GB2518389A

GB2518389A - Method and system for controlling the operating temperature of a boost pressure device

Info

Publication number: GB2518389A
Application number: GB1316667.3A
Authority: GB
Inventors: Jon Dixon; Andres Arevalo; Aaron John Oakley
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2013-09-19
Filing date: 2013-09-19
Publication date: 2015-03-25
Anticipated expiration: 2033-09-19
Also published as: DE102014218058A1; GB2518389B; GB201316667D0; CN104454195A; RU2665011C2; RU2014136579A; CN104454195B

Abstract

A method of controlling an operating temperature Tx of a boost pressure device, such as a turbocharger or supercharger, for a vehicle. The method comprising: determining a pressure difference ÎP (100) between a current operating pressure Px of the boost pressure device and a target boost pressure PLIM at which the boost pressure device operates at an operating temperature limit TLIM. Further determining a pressure step size dP (110), wherein the pressure step size dP is a function of the pressure difference ÎP and a predetermined number of pressure steps N, and successively adjusting the current operating pressure Px by the pressure step size dP (120) until the operating temperature Tx of the boost pressure device is substantially equal to the operating temperature limit TLIM. The method is an iterative approach which used knowledge of the boost pressure/mass flow relationship to solve for the highest boost pressure within the operating temperature limit, allowing better use of the available computing resources, thus giving a quicker response time.

Description

Method and System for Controlling the Operating Temperature of a Boost Pressure Device This invention relates to a method and a system for controlling the operating temperature of a boost pressure device, and particularly, but not exclusively, relates to adjusting the operating pressure of the boost pressure device such that the operating temperature of the boost device is substantially equal to an operating temperature limit.

Introduction

Boost pressure devices, such as turbochargers and superchargers, are components that may be used with an engine of a vehicle for the purpose of increasing the pressure of the air supplied to the engine via the intake manifold. An increase in the pressure of the air into the engine may result in an increase in performance and/or efficiency of the engine.

However, the amount by which the pressure of the air can be increased by may be constrained by an operating temperature limit of the boost pressure device, for example a maximum gas outlet temperature. Exceeding this operating temperature limit for extended periods may cause damage to the boost pressure device itself or components within the engine, which may affect the long-term reliability of the vehicle. The operating temperature of the boost pressure device may be limited, therefore, in accordance with the reliability requirements of the vehicle.

In order to reduce the operating temperature of the boost pressure device an operating pressure, e.g. a pressure ratio across the boost pressure device, must be restricted.

However, restricting the operating pressure of the boost pressure device may limit engine performance and may be detrimental to the overall fuel economy of the vehicle.

In order to obtain maximum engine efficiency and performance it is desirable to operate close to the operating temperature limit such that the boost pressure delivered from the boost pressure device is maximised. It is desirable therefore to control accurately and consistently the operating temperature of the boost pressure device within the operating temperature limit in order to achieve the best available performance and meet reliability requirements.

It is generally accepted that the boost pressure device within its normal operating range compresses with an efficiency dependent on the mass flow through it and pressure ratio across it. Boost pressure device manufacturers will generally supply a compressor characteristic map which plots contours of isentropic efficiency and compressor speed against air mass flow rate and compression ratio, both normalised to inlet temperature.

It is known to calculate an operating temperature estimate of the boost pressure device using S the mass flow rate and pressure ratio across the device. This outlet temperature estimate may then be used by a closed loop controller to lower iteratively the operating pressure until the operating temperature estimate is lower that the operating temperature limit, However, this approach has a number of drawbacks, such as calibration difficulties1 stability-performance trade-offs and limited dynamic response. Furthermore, using this method, a large number of iterations may be required in order to achieve the required operating pressure at the operating temperature limit, which may be computationally expensive and as a result not very responsive.

It is desirable therefore to calculate directly the boost pressure at which the boost pressure device must operate in order that the operating temperature is substantially equal to the operating temperature limit. This is not straightforward to achieve, however, as mass flow rate is itself a function of boost pressure and efficiency is a function of both.

The present invention seeks to address these issues.

