DE2126777A1 - Pump nozzle for fuel injection for internal combustion engines - Google Patents

Description

R. 256

March 24, 1971 Ks / Kb

Attachment to

Patent and

Utility model registration

EOBERiT BOSCH GMBH, 7 Stuttgart 1

Pump nozzle for fuel injection for internal combustion engines

The invention "relates to a pump-nozzle for fuel injection for internal combustion engines, in particular diesel engines, the pump cages of which are driven by a servo piston with a larger diameter and which is connected to a pressure source which supplies fuel to both the pump piston and the servo piston, and at a valve slide that is electromagnetically actuated in time with the machine controls the flow of fuel to the servo piston in its first switch position and from the servo piston to a return line in its second switch position and controls the start of the return stroke, in its first switch position it triggers the start of injection and the end of injection and the injection quantity by the rotational position of a mounted on the pump piston oblique control edge determined sindy which cooperates with a control bore in the pump cylinder. -2-

209851/0235

Robert Bosch GmbH E. 256 Ks / Kb

Stuttgart - '"...

In a known pump nozzle of this type (US Pat. No. 2,598,52 (3), the valve slide is mechanical connected to the armature of the electromagnet and is moved by it into its two switching positions. This arrangement has the disadvantage that the inertia forces of the armature and the valve slide are sufficiently fast and accurate Work especially when using in schneilaufenden Diesel engines, make it difficult or even impossible.

Since the magnet to switch the valve slide into its must perform large strokes in both switching positions and build large due to the masses to be moved, is another Another disadvantage is the long response delay of the magnet. and to name its too long switching time.

The invention is based on the object of addressing these disadvantages fix and create a. solenoid valve controlled pump nozzle, that with tendon running diesel engines sufficiently fast and works exactly. . -

This object is achieved according to the invention in that ™ the valve slide from one branched off from the pressure source Part of the fuel used as an auxiliary control fluid. is acted upon and operated by an electromagnetically Directional valve is controllable. . .

A particularly fast working of the pump nozzle is achieved, if the electromagnetically operated directional valve is a pressure-balanced 3/2-way valve with a ball as a valve element is. This advantage is even more pronounced if the fuel is • with the interposition of a small control piston on the Acts valve slide whose maximum cross-section a Is a multiple of the cross section of the control piston.

2098S17023S

Robert Bosch GmbH E. 256 Ks / Kb

Stuttgart ■ -;

A particularly advantageous embodiment of the invention is such that depending on the rotational position of the pump piston the second switching position at the same time as the end of injection of the valve slide is controllable. This leads the servo piston no unnecessary idle stroke and it is called servo fluid less fuel used.

To reduce the injection time at low load and / or at low speeds to extend, · is a further embodiment of the invention such that the pressure of the pressure source dem Fuel supplied to the servo piston can be changed as a function of the speed and / or as a function of the load.

TJm to limit the inflow velocity to the pump working space and to avoid that the servo pressure drops too much, it is advantageous that the pump working space at the end of the return stroke of the servo and pump piston by opening one with a narrow throttle gap having overflow channel the pressure source can be connected.

Two embodiments of the subject invention are shown in the drawing and are described in more detail below. Show it: '

Fig. 1 is a section through the first embodiment the pump nozzle,

Fig. 2 is a side view of the pump nozzle, 'partially cut according to the line II-II in Fig. 1,

Fig. 3 shows a simplified representation of the pump nozzle according to Fig. 1 and 2 additionally with the. essential parts of the entire injection system in the first switch position the valve slide at the beginning, the pressure stroke,

209851/0235

Robert Bosch Gm "bH R. 256 Ks / Kb

Stuttgart ■ '. "■ -

FIG. 4 shows a simplified representation like FIG. 3, however after completion of the pressure stroke (second switching position) "?

FIG. 5 shows a simplified illustration corresponding to FIG. 3, and

Fig. 6 is a simplified representation corresponding to Fig. 4- * however, both for the second embodiment.

L · The pump-nozzle 9, which essentially consists of two subassemblies, has a housing 10 and is screwed to form a coherent unit by means of a clamping sleeve 11 screwed into the housing 10 (FIGS. 1 and 2).

