Power supply device for vehicle

Abstract

To provide a power supply device for a vehicle that can increase opportunities to use electric devices with power from an onboard battery while being externally charged, thereby improving convenience.SOLUTION: An ECU permits DC-AC power supply, in which a DC-AC converter converts power from a high-voltage battery into AC power for supply, when the high-voltage battery capacity defined as the state of charge or dischargeable power of the high-voltage battery is equal to or greater than a predetermined power supply permission threshold (YES in Step S7) (Step S8). When the high-voltage battery is not being externally charged (NO in Step S4), the ECU sets the power supply permission threshold to a first threshold (Step S6); when the high-voltage battery is being externally charged (YES in Step S4), the ECU sets the power supply permission threshold to a second threshold that is lower than the first threshold (Step S5).SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a vehicle power supply device.

Background Art

[0002] Patent Document 1 discloses a vehicle power supply device including an ECU that calculates an allowable power consumption that can be supplied from a high-voltage battery to an accessory outlet via an inverter. In the vehicle power supply device described in Patent Document 1, when the SOC of the high-voltage battery exceeds a predetermined value, the ECU maintains the allowable power consumption at a predetermined high power, and when the SOC is below the predetermined value, the allowable power consumption is gradually decreased as the SOC decreases, and the operation of the inverter is permitted so that power is supplied to an electrical product with the calculated allowable power consumption as an upper limit.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the case of the device described in Patent Document 1, when the SOC is below a predetermined value, the allowable power consumption is gradually decreased as the SOC decreases. Therefore, even during external charging using external power, the allowable power consumption is set low until the SOC is sufficiently recovered, and there are cases where power cannot be supplied to electrical equipment.

[0005] An object of the present invention is to provide a vehicle power supply device that can increase the opportunity to use electrical equipment with the power of an in-vehicle battery during external charging and improve convenience.

Means for Solving the Problems

[0006] The vehicle power supply device according to the present invention is capable of external charging from outside the vehicle while the vehicle is stopped, and includes a battery that supplies power to at least a motor for driving, and a DC-AC converter that converts the power of the battery into AC power. The vehicle power supply device is characterized in that it includes a control unit that permits DC-AC power supply in which the power of the battery is converted into AC power by the DC-AC converter and supplied when the state of charge of the battery or the battery capacity, which is the dischargeable power, is equal to or greater than a predetermined power supply permission threshold value. When the battery is not being externally charged, the control unit sets the power supply permission threshold value to a first threshold value, and when the battery is being externally charged, the control unit sets the power supply permission threshold value to a second threshold value smaller than the first threshold value.

Effects of the Invention

[0007] The present invention can provide a vehicle power supply device that can increase the opportunities to use electrical equipment with the power of the in-vehicle battery during external charging and improve convenience.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0009] A vehicle power supply device according to an embodiment of the present invention is capable of external charging from outside the vehicle while the vehicle is stopped, and includes a battery that supplies power to at least a motor for running, and a DC-AC converter that converts the power of the battery into AC power. The vehicle power supply device is characterized in that it includes a control unit that permits DC-AC power supply in which the power of the battery is converted into AC power by the DC-AC converter and supplied when the state of charge of the battery or the battery capacity, which is the dischargeable power, is equal to or greater than a predetermined power supply permission threshold value. When the battery is not being externally charged, the control unit sets the power supply permission threshold value to a first threshold value, and when the battery is being externally charged, the control unit sets the power supply permission threshold value to a second threshold value smaller than the first threshold value. Thereby, the vehicle power supply device according to an embodiment of the present invention can increase the opportunities to use electrical equipment with the power of the in-vehicle battery during external charging, and can improve convenience.

Example

[0010] Hereinafter, a vehicle including a vehicle power supply device according to an embodiment of the present invention will be described with reference to the drawings.

[0011] As shown in FIG. 1, the vehicle 1 includes a motor 17 for running and a high-voltage battery 2 that supplies power to at least the motor 17 for running. The high-voltage battery 2 is an in-vehicle battery and constitutes the battery in the present invention.

[0012] The motor 17 is connected to the high-voltage battery 2 via a high-voltage line 11. The motor 17 has a function as an electric motor driven by the power supplied from the high-voltage battery 2 and a function as a generator that generates electricity by the reverse driving force input from the driving wheels. The power generated by the motor 17 is charged into the high-voltage battery 2.

