CN1198049C - Two-stroke IC engine - Google Patents

Abstract

The present invention relates to a two-stroke internal combustion engine (1) with a scavenged crankcase. At least one air passage with the length of Lai is arranged between an air inlet (2) and scavenging holes (31, 31') of a plurality of transferring pipelines (3, 3'), the air passage uses a piston as a valve, the transferring pipelines (3, 3') have the length Ls from the scavenging holes to the crankcase. The present invention is characterized in that the air passage is arranged from the air inlet, and the air inlet is provided with a throttling valve (4) which is controlled by at least one engine parameter. For example, the throttling valve is controlled by the throttle of a vaporizer. The air inlet extends to at least one connecting hole (8, 8') on the cylinder wall (12) of an engine through at least one connecting pipeline (6, 6'). The connecting holes are arranged as the following: when the piston is positioned at an upper dead point, the connecting holes are connected with flowing passages (10, 10') in the piston (13), and the flowing passages extend to the upper parts of the transferring pipelines (3, 3'). Each flowing passage in the piston is arranged as the following: notches (10, 10') in the piston crossed with each of the scavenging holes (31, 31') are arranged as that the air supply period is fundamentally long as the same as inlets (22 to 25) of the engine. The air supply period is expressed as a crank angle or a crank time, and the length Li of an inlet for feeding fuels is 0.6 time as much as the sum of the length Lai of the air passage using the piston as the valve and the length Ls of the transferring pipelines, namely 0.6 time (Lai + Ls), and is 1.4 times as little as the length of the sum of the length Lai of the air passage and the length Ls of the transferring pipelines, namely 1.4 times (Lai + Ls).

Description

Two-stroke internal-combustion engine

Technical field

The present invention relates to the internal-combustion engine of two-stroke crankcase scavenging, wherein, is that the air passageways of valve is arranged between the top of air intlet and a plurality of transfer canals with the piston.Fresh air adds the top of transfer canal to, and will be as the buffer agent (buffer) of the air/fuel mixture of back.The major part of this buffer agent flows out in the relief opening in scavenging process.Therefore, can reduce fuel consumption and exhaust emission.This motor is mainly used in hand-held tool.

Background technique

For a long time with regard to the combustion engine of known the above-mentioned type.They have reduced fuel consumption and exhaust emission, but restive air/fuel ratio in this motor.

US5425346 has represented a kind of motor, and the design of this motor and above-mentioned situation be difference a bit.At this moment, be furnished with conduit in the piston of motor, this conduit is at specific piston position, and with the pipe alignment that is arranged in the cylinder.Therefore, as shown in Figure 7, fresh air or exhaust can be added the top of transfer canal to.This situation can only take place at specific piston position, at this piston position, and the pipe alignment in piston and cylinder.And this takes place when moving upward away from top dead center when piston moves downward and when piston.Flow in order to prevent to form under latter event along the undesirable of the opposite way round, one-way valve is arranged in the inlet on the top of leading to transfer canal.The one-way valve of the type is commonly referred to leaf valve, and but, the type one-way valve has some shortcomings, and they often resonate, and are difficult to handle high speed conditions, and this high rotating speed be a lot of two-cycle engines can reach.In addition, it causes increasing cost and increases the engine components number.The amount of the fresh air that is added changes by variable inlet, promptly changes by the import that can shift to an earlier date in work cycle or lag behind.But, this is very complicated method.

International Patent Application WO 98/57053 has been represented a kind of slightly different motor embodiment, and wherein, air is by L shaped or and the T shape recess supply transfer canal in the piston.Therefore, there is not one-way valve.In whole embodiments, piston recess has very limited height in it and each transfer canal place of meeting, and this equals the height of actual transfer port highly substantially.This embodiment's a result is, air pass to by piston transfer port passage open obviously be later than undertaken by piston, make air/fuel mixture lead to the opening of passage of crank box.Therefore, during supplying with, air, wherein, may be calculated degree in crank angle or time during this period obviously than short during the supply of air/fuel mixture.This makes the control of total air/fuel ratio of motor become complicated.This amount that also means the air that can pass to transfer canal is obviously limited, because low-voltage driving, this additive air will reduce in a large number, because in during air is supplied with open a certain, this inlet hole is always opened.During this means that air supplies with and driving force all very little.And, shown in L shaped and the ducted flow resistance of T shape with relative higher, this part since the cross-section area of pipeline less relatively near the transfer port place, part is because sharp bend L shaped or that T shape causes.In a word, this will increase the amount that flow resistance and reducing can pass to the air of transfer canal, thereby the possibility that reduces fuel consumption and exhaust emission by this device is reduced.

