WO2022008412A1

WO2022008412A1 - Hydrostatic auxiliary drive

Info

Publication number: WO2022008412A1
Application number: PCT/EP2021/068460
Authority: WO
Inventors: Tobias Wille; Alex GLAVAK
Original assignee: Robert Bosch Gmbh
Priority date: 2020-07-09
Filing date: 2021-07-05
Publication date: 2022-01-13
Also published as: DE102020208594B4; EP4179234A1; DE102020208594A1

Abstract

The invention relates to a hydrostatic auxiliary drive for assisting a main drive, a variable displacement pump of the auxiliary drive being designed and controlled such that it is possible to control pressure and thus torque independently of the slip on the main drive.

Description

Hydrostatic auxiliary drive

The invention relates to a hydrostatic auxiliary drive according to the preamble of patent claim 1.

A truck is disclosed on the Internet at https://www.mantruckandbus.com/de/unternehmen/glossar/man-hydrodrive.html, which has rear wheels driven by a main drive and front wheels that can be driven by a hydrostatic auxiliary drive. The hydrostatic auxiliary drive can be switched on by the driver as required. Depending on the boundary conditions, in particular the driving speed, the auxiliary drive only transmits torque to the front wheels when the rear wheels are slipping. For this purpose, the additional drive for each of the two front wheels has a hydrostatic radial piston motor, which is supplied by a hydrostatic pump via a closed circuit.

The object of the present invention is to provide a hydrostatic auxiliary drive which can be driven together with a main drive by a common drive machine and which can be controlled independently of the slip on the main drive.

This problem is solved by a hydrostatic auxiliary drive with the combination of features of claim 1.

Further advantageous developments of the invention are described in the dependent claims.

The claimed hydrostatic auxiliary drive has a variable displacement pump which is connected to a hydrostatic motor arrangement via two working lines in a closed circuit. The variable displacement pump has a pressure control valve, with a control pressure surface of the pressure control valve acting in the direction of reducing the working pressure of the variable displacement pump. The control pressure surface can be connected or is connected to a feed circuit or a feed pressure supply via an electrically actuated flow control valve. With that you can Vary the start of control and choose the pressure limitation freely. In this way, the additional drive according to the invention can be controlled independently of the slip on the main drive, which is driven by a drive machine together with the variable displacement pump.

In a particularly preferred application of the additional drive according to the invention, the drive machine is a diesel engine to which the main drive on the one hand and also the additional drive according to the invention are coupled via a main transmission. The prime mover is coupled to rear wheels of a vehicle, such as a truck, while the accessory drive motor assembly is coupled to front wheels of the vehicle.

When driving in difficult terrain, this has a positive effect on the steering behavior and the directional stability of the vehicle. This enables, for example, a power start when moving off, i.e. additional torque on the front wheels. By specifying the pressure, the variable displacement pump automatically regulates to the necessary delivery volume, which means that it is no longer necessary to adjust the overall hydraulic-mechanical transmission ratio.

The pressure control valve is preferably a 3/2-way valve, which connects an actuating pressure chamber of an actuating cylinder of the variable displacement pump, which acts in the direction of reducing the working pressure, either via a first connection to the working line carrying the working pressure, or relieves this actuating pressure chamber via a second connection to a pressure medium sink.

If a switching valve designed as a 4/2-way valve is provided, which is connected on the one hand to the two connections of the 3/2-way valve and on the other hand to the working line carrying the working pressure and the pressure medium sink, then the additional drive can be switched between overrun mode and traction mode and be controlled independently of the slip at the main drive in both operating modes.

It is particularly preferred if the switchover valve can be switched automatically when the auxiliary drive changes between overrun mode and traction mode. For this purpose, according to an option 1, the changeover valve can be switched via an electric actuator. Or according to option 2, the changeover valve can be switched via a pilot valve.

In order to be able to control the auxiliary drive in option 2 in overrun and traction mode when driving forwards and backwards independently of the slip on the main drive, it is particularly preferred if the pilot control valve is designed as a 3/2-way valve which in one way - e.g. by a spring - prestressed position to the working pressure of the first working line transmits a control pressure area of the changeover valve, and which, in a position switched by an electric actuator, transmits the working pressure of the second working line to the control pressure area of the changeover valve.