Statements of Invention

According to a first aspect of the present invention there is provided a method of controlling an operating temperature of a boost pressure device for a vehicle, the method comprising: determining a pressure difference between a current operating pressure of the boost pressure device and a target boost pressure at which the boost pressure device operates at an operating temperature limit; determining a pressure step size, wherein the pressure step size is a function of the pressure difference and a predetermined number of pressure steps; and successively adjusting the current operating pressure by the pressure step size until the operating temperature of the boost pressure device is substantially equal to the operating temperature limit.

The method may further comprise determining an estimate for the target boost pressure at which the boost pressure device operates at the operating temperature limit. The estimate for the target boost pressure may be based upon the efficiency of the boost pressure device at the current operating pressure. The target operating pressure may be a function of the operating temperature limit and a predetermined boost pressure-mass air flow characteristic of the boost pressure device. The predetermined boost pressure-mass air flow characteristic of the boost pressure device relates to the efficiency of the boost pressure device, The predetermined boost pressure-mass air flow characteristic of the boost pressure device may be a characteristic performance map of the boost pressure device which plots contours of isentropic efficiency and operating speed against the mass air flow and a compression ratio of the boost pressure device, both normalised to a gas inlet temperature of the boost pressure device.

Adjusting the operating pressure of the boost pressure device may comprise successively decreasing the current operating pressure of the boost pressure device by a first pressure step size. Adjusting the operating pressure of the boost pressure device may comprise successively increasing the current operating pressure of the boost pressure device by a second pressure step size. The method may further comprise successively decreasing the operating pressure of the boost pressure device by the first pressure step size then successively increasing the operating pressure of the boost pressure device by the second pressure step size.

The current operating pressure of the boost pressure device may be successively decreased by the first pressure step size until the operating temperature of the boost pressure device is less than the operating temperature limit. The current operating pressure of the boost pressure device may be successively increased by the second pressure step size until the operating temperature of the boost pressure device is greater than the operating temperature limit.

The second pressure step size may be smaller than the first pressure step size, The second pressure step size may be a divisor of the first pressure step size.

The method may further comprise: determining a current operating temperature of the boost pressure device; and comparing the current operating temperature to the operating temperature limit.

The method may further comprise: repeatedly adjusting the current operating temperature until the current operating temperature is less than or more than the operating temperature limit.

The predetermined number of steps may be selected according to the performance requirements of the boost pressure device andior the vehicle. The predetermined number of pressure steps may relate to an optimal number of computations.

S The operating temperature limit may be a function of the performance requirements of the boost pressure device and/or the vehicle. The operating temperature limit may be selected in accordance with an ambient pressure. The operating temperature limit may be selected in accordance with an age factor of the boost pressure device and/or the vehicle. The operating temperature limit may be variable or fixed. The operating temperature may be a gas outlet temperature of the boost pressure device.

According to another aspect of the present invention there is provided a system of controlling an operating temperature of a boost pressure device for a vehicle, the system comprising: one or more control devices configured to: determine a pressure difference between a current operating pressure of the boost pressure device and a target boost pressure at which the boost pressure device operates at an operating temperature limit; determine a pressure step size, wherein the pressure step size is a function of the pressure difference and a predetermined number of pressure steps; and provide a signal, for example to a system pressure regulator, to adjust the pressure of the boost pressure device, the signal being configured to adjust the current operating pressure in a number of pressure steps such that the operating temperature of the boost pressure device is substantially equal to the operating temperature limit.

The system may further comprise one or more temperature sensors configured to measure the temperature of the boost pressure device. The system may further comprise one or more pressure sensors configured to measure the pressure of the boost pressure device and/or an ambient pressure. The control device may be a real-time embedded controller.

A vehicle or an engine may comprise the above mentioned system for controlling an operating temperature of the boost pressure device.

The boost pressure device may be a turbocharger or a supercharger. The boost pressure device may be a compressor, for example a compressor of a supercharger or a turbocharger. Alternatively, the boost pressure device may be a turbine, for example a turbine of a turbocharger.

The invention claimed here is an iterative approach which uses knowledge of the boost pressure/mass flow relationship to solve for the highest boost pressure which results in compressor outlet temperature at the operating temperature limit.

Any of the above mentioned pressures may be a pressure ratio of the boost pressure device.

For example, the pressure ratio may be a ratio of an inlet pressure to an outlet pressure of the boost pressure device.

