JPS5821139B2 - Hydraulic torque converter that can also be used for braking - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention can be engaged or disengaged by filling or discharging the working fluid, and can also be used in hydraulic brakes apart from the drive, and which is led from a filling pump. The present invention relates to a hydraulic torque converter that can be connected to a cooling circuit through which a refeed pipe runs, and in which a constant fluid pressure can be maintained in the refeed pipe during operation.

; Known vehicle transmission device (German Publication Specification No. 175)
No. 5916) has two such converters, one for each direction of travel.

The switchover to the braking function is thereby effected by draining the converter previously used for traction while still in operation and filling the other converter at the same time.

This converter thus acts as a hydraulic brake until the vehicle comes to a standstill, after which, if necessary, the vehicle is automatically started in the opposite direction.

A suitably sized pump is provided to ensure that the converter is filled quickly enough.

This pump simultaneously maintains the pressure necessary for optimal converter operation.

The pressure delivered by this pump varies at different flow rates (large flow for filling) when the driving speed is constant.

The use of a centrifugal pump is preferred since X' remains constant for a small flow of refeed during converter operation.

However, the use of evacuation pumps is also known.

Furthermore, if the filling process is taken into account, this type of pump is relatively large; however, there is always a relief valve connected to the compression side, so that the established pressure is limited to a certain value, regardless of the delivery propagation rate. is necessary.

Although the known transmission devices have already proven their effectiveness, there are difficulties in achieving a braking torque curve that is practically satisfactory with respect to the rotational speed of the converter turbine (and with respect to the vehicle speed).

That is, due to its characteristics, hydraulic torque converters produce excessively high braking torques, so that they generally have to be operated with partial filling during braking.

It is known for this purpose to provide the converk with an outlet equipped with a relief valve (pressure limiting valve).

It is kept closed during operation so that braking establishes a certain pressure limit which reduces the pressure spreading into the converter.

However, this results in a braking torque curve that decreases rapidly as negative turbine speed increases (see curve in FIG. 4).

Since in many applications it is desired instead of this to have a braking torque curve that is as flat as possible, attempts have also been made in known manner to vary the pressure limit of the relief valve during braking as a function of the vehicle speed.

However, this method is unsatisfactory as it has been found to be relatively expensive and devices of this type are prone to vibration and failure.

The above-mentioned known converter (German Publication Specification Letter 175
No. 591.6) is equipped with a so-called open cooling circuit; this incorporates a pressure relief valve in the converk outlet so that during braking the working fluid spills from the pressure relief valve into the transmission sump. It looks like this.

From the sump, the working fluid is returned to the converter by a charge pump via a cooling device.

In other known converters, the working fluid is circulated during braking by the pumping action of the converter itself in a closed cooling circuit that includes a cooling device.

During this time, the filling pump only serves to return the leaked fluid.

The closed cooling circuit described above ensures the dissipation of the intensity of braking heat during braking, since the flow velocity in the cooling circuit increases as the turbine speed increases.

Furthermore, the filling pump is designed not to deliver a mixture of liquid and gas that occurs during braking, which can sometimes cause difficulties.

This known converter also has the disadvantage that, although there is no relief valve in the cooling circuit, the hydraulic braking torque produced decreases rather rapidly as the negative turbine speed increases.

It is therefore also well known to provide a regulating valve in order to maintain a constant braking torque when using a closed cooling circuit and a discharge pump (gear pump) as a filling pump.

The regulated pressure transferred from the converk is compared to the rated value and the appropriately regulated refeed stream.

However, this type of regulating valve is expensive and prone to failure.

The object of the invention is that during braking, in cooperation with a closed cooling circuit,
The object is to show a torque converter in which a braking torque curve as close to horizontal as possible is obtained with a device as simple as possible and which overcomes the aforementioned drawbacks.

According to the invention, a torque converter of the type described above is characterized in that the cooling circuit tube has an injector-like constriction at the introduction of the refeed tube.

