DE3241763A1 - MOWING MACHINE, ESPECIALLY LAWN MOWER - Google Patents

Description

10-1-14

description

Mower / especially lawn mower

The present invention relates to a voh one Electric motor-driven mower, in particular lawn mower, according to the preamble of claim 1. 10

The invention has particular application to lawn mowers that have wheels on iron or carried by an air cushion v / earth.

Many types of such mowing machines are driven by commutator motors, which are usually Series connection universal motors.

The present invention is based on the object to substantially alleviate some of the disadvantages inherent in these known machines.

This object is achieved according to the invention by the features specified in the characterizing part of claim 1.

The driven by an electric motor according to the invention The mower contains electronic circuitry for controlling the engine speed so that the speed of the Motor in the unloaded state is limited to a constant speed within specified limits of the motor load set, and to set at least one further lower speed of the motor, the lower is than the constant speed.

The following is an embodiment of the invention

explained in more detail with reference to the drawing. Show it;

Figure 1 ■

a perspective view of an air cushion lawn mower,

Figure 2.

an enlarged vertical sectional view through part of the lawn mower /

Figures 3 and 4

graphic representations, and

Figure 5.

a circuit diagram of a control circuit for the motor of the lawn mower. -

An air cushion lawn mower shown in Figure 1 has the external shape of a conventional lawn mower with a

2Q cutting edge housing 1, which has a cutting knife and a fan wheel encloses which is connected by an electric motor. in one on the top of the cutter housing 1 mounted motor housing 2 is housed. The movement of the mower is controlled by a handle 3 controls, at the outer end of which there is an on / off lever 4, with which the supply of electrical energy from a cable 5 connected to the mains to a line 6 connected to the input terminals of the motor is controlled.

FIG. 2 shows an enlarged cross-sectional view of the cutter housing 1 and the motor housing 2.

The cutter housing 1 has a top 8 with a from this downwardly projecting peripheral wall 9, which has an upwardly curved rim 10 on the outside.

_ 5 "

The top 8 has a circular central opening 11, which is surrounded by a wall 12 formed in one piece with the housing 1. The edge of the opening 11 is bent upwards, as indicated at 13. 5

An annular part 14 of a bearing for a motor 15 is arranged centrally with respect to the opening 11. from the part 14 extending at a distance (not shown) arms in the radial direction through which the bracket is attached to the cutter housing 1.

A front bracket 16 of the motor 15 is attached to the part 14. The holder 16 has a central approach 17, which is in the central opening of the annular part 14 seated. The approach 17 has, as can be seen from the drawing, a passage in which a ball bearing 18 for the lower end of an armature shaft 19 of the. Electric motor 15 is attached. ·.

The front bracket 16 is on the front side of a Sheet metal packet. 20 of the motor 15 fastened by means of bolts 21, which at the other end of the package ■ die'ringiform Fasten the underside of a second bracket on the face side. From the bracket 22 extend to internally inclined, spaced arms 23, the. Carrying carrier for brushes 25 containing brush boxes 24. The inner ones Ends of the brushes 25 have electrical contact with an armature 26 of the motor 15. In addition, the arms 23 a spherical bearing 27 for the upper earth of the armature shaft 19 based.

The arms 23 also support a speed control module 28, which will be described below.

The housing 2 enclosing the motor 15 contains a lower part 29 with an outwardly sloping wall 30,

the wall 12 surrounding the opening 10 somewhat overlaps and is separated from the wall 12 to form an inlet opening 31 is spaced.

The lower part 29 is shaped so that it forms an annular pocket 32 which lies between the central wall of the part and an intermediate wall 33 which is radially spaced from an inner wall 34 surrounding the package 20 and extends essentially as far as this. The inner wall 34 has an inner flange 35 on a The outer flange 36 of the front bracket 16 is arranged in order to position the part 29 of the motor housing 2.

The ring pocket 32 receives an air filter 37 of a suitable foamed or porous plastic material /. which is held in place by radial ribs 38. The radial ribs 38 extend from the curved. Wall 39 of the hood-shaped upper part 40 of the housing 2 towards the inside. . .