[0013] The high-voltage battery 2 is constituted by, for example, a lithium-ion battery. Charge lines 14 and 15 are connected to the high-voltage battery 2. The high-voltage battery 2 is configured to be capable of external charging from the external charging lines 14 and 15 outside the vehicle while the vehicle is stopped. The high-voltage battery 2 mainly supplies power to the motor 17.

[0014] In the middle of the charging line 15, a charger 8 is provided. Also, a normal charging line 23, which is vehicle external equipment of an AC power source, is connected to the charging line 15. The charger 8 is mounted on the vehicle 1 and converts the AC supplied from the normal charging line 23 into DC. The charger 8 performs normal charging from the normal charging line 23 to the high-voltage battery 2.

[0015] A rapid charging line 22, which is vehicle external equipment of a DC power source, is connected to the charging line 14. A rapid charger 21 is connected to the rapid charging line 22. The rapid charger 21 performs rapid charging from the rapid charging line 22 to the high-voltage battery 2.

[0016] The vehicle 1 is equipped with a DCDC converter 5. The DCDC converter 5 is connected to the high-voltage battery 2 via the high-voltage line 11. It steps down the voltage of the high-voltage battery 2 to a predetermined auxiliary system voltage (for example, DC 12V) and supplies power to the auxiliary system. A lead battery (denoted as Pb battery in the figure) 6 and an ECU 7 are connected to the DCDC converter 5 via a power supply line 13. The lead battery 6 outputs DC 12V, and auxiliary systems such as the ECU 7 operate with DC 12V.

[0017] In this way, by converting the voltage of the high-voltage battery 2 to the auxiliary system voltage by the DCDC converter 5, it can be used for the operation of auxiliary systems such as the ECU 7. The ECU 7 constitutes the auxiliary system and the control unit in the present invention.

[0018] The vehicle 1 is equipped with a DCAC converter 3. The DCAC converter 3 is connected to the high-voltage battery 2 via the high-voltage line 11. The DCAC converter 3 converts the power of the high-voltage battery 2 into AC power (for example, AC 100V). A vehicle interior power outlet 4 is connected to the DCAC converter 3 via a power supply line 12.

[0019] The in-vehicle power outlet 4 supplies power to electrical devices such as mobile phones (not shown). Therefore, the occupant can use and charge the electrical devices connected to the in-vehicle power outlet 4. Converting the power of the high-voltage battery 2 into AC power by the DC-AC converter 3 and supplying power to the electrical devices is called DC-AC power supply.

[0020] The ECU 7 is composed of a computer unit including a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory for storing backup data and the like, an input port, and an output port.

[0021] In the ROM of the computer unit, a program for causing the computer unit to function as the ECU 7 is stored together with various constants and various maps. That is, by the CPU executing the program stored in the ROM using the RAM as a working area, the computer unit functions as the ECU 7 in the present embodiment.

[0022] An ignition switch (denoted as IG in the figure) 18 and a seating sensor 19 are connected to the ECU 7. The ignition switch 18 switches the power supply of the vehicle 1 on or off by being operated to the on position or the off position by the driver. The seating sensor 19 detects whether or not an occupant is seated on a seat (not shown). That is, the seating sensor 19 detects whether or not there is an occupant in the vehicle interior.

[0023] The ECU 7 is capable of performing DC-AC power supply in which the power of the high-voltage battery 2 is converted into AC power by the DC-AC converter 3 and supplied. The ECU 7 determines whether to permit or prohibit DC-AC power supply. The ECU 7 permits DC-AC power supply when the state of charge (SOC) of the high-voltage battery 2 or the battery capacity, which is the dischargeable power (Wout), is equal to or higher than a predetermined DC-AC power supply permission threshold value.

[0024] When the high-voltage battery 2 is not being externally charged, the ECU 7 sets the power supply permission threshold to the first threshold, and when the high-voltage battery 2 is being externally charged, the ECU 7 sets the power supply permission threshold to a second threshold smaller than the first threshold. That is, the DC-AC power supply permission threshold during external charging is set to a value lower than the DC-AC power supply permission threshold during non-external charging.