The invention also provides software such as a computer program or a computer program product for carrying out any of the methods described herein, and a computer readable medium having stored thereon a program for carrying out any of the methods described herein. A computer program embodying the invention may be stored on a computer-readable medium, or it could, for example, be in the form of a signal such as a downloadable data signal provided from an Internet website, or it could be in any other form.

The control devices may be further configured to carry out any of the above-mentioned methods.

Brief Description of the Drawings

For a better understanding of the present disclosure, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 shows a flowchart of a method for controlling an operating temperature of a boost pressure device; Figure 2 shows a flowchart of a step of determining an estimate for a target boost pressure; Figure 3 shows a flowchart of the method for controlling the operating temperature of the boost pressure device, the method comprising the step of determining the estimate for the target boost pressure; Figure 4 shows a flowchart of a step of determining a current operating temperature of the boost pressure device and a step of comparing the current operating temperature to an operating temperature limit; Figure 5 shows a flowchart of the method for controlling the operating temperature of the boost pressure device, the method comprising the step of determining the current operating temperature of the boost pressure device and the step of comparing the current operating temperature to the operating temperature limit; Figure 6 shows a flowchart of the method for controlling the operating temperature of the boost pressure device, the method comprising a step of decreasing an operating pressure of the boost pressure device and a step of increasing the pressure of the boost pressure device; Figure 7 shows a graphical example of the method for controlling the operating temperature of the boost pressure device; and Figure 8 shows a system for controlling the operating temperature of the boost pressure device.

Detailed Description

The present invention provides a method and a system of controlling an operating temperature of a boost pressure device, such as a compressor of a turbocharger or a supercharger, for a vehicle, wherein a boost pressure of the boost pressure device is adjusted such that an operating temperature T, for example a gas outlet temperature, of the boost pressure device is substantially equal to an operating temperature limit TLIM* In this way, the boost pressure produced by the boost pressure device is the maximum allowable boost pressure for a given set of operational criteria, such as the reliability of the boost pressure device and/or the performance of the engine. For the sake of brevity in describing the method, it is assumed that the operating temperature limit TLIM is a single, fixed value, but may in practice be variable depending on a number of factors, for example the operating conditions of the vehicle and/or the history and age of the engine, as discussed below.

One of the aims of the system is to operate the boost pressure device at a pressure that is restricted such that the operating temperature is substantially equal to the operating temperature limit TLIM. The method which follows describes a method to achieve this control, which is highly efficient to implement and calibrate, and which maximises the performance of the boost pressure device, the engine and/or the vehicle.

Figure 1 depicts the method of controlling the operating temperature of the boost pressure device for the vehicle. The method comprises step 100 of determining a pressure difference AP between a current operating pressure P of the boost pressure device and a target boost pressure PLIM at which the operating temperature T boost pressure device is substantially equal to the operating temperature limit TLIM. The pressure difference AP is determined by the following equation: = 3L1M The method further comprises step 110 of determining a pressure step size dP, wherein the pressure step size dP is a function of the pressure difference LXP and a predetermined number of steps N. The pressure step size dP is determined by the following equation: The method further comprises step 120 of successively adjusting the operating pressure F of the boost pressure device by the pressure step size dP until the operating temperature T of the boost pressure device is substantially equal to the operating temperature limit TLIM, which may be expressed as: T7 The operating pressure P, of the boost pressure device may be adjusted by varying the mass flow through the device, for example by adjusting a bypass valve in a passage that bypasses the boost pressure device. For example, a bypass passage may be provided around a turbine of a turbocharger and a fraction of the flow through the bypass passage may be adjusted to vary the operating pressure P. Alternatively, in the case of a supercharger, the power delivered to a compressor of the supercharger may be varied to regulate the operational speed to adjust the operating pressure P. In this manner, the current operating temperature T of the boost pressure device is adjusted iteratively to a value substantially equal to the operating temperature limit TLIM in a number of steps approximated by the predetermined number of steps N. The predetermined number of steps N may relate to a desired number of calculations performed by a control device 1, as shown in figure 8. This is advantageous as the method according to the present invention may be implemented using a real-time, embedded controller for example. It is desirable, therefore, that a solution is found within a predetermined number of steps using the minimum required computing resources of the control device 1.