In a preferred embodiment of the additional drive according to the invention, the feed pressure supply has a feed pump, a feed valve, a main feed line and a feed branch line. The feed pump is connected to the main feed line via the feed valve. The main feed line can be connected to the secondary feed line via a non-return valve which is preloaded, preferably by a spring, with the opening direction of the non-return valve being directed from the main feed line to the secondary feed line. This means that cross-flushing as described below is possible when the two working lines are depressurized. For example, the spring has an equivalent of 3 bar.

The flow control valve is connected to the food bypass.

When the engine assembly includes at least one radial piston engine having a housing, a cam ring, and a plurality of pistons, a cross-flush valve may be connected to the feed main line, with the housing having a first tank port connected to the cross-flush valve. Cross-flushing of the interior space is realized when an interior space of the housing is supplied with supply pressure medium via the cross-flush valve and via the first tank connection. In this way, the pistons of the radial piston motor in question can be lifted off the cam ring, that is to say they can be pulled back radially inwards. This minimizes the heat loss when the additional drive is deactivated. Furthermore, the remaining heat loss is transported away in this way.

The housing of the at least one radial piston motor can have a second tank connection, with the cross-flushing being realized from the first tank connection through the interior space to the second tank connection.

The interior of the housing of the at least one radial piston motor can be connected to the two working lines via a respective check valve, with an opening direction of the two check valves being directed from the interior to the respective working line, with the cross-flushing being realized from the first tank connection via one of the check valves to the working line connected thereto . Preferably, the two check valves are biased by a respective spring. For example, the spring has an equivalent of 0.5 bar. Cross-flushing should always be ensured. In particular, cross-flushing should be ensured even if the control signal of the feed valve is interrupted.

For this purpose, the feed valve connects the feed pump to the main feed line in an open position prestressed, e.g. by a spring, whereby it shuts off the feed pump from the main feed line in a blocking position actuated by an actuator, e.g. electromagnetic. In conjunction with pressure sensors in the working lines, it is possible to actively close the feed valve with its actuator in the event of a line break in a working line. This avoids the quantity of the feed pump escaping at the point of the line break in this case. On the other hand, it is possible to maintain the supply of the main feed line with feed pressure medium and thus also the cross-flushing even if the control signal of the feed valve is interrupted.

In a preferred embodiment, the feed valve is a 3/2-way valve with a tank connection which is shut off in the open position and which is connected to the main feed line in the blocking position in order to relieve the latter.

The two working lines can preferably be connected to the secondary feed line via a respective high-pressure valve, with the high-pressure valve being an electro-proportional valve which can be opened via the respective working pressure of the working line in order to relieve it - Eg electromagnetic - actuator controlled. Pressure peaks are no longer reduced via the HP valves, as a result of which the efficiency and service life of the additional drive according to the invention increases due to the lower temperature input in the closed circuit.

Preferably, an anti-cavitation valve is arranged parallel to each HP valve, which is designed as a non-return valve whose opening direction is directed from the feed side line to the respective working line.

Preferably, the feed bypass can be relieved via a feed pressure reducing valve to a pressure medium sink.

According to a first variant, the feed pressure reducing valve is a shut-off valve which, in an open position preloaded, for example by a spring, connects the feed branch line to the pressure medium sink, and which shuts off the feed branch line from the pressure medium sink in a blocking position actuated by a - for example electromagnetic - actuator. According to a second variant, the feed pressure reducing valve is an electro-proportional valve which can be opened via the pressure of the feed bypass line and which can be controlled via an electromagnetic actuator.

The transverse scavenging valve can be a 3/2-way valve which, in an open position preloaded - e.g. by a spring - connects the main feed line to the tank connection of the radial piston engine, and which in a closed position shuts off the main feed line from the tank connection and relieves the tank connection to a pressure medium sink. This ensures cross-flushing with boost pressure medium even if the cross-flush valve is not activated.

In connection with the cross-flushing to one of the two working lines, the pressure of the secondary feed line preferably acts in the direction of the closed position of the cross-flushing valve.

In connection with the transverse flushing to the second tank connection of the at least one housing, an electromagnetic actuator preferably acts in the direction of the closed position of the transverse flushing valve.

Furthermore, it is advantageous if at least one scavenging valve designed as a 3/3-way valve is provided for the closed circuit.