The top wall 41 of part 40 has one of a sight glass or transparent plastic covered central opening through which the end face of the armature shaft 19 is sighted can be used to determine their rotation. The top wall 41 also has a stepped portion 42 having an opening (not shown), the purpose of which will be described below.

At the lower end of the armature shaft 19, a fan wheel 43 is attached, the blades of which are very close to the opening 11 of the cutter housing 1 lie. In addition, a cutting rod 44 is attached to the armature shaft 19, which under the Fan wheel 43 is arranged. ·

The lawnmower described so far works as follows:

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When the motor 15 is excited, the fan wheel 43 rotates, whereby the inlet opening 32 and the opening 11 Air is sucked in to create an air cushion under the blade housing 1 which carries the lawnmower. In addition, air is drawn into the upper part 40 of the housing via openings (not shown) provided in the housing 2 2 sucked. This air passes through the filter 37, which frees the air from entrained material, and then the air flows upwards to the room between-'0 see the motor armature and the stack 20 and thereby support the cooling of the motor.

The cooling air flow exits via openings (not shown) in the front holder 16 and combines .15 with the air flow coming from the inlet opening 31 before entering the fan wheel. The rotating motor also rotates the cutting rod 43, whose outer ends cut off any plants that are in the path

of the cutting rod.
20th

In FIG. 3, curve A is the speed-torque characteristic a conventional series-wound commutator motor employing an air cushion lawnmower with that shown in the figures 1 and 2 drives the structure shown. The characteristic illustrates the known disadvantage of such motors that as the speed decreases, the torque increases. Such a decrease in speed affects the smooth and quiet cutting process with such a lawnmower. On long and / or wet grass, which makes the engine considerably easier loaded, the reduction in speed can lead to the fact that the lawnmower no longer cuts at all, ■

However, to ensure that even under heavy loads is cut, one can remember that it is only necessary to have a motor of greater power to use to a reasonable speed over

ι to ensure a larger torque range. this can be achieved by designing the engine so that it runs at a higher speed. One However, higher speed under load has the disadvantage that the speed in the unloaded state is excessive is great. If the speed is too high, there is an undesirably high energy consumption and a high level of noise hand in hand. ·.

Curve B in FIG. 3 is the characteristic curve of the motor corresponding to curve A, but which is electronically controlled in this way is that a constant speed is achieved in the beginning of the characteristic curve. The constant speed is chosen as required for effective cutting of long and / or wet grass.

In this way one counteracts the problem of too high speeds in the unloaded state, whereby at the same time a Excessive noise levels associated with high speeds is avoided.

A reduction in speed, a reduction in energy consumption and a reduction in the noise level are also achieved in comparison to a "standard" engine, the drives an air-cushion lawnmower.

A further reduction in the noise level and a further one Energy savings can be achieved in that the electronic control with a device which allows adjustment by the user and which reduces the engine speed, if circumstances permit. During the summer months, for example, the lawn does not grow as quickly, and therefore does only a "light" cut is required; this takes place at a lower engine speed.

SAD QRfGIWAL

In Figure 3, curves C and D relate to speed • or torque of the motor at two different reduced speeds.

Curves A, B, C and D in Figure 4 relate to the Torque of the motor in relation to the power consumption measured in watts. Curve A represents a conventional series-wound commutator motor that uses an air. drives cushion lawnmower, which was described above in connection with Figures 1 and 2, and that of the curve A in Figure 3 corresponds.

Curves B, C. and D in Fig. 4 are torque / power consumption characteristics of the electronically controlled motor when it is controlled so that its speeds
correspond to curves B, C and D in FIG.

It can be seen that in the case of curves B, C and D, compared to curve A, there is a considerable reduction in power consumption takes place in the unloaded or in the low-load state. In the case of curves C and D, the energy saving extends over a considerable range of torque values. .