Summary of the invention

The objective of the invention is obviously to reduce the problems referred to above, and obtain lot of advantages.

Above-mentioned purpose can realize by two-stroke combustion engine of the present invention, and this two-stroke combustion engine is as described in the characteristic in the additional claim.

Therefore, major character according to combustion engine of the present invention is: air passageways begins to arrange from air intlet, this air intlet is equipped with throttle valve, this throttle valve is by at least one engine parameter control, for example vaporizer throttling control, described air intlet is directed at least one attachment hole on the engine air casing wall by at least one connecting tube, this attachment hole is arranged to like this, when piston is positioned at upper dead center, the flow passage of the recess form in this attachment hole and the piston links to each other, this flow passage extends to the top of transfer canal, and this flow passage is arranged to like this, that is, the same long with intake period basic and internal-combustion engine during recess in the piston that intersects in the hole of each transfer canal is arranged to make air to supply with, this air is expressed as degree in crank angle or time during supplying with, and adds the length L of the import 22-25 of fuel _iGreater than with the air path length L of piston as valve _AiWith the transfer canal length L _s0.6 times of sum, i.e. 0.6 times of (L _Ai+ L _s), but less than 1.4 times of this length, i.e. 1.4 times of (L _Ai+ L _s).

Guide air between the length of the length of pipeline of crank box and inlet pipeline relation by changing, can simply carry out the control of motor.By changing the correlation of these two systems, the flow in each system can change simultaneously with the flow in another system.Like this, no matter the variation of load etc. how, the vaporizer in inlet system will be supplied with correct fuel quantity to motor.

Because at least one attachment hole in the engine air casing wall is arranged to when piston is positioned at upper dead center, it links to each other with flow passage in the piston, and fresh air can be arranged to there is not one-way valve fully to the supply on transfer canal top.This is because be in or during close upper dead center, transfer canal is a low pressure with respect to ambient air when piston.Therefore, be that the air passageways of valve can not have one-way valve with the piston, this is a very big advantage.Because air is very long during supplying with, can transmit very a large amount of air, therefore can reduce exhaust emission significantly.Control is undertaken by the throttle valve in the air intlet, and by at least one engine parameter control.The obvious variable ratio import of such controlling Design simplicity of design.Preferably, air intlet has two attachment holes, and in one embodiment, these two attachment holes are arranged to cover them when piston is in lower dead centre.Throttle valve can be only by engine speed control, perhaps with other engine parameter composite control.These and other characteristic will be known expression with advantage in to different embodiments' shown in the drawings detailed description.

Brief description of drawings

To and introduce the present invention in greater detail with reference to the attached drawings by various embodiments below.For the parts that are arranged symmetrically on the motor,, and represent with same numbers at the parts of opposite side with numeral at the parts of a side, but add ' number.In the accompanying drawings, band ' number parts be positioned at paper plane above, therefore cannot see.

Fig. 1 has represented the side view of motor of the present invention.Cylinder is represented with cross section, and piston is expressed as at upper dead center.

Fig. 2 is expressed as corresponding common engine.In order to explain the present invention, an imaginary partition wall places in the engine intake pipeline, and is shown in dotted line.