[0025] The first threshold is set to the battery capacity required to ensure driving performance (for example, the minimum speed of 50 km / h on a highway). Also, it is preferable that a margin is ensured for the first threshold.

[0026] The second threshold is set to the battery capacity required for the operation of the DCDC converter 5 or the battery capacity required to cover the power consumed by auxiliary systems such as the ECU 7. Also, it is preferable that a margin is ensured for the second threshold.

[0027] During external charging of the high-voltage battery 2, a margin is created in the battery capacity of the high-voltage battery 2, and it is easier to maintain the functions of auxiliary systems such as the ECU 7. For this reason, the power consumption by DC-AC power supply can be covered, the implementable range of DC-AC power supply can be expanded, and the opportunities for DC-AC power supply can be increased.

[0028] The first threshold is set to be larger than the value that can maintain a predetermined driving performance when driving by the motor 17. The predetermined driving performance is, for example, the performance that enables constant-speed driving at a predetermined vehicle speed (for example, 100 km / h).

[0029] That is, during driving, since it is not externally charging, DC-AC power supply is permitted when the battery capacity is equal to or greater than the battery capacity capable of maintaining a predetermined driving performance. Here, the power for DC-AC power supply and the power used by the motor 17 for driving are supplied from the high-voltage battery 2. Also, it is desirable to prioritize driving performance over DC-AC power supply during driving. During driving, that is, during non-external charging, by setting the DC-AC power supply permission threshold to a value obtained by adding a margin to the value at which a certain driving performance can no longer be maintained, DC-AC power supply is prohibited when the battery capacity is less than the DC-AC power supply permission threshold, and more power can be allocated to driving the motor 17.

[0030] The second threshold is set to be larger than the value at which the DCDC converter 5 can operate. By doing so, during external charging of the high-voltage battery 2, DC-AC power supply is permitted when the high-voltage battery 2 is in a state where the DCDC converter 5 can operate.

[0031] Also, the second threshold is set to be larger than the value capable of covering the power consumption of the auxiliary system. During external charging and when electrical components such as an air conditioner (not shown) are on, the DC-AC power supply permission threshold is set to a value obtained by adding the AC drive power to the value capable of maintaining the operation of the DCDC converter 5, and it is preferable to prioritize the operation of electrical components of the auxiliary system such as the air conditioner. The electrical components of the auxiliary system are not limited to the air conditioner and may be audio equipment, car navigation, etc.

[0032] By doing so, in a situation where the actual power consumption (power consumption for maintaining the operation of the DCDC converter 5 + power consumption for DC-AC power supply + power consumption of the air conditioner) exceeds the available power (power from external charging + power of the high-voltage battery 2), the power supplied to the air conditioner etc. can be the power excluding the power for DC-AC power supply (power capable of maintaining the operation of the DCDC converter 5 + power consumption of the air conditioner), so the operable range of the air conditioner can be expanded, and maximum air conditioning performance can be ensured for passengers such as infants who have a high need for air conditioning.

[0033] During external charging, when an occupant in the vehicle interior uses or charges an electrical device, by changing the DC-AC power supply permission threshold value to a value obtained by adding a margin to a value that enables the DCDC converter 5 to be maintained in operation, it is possible to use the power from the charger 8 side (external power from outside the vehicle, grid power) without waiting for the charging state or the recovery of the dischargeable power, and the convenience can be improved. By setting a value at which the DCDC converter 5 can operate, it is possible to ensure at least the power supplied to the auxiliary machine system such as the ECU 7 that requires the auxiliary machine system voltage.

[0034] The second threshold value in the case of external charging from a DC power supply is set to be smaller than the second threshold value in the case of external charging from an AC power supply. There are two types of external charging: rapid charging by DC and normal charging by AC. During rapid charging, it is preferable to further lower the DC-AC power supply permission threshold value compared to normal charging. During rapid charging, since the charging state of the high-voltage battery 2 is restored quickly, the margin amount for maintaining the operation of the DCDC converter 5 is reduced for the DC-AC power supply permission threshold value.

[0035] Rapid charging, which supplies more power than normal charging, creates a margin in the battery capacity of the high-voltage battery 2, and it is easier to maintain the functions of the ECU 7 and the like. Therefore, it is possible to cover the power consumption by DC-AC power supply, expand the feasible range of DC-AC power supply, and increase the opportunities for DC-AC power supply.

