VARIABLE DISPLACEMENT TRANSMISSION PUMP AND CONTROLLER WITH ADAPTIVE CONTROL

Abstract

A variable displacement transmission pump having a controller for adjusting the displaced volume, which controller actuates corresponding adjuster actuators of the adjustable pump via a control valve, so that the pump can be adjusted from minimum to maximum displaced volume in order to achieve a constant pump outlet pressure for supplying a hydraulically operated transmission, wherein for different operating points of both the adjustable pump and the transmission, the input variables of the controller are adjusted in such a way that, independently of the individual operating points, the overall damping of the control system comprising pump and transmission—that is, using corresponding influence variables from these systems—can be maintained substantially constant under variable operating conditions by means of adjustable controller amplification.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit and priority of German Application No. DE 10 2014 101 638.6 filed Feb. 11, 2014. The entire disclosure of the above application is incorporated herein by reference.

FIELD

The present disclosure is related to a transmission pump especially a motor oil/lubrication pump with variable displacement and control. Control of the outlet pressure of a variable displacement transmission pump has the task of maintaining the pump outlet pressure constant independently of the amount of the volume flow of the consumer. For this purpose, the pump delivery rate is influenced in such a way that only the volume flow actually required by the consumer is delivered. The pressure control is implemented by hydraulic-mechanical means, a force difference acting on a differential piston being used as an input variable. This force difference must be selected to be appropriate for all operating points and must be set permanently prior to installation of the pump.

BACKGROUND

This section provides background information related to the present disclosure which is not necessarily prior art.

In modern passenger car automatic transmissions, the trend is toward wide pressure spreads (1 to 40 bar) and small delivery quantities (10 L per minute), in order to achieve the lowest possible power consumption by the pump and therefore greater efficiency of the transmission. Especially in the case of a pressure-controlled pump, this presents numerous problems. Above all, robust control stability is necessary for reliable operation of the pump in the transmission. However, with a constant controller gain designed for the critical operating point of the total system, a corresponding inertia in the dynamics and a huge controller deviation/hysteresis of the total system at non-critical operating points must necessarily be accepted.

SUMMARY

This section provides a general summary of the disclosure and is not intended to be a comprehensive disclosure of its full scope or of all its objectives and features.

It is therefore the object of the present disclosure to provide a pump system including a variable displacement transmission pump with a pressure control system and a corresponding controller which is configured to overcome the problems associated with conventional pumps.

The object is achieved by a pump system having a controller which actuates corresponding adjuster actuators of the adjustable pump via a control valve, so that the pump can be adjusted from a minimum to a maximum displaced volume in order to achieve a constant pump outlet pressure for supplying a hydraulically-operated transmission. Specifically, for different operating points of both the adjustable pump and the transmission, the input variables of the controller are adjusted in such a way that, independently of the individual operating points, the overall damping of the control system comprising the pump and the transmission—that is, using corresponding influence variables from these systems—can be maintained substantially constant under variable operating conditions by means of adjustable controller amplification.

The object is additionally achieved by a pump system constructed in accordance with the present disclosure wherein a pressure-dependence of the adjustable controller amplification is varied according to the equation

$V_R\sim \frac{1}{\sqrt{p}}$

(p is the actual system pressure at the transmission inlet, VR is the controller amplification.)

In accordance with these objects, an inventive pump system constructed in accordance with the present disclosure is characterized in that a rotational-speed dependence of the adjustable controller amplification is defined by the equation

$V_R\sim \frac{1}{n}$

(pump rotational speed).

An inventive pump system constructed in accordance with the present disclosure is characterized in that a delivery-rate dependence of the amplification V_R is defined by the equation V_R˜Q² (Q equals volume flow rate).