Embodiment

In Fig. 1, reference number 1 expression internal-combustion engine of the present invention.It is two stroke type, and have transfer canal 3,3 '.Transfer canal 3 ' cannot see because it be positioned at paper plane above.This motor has cylinder and crank box 16, piston 13, and this piston has connecting rod 17 and crank mechanism 18.And this motor has inlet tube 22 with inlet hole 23 and the intermediate portion 24 that links to each other with this inlet tube, and this intermediate portion 24 links to each other with the vaporizer 25 with throttle valve 26 again.Usually, vaporizer links to each other with the import baffler that filter is arranged.For clear, do not represent these.Also by the same token and the not expression of the exhaust port of motor, exhaust duct and baffler.They are usually located on side cylinder, relative with import.Do not have step or analog on the upper side plane of piston, therefore, any position on the periphery all cooperates equally with cylinder-bore.Therefore, the height of engine block is compared with common engine almost and is not changed.Hole 31 and 31 on engine air casing wall 12 of transfer canal 3 and 3 ' have '.This motor combuster 32, there is unshowned spark plug this firing chamber 32.All these is a normal elements, does not therefore further specify.

Particularly, the air intlet 2 that is equipped with throttle valve 4 is arranged so that fresh air can supply cylinder.The connecting tube 6 of these air intlet 2 oriented cylinder flutings.From now on, attachment hole is meant the hole that is connected cylinder interior, and is called outer connecting port in the hole of cylinder outside.Air intlet 2 is suitable for linking to each other with the import baffler by filter, like this, will suck the fresh air of cleaning.When requiring to reduce, this filter is not necessary certainly.For clear, do not represent the import baffler.

Like this, connecting tube 6 links to each other with outer connecting port 7.So very favourable.At place, this hole or behind this hole, this pipeline be divided into two branches 11,11 ', these two branches lead respectively attachment hole 8,8 '.Their symmetric arrangement, as previously mentioned, have ' parts be positioned at paper plane above.Like this, outer connecting port 7 be positioned at inlet tube 22 below, this means a plurality of advantages, for example air temperature is low and can utilize the space of the hand-held tool that fuel tank is arranged usually better.

But, attachment hole 7 can also be positioned at inlet tube 22 above, at this moment the direction of this inlet tube will be more level.No matter where they are positioned at, can adopt two outer connecting ports 7,7 '.They also can be positioned at the both sides of this inlet tube 22.

Flow passage 10,10 ' be arranged in the piston, like this, when piston is in the upper dead center position place, flow passage make each attachment hole 8,8 ' with transfer canal 3,3 ' top link to each other.This flow passage 10,10 ' form by the partial notch in the piston.This piston has simply manufactured this partial notch, makes by casting usually.

Usually, attachment hole 8,8 ' be arranged on the cylinder axial direction when piston is positioned at its lower dead centre, to cover this attachment hole 8,8 '.Therefore, exhaust can not be passed this attachment hole and further be flowed to presumable air filter.But, can also make attachment hole 8,8 ' the position improve, like this, when piston is positioned at its lower dead centre, this attachment hole 8,8 ' a part open.Therefore, the exhaust of appropriate amount will supply in the connecting tube 6.Improve the position of attachment hole can also reduce air in the flow resistance when attachment hole turns to transfer port 31.

Air is from attachment hole 8,8 ' extremely important to the time of transfer port 31,31 ' supply, and it by the decision of the flow passage in the piston, is promptly determined by the recess in the piston to a great extent.

Preferably, the position height of the top edge of this recess is for like this, and when piston upwards arrived the lower limb in each hole 31,31 from lower dead centre, the lower limb of piston upwards arrived the lower limb of inlet hole.Therefore, attachment hole 8,8 ' and transfer port 31,31 ' between air connect and open, import is simultaneously opened.When piston again when upper dead center moves downward, air connects and import will be closed simultaneously, so provides the isometric substantially time.Wish that inlet period and air period are isometric substantially.Preferably, air period is the 90%-110% of inlet period.Because during these two all by limiting during the enough low maximum of the pressure in the crank box, thereby can have maximum to become a mandarin.Preferably, all maximum and isometric during these two.Therefore, recess 10,10 ' upper marginal position determined how early this recess is can and each transfer port 31,31 ' contact respectively.Therefore, preferably, respectively with the piston inner recess 10,10 in each hole 31,31 ' intersect ', preferably greater than 2 times of the height of transfer port at the localized axial height at this place, hole 1.5 times greater than the height of each transfer port.This makes this hole can be normal height, and like this, when piston was positioned at its lower dead centre, the end face of piston and the bottom surface of transfer port were contour, perhaps only protrude several millimeters.