The method may further comprise step 130, as shown in figure 2, which involves determining an estimate for the target boost pressure PLIM at which the boost pressure device operates at the operating temperature limit TLIM. It would be desirable to determine the estimate for the target boost pressure PUM based upon an efficiency 9UM of the boost pressure device at the target boost pressure PLIM. The problem arises, however, in that the efficiency flLIM of the boast pressure device at the target boost pressure PLIM is itself a function of the target boost pressure PLIM and the mass flow rate through the device. The mass flow rate is also a function of the target boost pressure PLIM, This results in an equation with two unknown variables and hence the solution for the target boost pressure PLIM is difficult to obtain.

S

However, the estimate for the target boost pressure PuM may be determined using a current efficiency lix at the current operating pressure P, instead, wherein the current efficiency lx of the boost pressure device may be readily determined from a predetermined boost pressure-mass air flow characteristic of the boost pressure device for a given set of ambient and engine operating conditions. Such data is commonly available in the form of characteristic maps that plot contours of isentropic efficiencies and operational speeds against air mass flow rate and pressure ratios. For example, the estimate for the target boost pressure PuM may be a function of: an inlet pressure PIN; the current efficiency r at the current operating pressure P; the operating temperature limit TLIM; a gas inlet temperature TIN of the boost pressure device; and the ratio of the specific heat of air y. The target boost pressure F'LIM may be calculated using the following equation: LJM = 1N ( (TUM/ -i) + Where multiple solutions are possible for the target boost pressure PLIM, the highest of the solutions is used. Step 130 may be incorporated into the method as shown in figure 3.

The method may further comprise step 140 of determining the current operating temperature Tx of the boost pressure device and step 141 of comparing the current operating temperature Tx to the operating temperature limit TLIM' In this way the control device I may be able to determine if current operating temperature Tx is greater than the operating temperature limit TLIM and thus establish if any action should be taken to adjust the current operating pressure Px to reduce the temperature T of the boost pressure device. The current operating temperature T at the operating pressure P may be determined in step 140 by way of the equation below, in which the current operating temperature T of the boost pressure device is a function of: the gas inlet temperature TIN; the current operating pressure P; the current efficiency lix at the current operating pressure Px; the inlet pressure P1 of the boost pressure device; and a ratio of the specific heat of air y. Alternatively, the current operating temperature of the boost pressure device may be determined by one or more temperature sensors.

S

1 7 y-11 T -T li+1i!(xi X-iN /11x. "31N) Figure 4 shows an example flowchart of how the current operating temperature Tx is determined and compared to the operating temperature limit TLIM. If the control device 1 determines that the current operating temperature T is greater than the operating temperature limit TLM, then appropriate action may be taken to reduce the current operating temperature Tx. If control device 1 determines that the current operating temperature Tx is less than the operating temperature limit TLIM, then the boost pressure device can continue to operate at the current operating pressure P,<. Step 141 may be repeated, for example periodically, to check that the operating temperature Tx does not exceed the operating temperature limit TLIM* Figure 5 shows an example of how step 140 and step 141 may be incorporated in to the method of controlling the operating temperature Tx of the boost pressure device.

As discussed above, the method according to the present invention comprises step 110 of determining the pressure step size dP and step 120 of adjusting the operating pressure P, as shown in figure 1, 3 and 5. Further to this, the method may comprise: step 111 of determining a first pressure step size dP1 and step 121 of successively decreasing the operating pressure P, of the boost pressure device by the first pressure step size dP1; and subsequently, step 112 of determining a second pressure step size dP2 and step 122 of successively increasing the operating pressure of the boost pressure device by the second pressure step size dP2. It may be appreciated, however, that the second pressure step size dP2 may be determined at any point in the method before step 122.