An inventive pump system constructed in accordance with the present disclosure is characterized in that the dependence of a load capacity comprising the transmission and line volumes, in particular the volumes of the transmission clutches subjected to pressure, is defined by the equation

$V_R\sim \frac{1}{\left(C_{\mathrm{HO}}+\sum C_{H,i}\right)},$

where C_HO represents the basic capacity of the lines subjected to pressure and volume flow, and C_H,i represents the individual capacity of a respective transmission clutch subjected to pressure.

An inventive pump system constructed in accordance with the present disclosure is characterized in that a damping factor D₀, which is to be maintained constant overall in dependence on the operating point by this control system, is represented by the equation

$D_0=\frac{G_L}{2}\sqrt{\frac{A_K}{V_R·V_S·V_V·C_0·C_{0P}·C_H}},$

where G_L corresponds to the conductance coefficient of a consumer throttle at the pump outlet, A_K corresponds to the piston area at the actuator of the adjustable cam ring, V_S corresponds to the transducer value of a pressure sensor, V_V corresponds to the transmission value of a valve, C₀ corresponds to the flow amplification of a valve, C_0P to the flow amplification of the pump, and C_H corresponds to the total hydraulic line capacity between pump and the consumers terminating the line.

An inventive pump system constructed in accordance with the present disclosure is characterized in that the rotational speed n and the system pressure p are input and processed in a first region of the controller via corresponding signals.

An inventive pump system constructed in accordance with the present disclosure is characterized in that the output signal is processed in a second controller region together with a signal representing the total hydraulic line capacity C_H.

An inventive pump system constructed in accordance with the present disclosure is characterized in that the signal from the second controller region is fed to a third controller region in which it represents, together with a reference value U_Soll and the signal of a pressure sensor at the pump outlet, the actual controller signal for adjusting a control valve which correspondingly activates the actuators or actuator in the pump for adjusting the displaced volume.

An inventive pump system constructed in accordance with the present disclosure is characterized in that the adjustable controller amplification decreases with increasing outlet pressure and/or with increasing pump rotational speed and/or with decreasing delivery rate and/or with increasing load volume.

An inventive pump system constructed in accordance with the present disclosure is characterized in that the adjustable controller amplification is increased with decreasing pump outlet pressure and/or with decreasing pump rotational speed and/or with increasing delivery rate of the pump and/or with decreasing load volume of the transmission.

An inventive pump system constructed in accordance with the present disclosure is characterized in that, as a result of the aforementioned controller amplification changes, the damping factor of the total control loop comprising pump and transmission, as the so-called load, remains substantially constant and therefore stable.

Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

DRAWINGS

The invention will now be described with reference to the figures wherein:

FIG. 1 shows an inventive pump system having a variable displacement pump and a corresponding control system in accordance with the present disclosure; and

FIG. 2 shows schematically in a diagram a dependency of the amplification V as a function of the system pressure p and the rotational speed n (pump outlet pressure and pump rotational speed and controller amplification V).

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference to the accompanying drawings.