[0036] During rapid charging, the power supply from outside the vehicle is larger compared to normal charging. The margin amount is set to ensure a level at which the operation of the DCDC converter 5 can be maintained when the external supply power during external charging instantaneously drops below the power by DC-AC power supply. Therefore, during rapid charging when the power supply from outside the vehicle is large, the margin amount can be made smaller compared to normal charging, and DC-AC power supply can be started from a lower DC-AC power supply permission threshold value, improving the convenience.

[0037] Here, when there is no occupant in the vehicle interior, even if external charging is in progress, there is no need to prioritize DC-AC power supply, and the priority of using electrical equipment by DC-AC power supply is low.

[0038] Therefore, when there is no occupant in the vehicle, the ECU 7 makes the second threshold equal to the first threshold. Specifically, when it is determined that there is no occupant in the vehicle interior, such as when the ignition switch 18 is off or the seating sensor 19 is off, the ECU 7 makes the DC-AC power supply permission threshold equal to that during driving (when not externally charging), even if external charging is in progress. By doing so, DC-AC power supply is prohibited until the battery capacity capable of maintaining driving is restored, and charging of the high-voltage battery 2 is prioritized, so that charging can be completed earlier.

[0039] Referring to FIG. 2, the flow of the first DC-AC power supply permission determination operation will be described. In the first DC-AC power supply permission determination operation, the power supply permission threshold differs depending on whether the high-voltage battery 2 is not externally charging or is externally charging. This operation is repeatedly executed by the ECU 7 at a predetermined time interval.

[0040] The ECU 7 acquires the battery capacity C (step S1).

[0041] The ECU 7 determines whether to perform DC-AC power supply (step S2).

[0042] When the ECU 7 does not perform DC-AC power supply (NO in step S2), it turns off the DC-AC power supply (step S3) and executes step S2 again.

[0043] When the ECU 7 performs DC-AC power supply (YES in step S2), it determines whether external charging is in progress (step S4).

[0044] When the ECU 7 is externally charging (YES in step S4), it sets the DC-AC power supply permission threshold C' to Ca (step S5). Ca is the threshold for external charging (marked as "during charging" in the figure).

[0045] When it is not during external charging (NO in step S4), the ECU 7 sets the DC-AC power supply permission threshold C' to Cb (step S6). Cb is a threshold for when not in external charging (denoted as "when not charging" in the figure). The values are set such that Ca < Cb. Cb corresponds to the first threshold in the present invention, and Ca corresponds to the second threshold in the present invention.

[0046] Subsequent to steps S5 and S6, the ECU 7 determines whether the battery capacity C is greater than or equal to the DC-AC power supply permission threshold C' (step S7).

[0047] When the battery capacity C is greater than or equal to the DC-AC power supply permission threshold C' (YES in step S7), the ECU 7 permits DC-AC power supply (step S8) and ends the current operation.

[0048] When the battery capacity C is less than the DC-AC power supply permission threshold C' (NO in step S7), the ECU 7 prohibits DC-AC power supply (step S9) and ends the current operation.

[0049] Referring to FIG. 3, the flow of the second DC-AC power supply permission determination operation will be described. The second DC-AC power supply permission determination operation differs from the first DC-AC power supply permission determination operation in that when the high-voltage battery 2 is being externally charged, the power supply permission threshold is varied according to whether it is normal charging or rapid charging. This operation is repeatedly executed by the ECU 7 at a predetermined time interval.

[0050] The ECU 7 acquires the battery capacity C (step S11).

[0051] The ECU 7 determines whether to perform DC-AC power supply (step S12).

[0052] When the ECU 7 does not perform DC-AC power supply (NO in step S12), it turns off the DC-AC power supply (step S13) and executes step S12 again.

[0053] When the ECU 7 performs DCAC power supply (YES in step S12), it determines whether it is under external charging (step S14).

[0054] When the ECU 7 is under external charging (YES in step S14), it determines whether it is under rapid charging (step S15).

[0055] When the ECU 7 is under rapid charging (YES in step S15), it sets the DCAC power supply permission threshold C' to Cc (step S16). Cc is the threshold for external charging and rapid charging.