The first assembly is one controlled by a valve slide 12, hydraulically driven pump 13, which has a servo piston 14, a pump piston 15> has a pump cylinder 16 and a pressure valve 17, and in which the valve spool by an electromagnetically operated 3/2-way valve 18 '(see Fig. 2) is controllable, which is briefly described in the following text Solenoid valve 18 is called. The flow rate of the pump is regulated in a known manner by a P adjusting device with a control rod 19 and one.

Pinion sleeve 20. This adjusting device -19.20 can the pump piston 15 are rotated in such a way that in each case a different area of a through an inclined control edge 21 on Pump piston 15 on one side limited control surface 22 interacts with a control bore 23 in the pump cylinder 16. The pump 13 can also be used in a manner known per se and not shown in more detail for reasons of hydraulic force equalization and the unimpeded flow of fuel each have two control edges 21, control surfaces 22 and control bores 23. The fuel supply to the pump working chamber 24 takes place separated from the return of the non-injected fuel via inlet bores 25, which via an inlet line

209851/0236 ~ ⁵ ~

Robert Bosch. GmbH K. 256 Ks / Kb

Stuttgart ·.

are fed and in an annular channel 27 in the. Wall the cylinder bore 28 of the pump cylinder 16 receiving the pump piston 15 open.

In the end position shown in Fig. 1 (OT = top dead center) of the servo piston 14 and the pump piston 15 opens one of an annular groove 29 on the pump piston Ί5 formed supply control edge 31 serving as an inlet ring channel 27 by only one narrow throttle gap "a" so that the fuel is throttled over the annular groove 29 and a longitudinal groove 32 serving as a stop groove can flow into the pump working space 24- at the pump piston 15. This throttled inlet prevents that of a The pressure source described in more detail further below in relation to FIGS. 3 to 6 generated servo pressure Pg in the supply line 26 drops to an impermissibly low value or even collapses. ·

In this TDC position of the piston 14, 15 flows over the throttle gap "a" inflowing fuel through the control bore 23 and a return line 33 pressureless into one Tank (see further below on Fig. 3 to 6) back until the pressure stroke, i.e. when the piston moves downwards the control surface 22 of which closes the control bore 23.

The flushing of the pump working space 24 while the pistons 14, 15 are at TDC, advantageously cools the pump nozzle, and the dreaded formation of vapor bubbles is largely prevented. Possibly occurring bubbles are entrained in the flushing and ^v to the tank. The fuel delivered under pressure during the delivery stroke of the pump piston 15 leaves the pump working chamber 24 via the pressure valve 17.

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209851/0235

Robert Bosch GmbH, R. 256 Ks / Kb

Stuttgart - ■ - ■ '■ "

To that of a valve body 36 »a valve closing member and a valve spring 38 existing pressure valve 17 closes In the axial direction of the pump nozzle 9, the injection nozzle 41, which has a spring housing 4-2 and a Nozzle body 43 has. A nozzle needle 44 is located in the nozzle body guided,. on the within a spring dream 45 of the spring

eVn springs eil he 46
housing 42 / is placed, on which one end 'a closing spring 47 is supported. The closing spring 47 seeks to the. The nozzle needle 44 is to be held in the closed position shown in FIG. 1 and its other end rests on an insert 48, the dimensions of which determine both the spring preload and the needle stroke in a known manner. ■. . .

Line sections 49 and 51 lead from the pressure valve 17 an annular space 52 in which the fuel pressure in known Manner, an annular surface 53 on the nozzle needle 44 is applied.

The spring chamber 45, a Leckölnut 5 ^ in the pump cylinder bore 28, a second spring chamber 55 with the servo piston 14 and a third spring chamber 56 below the valve he donating 12 "are in part a manner not shown with a leak _N ™ fuel hole 57 in connection that returns leaking fuel to the tank. '' ■ - \

The pinion sleeve 20 of the adjustment device 19, 20 is open a cylindrical extension 58 of the pump cylinder 16 rotatable mounted and guides the piston lug 61 of the pump piston 15 via slots 59 · If by longitudinal displacement

. designed as a rack control rack 19, which with Teeth 62 provided pinion sleeve 20 is rotated, granted

• They also rotate the pump piston 15 in the same direction and another area of the control surface 22 operates

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Robert Bosch GMBH . R. 256 Ks / Kb

Stuttgart

during the strokes of the pump piston 15 with the control bore 23 together, i.e. a different fuel delivery rate is injected.