In connection with the lower speeds this results Another advantage: The height at which the lawnmower is carried by the air cushion is slightly reduced. Through this a shorter cut is achieved.

Figure 5 is a circuit diagram of an electronic control circuit for the lawn mower motor. Leave with the circuit the behavior of the motor described above and other effects can be achieved.

The control circuit contains an integrated circuit
ULA type IC2 with a slow start ramp generator,

a frequency-voltage converter, a control amplifier, a trigger pulse generator and a current limiter. The engine speed is dependent on one of the engine associated speedometer coming signals regulated, via a wide speed range, for example above that through the horizontal starting section of curves B, C and D in Figure 3 marked area, the speed of the engine is kept at a constant value.

The speedometer expediently contains a Hall effect device, which generates a train of pulses, the frequency of which is proportional to the engine speed. This train of impulses arrives to the frequency-voltage converter, which converts the signals coming from the speedometer into a DC voltage signal converts whose. Amplitude is proportional to the frequency of the tachometer output pulses.

The output signal of the slow start ramp generator is matched with the output signal of the frequency-to-voltage converter compared by the control amplifier. This amplifier provides an output signal that controls the time setting

a trigger pulse generator controls. This one will used to trigger a triac CSR1 and thereby determine its firing angle. The triac is in series with the motor M between connections L and N.

The integrated circuit also contains the current limiter connected to the slow start ramp generator in order to absorb the current drawn by the lawnmower to limit a maximum current. If a current is drawn that is higher than a preset maximum value, the current limiter decreases the output of the slow start ramp generator, thereby reducing the Motor speed reduced so that the motor current decreases.

_7/8 BATHROOM ORIGSMAL

The speedometer is shown schematically in FIG. 5 as block IC1. The component contains a magnet, at Because it is a bar magnet or a ring magnet, which is mounted on a disk-like housing with the magnetic poles adjacent to the disc circumference are. The housing is attached to the armature shaft of the motor to rotate with the shaft, and it can be arranged next to the motor commutator. Close to the housing there is a carrier which, with respect to the Lawn mower housing is attached. The carrier owns about Cup farm, with the disc turning inside the cup. A Hall effect component, for example that of TL 170 CLP component sold by Texas Instruments Inc. is of this type on the curved wall of the carrier mounted so that there is a certain radial gap between the magnetic poles and the component, so that the output signal of the component is not influenced by a possible axial movement of the armature shaft.

The Hall effect component and the integrated circuit IC2 are connected to the mains L and N via a half-wave rectifier D1 and a voltage drop resistor R8 fed, with an electrolytic capacitor C9 as a filter is provided. A resistor R7, together with components provided in circuit IC2, forms a shunt stabilizer, in order to maintain a constant voltage at IC2 and the Hall effect component despite fluctuations in the electrical supply voltage. A additional electrolytic capacitor C8 forms an energy " memory for the current pulse required to ignite the triac CSR1.

The speed of the motor M is controlled via a potentiometer RV1, which is placed between the ground line and the Pin 8 of IC2 is switched. The grinder arm of the Po-

tentiometer RV1 can be operated by a button or lever which is arranged on the housing 2 and shown in FIG. 1 is indicated schematically at 7. The button or lever preferably has locking positions, one of which is the 5 Select the higher speed of the motor mentioned above and the others the lower speeds. Of course only an intermediate position can be provided if desired. The button 7 has a shaft that runs through it the above-mentioned opening in the stepped section 42 of the top wall 41 of the part 40 of the housing 2 extends. The shaft preferably has a number of elastic fingers which close when passing through the opening in order to then return to their starting position. in which they prevent the shaft from being easily pulled out. In addition, the shaft end is shaped so that it with appropriately designed surface parts of the shaft of the potentiometer RV1 in only one direction of orientation of the button engages.

in the circuit of Figure 5, the pins relate 1 and 4 of the IC2 to the control amplifier, and they are connected via a capacitor C3, which works as an integrator.