Preferably, this recess form downwards make recess 10,10 ' and attachment hole 8,8 ' between the connection maximum because this will reduce flow resistance.This means that when piston was positioned at its upper dead center, preferably recess reached such lower position, promptly do not cover fully attachment hole 8,8 ', as shown in Figure 1.Generally speaking, respectively with the piston inner recess 10,10 of each attachment hole 8,8 ' intersect ', preferably greater than 2 times of this attachment hole height at the localized axial height at this place, hole 1.5 times greater than the height of each attachment hole.

Attachment hole 8,8 ' and transfer port 31,31 ' relative position sizable variation can be arranged, as long as this hole is laterally staggered, the tangent direction of promptly grinding cylinder is staggered, as shown in Figure 1.Fig. 1 has represented attachment hole and transfer port 31,31 ' the have situation of axial overlap, and promptly the top edge of each attachment hole is contour or be higher than this lower limb with the lower limb of each transfer port along laying respectively on the axial direction of cylinder.Such advantage is that two holes can be in alignment with each other in the type device more, and this can reduce flow resistance from attachment hole at air when transfer port is carried.Therefore, can carry more air, this can improve the good effect of this device, promptly reduces fuel consumption and exhaust emission.For a lot of two-cycle engines, when piston was in lower dead centre, the lower limb of the end face of piston and the lower limb of exhaust outlet and transfer port was contour.But, also normally, piston reaches above the transfer port lower limb one millimeter or several millimeters.When the lower limb of transfer port further reduces, can between attachment hole and transfer port, form even bigger axial overlap.When air is supplied with scavenging air belt, because the hole is in alignment with each other more and because transfer port has bigger surface area, this makes flow resistance reduce.

