WO2007085344A1

WO2007085344A1 - Free-piston engine

Info

Publication number: WO2007085344A1
Application number: PCT/EP2007/000144
Authority: WO
Inventors: Jörg Dantlgraber; Rudolf SCHÄFFER
Original assignee: Robert Bosch Gmbh
Priority date: 2006-01-26
Filing date: 2007-01-10
Publication date: 2007-08-02
Also published as: DE102006003826A1; EP1982056A1

Abstract

Disclosed is a free-piston engine having a housing (2) which is mounted or suspended so as to be moveable relative to a frame (18), wherein said movement of the housing relative to the frame can be utilized for driving auxiliary functions of the free-piston engines such as for example for the circulation of coolant in a coolant circuit or for driving a low-pressure pump or an injection pump.

Description

Description Free piston machine

The invention relates to a free-piston machine with a coolant circuit, an associated low-pressure pump and / or an associated injection pump.

A free-piston engine is in principle a combustion engine operating according to the 2-stroke method, in which, instead of a crank drive, a hydraulic circuit with a piston pump as the drive train is connected downstream. For this purpose, the engine piston is connected to a hydraulic cylinder, via which the translational energy generated during an engine operating cycle is fed directly to the hydraulic working fluid without the classical detour via the rotational movement of a crank mechanism. The downstream, storable hydraulic circuit is designed such that it receives the delivered work, cached and supplies depending on power requirements of a hydraulic output unit.

Due to the high temperatures in the combustion cylinder, there is a need for cooling in the free-piston engine as well as in other combustion engines operating according to the 2-stroke process. The document EP 1282766 D1 shows a free-piston machine with a combustion cylinder by providing channels through which coolant can flow. This document, however, are no further details on the design of the Kühlkreislaüfes particular for promoting the coolant removed.

In the document US 6,314,924 a hydraulic motor is described, the output shaft is suitable for driving a fan wheel and a water pump. For example, centrifugal pumps are used as coolant pumps in the prior art. Coolant pumps must be specially adapted for the specific requirements of free-piston machines, so that the manufacturing cost of the ancillary units of the free-piston engine performing coolant pumps are relatively high. The mass of ancillary equipment also adversely affects the overall mass of the mobile implement when using free piston machines for mobile work equipment.

The object of the present invention is to provide a free-piston engine with improved drive for auxiliary functions of the free-piston engine.

This object is achieved by the free-piston engine according to claim 1.

The free-piston machine according to the invention has a housing that is movably mounted or suspended relative to a frame, so that the movement of the housing relative to the frame for driving the auxiliary functions of the free-piston engine such. B. is usable for the circulation of a coolant in the combustion cylinder. In this way, the relative movement between the engine piston and combustion cylinder can be used for additional functions in which ancillary units were previously necessary.

Preferably, the free-piston engine has a coolant space for cooling the combustion cylinder, wherein this has a check valve or the like, is made possible by a relative movement of the housing to the frame conveying the coolant in a direction in the coolant space. This is due to the relative movement between the engine piston and combustion cylinder The coolant circuit supports, so that no externally controlled valves or units are necessary.

Preferably, the check valve is provided at the coolant inlet, so that a backflow of heated coolant from the combustion cylinder is prevented against the flow direction of the cooling circuit.

It is preferred that the opening and closing of the check valve takes place in the direction of movement of the engine piston, so that the relative movement between the engine piston and combustion cylinder can be used to open the check valve.

According to an advantageous embodiment of the present invention, a piston is supported on the frame, which limits the housing a piston chamber of a pump, such as a low-pressure pump or an injection pump, can be executed via the additional secondary functions.

To avoid vibrations, an end portion of at least one piston rod provided on the piston is supported via a movable bearing on a frame.

In one embodiment, an annular piston is penetrated by a piston rod of the engine piston, due to its relative movement to the housing pressure medium can be sucked and conveyed to a space bounded by the hydraulic piston space. Due to the possibility of direct intake from the tank, the production price of the free-piston engine is lower and the efficiency of the free-piston engine is improved. The annular piston is preferably supported on a frame via a holder. In this way, an approximate determination of the relative position of the free-piston engine with respect to the frame.