Step 121 may comprise determining the first pressure step size dP1 in a similar manner to the pressure step size dP, i.e. the first pressure step size dP1 is a function of the pressure difference AP and a predetermined number of steps NJ1. The first pressure step size dP1 may be determined by the following equation: Al' dP1 = -N1 Step 121 may comprise successively decreasing the operating pressure P< of the boost pressure device by the first pressure step size dP1 until the operating temperature T is less than the operating temperature limit TLIM. Step 121 may further comprise determining the operating temperature T of the boost pressure device after each decrease in the operating pressure Px. The operating temperature T may be determined as outlined above and may then be compared to the operating temperature limit TLIM. If the operating temperature I is greater than the operating temperature limit TL!M, then the operating pressure P of the boost pressure device is again decreased by the first pressure step size dP1. The number of iterations of step 121 is approximated by the predetermined number of steps N1. In this way the number of computations required in order for the operating temperature T of the boost pressure device to reduced below the operating temperature limit TLIM may be selected in accordance with the allocated computational resource. Furthermore, the predetermined number of steps N1 may be selected to ensure that the operating temperature T of the boost pressure device is always decreased to a value less than the operating temperature limit Step 112 may comprise determining the second pressure step size dP2, wherein the second pressure step size dP2 is a function of the first pressure step size dP1 and another predetermined number of steps N2. The first pressure step size dP1 may be determined by the following equation: dP1 "2 In this way, the second pressure step size dP2 may be smaller than the first pressure step size dP1. In fact, the second pressure step size dP2 may be a divisor of the first pressure step size dP1.

Alternatively, step 112 may comprise determining the second pressure step size dP2 in a similar manner to the pressure step size dP, i.e. the second pressure step size dP2 is a function of the pressure difference AP and another predetermined number of steps N3. The second pressure step size dP2 may be determined by the following equation: lAP dP2 = N3 Step 122 may comprise successively increasing the operating pressure Px of the boost pressure device by the second pressure step size dP2 until the operating temperature T is greater than the operating temperature limit TLIM. Step 122 may further comprise determining the operating temperature T of the boost pressure device after each increase in the operating pressure P. The operating temperature T may be determined as outlined above and may then be compared to the operating temperature limit TuM. If the operating temperature T is less than the operating temperature limit TLIM, then the operating pressure Px of the boost pressure device is again increased by the pressure step size dP2. The number of iterations of step 122 is approximated by the predetermined number of steps N2 or N3. In this way the number of computations required in order for the operating temperature T of the boost pressure device to be greater than the operating temperature limit TLIM may be selected in accordance with the allocated computational resource. Furthermore, the predetermined number of steps N2 or N3 may be selected to ensure that the operating temperature I of the boost pressure device is always increased to a value greater than the operating temperature limit TLIM.

In this way, the operating pressure P, is successively decreased by the larger first pressure step size dP1 until the operating temperature T is less than the operating temperature limit TLIM, after which, the operating pressure P is successively increased by the smaller second pressure step size dP2 until the operating temperature T is greater than the operating temperature limit TLIM. The smaller second pressure step size dP2 may be determined by an appropriately predetermined number of steps NJ2 such that the operating temperature T is only just greater than the operating temperature limit TLIM, i.e. the resulting operating pressure P will be such that the operating temperature T is very close to the operating temperature limit TLIM.

Figure 7 depicts a graphical example of the steps taken to adjust the operating pressure P of the boost pressure device such that the current operating temperature T is substantially equal to the operating temperature limit TLIM. In the example shown in figure 7, the boost pressure device is operating at the operating pressure F and the current operating temperature T, An example of the method according to the present invention will now be described, with reference to figure 6 and figure 7, wherein the method comprises: * Step 140 of determining the current operating temperature I of the boost pressure device and step 141 of comparing the current operating temperature Tx to the operating temperature limit TuM. In this way the control device 1 determines that the current operating temperature T is greater than the operating temperature limit TLIM and thus action should be taken to adjust the current operating pressure P, to reduce the operating temperature Tx of the boost pressure device; * Step 130 of determining the estimate for the target boost pressure PLIM at which the boost pressure device operates at the operating temperature limit TIJM; * Step 100 of determining the pressure difference A? between the current operating pressure P of the boost pressure device and the target boost pressure FIlM at which the operating temperature T boost pressure device is substantially equal to the operating temperature limit TLIM; * Step 111 of determining the first pressure step size dP1; and * Successive steps 121 of decreasing the operating pressure P of the boost pressure device by the first pressure step size dP1 and steps 141 of comparing the current operating temperature T to the operating temperature limit TLIM after each first pressure step size dP1 decrease.

In the example shown in figure 7, the predetermined number of pressure steps N1 has been set to 4. It may be appreciated, however, that predetermined number of pressure steps N1 may be set to any appropriate value. As the initially calculated estimate for the target boost pressure FIlM is approximated, the actual number of steps required may be greater or less than the predetermined number of pressure steps N1. Step 121 is repeated until the current operating temperature T is less than the operating temperature limit TuM.