The invention is based on the knowledge of the following relationship: in known converter configurations with closed cooling circuits, an undesirable relatively rapid decrease in braking torque with increasing turbine speed is clearly caused by the pump during braking. This is caused by the fact that resupply decreases with increasing speed.

This is due, on the one hand, to the establishment of pressure in the region of the converter outlet caused by the increase in velocity that propagates up to the junction of the refeed pipe in the cooling circuit, and on the other hand to the buildup of pressure in the region of the converter outlet caused by the pump in the refeed pipe. This is due to the fact that the increased pressure is kept constant (this is necessary for the reasons mentioned above) so that it can be progressively reduced with respect to the increasing pressure in the cooling circuit.

The resulting reduction in resupply flow results in a progressive reduction in the amount of oil in the converter with a corresponding reduction in braking torque, especially since rising converter pressure also increases the amount of fluid flowing out through the leakage gap. .

The above assumptions on the part of the inventors turned out to be correct.

This is because when the arrangement according to the invention was tested, almost horizontal braking torque curves were obtained in practice, and under certain conditions slightly rising curves.

A distinct venture of the invention is therefore that the resupply delivered by the charge pump during braking is negative with increasing turbine speed (and correspondingly with increasing pressure in the cooling circuit).
must remain constant, or at least not decrease as rapidly as before.

Although it is generally known that in pipelines carrying fluid media other fluid media at low pressure can be pumped in or aspirated by an injector-type constriction, surprisingly the problem discussed above is not solved by this method. Obtained.

Preferably, standard type injectors (jet pumps) are provided in the cooling circuit pipes to which the refeed pipes are connected.

However, it is sufficient to provide the cooling circuit tube with a cross-sectional restriction at the point of introduction of the refeed tube.

It is important that a locally limited pressure drop is produced at the above-mentioned entry points by utilizing the energy of the cooling circuit tubes.

With the invention, tests have shown that a very good braking action of the torque converter is achieved with very little outlay.

Neither a relief valve at the converter outlet nor the above-mentioned regulating valve is required, which means that valves with working elements that are often prone to failure can be largely or completely omitted.

The invention can advantageously be used in the known hydraulic reversing gears mentioned at the outset.

However, the use of the invention in a heavy-duty transmission according to German Published Application No. 2354280 is such that the switching of the hydraulic converter to braking action takes place by engagement of a reversing gear.
This limits the torque converter to what can be temporarily discharged.

The clutch of the reversing gear is formed as a dog clutch,
Shifting during operation is made possible by a synchronizer.

However, the clutch may also be designed as a disc clutch.

As a result of the knowledge gained by the present invention, the refeeding of the cooling circuit during braking is at least constant, so that the above-mentioned problem can be solved at least independently of the pressure rising in the cooling circuit. an additional re-feed line with a second pump of discharge type which is constant, and the first-mentioned re-feed line is provided with a check valve arranged to prevent backflow to the filling pump; It can also be solved by

Said second pump acts purely as a refeeding pump, but has fundamentally different characteristics from the filling pump, which essentially has the original characteristic curve of a draining pump.

Therefore, in order to maintain the generated pressure constant at a value within the standard operating pressure range, there is no pressure limiting valve that should be installed in the pressure pipe of the resupply pump, and a leaf valve is installed at the required place to ensure safety. What is important is that you get it.

Thus, the second solution provides at least a more or less constant refeed flow despite the increase in pressure in the cooling circuit during one braking; It is necessary to provide a check valve to prevent backflow to the pump.

It has already been mentioned that the converter according to the invention is always connected to a cooling circuit during the braking operation, as is already known.

Known converters of this type are always connected to an open cooling circuit during towing, since on the one hand they are filled to capacity and on the other hand they generate less heat.

During the transition from traction to braking, a switch takes place from an open cooling circuit to a closed cooling circuit and vice versa.

A converter according to the invention (or a transmission with at least one converter according to the invention for two directions of travel) can also be operated with such a changeover between an open cooling circuit and a closed cooling circuit.

However, in a further development of the invention, it is proposed that the converter is connected to a closed cooling circuit both during traction and during braking.