According to a first variant, such a scavenging valve is provided on the at least one radial piston motor, via which one of the two working connections can be selectively connected to the interior of the housing.

According to a second variant, the flushing valve is arranged on the variable displacement pump.

Several exemplary embodiments of a hydrostatic auxiliary drive according to the invention are shown in the figures.

Show it

Figure 1 shows a circuit diagram of the hydrostatic auxiliary drive according to the invention according to a first embodiment,

Figure 2 shows a circuit diagram of the hydrostatic auxiliary drive according to the invention according to a second embodiment,

Figure 3 shows a circuit diagram of the hydrostatic auxiliary drive according to the invention according to a third embodiment, FIG. 4 shows a circuit diagram of the hydrostatic additional drive according to the invention according to a fourth exemplary embodiment,

FIG. 5 shows a circuit diagram of the hydrostatic additional drive according to the invention according to a fifth exemplary embodiment,

FIG. 6 shows a circuit diagram of the hydrostatic additional drive according to the invention according to a sixth exemplary embodiment,

FIG. 7 shows a circuit diagram of the hydrostatic additional drive according to the invention according to a seventh embodiment,

FIG. 8 shows a circuit diagram of the hydrostatic additional drive according to the invention according to an eighth exemplary embodiment,

FIG. 9 shows a circuit diagram of the hydrostatic additional drive according to the invention according to a ninth exemplary embodiment,

FIG. 10 shows a circuit diagram of a valve block of the additional drive according to the invention with an alternative feed pressure reducing valve,

FIG. 11 shows a circuit diagram of a valve block of the additional drive according to the invention with an alternative transverse flushing valve, and

FIG. 12 shows a radial piston engine of the additional drive according to the invention.

Figures 1 to 3 show the first to third embodiment of the hydrostatic auxiliary drive according to the invention. The additional drive is installed in a truck and its two wheel motors, designed as radial piston motors 1 with constant displacement, act on its two front wheels. The two radial piston engines 1 are supplied via a closed circuit with two working lines A, B, in which a valve block 2 is arranged.

A variable displacement pump 4 is used. Here, a scavenging valve 6 for the closed circuit according to the first and third exemplary embodiment is installed on the variable displacement pump 4 or according to the second exemplary embodiment on the radial piston motors 1 in each case. When using a flow divider (not shown here) for a right/left split, the flushing valve 6 must be installed on the variable displacement pump 4.

The valve block 2 has two proportionally controllable HP valves 8 . In the de-energized state, the pressure difference is Obar. This results in a fail-safe function. At maximum current flow, the pressure difference between the two working lines A, B is at its maximum. At the same time, an A/B bypass is implemented via the HP valves 8 . The result is a “hydraulic” clutch. Parallel to the two HP valves 8, two anti-cavitation valves 10 designed as non-return valves are provided, which are used for feeding into the working line A, B on the low-pressure side from a feed branch line 12 of a feed pressure supply.

The feed pressure supply also has a check valve 14 with 3 bar for the differential pressure between a pressure medium sink T and housings 16 of the radial piston motors 1, so that cross-flushing is possible when the additional drive is deactivated, and at the same time the pistons 15 in the radial piston motor 1 remain retracted. (Compare Figure 12.)

With further reference to FIGS. In the de-energized state, a flow to the pressure medium sink T is open. A fail-safe function results. The feed pressure reducing valve 17 enables the working lines A, B to be placed against the tank via the pressure medium sink T or to build up the feed pressure in the feed bypass line 12 in a closed circuit in the blocking position and in the bypass of the working lines A, B.

An electrically controlled 3/2-way valve serving as a feed valve 18 is provided between the main feed line 21 and a feed pump 24 . A de-energized open position is provided for line breakage. This results in a fail-safe position that causes make-up and cross-flushing. In the event of a line breakage, the feed valve 18 is actuated and switched to the blocking position. The make-up is interrupted, i.e. it is no longer possible for pressure medium to escape. At the same time, the HP valves 8 and the feed pressure reducing valve 17 are de-energized, and the variable displacement pump 4 is decoupled from a spur gear (not shown) serving as a power take-off.