FIG. 1 shows schematically an adjustable pump 1 such as, for example, an adjustable vane pump with an adjustable cam ring 3 which can be adjusted to various positions by a first actuator 5 and a second actuator 7 together with a spring 9. The first actuator 5 is subjected to the pump outlet pressure in the line 11, while the second actuator 7, which has an appropriately larger effective pressurized area than the first actuator 5, is subjected to a control pressure, which can be influenced by a control valve 15, in the feed line 13 of the second actuator 7. The control valve 15 can be supplied with the pump outlet pressure from the line 11, which leads further to the hydraulic consumer, in this case a transmission, and can be suitably varied according to the opening cross section of the control valve 15, which is adjustable by a proportional solenoid 19. The piston of the proportional control valve 15 has on one side a spring 21 and a pressure chamber 27, which leads via a essentially unpressurized line 23 to a tank or oil sump of the transmission, and has on the other side, between the proportional solenoid 19 and the valve piston, a further line 25, which is also connected to the tank pressure line 23. The spring 21 holds the equilibrium for a particular position against the force of the proportional solenoid 19 when the proportional solenoid 19 is energized with a corresponding solenoid current i supplied by a controller 33. The tank line or feed line to an oil sump 23 is further connected to the pump intake chamber 29. The current i for the proportional solenoid 19 is supplied by a suitable amplifier 31 which, in turn, receives its input variable from the controller 33. The controller 33 represents a total controller region comprising the regions 33, 35 and 37, which are also referred to as the first controller region 37, the second controller region 35 and the third controller region 33. The first controller region 37 processes, as input variables, the pump rotational speed n and the system pressure p supplied by the pump 1 to the transmission, to form the corresponding functions which describe the hydraulic and physical dependencies. The first controller region 37 generates a corresponding input signal for the second controller region 35, which additionally processes the hydraulic capacities C_H, which comprise the line volumes up to the corresponding consumers or the volumes which are present by virtue of the corresponding clutches in the automatic transmission and are pressurized correspondingly in order to actuate the clutch. The output signal 2 of this second controller region 35 is, in turn, supplied to the third controller region 33, which processes as further input signals the reference value U_soll of the controller and the signal of a corresponding pressure sensor 39, the pressure sensor 39 capturing the outlet pressure towards the transmission inlet, meaning the system pressure, generated by the pump 1.

As a result of this arrangement of the pump, the pump controller and the pump control system, the controller amplification is adjustable as a function of the operating point of the hydraulic load system—that is, of both the transmission and the pump itself. In what follows, the concept of controller amplification encompasses all the controller components which operate proportionally, integrally and differentially. During a change in the controller amplification, moreover, only individual components of the controller amplification may be concerned, depending on the operating point of the total system. As a criterion for the controller amplification, the formula of the damping factor, for example for a simplified model of an electrohydraulic pump control system, is used. The pump pressure is controlled to a reference value. By means of the pressure sensor in the vicinity of the pump outlet, a signal which can be processed by this electrical controller is compared to the reference value and a control signal for the electrically activated hydraulic valve, the proportional valve, is output. Depending on the position of the valve, the pump is subjected to a hydraulically generated force which increases or reduces the displaced volume. The real damping factor of the pressure control system is influenced, in addition to the parameters specified in the formula, by losses in the valve, internal forces of the pump and leakages, which are disregarded here for simplicity. Therefore the damping factor result essentially in:

$D_0=\frac{G_L}{2}\sqrt{\frac{A_K}{V_R·V_S·V_V·C_0·C_{0p}·C_H}}$

where G_L is the conductance coefficient of a so-called consumer throttle, that is, of the total system of the transmission, at the pump outlet, A_K is the piston area at the actuator (cam ring), V_S is the transducer value of the pressure sensor, V_V is the transmission value of the valve, C₀ is the flow amplification of the valve, C_0P is the flow amplification of the pump, and C_H is the hydraulic line capacity between pump and consumer.

The above-mentioned controller amplification, which is adaptively varied appropriately, is contained here as the constant V_R. The objective for the adjustable controller amplification should therefore be a constant damping factor under variable operating conditions. The controller amplification dependencies represented below are therefore yielded:

Pressure Dependence:

Since C₀˜√{square root over (p)}, the controller amplification should be variable according to

$V_R\sim \frac{1}{\sqrt{p}}.$

Rotational Speed Dependence:

The flow amplification of the pump C_0p is proportional to the pump rotational speed; a controller amplification should therefore be adapted using

$V_R\sim \frac{1}{n}.$

Displaced Quantity Dependence:

Since the conductance of the consumer throttle behaves proportionally to the displaced quantity Q,

V_R˜Q²

applies as orientation for an adaptation of controller amplification.