Preferably, the annular piston is supported on a movable bearing and the annular piston acts as an inert mass, so that vibrations due to reaction forces can be reduced or eliminated.

According to one embodiment of the invention, a magnetic element is supported on the frame, by the relative movement with respect to the housing of the free-piston engine electrical energy can be generated. As a result, the housing movement can be used with good efficiency for energy production.

Furthermore, it is preferred that the free-piston machine according to the invention comprises a spring arrangement or a suspension, by which it is preventable that the housing moves out of its zero position, which ensures a stable arrangement of the free-piston machine, in particular for mobile implements.

Developments according to the invention are the subject of claims.

Hereinafter, the present invention will be described with reference to schematic drawings. Show it,:

1 shows a free piston machine according to the invention according to the first embodiment during the compression stroke, 2 shows a sectional view through the combustion cylinder of FIG. 1 with illustrated overflow channel, FIG.

3 shows a free-piston machine according to the invention according to the first embodiment during the combustion stroke,

4 shows a free-piston machine according to the invention according to the second embodiment,

Fig. 5 shows a modification of the free-piston engine according to the second embodiment

6 shows a free-piston machine according to the invention according to the third embodiment,

Fig. 7 shows a modification of the free-piston engine according to the third embodiment, and

Fig. 8 is a free piston engine according to a fourth embodiment.

Figs. 1 and 2 show a greatly simplified, schematic representation of a free-piston machine 1 according to the invention according to the first embodiment. This has a motor housing 2, by which at least one combustion cylinder 3 and a hydraulic cylinder 7 are limited. The representation of the combustion cylinder 3 in Figs. 1 and 2 differs only in the position of the section through the combustion cylinder.

In a cylinder bore 8 of the combustion cylinder 3, an engine piston 10 is guided, via which the cylinder bore 8 is divided into a combustion chamber 12 and an inlet space 14. In the illustrated queue 1, the engine piston is at its inner dead center (IT), wherein an outlet valve 6a of an outlet channel 6 shown in FIG. 2 is opened, so that combustion gases can flow out of the combustion chamber 12. The supply of fresh gas via an inlet channel 4 shown in Fig. 2, which opens into the inlet chamber 14. The inlet space 14 and the combustion space 12 are connected by means of an overflow channel 5.

The injection of the fuel into the combustion space 12 ^' takes place via an injection valve 16 in the cylinder head of the combustion cylinder 3.

To cool the free-piston engine 1, a hollow-cylinder-like coolant chamber 40 is formed in the circumferential wall of the combustion cylinder 7, or its end sections are formed on the side of the end face of the engine piston 10 in such a way that it adjoins the combustion chamber 12 Injector 16 surrounds. Said end portion of the coolant chamber 40 further includes, in the axial direction of the engine piston 10, a coolant inlet closed by a check valve 42. A coolant outlet 44 is located in the peripheral wall in a section of the combustion cylinder which is opposite to the injection valve 16 in the axial direction of the engine piston 10. In this way, a flow through the coolant chamber 40 from the check valve 42 to the coolant outlet 44 in the axial direction of the combustion cylinder is possible, whereby heat can be dissipated effectively.

The combustion cylinder 3 is movably arranged on a frame 18 via a bearing 46 indicated schematically in FIG. In particular for mobile work devices to prevent movement of the motor housing 2 from the Nullläge out, the combustion cylinder is supported by springs or a suspension and this is reset by the spring or the suspension in a movement out of Nullläge out by the spring or suspension again.

