JPS6134951B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a drilling hammer having an impact mechanism and an internal combustion engine, and in which a crankshaft of the internal combustion engine is connected to a crank that reciprocates a driving piston of the impact mechanism by a connecting rod.

This type of drilling hammer is used where a fairly high breaking and working performance is required. The internal combustion engine used for the drive is usually a so-called two-stroke engine. Compared to four-stroke engines, this type of construction has a simple structure and low weight relative to performance. Two-stroke engines are typically used in hand-held tools and machinery for reasons of weight and cost.

On each working stroke, the two-stroke engine replaces the benzine, air (or gasoline, air) mixture to be scavenged, ie the combustion gas produced in the cylinder, and supplies fresh pyrotechnic charge gas to the engine. A pump is required to force the mixture into the cylinder. In fact, in all two-stroke small engines, the engine crankcase itself is used as a scavenging pump. However, this comes at a considerable cost. The crankshaft bearing locations and the connecting rod bearing locations, as well as the cylinder walls, must be properly lubricated. The lubricating oil is washed away in a very short time due to the flow of the gasoline-air mixture, so that if no countermeasures are taken, the engine will be destroyed in a very short time. To overcome this problem, a gasoline-oil mixture is used in two-stroke engines. The role of oil is to lubricate the moving parts and mechanisms of an engine. Gasoline is an energy carrier during combustion.

The oil that enters the combustion chamber is only incompletely combusted during the combustion of the gasoline-air mixture, resulting in the production of troublesome blue exhaust smoke.

The efficiency of conventional two-stroke engines is usually comparable4
lower than the efficiency of cycle engines. This low efficiency is mainly due to the scavenging loss that occurs in the scavenging air of the combustion chamber. In the case of fairly large stationary engines or engines mounted on vehicles, significant consumption generally occurs in the scavenging air of the combustion chamber. Thus, for example, turbo blowers, rotary slip blowers and piston pumps are known for this purpose. However, in the case of portable tools such as drilling hammers, such measures are completely out of the question for reasons of weight.

The object of the present invention is to obtain a drilling hammer equipped with an internal combustion engine, which achieves high efficiency due to good scavenging and has a suitable output despite the overall weight of the hammer.

To achieve this objective, the drilling hammer of the present invention separates the crank chamber of the impact mechanism in which the crank of the impact mechanism is arranged from the rest of the hammer, and provides an intake valve in the crank chamber of the impact mechanism;
The intake valve is characterized in that the intake valve communicates with an intake hole communicating with a combustion chamber of the internal combustion engine through an outflow opening.

Due to the separation of the crank chamber of the impact mechanism from the rest of the hammer, this crank chamber can be used as a scavenging pump for the engine. Since the stroke volume of the shock mechanism for a given two-stroke engine corresponds approximately to the stroke volume of the engine, the crankcase of the shock mechanism properly acts as a scavenging pump for the engine. Crankshaft installations are often located within the engine crankcase, and the drive pistons are usually lubricated from an impact mechanism. The connecting rod bearings of the impact mechanism can be designed without problems with sealed, grease-lubricated bearings. Lubrication of the crankcase of the impact mechanism is therefore not necessary. Since the engine's crank chamber does not come into contact with the fuel-air mixture in the case of a carburetor engine or the intake air in the case of a fuel-injection engine, the lubrication of the crankshaft bearing, the connected rod bearing, and the engine's cylinder chamber is prevented. It is possible to plan from an optimal perspective. Thus, for example, splash lubrication or oil atomization lubrication can be used. The incoming fuel-air mixture therefore does not have to perform any special lubricating action. It is therefore possible to operate the tool without using a two-cycle oil mixture, which has a positive effect on operating costs and emissions.

Known two-stroke engines have further drawbacks.
During scavenging, a portion of the fuel-air mixture passes through the exhaust port and is discharged to the outside air through the exhaust pipe as scavenging loss. 2
It is practically impossible to avoid this in cycle engines. The result is high fuel consumption, and since this lost fuel is not involved in the combustion process, a high proportion of unburned toxic gases escape through the exhaust pipe.
In the case of so-called fuel-injected engines, this can be avoided since the scavenging is done with fresh air. Then, as soon as the piston covers the control hole and makes the combustion chamber airtight, fuel is injected by the high-pressure injection nozzle. Three advantages result from this method. As a result of the subsequent injection of fuel, the performance is clearly improved, the fuel consumption is clearly reduced and the emissions are significantly improved. The scavenging method according to the invention using the crankcase of the percussion mechanism is suitable for both carburetor engines and fuel injection engines.