The feed pump 24 is designed as a gear pump and is driven by a diesel PTO. The feed pressure protection takes place directly at the feed pump 24. This has the advantage that in the event of a cold start, an internal hydraulic short circuit (pressure side-pressure valve-suction side) occurs directly at the feed pump 24. The short-circuit causes a local temperature input and a warm-up phase results.

Pressure sensors 19 on the working lines A, B are used to monitor the working pressure. If this working pressure is permanently 0 bar on at least one working line A, B, a line break is detected.

An electrically controlled 3/2-way valve serving as a cross-flush valve 120 is connected between a main feed line 21 and a cross-flush outlet L of the valve block 2 or first tank connections T1 of the two housings 16 of the radial piston engines 1 are provided. The transverse scavenging valve 120 activates and deactivates the transverse scavenging or the associated pressure in the housings 16 of the radial piston motors 1, preferably with a time delay, so that the pistons 15 can move in and out in a controlled manner. This transverse flushing takes place when the additional drive is deactivated. The two radial piston motors 1 are also cooled in the process.

In the exemplary embodiment 1 according to FIG. 1, the cross-flushing takes place from the first tank connection T1 to the second tank connection T2. In the exemplary embodiments 2 and 3 according to Figures 2 and 3, the cross-flushing takes place from the first tank connection T1 to the working line A or working line B Working line A, B a check valve 22 is arranged.

According to the invention, the pressure regulator on the variable displacement pump 4 can be overridden by a DRE valve of the valve block 2 designed as a flow control valve 100 . For this purpose, the flow control valve 100 is connected on the one hand to the feed branch line 12 and on the other hand via a control pressure connection X of the valve block 2 to a control pressure surface 104 of a pressure control valve 101, which is designed as a continuously adjustable 3/2-way valve. This control pressure surface 104 acts on the pressure control valve 101 in the direction of increasing an actuating pressure in an actuating pressure space 102 of an actuating cylinder. Since the actuating pressure chamber 102 acts in the direction of reducing the delivery volume Vg of the variable displacement pump 4, the loading of the control pressure surface 104 of the pressure control valve 101 with feed pressure medium acts in the direction of a reduction in the delivery volume Vg of the variable displacement pump 4 and thus the working pressure.

The variable displacement pump 4 begins control at Vg _max . This means that as soon as the admissible set working pressure is exceeded, the variable displacement pump 4 automatically regulates against a smaller delivery volume Vg. This also allows a constant torque on the front wheels. According to the invention, in the exemplary embodiments 1 to 3, this enables traction operation independent of the slip of the rear wheels.

So that the pressure regulation according to the invention is possible independently of the slip both in traction operation and in overrun operation, the variable displacement pump 4 according to the exemplary embodiments shown in FIGS. 203 expanded. In overrun mode, the 4/2-way valve 103 must be switched so that the pressure control according to the invention remains possible. The two options described below relate to the automatic switching of the 4/2-way valve 103; 203

FIGS. 4 to 6 show the fourth to sixth exemplary embodiment of the hydrostatic auxiliary drive according to the invention, designed as an auxiliary drive, according to a first option. The 4/2-way valve 103 is electrically controlled and switched so that the pressure control according to the invention remains possible when the additional drive changes from traction mode to overrun mode.

Figures 7 to 9 show the seventh to ninth embodiment of the hydrostatic auxiliary drive according to the invention according to a second option. The 4/2-way valve 203 is hydraulically pilot-controlled and switches over automatically in overrun mode, so that the pressure regulation according to the invention remains possible when the additional drive changes from traction mode to overrun mode.

In the second option according to FIGS. 7 to 9, an electrical 3/2-way valve 221 is used for pilot control. In a spring-biased position (shown in FIGS. 7 to 9), the 3/2-way valve 221 transmits the working pressure of the first working line A to a control pressure surface of the 4/2-way valve 203. In a position switched by an electric actuator, it transmits the 3/2-way valve 221 transmits the working pressure of the second working line B to the control pressure surface of the 4/2-way valve 203. This means that the additional drive can be controlled independently of the slip on the main drive during overrun and traction operation when driving forwards and backwards.

Figure 10 shows a circuit diagram of the valve block 2 with an alternative feed pressure reducing valve 117. It is an electrically proportional valve to the pressure medium sink T. This enables a proportional build-up of feed pressure and thus controlled actuation of an indirectly controlled cross-flush valve 20, which is responsible for the housing pressure and the cross-flushing of the Radial piston engines 1 can be used.

