Patent Description:
<CIT> discloses a hydraulic pressure supply system of an automatic transmission. In a first embodiment a first low pressure pump sucks a fluid from a reservoir via a line and supplies hydraulic fluid to a low pressure portion via a second line. A second pump, independent of the first pump, is a high pressure pump and draws the fluid from the low pressure line and supplies a portion at high pressure. The two pumps are simple pumps with a suction and a delivery. The second embodiment discloses a hydraulic pump which combines in the same pump the functions of the pumps of the first embodiment.

The object of the invention consists in creating a particularly compact pump unit which combines a multiplicity of different functions.

According to the invention, to achieve this object, a pump unit is provided, having a dual pump which has a suction port for drawing in from an external fluid reservoir and has a high-pressure outlet and a low-pressure outlet which lead to a first control port and to at least one lubricant/coolant port, respectively, of the pump unit, and having a high-pressure pump which draws in from an internal fluid reservoir and which has two high-pressure outlets which lead to a second and a third control port of the pump unit, wherein, between the high-pressure outlet of the dual pump and the first control port, there is arranged a control valve which has a return line which leads into the internal fluid reservoir. This pump unit has the advantage that it combines two different pumps, such that the overall installation process is simplified, because only a single component has to be installed. The pumps are different pumps, such that different types of fluid flows can be provided. The dual pump delivers both a low-pressure flow and a high-pressure flow, wherein the conveyed volume of the low-pressure flow is greater than the conveyed volume of the high-pressure flow. The low-pressure flow may be used for lubricating bearing points of the transmission or for cooling clutches or the electric motor. The high-pressure flow may be used for actuating a clutch. This also applies to the two high-pressure flows that are provided from the high-pressure outlets of the high-pressure pump. The return line of the control valve that is integrated into the pump unit makes it possible for the conveyed flow that is not required at the high-pressure port to be conducted directly into the internal fluid reservoir, such that the internal fluid reservoir is always sufficiently filled and the pump unit requires, overall, only one suction port to the outside.

According to one refinement of the invention, it is provided that the suction port of the pump unit and/or the high-pressure outlet of the dual pump is assigned a filter. This ensures that the high-pressure pump draws in only pre-filtered hydraulic fluid.

The dual pump may be a rotary vane pump having multiple rotary vanes which, together with a stator and a rotor, delimit multiple low-pressure chambers, wherein each rotary vane delimits a high-pressure chamber within the rotor. With a rotary vane pump configured in this way, it is possible for two different hydraulic oil flows to be provided, specifically firstly the "normal" low-pressure flow, which is provided by means of the conveying chambers of varying volume that are formed between adjacent rotary vanes. Secondly, it is also possible for a high-pressure flow to be generated by virtue of the rotary vanes acting as pistons of a piston pump, the pump chambers of which are delimited by the walls of the receiving slots for the rotary vanes in the rotor, by the face walls of the rotary vane pump and by a face side of the rotary vanes.

According to one refinement of the invention, a disconnection valve is provided which is arranged between the high-pressure outlet of the dual pump and the control valve of the first control port of the pump unit and the return line of which leads into the internal fluid reservoir. Losses are avoided in this way, because the dual pump cannot simply be shut off if, in the case of a clutch that can be actuated without leakage, the pressure can be maintained by means of the proportional valve; with regard to the lubricating and cooling requirements, the dual pump must normally be operated continuously.

In one embodiment of the invention, a shut-off valve is provided which is arranged between the low-pressure outlet of the dual pump and one of the lubricant/coolant ports of the pump unit. By means of the shut-off valve, the lubricating/cooling oil flow to a clutch can be shut off when said clutch does not require cooling. In this way, drag losses in the corresponding clutch are reduced.

In order to ensure that a minimum flow rate of a lubricating/cooling oil flow is maintained, a bypass line for the shut-off valve may be provided, wherein an aperture is arranged in the bypass line. With this configuration, a defined oil flow is provided, which is advantageous in particular if the clutch has hydraulic compensation chambers that should remain filled to a defined level.

In one embodiment of the invention, between the low-pressure outlet of the dual pump and one of the lubricant/coolant ports, there is arranged a build-up valve, the outlet of which is connected to the return lines of control valves that are arranged between one of the high-pressure ports of the high-pressure pump and the second and third control port respectively. By means of the build-up valve, a low-pressure oil flow can be conducted "backwards" through the control valves to the control ports and the actuators that are provided for switching the clutches. This makes it possible for the actuators, in the event of a switching demand, to be pre-filled very quickly up to a point at which the further supply of pressure is taken over by the high-pressure pump. This reduces the switching times.