A foot 63 of the pump piston .1.5 is held in a holding plate 64, which is attached to the bottom surface 66 by a spring 65 of the cup-shaped servo piston 14 is pressed. The spring 65 tends to the servo piston in the one shown in FIG To hold position and is supported on the housing 10 via an annular spring support 68, which at the same time an axial displacement the pinion sleeve 20 prevents twisting, however same allowed.

The valve slide 12 is by a spring 69 in his 1 and 2 drawn: position moved or held there when a control pressure chamber 71 is above a small Control piston 72 is depressurized. The control piston 72 is in a housing insert 73 out and has a much smaller cross section than the valve slide 12. That has the advantage that to move the valve slide 12 only uses a small amount of fuel as a control fluid so that short switching times of the solenoid valve 18 are possible are.

Another advantage is that the solenoid valve 18 (FIG. 2) is small, which means that the switching times that can be achieved can also be shortened. _t

As FIG. 2 shows, this is in the upper part of the housing 10 Solenoid valve 18 inserted in a stepped installation opening 74 coaxially to a control line section 75 »is pressure-balanced and operated by an electromagnet 76. Of the

-8th-

209851/0235

Robert Boseil GmbH E. 256 Ks / Kb

Stuttgart - ■

Control line section 75 is shunted to the side an annular channel 77a of a servo feed line 77 O? ig · 1) connected and the solenoid valve 18 controls the through this Line section. 75 incoming servo fluid, in this case Pail the fuel. In his one switching position (see further below on FIG. 4-) it controls the servo fluid via a control line 78 to the control pressure chamber 71 and in its other holding position (see Fig. 2 and 3) away from the control pressure chamber 71 into a return line 79 and thereby blocks the inflow from the line section 75.

The solenoid valve '18 has a valve housing 80 and as a movable Valve member a ball 81, which in the in-Fig. 2 drawn. Position a valve seat 82 in a longitudinal bore 85 blocks and thus the supply of fuel to Control pressure chamber 71 prevented. At the same time, the tax ■ pressure chamber 71 via a second valve seat 84, which is open in the position shown in FIG. 2, with the return line 79 connected. -

The electromagnet .76 has an armature 85, which is in extension the longitudinal bore 83 is guided in the valve housing 80 and with a mandrel 86 under the force of a spring 87 presses the ball 81 onto the valve seat 82 when the electromagnet 76 is in the de-energized state. Around the closing force of the spring 87 at the high servo pressure (e.g. p "= 50 atmospheres) within limits To be able to hold, the solenoid valve 18 is pressure balanced namely in that the pressure prevailing in the control line section 75 via a channel 88 behind the armature. 85 into a space 89 accommodating the spring 87. The areas on the pressurized by the fuel Ball 81 and anchor 85 are the same, so that the opening forces exerted on ball 81 and closing direction

■ -9-

$ 209851/023 ~

Robert Bosch GMBH ' . R. 256 Ks / Kb

Stuttgart

same

if / are. Therefore, only the additional force of the spring 87 acting in the closing direction needs the ball 81 on its Hold seat 82.

The electromagnet 76 has a coil 91 as a control winding. As soon as the coil 91 is energized, for example via an electronic Control unit 115 (indicated further back to FIGS. 3 to 6), the force of the spring 87 is overcome and the armature 8 ^ tightened. The fuel that flows in presses the ball 81 onto the second valve seat 84 and the fuel can flow from the control line section 75 via the longitudinal bore and the control line 78 pass into the control pressure chamber 71. The sections of the valve housing 80 which are under different high pressures are in the stepped installation opening 74 sealed against each other by sealing rings 92,92a, 92b.

The valve slide 12 is loosely connected to the small control piston 72 and only frictionally connected by the spring 69, and has an annular groove 93 * which transfers the fuel to the annular groove 77a in the position shown in FIG. 1 (see also further back to FIG. 3) a connecting line 94 to a servo pressure chamber 95 or, in its other switching position (see FIG. 4), from the servo pressure chamber 95 via the line 94 to an annular chamber 96 (FIG. 1). From the annular space 96, a dashed line in Fig. 2 and drawn stoppered 97 return hole 98 leading to the return line 33 "the i together with the ZuIaufleitung 26 and 57 ⁿ der.Leckkraftstoffbohrung a connecting flange 99 opens.