FIG. 11 shows a circuit diagram of the valve block 2 with an alternative transverse flushing valve 20. It is a hydraulically pilot-controlled 3/2-way valve instead of the electrically operated 3/2-way valve.

During cross-flushing from the first tank connection T1 to the working lines A, B, the cross-flushing valve 20 can be hydraulically pilot-controlled in order to bring it into the blocking position. Above a certain pressure level, the cross-scavenging valve 20 switches to the blocking position and the amount of food goes via the check valve 14 from the main food line 21 into the Meal bypass 12. This is done automatically. The advantage is that only the 2/2-way valve has to be switched to the tank (block).

During cross-flushing from the first tank connection T1 to the second tank connection T2, the electrically controlled cross-flushing valve 120 according to Figures 1 to 9 must be used, because even if A/B are not switched against T (block), no feed pressure is built up because the feed quantity goes from the first tank port T1 to the second tank port T2. Therefore, the hydraulically pilot operated cross-flush valve 20 would not function.

FIG. 12 shows a radial piston engine 1 of the additional drive according to the invention. It has a cam ring 13 which forms part of the housing 16. A rotor is arranged inside, in which star-shaped pistons 15 are arranged, which perform radial working strokes.

An activation sequence of the additional drive according to the invention when the truck concerned is stationary or driving consists of the following steps:

1. The boost pressure reducing valve 17 is shut off. Pressure builds up in the main feed line 21 and in the feed side line 12.

2. The transverse scavenging valve 20 is actuated indirectly via the build-up of feed pressure, or the transverse scavenging valve 120 is electrically actuated secondarily, so that the transverse scavenging outlet L is connected to the pressure medium sink T.

3. Activation

According to an activation option 1, a friction clutch from the spur gear (both not shown) to the variable displacement pump 4 is closed. The variable displacement pump 4 is thus brought to a specific operating speed. Then the HP valves 8 are energized. There is a separation of the working lines A, B, so a dp structure is possible. The disadvantage is the load on the friction clutch due to the differential speed.

According to an activation option 2, the HP valves 8 are energized. The working lines A, B are separated. The variable displacement pump 4 is thus brought to a specific operating speed. The friction clutch from the spur gear to the variable displacement pump 4 is closed, so the dp structure is possible. The differential speed is low, which protects the friction clutch.

Disclosed is a hydrostatic auxiliary drive to support a main drive, wherein a variable displacement pump 4 of the auxiliary drive is designed and controlled in such a way that a Pressure control and thus torque control is possible independently of the slip on the main drive.

Reference list:

1 radial piston motor

2 valve block

4 variable displacement pump

6 purge valve

8 HP valve

10 anti-cavitation valve

12 food bypass

13 cam ring

14 check valve

15 pistons

16 housing

17 boost pressure reducing valve

18 feed valve

19 pressure sensor

20 transverse flushing valve 21 main feed line 22 check valve 24 feed pump 100 flow control valve 101 pressure control valve 102 control pressure chamber

103; 203 4/2-way valve 104 Control pressure area 117 Boost pressure reducing valve 120 Cross-flushing valve 221 3/2-way valve

A first working line

B second working line

L Cross flushing connection

T Pressure medium sink of variable displacement pump or valve block

T1 first tank connection of the housing

T2 second tank port of the housing

X Pilot pressure port

Claims

patent claims

1. Hydrostatic auxiliary drive with a variable displacement pump (4) which is connected in a closed circuit to a hydrostatic engine arrangement via two working lines (A, B), the variable displacement pump (4) having a pressure control valve (101), a control pressure surface of the pressure control valve ( 101) acts in the direction of reducing the working pressure of the variable displacement pump (4), and wherein the control pressure surface can be connected to a feed pressure supply via an electrically actuated flow valve (100).

2. Hydrostatic auxiliary drive according to claim 1, wherein the pressure control valve (101) is a 3/2-way valve which supplies an actuating pressure chamber (102) of an actuating cylinder of the variable displacement pump (4) acting in the direction of reducing the working pressure either via a first connection with the working pressure leading working line (A, B), or relieves this actuating pressure chamber (102) via a second connection to a pressure medium sink (T), with a changeover valve, which is designed as a 4/2-way valve (103; 203), and with the both connections of the 3/2-way valve and with the working line (A, B) carrying the working pressure and the pressure medium sink (T).