In operation, the ignitable mixture enters through the carburetor and air through the air filter through the intake valve. Although this method is particularly suitable for internal combustion engines that operate on the two-stroke principle, it can also be used as a so-called booster for four-stroke engines, so that the performance can be improved in the same way as with two-stroke engines. The solution according to the invention is particularly simple and, compared to conventional internal combustion engine-driven drilling hammers, requires a connecting pipe from the outlet opening of the separate chamber to the intake hole of the engine and an intake valve. Only. Therefore, the measures required in the present invention add virtually no weight.

In order to simplify the construction of the drilling hammer, it is advantageous for the end face of the drive piston facing the connecting rod to form a wall of the chamber that is separate from the rest of the hammer. This impact mechanism is a compressed air impact mechanism, which seals the drive piston reciprocating in the cylinder against an air cushion placed between the drive piston and the impact piston containing the aforementioned engine, so that various additional measures may be taken. There's no need. The compression of the incoming air or mixture in the separate chamber can be determined in an optimal manner by determining the crank stroke as well as the dead air within an independent specific range of the drive engine.

Since the configuration of the invention has a chamber separate from the rest of the hammer, new possibilities appear compared to known tools in which the crank of the percussion mechanism and the crank of the drive engine are arranged in a similar chamber. Conventional 2
In a cycle engine, an air-fuel mixture flows through the engine's crankcase and is primarily compressed during the expansion stroke of a combustion chamber within the crankcase. Immediately before reaching the bottom dead center, the outflow passage is opened by the piston, allowing the primarily compressed air-fuel mixture to flow into the combustion chamber from the crankcase. However, as the crank rotates further, the pressure in the outflow passage in the crankcase decreases again, so that the flow into the combustion chamber decreases. For this reason, scavenging of the combustion chamber is only possible incompletely. If the scavenging pressure is increased by reducing the size of the crank chamber using other methods, most of the ignitable air-fuel mixture may escape through the exhaust hole as scavenging loss, unburnt, which will reduce fuel efficiency. leading to an increase in By the way, in an optimal manner, the engine crankshaft should be adjusted so that the impact mechanism lags the engine by a crank displacement (or angle between cranks) of 10° to 60° in order to be able to adapt the scavenging pressure to the scavenging stroke. It is advantageous to offset the crank of the impact mechanism with respect to the impact mechanism. In this way, starting from the bottom dead center of the piston of the engine, it is possible to deliver sufficient scavenging pressure as the crankshaft rotates further until the intake or outlet hole is again blocked by the piston. Since the impact mechanism is connected to the crankshaft, the displacement of this crank is always the same.

In practice, a crank displacement (or angle between cranks) of 40° has proven effective. And this result achieves sufficient scavenging pressure at a given location of the intake or outlet hole until the intake or outlet hole is closed, which prevents backflow of various scavenging air and is better than that achieved by crankcase scavenging. , allowing much better scavenging. On the other hand, in opening the intake hole,
Since the pressure drop and the degree of change between the scavenging pressure and the pressure inside the combustion chamber are small, flowing steam can be formed inside the combustion chamber, and the fresh inflow mixture separates most of the combustion gases passing through the exhaust hole.

The invention will be explained in detail with reference to the following drawings.

Illustrated in FIG. 1 is an embodiment of a drilling hammer according to the invention, comprising a housing designated by the reference numeral 1. FIG.
A handle 2 is attached to the rear end of the housing 1. A tool holder 3 is arranged at the end of the housing 1 remote from the handle 2. A crankshaft for an internal combustion engine is indicated at 4 and is rotatably mounted in the housing 1, and a connecting rod 5 is connected to the crankshaft 4 via a crank pin 4a. The connecting rod 5 is then connected to the piston 6.
This piston 6 is guided within the cylinder 1c.
At the upper end of the crankshaft 4, a crank designated by the reference numeral 7 is connected to the crankshaft 4 via a threaded groove 4b. The connecting rod 8 of the hammer impact mechanism is attached to the crank pin 7a of the crank 7. The connecting rod 8 is then connected, for example, to a drive piston 9 of a compressed air percussion mechanism. This drive piston 9 is guided in a sleeve 10. The impact mechanism is thus coupled to the internal combustion engine.