The engine piston 10 carries a piston rod 20 whose diameter is substantially smaller than that of the engine piston 10. This piston rod 20 is immersed in an axial bore 19 of the hydraulic cylinder 7. The piston rod 20 has, opposite to the side of the engine piston 10, a hydraulic piston 21. By the hydraulic piston 21, the axial bore 19 is divided into a limited by a piston surface 22 on the piston piston 21 cylinder chamber 23 and a limited by an annular surface 24 on the hydraulic piston 21 and the piston rod 20 annular space 25. The annular space 25 is connectable to the cylinder space 23 via a non-return valve 29 which is formed in the hydraulic piston 21 and opens toward the cylinder space 23. In the annular space 25 pressure medium from a low-pressure accumulator 27 and a pressure line 28 from the consumer passes through a check valve 26 which opens to the annular space 24.

With the cylinder chamber 23 is a working port of a pilot-controlled logic element 37 in pressure medium connection, the other working port is connected to a high-pressure accumulator 32 and a pressure line 34 to the consumer. At the control terminal X of the logic element 37 is a switching valve 36 with two switch positions and three connections. In the switching position a of the switching valve 36, a pressure medium connection between the control terminal X of the logic element 37 and a tank 30 is made, so that the spring chamber 37a is relieved in the logic element 37 to the tank 30. In one ner basic position b of the change-over valve 36, a pressure medium connection between the high-pressure accumulator 32 and the pressure line 34 is provided to the consumer with the control terminal X of the logic element 37, so that the pressure medium connection between the pressure line 34 and the cylinder chamber 23 is interrupted. Furthermore, the cylinder space 23 can be connected to the tank 30 via a relief valve 38, which is provided as a 2-way valve with an open and a closed switching position.

The function of the free piston machine according to the invention will be described below.

At the beginning of the compression stroke is the hydraulic piston 21 in Fig. 1 in its left position, the relief valve 38 is closed and the pressure in the high-pressure accumulator 32 via the set in its home position b switching valve 36 at the control terminal X of the logic element 37, so that there is no pressure medium connection between the high-pressure accumulator 32 and the cylinder chamber 23.

To initiate the compression stroke, the switching valve 36 is brought into its switching position a, so that the control terminal X of the logic element 37 is relieved to the tank 30 back. Due to the opening of the logic element 37 pressure medium from the high-pressure accumulator 32 passes into the cylinder chamber 23 and causes the pressure building up, which acts on the piston surface 22 of the hydraulic piston 21, a movement of the hydraulic piston 21 and thus of the engine piston 10 in Fig. 1 to the right, that is to the inner dead center of the engine piston 10 back. The pressure medium present in the annular space 25 passes via the opening check valve 29 into the cylinder space 23. Due to the movement of the engine piston 10 toward the inner dead center, due to the movable mounting of the motor housing 2 relative to the frame 18, the motor housing 2 opposite to the movement of the engine piston 10, that is in Fig. 1 to the left, accelerated. Due to the higher mass of the motor housing 2, the deflection of the motor housing 2 in comparison to the deflection of the engine piston 10 is substantially lower. As a result of this housing acceleration during the compression stroke, the cooling water in the coolant chamber 40 is set in motion so that coolant can flow in the direction of the coolant outlet 44.

Fuel is injected via the injection valve 16 and ignited upon reaching the desired compression in the combustion chamber 12, so that the engine piston 10 starts with its shown in Fig. 3 movement toward the outer dead center, that is in Fig. 3 to the left. In this case, the relief valve 38 is in the closed position and the switching valve 36 in switching position a, so that there is a pressure medium connection from the cylinder chamber 23 to the high-pressure accumulator 32 and the pressure line 34 to the consumer.

The movement of the engine piston 10 to the outer dead point causes a movement of the hydraulic piston 21 in Fig. 3 to the left, so that via the piston surface 22, the pressure in the cylinder chamber 23 is increased and pressure fluid flows to the high-pressure accumulator 32 and via the pressure line 34 to the consumer. In the increasing annular space 25 occurs pressure medium via the check valve 26 from both the low-pressure accumulator 27 and from the pressure line 28 from the consumer.