3. Hydrostatic auxiliary drive according to claim 2, wherein the switching valve can be switched via an electric actuator.

4. Hydrostatic auxiliary drive according to claim 2, wherein the switching valve can be switched via a pilot valve, which is designed as a 3/2-way valve.

5. Hydrostatic auxiliary drive according to one of the preceding claims, wherein the feed pressure supply has a feed pump (24), a feed valve (18), a main feed line (21) and a feed branch line (12), the feed pump (24) being connected via the feed valve (18) connected to the main feed line (21), and wherein the main feed line (21) can be connected to the secondary feed line (12) via a preloaded non-return valve (14), the opening direction of the non-return valve (14) being from the main feed line (21) to the secondary feed line (12 ) is directed, and wherein the flow control valve (100) is connected to the food bypass (12).

6. Hydrostatic auxiliary drive according to claim 5, wherein a transverse flushing valve (20; 120) is connected to the main feed line (21), and wherein the motor arrangement comprises at least one radial piston motor (1) with a housing (16), a cam ring (13) and has a plurality of pistons (15), the housing (16) having a first tank connection (T1) which is connected to the cross-flush valve (20; 120), and wherein when an interior of the housing (16) is supplied via the cross-flush valve (20; 120) and cross-flushing of the interior is realized via the first tank connection (T1).

7. Hydrostatic auxiliary drive according to claim 6, wherein the housing (16) of the at least one radial piston motor (1) has a second tank connection (T2), the cross-flushing being realized from the first tank connection (T1) through the interior to the second tank connection (T2).

8. Hydrostatic auxiliary drive according to Claim 6, in which the interior of the housing (16) of the at least one radial piston motor (1) can be connected to the two working lines (A, B) via a respective check valve (22), with an opening direction of the two check valves (22 ) is directed from the interior to the respective working line (A, B), the cross-flushing being realized from the first tank connection (T1) via one of the check valves (22) to the working line (A, B) connected thereto.

9. Hydrostatic auxiliary drive according to one of Claims 5 to 8, in which the feed valve (18) connects the feed pump (24) to the main feed line (21) in a preloaded open position, and in which the feed valve (18) in a blocking position actuated by an actuator closes the The feed pump (24) is shut off from the main feed line (21), and a pressure sensor (19) is connected to each working line (A, B).

10. Hydrostatic auxiliary drive according to one of claims 5 to 9, wherein the two working lines (A, B) can be connected to the feed side line (12) via a respective HP valve (8), the HP valve (8) being an electro-proportional valve is, which can be controlled via the respective working pressure of the working line (A, B), and which can be controlled via a respective actuator.

11. Hydrostatic auxiliary drive according to one of claims 5 to 10, wherein the feed bypass line (12) via a feed pressure reducing valve (17, 117) to a pressure medium sink (T) can be relieved.

12. Hydrostatic auxiliary drive according to claim 11, wherein the feed pressure reducing valve (17) is a shut-off valve which, in a prestressed open position, connects the feed branch line (12) to the pressure medium sink (T), and in a blocking position actuated by an actuator, the feed branch line (12) against the pressure medium sink (T) shuts off.

13. Hydrostatic auxiliary drive according to claim 11, wherein the feed pressure reducing valve (117) is an electro-proportional valve which can be opened via the pressure of the feed bypass line (12) and which can be controlled via an electromagnetic actuator.

14. Hydrostatic auxiliary drive according to one of claims 5 to 13, wherein the

Cross-flush valve (20; 120) is a 3/2-way valve in a biased

Open position connects the main feed line (21) to the tank connection (T1) of the radial piston motor (1), and in a closed position the main feed line (21) is blocked from the tank connection (T1) and the tank connection (T1) is relieved to a pressure medium sink (T).

15. Hydrostatic auxiliary drive according to claims 8 and 14, wherein the pressure of the feed bypass line (12) acts in the direction of the closed position of the transverse flushing valve (20).

16. Hydrostatic auxiliary drive according to claims 7 and 14, wherein an electromagnetic actuator acts in the direction of the closed position of the transverse scavenging valve (120).