Reservoir and tank equipped with a self-regulating heating element

1. A reservoir to hold a quantity of fluid within a tank, said reservoir comprising:

a first resistive element to electrically heat a first part of a tank, said first resistive element positioned outside said reservoir;

a second element to electrically heat a second part of said tank, said second element positioned inside said reservoir, said second element having a positive temperature coefficient; and

a third resistive element to electrically heat said second part of said tank, said third resistive element positioned inside said reservoir,

said second element and said first resistive element forming a parallel circuit, and said third resistive element being connected in series with said parallel circuit,

wherein said reservoir is mounted inside said tank,

wherein at a first time corresponding to a start the heating, the second element has a first resistance so as to dissipate a first power within the reservoir, and

wherein at a later second time the second element has a second resistance so as to dissipate a second power within the reservoir, the second power being lower than the first power so that a total power dissipated in the tank is lower at the second time than at the first time.

2. The reservoir of claim 1 , wherein said second element is positioned on an accessory of said tank.

3. The reservoir of claim 2 , wherein said accessory is a pump.

4. The reservoir of claim 1 , wherein said second element is overmolded with a thermoplastic material.

5. A vehicular fluid tank, comprising:

a reservoir including:

a first resistive element to electrically heat a first part of said tank, said first resistive element positioned outside said reservoir,

a second element to electrically heat a second part of said tank, said second element positioned inside said reservoir, said second element having a positive temperature coefficient, and

a third resistive element to electrically heat said second part of said tank, said third resistive element positioned inside said reservoir,

said second element and said first resistive element forming a parallel circuit, and said third resistive element being connected in series with said parallel circuit,

wherein said reservoir is mounted inside said tank,

wherein at a first time corresponding to a start of the heating, the second element has a first resistance so as to dissipate a first power within the reservoir, and

wherein at a later second time the second element has a second resistance so as to dissipate a second power within the reservoir, the second power being lower than the first power so that a total power dissipated in the tank is lower at the second time than at the first time.

6. The vehicular fluid tank according to claim 5 wherein said reservoir is placed substantially at a bottom of said vehicular fluid tank.

7. A method comprising:

using a circuit in a vehicular fluid tank, said tank comprising a reservoir mounted inside to hold a quantity of fluid within said tank, said circuit including

a first resistive element to electrically heat a first part of said tank, said first resistive element positioned outside said reservoir,

a second element to electrically heat a second part of said tank, said second element positioned inside said reservoir, said second element having a positive temperature coefficient, and

a third resistive element to electrically heat said second part of said tank, said third element positioned inside said reservoir,

wherein said second element and said first resistive element are connected in parallel, and said third resistive element is connected in series with said second element and said first resistive element,

wherein at a first time corresponding to a start of the heating, the second element has a first resistance so as to dissipate a first power, and

wherein at a later second time the second element has a second resistance so as to dissipate a second power, the second power being lower than the first power so that a total power dissipated in the tank is lower at the second time than at the first time.

8. The method of claim 7 , further comprising:

holding a urea solution in the vehicular fluid tank.

9. A reservoir to hold a quantity of fluid within a tank, said reservoir comprising:

a flexible heating element which includes a resistive wire forming a spiraling path or several concentric circles;

a first resistive element to electrically heat a first part of a tank, a first length of said resistive wire outside the reservoir forming said first element;

a second element to electrically heat a second part of said tank, said second element having a positive temperature coefficient; and

a third resistive element to electrically heat said second part of said tank, a second length of said resistive wire inside the reservoir forming said third resistive element,

said second element and said first resistive element forming a parallel circuit, and said third resistive clement being connected in series with said parallel circuit,

wherein said reservoir is mounted inside said tank, and

wherein at a first time corresponding to a start of the heating, the second element has a first resistance so as to dissipate a first power within the reservoir and wherein at a later second time the second element has a second resistance so as to dissipate a second power within the reservoir, the second power being lower than the first power so that the power dissipated in the tank is lower at the second time than at the first time.