The rapid movement of the engine piston 10 in Fig. 3 to the left causes entrainment of the coolant in the cooling middle space 40 in such a manner that the check valve 42 opens and further coolant enters the coolant chamber 40. Further, coolant flows out of the coolant outlet 44. In this way, without the use of an additional pump Kühlmittelumfüh- tion alone due to the relative movement between the motor housing 2 and engine piston 10 is possible.

In order to bring the hydraulic piston 21 in its initial position for the compression stroke, the relief valve 38 is brought into its open position, so that in the cylinder chamber remaining pressure fluid can flow to the tank 30.

With the free piston engine according to the first embodiment results in the advantageous effect that only when the free piston engine is running, and coolant is circulated, so that an efficient operation is possible.

According to a development of the invention, an adjustable throttle valve can be provided in the coolant circuit, by which the flow rate in the coolant circuit can be reduced in the desired manner.

In order to avoid with mobile implements that the free piston machine moves out of its zero position, a support by springs or a suspension of the free-piston engine is possible.

According to the second, third and fourth embodiment of the invention shown in FIGS. 4 and 5 or 6 and 7 or 8, the relative movement between the motor housing 2 and the frame 18 can also be used to drive further auxiliary functions. In particular, a piston may be provided on the frame or in connection therewith. be seen that defines with the motor housing 2, a low-pressure pump or an injection pump. Alternatively, a cylinder housing may be attached to the frame and a piston connected to the motor housing 2 of the free-piston pump.

In this case, it is preferable that the motor housing 2 is supported by springs. In the second and third embodiments, the relative movement of the motor housing 2 and frame 18 can be used to drive an injection pump or a low-pressure pump in addition or alternatively to drive the coolant in the coolant circuit, which will be explained below.

In a free-piston engine according to the second embodiment shown in Fig. 4, which corresponds to the following differences of the free piston engine of the first embodiment, is provided radially outside the combustion cylinder 3 on the motor housing 2, a synchronous cylinder 60 with a piston 62, on which a through a left Piston rod 64 limited, left annular end face 68 and a limited by a right piston rod 66 right annular end face 72 are provided. By the left annular end surface 68, a left annulus 70 and the right annular end face 72, a right annulus 74 is limited. The left piston rod 64 and the right piston rod 66 are fixed to a frame 18 on which the motor housing 2 is supported via bearings 46.

The left-hand annular space 70 is connected via a prefeed line 76 and a left-hand pressure line 80 to a prefeed pump, not shown in FIG. 4, for fuel in pressure medium connection. In the feed line 76 to the left annular space 70 toward opening, designed as a check valve, left suction valve 78 is provided. From the feed line 76 branches upstream with respect to the left suction valve 78 a leading to the right pressure chamber 74, right pressure line 84 from. In the right-hand pressure line 84, a right-hand suction valve 82, which opens to the right-hand pressure chamber 74, is provided.

Downstream of the left suction valve 78 branches from the left pressure line 80 from a connected to the injection valve fuel line 80 from. In this fuel line 80, an opening to the injector left pressure valve 86 is provided. Further, in this fuel line 80, downstream of the left-side pressure valve 86, a branch line 89 branching from the right-hand pressure line 84 downstream of the right-side suction valve 82 opens, in which a right-hand pressure valve 88 opening to the injection valve is arranged. Downstream of the left and right pressure valves 86, 88 is connected to the fuel line a surge tank 92, is stored in the fuel and is injected from the depending on the operation of the injector 16 in the combustion chamber of the free-piston engine.

Hereinafter, the function of the second embodiment will be explained as an injection pump. During the compression stroke shown in Fig. 1, the motor housing 2 and with this the Gleichgangzylinder 60 in Fig. 4 is shifted to the left. Since the piston 62 is firmly clamped on the frame 18 via the left and right piston rods 64, 66, the displacement of the housing of the synchronous cylinder 60 causes an increase in the volume of the left annulus 70 and a decrease in the volume of the right annulus 74. Due to the decreasing pressure in the left annulus 70 opens the left suction valve 78 and fuel flows from the prefeed pump via the feed line 76 and the left suction valve 78 in the left annulus 70. By reducing the volume of the right Annulus 74 causes the increasing pressure in this opening of the right pressure valve 88 so that fuel with increased pressure from the right annulus 74, the right pressure valve 88 and the fuel line 90 reaches the surge tank 92, of which the fuel upon opening of the injector is injected into the combustion chamber.