The invention also provides a drive assembly having a transmission, having a separating clutch by means of which an electric motor can be coupled to and separated from the transmission, and having a pump unit of the above-stated type, wherein the suction port of the pump unit is connected to an oil collecting volume of the transmission, and one of the lubricant/coolant ports is used for the cooling of the rotor and of the stator. The particular advantage of this drive assembly consists in that only a single pump unit has to be installed, which draws in hydraulic oil from an oil collecting volume of the transmission and provides both the various hydraulic oil flows for the switching of the various clutches and an oil flow of relatively low pressure, but relatively high volumetric flow rate, which can be used for the cooling of clutches, bearing points and of the electric motor.

According to one refinement of the invention, it is provided that one of the lubricant/coolant ports is assigned a heat exchanger. By means of said heat exchanger, the temperature of the cooling oil flow that is conducted to the electric motor can be reduced, which has a particularly great effect on the efficiency of the electric motor.

In one embodiment, the low-pressure outlet of the dual pump provides a supply to at least two lubricant/coolant ports, wherein at least one of the lubricant/coolant circuits to which a supply is thereby provided is assigned a restrictor or an aperture. By means of the restrictor or aperture, it can be defined what proportion of the volumetric flow rate flows through which of the lubricant/coolant circuits.

The invention will be described below on the basis of various embodiments, which are illustrated in the appended drawings. In these drawings:.

<FIG> shows a first embodiment of a transmission <NUM> and of a pump unit <NUM> installed thereon.

Here, of the transmission <NUM>, a part of a transmission housing <NUM> is shown, in which an oil collecting volume <NUM> is provided. Also schematically shown are multiple transmission gear wheels <NUM> with which different transmission ratio stages can be engaged.

The pump unit <NUM> has a housing <NUM>, in the interior space of which a fluid reservoir <NUM> is delimited.

Arranged in the pump unit <NUM> is a dual pump <NUM>, which is driven by an electric motor <NUM>.

A "dual pump" is to be understood here to mean a hydraulic pump which has both a low-pressure outlet and a high-pressure outlet. Here, the low-pressure outlet is denoted by the reference sign <NUM>, and the high-pressure outlet is denoted by the reference sign <NUM>. During the operation of the dual pump <NUM>, this delivers a hydraulic fluid flow with a high volumetric flow rate but low pressure at the low-pressure outlet <NUM>, and a hydraulic fluid flow with a low volumetric flow rate but high pressure at the high-pressure outlet <NUM>.

One possible configuration of the dual pump <NUM> will be discussed further below with reference to <FIG>.

The dual pump <NUM> draws in hydraulic fluid from the oil collecting volume <NUM> of the transmission housing <NUM> via a suction port <NUM> of the pump unit <NUM>. Here, an oil filter <NUM> is provided in order to ensure that no contaminants pass into the pump unit <NUM>.

The low-pressure port <NUM> of the dual pump <NUM> serves, in general terms, for supplying hydraulic fluid to one or more lubricant/coolant ports of the pump unit <NUM>. In the exemplary embodiment shown, two lubricant/coolant ports S1, S2 are provided, wherein the port S1 serves for the cooling of one or more clutches, and the port S2 serves for the supply of lubricant to bearing points of the transmission <NUM>.

The ports or lines through which the lubricating/cooling fluid is provided may be assigned restrictors <NUM> in order to divide up the volumetric flow rates in the desired manner.

The high-pressure port <NUM> of the dual pump <NUM> supplies hydraulic fluid to a first high-pressure outlet K0 of the pump unit <NUM>. Via the high-pressure outlet K0, it is for example possible for a separating clutch, by means of which a drive motor can be coupled and decoupled, to be switched.

For the actuation of the clutch, a control valve <NUM> is provided between the high-pressure outlet <NUM> and the high-pressure port K0, which control valve is in this case designed preferably as an electrically actuated proportional valve, which is assigned a pressure sensor <NUM>.

When the control valve <NUM> is closed, the high-pressure fluid flow that is provided at the high-pressure outlet <NUM> of the dual pump <NUM> is conducted via the high-pressure outlet K0 to the clutch, or more specifically to an actuator by means of which the clutch is closed. If the control valve <NUM> is opened, a proportion or the entirety of the hydraulic oil flow is conducted via a return line <NUM> of the control valve <NUM> into the fluid reservoir <NUM> of the pump unit <NUM>.