A capacitor C4 connected to pin 6 of IC2 determines the slope of the "slow" start, that is, the acceleration of the engine with which it goes through Set the potentiometer RV1 connected to pins 7 and 8 of IC2 at the selected speed be ^ - accelerates.

A capacitor C5 connected to pin 10 of IC2 determines the conversion factor of the frequency-to-voltage converter. The resistor-capacitor arrangement CI, R2 forms a filter circuit for the output signal of the frequency-voltage converter. A capacitor C2 takes care of

BATH ORIGINAL

32A1763

an additional filtering.

The pin 12 of IC2 is connected to a capacitor C6 which is the timing ramp for the trigger pulse generator supplies. The input signals delivered to input pins 13 and 14 through a resistor R 6 and R5, respectively provide input signals for the voltage

• and current synchronization of the trigger pulse generator.

The average current is limited by IC2 based on an input signal on pin 18 of IC2, which is received through a resistor R3, while a capacitor C7 does the averaging takes over for this input signal.

A resistor-capacitor arrangement R9, C1O leading to connected in parallel to the triac CSR1, limits the voltage rise at the triac and thus reduces the probability false triggering if the triac

switches. ·

The values of the individual components are given in FIG.

The electronic control circuit can expediently be accommodated in the housing 2 and arranged in such a way that that it is cooled by a stream of air, for example clean air, which is applied to the motor to cool it sweeps past.

In the shown construction in Figure 2, the integrated circuit IC2 and their associated discrete components on a printed circuit board are arranged, which forms a module 28th The Hall effect sensor 45 assigned to the tachometer is mounted on an extension of the module 28, while the rotary magnet arrangement is schematic

at 46 is indicated.

It can be seen that the mower is alternatively a moving or driven machine can, that is, a machine with a chassis equipped with wheels, the one around a vertical axis an electric motor carries rotatable cutting blade. It can also be a roller mower. The mower can also be constructed in such a way that a piece of thread is used as the cutting element, or that several. Cutting

Devices are used that can pivot on one. j carrier are attached, which is used as a drive device of

the engine is rotated.

Claims (3)

BLUMBACH. WE3ER ". B0ERGEIM · KRAlVlER ZWiRNER. HOFFMANN PATENTANWÄLTE IN MUNICH AND WIESBADEN Patentconsull RadeckestraOe 43 8000 Munich 60 Telelon (089) 883603/883604 Telex 05-212 513 Telegrarnmo99 Patentconsull Patentconsult (044300121 Sonnenberger Straße 43 62/561 Wiesbaden) Telegrarnmo99 (064300121 Sonnenberger Strasse 43 62/561 Wiesbaden) Telex 5629 186 237 telegrams Palonlconsull BLACK & DECKER INC. 10-114 Newark, Delaware 19711, USA Dr / sc mower, in particular lawn mower claims 1. Mower driven by an electric motor (15). in particular lawn mower, with an electronic circuit for controlling the engine speed, characterized in that the circuit (Figure 5) limits the engine speed in the unloaded state in order to set a constant speed within predetermined limits of the engine load , and to set at least one further engine speed that is differs from the mentioned constant speed, and which is also constant within predetermined limits of the engine load. 2. Mower according to Claim 1 , characterized in that the electronic circuit contains a module which is in a housing which accommodates the motor (15) (2) Mounted in a location where there is a flow of cooling air is exposed". Munich: R. Kramer Dlpl.-lng. . W. Weser Oipl.-Phys. Dr. rer. nai. . E. Hoffmann Dipl.-Ing. Wiesbaden: P.G. Blumbadi Dipl.-Ing. P.Bergen Prof.Dr.Jur.Dipl.-Ing., Pat.-Ass., Pat.-Anw. until 1979. G. Zwirner Dipl.-Ing. Dipl.-W.-Ing. * ■ 1 3. Mower according to Claim 2, characterized in that the cooling air flow is generated by a fan wheel (43) rotated by the motor (15), which also generates an air cushion during operation 5 shows that the mower carries. BATH ORIGINAL