During the combustion stroke shown in Fig. 3, the motor housing 2 moves in Fig. 4 to the right, so that the volume of the left annulus 70 decreases and increases the volume of the right annulus 74. Due to the pressure increase in the left annular space 70 of the fuel sucked in the previous compression stroke passes through the left pressure valve 86 in the fuel line 90 and from there into the surge tank 92. At the same time fuel via the feed line 76, the right pressure line 84 and the right suction valve 82 in the sucked right annular space 74.

With the synchronous cylinder of the second embodiment, a fuel delivery and fuel pressurization is thus possible both during the compression stroke and during the combustion stroke. The housing movement of the free-piston engine is used to drive the injection pump, so that it is possible to generate a high-pressure fuel with minimal effort and good efficiency.

Fig. 5 shows a modification of the second embodiment with respect to the use of the housing movement for secondary functions. In the second embodiment shown in Fig. 4, the left and right piston rods 64, 66 are rigidly supported on the frame 18. In the modification shown in FIG. 5, the left piston rod 64 is connected to the frame 18 via a left movable bearing 94, whereas rend the right piston rod 66 is connected via a right floating bearing 96 with the frame 18. In addition, the piston 62 is defined as an inert mass, so that vibrations due to reaction forces on the fuel delivery piston can be reduced.

Fig. 6 shows a free-piston engine according to the third embodiment, in which the movement of the motor housing of the free-piston engine for driving a low-pressure pump for the pressure medium to the annular space 25 is used on the hydraulic piston 21.

In contrast to the first and second exemplary embodiment, in the left section of the combustion cylinder 3, a prefeed piston 112 divides the inlet space 14 from FIG. 1 into an inlet space 114 adjacent to the engine piston 10 and a left piston space 115 adjacent to the hydraulic cylinder. The left piston chamber 115 is delimited by an annular end face 116 formed on the prefeed piston 112.

The prefeed piston 112 designed as an annular piston is penetrated by the piston rod 20 of the engine piston 10, is slidably mounted on the piston rod 20 and is secured to the frame 18 via a housing 108 extending essentially radially to the combustion cylinder 3. The inlet space 114 is sealed with a seal 110 between the bracket 108 and the motor housing 102.

In contrast to the radial inlet to the annular space 25 on the hydraulic piston 21 in the first embodiment, a suction line 118 is formed in the motor housing 102 in the third embodiment shown in Fig. 6. The suction line 118 connects a tank 30 with the left piston chamber 115 via an opening to the left piston chamber 115. the check valve 120. The left piston chamber 115 is connected via a pressure line 122 to the annular space 25 on the hydraulic piston 21 via a check valve 124 opening toward the annular space 25.

In the compression stroke shown in Fig. 6, the motor housing 102 moves to the left, so that the fixed feed piston 112 moves in the motor housing 102 in Fig. 6 to the right. Due to the increasing volume of the left piston chamber 115 pressure fluid from the tank 30 via the suction line 118 and the open check valve 120 is sucked into the left piston chamber 115.

In the subsequent combustion stroke moves due to the movement of the motor housing 102 to the right of the feed piston 112 with respect to the motor housing 102 in Fig. 6 to the left, so that the left piston chamber 115 decreases. The pressure medium with increased pressure flows via the pressure line 122 and the opened check valve 124 into the annular space 25.

By providing the prefeed piston 112 in the combustion cylinder 3, a low-pressure pump is thus provided in the free-piston engine with which the annular space 25 in the hydraulic cylinder 7 can be filled without cavitation during suction. On a separate, active low pressure supply, including with hydraulic pump and - motor, pressure accumulator can be dispensed with.