In the pump unit <NUM>, there is also arranged a high-pressure pump <NUM> which is driven by an electric motor <NUM> and which draws in hydraulic fluid from the internal fluid reservoir <NUM> of the pump unit <NUM> via a drawing-in channel <NUM>.

The high-pressure pump <NUM> has two high-pressure outlets <NUM> which serve for supplying hydraulic fluid to two further high-pressure outlets K1, K2 of the pump unit <NUM>. The two clutches that are actuated via the high-pressure outlets K1, K2 may for example be the two clutches of a dual clutch, which can be actuated by means of the pump unit <NUM> such that a switch can be made from a first transmission stage to a second transmission stage of a dual-clutch transmission without an interruption in traction power.

In order to be able to suitably actuate the clutches that are assigned to the high-pressure ports K1, K2, the pump unit <NUM> has a second and a third control valve <NUM> which, like the control valve <NUM>, are designed as solenoid-type proportional valves, and which are each assigned a pressure sensor <NUM>.

Each of the control valves <NUM> has a return line <NUM> which, like the return line <NUM> of the control valve <NUM>, leads to the internal fluid reservoir <NUM>.

Yet further filters <NUM> may be arranged at various points within the pump unit <NUM>. It is hereby ensured that only pre-filtered hydraulic oil is supplied to the internal fluid reservoir <NUM>.

All hydraulic oil requirements within the transmission can be met by means of the pump unit <NUM>. Dual clutches can be actuated via the high-pressure ports K1, K2, and a separating clutch can be actuated via the high-pressure port K0. It is furthermore possible for each of the clutches to be fed with a suitable cooling oil flow that is adapted to the respective requirements. For example, the thermal load of the dual clutches is higher by a factor of <NUM> to <NUM> than the thermal load of the separating clutches. Here, the high-pressure pump <NUM> always draws in from the internal fluid reservoir <NUM>.

<FIG> shows an exemplary embodiment of a dual pump <NUM>. Here, this is a rotary vane pump with a stator <NUM> in which there is formed an interior space <NUM> which is surrounded by an inner wall <NUM>.

A rotor <NUM> is arranged in the interior of the stator <NUM> and is mounted on a shaft <NUM> and can be driven by the latter.

The rotor <NUM> is provided with multiple receptacles <NUM>, in which in each case one rotary vane <NUM> is received.

The receptacles <NUM> extend in the axial direction normally from a face side of the rotor <NUM> as far as the opposite face side, and from the outer periphery of the rotor inwards. In the exemplary embodiment shown, the receptacles <NUM> extend in the radial direction. This is not necessary, however.

Here, the rotary vanes are in the form of plates whose dimension in the radial direction is slightly less than the radial depth of the receptacles <NUM>. Each of the plates has a thickness b, which corresponds to the width of the receptacles <NUM>.

As an alternative to plate-like rotary vanes, use may also be made of rotary vanes which are in the form of a cylinder.

The rotor <NUM> has a diameter of <NUM> x r (minus a clearance between rotor and stator that is to be provided in the design), which is less than the diameter r+R of the interior space <NUM> of the stator <NUM>. The rotor <NUM> is arranged eccentrically in the interior space, specifically such that it is (almost) in contact with the inner wall <NUM> on one side (at the <NUM> o'clock position in this case). Accordingly, the maximum spacing to the outer wall of the rotor <NUM> is on the diametrically opposite side.

The rotary vanes <NUM> bear with their radially outer side <NUM> permanently against the inner wall <NUM> of the stator <NUM> (at any rate when the rotor <NUM> is rotating). Consequently, between rotary vanes <NUM> adjacent to one another in the peripheral direction, the inner wall <NUM> of the stator <NUM>, the outer wall of the rotor <NUM> and two side walls which close off the interior space <NUM> at the face sides of the rotor <NUM> (and of which only the "rear" side wall <NUM> can be seen here), in each case one low-pressure chamber <NUM> is delimited.

In the exemplary embodiment shown, since five rotary vanes <NUM> are present, it is also the case that five low-pressure chambers <NUM> are formed. The volume of each individual low-pressure chamber, for one rotation of the rotor <NUM> through <NUM>°, changes from a minimum value (when the low-pressure chamber <NUM> is approximately at the <NUM> o'clock position) via a maximum value (when the low-pressure chamber <NUM> is approximately at the <NUM> o'clock position) and back to the minimum value.

Hydraulic fluid is fed to the low-pressure chambers <NUM> through the inlet <NUM>. Said inlet, as seen in the direction of rotation of the rotor <NUM>, is situated behind the point at which the spacing between the outer surface of the rotor <NUM> and the inner wall <NUM> of the stator <NUM> is minimal.