[0056] When the ECU 7 is not under rapid charging (NO in step S15), it sets the DCAC power supply permission threshold C' to Cd (step S17). Cd is the threshold for external charging and normal charging. Each value is set so that Cc < Cd.

[0057] When the ECU 7 is not under external charging (NO in step S14), it sets the DCAC power supply permission threshold C' to Cb (step S18). Cb is the threshold for non-external charging (marked as non-charging in the figure). Each value is set so that Cc and Cd are smaller than Cb. Cb corresponds to the first threshold in the present invention, and Cc and Cd correspond to the second threshold in the present invention.

[0058] After steps S16, S17, and S18, the ECU 7 determines whether the battery capacity C is equal to or greater than the DCAC power supply permission threshold C' (step S19).

[0059] When the battery capacity C is equal to or greater than the DCAC power supply permission threshold C' (YES in step S19), the ECU 7 permits DCAC power supply (step S20) and ends the current operation.

[0060] When the battery capacity C is less than the DCAC power supply permission threshold C' (NO in step S19), the ECU 7 prohibits DCAC power supply (step S21) and ends the current operation.

[0061] Referring to FIG. 4, the flow of the third DCAC power supply permission determination operation will be described. The third DCAC power supply permission determination operation is different from the first DCAC power supply permission determination operation in that the power supply permission threshold is varied according not only to whether external charging is in progress but also to whether there is an occupant in the vehicle. This operation is repeatedly executed by the ECU 7 at predetermined time intervals.

[0062] The ECU 7 acquires the battery capacity C (step S31).

[0063] The ECU 7 determines whether to perform DCAC power supply (step S32).

[0064] If the ECU 7 does not perform DCAC power supply (NO in step S32), it turns off the DCAC power supply (step S33) and executes step S32 again.

[0065] If the ECU 7 performs DCAC power supply (YES in step S32), it determines whether external charging is in progress (step S34).

[0066] If external charging is in progress (YES in step S34), the ECU 7 determines whether there is an occupant in the vehicle interior (step S35).

[0067] If there is an occupant in the vehicle interior (YES in step S35), the ECU 7 sets the DCAC power supply permission threshold C' to Ca (step S36). Ca is the threshold for external charging (denoted as "during charging" in the figure).

[0068] If there is no occupant in the vehicle interior (NO in step S35), the ECU 7 sets the DCAC power supply permission threshold C' to Cb (step S37). Cb is the threshold for non-external charging (denoted as "not during charging" in the figure). The values are set such that Ca < Cb. Cb corresponds to the first threshold in the present invention, and Ca corresponds to the second threshold in the present invention.

[0069] Following steps S36 and S37, the ECU7 determines whether the battery capacity C is equal to or greater than the DCAC power supply permission threshold C' (step S38).

[0070] When the battery capacity C is equal to or greater than the DCAC power supply permission threshold C' (YES in step S38), the ECU7 permits DCAC power supply (step S39) and ends the current operation.

[0071] When the battery capacity C is less than the DCAC power supply permission threshold C' (NO in step S38), the ECU7 prohibits DCAC power supply (step S40) and ends the current operation.

[0072] As described above, in the vehicle power supply device according to this embodiment, the ECU7 permits DCAC power supply, in which the DCAC converter 3 converts the power of the high-voltage battery 2 into AC power for power supply, when the state of charge of the high-voltage battery 2 or the high-voltage battery capacity, which is the dischargeable power, is equal to or greater than a predetermined power supply permission threshold. Further, when the high-voltage battery 2 is not being externally charged, the ECU7 sets the power supply permission threshold to the first threshold, and when the high-voltage battery 2 is being externally charged, the ECU7 sets the power supply permission threshold to a second threshold smaller than the first threshold.

[0073] Thereby, when the high-voltage battery 2 is being externally charged, the power supply permission threshold at which DCAC power supply is permitted is made smaller than when it is not being externally charged. As a result, it is possible to increase the opportunities to use electrical equipment with the power of the high-voltage battery 2 as an in-vehicle battery during external charging, and the convenience can be improved.

[0074] Also, in the vehicle power supply device according to this embodiment, the first threshold is greater than a value that can maintain a predetermined driving performance during driving by the motor 17.