Fig. 7 shows a modification of the third embodiment, in which instead of the fixed bearing 46 for supporting the motor housing 102, a floating bearing 148 with a support 140, with which the holder 108 is connected to the Vorförderkolben 112, the motor housing 102 holds. Furthermore, the prefeed piston 132 has an annular additional mass 134, which is designed so that it can dip into an annular engine piston interior 136 of the engine piston 10 when it is at its outer dead center.

As a result of the annular additional mass 134, the delivery piston 132 acts as an inert mass, so that a relative movement between the motor housing 102 and the engine piston 10, despite the existing floating bearing 138, enables an increase in volume / volume reduction of the left piston chamber 115 and thus the function of the low-pressure pump. Due to the floating bearing 138 vibrations due to reaction forces are reduced.

Fig. 8 shows a free-piston engine according to the fourth embodiment, which differs from the free-piston engine of the first embodiment in that the motor housing 2, a solenoid coil 150 is provided in the recess of a supported on the frame via a left mounting rod 154 and a right mounting rod 156 armature 152 is slidably received. Due to the relative movement between the motor housing 2 and magnet armature 152, an oscillating voltage is induced in the magnet coil 150. This oscillating voltage is rectified by a rectifier according to the requirements of the secondary functions.

The fourth embodiment is not limited to the arrangement of a magnetic armature 152 in the magnetic coil 150, but the armature may be connected in a modification with the motor housing 2 while the coil is fixed to the frame 18. The magnet armature can have a permanent magnet or be provided with a current-carrying winding. The present invention is not limited to any of the embodiments, but may be any combination between driving the Kühlmittelkreis- run of the first embodiment, injection pump of the second embodiment, low-pressure pump of the third embodiment and / or solenoid coil of the fourth embodiment of a free-piston engine be provided according to the present invention.

Disclosed is thus a free-piston engine with a housing which is movably mounted or suspended relative to a frame, said movement of housing relative to the frame for driving auxiliary functions of free-piston engines such. B. for the transfer of coolant in a coolant circuit or to drive a low-pressure pump or an injection pump is available.

Claims

claims

A free piston machine (1) comprising a housing (2) movably mounted or suspended relative to a frame (18) such that movement of the housing (2) relative to the frame (18) drives auxiliary functions of the free piston engine is usable.

2. The free-piston machine according to claim 1, having a coolant chamber (40) for cooling the combustion cylinder (3), the coolant chamber (40) having a check valve (42) arranged in such a way that, due to the relative movement of the housing (40), 2) to the frame (18) a conveying of coolant in the coolant space (40) in one direction is made possible.

3. Free-piston machine according to claim 2, wherein the check valve (42) is provided at the coolant inlet.

4. Free-piston machine according to one of claims 2 and 3, wherein the opening and closing of the check valve (42) in the direction of movement of the engine piston (10).

5. Free-piston machine according to one of the preceding claims, wherein on the frame (18) a piston (62) is supported, which defines a piston chamber (70, 74) of a low-pressure pump or an injection pump with the housing (2).

6. Free-piston machine according to claim 5, wherein an end portion of at least one of the piston (62) arranged piston rod (64, 66) via a movable bearing (94, 96) on a frame (18) is supported.

7. Free-piston machine according to one of the preceding claims with an annular piston (112) which is penetrated by a piston rod of an engine piston (10), and due to its relative movement to the housing (2) pressure medium sucked and to a by the hydraulic piston (21) limited space ( 25) is eligible.

8. Free-piston machine according to claim 7 with a holder (108) for the annular piston (112) which is supported on a frame (18).

9. free piston engine according to claim 7 with a holder (108) for the annular piston (112), to a floating bearing

(138) is supported and the annular piston is designed in such a way that it acts as a sluggish mass.

10. Free-piston machine according to one of claims 1 to 4, wherein on the frame (18) a magnetic element (152) is supported, via whose relative movement to the housing (2) electrical energy can be generated.

11. Free-piston machine according to one of the preceding claims with a spring or a suspension, can be prevented by the fact that the housing moves out of a zero position.