The hydraulic fluid drawn in by the low-pressure chambers <NUM> via the inlet <NUM> is delivered via a low-pressure outlet <NUM>, which, as seen in the peripheral direction, is behind the position at which the low-pressure chambers <NUM> have the maximum volume, but in front of the position at which the spacing between the outer side of the rotor <NUM> and the inner wall <NUM> of the stator <NUM> is minimal.

The inlet <NUM> and the low-pressure outlet <NUM> are arranged here in one of the side walls <NUM> of the hydraulic pump <NUM> or else, so as to improve the filling, in both side walls <NUM>, so that the hydraulic fluid can be drawn into the low-pressure chamber <NUM>, and pushed out therefrom, from both sides.

Each of the rotary vanes <NUM> delimits together with the rotor <NUM> (and also the side walls <NUM>) in each case one high-pressure chamber <NUM>. Specifically, each radially inner side <NUM> of each rotary vane <NUM> delimits, together with the walls of the receptacle <NUM> and the side walls <NUM> shown, in each case one high-pressure chamber <NUM>.

The volume of the high-pressure chambers <NUM> changes according to the displacement of the rotary vanes <NUM> in the receptacles <NUM>. When the rotary vanes <NUM> move outwards (that is to say during a movement from the <NUM> o'clock position to the <NUM> o'clock position via the <NUM> o'clock position in the exemplary embodiment shown), the volume of the high-pressure chambers <NUM> increases, and when the rotary vanes <NUM> move inwards (that is to say during a movement from the <NUM> o'clock position to the <NUM> o'clock position via the <NUM> o'clock position), the volume decreases.

In this way, there is formed a piston pump in which the radially inner side <NUM> of each rotary vane <NUM> may be regarded as the face surface of a pump piston which is adjusted by means of a curved path (of the inner wall <NUM> of the stators <NUM>). For drawing-in, the pump piston is adjusted outwards under the action of centrifugal force, and for pushing-out, the pump piston is displaced inwards owing to the contour of the inner wall <NUM> of the stator <NUM>.

The high-pressure chamber <NUM> draws in via the same inlet <NUM> as that which provides a supply to the low-pressure chambers <NUM>.

A high-pressure outlet <NUM> which is separate from the low-pressure outlet <NUM> is provided on the pressure side of the high-pressure pump. In the peripheral direction, said high-pressure outlet is arranged approximately at the same position as the low-pressure outlet <NUM>.

The high-pressure outlet <NUM> may be provided either at only one of the side walls <NUM> of the stator <NUM> (and thus also of the rotor <NUM>) or at both face sides.

<FIG> shows a second embodiment. The same reference signs are used for the components known from the first embodiment, and, in this respect, reference is made to the explanations above.

The difference between the first and second embodiments is that, in the second embodiment, a disconnection valve <NUM> is arranged between the high-pressure outlet <NUM> of the dual pump <NUM> and the first control valve <NUM>. The disconnection valve <NUM> serves, in the open state, to discharge directly into the internal fluid reservoir <NUM> the hydraulic fluid that is conveyed by the dual pump <NUM> at the high-pressure port <NUM>, without said hydraulic fluid having to flow through the control valve <NUM>. In this way, the energy required for driving the dual pump <NUM> can be reduced in the phases in which, at the first high-pressure port K0, the fluid pressure can be maintained by the proportional valve alone.

<FIG> shows a third embodiment. The same reference signs are used for the components known from the preceding embodiments, and, in this respect, reference is made to the explanations above.

The difference between the first and the third embodiment consists in that, in the third embodiment, the lubricant flow that is provided at the lubricant/coolant port S2 is used for cooling a stator <NUM> and a rotor <NUM> of an electric motor, which is symbolized here merely by the stator <NUM> and the rotor <NUM>. The hydraulic oil subsequently passes to the bearing points and tooth meshing points of the transmission gearwheels <NUM>.

<FIG> shows a fourth embodiment. The same reference signs are used for the components known from the preceding embodiments, and reference is made to the explanations above.

The difference between the third and the fourth embodiment consists in that, in the fourth embodiment, restrictors <NUM> are provided, by means of which the volumetric flow rate through the stator <NUM> and the rotor <NUM> can be suitably set. In particular, a relatively large proportion of the volumetric flow rate is conducted through the stator, because more heat is generated there.

<FIG> shows a fifth embodiment. The same reference signs are used for the components known from the preceding embodiments, and, in this respect, reference is made to the explanations above.