The method further comprises: * Step 112 of determining the second pressure step size dF2; and * Successive steps 122 of increasing the operating pressure P, of the boost pressure device by the second pressure step size dP2 and steps 141 of comparing the current operating temperature T to the operating temperature limit TLIM after each second pressure step size dP2 increase.

In the example shown in figure 7 the predetermined number of pressure steps N2 has been set to 2. It may be appreciated, however, that predetermined number of pressure steps N2 may be set to any appropriate value. As the initially calculated estimate for the target boost pressure FIlM is approximated, the actual number of steps required may be greater or less than the predetermined number of pressure steps N2. Step 122 is repeated until the current operating temperature T is greater than the operating temperature limit TLIM Since the second pressure step size dP2 is relatively small, for example with respect to dP1, the current operating temperature is substantially equal to the operating temperature limit TLIM of the boost pressure device. However, in an alternative example, to ensure that the operating temperature T is less than the operating temperature limit TuM, the boost pressure device may be operated at the previous operating pressure P> prior to the last step 122.

The predetermined number of steps N N1, N2, N3 and/or the operating temperature limit TLIM may be selected in accordance with the performance requirements of the boost pressure device and/or the vehicle. The predetermined number of steps NJ, N2, N3 may be selected such that the operating pressure P, is adjusted in a smaller number of steps if a rapid adjustment is required, or alternatively, in a larger number of steps if a more accurate solution is required. For example! if the predetermined number of pressure steps N2 was set to 20, the method would converge on a more accurate solution of the operating temperature T,, but would require more computational resource to reach the solution. Similarly, the operating temperature limit TLIM may be selected at a higher level if the expected lifetime of the boost pressure device 1 is short. In this manner, the boost pressure of the boost pressure device may be maximised without significant regard to the reliability of the boost pressure device over an extended time period.

The operating temperature limit TUM may be selected in accordance with an age factor of the boost pressure device. For example, operating temperature limit TLIM may be set at a lower level in those boost pressure devices that have completed a higher number of operational cycles than in those boost pressure devices that have completed a lower number of operational cycles. The age factor may be determined at appropriate service intervals and may be selected in accordance with the perceived wear rate of the boost pressure device.

The operating temperature limit TLIM may be selected accordance with an ambient pressure of the boost pressure device. For example, the operating temperature limit Iu,, may be set at a higher level when installed to a vehicle that operates at a higher altitude. In this manner, the boost pressure device 1 is able to produce higher boost pressures in order to compensate for the reduced ambient pressure at those higher altitudea The operating temperature limit TLIM may be set at fixed values and/or may be variable dependent upon the operational requirements of the boost pressure device and/or the vehicle. For example, the age factor may be set to adjust automatically as the number of operational cycles of the boost pressure device increases. In another example, the control device I may be configured to detect the ambient conditions surrounding the vehicle. The control device may be configured to determine atmospheric pressure and/or temperature amongst other variables. The operating temperature limit TLIM may be varied in accordance with the changing ambient conditions such that the reliability and/or the performance of the boost pressure device is maximised in accordance with the ambient conditions. Whether or not the operating temperature limit TLIM control is active may be dependent on ambient conditions and engine performance requirements, but for use of vehicles at higher altitudes and higher ambient temperatures, the operating temperature limit TLIM will be applicable for a significant proportion of engine operation.

Figure 8 shows a system 10 according to the present invention. The system 10 comprises the control device 1 and a system pressure regulator 3. The control device I is configured to determine the pressure difference AP between the current operating pressure P, of the boost pressure device and a target boost pressure PLIM at which the boost pressure device operates at an operating temperature limit TUM. The control device is further configured to determine a pressure step size dP, wherein the pressure step size dP is a function of the pressure difference A? and a predetermined number of pressure steps N1. The control device 1 is further configured to provide a signal to the system pressure regulator 3, the system pressure regulator 3 being configured to adjust the pressure of the boost pressure device and the signal being configured to adjust the current operating pressure in the predetermined number of pressure steps N1 such that the operating temperature T of the boost pressure device is substantially equal to the operating temperature limit TLIM.

The system may further comprise one or more temperature sensors configured to measure the temperature, for example the gas inlet and/or gas outlet temperature, of the boost pressure device and/or one or more pressure sensors configured to measure the pressure for example the inlet and/or the outlet pressure, of the boost pressure device and/or an ambient pressure. Furthermore, the control device 1 may be a real-time embedded controller.

