment during operation of the hand-held power tool that is at least 0.3 bar above atmospheric pressure or air pressure.

In another configuration, it is provided that the device is a pump. This results in a particularly cost-effective solution for increasing the pressure since simple standard parts can be used.

Description of drawings

Additional advantages emerge from the following description of the figures. Exemplary embodiments of the invention are shown in the drawings. The drawings, the description, and the claims contain many combinations of features. A person skilled in the art can also expediently consider these features individually and combine other meaningful combinations.

Detailed ways

FIG. 1 shows a schematic diagram of a hand power tool 10 comprising a hammer drill with a machine compartment 12 . The machine compartment 12 is surrounded by a machine housing. In the machine chamber 12 there is a striking mechanism unit 14 comprising a hammer unit 16 and a piston unit 18 which are received axially one behind the other in a guide tube 32 and can be positioned in this guide Guided axially and bi-directionally in the tube.

A first end face 34 of the striker unit 16 and a first end face 36 of the piston unit 18 lie opposite each other and delimit a compression chamber 38 in which the gas volume 20 is enclosed. The hand-held power tool 10 has a control bore 22 designed as a perforation, which fluidically connects the gas volume 20 to the machine chamber 12 . The axis 40 of the guide tube 32 is coaxial with the axis of a tool holder 42 in which a tool 44 is receivable. In the present exemplary embodiment, the striker unit 16 acts on the tool 44 via an impact pin 46 which is likewise guided axially displaceably in the guide tube 32 . As an alternative, the striker unit 16 can also act directly on the tool 44 .

During operation of the hand-held power tool 10, the rotational movement of the drive device 26 is converted into a reciprocating movement of the piston unit 18 in that the piston unit 18 makes an axial reciprocating movement back and forth in the guide tube 32 starting from the initial position, wherein the compression The gas volume 20 in the chamber 38 is alternately compressed and unloaded. During the forward movement of the piston unit 18 , an overpressure is generated between the piston unit 18 and the hammer unit 16 , which accelerates the hammer unit 16 forward. The striker unit 16 accelerated by the compression pressure in the guide tube 32 outputs its kinetic or impact energy via the impact pin 46 to the tool 44 or conducts pulses to the tool 44 positioned in the tool holder 42 . During the backward movement of the piston unit 18 a negative pressure is generated in the compression chamber 38 which pulls the hammer unit 16 backwards.

In order to achieve a high pulse and energy transfer from the hammer unit 16 to the tool 44 , the hand-held power tool according to the invention has at least one device 24 provided for increasing the pressure p _M in the machine chamber 12 . The device 24 is provided for feeding gas or air into the machine compartment 12 . In the present exemplary embodiment, the device 24 is designed as a pump. Preferably, the device 24 generates a pressure p _M in the machine compartment 12 during operation of the hand-held power tool 10 which is at least 0.3 bar above the atmospheric or ambient pressure p _At . The device 24 can be switched on or off and is preferably electrically or mechanically actuatable. In the present exemplary embodiment, the device 24 can be driven at least partially by a drive device 26 of the striking mechanism unit 14 . In this case, drive 26 of hammer mechanism unit 14 is designed as an eccentric mechanism. The hand power tool additionally has a filter unit 28 which is connected to the device 24 and is arranged upstream of the machine compartment 12 in the input direction. The device 24 , which is designed as a pump, generally sucks in ambient air, which is therefore filtered before being fed into the machine room 12 .

Claims (8)

1. hand held power machine (10), have a machine chamber (12), and be arranged on percussion unit (14), a control hole (22) and at least one device (24) in this machine chamber (12), this percussion unit comprises ram unit (16), this ram unit can drive by gas volume (20) by a piston unit (18), described control hole couples described gas volume (20) and described machine chamber (12), and described device is arranged for the pressure (p that improves in the described machine chamber (12) _M), make the impulse member unit earlier get back in the folded back position of back in time, it is characterized in that described device (24) is a pump that constitutes dividually with described piston unit (18).

2. according to the hand held power machine of claim 1, it is characterized in that described device (24) is arranged for gas is input in the described machine chamber (12).

3. according to the hand held power machine of claim 1 or 2, it is characterized in that described device (24) can turn on and off.

4. according to the hand held power machine of one of aforesaid right requirement, it is characterized in that described device (24) can be by electricity ground or mechanically driving.

5. according to the hand held power machine of claim 4, it is characterized in that the drive unit (26) that described device (24) can pass through described percussion unit (14) at least in part drives.

6. according to the hand held power machine of claim 5, it is characterized in that the described drive unit (26) of described percussion unit (14) is configured to eccentric stiffener.

7. according to the hand held power machine of one of claim 2 to 6, it is characterized in that, be provided with a filter element (28), this filter element is connected to described device (24) and upward and at input direction (30) is arranged in described machine chamber (12) front.

8. according to the hand held power machine of one of aforesaid right requirement, it is characterized in that described device (24) surpasses atmospheric pressure (p in service generation of hand held power machine (10) in described machine chamber (12) _At) pressure (p of 0.3bar at least _M).

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