Dependence on Line Capacity:

The hydraulic capacity between pump outlet and consumer is difficult to establish. However, as it is determined substantially by the number and size of the pressurized clutches in the transmission, it is appropriate to adapt the controller amplification when varying the pressurisations of the clutches in the transmission. When regulating a pump outlet pressure the following applies:

$V_R\sim \frac{1}{C_R}.\mathrm{Therefore},V_R\sim \frac{1}{\left(C_{\mathrm{HO}}+\sum C_{H,i}\right)}$

may apply for a pump outlet pressure regulation, where C_H,i is an individual capacity of a clutch and C_H0 is the basic capacity of the line.

FIG. 2 then shows schematically the interdependence between the controller amplification V (or V_R), the system pressure p (that is, the outlet pressure at the pump outlet or the inlet pressure for the transmission system), and the rotational speed n (that is, the pump rotational speed).

It can be seen purely schematically that as the system pressure p rises the controller amplification must fall, and that as the rotational speed n rises the amplification must likewise fall. Accordingly, this gives rise to an overall, three-dimensional input-output map to which the corresponding pump control system must conform in dependence on the operating point.

LIST OF REFERENCES

• 1 Pump
• 3 Cam ring
• 5 Actuator
• 7 Actuator
• 9 Spring
• 11 Line
• 13 Feed line
• 15 Control valve
• 19 Proportional solenoid
• 21 Spring
• 23 Line
• 25 Line
• 27 Pressure chamber
• 29 Pump intake chamber
• 31 Amplifier
• 33 Controller region
• 35 Controller region
• 37 Controller region
• 39 Pressure sensor

Claims

1. A. variable displacement transmission pump having a controller for adjusting the displaced volume, wherein the controller actuates corresponding adjuster actuators of the adjustable pump via a control valve so that the pump can be adjusted from a minimum to a maximum displaced volume in order to achieve a constant pump outlet pressure for supplying a hydraulically-operated transmission, wherein for different operating points of both the adjustable pump and the transmission, the input variables of the controller are adjusted in such a way that, independently of the individual operating points, the overall damping of a control system comprising the pump and the transmission—that is, using corresponding influence variables from these systems—can be maintained substantially constant under variable operating conditions by means of adjustable controller amplification.

2. The pump according to claim 1, wherein a pressure-dependence of the adjustable controller amplification (VR) is varied according to the equation

3. The pump according to claim 1, wherein a rotational-speed dependence of the adjustable controller amplification (VR) is defined by the equation

4. The pump according to claim 1, wherein a delivery-rate dependence of the adjustable controller amplification (VR) is defined by the equation VR˜Q2 (Q=volume flow rate).

5. The pump according to claim 1, wherein the dependence of a load capacity comprising the transmission and line volumes, in particular the volumes of clutches subjected to pressure, is defined by the equation

6. The pump according to claim 1, wherein a damping factor D0, which is to be maintained constant overall in dependence on the operating point by the control system, is represented by the equation

7. The pump according to claim 1, wherein a rotational speed n and a system pressure p are input and processed in a first controller region of the controller via corresponding signals.

8. The pump according to claim 7, wherein an output signal is processed in a second controller region of the controller together with a signal representing the capacity CH.

9. The pump according to claim 8, wherein the signal from the second controller region is fed to a third controller region in which it represents, together with a reference value USoll and the signal of a pressure sensor at the pump outlet, the actual controller signal for adjusting the control valve which correspondingly activates the actuators or actuator in the pump for adjusting the displaced volume.

10. The pump according to claim 1, wherein the controller amplification (VR) decreases with increasing outlet pressure (p) and/or with increasing pump rotational speed (n) and/or with decreasing delivery rate and/or with increasing load volume (Q).

11. The pump according to claim 1, wherein the controller amplification (VR) is increased with decreasing pump outlet pressure (p) and/or with decreasing pump rotational speed (n) and/or with increasing delivery rate of the pump and/or with decreasing load volume (Q) of the transmission.

12. The pump according to claim 1, wherein as a result of the aforementioned amplification (VR) changes, the damping factor (D0) of the total control loop comprising the pump and the transmission, as the so-called load, remains substantially constant and therefore stable.