The return line 79 led away to the outside in FIG. 2 can also lead within the housing 10 to the annular space 96, from where then the flowing back from the control pressure chamber 71

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209851/0235

Robert Bosch GmbH R. 256 Ks / Kb

Stuttgart "

Fuel can flow off via the return bore 98 to the return line 33. The servo-pressure chamber 95 ^s i- "k by a cover 101 (see Fig. 1). Locked, has a stop screw 102, which sets the TDC position of the servo piston 14.

In Fig. 3 there are servo pistons 14, pump pistons 15? "Valve spool 12 and control piston 72 in their upper position also shown in FIG. 1. The electromagnet 76 is current-

w go and the solenoid valve 18 has closed the control line section 75 and relieved the control pressure chamber 71 via the control line 78 ZUT return line 79. The valve slide 12 connects via its annular groove 93 the servo feed line 77 fed by a pressure source 105 via the connection line 94 with the servo pressure chamber 95 The pressure source 105, which is, for example, a gear pump driven by the internal combustion engine 106, generates a pressure control valve 107 regulated constant pressure pg in a pressure line 108 and sucks the fuel in via a filter 109 from a tank 111. The servo pressure pg can also with a corresponding design of the pressure control valve 107 speed

be regulated depending on fc and / or load. The load dependency is, for example, in a known manner by changing the spring preload as a function of the position the power lever (throttle lever) or by turning it of the movable valve members 112 of the pressure valve, which is provided with a known inclined overflow edge (not shown) 107 can be achieved.

In the position shown, some of the fuel flows, as already described for FIG. 1, via the inlet line

209851/0235

Robert Bo sell GmbH 'R. 256 Ks / Kb

Stuttgart.

into the pump working space 24 and from there back into the tank 111 via the return line 33. The return line 79 controlled by the solenoid valve 18 also guides the amount of fuel flowing off from the control pressure chamber 71 back into the tank 111, in the example shown via the return line 33. - ■■ '■'

For a better understanding of the following description of the The mode of operation of the pump nozzle 9 according to the invention is also shown in a simplified representation of the essential assemblies the electrical control device for the solenoid valve 18 is shown. The solenoid valve 18 is activated via lines 114 controlled by an electronic control unit 115, the depending on the speed signal Un one of the internal combustion engine 106 driven speed sensor 116 ,, from the Vegsignal Uv; a displacement encoder 1i7i from the pressure signal Ud one Pressure transmitter 118 and the setpoint signal Us of a known controller 119 determines the switching times of the solenoid valve 18. The position sensor 117 is connected to the control rod 19 and its path signal Uw is dependent on the position of the control rod or the corresponding rotational position of the pump piston 15- The Pressure transmitter 118 is connected to the pressure control valve 107 and generates the pressure signal Ud ^ e.g. as a function of the Position of the valve member 112. The controller 119 can be a known mechanical, hydraulic, electrical or electronic one Be a controller that also moves the control rod 19 via control or connecting elements 120 indicated by dashed lines.

Fig. 4- differs from Fig. 3 by the changed Switching position of the solenoid valve 18 and the other position of both the control piston 72, the valve slide 12 as also the pistons 14 and 15, which are in their bottom dead center position. (UT) stand. The solenoid valve 18, its electromagnet 76

2 0 9851 / 023S

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Robert Böscli GmbH E * 256 Ks / fCb

Stuttgart - "-, ..-

is energized * has the control line section 75 via the Control line 78 connected to control pressure chamber 7Ί * and under the effect of the servo pressure pg, the Control piston 72 moved down and the valve spool 12 moved to the position shown »The valve slide 12 has closed the inlet line 77 and its annular groove 93 connects the servo pressure chamber via the connecting line 94 95 with the return bore 98 and the return line 33, which allows the fuel to flow off to the tank 111 without pressure. 4-The annular channel 27 fed by the feed line 26 is through "the pump piston 15 is closed. The pump working space 24 is via the control bore 23 and return line 33 & it dem Tank 111 connected, i.e. the delivery stroke and also the injection are finished, servo piston 14 and pump piston 1 $ can execute the return stroke under the force of spring 65 until they are again drawn in their in FIGS. 1 and 3 Standing in the OT position.