An intake valve 11, designated 11, is arranged in the housing 1 in the area of the crank 7. Intake valve 11
The inner ball 11a is pressurized against the valve seat 11c by a spring 11b. The intake valve 11 acts as a check valve or a one-way valve. When the drive piston 9 moves in the direction of the tool holder 3, air or a mixture of fuel and air flows through the intake valve 11 into the chamber 1a in which the crank 7 and the connecting rod 8 act. Chamber 1 is sealed by seal 12 to the rest of the housing.
Seal a. This chamber 1a further has an outflow opening 1a.
has. The pipe 13 is connected to the cylinder 1 from the outflow opening 1d.
It is electrically connected to the air intake hole 1e in the wall of c. When the drive piston 9 changes direction and moves towards the handle 2, the volume of the chamber 1a decreases and the air or air/fuel mixture that has entered it is discharged through the tube 13. When the piston 6 opens the intake hole 1e, air or air-fuel mixture can flow into the combustion chamber. Next, in the previous cycle, after ignition already the combustion chamber 1
The combustion waste gas contained in the chamber 6 is exhausted through the exhaust hole 1f. The technical term for this is "scavenging".
It is called. In carburetor engines, this scavenging is accomplished by means of a pyrophoric fuel-air mixture. This has its own (or potential) disadvantage that part of the air-fuel mixture may be lost through the exhaust hole 1f, and the efficiency of the internal combustion engine is correspondingly reduced. For fuel-injected engines,
Scavenging, on the other hand, is done with pure air. Fuel is injected into the combustion chamber 1b through an injection device (not shown) only when both the intake hole 1e and the exhaust hole 1f are closed. This of course has an effect on efficiency.

Flywheel 1 at the lower end of crankshaft 4
Place 4. This is customary in internal combustion engines. On the other hand, this flywheel 14 balances the power consumption of the engine during the compression stroke as well as the impact action of the impact mechanism and the output of the internal combustion engine. Furthermore, the flywheel serves as a generator to generate the ignition voltage, which flows through the cover 15 and
It additionally serves as an impeller to provide a flow of cooling air blowing through the cylinder 1c.

FIG. 2 shows this device cut along line A--A in FIG. 1, and the parts clearly shown here are the main parts of the engine of this device. The drive piston 9 was opened at top dead center. On the other hand, the piston 6 has already passed through its top dead center in the direction of rotation D. Since the crank pin 7a of the impact mechanism is offset by an angle α with respect to the crank pin 4a of such an internal combustion engine, the impact mechanism lags behind the internal combustion engine by an angle α.

When the crank 7 further rotates, the volume of the chamber 1a decreases again, and the air or air-fuel mixture held inside is blown out through the outflow opening 1d. Compared to conventional two-stroke engines, where the engine crankcase acts as a scavenging pump, this delay in the shock mechanism for the internal combustion engine prevents backflow of the mixture since the scavenging pressure is higher than the pressure in the combustion chamber during the entire scavenging. There are benefits to be gained.

FIG. 3 shows the same engine part as FIG. 2, but with the drive piston 9 located at bottom dead center. The crank pin 4a of the piston 6 has already passed the position of the crank pin 7a of the crank 7. The air or fuel-air mixture entering the combustion chamber from the chamber 1a through the outlet opening 1a and the intake opening 1e is therefore compressed. In this position, the power required for the impact mechanism is low. In this way, fly hole 1
The energy stored in combustion chamber 4 is essentially
can be fully used for the compression of the fuel-air mixture contained in b. A phase shift between the impact mechanism and the internal combustion engine therefore gives good results.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway side view of the drilling hammer of the present invention; Fig. 2 is a schematic cross-sectional view taken along line A-A in Fig. 1 showing the engine and impact mechanism at the top dead center of the drive piston; FIG. 3 is a schematic sectional view similar to FIG. 2 at the bottom dead center of the drive piston. 1...Housing, 1a...Chamber, 1b...Combustion chamber, 1c...Cylinder, 1d...Outflow opening, 1e
...Intake hole, 1f...Exhaust hole, 2...Handle,
3...Tool holder, 4...Crankshaft, 4
a...Crank pin, 4b...Thread groove, 5...Connection rod, 6...Piston, 7...Crank, 7
a...Crank pin, 8...Connection rod, 9...
Drive piston, 10...Sleeve, 11...Intake valve, 11a...Ball, 11b...Spring, 11c...
Valve seat, 12...Seal, 13...Pipe, 14...Flywheel, 15...Cover, D...Rotation direction, α...Angle.

Claims (1)

[Scope of Claims] 1. A drilling hammer having an impact mechanism and an internal combustion engine, in which a crankshaft of the internal combustion engine is connected to a crank that reciprocates a driving piston of the impact mechanism by a connecting rod. separating the crank chamber of the impact mechanism in which the impact mechanism is arranged from the rest of the hammer, providing an intake valve in the crank chamber of the impact mechanism, communicating the intake valve by an outflow opening with an intake hole leading to the combustion chamber of the internal combustion engine; A drilling hammer characterized by: 2. A drilling hammer according to claim 1, characterized in that the end face of the drive piston facing the connecting rod is formed with a wall of the crank chamber of the impact mechanism, which is separate from the rest of the hammer. 3. Any one of claims 1 and 2, characterized in that the crank of the impact mechanism is angularly displaced with respect to the crank of the internal combustion engine so as to lag rearward at a displacement angle of 10° to 60°. Perforating hammer as described in . 4. The drilling hammer according to claim 3, wherein the displacement angle of the crank is approximately 40 degrees.