[0075] Thereby, it is possible to prevent the high-voltage battery capacity from decreasing (power failure) to a state where a predetermined driving performance cannot be maintained due to the use of electrical equipment by DCAC power supply during non-external charging.

[0076] In addition, the vehicle power supply device according to this embodiment includes a DCDC converter 5 that steps down the voltage of the high-voltage battery 2 to a predetermined auxiliary system voltage and supplies power to the auxiliary system. And the second threshold value is larger than a value at which the DCDC converter 5 can operate.

[0077] Thereby, during external charging of the high-voltage battery 2, while ensuring the operation of the DCDC converter 5, DC-AC power supply to electrical equipment can be performed.

[0078] Also, in the vehicle power supply device according to this embodiment, the second threshold value is larger than a value that can cover the power consumption of the auxiliary system.

[0079] Thereby, during external charging of the high-voltage battery 2, while ensuring the operation of the auxiliary system, DC-AC power supply to electrical equipment can be performed.

[0080] Also, in the vehicle power supply device according to this embodiment, the high-voltage battery 2 can be externally charged from a DC power source or an AC power source outside the vehicle. And the second threshold value when performing external charging from a DC power source is smaller than the second threshold value when performing external charging from an AC power source.

[0081] Here, rapid charging by a DC power source can supply more power from an external charging facility than normal charging by an AC power source. The margin amount is set to ensure the driving maintenance level of the DCDC converter 5 when the power amount from the outside momentarily falls below the in-vehicle power supply. Therefore, during rapid charging when more power can be taken from outside the vehicle, the margin amount can be made smaller. So, during rapid charging by a DC power source, DC-AC power supply can be started from a lower second threshold value, and the opportunity to use electrical equipment with the power of the high-voltage battery 2 as an in-vehicle battery during external charging can be increased.

[0082] Also, in the vehicle power supply device according to this embodiment, when there is no occupant in the vehicle, the ECU 7 makes the second threshold value equal to the first threshold value.

[0083] Accordingly, when there is no occupant in the vehicle, since the priority of using electrical equipment by DCAC power supply is low, by setting the second threshold value to a large value equal to the first threshold value, the charging of the high-voltage battery 2 can be performed faster.

[0084] Although embodiments of the present invention have been disclosed, it is obvious that those skilled in the art can make changes without departing from the scope of the present invention. It is intended that all such modifications and equivalents be included in the following claims.

Explanation of Signs

[0085] 1 Vehicle 2 High-voltage battery (battery) 3 DCAC converter 5 DCDC converter 7 ECU (control unit, accessory system) 17 Motor

Claims

1. A vehicle power supply device that enables external charging from outside the vehicle while parked and includes a battery that supplies power to at least a motor for driving, and a DC-AC converter that converts the power of the battery into AC power, and is characterized in that: a control unit that permits DC-AC power supply, which converts the power of the battery into AC power by the DC-AC converter and supplies power, when the state of charge of the battery or the battery capacity, which is the dischargeable power, is equal to or greater than a predetermined power supply permission threshold value; the control unit: when the battery is not being externally charged, sets the power supply permission threshold value to a first threshold value; when the battery is being externally charged, sets the power supply permission threshold value to a second threshold value smaller than the first threshold value. The vehicle power supply device is characterized by this.

2. The vehicle power supply device according to claim 1, wherein the first threshold value is greater than a value that can maintain a predetermined driving performance during driving by the motor.

3. The vehicle power supply device according to claim 1 or claim 2, further comprising a DC-DC converter that steps down the voltage of the battery to a predetermined auxiliary system voltage and supplies power to the auxiliary system, wherein the second threshold value is greater than a value at which the DC-DC converter can operate.

4. The vehicle power supply device according to claim 3, wherein the second threshold value is greater than a value that can cover the power consumption of the auxiliary system.

5. The battery can be externally charged from a DC power source or an AC power source outside the vehicle, and the second threshold value when externally charging from the DC power source is smaller than the second threshold value when externally charging from the AC power source. The vehicle power supply device according to claim 1 is characterized by this.

6. The vehicle power supply device according to claim 1, wherein the control unit makes the second threshold value equal to the first threshold value when there is no occupant in the vehicle.

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