Insulator and spark plug

Patent metadata

Field	Value
Publication number	US-12322930-B2
Application number	US-202218575062-A
Country	US
Kind code	B2
Filing date	Jul 21, 2022
Priority date	Jul 27, 2021
Publication date	Jun 3, 2025
Grant date	Jun 3, 2025

Abstract

A spark plug (1) includes a tubular insulator (50). The insulator contains alumina as a primary component, and further contains a secondary component. The secondary component contains a silicon (Si) component, a magnesium (Mg) component, a barium (Ba) component, a calcium (Ca) component, and a rare earth component. The amounts (mass %) of these components as reduced to oxide and relative to the total mass of the secondary component satisfy specific conditions.

First claim

The invention claimed is:

1. A tubular insulator for a spark plug, wherein
the insulator contains alumina as a primary component, and further contains a secondary component;
the secondary component contains a silicon (Si) component, a magnesium (Mg) component, a barium (Ba) component, a calcium (Ca) component, and a rare earth component; and
the amounts (mass %) of these components as reduced to oxide and relative to the total mass of the secondary component satisfy the following relations (1) to (5):
15.5≤(the amount of the Si component)≤55.1;  (1)

0.6≤(the amount of the Mg component)≤7.4;  (2)

26.7≤(the amount of the Ba component)≤68.5;  (3)

1.1≤(the amount of the Ca component)≤32.4;  (4)

11.4≤(the amount of the rare earth component)≤46.5; and  (5)

wherein the amount (mass %) of the alumina relative to the total mass of the insulator falls within a range of 91.0 mass % to 97.0 mass %.

2. An insulator according to claim 1 , wherein the amounts (mass %) of the Ba component and the rare earth component as reduced to oxide and relative to the total mass of the secondary component further satisfy the following relations (a) and (b):
29.1≤(the amount of the Ba component)≤52.5; and  (a)

12.4≤(the amount of the rare earth component)≤41.5.  (b)

3. An insulator according to claim 2 , wherein the amounts (mass %) of the Ba component and the rare earth component as reduced to oxide and relative to the total mass of the secondary component further satisfy the following relations (A) and (B):
30.6≤(the amount of the Ba component)≤35.3; and  (A)

17.4≤(the amount of the rare earth component)≤29.7.  (B)

4. An insulator according to claim 1 , wherein the rare earth component is a lanthanum (La) component.

5. A spark plug comprising:
an insulator as recited in claim 1 ;
a tubular metallic shell which holds at least a portion of the insulator therein;
a center electrode which is disposed at a forward end of the insulator; and
a ground electrode which is attached to the metallic shell and provides a gap between the ground electrode and the center electrode.

Assignees

• Niterra Co Ltd

Inventors

• Yokoyama Yutaka
• Kon Toshiki
• Kato Ippei

Classifications

• H01T13/60

  of electrical properties · CPC title

• C04B2235/6567

  Treatment time · CPC title

• C04B2235/6565

  Cooling rate · CPC title

• C04B2235/6562

  Heating rate · CPC title

• C04B2235/3227

  Lanthanum oxide or oxide-forming salts thereof · CPC title