The second embodiment shown in simplified form according to , Figs. 5 and 6 has the same assemblies and parts like the first example according to FIGS. 3 and 4. The pump-nozzle 9 with the lines 94, 26 and 53 is shown in FIG and 6 drawn in the same position as in FIG. 3 and 4, the position in FIG. 5 that of FIG. 3 "and the Position in Fig. 6 corresponds to that of Fig. 4 *

In Fig. 5, however, in contrast to Fig. 3, the electromagnet 76 is excited, the solenoid valve 18 has the control line section 75 connected via the control line 78 to the control pressure chamber 71 and the control piston 72 and valve slide 12 are in their "lower Sehalt position / but the servo inlet line 77 'and the return line 98' are reversed with respect to the arrangement of the lines 77 and 98 in FIG. 3, is despite the changed switch position of the "." -13-

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Robert Bosch. GmbH ■ E. 256 Ks / Kb

Stuttgart.

Valve slide 12 of the servo pressure chamber 95 via the lines 94, 77 'and 108 connected to the pressure source 105.

In Pig. 6, the electromagnet 76 is de-energized and the solenoid valve 18 blocks and connects the control line section 75 the control pressure chamber 71 with the return line 79 and the tank 111. Control piston 72 and valve slide 12 are in their upper end position and valve slide 12 is in their upper end position blocks the servo feed line 77 'and connects the servo pressure chamber 95 as in FIG. 4, however, via the return bore 98 'with the tank 111. "..

In the switching positions of the solenoid valve 18, the control piston 72 and the valve slide 12 according to FIGS. 3 and 5 the pressure stroke is initiated (start of pressure stroke) and in the position according to FIGS. 4 and 6 the return stroke begins (Start of return stroke), whereby in the first embodiment according to Fig. 5 and 4 the electromagnet 76 during the printing stroke, i. between the start of the pressure stroke and the end of the pressure stroke is de-energized, and in the second embodiment according to FIGS. 5 and 6 it is energized during this stroke, that is, energized.

The second embodiment according to Figures 5 and 6 has the advantage that the duty cycle of the electromagnet is shorter and that the solenoid valve 18 relieves the control pressure chamber 71 in the event of a power failure. This causes the control piston 72 and valve slide 12 by the spring 69 in their pushed upper rest position, and the valve slide 12 connects while the servo pressure chamber 95 ^ t the tank 111, so that the pump piston 15 and servo piston 14 through the Spring 65 brought into its top dead center position (OT) and there being held. Even if the servo pressure fails, the control piston 72 and valve slide 12, as well as the pump piston, return and servo piston 14- back to their original position.

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Robert Bosch GmbH R. 256 Ks / Kb

Stuttgart

In the following, the mode of operation of the pump nozzle 9 is based on 3 to 6 described by a complete working cycle:. . '. -. -

In the first switching position shown in FIGS of the valve slide 12 is, as already described ^ the servo pressure chamber 95 is connected to the pressure source 105, and the servo pressure Pg of e.g. 50 atm acts on the cross-sectional

P surface of the servo piston 14 and moves it together with the Pump piston 1-5 from the position shown opposite to Force of the spring 65 downwards. During this pressure stroke, the fuel supply is first shut down by closing the gap "a" interrupted and then the control bore 25 through the

; Control surface 22 of the pump piston 15 closed, with which the egg injection stroke begins. An injection pressure p-g of, for example, 300 atm. speaking of the transmission ratio between servo piston 14 and pump piston 15 is greater than the servo pressure of e.g. 50 atm. The pump piston 15 pushes the fuel away Pump working space 24 via the pressure valve 17 and the line sections 49,51 to the annular space 52 in the injection nozzle 41 .. The closing spring 4? this injection nozzle 41 is in the present Example preloaded to 150 atmospheric nozzle opening pressure and the fuel under injection pressure pxj takes effect on the annular surface 53 of the nozzle needle 44, lifts it and Fuel is injected into the engine cylinder. -