In this way, control elements that would otherwise be necessary for determining whether the transmission is in a traction or braking condition can be omitted.

Adjustment of different braking torques at a given rail speed (
i.e., the shift of the braking torque curve) by one of the known methods, e.g. the converter input speed (engine speed), in which both the speed of the pump impeller of the converter and the speed of the charging pump driven by the converter input shaft are varied. can be guaranteed by changing the

However, it is further advantageous to provide the refeed pipe with an adjustable restriction valve in order to directly vary the refeed flow.

Embodiments of the invention are described below in conjunction with the drawings.

The transmission shown in FIG. 1 has two identical hydraulic torque converters 10 and 20.

Each of these has an input drive shaft 11 or 21 with a gear 12 or 22 and a pump impeller 13 or 23, an output drive shaft 14 or 24 with a turbine 15 or 25 and a gear 16 or 26, and furthermore Filling tube 17
or 27. A drain pipe 18 or 28 and finally a symbolic outlet 19 or 29 for the leakage fluid are installed.

Each of the gears 12 or 22 meshes with an input drive gear 9 that is fixed to the input shaft 8.

In this way, the two input drive shafts 11 or 21 with pump impellers 13 or 23 always rotate in the same direction.

The two gear wheels 16 or 26 mesh with each other so that the converter output shaft 14 or 24 with the turbine 15 or 25 always rotates in opposite directions.

One of these two shafts, namely the shaft designated 24, is at the same time the output drive shaft of the transmission.

The filling and draining pipes 17, 27 and 18, 28 have three positions: position V for forward traction or braking when reversing, position 0 for neutral or stationary and position 0 for rearward traction or forward movement. is connected to a valve 30 having a position R for braking.

The directional control valve 30 has junction pipes 31 and 32 for a cooling circuit pipe 33 which leads from the junction pipe 31 to a cooling device 34 and from there back to the junction pipe 32.

An injector 35 is provided in the cooling circuit tube 33.

A refeed line 36, which is connected to the delivery end of a filling pump 37, leads to this injector.

This pump pumps working fluid from the transmission sump 38 and is driven by the input drive shaft 21 via a bevel gear unit and shaft.

The injector is connected to the cooling circuit tube 33 in the direction of flow.
The cooling device 34 may be located in front of the cooling device 34 or, as shown, at the rear.

In position 0 of the directional control valve 30, the drain pipes 18 and 28 are both connected to the oil sump 38 of the transmission, as shown.

Two junction pipes 31 and 32 of cooling circuit pipe 33 are separated from converters 10 and 20, and junction pipe 32 is connected to oil sump 38.

In this way, both converters are drained.

In position V, the junction pipe 32 is connected to the filling pipe of the converter 10 and the discharge pipe 18 is connected to the junction pipe 31.

Converter 10 is thus filled, but converter 2
0 remains ejected.

In position R of the directional control valve 30, the opposite condition occurs.

If necessary, an adjustable restriction valve 41 can be provided in the filling tube 36 (indicated in dash-dotted lines in the drawing).

This allows the flow rate to be varied arbitrarily during braking operations in order to obtain different braking stages.

FIG. 2 shows a part of FIG. 1, namely the cooling circuit lines 31, 33, 32 with the refeed line 36 and the filling pump, but with a gear pump 45 instead of the centrifugal pump.

Similar to the volute pump 37 in FIG. 1, this pump is designed to be able to quickly fill one of the torque converters 10 or 20 and to maintain a certain pressure in the converter (for traction). Its size is selected.

For this purpose, a pressure limiting valve 46 is provided which is connected to the refeed line 36 so as to obtain pump characteristics similar to those characteristic of a volute pump.

Therefore, the introduction part of the resupply pipe 36 into the cooling circuit pipe 33 is as follows:
The injector 35 is configured so that the flow rate does not decrease too rapidly during braking operations (which would cause a significant pressure increase in the cooling circuit).