The present invention includes two important principles, be used for changing or regulating this two pipe-line systems.A principle is, when the import that air/fuel mixture leads to crank box is opened, opens the supply of air to transfer canal substantially.This has been described in detail in front.Another principle is that the length in two systems can be regulated each other.By study Fig. 2, this principle can be described better, Fig. 2 has represented a kind of corresponding common engine, this common engine is not used in the air supply system of transfer canal.In this common engine, there is not partition wall 36, shown in dotted line in the inlet pipeline.Therefore, this common engine has only an inlet pipeline, in this inlet pipeline, whole suction air flow stream overflash device and with 37 effects of fuel stream, thereby form suitable air/fuel ratio, because the amount of fuel that vaporizer is supplied with to motor and inlet air is proportional.Therefore, when the piece-rate system that is furnished with as Fig. 1,, have only air to pass through connecting tube 6, and air/fuel mixture will be by import 22-25 so that when the motor air supply.Therefore, have only the smaller portions process vaporizer of the inlet air amount of motor, the fresh air stream in connecting tube 6 will can not influence the fuel stream 37 in import.But, owing to the both duct systems that can regulate specially in this motor, therefore can also come they are carried out identical pneumatic adjusting.This can arrange a longitudinal subdivision wall 36 and understand in the simplest mode by imagination in the common engine of Fig. 2.This partition wall 36 does not change their characteristic and feature simultaneously with the inlet tube separated into two parts.All fuel 37 is all supplied with the part of this pipe.The variation that is proportional to one another of flow in the two-part that in this pipe, separate by this partition wall 36.For example, when the flow in the part doubled, the flow in another part also doubled.Basic principle is that the characteristic and the feature of this inlet tube can not change, because this area by the longitudinal subdivision wall separately.Below, when forwarding this principle to Fig. 1, at this moment we have inlet system, i.e. import 22-25, and all fuel 37 are all supplied with this import 22-25.The length of inlet system is L _i, as shown in FIG..This length can increase or reduce, and this is shown in the cut-out near place, inlet tube outer end.Another inlet system that is used for fresh air stretches out from air intlet 2, and until the mouth 38 of transfer canal 3 in crank box.This comprises two parts.With L _AiThe first portion of expression stretches out from import 2, and until the mouth of transfer port 31.Therefore, it passes connecting tube 6 and is connected branch's 11 extensions, and passes attachment hole 8, passes piston recess 19 then, up to transfer port 31.Obviously, this is the situation that is positioned at the position of close upper dead center when piston, and at this moment, piston recess 10 makes two holes 8 link to each other with 31.The length L of 38 transfer canal from transfer port 31 to mouth _sThe back part of expression air inlet system.Therefore, the total length of this system is L _Ai+ L _sThis connecting tube 6 represents that with divided mode this is can change for the length of pointing out it.In order to shorten length L _Ai+ L _s, can be so that air intlet 2 close outer connecting ports 7.Work as length L _iBasic and length L _Ai+ L _sWhen equally long,, also can in different speed and loading range, obtain stable air/fuel ratio even all fuel all supplies in the normal import.Especially, you can get the lower part of the inlet pipeline among Fig. 2, and with its air conduit as the outlet 38 from import 2 to crank box.Certainly, the design of motor also can be subjected to the influence to the actual requirement of different performance, and this makes between the length very difficult identical.Wish to make and to add the length L of the import of fuel _iGreater than with the air path length L of piston as valve _AiWith the transfer canal length L _s0.6 times of sum, i.e. 0.6 times of (L _Ai+ L _s), but less than 1.4 times of this length, i.e. 1.4 times of (L _Ai+ L _s).Preferably, length L _iGreater than with the air path length L of piston as valve _AiWith the transfer canal length L _s0.8 times of sum, i.e. 0.8 times of (L _Ai+ L _s), but less than 1.2 times of this length, i.e. 1.2 times of (L _Ai+ L _s).

Importantly, recess 10 in the piston and hole 8 and 31 are arranged to when air is changed flow resistance between the hole very little, and like this, regulating can multilated.This adjusting is mainly carried out when two valves 26 and 4 are opened fully.When valve portion is closed, will form multiple different conditions.

In complete throttle operation, promptly in the running of not throttling, the relation between the flow in two systems depends on the cross-section area of each flow passage.Preferably, this cross section is rule as far as possible, but when irregular, cross-section area can be averaged.Therefore, in the simulation of Fig. 2, where this is positioned at corresponding to this partition wall 36.In order to obtain high-performance device, preferably a large amount of air adds by the air supply system that import 2 is arranged.Preferably, has length L _Ai+ L _sThe cross-section area of air flowing access for having length L _iThe 100-200% of cross-section area of import, like this, when throttle operation fully, the amount that enters air is the 50-67% that enters gas gross.Preferably, has length L _Ai+ L _sThe cross-section area of air flowing access be set to have length L _iThe 120-180% of cross-section area of import, like this, when throttle operation fully, the amount that enters air is the 55-64% that enters gas gross.The present invention has a plurality of advantages.Can be installed in the inlet pipeline with a normal standard vaporizer.Then, because the cross-section area of inlet pipeline is divided half, perhaps roughly divided half, therefore can adopt littler standard vaporizer, this will reduce its price, volume and cost.The length of two inlet systems can be determined in manufacture process, can not be subjected to the influence of environment or time, and therefore, air/fuel ratio also can not be subjected to the influence of these factors.By such simple structure, in the speed of certain limit and load, can obtain the may command air/fuel ratio.Compare with common engine, only need to add the throttle valve 4 of simple types, so that regulate the air quantity in the air supply system.This valve cuts out when zero load fully or almost completely, and when throttle valve is opened, it will be opened into increasing gradually.For example, it can be driven by connecting rod, and this connecting rod will transmit desirable motion from throttle valve.