Claims

Claims 1. A method of controlling an operating temperature of a boost pressure device for a vehicle, the method comprising: S determining a pressure difference between a current operating pressure of the boost pressure device and a target boost pressure at which the boost pressure device operates at an operating temperature limit; determining a pressure step size, wherein the pressure step size is a function of the pressure difference and a predetermined number of pressure steps; and successively adjusting the current operating pressure by the pressure step size until the operating temperature of the boost pressure device is substantially equal to the operating temperature limit.
2. A method according to claim 1 the method further comprising: determining an estimate for the target boost pressure at which the boost pressure device operates at the operating temperature limit.
3. A method according to claim 2, wherein the estimate for the target boost pressure is based upon the efficiency of the boost pressure device at the current operating pressure.
4. A method according to any of claims 1 to 3, wherein adjusting the operating pressure of the boost pressure device comprises: successively decreasing the current operating pressure of the boost pressure device by a first pressure step size; and subsequently, successively increasing the current operating pressure of the boost pressure device by a second pressure step size.
5. A method according to claim 4, wherein the current operating pressure of the boost pressure device is successively decreased by the first pressure step size until the operating temperature of the boost pressure device is less than the operating temperature limit.
6. A method according to claim 4 or 5, wherein the operating pressure of the boost pressure device is successively increased by the second pressure step size until the operating temperature of the boost pressure device is greater than the operating temperature limit.
7. A method according to any of claims 4 to 6, wherein the second pressure step size is smaller than the first pressure step size.
8. A method according to any of claims 4 to 7, wherein the second pressure step size is a divisor of the first pressure step size.
9. A method according to any of the preceding claims, the method further comprising: determining a current operating temperature of the boost pressure device; and comparing the current operating temperature to the operating temperature limit.
10. A method according to claim 9, the method further comprising: repeatedly adjusting the current operating temperature until the current operating temperature is less than or more than the operating temperature limit.
11. A method according to any of the preceding claims, wherein the predetermined number of pressure steps is selected according to the performance requirements of the boost pressure device and/or the vehicle.
12. A method according to any of the preceding claims, wherein the operating temperature limit is a function of the performance requirements of the boost pressure device and/or the vehicle.
13. A method according to any of the preceding claims, wherein the predetermined number of pressure steps relates to an optimal number of computations.
14. A method according to any of the preceding claims, wherein the operating temperature limit is determined in accordance with an ambient pressure.
15. A method according to any of the preceding claims, wherein the operating temperature limit is determined in accordance with an age factor of the boost pressure device and/or the vehicle.
16. A method according to any of the preceding claims, wherein the operating temperature Umit is variable or fixed.
17. A method according to any of the preceding claims, wherein the operating temperature is a gas outlet temperature of the boost pressure device.
18. A system of controlling an operating temperature of a boost pressure device for a vehicle, the system comprising: one or more control devices configured to: detemiine a pressure difference between a current operating pressure of the boost pressure device and a target boost pressure at which the boost pressure device operates at an operating temperature limit; determine a pressure step size, wherein the pressure step size is a function of the pressure difference and a predetermined number of pressure steps; and provide a signal to adjust the pressure of the boost pressure device, the signal being configured to adjust the current operating pressure in a number of pressure steps such that the operating temperature of the boost pressure device is substantially equal to the operating temperature limit.
19. A system according to claim 18, the system further comprising: one or more temperature sensors configured to measure the temperature of the boost pressure device; and/or one or more pressure sensors configured to measure the pressure of the boost pressure device and/or an ambient pressure.
20. A system according to any of claims 18 or 19, wherein the control device is a real-time embedded controller.
21. A method according to any of claims 1 to 17 or a system according to any of claims 18 to 20, wherein the boost pressure device is a turbocharger or a supercharger.
22. Software which when executed by a computing apparatus causes the computing apparatus to perform the method of any of claims ito 17.
23. A vehicle or engine comprising the system for controlling an operating temperature of a boost pressure device according to any of claims 18 to 20.
24. A system as described herein, with reference to and as shown in the accompanying drawings.
25. A method as described herein, with reference to and as shown in the accompanying drawings.