A restriction valve 41 may also be provided for regulating the refeed;
or a similar arrangement is provided, whereby the relief valve 4
The tension of the spring 47 of 6 can be changed, for example, by a screw 48.

In FIG. 3, a volute pump 37 is again provided as a filling pump, but the arrangement of FIG. 2 with a gear pump and relief valve can also be used instead.

A feature of the arrangement in FIG. 3 is that an additional supply pipe 50 is provided with its own supply pump 51 instead of the injector to resupply the converter with working fluid during braking.

This pump is a gear pump, and the safety valve 52, which does not respond within the standard operating pressure range, is a relief valve (Fig. 2, 46).
has instead of .

A check valve 53 in the refeed line 36 ensures that the working fluid delivered by the gear pump 51 is supplied to the oil via the volute pump 37 or, if the filling pump 37 is configured as a gear pump, via the above-mentioned pressure relief valve. Backflow into reservoir 38 is prevented; otherwise the desired effect will not be achieved.

The gear pump 51, together with the centrifugal pump 37 as shown,
It can be driven by an input drive shaft via shaft 40.

However, it may also be driven by the output drive shaft 24 (see FIG. 1) or by a drive independent of the converters 10 and 20 (for example by an electric motor).

In the graph of FIG. 4, the torque M2 of the output drive shaft 24
is written regarding the speed n2 of the output shaft.

The right region of the graph labeled T relates to traction, and the left region B relates to braking.

Curve a shows the torque M2 during traction with a charged converter on the one hand and the torque M2 in the highest braking phase during braking on the other hand.

For comparison, the dashed line shows the braking torque curve of the known converter at the highest braking stage.

Curves aI J a2 and a3 are, for example, the limit valve 41 (first
FIG. 2 is a braking torque curve in a lower braking stage obtained by adjusting the FIG.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a reversing transmission with two hydraulic torque converters according to the invention; FIGS.
FIG. 4 is a diagram showing a modification of the device shown in FIG. 4, and FIG. 4 is a graph of a torque curve. 8...Input shaft, 9...Input, drive gear, 10.20
... Hydraulic torque converter, 11.21 ... Input drive shaft, 12, 22, 16, 26 ... Gear, 13.2
3... Pump impeller, 14, 24... Output drive shaft,
15°25...turbine, 17.27...filling pipe,
18゜28...Discharge pipe, 19.29...Discharge port, 3
0...Directional control valve, 31.32...Joint pipe, 33.
... Cooling circuit pipe, 34 ... Cooling device, 35 ... Injector, 36 ... Re-supply pipe, 37 ... Filling pump, 38 ... Oil reservoir of transmission device, 39 ... Bevel gear Unit, 40... Axis, 41... Adjustable restriction valve, 4
5.51... Gear pump, 46... Pressure limiting valve, 4
7... Spring, 48... Screw, 50... Supply pipe, 5
2...Safety valve, 53...Check valve.

Claims (1)

[Claims] 1. A resupply pipe that can be engaged or disengaged by filling or discharging working fluid, can be used for hydraulic brakes in addition to driving, and is led from a filling pump. In the hydraulic torque converter, the hydraulic torque converter can be connected to a cooling circuit through which the resupply pipe is connected, and a nearly constant fluid pressure can be maintained in the resupply pipe during operation, and the resupply pipe has an injector-shaped constriction at the introduction part thereof. A hydraulic torque converter featuring: 2. Claim 1, characterized in that an additional refeed pipe with a discharge pump is provided, and said refeed pipe is provided with a backflow valve to prevent backflow to the filling pump. Hydraulic torque converter as described. 3 Converter discharge pipe 18. 3. The hydraulic torque converter according to claim 1, wherein the cooling circuit pipe and the converter filling pipe 17 form a closed cooling circuit both during driving and during braking. 4. Hydraulic torque converter according to claim 1 or 3, characterized in that an adjustable limit valve is arranged in the resupply pipe. 5. Hydraulic according to any one of claims 1 to 4, characterized in that it is used in a purely hydraulic reversing transmission, in which at least one converter is arranged for each direction of travel. torque converter.