The difference between the fifth and the fourth embodiment consists in that, in the fifth embodiment, a heat exchanger <NUM> is provided between the lubricant/coolant port S2 and the electric motor <NUM>, by means of which heat exchanger the temperature of the hydraulic oil used for cooling the electric motor <NUM> is reduced. This has a particularly advantageous effect on the efficiency of the electric motor <NUM>.

<FIG> shows a sixth embodiment. The same reference signs are used for the components known from the preceding embodiments, and, in this respect, reference is made to the explanations above.

The difference between the sixth and the fifth embodiment consists in that, in the sixth embodiment, a shut-off valve <NUM> is provided which is arranged between the low-pressure outlet <NUM> of the dual pump <NUM> and the first lubricant/coolant port S1.

By means of the shut-off valve <NUM>, the separating clutch to which cooling medium is supplied via the lubricant/coolant port S1 can be cooled in accordance with demand. After an actuation, the shut-off valve <NUM> is opened for a period of typically <NUM>-<NUM> seconds, such that the desired cooling action is attained. The shut-off valve <NUM> is subsequently closed again. In this way, drag losses in the open state of the separating clutch can be prevented.

<FIG> shows a seventh embodiment. The same reference signs are used for the components known from the preceding embodiments, and, in this respect, reference is made to the explanations above.

The difference between the sixth and the seventh embodiment consists in that, in the seventh embodiment, a bypass line <NUM> for the shut-off valve <NUM> is provided. An aperture <NUM> may be arranged in said bypass line. By means of the bypass line <NUM>, it is ensured that a minimum volumetric flow rate via the lubricant/coolant port S1 is provided even in the closed state of the shut-off valve <NUM>. This is expedient if a wet clutch with internally situated rotating pistons is involved; these require constant lubrication. Furthermore, it is possible in this way for the hydraulic compensation chambers that are required in this clutch type for compensating the centrifugal forces of the rotating oil to be kept in a filled state.

The particular advantage of a restrictor <NUM> consists in that it acts virtually independently of viscosity. The desired volumetric flow rate can thus be ensured independently of the temperature of the hydraulic oil.

<FIG> shows an eighth embodiment. The same reference signs are used for the components known from the preceding embodiments, and, in this respect, reference is made to the explanations above.

The difference between the eighth and the seventh embodiment consists in that, in the eighth embodiment, the cooling oil flow that is provided via the port S1 is divided into two separate cooling oil flows for the separating clutch (port K0) and the two dual clutches (ports K1, K2). Here, the volumetric flow rate can be suitably set by means of restrictors.

<FIG> shows a ninth embodiment. The same reference signs are used for the components known from the preceding embodiments, and, in this respect, reference is made to the explanations above.

The difference between the ninth embodiment and the eighth embodiment consists in that, in the ninth embodiment, a build-up valve <NUM> is provided between the low-pressure outlet <NUM> of the dual pump <NUM> and the second lubricant/coolant port S2.

If the build-up valve <NUM> is open, a supply is provided to the port S2, similarly to the situation in the preceding embodiments.

If the build-up valve <NUM> is closed, the volumetric flow rate of the low-pressure outlet <NUM> of the dual pump <NUM> is conducted via a build-up line <NUM> to the return lines <NUM> of the control valves <NUM>. This makes it possible for flow to pass through the control valves <NUM> "backwards", and thus for the clutch actuators that are connected to the high-pressure ports K1, K2 to be pre-filled in a very short time. In this way, in the presence of a shift demand, the corresponding clutches can be brought into the vicinity of the "biting point" very quickly. The control valves <NUM> subsequently take over the actuation of the clutches in order to control the transfer of the torque from one clutch to the other clutch. For this purpose, the high-pressure fluid provided via the high-pressure outlets <NUM> of the high-pressure pump <NUM> is then required.

Claim 1:
Pump unit (<NUM>) having a dual pump (<NUM>) which has a suction port (<NUM>) for drawing in from an external fluid reservoir (<NUM>) and has a high-pressure outlet (<NUM>) and a low-pressure outlet (<NUM>) which lead to a first control port (K0) and to at least one lubricant/coolant port (S1, S2), respectively, of the pump unit (<NUM>), and having a high-pressure pump (<NUM>) which draws in from an internal fluid reservoir (<NUM>) and which has two high-pressure outlets (<NUM>) which lead to a second and a third control port (K1, K2) of the pump unit (<NUM>), wherein, between the high-pressure outlet (<NUM>) of the dual pump (<NUM>) and the first control port (K0), there is arranged a control valve (<NUM>) which has a return line (<NUM>) which leads into the internal fluid reservoir (<NUM>).