The injection is ended, as shown in Fig. 4 and 6, when the ^ inclined control edge 21 of the control surface 22 the Control hole 23 opens, because with the opening of the control hole 23, the pump working space 24 becomes the tank via the longitudinal groove 32 in the pump piston 15 and the return line 33

• · -15-

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Robert Bosch GmbH R. 256 Ks / iCb

Stuttgart " ^: " -. '

relieved. i) the injection pressure p-g falls "below the nozzle opening pressure from, the nozzle needle 44 returns to its * closed position and the injection is ended. That Pressure valve 17 ensures in a known manner one each after the valve spring 38 has been pretensioned and the valve member 112 has been formed, the desired static pressure in the line 49 and 51 eier injection nozzle 41. It switches when the injection is completed or very shortly after this point in time the solenoid valve 18 by the control signal of the control unit 115 in. Its position shown in FIGS. 4 and 6 By loading the control pressure chamber 71 (Fig. 4) or The valve slide switches to relieve this space (Fig. 6) 12 in its second switching position shown in FIGS. 4 and 6 around. In this case, the servo pressure chamber 95 is via the Connecting line 94, the annular groove 93 of the valve slide 12, the bore 98.98 'and the return line 33 with the Tank 111 connected. The pressure stroke "H" has now ended, and under the action of the spring 65, pump pistons 15 and 15 return Servo pistons 14 in their drawn in FIGS. 1 to 3 and 5 or in Fig. 4 and 6 indicated by dot-dash lines OT or Rest position back. The pump working space is in this position 24 filled and flushed until by switching the solenoid valve 18 into its shown in FIGS. 2, 3 and 5 Position the next pressure stroke begins.

By additionally switching on a dash-dotted line in FIG. 3 indicated pressure holding valve 121 can, if desired, the pressure remaining in the pump working chamber 24 after the injection process can be maintained at a desired value. ^

209851/0236

Claims (6)

Robert Bosch GmbH R. 256 Ks / Kb Stuttgart Expectations (1.) Pump-nozzle for fuel injection for internal combustion engines, especially diesel engines, whose pump piston is driven by a servo piston with a larger diameter, and the an ψ so a pressure source is connected, which (probably the pump piston and also supplies fuel to the servo piston, and in which one is electromagnetically actuated in time with the machine Valve slide in its first switching position the flow of fuel to the servo piston and, in its second switching position, from the servo piston to a return line and thereby controls the start of the return stroke, whereby it triggers the start of injection in its first stop position; and both the end of injection and the amount of injection ψ ""'are determined by the rotational position of an inclined control edge attached to the pump piston, which cooperates with "a control bore in the pump cylinder, characterized in that the valve slide (12) is branched off from the pressure source (1Q5) part of the fuel serving as auxiliary control fluid is acted upon and can be controlled by an electromagnetically operated directional valve (18). • -17- 209851/0236 Eobert Bosch GmbH R. 256 Ks / Kb Stuttgart 2. Pump-nozzle according to claim 1, characterized in that the solenoid operated directional control valve (18) is a pressure balanced 3/2-way valve with a ball (81) as Valve member is. 3.; <. Pump-nozzle according to one of Claims 1 or 2, characterized characterized that the fuel with the interposition of a small control piston (72) on the valve slide (12) acts whose maximum cross section is a multiple of the cross section of the control piston (72). 4-. Pump-nozzle according to one of claims 1 to 3 »characterized in that depending on the rotational position of the pump piston (15) the second switching position of the valve slide (12) can be controlled at the same time as the end of injection. 5. Pump-nozzle according to one of the preceding claims, daduDch characterized in that the pressure (ps) of the pressure source (105) the fuel supplied to the servo piston (14-) can be changed as a function of the speed and / or as a function of the load. -18- 209851/0236 Robert Bosch GmbH E. 256 Ks / Kb ■ Stuttgart 6. Pump nozzle according to one of the preceding claims, characterized in that the pump working space (24-) at the end of the return stroke of the servo and pump piston (14-, by opening an overflow channel (25.27 ^ 29 * 32) with the pressure source that has a narrow throttle gap (a) (105) is connectable. 209851/0238 Blank page