Claims (11)

1. the two-stroke internal-combustion engine of a crank box scavenging (1) wherein, has length L _AiAt least one be that the air passageways of valve is arranged between each transfer port (31,31 ') of air intlet (2) and a plurality of transfer canal (3,3 ') with the piston, these a plurality of transfer canals (3,3 ') have length L _sFrom the transfer port to the crank box, it is characterized in that: air passageways begins to arrange from air intlet (2), this air intlet is equipped with throttle valve (4), this throttle valve is by at least one engine parameter control, air intlet is by at least one connecting tube (6,6 ') stretch at least one attachment hole (8 on engine air casing wall (12), 8 '), this attachment hole is arranged to like this, when piston is positioned at upper dead center, recess (10 in this attachment hole and the piston (13), 10 ') flow passage of form links to each other, this flow passage extends to a plurality of transfer canals (3,3 ') top, and each flow passage in piston is arranged to like this, promptly, with each transfer port (31,31 ') recess (10 in the piston that intersects, 10 ') basic the same long with the intake period of internal-combustion engine during being arranged to make air to supply with, and the length L of the import of adding fuel _iGreater than with the air path length L of piston as valve _AiWith the transfer canal length L _s0.6 times of sum, i.e. 0.6 times of (L _Ai+ L _s), but less than 1.4 times of this length, i.e. 1.4 times of (L _Ai+ L _s).

2. the internal-combustion engine of crank box scavenging according to claim 1 (1) is characterized in that: the length L that adds the import of fuel _iGreater than with the air path length L of piston as valve _AiWith the transfer canal length L _s0.8 times of sum, i.e. 0.8 times of (L _Ai+ L _s), but less than 1.2 times of this length, i.e. 1.2 times of (L _Ai+ L _s).

3. according to the internal-combustion engine (1) of any one described crank box scavenging among the claim 1-2, it is characterized in that: air supply with during greater than 90% of intake period, but less than 110% of intake period.

4. the internal-combustion engine of crank box scavenging according to claim 1 (1) is characterized in that: the recess (10,10 ') in the piston that each transfer port (31,31 ') of described and transfer canal intersects is at greater than the height of corresponding transfer port (31,31 ') 1.5 times of the localized axial height at this place, hole.

5. the internal-combustion engine of crank box scavenging according to claim 1 (1) is characterized in that: the recess (10,10 ') in the piston that each transfer port (31,31 ') of described and transfer canal intersects is at greater than the height of corresponding transfer port (31,31 ') 2 times of the localized axial height at this place, hole.

6. the internal-combustion engine of crank box scavenging according to claim 1 (1) is characterized in that: air intlet (2) has at least two attachment holes (8,8 ') on engine air casing wall (12).

7. the internal-combustion engine of crank box scavenging according to claim 1 (1) is characterized in that: the position of the attachment hole on engine air casing wall (12) (8,8 ') is for like this, and promptly when piston was positioned at its lower dead centre, this piston covered them.

8. the internal-combustion engine of crank box scavenging according to claim 1 (1), it is characterized in that: the position of the attachment hole on engine air casing wall (12) (8,8 ') is for like this, promptly when piston was positioned at its lower dead centre, this piston did not cover them, but the exhaust of cylinder can be passed through air intlet.

9. the internal-combustion engine of crank box scavenging according to claim 1 (1) is characterized in that: the flow passage in the piston (10,10 ') to small part is arranged to the form of at least one recess (10,10 ') on the piston periphery.

10. the internal-combustion engine of crank box scavenging according to claim 1 (1) is characterized in that: have length L _Ai+ L _sThe cross-section area of air flowing access be to have length L _iThe 100-200% of cross-section area of import, like this, when throttle operation fully, the amount that enters air is the 50-67% that enters gas gross.

11. the internal-combustion engine of crank box scavenging according to claim 1 (1) is characterized in that: have length L _Ai+ L _sThe cross-section area of air flowing access be to have length L _iThe 120-180% of cross-section area of import, like this, when throttle operation fully, the amount that enters air is the 55-64% that enters gas gross.

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